[OpenMP] libomp: Add new experimental barrier: two-level distributed barrier

[tlwilmar]

Summary

Two-level distributed barrier is a new experimental barrier designed
for Intel hardware that has better performance in some cases than the
default hyper barrier.

This barrier is designed to handle fine granularity parallelism where
barriers are used frequently with little compute and memory access
between barriers. There is no need to use it for codes with few
barriers and large granularity compute, or memory intensive
applications, as little difference will be seen between this barrier
and the default hyper barrier. This barrier is designed to work
optimally with a fixed number of threads, and has a significant setup
time, so should NOT be used in situations where the number of threads
in a team is varied frequently.

The two-level distributed barrier is off by default -- hyper barrier
is used by default. To use this barrier, you must set all barrier
patterns to use this type, because it will not work with other barrier
patterns. Thus, to turn it on, the following settings are required:

KMP_FORKJOIN_BARRIER_PATTERN=dist,dist
KMP_PLAIN_BARRIER_PATTERN=dist,dist
KMP_REDUCTION_BARRIER_PATTERN=dist,dist

Branching factors (set with KMP_FORKJOIN_BARRIER, KMP_PLAIN_BARRIER,
and KMP_REDUCTION_BARRIER) are ignored by the two-level distributed
barrier.

[jlpeyton]

Can you add the lit run lines to test this new barrier in test/barrier/omp_barrier.c?

[tlwilmar]

Added test lines.

[jlpeyton]

Thanks! LGTM

[kkwli0]

Building on Power running RHEL has the following errors.

/llvm-project/openmp/runtime/src/kmp_barrier.cpp:371:3: error: use of undeclared identifier 'KMP_MFENCE'
  KMP_MFENCE();
  ^

/llvm-project/openmp/runtime/src/kmp_barrier.h:82:51: error: use of undeclared identifier '_mm_malloc'
    distributedBarrier *d = (distributedBarrier *)_mm_malloc(
                                                  ^

[jlpeyton]

In D103121#2828326, @kkwli0 wrote:

Building on Power running RHEL has the following errors.

/llvm-project/openmp/runtime/src/kmp_barrier.cpp:371:3: error: use of undeclared identifier 'KMP_MFENCE'
  KMP_MFENCE();
  ^

/llvm-project/openmp/runtime/src/kmp_barrier.h:82:51: error: use of undeclared identifier '_mm_malloc'
    distributedBarrier *d = (distributedBarrier *)_mm_malloc(
                                                  ^

Kelvin, I've created https://reviews.llvm.org/D104788 to fix this, can you check this patch and see if it fixes your problem.

[tlwilmar]

This update contains the original patch plus https://reviews.llvm.org/D104638, https://reviews.llvm.org/D104788, and a few more additions to fix the warnings mentioned in D104788.

[jdoerfert]

I think the original approval is still good, assuming this doesn't break other targets. Maybe have someone test it for you.

[tlwilmar]

kmp_barrier.h was missing; added back.

[kkwli0]

Is the diff from HEAD? I try to build it but the patch cannot be applied to the trunk.

[tlwilmar]

Kelvin, please try again with this new patch. As of this moment, at least, it applies on top of main branch.

[kkwli0]

Thanks Terry. Unfortunately, I got the following errors.

CMakeFiles/omp.dir/kmp_runtime.cpp.o: In function `~kmp_flag_64':
llvm-project/openmp/runtime/src/kmp.h:266: undefined reference to `operator delete(void*)'
CMakeFiles/omp.dir/kmp_runtime.cpp.o: In function `~kmp_flag_native':
llvm-project/openmp/runtime/src/kmp_wait_release.h:157: undefined reference to `operator delete(void*)'
CMakeFiles/omp.dir/kmp_barrier.cpp.o: In function `~kmp_flag_oncore':
llvm-project/openmp/runtime/src/kmp_wait_release.h:955: undefined reference to `operator delete(void*)'
CMakeFiles/omp.dir/kmp_barrier.cpp.o: In function `~kmp_flag_native':
llvm-project/openmp/runtime/src/kmp_wait_release.h:157: undefined reference to `operator delete(void*)'
CMakeFiles/omp.dir/kmp_barrier.cpp.o: In function `~kmp_flag_64':
/llvm-project/openmp/runtime/src/kmp_wait_release.h:855: undefined reference to `operator delete(void*)'
CMakeFiles/omp.dir/kmp_barrier.cpp.o:llvm-project/openmp/runtime/src/kmp_wait_release.h:157: more undefined references to `operator delete(void*)' follow

[tlwilmar]

Patch notes from Jonathan Peyton: The -Wl,-z,defs flag sent in from LLVM cause undefined references which cause link-time errors in object files due to the new empty virtual destructors. We eliminate this flag for the host OpenMP runtime which eliminates the undefined reference errors. This prevents the host runtime from requiring linking to the standard C++ runtime library.

[kkwli0]

@tlwilmar Is kmp_barrier.h accidentally removed in the latest update?

[JonChesterfield]

The -Wl,-z,defs flag sent in from LLVM cause undefined references which cause link-time errors in object files

This flag does not cause or create undefined references. It warns when there are some undefined references. Better to fix the missing symbols than to hope the application never tries to call them.

[tlwilmar]

Johnny added overloaded operator new() and operator delete() functions to the two kmp_flag classes that have virtual destructors. He took out the removal of the -Wl,-z,defs flag from the previous patch as well.
He applied it to LLVM and built all of LLVM using clang-12 (with no warnings now and no undefined references), then ran check-openmp and everything was OK.
Kelvin, please wait for the x86 build bot to give a passing result, before attempting to test. Thanks!

[tlwilmar]

@kkwli0 Other than some clang-format and clang-tidy issues (ignorable), builds look okay, so I think this is ready to try out.

[kkwli0]

@tlwilmar It builds successfully on Power9 running RHEL 8.2. Thanks.

openmp/runtime/cmake/config-ix.cmake

 # Check for Unix shared memory
 check_symbol_exists(shm_open "sys/mman.h" LIBOMP_HAVE_SHM_OPEN_NO_LRT)
 if (NOT LIBOMP_HAVE_SHM_OPEN_NO_LRT)
   set(CMAKE_REQUIRED_LIBRARIES -lrt)
   check_symbol_exists(shm_open "sys/mman.h" LIBOMP_HAVE_SHM_OPEN_WITH_LRT)
   set(CMAKE_REQUIRED_LIBRARIES)
 endif()
 
+# Check for aligned memory allocator function
+check_include_file(xmmintrin.h LIBOMP_HAVE_XMMINTRIN_H)
+set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
+if (LIBOMP_HAVE_XMMINTRIN_H)
+  set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -DLIBOMP_HAVE_XMMINTRIN_H")
+endif()
+set(source_code "// check for _mm_malloc
+    #ifdef LIBOMP_HAVE_XMMINTRIN_H
+    #include <xmmintrin.h>
+    #endif
+    int main() { void *ptr = _mm_malloc(sizeof(int) * 1000, 64); _mm_free(ptr); return 0; }")
+check_cxx_source_compiles("${source_code}" LIBOMP_HAVE__MM_MALLOC)
+set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
+check_symbol_exists(aligned_alloc "stdlib.h" LIBOMP_HAVE_ALIGNED_ALLOC)
+check_symbol_exists(posix_memalign "stdlib.h" LIBOMP_HAVE_POSIX_MEMALIGN)
+check_symbol_exists(_aligned_malloc "malloc.h" LIBOMP_HAVE__ALIGNED_MALLOC)
+
 # Check linker flags
 if(WIN32)
   libomp_check_linker_flag(/SAFESEH LIBOMP_HAVE_SAFESEH_FLAG)
 elseif(NOT APPLE)
   libomp_check_linker_flag(-Wl,-x LIBOMP_HAVE_X_FLAG)
   libomp_check_linker_flag(-Wl,--warn-shared-textrel LIBOMP_HAVE_WARN_SHARED_TEXTREL_FLAG)
   libomp_check_linker_flag(-Wl,--as-needed LIBOMP_HAVE_AS_NEEDED_FLAG)
   libomp_check_linker_flag("-Wl,--version-script=${LIBOMP_SRC_DIR}/exports_so.txt" LIBOMP_HAVE_VERSION_SCRIPT_FLAG)

openmp/runtime/src/i18n/en_US.txt

 FatalSysError                "Fatal system error detected."
 OutOfHeapMemory              "Out of heap memory."
 OBSOLETE                     "Clearing __KMP_REGISTERED_LIB env var failed."
 OBSOLETE                     "Registering library with env var failed."
 Using_int_Value              "%1$s value \"%2$d\" will be used."
 Using_uint_Value             "%1$s value \"%2$u\" will be used."
 Using_uint64_Value           "%1$s value \"%2$s\" will be used."
 Using_str_Value              "%1$s value \"%2$s\" will be used."
+BarrierPatternOverride       "Mixing other barrier patterns with dist is prohibited. Using dist for all barrier patterns."
 MaxValueUsing                "%1$s maximum value \"%2$d\" will be used."
 MinValueUsing                "%1$s minimum value \"%2$d\" will be used."
 MemoryAllocFailed            "Memory allocation failed."
 FileNameTooLong              "File name too long."
 OBSOLETE                     "Lock table overflow."
 ManyThreadsForTPDirective    "Too many threads to use threadprivate directive."
 AffinityInvalidMask          "%1$s: invalid mask."
 WrongDefinition              "Wrong definition."

openmp/runtime/src/kmp.h

 
 #if KMP_ARCH_X86 || KMP_ARCH_X86_64
 #include <xmmintrin.h>
 #endif
 
 #include "kmp_debug.h"
 #include "kmp_lock.h"
 #include "kmp_version.h"
+#include "kmp_barrier.h"
 #if USE_DEBUGGER
 #include "kmp_debugger.h"
 #endif
 #include "kmp_i18n.h"
 
 #define KMP_HANDLE_SIGNALS (KMP_OS_UNIX || KMP_OS_WINDOWS)
 
 #include "kmp_wrapper_malloc.h"

 typedef struct kmp_taskdata kmp_taskdata_t;
 typedef union kmp_task_team kmp_task_team_t;
 typedef union kmp_team kmp_team_p;
 typedef union kmp_info kmp_info_p;
 typedef union kmp_root kmp_root_p;
 
 template <bool C = false, bool S = true> class kmp_flag_32;
 template <bool C = false, bool S = true> class kmp_flag_64;
+template <bool C = false, bool S = true> class kmp_atomic_flag_64;
 class kmp_flag_oncore;
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 /* ------------------------------------------------------------------------ */
 
#define KMP_BARRIER_SWITCH_TO_OWN_FLAG                                         \
   3 // Special state; tells worker to shift from parent to own b_go
 #define KMP_BARRIER_SWITCHING                                                  \
   4 // Special state; worker resets appropriate flag on wake-up
 
 #define KMP_NOT_SAFE_TO_REAP                                                   \
   0 // Thread th_reap_state: not safe to reap (tasking)
 #define KMP_SAFE_TO_REAP 1 // Thread th_reap_state: safe to reap (not tasking)
 
+// The flag_type describes the storage used for the flag.
+enum flag_type {
+  flag32, /**< atomic 32 bit flags */
+  flag64, /**< 64 bit flags */
+  atomic_flag64, /**< atomic 64 bit flags */
+  flag_oncore, /**< special 64-bit flag for on-core barrier (hierarchical) */
+  flag_unset
+};
+
 enum barrier_type {
   bs_plain_barrier = 0, /* 0, All non-fork/join barriers (except reduction
                            barriers if enabled) */
   bs_forkjoin_barrier, /* 1, All fork/join (parallel region) barriers */
 #if KMP_FAST_REDUCTION_BARRIER
   bs_reduction_barrier, /* 2, All barriers that are used in reduction */
 #endif // KMP_FAST_REDUCTION_BARRIER
   bs_last_barrier /* Just a placeholder to mark the end */
 };
 
 // to work with reduction barriers just like with plain barriers
 #if !KMP_FAST_REDUCTION_BARRIER
 #define bs_reduction_barrier bs_plain_barrier
 #endif // KMP_FAST_REDUCTION_BARRIER
 
 typedef enum kmp_bar_pat { /* Barrier communication patterns */
                            bp_linear_bar =
                                0, /* Single level (degenerate) tree */
                            bp_tree_bar =
                                1, /* Balanced tree with branching factor 2^n */
                            bp_hyper_bar = 2, /* Hypercube-embedded tree with min
                                                 branching factor 2^n */
                            bp_hierarchical_bar = 3, /* Machine hierarchy tree */
+                           bp_dist_bar = 4, /* Distributed barrier */
                            bp_last_bar /* Placeholder to mark the end */
 } kmp_bar_pat_e;
 
 #define KMP_BARRIER_ICV_PUSH 1
 
 /* Record for holding the values of the internal controls stack records */
 typedef struct kmp_internal_control {
   int serial_nesting_level; /* corresponds to the value of the
#endif
 
   /* The following are also read by the primary thread during reinit */
   struct common_table *th_pri_common;
 
   volatile kmp_uint32 th_spin_here; /* thread-local location for spinning */
   /* while awaiting queuing lock acquire */
 
   volatile void *th_sleep_loc; // this points at a kmp_flag<T>
+  flag_type th_sleep_loc_type; // enum type of flag stored in th_sleep_loc
 
   ident_t *th_ident;
   unsigned th_x; // Random number generator data
   unsigned th_a; // Random number generator data
 
   /* Tasking-related data for the thread */
   kmp_task_team_t *th_task_team; // Task team struct
   kmp_taskdata_t *th_current_task; // Innermost Task being executed
   kmp_uint8 th_task_state; // alternating 0/1 for task team identification
   kmp_uint8 *th_task_state_memo_stack; // Stack holding memos of th_task_state
   // at nested levels
   kmp_uint32 th_task_state_top; // Top element of th_task_state_memo_stack
   kmp_uint32 th_task_state_stack_sz; // Size of th_task_state_memo_stack
   kmp_uint32 th_reap_state; // Non-zero indicates thread is not
   // tasking, thus safe to reap
 
   /* More stuff for keeping track of active/sleeping threads (this part is
      written by the worker thread) */
   kmp_uint8 th_active_in_pool; // included in count of #active threads in pool
   int th_active; // ! sleeping; 32 bits for TCR/TCW
+  std::atomic<kmp_uint32> th_used_in_team; // Flag indicating use in team
+  // 0 = not used in team; 1 = used in team;
+  // 2 = transitioning to not used in team; 3 = transitioning to used in team
   struct cons_header *th_cons; // used for consistency check
 #if KMP_USE_HIER_SCHED
   // used for hierarchical scheduling
   kmp_hier_private_bdata_t *th_hier_bar_data;
 #endif
 
   /* Add the syncronizing data which is cache aligned and padded. */
   KMP_ALIGN_CACHE kmp_balign_t th_bar[bs_last_barrier];
#endif
   int t_master_active; // save on fork, restore on join
   void *t_copypriv_data; // team specific pointer to copyprivate data array
 #if KMP_OS_WINDOWS
   std::atomic<kmp_uint32> t_copyin_counter;
 #endif
 #if USE_ITT_BUILD
   void *t_stack_id; // team specific stack stitching id (for ittnotify)
 #endif /* USE_ITT_BUILD */
+  distributedBarrier *b; // Distributed barrier data associated with team
 } kmp_base_team_t;
 
 union KMP_ALIGN_CACHE kmp_team {
   kmp_base_team_t t;
   double t_align; /* use worst case alignment */
   char t_pad[KMP_PAD(kmp_base_team_t, CACHE_LINE)];
 };
 

 #ifdef __cplusplus
 }
 #endif
 
 template <bool C, bool S>
 extern void __kmp_suspend_32(int th_gtid, kmp_flag_32<C, S> *flag);
 template <bool C, bool S>
 extern void __kmp_suspend_64(int th_gtid, kmp_flag_64<C, S> *flag);
+template <bool C, bool S>
+extern void __kmp_atomic_suspend_64(int th_gtid,
+                                    kmp_atomic_flag_64<C, S> *flag);
 extern void __kmp_suspend_oncore(int th_gtid, kmp_flag_oncore *flag);
 #if KMP_HAVE_MWAIT || KMP_HAVE_UMWAIT
 template <bool C, bool S>
 extern void __kmp_mwait_32(int th_gtid, kmp_flag_32<C, S> *flag);
 template <bool C, bool S>
 extern void __kmp_mwait_64(int th_gtid, kmp_flag_64<C, S> *flag);
+template <bool C, bool S>
+extern void __kmp_atomic_mwait_64(int th_gtid, kmp_atomic_flag_64<C, S> *flag);
 extern void __kmp_mwait_oncore(int th_gtid, kmp_flag_oncore *flag);
 #endif
 template <bool C, bool S>
 extern void __kmp_resume_32(int target_gtid, kmp_flag_32<C, S> *flag);
 template <bool C, bool S>
 extern void __kmp_resume_64(int target_gtid, kmp_flag_64<C, S> *flag);
+template <bool C, bool S>
+extern void __kmp_atomic_resume_64(int target_gtid,
+                                   kmp_atomic_flag_64<C, S> *flag);
 extern void __kmp_resume_oncore(int target_gtid, kmp_flag_oncore *flag);
 
 template <bool C, bool S>
 int __kmp_execute_tasks_32(kmp_info_t *thread, kmp_int32 gtid,
                            kmp_flag_32<C, S> *flag, int final_spin,
                            int *thread_finished,
 #if USE_ITT_BUILD
                            void *itt_sync_obj,
 #endif /* USE_ITT_BUILD */
                            kmp_int32 is_constrained);
 template <bool C, bool S>
 int __kmp_execute_tasks_64(kmp_info_t *thread, kmp_int32 gtid,
                            kmp_flag_64<C, S> *flag, int final_spin,
                            int *thread_finished,
 #if USE_ITT_BUILD
                            void *itt_sync_obj,
 #endif /* USE_ITT_BUILD */
                            kmp_int32 is_constrained);
+template <bool C, bool S>
+int __kmp_atomic_execute_tasks_64(kmp_info_t *thread, kmp_int32 gtid,
+                                  kmp_atomic_flag_64<C, S> *flag,
+                                  int final_spin, int *thread_finished,
+#if USE_ITT_BUILD
+                                  void *itt_sync_obj,
+#endif /* USE_ITT_BUILD */
+                                  kmp_int32 is_constrained);
 int __kmp_execute_tasks_oncore(kmp_info_t *thread, kmp_int32 gtid,
                                kmp_flag_oncore *flag, int final_spin,
                                int *thread_finished,
 #if USE_ITT_BUILD
                                void *itt_sync_obj,
 #endif /* USE_ITT_BUILD */
                                kmp_int32 is_constrained);
 

openmp/runtime/src/kmp_atomic.cpp

#define OP_CRITICAL(OP, LCK_ID)                                                \
   __kmp_acquire_atomic_lock(&ATOMIC_LOCK##LCK_ID, gtid);                       \
                                                                                \
   (*lhs) OP(rhs);                                                              \
                                                                                \
   __kmp_release_atomic_lock(&ATOMIC_LOCK##LCK_ID, gtid);
 
 #define OP_UPDATE_CRITICAL(TYPE, OP, LCK_ID)                                   \
   __kmp_acquire_atomic_lock(&ATOMIC_LOCK##LCK_ID, gtid);                       \
-  (*lhs) = (TYPE)((*lhs)OP((TYPE)rhs));                                        \
+  (*lhs) = (TYPE)((*lhs)OP rhs);                                               \
   __kmp_release_atomic_lock(&ATOMIC_LOCK##LCK_ID, gtid);
 
 // ------------------------------------------------------------------------
 // For GNU compatibility, we may need to use a critical section,
 // even though it is not required by the ISA.
 //
 // On IA-32 architecture, all atomic operations except for fixed 4 byte add,
 // sub, and bitwise logical ops, and 1 & 2 byte logical ops use a common

 // Operation on *lhs, rhs using "compare_and_store" routine
 //     TYPE    - operands' type
 //     BITS    - size in bits, used to distinguish low level calls
 //     OP      - operator
 #define OP_CMPXCHG(TYPE, BITS, OP)                                             \
   {                                                                            \
     TYPE old_value, new_value;                                                 \
     old_value = *(TYPE volatile *)lhs;                                         \
-    new_value = (TYPE)(old_value OP((TYPE)rhs));                               \
+    new_value = (TYPE)(old_value OP rhs);                                      \
     while (!KMP_COMPARE_AND_STORE_ACQ##BITS(                                   \
         (kmp_int##BITS *)lhs, *VOLATILE_CAST(kmp_int##BITS *) & old_value,     \
         *VOLATILE_CAST(kmp_int##BITS *) & new_value)) {                        \
       KMP_DO_PAUSE;                                                            \
                                                                                \
       old_value = *(TYPE volatile *)lhs;                                       \
-      new_value = (TYPE)(old_value OP((TYPE)rhs));                             \
+      new_value = (TYPE)(old_value OP rhs);                                    \
     }                                                                          \
   }
 
 #if USE_CMPXCHG_FIX
 // 2007-06-25:
 // workaround for C78287 (complex(kind=4) data type). lin_32, lin_32e, win_32
 // and win_32e are affected (I verified the asm). Compiler ignores the volatile
 // qualifier of the temp_val in the OP_CMPXCHG macro. This is a problem of the

openmp/runtime/src/kmp_barrier.h

+/*
+ * kmp_barrier.h
+ */
+
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef KMP_BARRIER_H
+#define KMP_BARRIER_H
+
+#include "kmp.h"
+#include "kmp_i18n.h"
+
+#if KMP_HAVE_XMMINTRIN_H && KMP_HAVE__MM_MALLOC
+#include <xmmintrin.h>
+#define KMP_ALIGNED_ALLOCATE(size, alignment) _mm_malloc(size, alignment)
+#define KMP_ALIGNED_FREE(ptr) _mm_free(ptr)
+#elif KMP_HAVE_ALIGNED_ALLOC
+#define KMP_ALIGNED_ALLOCATE(size, alignment) aligned_alloc(alignment, size)
+#define KMP_ALIGNED_FREE(ptr) free(ptr)
+#elif KMP_HAVE_POSIX_MEMALIGN
+static inline void *KMP_ALIGNED_ALLOCATE(size_t size, size_t alignment) {
+  void *ptr;
+  int n = posix_memalign(&ptr, alignment, size);
+  if (n != 0) {
+    if (ptr)
+      free(ptr);
+    return nullptr;
+  }
+  return ptr;
+}
+#define KMP_ALIGNED_FREE(ptr) free(ptr)
+#elif KMP_HAVE__ALIGNED_MALLOC
+#include <malloc.h>
+#define KMP_ALIGNED_ALLOCATE(size, alignment) _aligned_malloc(size, alignment)
+#define KMP_ALIGNED_FREE(ptr) _aligned_free(ptr)
+#else
+#define KMP_ALIGNED_ALLOCATE(size, alignment) KMP_INTERNAL_MALLOC(size)
+#define KMP_ALIGNED_FREE(ptr) KMP_INTERNAL_FREE(ptr)
+#endif
+
+// Use four cache lines: MLC tends to prefetch the next or previous cache line
+// creating a possible fake conflict between cores, so this is the only way to
+// guarantee that no such prefetch can happen.
+#ifndef KMP_FOURLINE_ALIGN_CACHE
+#define KMP_FOURLINE_ALIGN_CACHE KMP_ALIGN(4 * CACHE_LINE)
+#endif
+
+#define KMP_OPTIMIZE_FOR_REDUCTIONS 0
+
+class distributedBarrier {
+  struct flags_s {
+    kmp_uint32 volatile KMP_FOURLINE_ALIGN_CACHE stillNeed;
+  };
+
+  struct go_s {
+    std::atomic<kmp_uint64> KMP_FOURLINE_ALIGN_CACHE go;
+  };
+
+  struct iter_s {
+    kmp_uint64 volatile KMP_FOURLINE_ALIGN_CACHE iter;
+  };
+
+  struct sleep_s {
+    std::atomic<bool> KMP_FOURLINE_ALIGN_CACHE sleep;
+  };
+
+  void init(size_t nthr);
+  void resize(size_t nthr);
+  void computeGo(size_t n);
+  void computeVarsForN(size_t n);
+
+public:
+  enum {
+    MAX_ITERS = 3,
+    MAX_GOS = 8,
+    IDEAL_GOS = 4,
+    IDEAL_CONTENTION = 16,
+  };
+
+  flags_s *flags[MAX_ITERS];
+  go_s *go;
+  iter_s *iter;
+  sleep_s *sleep;
+
+  size_t KMP_ALIGN_CACHE num_threads; // number of threads in barrier
+  size_t KMP_ALIGN_CACHE max_threads; // size of arrays in data structure
+  // number of go signals each requiring one write per iteration
+  size_t KMP_ALIGN_CACHE num_gos;
+  // number of groups of gos
+  size_t KMP_ALIGN_CACHE num_groups;
+  // threads per go signal
+  size_t KMP_ALIGN_CACHE threads_per_go;
+  bool KMP_ALIGN_CACHE fix_threads_per_go;
+  // threads per group
+  size_t KMP_ALIGN_CACHE threads_per_group;
+  // number of go signals in a group
+  size_t KMP_ALIGN_CACHE gos_per_group;
+  void *team_icvs;
+
+  distributedBarrier() = delete;
+  ~distributedBarrier() = delete;
+
+  // Used instead of constructor to create aligned data
+  static distributedBarrier *allocate(int nThreads) {
+    distributedBarrier *d = (distributedBarrier *)KMP_ALIGNED_ALLOCATE(
+        sizeof(distributedBarrier), 4 * CACHE_LINE);
+    if (!d) {
+      KMP_FATAL(MemoryAllocFailed);
+    }
+    d->num_threads = 0;
+    d->max_threads = 0;
+    for (int i = 0; i < MAX_ITERS; ++i)
+      d->flags[i] = NULL;
+    d->go = NULL;
+    d->iter = NULL;
+    d->sleep = NULL;
+    d->team_icvs = NULL;
+    d->fix_threads_per_go = false;
+    // calculate gos and groups ONCE on base size
+    d->computeGo(nThreads);
+    d->init(nThreads);
+    return d;
+  }
+
+  static void deallocate(distributedBarrier *db) { KMP_ALIGNED_FREE(db); }
+
+  void update_num_threads(size_t nthr) { init(nthr); }
+
+  bool need_resize(size_t new_nthr) { return (new_nthr > max_threads); }
+  size_t get_num_threads() { return num_threads; }
+  kmp_uint64 go_release();
+  void go_reset();
+};
+
+#endif // KMP_BARRIER_H

openmp/runtime/src/kmp_barrier.cpp

 /*
  * kmp_barrier.cpp
  */
 
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-#include "kmp.h"
 #include "kmp_wait_release.h"
+#include "kmp_barrier.h"
 #include "kmp_itt.h"
 #include "kmp_os.h"
 #include "kmp_stats.h"
 #include "ompt-specific.h"
+// for distributed barrier
+#include "kmp_affinity.h"
 
 #if KMP_MIC
 #include <immintrin.h>
 #define USE_NGO_STORES 1
 #endif // KMP_MIC
 
 #if KMP_MIC && USE_NGO_STORES
 // ICV copying
 #define ngo_load(src) __m512d Vt = _mm512_load_pd((void *)(src))
 #define ngo_store_icvs(dst, src) _mm512_storenrngo_pd((void *)(dst), Vt)
 #define ngo_store_go(dst, src) _mm512_storenrngo_pd((void *)(dst), Vt)
 #define ngo_sync() __asm__ volatile("lock; addl $0,0(%%rsp)" ::: "memory")
 #else
 #define ngo_load(src) ((void)0)
 #define ngo_store_icvs(dst, src) copy_icvs((dst), (src))
 #define ngo_store_go(dst, src) KMP_MEMCPY((dst), (src), CACHE_LINE)
 #define ngo_sync() ((void)0)
 #endif /* KMP_MIC && USE_NGO_STORES */
 
 void __kmp_print_structure(void); // Forward declaration
 
 // ---------------------------- Barrier Algorithms ----------------------------
+// Distributed barrier
+
+// Compute how many threads to have polling each cache-line.
+// We want to limit the number of writes to IDEAL_GO_RESOLUTION.
+void distributedBarrier::computeVarsForN(size_t n) {
+  int nsockets = 1;
+  if (__kmp_topology) {
+    int socket_level = __kmp_topology->get_level(KMP_HW_SOCKET);
+    int core_level = __kmp_topology->get_level(KMP_HW_CORE);
+    int ncores_per_socket =
+        __kmp_topology->calculate_ratio(core_level, socket_level);
+    nsockets = __kmp_topology->get_count(socket_level);
+
+    if (nsockets <= 0)
+      nsockets = 1;
+    if (ncores_per_socket <= 0)
+      ncores_per_socket = 1;
+
+    threads_per_go = ncores_per_socket >> 1;
+    if (!fix_threads_per_go) {
+      // Minimize num_gos
+      if (threads_per_go > 4) {
+        if (KMP_OPTIMIZE_FOR_REDUCTIONS) {
+          threads_per_go = threads_per_go >> 1;
+        }
+        if (threads_per_go > 4 && nsockets == 1)
+          threads_per_go = threads_per_go >> 1;
+      }
+    }
+    if (threads_per_go == 0)
+      threads_per_go = 1;
+    fix_threads_per_go = true;
+    num_gos = n / threads_per_go;
+    if (n % threads_per_go)
+      num_gos++;
+    if (nsockets == 1 || num_gos == 1)
+      num_groups = 1;
+    else {
+      num_groups = num_gos / nsockets;
+      if (num_gos % nsockets)
+        num_groups++;
+    }
+    if (num_groups <= 0)
+      num_groups = 1;
+    gos_per_group = num_gos / num_groups;
+    if (num_gos % num_groups)
+      gos_per_group++;
+    threads_per_group = threads_per_go * gos_per_group;
+  } else {
+    num_gos = n / threads_per_go;
+    if (n % threads_per_go)
+      num_gos++;
+    if (num_gos == 1)
+      num_groups = 1;
+    else {
+      num_groups = num_gos / 2;
+      if (num_gos % 2)
+        num_groups++;
+    }
+    gos_per_group = num_gos / num_groups;
+    if (num_gos % num_groups)
+      gos_per_group++;
+    threads_per_group = threads_per_go * gos_per_group;
+  }
+}
+
+void distributedBarrier::computeGo(size_t n) {
+  // Minimize num_gos
+  for (num_gos = 1;; num_gos++)
+    if (IDEAL_CONTENTION * num_gos >= n)
+      break;
+  threads_per_go = n / num_gos;
+  if (n % num_gos)
+    threads_per_go++;
+  while (num_gos > MAX_GOS) {
+    threads_per_go++;
+    num_gos = n / threads_per_go;
+    if (n % threads_per_go)
+      num_gos++;
+  }
+  computeVarsForN(n);
+}
+
+// This function is to resize the barrier arrays when the new number of threads
+// exceeds max_threads, which is the current size of all the arrays
+void distributedBarrier::resize(size_t nthr) {
+  KMP_DEBUG_ASSERT(nthr > max_threads);
+
+  // expand to requested size * 2
+  max_threads = nthr * 2;
+
+  // allocate arrays to new max threads
+  for (int i = 0; i < MAX_ITERS; ++i) {
+    if (flags[i])
+      flags[i] = (flags_s *)KMP_INTERNAL_REALLOC(flags[i],
+                                                 max_threads * sizeof(flags_s));
+    else
+      flags[i] = (flags_s *)KMP_INTERNAL_MALLOC(max_threads * sizeof(flags_s));
+  }
+
+  if (go)
+    go = (go_s *)KMP_INTERNAL_REALLOC(go, max_threads * sizeof(go_s));
+  else
+    go = (go_s *)KMP_INTERNAL_MALLOC(max_threads * sizeof(go_s));
+
+  if (iter)
+    iter = (iter_s *)KMP_INTERNAL_REALLOC(iter, max_threads * sizeof(iter_s));
+  else
+    iter = (iter_s *)KMP_INTERNAL_MALLOC(max_threads * sizeof(iter_s));
+
+  if (sleep)
+    sleep =
+        (sleep_s *)KMP_INTERNAL_REALLOC(sleep, max_threads * sizeof(sleep_s));
+  else
+    sleep = (sleep_s *)KMP_INTERNAL_MALLOC(max_threads * sizeof(sleep_s));
+}
+
+// This function is to set all the go flags that threads might be waiting
+// on, and when blocktime is not infinite, it should be followed by a wake-up
+// call to each thread
+kmp_uint64 distributedBarrier::go_release() {
+  kmp_uint64 next_go = iter[0].iter + distributedBarrier::MAX_ITERS;
+  for (size_t j = 0; j < num_gos; j++) {
+    go[j].go.store(next_go);
+  }
+  return next_go;
+}
+
+void distributedBarrier::go_reset() {
+  for (size_t j = 0; j < max_threads; ++j) {
+    for (size_t i = 0; i < distributedBarrier::MAX_ITERS; ++i) {
+      flags[i][j].stillNeed = 1;
+    }
+    go[j].go.store(0);
+    iter[j].iter = 0;
+  }
+}
+
+// This function inits/re-inits the distributed barrier for a particular number
+// of threads. If a resize of arrays is needed, it calls the resize function.
+void distributedBarrier::init(size_t nthr) {
+  size_t old_max = max_threads;
+  if (nthr > max_threads) { // need more space in arrays
+    resize(nthr);
+  }
+
+  for (size_t i = 0; i < max_threads; i++) {
+    for (size_t j = 0; j < distributedBarrier::MAX_ITERS; j++) {
+      flags[j][i].stillNeed = 1;
+    }
+    go[i].go.store(0);
+    iter[i].iter = 0;
+    if (i >= old_max)
+      sleep[i].sleep = false;
+  }
+
+  // Recalculate num_gos, etc. based on new nthr
+  computeVarsForN(nthr);
+
+  num_threads = nthr;
+
+  if (team_icvs == NULL)
+    team_icvs = __kmp_allocate(sizeof(kmp_internal_control_t));
+}
+
+// This function is used only when KMP_BLOCKTIME is not infinite.
+// static
+void __kmp_dist_barrier_wakeup(enum barrier_type bt, kmp_team_t *team,
+                               size_t start, size_t stop, size_t inc,
+                               size_t tid) {
+  KMP_DEBUG_ASSERT(__kmp_dflt_blocktime != KMP_MAX_BLOCKTIME);
+  if (bt == bs_forkjoin_barrier && TCR_4(__kmp_global.g.g_done))
+    return;
+
+  kmp_info_t **other_threads = team->t.t_threads;
+  for (size_t thr = start; thr < stop; thr += inc) {
+    KMP_DEBUG_ASSERT(other_threads[thr]);
+    int gtid = other_threads[thr]->th.th_info.ds.ds_gtid;
+    // Wake up worker regardless of if it appears to be sleeping or not
+    __kmp_atomic_resume_64(gtid, (kmp_atomic_flag_64<> *)NULL);
+  }
+}
+
+static void __kmp_dist_barrier_gather(
+    enum barrier_type bt, kmp_info_t *this_thr, int gtid, int tid,
+    void (*reduce)(void *, void *) USE_ITT_BUILD_ARG(void *itt_sync_obj)) {
+  KMP_TIME_DEVELOPER_PARTITIONED_BLOCK(KMP_dist_gather);
+  kmp_team_t *team;
+  distributedBarrier *b;
+  kmp_info_t **other_threads;
+  kmp_uint64 my_current_iter, my_next_iter;
+  kmp_uint32 nproc;
+  bool group_leader;
+
+  team = this_thr->th.th_team;
+  nproc = this_thr->th.th_team_nproc;
+  other_threads = team->t.t_threads;
+  b = team->t.b;
+  my_current_iter = b->iter[tid].iter;
+  my_next_iter = (my_current_iter + 1) % distributedBarrier::MAX_ITERS;
+  group_leader = ((tid % b->threads_per_group) == 0);
+
+  KA_TRACE(20,
+           ("__kmp_dist_barrier_gather: T#%d(%d:%d) enter; barrier type %d\n",
+            gtid, team->t.t_id, tid, bt));
+
+#if USE_ITT_BUILD && USE_ITT_NOTIFY
+  // Barrier imbalance - save arrive time to the thread
+  if (__kmp_forkjoin_frames_mode == 3 || __kmp_forkjoin_frames_mode == 2) {
+    this_thr->th.th_bar_arrive_time = this_thr->th.th_bar_min_time =
+        __itt_get_timestamp();
+  }
+#endif
+
+  if (group_leader) {
+    // Start from the thread after the group leader
+    size_t group_start = tid + 1;
+    size_t group_end = tid + b->threads_per_group;
+    size_t threads_pending = 0;
+
+    if (group_end > nproc)
+      group_end = nproc;
+    do { // wait for threads in my group
+      threads_pending = 0;
+      // Check all the flags every time to avoid branch misspredict
+      for (size_t thr = group_start; thr < group_end; thr++) {
+        // Each thread uses a different cache line
+        threads_pending += b->flags[my_current_iter][thr].stillNeed;
+      }
+      // Execute tasks here
+      if (__kmp_tasking_mode != tskm_immediate_exec) {
+        kmp_task_team_t *task_team = this_thr->th.th_task_team;
+        if (task_team != NULL) {
+          if (TCR_SYNC_4(task_team->tt.tt_active)) {
+            if (KMP_TASKING_ENABLED(task_team)) {
+              int tasks_completed = FALSE;
+              __kmp_atomic_execute_tasks_64(
+                  this_thr, gtid, (kmp_atomic_flag_64<> *)NULL, FALSE,
+                  &tasks_completed USE_ITT_BUILD_ARG(itt_sync_obj), 0);
+            } else
+              this_thr->th.th_reap_state = KMP_SAFE_TO_REAP;
+          }
+        } else {
+          this_thr->th.th_reap_state = KMP_SAFE_TO_REAP;
+        } // if
+      }
+      if (TCR_4(__kmp_global.g.g_done)) {
+        if (__kmp_global.g.g_abort)
+          __kmp_abort_thread();
+        break;
+      } else if (__kmp_tasking_mode != tskm_immediate_exec &&
+                 this_thr->th.th_reap_state == KMP_SAFE_TO_REAP) {
+        this_thr->th.th_reap_state = KMP_NOT_SAFE_TO_REAP;
+      }
+    } while (threads_pending > 0);
+
+    if (reduce) { // Perform reduction if needed
+      OMPT_REDUCTION_DECL(this_thr, gtid);
+      OMPT_REDUCTION_BEGIN;
+      // Group leader reduces all threads in group
+      for (size_t thr = group_start; thr < group_end; thr++) {
+        (*reduce)(this_thr->th.th_local.reduce_data,
+                  other_threads[thr]->th.th_local.reduce_data);
+      }
+      OMPT_REDUCTION_END;
+    }
+
+    // Set flag for next iteration
+    b->flags[my_next_iter][tid].stillNeed = 1;
+    // Each thread uses a different cache line; resets stillNeed to 0 to
+    // indicate it has reached the barrier
+    b->flags[my_current_iter][tid].stillNeed = 0;
+
+    do { // wait for all group leaders
+      threads_pending = 0;
+      for (size_t thr = 0; thr < nproc; thr += b->threads_per_group) {
+        threads_pending += b->flags[my_current_iter][thr].stillNeed;
+      }
+      // Execute tasks here
+      if (__kmp_tasking_mode != tskm_immediate_exec) {
+        kmp_task_team_t *task_team = this_thr->th.th_task_team;
+        if (task_team != NULL) {
+          if (TCR_SYNC_4(task_team->tt.tt_active)) {
+            if (KMP_TASKING_ENABLED(task_team)) {
+              int tasks_completed = FALSE;
+              __kmp_atomic_execute_tasks_64(
+                  this_thr, gtid, (kmp_atomic_flag_64<> *)NULL, FALSE,
+                  &tasks_completed USE_ITT_BUILD_ARG(itt_sync_obj), 0);
+            } else
+              this_thr->th.th_reap_state = KMP_SAFE_TO_REAP;
+          }
+        } else {
+          this_thr->th.th_reap_state = KMP_SAFE_TO_REAP;
+        } // if
+      }
+      if (TCR_4(__kmp_global.g.g_done)) {
+        if (__kmp_global.g.g_abort)
+          __kmp_abort_thread();
+        break;
+      } else if (__kmp_tasking_mode != tskm_immediate_exec &&
+                 this_thr->th.th_reap_state == KMP_SAFE_TO_REAP) {
+        this_thr->th.th_reap_state = KMP_NOT_SAFE_TO_REAP;
+      }
+    } while (threads_pending > 0);
+
+    if (reduce) { // Perform reduction if needed
+      if (KMP_MASTER_TID(tid)) { // Master reduces over group leaders
+        OMPT_REDUCTION_DECL(this_thr, gtid);
+        OMPT_REDUCTION_BEGIN;
+        for (size_t thr = b->threads_per_group; thr < nproc;
+             thr += b->threads_per_group) {
+          (*reduce)(this_thr->th.th_local.reduce_data,
+                    other_threads[thr]->th.th_local.reduce_data);
+        }
+        OMPT_REDUCTION_END;
+      }
+    }
+  } else {
+    // Set flag for next iteration
+    b->flags[my_next_iter][tid].stillNeed = 1;
+    // Each thread uses a different cache line; resets stillNeed to 0 to
+    // indicate it has reached the barrier
+    b->flags[my_current_iter][tid].stillNeed = 0;
+  }
+
+  KMP_MFENCE();
+
+  KA_TRACE(20,
+           ("__kmp_dist_barrier_gather: T#%d(%d:%d) exit for barrier type %d\n",
+            gtid, team->t.t_id, tid, bt));
+}
+
+static void __kmp_dist_barrier_release(
+    enum barrier_type bt, kmp_info_t *this_thr, int gtid, int tid,
+    int propagate_icvs USE_ITT_BUILD_ARG(void *itt_sync_obj)) {
+  KMP_TIME_DEVELOPER_PARTITIONED_BLOCK(KMP_dist_release);
+  kmp_team_t *team;
+  distributedBarrier *b;
+  kmp_bstate_t *thr_bar;
+  kmp_uint64 my_current_iter, next_go;
+  size_t my_go_index;
+  bool group_leader;
+
+  KA_TRACE(20, ("__kmp_dist_barrier_release: T#%d(%d) enter; barrier type %d\n",
+                gtid, tid, bt));
+
+  thr_bar = &this_thr->th.th_bar[bt].bb;
+
+  if (!KMP_MASTER_TID(tid)) {
+    // workers and non-master group leaders need to check their presence in team
+    do {
+      if (this_thr->th.th_used_in_team.load() != 1 &&
+          this_thr->th.th_used_in_team.load() != 3) {
+        // Thread is not in use in a team. Wait on location in tid's thread
+        // struct. The 0 value tells anyone looking that this thread is spinning
+        // or sleeping until this location becomes 3 again; 3 is the transition
+        // state to get to 1 which is waiting on go and being in the team
+        kmp_flag_32<false, false> my_flag(&(this_thr->th.th_used_in_team), 3);
+        if (KMP_COMPARE_AND_STORE_ACQ32(&(this_thr->th.th_used_in_team), 2,
+                                        0) ||
+            this_thr->th.th_used_in_team.load() == 0) {
+          my_flag.wait(this_thr, true USE_ITT_BUILD_ARG(itt_sync_obj));
+        }
+#if USE_ITT_BUILD && USE_ITT_NOTIFY
+        if ((__itt_sync_create_ptr && itt_sync_obj == NULL) || KMP_ITT_DEBUG) {
+          // In fork barrier where we could not get the object reliably
+          itt_sync_obj =
+              __kmp_itt_barrier_object(gtid, bs_forkjoin_barrier, 0, -1);
+          // Cancel wait on previous parallel region...
+          __kmp_itt_task_starting(itt_sync_obj);
+
+          if (bt == bs_forkjoin_barrier && TCR_4(__kmp_global.g.g_done))
+            return;
+
+          itt_sync_obj = __kmp_itt_barrier_object(gtid, bs_forkjoin_barrier);
+          if (itt_sync_obj != NULL)
+            // Call prepare as early as possible for "new" barrier
+            __kmp_itt_task_finished(itt_sync_obj);
+        } else
+#endif /* USE_ITT_BUILD && USE_ITT_NOTIFY */
+            if (bt == bs_forkjoin_barrier && TCR_4(__kmp_global.g.g_done))
+          return;
+      }
+      if (this_thr->th.th_used_in_team.load() != 1 &&
+          this_thr->th.th_used_in_team.load() != 3) // spurious wake-up?
+        continue;
+      if (bt == bs_forkjoin_barrier && TCR_4(__kmp_global.g.g_done))
+        return;
+
+      // At this point, the thread thinks it is in use in a team, or in
+      // transition to be used in a team, but it might have reached this barrier
+      // before it was marked unused by the team. Unused threads are awoken and
+      // shifted to wait on local thread struct elsewhere. It also might reach
+      // this point by being picked up for use by a different team. Either way,
+      // we need to update the tid.
+      tid = __kmp_tid_from_gtid(gtid);
+      team = this_thr->th.th_team;
+      KMP_DEBUG_ASSERT(tid >= 0);
+      KMP_DEBUG_ASSERT(team);
+      b = team->t.b;
+      my_current_iter = b->iter[tid].iter;
+      next_go = my_current_iter + distributedBarrier::MAX_ITERS;
+      my_go_index = tid / b->threads_per_go;
+      if (this_thr->th.th_used_in_team.load() == 3) {
+        KMP_COMPARE_AND_STORE_ACQ32(&(this_thr->th.th_used_in_team), 3, 1);
+      }
+      // Check if go flag is set
+      if (b->go[my_go_index].go.load() != next_go) {
+        // Wait on go flag on team
+        kmp_atomic_flag_64<false, true> my_flag(
+            &(b->go[my_go_index].go), next_go, &(b->sleep[tid].sleep));
+        my_flag.wait(this_thr, true USE_ITT_BUILD_ARG(itt_sync_obj));
+        KMP_DEBUG_ASSERT(my_current_iter == b->iter[tid].iter ||
+                         b->iter[tid].iter == 0);
+        KMP_DEBUG_ASSERT(b->sleep[tid].sleep == false);
+      }
+
+      if (bt == bs_forkjoin_barrier && TCR_4(__kmp_global.g.g_done))
+        return;
+      // At this point, the thread's go location was set. This means the primary
+      // thread is safely in the barrier, and so this thread's data is
+      // up-to-date, but we should check again that this thread is really in
+      // use in the team, as it could have been woken up for the purpose of
+      // changing team size, or reaping threads at shutdown.
+      if (this_thr->th.th_used_in_team.load() == 1)
+        break;
+    } while (1);
+
+    if (bt == bs_forkjoin_barrier && TCR_4(__kmp_global.g.g_done))
+      return;
+
+    group_leader = ((tid % b->threads_per_group) == 0);
+    if (group_leader) {
+      // Tell all the threads in my group they can go!
+      for (size_t go_idx = my_go_index + 1;
+           go_idx < my_go_index + b->gos_per_group; go_idx++) {
+        b->go[go_idx].go.store(next_go);
+      }
+      // Fence added so that workers can see changes to go. sfence inadequate.
+      KMP_MFENCE();
+    }
+
+#if KMP_BARRIER_ICV_PUSH
+    if (propagate_icvs) { // copy ICVs to final dest
+      __kmp_init_implicit_task(team->t.t_ident, team->t.t_threads[tid], team,
+                               tid, FALSE);
+      copy_icvs(&team->t.t_implicit_task_taskdata[tid].td_icvs,
+                (kmp_internal_control_t *)team->t.b->team_icvs);
+      copy_icvs(&thr_bar->th_fixed_icvs,
+                &team->t.t_implicit_task_taskdata[tid].td_icvs);
+    }
+#endif
+    if (__kmp_dflt_blocktime != KMP_MAX_BLOCKTIME && group_leader) {
+      // This thread is now awake and participating in the barrier;
+      // wake up the other threads in the group
+      size_t nproc = this_thr->th.th_team_nproc;
+      size_t group_end = tid + b->threads_per_group;
+      if (nproc < group_end)
+        group_end = nproc;
+      __kmp_dist_barrier_wakeup(bt, team, tid + 1, group_end, 1, tid);
+    }
+  } else { //  Primary thread
+    team = this_thr->th.th_team;
+    b = team->t.b;
+    my_current_iter = b->iter[tid].iter;
+    next_go = my_current_iter + distributedBarrier::MAX_ITERS;
+#if KMP_BARRIER_ICV_PUSH
+    if (propagate_icvs) {
+      // primary thread has ICVs in final destination; copy
+      copy_icvs(&thr_bar->th_fixed_icvs,
+                &team->t.t_implicit_task_taskdata[tid].td_icvs);
+    }
+#endif
+    // Tell all the group leaders they can go!
+    for (size_t go_idx = 0; go_idx < b->num_gos; go_idx += b->gos_per_group) {
+      b->go[go_idx].go.store(next_go);
+    }
+
+    if (__kmp_dflt_blocktime != KMP_MAX_BLOCKTIME) {
+      // Wake-up the group leaders
+      size_t nproc = this_thr->th.th_team_nproc;
+      __kmp_dist_barrier_wakeup(bt, team, tid + b->threads_per_group, nproc,
+                                b->threads_per_group, tid);
+    }
+
+    // Tell all the threads in my group they can go!
+    for (size_t go_idx = 1; go_idx < b->gos_per_group; go_idx++) {
+      b->go[go_idx].go.store(next_go);
+    }
+
+    // Fence added so that workers can see changes to go. sfence inadequate.
+    KMP_MFENCE();
+
+    if (__kmp_dflt_blocktime != KMP_MAX_BLOCKTIME) {
+      // Wake-up the other threads in my group
+      size_t nproc = this_thr->th.th_team_nproc;
+      size_t group_end = tid + b->threads_per_group;
+      if (nproc < group_end)
+        group_end = nproc;
+      __kmp_dist_barrier_wakeup(bt, team, tid + 1, group_end, 1, tid);
+    }
+  }
+  // Update to next iteration
+  KMP_ASSERT(my_current_iter == b->iter[tid].iter);
+  b->iter[tid].iter = (b->iter[tid].iter + 1) % distributedBarrier::MAX_ITERS;
+
+  KA_TRACE(
+      20, ("__kmp_dist_barrier_release: T#%d(%d:%d) exit for barrier type %d\n",
+           gtid, team->t.t_id, tid, bt));
+}
 
 // Linear Barrier
 template <bool cancellable = false>
 static bool __kmp_linear_barrier_gather_template(
     enum barrier_type bt, kmp_info_t *this_thr, int gtid, int tid,
     void (*reduce)(void *, void *) USE_ITT_BUILD_ARG(void *itt_sync_obj)) {
   KMP_TIME_DEVELOPER_PARTITIONED_BLOCK(KMP_linear_gather);
   kmp_team_t *team = this_thr->th.th_team;
if (KMP_MASTER_TID(tid) && __kmp_tasking_mode != tskm_immediate_exec)
       // use 0 to only setup the current team if nthreads > 1
       __kmp_task_team_setup(this_thr, team, 0);
 
     if (cancellable) {
       cancelled = __kmp_linear_barrier_gather_cancellable(
           bt, this_thr, gtid, tid, reduce USE_ITT_BUILD_ARG(itt_sync_obj));
     } else {
       switch (__kmp_barrier_gather_pattern[bt]) {
+      case bp_dist_bar: {
+        __kmp_dist_barrier_gather(bt, this_thr, gtid, tid,
+                                  reduce USE_ITT_BUILD_ARG(itt_sync_obj));
+        break;
+      }
       case bp_hyper_bar: {
         // don't set branch bits to 0; use linear
         KMP_ASSERT(__kmp_barrier_gather_branch_bits[bt]);
         __kmp_hyper_barrier_gather(bt, this_thr, gtid, tid,
                                    reduce USE_ITT_BUILD_ARG(itt_sync_obj));
         break;
       }
       case bp_hierarchical_bar: {

 #endif /* USE_ITT_BUILD */
     }
     if ((status == 1 || !is_split) && !cancelled) {
       if (cancellable) {
         cancelled = __kmp_linear_barrier_release_cancellable(
             bt, this_thr, gtid, tid, FALSE USE_ITT_BUILD_ARG(itt_sync_obj));
       } else {
         switch (__kmp_barrier_release_pattern[bt]) {
+        case bp_dist_bar: {
+          KMP_ASSERT(__kmp_barrier_release_branch_bits[bt]);
+          __kmp_dist_barrier_release(bt, this_thr, gtid, tid,
+                                     FALSE USE_ITT_BUILD_ARG(itt_sync_obj));
+          break;
+        }
         case bp_hyper_bar: {
           KMP_ASSERT(__kmp_barrier_release_branch_bits[bt]);
           __kmp_hyper_barrier_release(bt, this_thr, gtid, tid,
                                       FALSE USE_ITT_BUILD_ARG(itt_sync_obj));
           break;
         }
         case bp_hierarchical_bar: {
           __kmp_hierarchical_barrier_release(
void __kmp_end_split_barrier(enum barrier_type bt, int gtid) {
   KMP_DEBUG_ASSERT(bt < bs_last_barrier);
   int tid = __kmp_tid_from_gtid(gtid);
   kmp_info_t *this_thr = __kmp_threads[gtid];
   kmp_team_t *team = this_thr->th.th_team;
 
   if (!team->t.t_serialized) {
     if (KMP_MASTER_GTID(gtid)) {
       switch (__kmp_barrier_release_pattern[bt]) {
+      case bp_dist_bar: {
+        __kmp_dist_barrier_release(bt, this_thr, gtid, tid,
+                                   FALSE USE_ITT_BUILD_ARG(NULL));
+        break;
+      }
       case bp_hyper_bar: {
         KMP_ASSERT(__kmp_barrier_release_branch_bits[bt]);
         __kmp_hyper_barrier_release(bt, this_thr, gtid, tid,
                                     FALSE USE_ITT_BUILD_ARG(NULL));
         break;
       }
       case bp_hierarchical_bar: {
         __kmp_hierarchical_barrier_release(bt, this_thr, gtid, tid,
if (!KMP_MASTER_TID(ds_tid))
       this_thr->th.ompt_thread_info.task_data = *OMPT_CUR_TASK_DATA(this_thr);
 #endif
     this_thr->th.ompt_thread_info.state = ompt_state_wait_barrier_implicit;
   }
 #endif
 
   if (__kmp_tasking_mode == tskm_extra_barrier) {
     __kmp_tasking_barrier(team, this_thr, gtid);
-    KA_TRACE(10, ("__kmp_join_barrier: T#%d(%d:%d) past taking barrier\n", gtid,
-                  team_id, tid));
+    KA_TRACE(10, ("__kmp_join_barrier: T#%d(%d:%d) past tasking barrier\n",
+                  gtid, team_id, tid));
   }
 #ifdef KMP_DEBUG
   if (__kmp_tasking_mode != tskm_immediate_exec) {
     KA_TRACE(20, ("__kmp_join_barrier: T#%d, old team = %d, old task_team = "
                   "%p, th_task_team = %p\n",
                   __kmp_gtid_from_thread(this_thr), team_id,
                   team->t.t_task_team[this_thr->th.th_task_state],
                   this_thr->th.th_task_team));
+    if (this_thr->th.th_task_team)
       KMP_DEBUG_ASSERT(this_thr->th.th_task_team ==
                        team->t.t_task_team[this_thr->th.th_task_state]);
   }
 #endif /* KMP_DEBUG */
 
   /* Copy the blocktime info to the thread, where __kmp_wait_template() can
      access it when the team struct is not guaranteed to exist. Doing these
      loads causes a cache miss slows down EPCC parallel by 2x. As a workaround,
      we do not perform the copy if blocktime=infinite, since the values are not
      used by __kmp_wait_template() in that case. */
#endif
   }
 
 #if USE_ITT_BUILD
   if (__itt_sync_create_ptr || KMP_ITT_DEBUG)
     __kmp_itt_barrier_starting(gtid, itt_sync_obj);
 #endif /* USE_ITT_BUILD */
 
   switch (__kmp_barrier_gather_pattern[bs_forkjoin_barrier]) {
+  case bp_dist_bar: {
+    __kmp_dist_barrier_gather(bs_forkjoin_barrier, this_thr, gtid, tid,
+                              NULL USE_ITT_BUILD_ARG(itt_sync_obj));
+    break;
+  }
   case bp_hyper_bar: {
     KMP_ASSERT(__kmp_barrier_gather_branch_bits[bs_forkjoin_barrier]);
     __kmp_hyper_barrier_gather(bs_forkjoin_barrier, this_thr, gtid, tid,
                                NULL USE_ITT_BUILD_ARG(itt_sync_obj));
     break;
   }
   case bp_hierarchical_bar: {
     __kmp_hierarchical_barrier_gather(bs_forkjoin_barrier, this_thr, gtid, tid,
#if KMP_STATS_ENABLED
     // idle.
     for (int i = 0; i < team->t.t_nproc; ++i) {
       kmp_info_t *team_thread = team->t.t_threads[i];
       if (team_thread == this_thr)
         continue;
       team_thread->th.th_stats->setIdleFlag();
       if (__kmp_dflt_blocktime != KMP_MAX_BLOCKTIME &&
           team_thread->th.th_sleep_loc != NULL)
-        __kmp_null_resume_wrapper(__kmp_gtid_from_thread(team_thread),
-                                  team_thread->th.th_sleep_loc);
+        __kmp_null_resume_wrapper(team_thread);
     }
 #endif
 #if USE_ITT_BUILD
     if (__itt_sync_create_ptr || KMP_ITT_DEBUG)
       __kmp_itt_barrier_middle(gtid, itt_sync_obj);
 #endif /* USE_ITT_BUILD */
 
 #if USE_ITT_BUILD && USE_ITT_NOTIFY
#if KMP_USE_MONITOR
           team->t.t_implicit_task_taskdata[tid].td_icvs.bt_set;
 #else
       this_thr->th.th_team_bt_intervals = KMP_BLOCKTIME_INTERVAL(team, tid);
 #endif
     }
   } // primary thread
 
   switch (__kmp_barrier_release_pattern[bs_forkjoin_barrier]) {
+  case bp_dist_bar: {
+    __kmp_dist_barrier_release(bs_forkjoin_barrier, this_thr, gtid, tid,
+                               TRUE USE_ITT_BUILD_ARG(NULL));
+    break;
+  }
   case bp_hyper_bar: {
     KMP_ASSERT(__kmp_barrier_release_branch_bits[bs_forkjoin_barrier]);
     __kmp_hyper_barrier_release(bs_forkjoin_barrier, this_thr, gtid, tid,
                                 TRUE USE_ITT_BUILD_ARG(itt_sync_obj));
     break;
   }
   case bp_hierarchical_bar: {
     __kmp_hierarchical_barrier_release(bs_forkjoin_barrier, this_thr, gtid, tid,

openmp/runtime/src/kmp_config.h.cmake

 #cmakedefine01 LIBOMP_HAVE_INTRIN_H
 #define KMP_HAVE_INTRIN_H LIBOMP_HAVE_INTRIN_H
 #cmakedefine01 LIBOMP_HAVE_ATTRIBUTE_WAITPKG
 #define KMP_HAVE_ATTRIBUTE_WAITPKG LIBOMP_HAVE_ATTRIBUTE_WAITPKG
 #cmakedefine01 LIBOMP_HAVE_ATTRIBUTE_RTM
 #define KMP_HAVE_ATTRIBUTE_RTM LIBOMP_HAVE_ATTRIBUTE_RTM
 #cmakedefine01 LIBOMP_ARCH_AARCH64_A64FX
 #define KMP_ARCH_AARCH64_A64FX LIBOMP_ARCH_AARCH64_A64FX
+#cmakedefine01 LIBOMP_HAVE_XMMINTRIN_H
+#define KMP_HAVE_XMMINTRIN_H LIBOMP_HAVE_XMMINTRIN_H
+#cmakedefine01 LIBOMP_HAVE__MM_MALLOC
+#define KMP_HAVE__MM_MALLOC LIBOMP_HAVE__MM_MALLOC
+#cmakedefine01 LIBOMP_HAVE_ALIGNED_ALLOC
+#define KMP_HAVE_ALIGNED_ALLOC LIBOMP_HAVE_ALIGNED_ALLOC
+#cmakedefine01 LIBOMP_HAVE_POSIX_MEMALIGN
+#define KMP_HAVE_POSIX_MEMALIGN LIBOMP_HAVE_POSIX_MEMALIGN
+#cmakedefine01 LIBOMP_HAVE__ALIGNED_MALLOC
+#define KMP_HAVE__ALIGNED_MALLOC LIBOMP_HAVE__ALIGNED_MALLOC
 
 // Configured cache line based on architecture
 #if KMP_ARCH_PPC64
 # define CACHE_LINE 128
 #elif KMP_ARCH_AARCH64_A64FX
 # define CACHE_LINE 256
 #else
 # define CACHE_LINE 64

openmp/runtime/src/kmp_global.cpp

 #endif // KMP_FAST_REDUCTION_BARRIER
 };
 char const *__kmp_barrier_type_name[bs_last_barrier] = {"plain", "forkjoin"
 #if KMP_FAST_REDUCTION_BARRIER
                                                         ,
                                                         "reduction"
 #endif // KMP_FAST_REDUCTION_BARRIER
 };
-char const *__kmp_barrier_pattern_name[bp_last_bar] = {"linear", "tree",
-                                                       "hyper", "hierarchical"};
+char const *__kmp_barrier_pattern_name[bp_last_bar] = {
+    "linear", "tree", "hyper", "hierarchical", "dist"};
 
 int __kmp_allThreadsSpecified = 0;
 size_t __kmp_align_alloc = CACHE_LINE;
 
 int __kmp_generate_warnings = kmp_warnings_low;
 int __kmp_reserve_warn = 0;
 int __kmp_xproc = 0;
 int __kmp_avail_proc = 0;

openmp/runtime/src/kmp_os.h

 #define KMP_MB() __sync_synchronize()
 #endif
 #endif
 
 #ifndef KMP_MB
 #define KMP_MB() /* nothing to do */
 #endif
 
+#if KMP_ARCH_X86 || KMP_ARCH_X86_64
+#if KMP_COMPILER_ICC
+#define KMP_MFENCE_() _mm_mfence()
+#define KMP_SFENCE_() _mm_sfence()
+#elif KMP_COMPILER_MSVC
+#define KMP_MFENCE_() MemoryBarrier()
+#define KMP_SFENCE_() MemoryBarrier()
+#else
+#define KMP_MFENCE_() __sync_synchronize()
+#define KMP_SFENCE_() __sync_synchronize()
+#endif
+#define KMP_MFENCE()                                                           \
+  if (UNLIKELY(!__kmp_cpuinfo.initialized)) {                                  \
+    __kmp_query_cpuid(&__kmp_cpuinfo);                                         \
+  }                                                                            \
+  if (__kmp_cpuinfo.sse2) {                                                    \
+    KMP_MFENCE_();                                                             \
+  }
+#define KMP_SFENCE() KMP_SFENCE_()
+#else
+#define KMP_MFENCE() KMP_MB()
+#define KMP_SFENCE() KMP_MB()
+#endif
+
 #ifndef KMP_IMB
 #define KMP_IMB() /* nothing to do */
 #endif
 
 #ifndef KMP_ST_REL32
 #define KMP_ST_REL32(A, D) (*(A) = (D))
 #endif
 

openmp/runtime/src/kmp_runtime.cpp

 
 static int __kmp_expand_threads(int nNeed);
 #if KMP_OS_WINDOWS
 static int __kmp_unregister_root_other_thread(int gtid);
 #endif
 static void __kmp_reap_thread(kmp_info_t *thread, int is_root);
 kmp_info_t *__kmp_thread_pool_insert_pt = NULL;
 
+void __kmp_resize_dist_barrier(kmp_team_t *team, int old_nthreads,
+                               int new_nthreads);
+void __kmp_add_threads_to_team(kmp_team_t *team, int new_nthreads);
+
 /* Calculate the identifier of the current thread */
 /* fast (and somewhat portable) way to get unique identifier of executing
    thread. Returns KMP_GTID_DNE if we haven't been assigned a gtid. */
 int __kmp_get_global_thread_id() {
   int i;
   kmp_info_t **other_threads;
   size_t stack_data;
   char *stack_addr;
#endif
     serial_team->t.t_ident = loc;
     serial_team->t.t_serialized = 1;
     serial_team->t.t_nproc = 1;
     serial_team->t.t_parent = this_thr->th.th_team;
     serial_team->t.t_sched.sched = this_thr->th.th_team->t.t_sched.sched;
     this_thr->th.th_team = serial_team;
     serial_team->t.t_master_tid = this_thr->th.th_info.ds.ds_tid;
 
-    KF_TRACE(10, ("__kmpc_serialized_parallel: T#d curtask=%p\n", global_tid,
+    KF_TRACE(10, ("__kmpc_serialized_parallel: T#%d curtask=%p\n", global_tid,
                   this_thr->th.th_current_task));
     KMP_ASSERT(this_thr->th.th_current_task->td_flags.executing == 1);
     this_thr->th.th_current_task->td_flags.executing = 0;
 
     __kmp_push_current_task_to_thread(this_thr, serial_team, 0);
 
     /* TODO: GEH: do ICVs work for nested serialized teams? Don't we need an
        implicit task for each serialized task represented by
#if OMPT_SUPPORT
         __ompt_lw_taskteam_init(&lw_taskteam, master_th, gtid,
                                 &ompt_parallel_data, return_address);
         __ompt_lw_taskteam_link(&lw_taskteam, master_th, 1, true);
       }
 #endif
 
       /* Change number of threads in the team if requested */
       if (master_set_numthreads) { // The parallel has num_threads clause
-        if (master_set_numthreads < master_th->th.th_teams_size.nth) {
+        if (master_set_numthreads <= master_th->th.th_teams_size.nth) {
           // AC: only can reduce number of threads dynamically, can't increase
           kmp_info_t **other_threads = parent_team->t.t_threads;
+          // NOTE: if using distributed barrier, we need to run this code block
+          // even when the team size appears not to have changed from the max.
+          int old_proc = master_th->th.th_teams_size.nth;
+          if (__kmp_barrier_release_pattern[bs_forkjoin_barrier] ==
+              bp_dist_bar) {
+            __kmp_resize_dist_barrier(parent_team, old_proc,
+                                      master_set_numthreads);
+            __kmp_add_threads_to_team(parent_team, master_set_numthreads);
+          }
           parent_team->t.t_nproc = master_set_numthreads;
           for (i = 0; i < master_set_numthreads; ++i) {
             other_threads[i]->th.th_team_nproc = master_set_numthreads;
           }
-          // Keep extra threads hot in the team for possible next parallels
         }
+        // Keep extra threads hot in the team for possible next parallels
         master_th->th.th_set_nproc = 0;
       }
 
 #if USE_DEBUGGER
       if (__kmp_debugging) { // Let debugger override number of threads.
         int nth = __kmp_omp_num_threads(loc);
         if (nth > 0) { // 0 means debugger doesn't want to change num threads
           master_set_numthreads = nth;

 
 #if KMP_DEBUG
     if (__kmp_tasking_mode != tskm_immediate_exec) {
       KMP_DEBUG_ASSERT(master_th->th.th_task_team ==
                        parent_team->t.t_task_team[master_th->th.th_task_state]);
     }
 #endif
 
+    // Need this to happen before we determine the number of threads, not while
+    // we are allocating the team
+    //__kmp_push_current_task_to_thread(master_th, parent_team, 0);
     int enter_teams = 0;
     if (parent_team->t.t_active_level >=
         master_th->th.th_current_task->td_icvs.max_active_levels) {
       nthreads = 1;
     } else {
       enter_teams = ((ap == NULL && active_level == 0) ||
                      (ap && teams_level > 0 && teams_level == level));
-      nthreads =
-          master_set_numthreads
+      nthreads = master_set_numthreads
                      ? master_set_numthreads
-              : get__nproc_2(
-                    parent_team,
-                    master_tid); // TODO: get nproc directly from current task
-
+                     // TODO: get nproc directly from current task
+                     : get__nproc_2(parent_team, master_tid);
       // Check if we need to take forkjoin lock? (no need for serialized
       // parallel out of teams construct). This code moved here from
       // __kmp_reserve_threads() to speedup nested serialized parallels.
       if (nthreads > 1) {
         if ((get__max_active_levels(master_th) == 1 &&
              (root->r.r_in_parallel && !enter_teams)) ||
             (__kmp_library == library_serial)) {
           KC_TRACE(10, ("__kmp_fork_call: T#%d serializing team; requested %d"
if ((nthreads_icv > 0) || (proc_bind_icv != proc_bind_default)) {
       /* allocate a new parallel team */
       KF_TRACE(10, ("__kmp_fork_call: before __kmp_allocate_team\n"));
       team = __kmp_allocate_team(root, nthreads, nthreads,
 #if OMPT_SUPPORT
                                  ompt_parallel_data,
 #endif
                                  proc_bind, &new_icvs,
                                  argc USE_NESTED_HOT_ARG(master_th));
+      if (__kmp_barrier_release_pattern[bs_forkjoin_barrier] == bp_dist_bar)
+        copy_icvs((kmp_internal_control_t *)team->t.b->team_icvs, &new_icvs);
     } else {
       /* allocate a new parallel team */
       KF_TRACE(10, ("__kmp_fork_call: before __kmp_allocate_team\n"));
       team = __kmp_allocate_team(root, nthreads, nthreads,
 #if OMPT_SUPPORT
                                  ompt_parallel_data,
 #endif
                                  proc_bind,
                                  &master_th->th.th_current_task->td_icvs,
                                  argc USE_NESTED_HOT_ARG(master_th));
+      if (__kmp_barrier_release_pattern[bs_forkjoin_barrier] == bp_dist_bar)
+        copy_icvs((kmp_internal_control_t *)team->t.b->team_icvs,
+                  &master_th->th.th_current_task->td_icvs);
     }
     KF_TRACE(
         10, ("__kmp_fork_call: after __kmp_allocate_team - team = %p\n", team));
 
     /* setup the new team */
     KMP_CHECK_UPDATE(team->t.t_master_tid, master_tid);
     KMP_CHECK_UPDATE(team->t.t_master_this_cons, master_this_cons);
     KMP_CHECK_UPDATE(team->t.t_ident, loc);
if (__itt_stack_caller_create_ptr && parent_team->t.t_serialized) {
       KMP_DEBUG_ASSERT(parent_team->t.t_stack_id != NULL);
       // destroy the stack stitching id on exit from the teams construct
       // if parent_team is active, then the id will be destroyed later on
       // by master of the league of teams
       __kmp_itt_stack_caller_destroy((__itt_caller)parent_team->t.t_stack_id);
       parent_team->t.t_stack_id = NULL;
     }
 #endif
+
+    if (team->t.t_nproc > 1 &&
+        __kmp_barrier_gather_pattern[bs_forkjoin_barrier] == bp_dist_bar) {
+      team->t.b->update_num_threads(team->t.t_nproc);
+      __kmp_add_threads_to_team(team, team->t.t_nproc);
+    }
   }
 
   KMP_MB();
 
 #if OMPT_SUPPORT
   ompt_data_t *parallel_data = &(team->t.ompt_team_info.parallel_data);
   void *codeptr = team->t.ompt_team_info.master_return_address;
 #endif
#if KMP_NESTED_HOT_TEAMS
       && __kmp_hot_teams_max_level && !__kmp_hot_teams_mode
 #endif
   ) {
     kmp_team_t *hot_team = root->r.r_hot_team;
     int f;
 
     __kmp_acquire_bootstrap_lock(&__kmp_forkjoin_lock);
 
+    if (__kmp_barrier_release_pattern[bs_forkjoin_barrier] == bp_dist_bar) {
+      __kmp_resize_dist_barrier(hot_team, hot_team->t.t_nproc, new_nth);
+    }
     // Release the extra threads we don't need any more.
     for (f = new_nth; f < hot_team->t.t_nproc; f++) {
       KMP_DEBUG_ASSERT(hot_team->t.t_threads[f] != NULL);
       if (__kmp_tasking_mode != tskm_immediate_exec) {
         // When decreasing team size, threads no longer in the team should unref
         // task team.
         hot_team->t.t_threads[f]->th.th_task_team = NULL;
       }
       __kmp_free_thread(hot_team->t.t_threads[f]);
       hot_team->t.t_threads[f] = NULL;
     }
     hot_team->t.t_nproc = new_nth;
 #if KMP_NESTED_HOT_TEAMS
     if (thread->th.th_hot_teams) {
       KMP_DEBUG_ASSERT(hot_team == thread->th.th_hot_teams[0].hot_team);
       thread->th.th_hot_teams[0].hot_team_nth = new_nth;
     }
 #endif
 
+    if (__kmp_barrier_release_pattern[bs_forkjoin_barrier] == bp_dist_bar) {
+      hot_team->t.b->update_num_threads(new_nth);
+      __kmp_add_threads_to_team(hot_team, new_nth);
+    }
+
     __kmp_release_bootstrap_lock(&__kmp_forkjoin_lock);
 
     // Update the t_nproc field in the threads that are still active.
     for (f = 0; f < new_nth; f++) {
       KMP_DEBUG_ASSERT(hot_team->t.t_threads[f] != NULL);
       hot_team->t.t_threads[f]->th.th_team_nproc = new_nth;
     }
     // Special flag in case omp_set_num_threads() call
#if KMP_AFFINITY_SUPPORTED
   this_thr->th.th_new_place = this_thr->th.th_current_place;
 #endif
   this_thr->th.th_root = master->th.th_root;
 
   /* setup the thread's cache of the team structure */
   this_thr->th.th_team_nproc = team->t.t_nproc;
   this_thr->th.th_team_master = master;
   this_thr->th.th_team_serialized = team->t.t_serialized;
-  TCW_PTR(this_thr->th.th_sleep_loc, NULL);
 
   KMP_DEBUG_ASSERT(team->t.t_implicit_task_taskdata);
 
   KF_TRACE(10, ("__kmp_initialize_info1: T#%d:%d this_thread=%p curtask=%p\n",
                 tid, gtid, this_thr, this_thr->th.th_current_task));
 
   __kmp_init_implicit_task(this_thr->th.th_team_master->th.th_ident, this_thr,
                            team, tid, TRUE);
if (__kmp_thread_pool) {
     KMP_DEBUG_ASSERT(new_thr->th.th_serial_team);
 
     TCW_4(__kmp_nth, __kmp_nth + 1);
 
     new_thr->th.th_task_state = 0;
     new_thr->th.th_task_state_top = 0;
     new_thr->th.th_task_state_stack_sz = 4;
 
+    if (__kmp_barrier_gather_pattern[bs_forkjoin_barrier] == bp_dist_bar) {
+      // Make sure pool thread has transitioned to waiting on own thread struct
+      KMP_DEBUG_ASSERT(new_thr->th.th_used_in_team.load() == 0);
+      // Thread activated in __kmp_allocate_team when increasing team size
+    }
+
 #ifdef KMP_ADJUST_BLOCKTIME
     /* Adjust blocktime back to zero if necessary */
     /* Middle initialization might not have occurred yet */
     if (!__kmp_env_blocktime && (__kmp_avail_proc > 0)) {
       if (__kmp_nth > __kmp_avail_proc) {
         __kmp_zero_bt = TRUE;
       }
     }
#endif
   kmp_balign_t *balign = new_thr->th.th_bar;
   for (b = 0; b < bs_last_barrier; ++b) {
     balign[b].bb.b_go = KMP_INIT_BARRIER_STATE;
     balign[b].bb.team = NULL;
     balign[b].bb.wait_flag = KMP_BARRIER_NOT_WAITING;
     balign[b].bb.use_oncore_barrier = 0;
   }
 
+  TCW_PTR(new_thr->th.th_sleep_loc, NULL);
+  new_thr->th.th_sleep_loc_type = flag_unset;
+
   new_thr->th.th_spin_here = FALSE;
   new_thr->th.th_next_waiting = 0;
 #if KMP_OS_UNIX
   new_thr->th.th_blocking = false;
 #endif
 
 #if KMP_AFFINITY_SUPPORTED
   new_thr->th.th_current_place = KMP_PLACE_UNDEFINED;

 #if KMP_DEBUG
     if (__kmp_tasking_mode != tskm_immediate_exec) {
       KA_TRACE(20, ("__kmp_allocate_team: hot team task_team[0] = %p "
                     "task_team[1] = %p before reinit\n",
                     team->t.t_task_team[0], team->t.t_task_team[1]));
     }
 #endif
 
+    if (team->t.t_nproc != new_nproc &&
+        __kmp_barrier_release_pattern[bs_forkjoin_barrier] == bp_dist_bar) {
+      // Distributed barrier may need a resize
+      int old_nthr = team->t.t_nproc;
+      __kmp_resize_dist_barrier(team, old_nthr, new_nproc);
+    }
+
     // Has the number of threads changed?
     /* Let's assume the most common case is that the number of threads is
        unchanged, and put that case first. */
     if (team->t.t_nproc == new_nproc) { // Check changes in number of threads
       KA_TRACE(20, ("__kmp_allocate_team: reusing hot team\n"));
       // This case can mean that omp_set_num_threads() was called and the hot
       // team size was already reduced, so we check the special flag
       if (team->t.t_size_changed == -1) {
#else
       KMP_CHECK_UPDATE(team->t.t_proc_bind, new_proc_bind);
 #endif /* KMP_AFFINITY_SUPPORTED */
     } else if (team->t.t_nproc > new_nproc) {
       KA_TRACE(20,
                ("__kmp_allocate_team: decreasing hot team thread count to %d\n",
                 new_nproc));
 
       team->t.t_size_changed = 1;
+      if (__kmp_barrier_release_pattern[bs_forkjoin_barrier] == bp_dist_bar) {
+        // Barrier size already reduced earlier in this function
+        // Activate team threads via th_used_in_team
+        __kmp_add_threads_to_team(team, new_nproc);
+      }
 #if KMP_NESTED_HOT_TEAMS
       if (__kmp_hot_teams_mode == 0) {
         // AC: saved number of threads should correspond to team's value in this
         // mode, can be bigger in mode 1, when hot team has threads in reserve
         KMP_DEBUG_ASSERT(hot_teams[level].hot_team_nth == team->t.t_nproc);
         hot_teams[level].hot_team_nth = new_nproc;
 #endif // KMP_NESTED_HOT_TEAMS
         /* release the extra threads we don't need any more */
#if (KMP_OS_LINUX || KMP_OS_FREEBSD) && KMP_AFFINITY_SUPPORTED
       if (KMP_AFFINITY_CAPABLE()) {
         KMP_CPU_ALLOC(old_mask);
       }
 #endif
 
       KA_TRACE(20,
                ("__kmp_allocate_team: increasing hot team thread count to %d\n",
                 new_nproc));
-
+      int old_nproc = team->t.t_nproc; // save old value and use to update only
       team->t.t_size_changed = 1;
 
 #if KMP_NESTED_HOT_TEAMS
       int avail_threads = hot_teams[level].hot_team_nth;
       if (new_nproc < avail_threads)
         avail_threads = new_nproc;
       kmp_info_t **other_threads = team->t.t_threads;
       for (f = team->t.t_nproc; f < avail_threads; ++f) {
#endif
         }
       }
       if (hot_teams[level].hot_team_nth >= new_nproc) {
         // we have all needed threads in reserve, no need to allocate any
         // this only possible in mode 1, cannot have reserved threads in mode 0
         KMP_DEBUG_ASSERT(__kmp_hot_teams_mode == 1);
         team->t.t_nproc = new_nproc; // just get reserved threads involved
       } else {
-        // we may have some threads in reserve, but not enough
-        team->t.t_nproc =
-            hot_teams[level]
-                .hot_team_nth; // get reserved threads involved if any
+        // We may have some threads in reserve, but not enough;
+        // get reserved threads involved if any.
+        team->t.t_nproc = hot_teams[level].hot_team_nth;
         hot_teams[level].hot_team_nth = new_nproc; // adjust hot team max size
 #endif // KMP_NESTED_HOT_TEAMS
         if (team->t.t_max_nproc < new_nproc) {
           /* reallocate larger arrays */
           __kmp_reallocate_team_arrays(team, new_nproc);
           __kmp_reinitialize_team(team, new_icvs, NULL);
         }
 
#if (KMP_OS_LINUX || KMP_OS_FREEBSD) && KMP_AFFINITY_SUPPORTED
           /* Restore initial primary thread's affinity mask */
           __kmp_set_system_affinity(old_mask, TRUE);
           KMP_CPU_FREE(old_mask);
         }
 #endif
 #if KMP_NESTED_HOT_TEAMS
       } // end of check of t_nproc vs. new_nproc vs. hot_team_nth
 #endif // KMP_NESTED_HOT_TEAMS
+      if (__kmp_barrier_release_pattern[bs_forkjoin_barrier] == bp_dist_bar) {
+        // Barrier size already increased earlier in this function
+        // Activate team threads via th_used_in_team
+        __kmp_add_threads_to_team(team, new_nproc);
+      }
       /* make sure everyone is syncronized */
-      int old_nproc = team->t.t_nproc; // save old value and use to update only
       // new threads below
       __kmp_initialize_team(team, new_nproc, new_icvs,
                             root->r.r_uber_thread->th.th_ident);
 
       /* reinitialize the threads */
       KMP_DEBUG_ASSERT(team->t.t_nproc == new_nproc);
       for (f = 0; f < team->t.t_nproc; ++f)
         __kmp_initialize_info(team->t.t_threads[f], team, f,
#endif
   KMP_MB();
   for (team = CCAST(kmp_team_t *, __kmp_team_pool); (team);) {
     /* TODO: consider resizing undersized teams instead of reaping them, now
        that we have a resizing mechanism */
     if (team->t.t_max_nproc >= max_nproc) {
       /* take this team from the team pool */
       __kmp_team_pool = team->t.t_next_pool;
 
+      if (max_nproc > 1 &&
+          __kmp_barrier_gather_pattern[bs_forkjoin_barrier] == bp_dist_bar) {
+        if (!team->t.b) { // Allocate barrier structure
+          team->t.b = distributedBarrier::allocate(__kmp_dflt_team_nth_ub);
+        }
+      }
+
       /* setup the team for fresh use */
       __kmp_initialize_team(team, new_nproc, new_icvs, NULL);
 
       KA_TRACE(20, ("__kmp_allocate_team: setting task_team[0] %p and "
                     "task_team[1] %p to NULL\n",
                     &team->t.t_task_team[0], &team->t.t_task_team[1]));
       team->t.t_task_team[0] = NULL;
       team->t.t_task_team[1] = NULL;
#endif
   }
 
   /* nothing available in the pool, no matter, make a new team! */
   KMP_MB();
   team = (kmp_team_t *)__kmp_allocate(sizeof(kmp_team_t));
 
   /* and set it up */
   team->t.t_max_nproc = max_nproc;
+  if (max_nproc > 1 &&
+      __kmp_barrier_gather_pattern[bs_forkjoin_barrier] == bp_dist_bar) {
+    // Allocate barrier structure
+    team->t.b = distributedBarrier::allocate(__kmp_dflt_team_nth_ub);
+  }
+
   /* NOTE well, for some reason allocating one big buffer and dividing it up
      seems to really hurt performance a lot on the P4, so, let's not use this */
   __kmp_allocate_team_arrays(team, max_nproc);
 
   KA_TRACE(20, ("__kmp_allocate_team: making a new team\n"));
   __kmp_initialize_team(team, new_nproc, new_icvs, NULL);
 
   KA_TRACE(20, ("__kmp_allocate_team: setting task_team[0] %p and task_team[1] "
#endif
     // Reset pointer to parent team only for non-hot teams.
     team->t.t_parent = NULL;
     team->t.t_level = 0;
     team->t.t_active_level = 0;
 
     /* free the worker threads */
     for (f = 1; f < team->t.t_nproc; ++f) {
       KMP_DEBUG_ASSERT(team->t.t_threads[f]);
+      if (__kmp_barrier_gather_pattern[bs_forkjoin_barrier] == bp_dist_bar) {
+        KMP_COMPARE_AND_STORE_ACQ32(&(team->t.t_threads[f]->th.th_used_in_team),
+                                    1, 2);
+      }
       __kmp_free_thread(team->t.t_threads[f]);
+    }
+
+    if (__kmp_barrier_gather_pattern[bs_forkjoin_barrier] == bp_dist_bar) {
+      if (team->t.b) {
+        // wake up thread at old location
+        team->t.b->go_release();
+        if (__kmp_dflt_blocktime != KMP_MAX_BLOCKTIME) {
+          for (f = 1; f < team->t.t_nproc; ++f) {
+            if (team->t.b->sleep[f].sleep) {
+              __kmp_atomic_resume_64(
+                  team->t.t_threads[f]->th.th_info.ds.ds_gtid,
+                  (kmp_atomic_flag_64<> *)NULL);
+            }
+          }
+        }
+        // Wait for threads to be removed from team
+        for (int f = 1; f < team->t.t_nproc; ++f) {
+          while (team->t.t_threads[f]->th.th_used_in_team.load() != 0)
+            KMP_CPU_PAUSE();
+        }
+      }
+    }
+
+    for (f = 1; f < team->t.t_nproc; ++f) {
       team->t.t_threads[f] = NULL;
     }
 
+    if (team->t.t_max_nproc > 1 &&
+        __kmp_barrier_gather_pattern[bs_forkjoin_barrier] == bp_dist_bar) {
+      distributedBarrier::deallocate(team->t.b);
+      team->t.b = NULL;
+    }
     /* put the team back in the team pool */
     /* TODO limit size of team pool, call reap_team if pool too large */
     team->t.t_next_pool = CCAST(kmp_team_t *, __kmp_team_pool);
     __kmp_team_pool = (volatile kmp_team_t *)team;
   } else { // Check if team was created for primary threads in teams construct
     // See if first worker is a CG root
     KMP_DEBUG_ASSERT(team->t.t_threads[1] &&
                      team->t.t_threads[1]->th.th_cg_roots);
static void __kmp_reap_thread(kmp_info_t *thread, int is_root) {
   gtid = thread->th.th_info.ds.ds_gtid;
 
   if (!is_root) {
     if (__kmp_dflt_blocktime != KMP_MAX_BLOCKTIME) {
       /* Assume the threads are at the fork barrier here */
       KA_TRACE(
           20, ("__kmp_reap_thread: releasing T#%d from fork barrier for reap\n",
                gtid));
-      /* Need release fence here to prevent seg faults for tree forkjoin barrier
-       * (GEH) */
+      if (__kmp_barrier_gather_pattern[bs_forkjoin_barrier] == bp_dist_bar) {
+        while (
+            !KMP_COMPARE_AND_STORE_ACQ32(&(thread->th.th_used_in_team), 0, 3))
+          KMP_CPU_PAUSE();
+        __kmp_resume_32(gtid, (kmp_flag_32<false, false> *)NULL);
+      } else {
+        /* Need release fence here to prevent seg faults for tree forkjoin
+           barrier (GEH) */
         kmp_flag_64<> flag(&thread->th.th_bar[bs_forkjoin_barrier].bb.b_go,
                            thread);
         __kmp_release_64(&flag);
       }
+    }
 
     // Terminate OS thread.
     __kmp_reap_worker(thread);
 
     // The thread was killed asynchronously.  If it was actively
     // spinning in the thread pool, decrement the global count.
     //
     // There is a small timing hole here - if the worker thread was just waking

 //__kmp_guided = kmp_sch_guided_iterative_chunked;
 //__kmp_auto = kmp_sch_guided_analytical_chunked; // AC: it is the default, no
 // need to repeat assignment
 // Barrier initialization. Moved here from __kmp_env_initialize() Barrier branch
 // bit control and barrier method control parts
 #if KMP_FAST_REDUCTION_BARRIER
 #define kmp_reduction_barrier_gather_bb ((int)1)
 #define kmp_reduction_barrier_release_bb ((int)1)
-#define kmp_reduction_barrier_gather_pat bp_hyper_bar
-#define kmp_reduction_barrier_release_pat bp_hyper_bar
+#define kmp_reduction_barrier_gather_pat __kmp_barrier_gather_pat_dflt
+#define kmp_reduction_barrier_release_pat __kmp_barrier_release_pat_dflt
 #endif // KMP_FAST_REDUCTION_BARRIER
   for (i = bs_plain_barrier; i < bs_last_barrier; i++) {
     __kmp_barrier_gather_branch_bits[i] = __kmp_barrier_gather_bb_dflt;
     __kmp_barrier_release_branch_bits[i] = __kmp_barrier_release_bb_dflt;
     __kmp_barrier_gather_pattern[i] = __kmp_barrier_gather_pat_dflt;
     __kmp_barrier_release_pattern[i] = __kmp_barrier_release_pat_dflt;
 #if KMP_FAST_REDUCTION_BARRIER
     if (i == bs_reduction_barrier) { // tested and confirmed on ALTIX only (

 void __kmp_omp_display_env(int verbose) {
   __kmp_acquire_bootstrap_lock(&__kmp_initz_lock);
   if (__kmp_init_serial == 0)
     __kmp_do_serial_initialize();
   __kmp_display_env_impl(!verbose, verbose);
   __kmp_release_bootstrap_lock(&__kmp_initz_lock);
 }
 
+// The team size is changing, so distributed barrier must be modified
+void __kmp_resize_dist_barrier(kmp_team_t *team, int old_nthreads,
+                               int new_nthreads) {
+  KMP_DEBUG_ASSERT(__kmp_barrier_release_pattern[bs_forkjoin_barrier] ==
+                   bp_dist_bar);
+  kmp_info_t **other_threads = team->t.t_threads;
+
+  // We want all the workers to stop waiting on the barrier while we adjust the
+  // size of the team.
+  for (int f = 1; f < old_nthreads; ++f) {
+    KMP_DEBUG_ASSERT(other_threads[f] != NULL);
+    // Ignore threads that are already inactive or not present in the team
+    if (team->t.t_threads[f]->th.th_used_in_team.load() == 0) {
+      // teams construct causes thread_limit to get passed in, and some of
+      // those could be inactive; just ignore them
+      continue;
+    }
+    // If thread is transitioning still to in_use state, wait for it
+    if (team->t.t_threads[f]->th.th_used_in_team.load() == 3) {
+      while (team->t.t_threads[f]->th.th_used_in_team.load() == 3)
+        KMP_CPU_PAUSE();
+    }
+    // The thread should be in_use now
+    KMP_DEBUG_ASSERT(team->t.t_threads[f]->th.th_used_in_team.load() == 1);
+    // Transition to unused state
+    team->t.t_threads[f]->th.th_used_in_team.store(2);
+    KMP_DEBUG_ASSERT(team->t.t_threads[f]->th.th_used_in_team.load() == 2);
+  }
+  // Release all the workers
+  kmp_uint64 new_value; // new value for go
+  new_value = team->t.b->go_release();
+
+  KMP_MFENCE();
+
+  // Workers should see transition status 2 and move to 0; but may need to be
+  // woken up first
+  size_t my_go_index;
+  int count = old_nthreads - 1;
+  while (count > 0) {
+    count = old_nthreads - 1;
+    for (int f = 1; f < old_nthreads; ++f) {
+      my_go_index = f / team->t.b->threads_per_go;
+      if (other_threads[f]->th.th_used_in_team.load() != 0) {
+        if (__kmp_dflt_blocktime != KMP_MAX_BLOCKTIME) { // Wake up the workers
+          kmp_atomic_flag_64<> *flag = (kmp_atomic_flag_64<> *)CCAST(
+              void *, other_threads[f]->th.th_sleep_loc);
+          __kmp_atomic_resume_64(other_threads[f]->th.th_info.ds.ds_gtid, flag);
+        }
+      } else {
+        KMP_DEBUG_ASSERT(team->t.t_threads[f]->th.th_used_in_team.load() == 0);
+        count--;
+      }
+    }
+  }
+  // Now update the barrier size
+  team->t.b->update_num_threads(new_nthreads);
+  team->t.b->go_reset();
+}
+
+void __kmp_add_threads_to_team(kmp_team_t *team, int new_nthreads) {
+  // Add the threads back to the team
+  KMP_DEBUG_ASSERT(team);
+  // Threads were paused and pointed at th_used_in_team temporarily during a
+  // resize of the team. We're going to set th_used_in_team to 3 to indicate to
+  // the thread that it should transition itself back into the team. Then, if
+  // blocktime isn't infinite, the thread could be sleeping, so we send a resume
+  // to wake it up.
+  for (int f = 1; f < new_nthreads; ++f) {
+    KMP_DEBUG_ASSERT(team->t.t_threads[f]);
+    KMP_COMPARE_AND_STORE_ACQ32(&(team->t.t_threads[f]->th.th_used_in_team), 0,
+                                3);
+    if (__kmp_dflt_blocktime != KMP_MAX_BLOCKTIME) { // Wake up sleeping threads
+      __kmp_resume_32(team->t.t_threads[f]->th.th_info.ds.ds_gtid,
+                      (kmp_flag_32<false, false> *)NULL);
+    }
+  }
+  // The threads should be transitioning to the team; when they are done, they
+  // should have set th_used_in_team to 1. This loop forces master to wait until
+  // all threads have moved into the team and are waiting in the barrier.
+  int count = new_nthreads - 1;
+  while (count > 0) {
+    count = new_nthreads - 1;
+    for (int f = 1; f < new_nthreads; ++f) {
+      if (team->t.t_threads[f]->th.th_used_in_team.load() == 1) {
+        count--;
+      }
+    }
+  }
+}
+
 // Globals and functions for hidden helper task
 kmp_info_t **__kmp_hidden_helper_threads;
 kmp_info_t *__kmp_hidden_helper_main_thread;
 std::atomic<kmp_int32> __kmp_unexecuted_hidden_helper_tasks;
 #if KMP_OS_LINUX
 kmp_int32 __kmp_hidden_helper_threads_num = 8;
 kmp_int32 __kmp_enable_hidden_helper = TRUE;
 #else

openmp/runtime/src/kmp_settings.cpp

 // TODO: Remove __kmp_barrier_pattern_name variable, remove loops from parse and
 // print functions, pass required data to functions through data argument.
 
 static void __kmp_stg_parse_barrier_pattern(char const *name, char const *value,
                                             void *data) {
   const char *var;
   /* ---------- Barrier method control ------------ */
 
+  static int dist_req = 0, non_dist_req = 0;
+  static bool warn = 1;
   for (int i = bs_plain_barrier; i < bs_last_barrier; i++) {
     var = __kmp_barrier_pattern_env_name[i];
 
     if ((strcmp(var, name) == 0) && (value != 0)) {
       int j;
       char *comma = CCAST(char *, strchr(value, ','));
 
       /* handle first parameter: gather pattern */
       for (j = bp_linear_bar; j < bp_last_bar; j++) {
         if (__kmp_match_with_sentinel(__kmp_barrier_pattern_name[j], value, 1,
                                       ',')) {
+          if (j == bp_dist_bar) {
+            dist_req++;
+          } else {
+            non_dist_req++;
+          }
           __kmp_barrier_gather_pattern[i] = (kmp_bar_pat_e)j;
           break;
         }
       }
       if (j == bp_last_bar) {
         KMP_WARNING(BarrGatherValueInvalid, name, value);
         KMP_INFORM(Using_str_Value, name,
                    __kmp_barrier_pattern_name[bp_linear_bar]);
       }
 
       /* handle second parameter: release pattern */
       if (comma != NULL) {
         for (j = bp_linear_bar; j < bp_last_bar; j++) {
           if (__kmp_str_match(__kmp_barrier_pattern_name[j], 1, comma + 1)) {
+            if (j == bp_dist_bar) {
+              dist_req++;
+            } else {
+              non_dist_req++;
+            }
             __kmp_barrier_release_pattern[i] = (kmp_bar_pat_e)j;
             break;
           }
         }
         if (j == bp_last_bar) {
           __kmp_msg(kmp_ms_warning,
                     KMP_MSG(BarrReleaseValueInvalid, name, comma + 1),
                     __kmp_msg_null);
           KMP_INFORM(Using_str_Value, name,
                      __kmp_barrier_pattern_name[bp_linear_bar]);
         }
       }
     }
   }
+  if ((dist_req == 0) && (non_dist_req != 0)) {
+    // Something was set to a barrier other than dist; set all others to hyper
+    for (int i = bs_plain_barrier; i < bs_last_barrier; i++) {
+      if (__kmp_barrier_release_pattern[i] == bp_dist_bar)
+        __kmp_barrier_release_pattern[i] = bp_hyper_bar;
+      if (__kmp_barrier_gather_pattern[i] == bp_dist_bar)
+        __kmp_barrier_gather_pattern[i] = bp_hyper_bar;
+    }
+  } else if (non_dist_req != 0) {
+    // some requests for dist, plus requests for others; set all to dist
+    if (non_dist_req > 0 && dist_req > 0 && warn) {
+      KMP_INFORM(BarrierPatternOverride, name,
+                 __kmp_barrier_pattern_name[bp_dist_bar]);
+      warn = 0;
+    }
+    for (int i = bs_plain_barrier; i < bs_last_barrier; i++) {
+      if (__kmp_barrier_release_pattern[i] != bp_dist_bar)
+        __kmp_barrier_release_pattern[i] = bp_dist_bar;
+      if (__kmp_barrier_gather_pattern[i] != bp_dist_bar)
+        __kmp_barrier_gather_pattern[i] = bp_dist_bar;
+    }
+  }
 } // __kmp_stg_parse_barrier_pattern
 
 static void __kmp_stg_print_barrier_pattern(kmp_str_buf_t *buffer,
                                             char const *name, void *data) {
   const char *var;
   for (int i = bs_plain_barrier; i < bs_last_barrier; i++) {
     var = __kmp_barrier_pattern_env_name[i];
     if (strcmp(var, name) == 0) {
       int j = __kmp_barrier_gather_pattern[i];
       int k = __kmp_barrier_release_pattern[i];
       if (__kmp_env_format) {
         KMP_STR_BUF_PRINT_NAME_EX(__kmp_barrier_pattern_env_name[i]);
       } else {
         __kmp_str_buf_print(buffer, "   %s='",
                             __kmp_barrier_pattern_env_name[i]);
       }
-      KMP_DEBUG_ASSERT(j < bs_last_barrier && k < bs_last_barrier);
+      KMP_DEBUG_ASSERT(j < bp_last_bar && k < bp_last_bar);
       __kmp_str_buf_print(buffer, "%s,%s'\n", __kmp_barrier_pattern_name[j],
                           __kmp_barrier_pattern_name[k]);
     }
   }
 } // __kmp_stg_print_barrier_pattern
 
 // -----------------------------------------------------------------------------
 // KMP_ABORT_DELAY

openmp/runtime/src/kmp_stats.h

 // KMP_setup_icv_copy     -- time in __kmp_setup_icv_copy
 // KMP_icv_copy           -- start/stop timer for any ICV copying
 // KMP_linear_gather      -- time in __kmp_linear_barrier_gather
 // KMP_linear_release     -- time in __kmp_linear_barrier_release
 // KMP_tree_gather        -- time in __kmp_tree_barrier_gather
 // KMP_tree_release       -- time in __kmp_tree_barrier_release
 // KMP_hyper_gather       -- time in __kmp_hyper_barrier_gather
 // KMP_hyper_release      -- time in __kmp_hyper_barrier_release
+// KMP_dist_gather       -- time in __kmp_dist_barrier_gather
+// KMP_dist_release      -- time in __kmp_dist_barrier_release
 // clang-format off
 #define KMP_FOREACH_DEVELOPER_TIMER(macro, arg)                                \
   macro(KMP_fork_call, 0, arg)                                                 \
   macro(KMP_join_call, 0, arg)                                                 \
   macro(KMP_end_split_barrier, 0, arg)                                         \
   macro(KMP_hier_gather, 0, arg)                                               \
   macro(KMP_hier_release, 0, arg)                                              \
   macro(KMP_hyper_gather, 0, arg)                                              \
   macro(KMP_hyper_release, 0, arg)                                             \
+  macro(KMP_dist_gather, 0, arg)                                              \
+  macro(KMP_dist_release, 0, arg)                                             \
   macro(KMP_linear_gather, 0, arg)                                             \
   macro(KMP_linear_release, 0, arg)                                            \
   macro(KMP_tree_gather, 0, arg)                                               \
   macro(KMP_tree_release, 0, arg)                                              \
   macro(USER_resume, 0, arg)                                                   \
   macro(USER_suspend, 0, arg)                                                  \
   macro(USER_mwait, 0, arg)                                                    \
   macro(KMP_allocate_team, 0, arg)                                             \

openmp/runtime/src/kmp_str.h

 kmp_str_loc_t __kmp_str_loc_init(char const *psource, bool init_fname);
 void __kmp_str_loc_numbers(char const *Psource, int *Line, int *Col);
 void __kmp_str_loc_free(kmp_str_loc_t *loc);
 
 int __kmp_str_eqf(char const *lhs, char const *rhs);
 char *__kmp_str_format(char const *format, ...);
 void __kmp_str_free(char **str);
 int __kmp_str_match(char const *target, int len, char const *data);
+bool __kmp_str_contains(char const *target, int len, char const *data);
 int __kmp_str_match_false(char const *data);
 int __kmp_str_match_true(char const *data);
 void __kmp_str_replace(char *str, char search_for, char replace_with);
 void __kmp_str_split(char *str, char delim, char **head, char **tail);
 char *__kmp_str_token(char *str, char const *delim, char **buf);
 int __kmp_str_to_int(char const *str, char sentinel);
 
 void __kmp_str_to_size(char const *str, size_t *out, size_t dfactor,

openmp/runtime/src/kmp_str.cpp

int __kmp_str_match(char const *target, int len, char const *data) {
   for (i = 0; target[i] && data[i]; ++i) {
     if (TOLOWER(target[i]) != TOLOWER(data[i])) {
       return FALSE;
     }
   }
   return ((len > 0) ? i >= len : (!target[i] && (len || !data[i])));
 } // __kmp_str_match
 
+// If data contains all of target, returns true, otherwise returns false.
+// len should be the length of target
+bool __kmp_str_contains(char const *target, int len, char const *data) {
+  int i = 0, j = 0, start = 0;
+  if (target == NULL || data == NULL) {
+    return FALSE;
+  }
+  while (target[i]) {
+    if (!data[j])
+      return FALSE;
+    if (TOLOWER(target[i]) != TOLOWER(data[j])) {
+      j = start + 1;
+      start = j;
+      i = 0;
+    } else {
+      if (i == 0)
+        start = j;
+      j++;
+      i++;
+    }
+  }
+
+  return i == len;
+} // __kmp_str_contains
+
 int __kmp_str_match_false(char const *data) {
   int result =
       __kmp_str_match("false", 1, data) || __kmp_str_match("off", 2, data) ||
       __kmp_str_match("0", 1, data) || __kmp_str_match(".false.", 2, data) ||
       __kmp_str_match(".f.", 2, data) || __kmp_str_match("no", 1, data) ||
       __kmp_str_match("disabled", 0, data);
   return result;
 } // __kmp_str_match_false

openmp/runtime/src/kmp_tasking.cpp

while (1) { // Inner loop to find a task and execute it
             // extra barrier mode, tasks do not sleep at the separate tasking
             // barrier, so this isn't a problem.
             asleep = 0;
             if ((__kmp_tasking_mode == tskm_task_teams) &&
                 (__kmp_dflt_blocktime != KMP_MAX_BLOCKTIME) &&
                 (TCR_PTR(CCAST(void *, other_thread->th.th_sleep_loc)) !=
                  NULL)) {
               asleep = 1;
-              __kmp_null_resume_wrapper(__kmp_gtid_from_thread(other_thread),
-                                        other_thread->th.th_sleep_loc);
+              __kmp_null_resume_wrapper(other_thread);
               // A sleeping thread should not have any tasks on it's queue.
               // There is a slight possibility that it resumes, steals a task
               // from another thread, which spawns more tasks, all in the time
               // that it takes this thread to check => don't write an assertion
               // that the victim's queue is empty.  Try stealing from a
               // different thread.
             }
           } while (asleep);
int __kmp_execute_tasks_64(
     kmp_info_t *thread, kmp_int32 gtid, kmp_flag_64<C, S> *flag, int final_spin,
     int *thread_finished USE_ITT_BUILD_ARG(void *itt_sync_obj),
     kmp_int32 is_constrained) {
   return __kmp_execute_tasks_template(
       thread, gtid, flag, final_spin,
       thread_finished USE_ITT_BUILD_ARG(itt_sync_obj), is_constrained);
 }
 
+template <bool C, bool S>
+int __kmp_atomic_execute_tasks_64(
+    kmp_info_t *thread, kmp_int32 gtid, kmp_atomic_flag_64<C, S> *flag,
+    int final_spin, int *thread_finished USE_ITT_BUILD_ARG(void *itt_sync_obj),
+    kmp_int32 is_constrained) {
+  return __kmp_execute_tasks_template(
+      thread, gtid, flag, final_spin,
+      thread_finished USE_ITT_BUILD_ARG(itt_sync_obj), is_constrained);
+}
+
 int __kmp_execute_tasks_oncore(
     kmp_info_t *thread, kmp_int32 gtid, kmp_flag_oncore *flag, int final_spin,
     int *thread_finished USE_ITT_BUILD_ARG(void *itt_sync_obj),
     kmp_int32 is_constrained) {
   return __kmp_execute_tasks_template(
       thread, gtid, flag, final_spin,
       thread_finished USE_ITT_BUILD_ARG(itt_sync_obj), is_constrained);
 }
template int __kmp_execute_tasks_64<false, true>(kmp_info_t *, kmp_int32,
                                                  kmp_int32);
 
 template int __kmp_execute_tasks_64<true, false>(kmp_info_t *, kmp_int32,
                                                  kmp_flag_64<true, false> *,
                                                  int,
                                                  int *USE_ITT_BUILD_ARG(void *),
                                                  kmp_int32);
 
+template int __kmp_atomic_execute_tasks_64<false, true>(
+    kmp_info_t *, kmp_int32, kmp_atomic_flag_64<false, true> *, int,
+    int *USE_ITT_BUILD_ARG(void *), kmp_int32);
+
+template int __kmp_atomic_execute_tasks_64<true, false>(
+    kmp_info_t *, kmp_int32, kmp_atomic_flag_64<true, false> *, int,
+    int *USE_ITT_BUILD_ARG(void *), kmp_int32);
+
 // __kmp_enable_tasking: Allocate task team and resume threads sleeping at the
 // next barrier so they can assist in executing enqueued tasks.
 // First thread in allocates the task team atomically.
 static void __kmp_enable_tasking(kmp_task_team_t *task_team,
                                  kmp_info_t *this_thr) {
   kmp_thread_data_t *threads_data;
   int nthreads, i, is_init_thread;
 
static void __kmp_enable_tasking(kmp_task_team_t *task_team,
   KMP_DEBUG_ASSERT(threads_data != NULL);
 
   if (__kmp_tasking_mode == tskm_task_teams &&
       (__kmp_dflt_blocktime != KMP_MAX_BLOCKTIME)) {
     // Release any threads sleeping at the barrier, so that they can steal
     // tasks and execute them.  In extra barrier mode, tasks do not sleep
     // at the separate tasking barrier, so this isn't a problem.
     for (i = 0; i < nthreads; i++) {
-      volatile void *sleep_loc;
+      void *sleep_loc;
       kmp_info_t *thread = threads_data[i].td.td_thr;
 
       if (i == this_thr->th.th_info.ds.ds_tid) {
         continue;
       }
       // Since we haven't locked the thread's suspend mutex lock at this
       // point, there is a small window where a thread might be putting
       // itself to sleep, but hasn't set the th_sleep_loc field yet.
       // To work around this, __kmp_execute_tasks_template() periodically checks
       // see if other threads are sleeping (using the same random mechanism that
       // is used for task stealing) and awakens them if they are.
       if ((sleep_loc = TCR_PTR(CCAST(void *, thread->th.th_sleep_loc))) !=
           NULL) {
         KF_TRACE(50, ("__kmp_enable_tasking: T#%d waking up thread T#%d\n",
                       __kmp_gtid_from_thread(this_thr),
                       __kmp_gtid_from_thread(thread)));
-        __kmp_null_resume_wrapper(__kmp_gtid_from_thread(thread), sleep_loc);
+        __kmp_null_resume_wrapper(thread);
       } else {
         KF_TRACE(50, ("__kmp_enable_tasking: T#%d don't wake up thread T#%d\n",
                       __kmp_gtid_from_thread(this_thr),
                       __kmp_gtid_from_thread(thread)));
       }
     }
   }
 
#endif
 
       done = FALSE; // Because th_task_team pointer is not NULL for this thread
 
       KA_TRACE(10, ("__kmp_wait_to_unref_task_team: Waiting for T#%d to "
                     "unreference task_team\n",
                     __kmp_gtid_from_thread(thread)));
 
       if (__kmp_dflt_blocktime != KMP_MAX_BLOCKTIME) {
-        volatile void *sleep_loc;
+        void *sleep_loc;
         // If the thread is sleeping, awaken it.
         if ((sleep_loc = TCR_PTR(CCAST(void *, thread->th.th_sleep_loc))) !=
             NULL) {
           KA_TRACE(
               10,
               ("__kmp_wait_to_unref_task_team: T#%d waking up thread T#%d\n",
                __kmp_gtid_from_thread(thread), __kmp_gtid_from_thread(thread)));
-          __kmp_null_resume_wrapper(__kmp_gtid_from_thread(thread), sleep_loc);
+          __kmp_null_resume_wrapper(thread);
         }
       }
     }
     if (done) {
       break;
     }
 
     // If oversubscribed or have waited a bit, yield.

openmp/runtime/src/kmp_wait_release.h

 higher level operations such as barriers and fork/join.
 */
 
 /*!
 @ingroup WAIT_RELEASE
 @{
 */
 
-/*!
- * The flag_type describes the storage used for the flag.
- */
-enum flag_type {
-  flag32, /**< 32 bit flags */
-  flag64, /**< 64 bit flags */
-  flag_oncore /**< special 64-bit flag for on-core barrier (hierarchical) */
-};
-
 struct flag_properties {
   unsigned int type : 16;
   unsigned int reserved : 16;
 };
 
-/*!
- * Base class for wait/release volatile flag
- */
-template <typename P> class kmp_flag_native {
-  volatile P *loc;
-  flag_properties t;
+template <enum flag_type FlagType> struct flag_traits {};
+
+template <> struct flag_traits<flag32> {
+  typedef kmp_uint32 flag_t;
+  static const flag_type t = flag32;
+  static inline flag_t tcr(flag_t f) { return TCR_4(f); }
+  static inline flag_t test_then_add4(volatile flag_t *f) {
+    return KMP_TEST_THEN_ADD4_32(RCAST(volatile kmp_int32 *, f));
+  }
+  static inline flag_t test_then_or(volatile flag_t *f, flag_t v) {
+    return KMP_TEST_THEN_OR32(f, v);
+  }
+  static inline flag_t test_then_and(volatile flag_t *f, flag_t v) {
+    return KMP_TEST_THEN_AND32(f, v);
+  }
+};
+
+template <> struct flag_traits<atomic_flag64> {
+  typedef kmp_uint64 flag_t;
+  static const flag_type t = atomic_flag64;
+  static inline flag_t tcr(flag_t f) { return TCR_8(f); }
+  static inline flag_t test_then_add4(volatile flag_t *f) {
+    return KMP_TEST_THEN_ADD4_64(RCAST(volatile kmp_int64 *, f));
+  }
+  static inline flag_t test_then_or(volatile flag_t *f, flag_t v) {
+    return KMP_TEST_THEN_OR64(f, v);
+  }
+  static inline flag_t test_then_and(volatile flag_t *f, flag_t v) {
+    return KMP_TEST_THEN_AND64(f, v);
+  }
+};
+
+template <> struct flag_traits<flag64> {
+  typedef kmp_uint64 flag_t;
+  static const flag_type t = flag64;
+  static inline flag_t tcr(flag_t f) { return TCR_8(f); }
+  static inline flag_t test_then_add4(volatile flag_t *f) {
+    return KMP_TEST_THEN_ADD4_64(RCAST(volatile kmp_int64 *, f));
+  }
+  static inline flag_t test_then_or(volatile flag_t *f, flag_t v) {
+    return KMP_TEST_THEN_OR64(f, v);
+  }
+  static inline flag_t test_then_and(volatile flag_t *f, flag_t v) {
+    return KMP_TEST_THEN_AND64(f, v);
+  }
+};
+
+template <> struct flag_traits<flag_oncore> {
+  typedef kmp_uint64 flag_t;
+  static const flag_type t = flag_oncore;
+  static inline flag_t tcr(flag_t f) { return TCR_8(f); }
+  static inline flag_t test_then_add4(volatile flag_t *f) {
+    return KMP_TEST_THEN_ADD4_64(RCAST(volatile kmp_int64 *, f));
+  }
+  static inline flag_t test_then_or(volatile flag_t *f, flag_t v) {
+    return KMP_TEST_THEN_OR64(f, v);
+  }
+  static inline flag_t test_then_and(volatile flag_t *f, flag_t v) {
+    return KMP_TEST_THEN_AND64(f, v);
+  }
+};
+
+/*! Base class for all flags */
+template <flag_type FlagType> class kmp_flag {
+protected:
+  flag_properties t; /**< "Type" of the flag in loc */
+  kmp_info_t *waiting_threads[1]; /**< Threads sleeping on this thread. */
+  kmp_uint32 num_waiting_threads; /**< #threads sleeping on this thread. */
+  std::atomic<bool> *sleepLoc;
 
 public:
-  typedef P flag_t;
-  kmp_flag_native(volatile P *p, flag_type ft)
-      : loc(p), t({(short unsigned int)ft, 0U}) {}
-  volatile P *get() { return loc; }
-  void *get_void_p() { return RCAST(void *, CCAST(P *, loc)); }
-  void set(volatile P *new_loc) { loc = new_loc; }
+  typedef flag_traits<FlagType> traits_type;
+  kmp_flag() : t({FlagType, 0U}), num_waiting_threads(0), sleepLoc(nullptr) {}
+  kmp_flag(int nwaiters)
+      : t({FlagType, 0U}), num_waiting_threads(nwaiters), sleepLoc(nullptr) {}
+  kmp_flag(std::atomic<bool> *sloc)
+      : t({FlagType, 0U}), num_waiting_threads(0), sleepLoc(sloc) {}
+  /*! @result the flag_type */
   flag_type get_type() { return (flag_type)(t.type); }
-  P load() { return *loc; }
-  void store(P val) { *loc = val; }
+
+  /*! param i in   index into waiting_threads
+   *  @result the thread that is waiting at index i */
+  kmp_info_t *get_waiter(kmp_uint32 i) {
+    KMP_DEBUG_ASSERT(i < num_waiting_threads);
+    return waiting_threads[i];
+  }
+  /*! @result num_waiting_threads */
+  kmp_uint32 get_num_waiters() { return num_waiting_threads; }
+  /*! @param thr in   the thread which is now waiting
+   *  Insert a waiting thread at index 0. */
+  void set_waiter(kmp_info_t *thr) {
+    waiting_threads[0] = thr;
+    num_waiting_threads = 1;
+  }
+  enum barrier_type get_bt() { return bs_last_barrier; }
 };
 
-/*!
- * Base class for wait/release atomic flag
- */
-template <typename P> class kmp_flag {
-  std::atomic<P>
-      *loc; /**< Pointer to the flag storage that is modified by another thread
-             */
-  flag_properties t; /**< "Type" of the flag in loc */
+/*! Base class for wait/release volatile flag */
+template <typename PtrType, flag_type FlagType, bool Sleepable>
+class kmp_flag_native : public kmp_flag<FlagType> {
+protected:
+  volatile PtrType *loc;
+  PtrType checker; /**< When flag==checker, it has been released. */
+  typedef flag_traits<FlagType> traits_type;
+
 public:
-  typedef P flag_t;
-  kmp_flag(std::atomic<P> *p, flag_type ft)
-      : loc(p), t({(short unsigned int)ft, 0U}) {}
-  /*!
-   * @result the pointer to the actual flag
-   */
-  std::atomic<P> *get() { return loc; }
-  /*!
-   * @result void* pointer to the actual flag
-   */
+  typedef PtrType flag_t;
+  kmp_flag_native(volatile PtrType *p) : kmp_flag<FlagType>(), loc(p) {}
+  kmp_flag_native(volatile PtrType *p, kmp_info_t *thr)
+      : kmp_flag<FlagType>(1), loc(p) {
+    this->waiting_threads[0] = thr;
+  }
+  kmp_flag_native(volatile PtrType *p, PtrType c)
+      : kmp_flag<FlagType>(), loc(p), checker(c) {}
+  kmp_flag_native(volatile PtrType *p, PtrType c, std::atomic<bool> *sloc)
+      : kmp_flag<FlagType>(sloc), loc(p), checker(c) {}
+  virtual ~kmp_flag_native() {}
+  void *operator new(size_t size) { return __kmp_allocate(size); }
+  void operator delete(void *p) { __kmp_free(p); }
+  volatile PtrType *get() { return loc; }
+  void *get_void_p() { return RCAST(void *, CCAST(PtrType *, loc)); }
+  void set(volatile PtrType *new_loc) { loc = new_loc; }
+  PtrType load() { return *loc; }
+  void store(PtrType val) { *loc = val; }
+  /*! @result true if the flag object has been released. */
+  virtual bool done_check() {
+    if (Sleepable && !(this->sleepLoc))
+      return (traits_type::tcr(*(this->get())) & ~KMP_BARRIER_SLEEP_STATE) ==
+             checker;
+    else
+      return traits_type::tcr(*(this->get())) == checker;
+  }
+  /*! @param old_loc in   old value of flag
+   *  @result true if the flag's old value indicates it was released. */
+  virtual bool done_check_val(PtrType old_loc) { return old_loc == checker; }
+  /*! @result true if the flag object is not yet released.
+   * Used in __kmp_wait_template like:
+   * @code
+   * while (flag.notdone_check()) { pause(); }
+   * @endcode */
+  virtual bool notdone_check() {
+    return traits_type::tcr(*(this->get())) != checker;
+  }
+  /*! @result Actual flag value before release was applied.
+   * Trigger all waiting threads to run by modifying flag to release state. */
+  void internal_release() {
+    (void)traits_type::test_then_add4((volatile PtrType *)this->get());
+  }
+  /*! @result Actual flag value before sleep bit(s) set.
+   * Notes that there is at least one thread sleeping on the flag by setting
+   * sleep bit(s). */
+  PtrType set_sleeping() {
+    if (this->sleepLoc) {
+      this->sleepLoc->store(true);
+      return *(this->get());
+    }
+    return traits_type::test_then_or((volatile PtrType *)this->get(),
+                                     KMP_BARRIER_SLEEP_STATE);
+  }
+  /*! @result Actual flag value before sleep bit(s) cleared.
+   * Notes that there are no longer threads sleeping on the flag by clearing
+   * sleep bit(s). */
+  void unset_sleeping() {
+    if (this->sleepLoc) {
+      this->sleepLoc->store(false);
+      return;
+    }
+    traits_type::test_then_and((volatile PtrType *)this->get(),
+                               ~KMP_BARRIER_SLEEP_STATE);
+  }
+  /*! @param old_loc in   old value of flag
+   * Test if there are threads sleeping on the flag's old value in old_loc. */
+  bool is_sleeping_val(PtrType old_loc) {
+    if (this->sleepLoc)
+      return this->sleepLoc->load();
+    return old_loc & KMP_BARRIER_SLEEP_STATE;
+  }
+  /*! Test whether there are threads sleeping on the flag. */
+  bool is_sleeping() {
+    if (this->sleepLoc)
+      return this->sleepLoc->load();
+    return is_sleeping_val(*(this->get()));
+  }
+  bool is_any_sleeping() {
+    if (this->sleepLoc)
+      return this->sleepLoc->load();
+    return is_sleeping_val(*(this->get()));
+  }
+  kmp_uint8 *get_stolen() { return NULL; }
+};
+
+/*! Base class for wait/release atomic flag */
+template <typename PtrType, flag_type FlagType, bool Sleepable>
+class kmp_flag_atomic : public kmp_flag<FlagType> {
+protected:
+  std::atomic<PtrType> *loc; /**< Pointer to flag location to wait on */
+  PtrType checker; /**< Flag == checker means it has been released. */
+public:
+  typedef flag_traits<FlagType> traits_type;
+  typedef PtrType flag_t;
+  kmp_flag_atomic(std::atomic<PtrType> *p) : kmp_flag<FlagType>(), loc(p) {}
+  kmp_flag_atomic(std::atomic<PtrType> *p, kmp_info_t *thr)
+      : kmp_flag<FlagType>(1), loc(p) {
+    this->waiting_threads[0] = thr;
+  }
+  kmp_flag_atomic(std::atomic<PtrType> *p, PtrType c)
+      : kmp_flag<FlagType>(), loc(p), checker(c) {}
+  kmp_flag_atomic(std::atomic<PtrType> *p, PtrType c, std::atomic<bool> *sloc)
+      : kmp_flag<FlagType>(sloc), loc(p), checker(c) {}
+  /*! @result the pointer to the actual flag */
+  std::atomic<PtrType> *get() { return loc; }
+  /*! @result void* pointer to the actual flag */
   void *get_void_p() { return RCAST(void *, loc); }
-  /*!
-   * @param new_loc in   set loc to point at new_loc
-   */
-  void set(std::atomic<P> *new_loc) { loc = new_loc; }
-  /*!
-   * @result the flag_type
-   */
-  flag_type get_type() { return (flag_type)(t.type); }
-  /*!
-   * @result flag value
-   */
-  P load() { return loc->load(std::memory_order_acquire); }
-  /*!
-   * @param val the new flag value to be stored
-   */
-  void store(P val) { loc->store(val, std::memory_order_release); }
-  // Derived classes must provide the following:
-  /*
-  kmp_info_t * get_waiter(kmp_uint32 i);
-  kmp_uint32 get_num_waiters();
-  bool done_check();
-  bool done_check_val(P old_loc);
-  bool notdone_check();
-  P internal_release();
-  void suspend(int th_gtid);
-  void mwait(int th_gtid);
-  void resume(int th_gtid);
-  P set_sleeping();
-  P unset_sleeping();
-  bool is_sleeping();
-  bool is_any_sleeping();
-  bool is_sleeping_val(P old_loc);
-  int execute_tasks(kmp_info_t *this_thr, kmp_int32 gtid, int final_spin,
-                    int *thread_finished
-                    USE_ITT_BUILD_ARG(void * itt_sync_obj), kmp_int32
-                    is_constrained);
-  */
+  /*! @param new_loc in   set loc to point at new_loc */
+  void set(std::atomic<PtrType> *new_loc) { loc = new_loc; }
+  /*! @result flag value */
+  PtrType load() { return loc->load(std::memory_order_acquire); }
+  /*! @param val the new flag value to be stored */
+  void store(PtrType val) { loc->store(val, std::memory_order_release); }
+  /*! @result true if the flag object has been released. */
+  bool done_check() {
+    if (Sleepable && !(this->sleepLoc))
+      return (this->load() & ~KMP_BARRIER_SLEEP_STATE) == checker;
+    else
+      return this->load() == checker;
+  }
+  /*! @param old_loc in   old value of flag
+   * @result true if the flag's old value indicates it was released. */
+  bool done_check_val(PtrType old_loc) { return old_loc == checker; }
+  /*! @result true if the flag object is not yet released.
+   * Used in __kmp_wait_template like:
+   * @code
+   * while (flag.notdone_check()) { pause(); }
+   * @endcode */
+  bool notdone_check() { return this->load() != checker; }
+  /*! @result Actual flag value before release was applied.
+   * Trigger all waiting threads to run by modifying flag to release state. */
+  void internal_release() { KMP_ATOMIC_ADD(this->get(), 4); }
+  /*! @result Actual flag value before sleep bit(s) set.
+   * Notes that there is at least one thread sleeping on the flag by setting
+   * sleep bit(s). */
+  PtrType set_sleeping() {
+    if (this->sleepLoc) {
+      this->sleepLoc->store(true);
+      return *(this->get());
+    }
+    return KMP_ATOMIC_OR(this->get(), KMP_BARRIER_SLEEP_STATE);
+  }
+  /*! @result Actual flag value before sleep bit(s) cleared.
+   * Notes that there are no longer threads sleeping on the flag by clearing
+   * sleep bit(s). */
+  void unset_sleeping() {
+    if (this->sleepLoc) {
+      this->sleepLoc->store(false);
+      return;
+    }
+    KMP_ATOMIC_AND(this->get(), ~KMP_BARRIER_SLEEP_STATE);
+  }
+  /*! @param old_loc in   old value of flag
+   * Test whether there are threads sleeping on flag's old value in old_loc. */
+  bool is_sleeping_val(PtrType old_loc) {
+    if (this->sleepLoc)
+      return this->sleepLoc->load();
+    return old_loc & KMP_BARRIER_SLEEP_STATE;
+  }
+  /*! Test whether there are threads sleeping on the flag. */
+  bool is_sleeping() {
+    if (this->sleepLoc)
+      return this->sleepLoc->load();
+    return is_sleeping_val(this->load());
+  }
+  bool is_any_sleeping() {
+    if (this->sleepLoc)
+      return this->sleepLoc->load();
+    return is_sleeping_val(this->load());
+  }
+  kmp_uint8 *get_stolen() { return NULL; }
 };
 
 #if OMPT_SUPPORT
 OMPT_NOINLINE
 static void __ompt_implicit_task_end(kmp_info_t *this_thr,
                                      ompt_state_t ompt_state,
                                      ompt_data_t *tId) {
   int ds_tid = this_thr->th.th_info.ds.ds_tid;

 */
 #if OMPT_SUPPORT
   ompt_state_t ompt_entry_state;
   ompt_data_t *tId;
   if (ompt_enabled.enabled) {
     ompt_entry_state = this_thr->th.ompt_thread_info.state;
     if (!final_spin || ompt_entry_state != ompt_state_wait_barrier_implicit ||
         KMP_MASTER_TID(this_thr->th.th_info.ds.ds_tid)) {
-      ompt_lw_taskteam_t *team =
-          this_thr->th.th_team->t.ompt_serialized_team_info;
+      ompt_lw_taskteam_t *team = NULL;
+      if (this_thr->th.th_team)
+        team = this_thr->th.th_team->t.ompt_serialized_team_info;
       if (team) {
         tId = &(team->ompt_task_info.task_data);
       } else {
         tId = OMPT_CUR_TASK_DATA(this_thr);
       }
     } else {
       tId = &(this_thr->th.ompt_thread_info.task_data);
     }
if (__kmp_tasking_mode != tskm_immediate_exec) {
          1) A newly-created thread is first being released by
          __kmp_fork_barrier(), and its task team has not been set up yet.
          2) All tasks have been executed to completion.
          3) Tasking is off for this region.  This could be because we are in a
          serialized region (perhaps the outer one), or else tasking was manually
          disabled (KMP_TASKING=0).  */
       if (task_team != NULL) {
         if (TCR_SYNC_4(task_team->tt.tt_active)) {
-          if (KMP_TASKING_ENABLED(task_team))
+          if (KMP_TASKING_ENABLED(task_team)) {
             flag->execute_tasks(
                 this_thr, th_gtid, final_spin,
                 &tasks_completed USE_ITT_BUILD_ARG(itt_sync_obj), 0);
-          else
+          } else
             this_thr->th.th_reap_state = KMP_SAFE_TO_REAP;
         } else {
           KMP_DEBUG_ASSERT(!KMP_MASTER_TID(this_thr->th.th_info.ds.ds_tid));
 #if OMPT_SUPPORT
           // task-team is done now, other cases should be catched above
           if (final_spin && ompt_enabled.enabled)
             __ompt_implicit_task_end(this_thr, ompt_entry_state, tId);
 #endif
#endif
     // To avoid a race, check flag between 'monitor' and 'mwait'. A write to
     // the address could happen after the last time we checked and before
     // monitoring started, in which case monitor can't detect the change.
     if (flag->done_check())
       flag->unset_sleeping();
     else {
       // if flag changes here, wake-up happens immediately
       TCW_PTR(th->th.th_sleep_loc, (void *)flag);
+      th->th.th_sleep_loc_type = flag->get_type();
       __kmp_unlock_suspend_mx(th);
       KF_TRACE(50, ("__kmp_mwait_template: T#%d calling mwait\n", th_gtid));
 #if KMP_HAVE_UMWAIT
       if (__kmp_umwait_enabled) {
         __kmp_umwait(1, 100); // to do: enable ctrl via hints, backoff counter
       }
 #elif KMP_HAVE_MWAIT
       if (__kmp_mwait_enabled) {
         __kmp_mm_mwait(0, __kmp_mwait_hints);
       }
 #endif
       KF_TRACE(50, ("__kmp_mwait_template: T#%d mwait done\n", th_gtid));
       __kmp_lock_suspend_mx(th);
       // Clean up sleep info; doesn't matter how/why this thread stopped waiting
       if (flag->is_sleeping())
         flag->unset_sleeping();
       TCW_PTR(th->th.th_sleep_loc, NULL);
+      th->th.th_sleep_loc_type = flag_unset;
     }
     // Mark thread as active again
     th->th.th_active = TRUE;
     if (TCR_4(th->th.th_in_pool)) {
       KMP_ATOMIC_INC(&__kmp_thread_pool_active_nth);
       th->th.th_active_in_pool = TRUE;
     }
   } // Drop out to main wait loop to check flag, handle tasks, etc.
if (flag->is_any_sleeping()) {
                         gtid, wait_gtid, flag->get()));
           flag->resume(wait_gtid); // unsets flag's current_waiter when done
         }
       }
     }
   }
 }
 
-template <typename FlagType> struct flag_traits {};
-
-template <> struct flag_traits<kmp_uint32> {
-  typedef kmp_uint32 flag_t;
-  static const flag_type t = flag32;
-  static inline flag_t tcr(flag_t f) { return TCR_4(f); }
-  static inline flag_t test_then_add4(volatile flag_t *f) {
-    return KMP_TEST_THEN_ADD4_32(RCAST(volatile kmp_int32 *, f));
-  }
-  static inline flag_t test_then_or(volatile flag_t *f, flag_t v) {
-    return KMP_TEST_THEN_OR32(f, v);
-  }
-  static inline flag_t test_then_and(volatile flag_t *f, flag_t v) {
-    return KMP_TEST_THEN_AND32(f, v);
-  }
-};
-
-template <> struct flag_traits<kmp_uint64> {
-  typedef kmp_uint64 flag_t;
-  static const flag_type t = flag64;
-  static inline flag_t tcr(flag_t f) { return TCR_8(f); }
-  static inline flag_t test_then_add4(volatile flag_t *f) {
-    return KMP_TEST_THEN_ADD4_64(RCAST(volatile kmp_int64 *, f));
-  }
-  static inline flag_t test_then_or(volatile flag_t *f, flag_t v) {
-    return KMP_TEST_THEN_OR64(f, v);
-  }
-  static inline flag_t test_then_and(volatile flag_t *f, flag_t v) {
-    return KMP_TEST_THEN_AND64(f, v);
-  }
-};
-
-// Basic flag that does not use C11 Atomics
-template <typename FlagType, bool Sleepable>
-class kmp_basic_flag_native : public kmp_flag_native<FlagType> {
-  typedef flag_traits<FlagType> traits_type;
-  FlagType checker; /**< Value to compare flag to to check if flag has been
-                       released. */
-  kmp_info_t
-      *waiting_threads[1]; /**< Array of threads sleeping on this thread. */
-  kmp_uint32
-      num_waiting_threads; /**< Number of threads sleeping on this thread. */
-public:
-  kmp_basic_flag_native(volatile FlagType *p)
-      : kmp_flag_native<FlagType>(p, traits_type::t), num_waiting_threads(0) {}
-  kmp_basic_flag_native(volatile FlagType *p, kmp_info_t *thr)
-      : kmp_flag_native<FlagType>(p, traits_type::t), num_waiting_threads(1) {
-    waiting_threads[0] = thr;
-  }
-  kmp_basic_flag_native(volatile FlagType *p, FlagType c)
-      : kmp_flag_native<FlagType>(p, traits_type::t), checker(c),
-        num_waiting_threads(0) {}
-  /*!
-   * param i in   index into waiting_threads
-   * @result the thread that is waiting at index i
-   */
-  kmp_info_t *get_waiter(kmp_uint32 i) {
-    KMP_DEBUG_ASSERT(i < num_waiting_threads);
-    return waiting_threads[i];
-  }
-  /*!
-   * @result num_waiting_threads
-   */
-  kmp_uint32 get_num_waiters() { return num_waiting_threads; }
-  /*!
-   * @param thr in   the thread which is now waiting
-   *
-   * Insert a waiting thread at index 0.
-   */
-  void set_waiter(kmp_info_t *thr) {
-    waiting_threads[0] = thr;
-    num_waiting_threads = 1;
-  }
-  /*!
-   * @result true if the flag object has been released.
-   */
-  bool done_check() {
-    if (Sleepable)
-      return (traits_type::tcr(*(this->get())) & ~KMP_BARRIER_SLEEP_STATE) ==
-             checker;
-    else
-      return traits_type::tcr(*(this->get())) == checker;
-  }
-  /*!
-   * @param old_loc in   old value of flag
-   * @result true if the flag's old value indicates it was released.
-   */
-  bool done_check_val(FlagType old_loc) { return old_loc == checker; }
-  /*!
-   * @result true if the flag object is not yet released.
-   * Used in __kmp_wait_template like:
-   * @code
-   * while (flag.notdone_check()) { pause(); }
-   * @endcode
-   */
-  bool notdone_check() { return traits_type::tcr(*(this->get())) != checker; }
-  /*!
-   * @result Actual flag value before release was applied.
-   * Trigger all waiting threads to run by modifying flag to release state.
-   */
-  void internal_release() {
-    (void)traits_type::test_then_add4((volatile FlagType *)this->get());
-  }
-  /*!
-   * @result Actual flag value before sleep bit(s) set.
-   * Notes that there is at least one thread sleeping on the flag by setting
-   * sleep bit(s).
-   */
-  FlagType set_sleeping() {
-    return traits_type::test_then_or((volatile FlagType *)this->get(),
-                                     KMP_BARRIER_SLEEP_STATE);
-  }
-  /*!
-   * @result Actual flag value before sleep bit(s) cleared.
-   * Notes that there are no longer threads sleeping on the flag by clearing
-   * sleep bit(s).
-   */
-  FlagType unset_sleeping() {
-    return traits_type::test_then_and((volatile FlagType *)this->get(),
-                                      ~KMP_BARRIER_SLEEP_STATE);
-  }
-  /*!
-   * @param old_loc in   old value of flag
-   * Test whether there are threads sleeping on the flag's old value in old_loc.
-   */
-  bool is_sleeping_val(FlagType old_loc) {
-    return old_loc & KMP_BARRIER_SLEEP_STATE;
-  }
-  /*!
-   * Test whether there are threads sleeping on the flag.
-   */
-  bool is_sleeping() { return is_sleeping_val(*(this->get())); }
-  bool is_any_sleeping() { return is_sleeping_val(*(this->get())); }
-  kmp_uint8 *get_stolen() { return NULL; }
-  enum barrier_type get_bt() { return bs_last_barrier; }
-};
-
-template <typename FlagType, bool Sleepable>
-class kmp_basic_flag : public kmp_flag<FlagType> {
-  typedef flag_traits<FlagType> traits_type;
-  FlagType checker; /**< Value to compare flag to to check if flag has been
-                       released. */
-  kmp_info_t
-      *waiting_threads[1]; /**< Array of threads sleeping on this thread. */
-  kmp_uint32
-      num_waiting_threads; /**< Number of threads sleeping on this thread. */
-public:
-  kmp_basic_flag(std::atomic<FlagType> *p)
-      : kmp_flag<FlagType>(p, traits_type::t), num_waiting_threads(0) {}
-  kmp_basic_flag(std::atomic<FlagType> *p, kmp_info_t *thr)
-      : kmp_flag<FlagType>(p, traits_type::t), num_waiting_threads(1) {
-    waiting_threads[0] = thr;
-  }
-  kmp_basic_flag(std::atomic<FlagType> *p, FlagType c)
-      : kmp_flag<FlagType>(p, traits_type::t), checker(c),
-        num_waiting_threads(0) {}
-  /*!
-   * param i in   index into waiting_threads
-   * @result the thread that is waiting at index i
-   */
-  kmp_info_t *get_waiter(kmp_uint32 i) {
-    KMP_DEBUG_ASSERT(i < num_waiting_threads);
-    return waiting_threads[i];
-  }
-  /*!
-   * @result num_waiting_threads
-   */
-  kmp_uint32 get_num_waiters() { return num_waiting_threads; }
-  /*!
-   * @param thr in   the thread which is now waiting
-   *
-   * Insert a waiting thread at index 0.
-   */
-  void set_waiter(kmp_info_t *thr) {
-    waiting_threads[0] = thr;
-    num_waiting_threads = 1;
-  }
-  /*!
-   * @result true if the flag object has been released.
-   */
-  bool done_check() {
-    if (Sleepable)
-      return (this->load() & ~KMP_BARRIER_SLEEP_STATE) == checker;
-    else
-      return this->load() == checker;
-  }
-  /*!
-   * @param old_loc in   old value of flag
-   * @result true if the flag's old value indicates it was released.
-   */
-  bool done_check_val(FlagType old_loc) { return old_loc == checker; }
-  /*!
-   * @result true if the flag object is not yet released.
-   * Used in __kmp_wait_template like:
-   * @code
-   * while (flag.notdone_check()) { pause(); }
-   * @endcode
-   */
-  bool notdone_check() { return this->load() != checker; }
-  /*!
-   * @result Actual flag value before release was applied.
-   * Trigger all waiting threads to run by modifying flag to release state.
-   */
-  void internal_release() { KMP_ATOMIC_ADD(this->get(), 4); }
-  /*!
-   * @result Actual flag value before sleep bit(s) set.
-   * Notes that there is at least one thread sleeping on the flag by setting
-   * sleep bit(s).
-   */
-  FlagType set_sleeping() {
-    return KMP_ATOMIC_OR(this->get(), KMP_BARRIER_SLEEP_STATE);
-  }
-  /*!
-   * @result Actual flag value before sleep bit(s) cleared.
-   * Notes that there are no longer threads sleeping on the flag by clearing
-   * sleep bit(s).
-   */
-  FlagType unset_sleeping() {
-    return KMP_ATOMIC_AND(this->get(), ~KMP_BARRIER_SLEEP_STATE);
-  }
-  /*!
-   * @param old_loc in   old value of flag
-   * Test whether there are threads sleeping on the flag's old value in old_loc.
-   */
-  bool is_sleeping_val(FlagType old_loc) {
-    return old_loc & KMP_BARRIER_SLEEP_STATE;
-  }
-  /*!
-   * Test whether there are threads sleeping on the flag.
-   */
-  bool is_sleeping() { return is_sleeping_val(this->load()); }
-  bool is_any_sleeping() { return is_sleeping_val(this->load()); }
-  kmp_uint8 *get_stolen() { return NULL; }
-  enum barrier_type get_bt() { return bs_last_barrier; }
-};
-
 template <bool Cancellable, bool Sleepable>
-class kmp_flag_32 : public kmp_basic_flag<kmp_uint32, Sleepable> {
+class kmp_flag_32 : public kmp_flag_atomic<kmp_uint32, flag32, Sleepable> {
 public:
   kmp_flag_32(std::atomic<kmp_uint32> *p)
-      : kmp_basic_flag<kmp_uint32, Sleepable>(p) {}
+      : kmp_flag_atomic<kmp_uint32, flag32, Sleepable>(p) {}
   kmp_flag_32(std::atomic<kmp_uint32> *p, kmp_info_t *thr)
-      : kmp_basic_flag<kmp_uint32, Sleepable>(p, thr) {}
+      : kmp_flag_atomic<kmp_uint32, flag32, Sleepable>(p, thr) {}
   kmp_flag_32(std::atomic<kmp_uint32> *p, kmp_uint32 c)
-      : kmp_basic_flag<kmp_uint32, Sleepable>(p, c) {}
+      : kmp_flag_atomic<kmp_uint32, flag32, Sleepable>(p, c) {}
   void suspend(int th_gtid) { __kmp_suspend_32(th_gtid, this); }
 #if KMP_HAVE_MWAIT || KMP_HAVE_UMWAIT
   void mwait(int th_gtid) { __kmp_mwait_32(th_gtid, this); }
 #endif
   void resume(int th_gtid) { __kmp_resume_32(th_gtid, this); }
   int execute_tasks(kmp_info_t *this_thr, kmp_int32 gtid, int final_spin,
                     int *thread_finished USE_ITT_BUILD_ARG(void *itt_sync_obj),
                     kmp_int32 is_constrained) {
else
       return __kmp_wait_template<kmp_flag_32, FALSE, Cancellable, Sleepable>(
           this_thr, this USE_ITT_BUILD_ARG(itt_sync_obj));
   }
   void release() { __kmp_release_template(this); }
   flag_type get_ptr_type() { return flag32; }
 };
 
 template <bool Cancellable, bool Sleepable>
-class kmp_flag_64 : public kmp_basic_flag_native<kmp_uint64, Sleepable> {
+class kmp_flag_64 : public kmp_flag_native<kmp_uint64, flag64, Sleepable> {
 public:
   kmp_flag_64(volatile kmp_uint64 *p)
-      : kmp_basic_flag_native<kmp_uint64, Sleepable>(p) {}
+      : kmp_flag_native<kmp_uint64, flag64, Sleepable>(p) {}
   kmp_flag_64(volatile kmp_uint64 *p, kmp_info_t *thr)
-      : kmp_basic_flag_native<kmp_uint64, Sleepable>(p, thr) {}
+      : kmp_flag_native<kmp_uint64, flag64, Sleepable>(p, thr) {}
   kmp_flag_64(volatile kmp_uint64 *p, kmp_uint64 c)
-      : kmp_basic_flag_native<kmp_uint64, Sleepable>(p, c) {}
+      : kmp_flag_native<kmp_uint64, flag64, Sleepable>(p, c) {}
+  kmp_flag_64(volatile kmp_uint64 *p, kmp_uint64 c, std::atomic<bool> *loc)
+      : kmp_flag_native<kmp_uint64, flag64, Sleepable>(p, c, loc) {}
   void suspend(int th_gtid) { __kmp_suspend_64(th_gtid, this); }
 #if KMP_HAVE_MWAIT || KMP_HAVE_UMWAIT
   void mwait(int th_gtid) { __kmp_mwait_64(th_gtid, this); }
 #endif
   void resume(int th_gtid) { __kmp_resume_64(th_gtid, this); }
   int execute_tasks(kmp_info_t *this_thr, kmp_int32 gtid, int final_spin,
                     int *thread_finished USE_ITT_BUILD_ARG(void *itt_sync_obj),
                     kmp_int32 is_constrained) {
bool wait(kmp_info_t *this_thr,
     else
       return __kmp_wait_template<kmp_flag_64, FALSE, Cancellable, Sleepable>(
           this_thr, this USE_ITT_BUILD_ARG(itt_sync_obj));
   }
   void release() { __kmp_release_template(this); }
   flag_type get_ptr_type() { return flag64; }
 };
 
+template <bool Cancellable, bool Sleepable>
+class kmp_atomic_flag_64
+    : public kmp_flag_atomic<kmp_uint64, atomic_flag64, Sleepable> {
+public:
+  kmp_atomic_flag_64(std::atomic<kmp_uint64> *p)
+      : kmp_flag_atomic<kmp_uint64, atomic_flag64, Sleepable>(p) {}
+  kmp_atomic_flag_64(std::atomic<kmp_uint64> *p, kmp_info_t *thr)
+      : kmp_flag_atomic<kmp_uint64, atomic_flag64, Sleepable>(p, thr) {}
+  kmp_atomic_flag_64(std::atomic<kmp_uint64> *p, kmp_uint64 c)
+      : kmp_flag_atomic<kmp_uint64, atomic_flag64, Sleepable>(p, c) {}
+  kmp_atomic_flag_64(std::atomic<kmp_uint64> *p, kmp_uint64 c,
+                     std::atomic<bool> *loc)
+      : kmp_flag_atomic<kmp_uint64, atomic_flag64, Sleepable>(p, c, loc) {}
+  void suspend(int th_gtid) { __kmp_atomic_suspend_64(th_gtid, this); }
+  void mwait(int th_gtid) { __kmp_atomic_mwait_64(th_gtid, this); }
+  void resume(int th_gtid) { __kmp_atomic_resume_64(th_gtid, this); }
+  int execute_tasks(kmp_info_t *this_thr, kmp_int32 gtid, int final_spin,
+                    int *thread_finished USE_ITT_BUILD_ARG(void *itt_sync_obj),
+                    kmp_int32 is_constrained) {
+    return __kmp_atomic_execute_tasks_64(
+        this_thr, gtid, this, final_spin,
+        thread_finished USE_ITT_BUILD_ARG(itt_sync_obj), is_constrained);
+  }
+  bool wait(kmp_info_t *this_thr,
+            int final_spin USE_ITT_BUILD_ARG(void *itt_sync_obj)) {
+    if (final_spin)
+      return __kmp_wait_template<kmp_atomic_flag_64, TRUE, Cancellable,
+                                 Sleepable>(
+          this_thr, this USE_ITT_BUILD_ARG(itt_sync_obj));
+    else
+      return __kmp_wait_template<kmp_atomic_flag_64, FALSE, Cancellable,
+                                 Sleepable>(
+          this_thr, this USE_ITT_BUILD_ARG(itt_sync_obj));
+  }
+  void release() { __kmp_release_template(this); }
+  flag_type get_ptr_type() { return atomic_flag64; }
+};
+
 // Hierarchical 64-bit on-core barrier instantiation
-class kmp_flag_oncore : public kmp_flag_native<kmp_uint64> {
-  kmp_uint64 checker;
-  kmp_info_t *waiting_threads[1];
-  kmp_uint32 num_waiting_threads;
-  kmp_uint32
-      offset; /**< Portion of flag that is of interest for an operation. */
+class kmp_flag_oncore : public kmp_flag_native<kmp_uint64, flag_oncore, false> {
+  kmp_uint32 offset; /**< Portion of flag of interest for an operation. */
   bool flag_switch; /**< Indicates a switch in flag location. */
   enum barrier_type bt; /**< Barrier type. */
-  kmp_info_t *this_thr; /**< Thread that may be redirected to different flag
-                           location. */
+  kmp_info_t *this_thr; /**< Thread to redirect to different flag location. */
 #if USE_ITT_BUILD
-  void *
-      itt_sync_obj; /**< ITT object that must be passed to new flag location. */
+  void *itt_sync_obj; /**< ITT object to pass to new flag location. */
 #endif
   unsigned char &byteref(volatile kmp_uint64 *loc, size_t offset) {
     return (RCAST(unsigned char *, CCAST(kmp_uint64 *, loc)))[offset];
   }
 
 public:
   kmp_flag_oncore(volatile kmp_uint64 *p)
-      : kmp_flag_native<kmp_uint64>(p, flag_oncore), num_waiting_threads(0),
-        flag_switch(false) {}
+      : kmp_flag_native<kmp_uint64, flag_oncore, false>(p), flag_switch(false) {
+  }
   kmp_flag_oncore(volatile kmp_uint64 *p, kmp_uint32 idx)
-      : kmp_flag_native<kmp_uint64>(p, flag_oncore), num_waiting_threads(0),
-        offset(idx), flag_switch(false) {}
+      : kmp_flag_native<kmp_uint64, flag_oncore, false>(p), offset(idx),
+        flag_switch(false),
+        bt(bs_last_barrier) USE_ITT_BUILD_ARG(itt_sync_obj(nullptr)) {}
   kmp_flag_oncore(volatile kmp_uint64 *p, kmp_uint64 c, kmp_uint32 idx,
                   enum barrier_type bar_t,
                   kmp_info_t *thr USE_ITT_BUILD_ARG(void *itt))
-      : kmp_flag_native<kmp_uint64>(p, flag_oncore), checker(c),
-        num_waiting_threads(0), offset(idx), flag_switch(false), bt(bar_t),
+      : kmp_flag_native<kmp_uint64, flag_oncore, false>(p, c), offset(idx),
+        flag_switch(false), bt(bar_t),
         this_thr(thr) USE_ITT_BUILD_ARG(itt_sync_obj(itt)) {}
-  kmp_info_t *get_waiter(kmp_uint32 i) {
-    KMP_DEBUG_ASSERT(i < num_waiting_threads);
-    return waiting_threads[i];
-  }
-  kmp_uint32 get_num_waiters() { return num_waiting_threads; }
-  void set_waiter(kmp_info_t *thr) {
-    waiting_threads[0] = thr;
-    num_waiting_threads = 1;
-  }
-  bool done_check_val(kmp_uint64 old_loc) {
+  virtual ~kmp_flag_oncore() override {}
+  void *operator new(size_t size) { return __kmp_allocate(size); }
+  void operator delete(void *p) { __kmp_free(p); }
+  bool done_check_val(kmp_uint64 old_loc) override {
     return byteref(&old_loc, offset) == checker;
   }
-  bool done_check() { return done_check_val(*get()); }
-  bool notdone_check() {
+  bool done_check() override { return done_check_val(*get()); }
+  bool notdone_check() override {
     // Calculate flag_switch
     if (this_thr->th.th_bar[bt].bb.wait_flag == KMP_BARRIER_SWITCH_TO_OWN_FLAG)
       flag_switch = true;
     if (byteref(get(), offset) != 1 && !flag_switch)
       return true;
     else if (flag_switch) {
       this_thr->th.th_bar[bt].bb.wait_flag = KMP_BARRIER_SWITCHING;
       kmp_flag_64<> flag(&this_thr->th.th_bar[bt].bb.b_go,
                          (kmp_uint64)KMP_BARRIER_STATE_BUMP);
       __kmp_wait_64(this_thr, &flag, TRUE USE_ITT_BUILD_ARG(itt_sync_obj));
     }
     return false;
   }
   void internal_release() {
     // Other threads can write their own bytes simultaneously.
     if (__kmp_dflt_blocktime == KMP_MAX_BLOCKTIME) {
       byteref(get(), offset) = 1;
     } else {
       kmp_uint64 mask = 0;
       byteref(&mask, offset) = 1;
       KMP_TEST_THEN_OR64(get(), mask);
     }
   }
-  kmp_uint64 set_sleeping() {
-    return KMP_TEST_THEN_OR64(get(), KMP_BARRIER_SLEEP_STATE);
-  }
-  kmp_uint64 unset_sleeping() {
-    return KMP_TEST_THEN_AND64(get(), ~KMP_BARRIER_SLEEP_STATE);
-  }
-  bool is_sleeping_val(kmp_uint64 old_loc) {
-    return old_loc & KMP_BARRIER_SLEEP_STATE;
-  }
-  bool is_sleeping() { return is_sleeping_val(*get()); }
-  bool is_any_sleeping() { return is_sleeping_val(*get()); }
   void wait(kmp_info_t *this_thr, int final_spin) {
     if (final_spin)
       __kmp_wait_template<kmp_flag_oncore, TRUE>(
           this_thr, this USE_ITT_BUILD_ARG(itt_sync_obj));
     else
       __kmp_wait_template<kmp_flag_oncore, FALSE>(
           this_thr, this USE_ITT_BUILD_ARG(itt_sync_obj));
   }
if (ompd_state & OMPD_ENABLE_BP)
       ompd_bp_task_end();
     return ret;
 #else
     return __kmp_execute_tasks_oncore(
         this_thr, gtid, this, final_spin,
         thread_finished USE_ITT_BUILD_ARG(itt_sync_obj), is_constrained);
 #endif
   }
-  kmp_uint8 *get_stolen() { return NULL; }
   enum barrier_type get_bt() { return bt; }
   flag_type get_ptr_type() { return flag_oncore; }
 };
 
-// Used to wake up threads, volatile void* flag is usually the th_sleep_loc
-// associated with int gtid.
-static inline void __kmp_null_resume_wrapper(int gtid, volatile void *flag) {
+static inline void __kmp_null_resume_wrapper(kmp_info_t *thr) {
+  int gtid = __kmp_gtid_from_thread(thr);
+  void *flag = CCAST(void *, thr->th.th_sleep_loc);
+  flag_type type = thr->th.th_sleep_loc_type;
   if (!flag)
     return;
-
-  switch (RCAST(kmp_flag_64<> *, CCAST(void *, flag))->get_type()) {
+  // Attempt to wake up a thread: examine its type and call appropriate template
+  switch (type) {
   case flag32:
-    __kmp_resume_32(gtid, (kmp_flag_32<> *)NULL);
+    __kmp_resume_32(gtid, RCAST(kmp_flag_32<> *, flag));
     break;
   case flag64:
-    __kmp_resume_64(gtid, (kmp_flag_64<> *)NULL);
+    __kmp_resume_64(gtid, RCAST(kmp_flag_64<> *, flag));
+    break;
+  case atomic_flag64:
+    __kmp_atomic_resume_64(gtid, RCAST(kmp_atomic_flag_64<> *, flag));
     break;
   case flag_oncore:
-    __kmp_resume_oncore(gtid, (kmp_flag_oncore *)NULL);
+    __kmp_resume_oncore(gtid, RCAST(kmp_flag_oncore *, flag));
     break;
+#ifdef KMP_DEBUG
+  case flag_unset:
+    KF_TRACE(100, ("__kmp_null_resume_wrapper: flag type %d is unset\n", type));
+    break;
+  default:
+    KF_TRACE(100, ("__kmp_null_resume_wrapper: flag type %d does not match any "
+                   "known flag type\n",
+                   type));
+#endif
   }
 }
 
 /*!
 @}
 */
 
 #endif // KMP_WAIT_RELEASE_H

openmp/runtime/src/kmp_wait_release.cpp

 template <bool C, bool S>
 void __kmp_mwait_32(int th_gtid, kmp_flag_32<C, S> *flag) {
   __kmp_mwait_template(th_gtid, flag);
 }
 template <bool C, bool S>
 void __kmp_mwait_64(int th_gtid, kmp_flag_64<C, S> *flag) {
   __kmp_mwait_template(th_gtid, flag);
 }
+template <bool C, bool S>
+void __kmp_atomic_mwait_64(int th_gtid, kmp_atomic_flag_64<C, S> *flag) {
+  __kmp_mwait_template(th_gtid, flag);
+}
 void __kmp_mwait_oncore(int th_gtid, kmp_flag_oncore *flag) {
   __kmp_mwait_template(th_gtid, flag);
 }
 
 template void __kmp_mwait_32<false, false>(int, kmp_flag_32<false, false> *);
 template void __kmp_mwait_64<false, true>(int, kmp_flag_64<false, true> *);
 template void __kmp_mwait_64<true, false>(int, kmp_flag_64<true, false> *);
+template void
+__kmp_atomic_mwait_64<false, true>(int, kmp_atomic_flag_64<false, true> *);
+template void
+__kmp_atomic_mwait_64<true, false>(int, kmp_atomic_flag_64<true, false> *);
 #endif

openmp/runtime/src/z_Linux_util.cpp

static inline void __kmp_suspend_template(int th_gtid, C *flag) {
   __kmp_lock_suspend_mx(th);
 
   KF_TRACE(10, ("__kmp_suspend_template: T#%d setting sleep bit for spin(%p)\n",
                 th_gtid, flag->get()));
 
   /* TODO: shouldn't this use release semantics to ensure that
      __kmp_suspend_initialize_thread gets called first? */
   old_spin = flag->set_sleeping();
+  TCW_PTR(th->th.th_sleep_loc, (void *)flag);
+  th->th.th_sleep_loc_type = flag->get_type();
   if (__kmp_dflt_blocktime == KMP_MAX_BLOCKTIME &&
       __kmp_pause_status != kmp_soft_paused) {
     flag->unset_sleeping();
+    TCW_PTR(th->th.th_sleep_loc, NULL);
+    th->th.th_sleep_loc_type = flag_unset;
     __kmp_unlock_suspend_mx(th);
     return;
   }
   KF_TRACE(5, ("__kmp_suspend_template: T#%d set sleep bit for spin(%p)==%x,"
                " was %x\n",
                th_gtid, flag->get(), flag->load(), old_spin));
 
-  if (flag->done_check_val(old_spin)) {
-    old_spin = flag->unset_sleeping();
+  if (flag->done_check_val(old_spin) || flag->done_check()) {
+    flag->unset_sleeping();
+    TCW_PTR(th->th.th_sleep_loc, NULL);
+    th->th.th_sleep_loc_type = flag_unset;
     KF_TRACE(5, ("__kmp_suspend_template: T#%d false alarm, reset sleep bit "
                  "for spin(%p)\n",
                  th_gtid, flag->get()));
   } else {
     /* Encapsulate in a loop as the documentation states that this may
        "with low probability" return when the condition variable has
        not been signaled or broadcast */
     int deactivated = FALSE;
-    TCW_PTR(th->th.th_sleep_loc, (void *)flag);
 
     while (flag->is_sleeping()) {
 #ifdef DEBUG_SUSPEND
       char buffer[128];
       __kmp_suspend_count++;
       __kmp_print_cond(buffer, &th->th.th_suspend_cv);
       __kmp_printf("__kmp_suspend_template: suspending T#%d: %s\n", th_gtid,
                    buffer);
 #endif
       // Mark the thread as no longer active (only in the first iteration of the
       // loop).
       if (!deactivated) {
         th->th.th_active = FALSE;
         if (th->th.th_active_in_pool) {
           th->th.th_active_in_pool = FALSE;
           KMP_ATOMIC_DEC(&__kmp_thread_pool_active_nth);
           KMP_DEBUG_ASSERT(TCR_4(__kmp_thread_pool_active_nth) >= 0);
         }
         deactivated = TRUE;
       }
 
+      KMP_DEBUG_ASSERT(th->th.th_sleep_loc);
+      KMP_DEBUG_ASSERT(flag->get_type() == th->th.th_sleep_loc_type);
+
 #if USE_SUSPEND_TIMEOUT
       struct timespec now;
       struct timeval tval;
       int msecs;
 
       status = gettimeofday(&tval, NULL);
       KMP_CHECK_SYSFAIL_ERRNO("gettimeofday", status);
       TIMEVAL_TO_TIMESPEC(&tval, &now);
#else
                     th_gtid));
       status = pthread_cond_wait(&th->th.th_suspend_cv.c_cond,
                                  &th->th.th_suspend_mx.m_mutex);
 #endif // USE_SUSPEND_TIMEOUT
 
       if ((status != 0) && (status != EINTR) && (status != ETIMEDOUT)) {
         KMP_SYSFAIL("pthread_cond_wait", status);
       }
+
+      KMP_DEBUG_ASSERT(flag->get_type() == flag->get_ptr_type());
+
+      if (!flag->is_sleeping() &&
+          ((status == EINTR) || (status == ETIMEDOUT))) {
+        // if interrupt or timeout, and thread is no longer sleeping, we need to
+        // make sure sleep_loc gets reset; however, this shouldn't be needed if
+        // we woke up with resume
+        flag->unset_sleeping();
+        TCW_PTR(th->th.th_sleep_loc, NULL);
+        th->th.th_sleep_loc_type = flag_unset;
+      }
 #ifdef KMP_DEBUG
       if (status == ETIMEDOUT) {
         if (flag->is_sleeping()) {
           KF_TRACE(100,
                    ("__kmp_suspend_template: T#%d timeout wakeup\n", th_gtid));
         } else {
           KF_TRACE(2, ("__kmp_suspend_template: T#%d timeout wakeup, sleep bit "
                        "not set!\n",
                        th_gtid));
+          TCW_PTR(th->th.th_sleep_loc, NULL);
+          th->th.th_sleep_loc_type = flag_unset;
         }
       } else if (flag->is_sleeping()) {
         KF_TRACE(100,
                  ("__kmp_suspend_template: T#%d spurious wakeup\n", th_gtid));
       }
 #endif
     } // while
 
     // Mark the thread as active again (if it was previous marked as inactive)
     if (deactivated) {
       th->th.th_active = TRUE;
       if (TCR_4(th->th.th_in_pool)) {
         KMP_ATOMIC_INC(&__kmp_thread_pool_active_nth);
         th->th.th_active_in_pool = TRUE;
       }
     }
   }
+  // We may have had the loop variable set before entering the loop body;
+  // so we need to reset sleep_loc.
+  TCW_PTR(th->th.th_sleep_loc, NULL);
+  th->th.th_sleep_loc_type = flag_unset;
+
+  KMP_DEBUG_ASSERT(!flag->is_sleeping());
+  KMP_DEBUG_ASSERT(!th->th.th_sleep_loc);
 #ifdef DEBUG_SUSPEND
   {
     char buffer[128];
     __kmp_print_cond(buffer, &th->th.th_suspend_cv);
     __kmp_printf("__kmp_suspend_template: T#%d has awakened: %s\n", th_gtid,
                  buffer);
   }
 #endif
 
   __kmp_unlock_suspend_mx(th);
   KF_TRACE(30, ("__kmp_suspend_template: T#%d exit\n", th_gtid));
 }
 
 template <bool C, bool S>
 void __kmp_suspend_32(int th_gtid, kmp_flag_32<C, S> *flag) {
   __kmp_suspend_template(th_gtid, flag);
 }
 template <bool C, bool S>
 void __kmp_suspend_64(int th_gtid, kmp_flag_64<C, S> *flag) {
   __kmp_suspend_template(th_gtid, flag);
 }
+template <bool C, bool S>
+void __kmp_atomic_suspend_64(int th_gtid, kmp_atomic_flag_64<C, S> *flag) {
+  __kmp_suspend_template(th_gtid, flag);
+}
 void __kmp_suspend_oncore(int th_gtid, kmp_flag_oncore *flag) {
   __kmp_suspend_template(th_gtid, flag);
 }
 
 template void __kmp_suspend_32<false, false>(int, kmp_flag_32<false, false> *);
 template void __kmp_suspend_64<false, true>(int, kmp_flag_64<false, true> *);
 template void __kmp_suspend_64<true, false>(int, kmp_flag_64<true, false> *);
+template void
+__kmp_atomic_suspend_64<false, true>(int, kmp_atomic_flag_64<false, true> *);
+template void
+__kmp_atomic_suspend_64<true, false>(int, kmp_atomic_flag_64<true, false> *);
 
 /* This routine signals the thread specified by target_gtid to wake up
    after setting the sleep bit indicated by the flag argument to FALSE.
    The target thread must already have called __kmp_suspend_template() */
 template <class C>
 static inline void __kmp_resume_template(int target_gtid, C *flag) {
   KMP_TIME_DEVELOPER_PARTITIONED_BLOCK(USER_resume);
   kmp_info_t *th = __kmp_threads[target_gtid];
   int status;
 
 #ifdef KMP_DEBUG
   int gtid = TCR_4(__kmp_init_gtid) ? __kmp_get_gtid() : -1;
 #endif
 
   KF_TRACE(30, ("__kmp_resume_template: T#%d wants to wakeup T#%d enter\n",
                 gtid, target_gtid));
   KMP_DEBUG_ASSERT(gtid != target_gtid);
 
   __kmp_suspend_initialize_thread(th);
 
   __kmp_lock_suspend_mx(th);
 
-  if (!flag) { // coming from __kmp_null_resume_wrapper
+  if (!flag || flag != th->th.th_sleep_loc) {
+    // coming from __kmp_null_resume_wrapper, or thread is now sleeping on a
+    // different location; wake up at new location
     flag = (C *)CCAST(void *, th->th.th_sleep_loc);
   }
 
   // First, check if the flag is null or its type has changed. If so, someone
   // else woke it up.
-  if (!flag || flag->get_type() != flag->get_ptr_type()) { // get_ptr_type
-    // simply shows what flag was cast to
+  if (!flag) { // Thread doesn't appear to be sleeping on anything
     KF_TRACE(5, ("__kmp_resume_template: T#%d exiting, thread T#%d already "
                  "awake: flag(%p)\n",
-                 gtid, target_gtid, NULL));
+                 gtid, target_gtid, (void *)NULL));
     __kmp_unlock_suspend_mx(th);
     return;
+  } else if (flag->get_type() != th->th.th_sleep_loc_type) {
+    // Flag type does not appear to match this function template; possibly the
+    // thread is sleeping on something else. Try null resume again.
+    KF_TRACE(
+        5,
+        ("__kmp_resume_template: T#%d retrying, thread T#%d Mismatch flag(%p), "
+         "spin(%p) type=%d ptr_type=%d\n",
+         gtid, target_gtid, flag, flag->get(), flag->get_type(),
+         th->th.th_sleep_loc_type));
+    __kmp_unlock_suspend_mx(th);
+    __kmp_null_resume_wrapper(th);
+    return;
   } else { // if multiple threads are sleeping, flag should be internally
     // referring to a specific thread here
-    typename C::flag_t old_spin = flag->unset_sleeping();
-    if (!flag->is_sleeping_val(old_spin)) {
+    if (!flag->is_sleeping()) {
       KF_TRACE(5, ("__kmp_resume_template: T#%d exiting, thread T#%d already "
-                   "awake: flag(%p): "
-                   "%u => %u\n",
-                   gtid, target_gtid, flag->get(), old_spin, flag->load()));
+                   "awake: flag(%p): %u\n",
+                   gtid, target_gtid, flag->get(), (unsigned int)flag->load()));
       __kmp_unlock_suspend_mx(th);
       return;
     }
-    KF_TRACE(5, ("__kmp_resume_template: T#%d about to wakeup T#%d, reset "
-                 "sleep bit for flag's loc(%p): "
-                 "%u => %u\n",
-                 gtid, target_gtid, flag->get(), old_spin, flag->load()));
   }
+  KMP_DEBUG_ASSERT(flag);
+  flag->unset_sleeping();
   TCW_PTR(th->th.th_sleep_loc, NULL);
+  th->th.th_sleep_loc_type = flag_unset;
+
+  KF_TRACE(5, ("__kmp_resume_template: T#%d about to wakeup T#%d, reset "
+               "sleep bit for flag's loc(%p): %u\n",
+               gtid, target_gtid, flag->get(), (unsigned int)flag->load()));
 
 #ifdef DEBUG_SUSPEND
   {
     char buffer[128];
     __kmp_print_cond(buffer, &th->th.th_suspend_cv);
     __kmp_printf("__kmp_resume_template: T#%d resuming T#%d: %s\n", gtid,
                  target_gtid, buffer);
   }

 template <bool C, bool S>
 void __kmp_resume_32(int target_gtid, kmp_flag_32<C, S> *flag) {
   __kmp_resume_template(target_gtid, flag);
 }
 template <bool C, bool S>
 void __kmp_resume_64(int target_gtid, kmp_flag_64<C, S> *flag) {
   __kmp_resume_template(target_gtid, flag);
 }
+template <bool C, bool S>
+void __kmp_atomic_resume_64(int target_gtid, kmp_atomic_flag_64<C, S> *flag) {
+  __kmp_resume_template(target_gtid, flag);
+}
 void __kmp_resume_oncore(int target_gtid, kmp_flag_oncore *flag) {
   __kmp_resume_template(target_gtid, flag);
 }
 
 template void __kmp_resume_32<false, true>(int, kmp_flag_32<false, true> *);
+template void __kmp_resume_32<false, false>(int, kmp_flag_32<false, false> *);
 template void __kmp_resume_64<false, true>(int, kmp_flag_64<false, true> *);
+template void
+__kmp_atomic_resume_64<false, true>(int, kmp_atomic_flag_64<false, true> *);
 
 #if KMP_USE_MONITOR
 void __kmp_resume_monitor() {
   KMP_TIME_DEVELOPER_PARTITIONED_BLOCK(USER_resume);
   int status;
 #ifdef KMP_DEBUG
   int gtid = TCR_4(__kmp_init_gtid) ? __kmp_get_gtid() : -1;
   KF_TRACE(30, ("__kmp_resume_monitor: T#%d wants to wakeup T#%d enter\n", gtid,

openmp/runtime/src/z_Windows_NT_util.cpp

if (res == WAIT_OBJECT_0) {
       // as MS sent us debug dump whith inconsistent state of data
       __kmp_win32_mutex_lock(mx);
       typename C::flag_t old_f = flag->set_sleeping();
       if (!flag->done_check_val(old_f & ~KMP_BARRIER_SLEEP_STATE)) {
         __kmp_win32_mutex_unlock(mx);
         continue;
       }
       // condition fulfilled, exiting
-      old_f = flag->unset_sleeping();
-      KMP_DEBUG_ASSERT(old_f & KMP_BARRIER_SLEEP_STATE);
+      flag->unset_sleeping();
       TCW_PTR(th->th.th_sleep_loc, NULL);
-      KF_TRACE(50,
-               ("__kmp_win32_cond_wait: exiting, condition "
-                "fulfilled: flag's loc(%p): %u => %u\n",
-                flag->get(), (unsigned int)old_f, (unsigned int)flag->load()));
+      th->th.th_sleep_loc_type = flag_unset;
+      KF_TRACE(50, ("__kmp_win32_cond_wait: exiting, condition "
+                    "fulfilled: flag's loc(%p): %u\n",
+                    flag->get(), (unsigned int)flag->load()));
 
       __kmp_win32_mutex_lock(&cv->waiters_count_lock_);
       KMP_DEBUG_ASSERT(cv->waiters_count_ > 0);
       cv->release_count_ = cv->waiters_count_;
       cv->wait_generation_count_++;
       wait_done = 1;
       __kmp_win32_mutex_unlock(&cv->waiters_count_lock_);
 
static inline void __kmp_suspend_template(int th_gtid, C *flag) {
 
   KF_TRACE(10, ("__kmp_suspend_template: T#%d setting sleep bit for flag's"
                 " loc(%p)\n",
                 th_gtid, flag->get()));
 
   /* TODO: shouldn't this use release semantics to ensure that
      __kmp_suspend_initialize_thread gets called first? */
   old_spin = flag->set_sleeping();
+  TCW_PTR(th->th.th_sleep_loc, (void *)flag);
+  th->th.th_sleep_loc_type = flag->get_type();
   if (__kmp_dflt_blocktime == KMP_MAX_BLOCKTIME &&
       __kmp_pause_status != kmp_soft_paused) {
     flag->unset_sleeping();
+    TCW_PTR(th->th.th_sleep_loc, NULL);
+    th->th.th_sleep_loc_type = flag_unset;
     __kmp_unlock_suspend_mx(th);
     return;
   }
 
   KF_TRACE(5, ("__kmp_suspend_template: T#%d set sleep bit for flag's"
                " loc(%p)==%u\n",
                th_gtid, flag->get(), (unsigned int)flag->load()));
 
-  if (flag->done_check_val(old_spin)) {
-    old_spin = flag->unset_sleeping();
+  if (flag->done_check_val(old_spin) || flag->done_check()) {
+    flag->unset_sleeping();
+    TCW_PTR(th->th.th_sleep_loc, NULL);
+    th->th.th_sleep_loc_type = flag_unset;
     KF_TRACE(5, ("__kmp_suspend_template: T#%d false alarm, reset sleep bit "
                  "for flag's loc(%p)\n",
                  th_gtid, flag->get()));
   } else {
 #ifdef DEBUG_SUSPEND
     __kmp_suspend_count++;
 #endif
     /* Encapsulate in a loop as the documentation states that this may "with
        low probability" return when the condition variable has not been signaled
        or broadcast */
     int deactivated = FALSE;
-    TCW_PTR(th->th.th_sleep_loc, (void *)flag);
+
     while (flag->is_sleeping()) {
       KF_TRACE(15, ("__kmp_suspend_template: T#%d about to perform "
                     "kmp_win32_cond_wait()\n",
                     th_gtid));
       // Mark the thread as no longer active (only in the first iteration of the
       // loop).
       if (!deactivated) {
         th->th.th_active = FALSE;
         if (th->th.th_active_in_pool) {
           th->th.th_active_in_pool = FALSE;
           KMP_ATOMIC_DEC(&__kmp_thread_pool_active_nth);
           KMP_DEBUG_ASSERT(TCR_4(__kmp_thread_pool_active_nth) >= 0);
         }
         deactivated = TRUE;
-        __kmp_win32_cond_wait(&th->th.th_suspend_cv, &th->th.th_suspend_mx, th,
-                              flag);
-      } else {
-        __kmp_win32_cond_wait(&th->th.th_suspend_cv, &th->th.th_suspend_mx, th,
-                              flag);
-      }
+      }
+
+      KMP_DEBUG_ASSERT(th->th.th_sleep_loc);
+      KMP_DEBUG_ASSERT(th->th.th_sleep_loc_type == flag->get_type());
+
 
 #ifdef KMP_DEBUG
       if (flag->is_sleeping()) {
         KF_TRACE(100,
                  ("__kmp_suspend_template: T#%d spurious wakeup\n", th_gtid));
       }
 #endif /* KMP_DEBUG */
 
     } // while
 
+    // We may have had the loop variable set before entering the loop body;
+    // so we need to reset sleep_loc.
+    TCW_PTR(th->th.th_sleep_loc, NULL);
+    th->th.th_sleep_loc_type = flag_unset;
+
+    KMP_DEBUG_ASSERT(!flag->is_sleeping());
+    KMP_DEBUG_ASSERT(!th->th.th_sleep_loc);
+
     // Mark the thread as active again (if it was previous marked as inactive)
     if (deactivated) {
       th->th.th_active = TRUE;
       if (TCR_4(th->th.th_in_pool)) {
         KMP_ATOMIC_INC(&__kmp_thread_pool_active_nth);
         th->th.th_active_in_pool = TRUE;
       }
     }
   }
 
   __kmp_unlock_suspend_mx(th);
   KF_TRACE(30, ("__kmp_suspend_template: T#%d exit\n", th_gtid));
 }
 
 template <bool C, bool S>
 void __kmp_suspend_32(int th_gtid, kmp_flag_32<C, S> *flag) {
   __kmp_suspend_template(th_gtid, flag);
 }
 template <bool C, bool S>
 void __kmp_suspend_64(int th_gtid, kmp_flag_64<C, S> *flag) {
   __kmp_suspend_template(th_gtid, flag);
 }
+template <bool C, bool S>
+void __kmp_atomic_suspend_64(int th_gtid, kmp_atomic_flag_64<C, S> *flag) {
+  __kmp_suspend_template(th_gtid, flag);
+}
 void __kmp_suspend_oncore(int th_gtid, kmp_flag_oncore *flag) {
   __kmp_suspend_template(th_gtid, flag);
 }
 
 template void __kmp_suspend_32<false, false>(int, kmp_flag_32<false, false> *);
 template void __kmp_suspend_64<false, true>(int, kmp_flag_64<false, true> *);
 template void __kmp_suspend_64<true, false>(int, kmp_flag_64<true, false> *);
+template void
+__kmp_atomic_suspend_64<false, true>(int, kmp_atomic_flag_64<false, true> *);
+template void
+__kmp_atomic_suspend_64<true, false>(int, kmp_atomic_flag_64<true, false> *);
 
 /* This routine signals the thread specified by target_gtid to wake up
    after setting the sleep bit indicated by the flag argument to FALSE */
 template <class C>
 static inline void __kmp_resume_template(int target_gtid, C *flag) {
   kmp_info_t *th = __kmp_threads[target_gtid];
 
 #ifdef KMP_DEBUG
   int gtid = TCR_4(__kmp_init_gtid) ? __kmp_get_gtid() : -1;
 #endif
 
   KF_TRACE(30, ("__kmp_resume_template: T#%d wants to wakeup T#%d enter\n",
                 gtid, target_gtid));
 
   __kmp_suspend_initialize_thread(th);
   __kmp_lock_suspend_mx(th);
 
-  if (!flag) { // coming from __kmp_null_resume_wrapper
+  if (!flag || flag != th->th.th_sleep_loc) {
+    // coming from __kmp_null_resume_wrapper, or thread is now sleeping on a
+    // different location; wake up at new location
     flag = (C *)th->th.th_sleep_loc;
   }
 
   // First, check if the flag is null or its type has changed. If so, someone
   // else woke it up.
-  if (!flag || flag->get_type() != flag->get_ptr_type()) { // get_ptr_type
-    // simply shows what
-    // flag was cast to
+  if (!flag || flag->get_type() != th->th.th_sleep_loc_type) {
+    // simply shows what flag was cast to
     KF_TRACE(5, ("__kmp_resume_template: T#%d exiting, thread T#%d already "
                  "awake: flag's loc(%p)\n",
                  gtid, target_gtid, NULL));
     __kmp_unlock_suspend_mx(th);
     return;
   } else {
-    typename C::flag_t old_spin = flag->unset_sleeping();
-    if (!flag->is_sleeping_val(old_spin)) {
+    if (!flag->is_sleeping()) {
       KF_TRACE(5, ("__kmp_resume_template: T#%d exiting, thread T#%d already "
-                   "awake: flag's loc(%p): %u => %u\n",
-                   gtid, target_gtid, flag->get(), (unsigned int)old_spin,
-                   (unsigned int)flag->load()));
+                   "awake: flag's loc(%p): %u\n",
+                   gtid, target_gtid, flag->get(), (unsigned int)flag->load()));
       __kmp_unlock_suspend_mx(th);
       return;
     }
   }
+  KMP_DEBUG_ASSERT(flag);
+  flag->unset_sleeping();
   TCW_PTR(th->th.th_sleep_loc, NULL);
+  th->th.th_sleep_loc_type = flag_unset;
+
   KF_TRACE(5, ("__kmp_resume_template: T#%d about to wakeup T#%d, reset sleep "
                "bit for flag's loc(%p)\n",
                gtid, target_gtid, flag->get()));
 
   __kmp_win32_cond_signal(&th->th.th_suspend_cv);
   __kmp_unlock_suspend_mx(th);
 
   KF_TRACE(30, ("__kmp_resume_template: T#%d exiting after signaling wake up"
                 " for T#%d\n",
                 gtid, target_gtid));
 }
 
 template <bool C, bool S>
 void __kmp_resume_32(int target_gtid, kmp_flag_32<C, S> *flag) {
   __kmp_resume_template(target_gtid, flag);
 }
 template <bool C, bool S>
 void __kmp_resume_64(int target_gtid, kmp_flag_64<C, S> *flag) {
   __kmp_resume_template(target_gtid, flag);
 }
+template <bool C, bool S>
+void __kmp_atomic_resume_64(int target_gtid, kmp_atomic_flag_64<C, S> *flag) {
+  __kmp_resume_template(target_gtid, flag);
+}
 void __kmp_resume_oncore(int target_gtid, kmp_flag_oncore *flag) {
   __kmp_resume_template(target_gtid, flag);
 }
 
 template void __kmp_resume_32<false, true>(int, kmp_flag_32<false, true> *);
+template void __kmp_resume_32<false, false>(int, kmp_flag_32<false, false> *);
 template void __kmp_resume_64<false, true>(int, kmp_flag_64<false, true> *);
+template void
+__kmp_atomic_resume_64<false, true>(int, kmp_atomic_flag_64<false, true> *);
 
 void __kmp_yield() { Sleep(0); }
 
 void __kmp_gtid_set_specific(int gtid) {
   if (__kmp_init_gtid) {
     KA_TRACE(50, ("__kmp_gtid_set_specific: T#%d key:%d\n", gtid,
                   __kmp_gtid_threadprivate_key));
     if (!TlsSetValue(__kmp_gtid_threadprivate_key, (LPVOID)(gtid + 1)))

openmp/runtime/test/barrier/omp_barrier.c

 // RUN: %libomp-compile-and-run
 // RUN: %libomp-compile && env KMP_BLOCKTIME=infinite %libomp-run
 // RUN: %libomp-compile && env KMP_PLAIN_BARRIER_PATTERN='hierarchical,hierarchical' KMP_FORKJOIN_BARRIER_PATTERN='hierarchical,hierarchical' %libomp-run
 // RUN: %libomp-compile && env KMP_BLOCKTIME=infinite KMP_PLAIN_BARRIER_PATTERN='hierarchical,hierarchical' KMP_FORKJOIN_BARRIER_PATTERN='hierarchical,hierarchical' %libomp-run
+// RUN: %libomp-compile && env KMP_PLAIN_BARRIER_PATTERN='dist,dist' KMP_FORKJOIN_BARRIER_PATTERN='dist,dist' KMP_REDUCTION_BARRIER_PATTERN='dist,dist' %libomp-run
+// RUN: %libomp-compile && env KMP_BLOCKTIME=infinite KMP_PLAIN_BARRIER_PATTERN='dist,dist' KMP_FORKJOIN_BARRIER_PATTERN='dist,dist' KMP_REDUCTION_BARRIER_PATTERN='dist,dist' %libomp-run
 #include <stdio.h>
 #include "omp_testsuite.h"
 #include "omp_my_sleep.h"
 
 int test_omp_barrier()
 {
   int result1;
   int result2;