Fixes to wait-loop code

jpeyton52 · jpeyton52 · commit 3f5dfc256204 · 2015-11-09T16:31:51.000Z
1) Add get_ptr_type() method to all wait flag types. 2) Flag in sleep_loc may change type by the time the resume is called from __kmp_null_resume_wrapper. We use get_ptr_type to obtain the real type and compare it to the casted object received. If they don't match, we know the flag has changed (already resumed and replaced by another flag). If they match, it doesn't hurt to go ahead and resume it. Differential Revision: http://reviews.llvm.org/D14458 llvm-svn: 252487
diff --git a/openmp/runtime/src/kmp_tasking.c b/openmp/runtime/src/kmp_tasking.c
@@ -39,6 +39,7 @@ static void __kmp_bottom_half_finish_proxy( kmp_int32 gtid, kmp_task_t * ptask )
 
 static inline void __kmp_null_resume_wrapper(int gtid, volatile void *flag) {
     if (!flag) return;
+    // Attempt to wake up a thread: examine its type and call appropriate template
     switch (((kmp_flag_64 *)flag)->get_type()) {
     case flag32: __kmp_resume_32(gtid, NULL); break;
     case flag64: __kmp_resume_64(gtid, NULL); break;
diff --git a/openmp/runtime/src/kmp_wait_release.h b/openmp/runtime/src/kmp_wait_release.h
@@ -438,6 +438,7 @@ class kmp_flag_32 : public kmp_basic_flag<kmp_uint32> {
                             USE_ITT_BUILD_ARG(itt_sync_obj));
     }
     void release() { __kmp_release_template(this); }
+    flag_type get_ptr_type() { return flag32; }
 };
 
 class kmp_flag_64 : public kmp_basic_flag<kmp_uint64> {
@@ -458,6 +459,7 @@ class kmp_flag_64 : public kmp_basic_flag<kmp_uint64> {
                             USE_ITT_BUILD_ARG(itt_sync_obj));
     }
     void release() { __kmp_release_template(this); }
+    flag_type get_ptr_type() { return flag64; }
 };
 
 // Hierarchical 64-bit on-core barrier instantiation
@@ -551,6 +553,7 @@ class kmp_flag_oncore : public kmp_flag<kmp_uint64> {
     }
     kmp_uint8 *get_stolen() { return NULL; }
     enum barrier_type get_bt() { return bt; }
+    flag_type get_ptr_type() { return flag_oncore; }
 };
 
 
diff --git a/openmp/runtime/src/z_Linux_util.c b/openmp/runtime/src/z_Linux_util.c
@@ -1837,11 +1837,12 @@ static inline void __kmp_resume_template( int target_gtid, C *flag )
     status = pthread_mutex_lock( &th->th.th_suspend_mx.m_mutex );
     KMP_CHECK_SYSFAIL( "pthread_mutex_lock", status );
 
-    if (!flag) {
+    if (!flag) { // coming from __kmp_null_resume_wrapper
         flag = (C *)th->th.th_sleep_loc;
     }
 
-    if (!flag) {
+    // 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
         KF_TRACE( 5, ( "__kmp_resume_template: T#%d exiting, thread T#%d already awake: flag(%p)\n",
                        gtid, target_gtid, NULL ) );
         status = pthread_mutex_unlock( &th->th.th_suspend_mx.m_mutex );
diff --git a/openmp/runtime/src/z_Windows_NT_util.c b/openmp/runtime/src/z_Windows_NT_util.c
@@ -455,11 +455,12 @@ static inline void __kmp_resume_template( int target_gtid, C *flag )
     __kmp_suspend_initialize_thread( th );
     __kmp_win32_mutex_lock( &th->th.th_suspend_mx );
 
-    if (!flag) {
+    if (!flag) { // coming from __kmp_null_resume_wrapper
         flag = (C *)th->th.th_sleep_loc;
     }
 
-    if (!flag) {
+    // 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
         KF_TRACE( 5, ( "__kmp_resume_template: T#%d exiting, thread T#%d already awake: flag's loc(%p)\n",
                        gtid, target_gtid, NULL ) );
         __kmp_win32_mutex_unlock( &th->th.th_suspend_mx );

Original file line number	Diff line number	Diff line change
`@@ -438,6 +438,7 @@ class kmp_flag_32 : public kmp_basic_flag<kmp_uint32> {`
`438`	`438`	`USE_ITT_BUILD_ARG(itt_sync_obj));`
`439`	`439`	`}`
`440`	`440`	`void release() { __kmp_release_template(this); }`
	`441`	`+ flag_type get_ptr_type() { return flag32; }`
`441`	`442`	`};`
`442`	`443`
`443`	`444`	`class kmp_flag_64 : public kmp_basic_flag<kmp_uint64> {`
`@@ -458,6 +459,7 @@ class kmp_flag_64 : public kmp_basic_flag<kmp_uint64> {`
`458`	`459`	`USE_ITT_BUILD_ARG(itt_sync_obj));`
`459`	`460`	`}`
`460`	`461`	`void release() { __kmp_release_template(this); }`
	`462`	`+ flag_type get_ptr_type() { return flag64; }`
`461`	`463`	`};`
`462`	`464`
`463`	`465`	`// Hierarchical 64-bit on-core barrier instantiation`
`@@ -551,6 +553,7 @@ class kmp_flag_oncore : public kmp_flag<kmp_uint64> {`
`551`	`553`	`}`
`552`	`554`	`kmp_uint8 *get_stolen() { return NULL; }`
`553`	`555`	`enum barrier_type get_bt() { return bt; }`
	`556`	`+ flag_type get_ptr_type() { return flag_oncore; }`
`554`	`557`	`};`
`555`	`558`
`556`	`559`