Index: openmp/trunk/runtime/src/kmp.h
===================================================================
--- openmp/trunk/runtime/src/kmp.h
+++ openmp/trunk/runtime/src/kmp.h
@@ -3263,6 +3263,7 @@
 
 extern kmp_r_sched_t __kmp_get_schedule_global(void);
 extern void __kmp_adjust_num_threads(int new_nproc);
+extern void __kmp_check_stksize(size_t *val);
 
 extern void *___kmp_allocate(size_t size KMP_SRC_LOC_DECL);
 extern void *___kmp_page_allocate(size_t size KMP_SRC_LOC_DECL);
Index: openmp/trunk/runtime/src/kmp_settings.cpp
===================================================================
--- openmp/trunk/runtime/src/kmp_settings.cpp
+++ openmp/trunk/runtime/src/kmp_settings.cpp
@@ -289,6 +289,20 @@
   }
 } // __kmp_stg_parse_bool
 
+// placed here in order to use __kmp_round4k static function
+void __kmp_check_stksize(size_t *val) {
+  // if system stack size is too big then limit the size for worker threads
+  if (*val > KMP_DEFAULT_STKSIZE * 16) // just a heuristics...
+    *val = KMP_DEFAULT_STKSIZE * 16;
+  if (*val < KMP_MIN_STKSIZE)
+    *val = KMP_MIN_STKSIZE;
+  if (*val > KMP_MAX_STKSIZE)
+    *val = KMP_MAX_STKSIZE; // dead code currently, but may work in future
+#if KMP_OS_DARWIN
+  *val = __kmp_round4k(*val);
+#endif // KMP_OS_DARWIN
+}
+
 static void __kmp_stg_parse_size(char const *name, char const *value,
                                  size_t size_min, size_t size_max,
                                  int *is_specified, size_t *out,
Index: openmp/trunk/runtime/src/z_Linux_util.cpp
===================================================================
--- openmp/trunk/runtime/src/z_Linux_util.cpp
+++ openmp/trunk/runtime/src/z_Linux_util.cpp
@@ -1833,6 +1833,17 @@
 
   __kmp_xproc = __kmp_get_xproc();
 
+#if ! KMP_32_BIT_ARCH
+  struct rlimit rlim;
+  // read stack size of calling thread, save it as default for worker threads;
+  // this should be done before reading environment variables
+  status = getrlimit(RLIMIT_STACK, &rlim);
+  if (status == 0) { // success?
+    __kmp_stksize = rlim.rlim_cur;
+    __kmp_check_stksize(&__kmp_stksize); // check value and adjust if needed
+  }
+#endif /* KMP_32_BIT_ARCH */
+
   if (sysconf(_SC_THREADS)) {
 
     /* Query the maximum number of threads */
Index: openmp/trunk/runtime/test/misc_bugs/stack-propagate.c
===================================================================
--- openmp/trunk/runtime/test/misc_bugs/stack-propagate.c
+++ openmp/trunk/runtime/test/misc_bugs/stack-propagate.c
@@ -0,0 +1,65 @@
+// RUN: %libomp-compile-and-run
+
+// https://bugs.llvm.org/show_bug.cgi?id=26540 requested
+// stack size to be propagated from master to workers.
+// Library implements propagation of not too big stack
+// for Linux x86_64 platform (skipped Windows for now).
+//
+// The test checks that workers can use more than 4MB
+// of stack (4MB - was historical default for
+// stack size of worker thread in runtime library).
+
+#include <stdio.h>
+#include <omp.h>
+#if !defined(_WIN32)
+#include <sys/resource.h> // getrlimit
+#endif
+
+#define STK 4800000
+
+double foo(int n, int th)
+{
+  double arr[n];
+  int i;
+  double res = 0.0;
+  for (i = 0; i < n; ++i) {
+    arr[i] = (double)i / (n + 2);
+  }
+  for (i = 0; i < n; ++i) {
+    res += arr[i] / n;
+  }
+  return res;
+}
+
+int main(int argc, char *argv[])
+{
+#if defined(_WIN32)
+  // don't test Windows
+  printf("stack propagation not implemented, skipping test...\n");
+  return 0;
+#else
+  int status;
+  double val = 0.0;
+  int m = STK / 8; // > 4800000 bytes per thread
+  // read stack size of calling thread, save it as default
+  struct rlimit rlim;
+  status = getrlimit(RLIMIT_STACK, &rlim);
+  if (sizeof(void *) > 4 &&                 // do not test 32-bit systems,
+      status == 0 && rlim.rlim_cur > STK) { // or small initial stack size
+#pragma omp parallel reduction(+:val)
+    {
+      val += foo(m, omp_get_thread_num());
+    }
+  } else {
+    printf("too small stack size limit (needs about 8MB), skipping test...\n");
+    return 0;
+  }
+  if (val > 0.1) {
+    printf("passed\n");
+    return 0;
+  } else {
+    printf("failed, val = %f\n", val);
+    return 1;
+  }
+#endif // _WIN32
+}