[Openmp-commits] [PATCH] D119586: [OpenMP][libomp] Fix crash when LIBOMP_NUM_HIDDEN_HELPER_THREADS=1.

[Andrey Churbanov via Phabricator via Openmp-commits]

AndreyChurbanov updated this revision to Diff 408040.
AndreyChurbanov added a comment.

Addressed Ravi's comment.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D119586/new/

https://reviews.llvm.org/D119586

Files:
  openmp/runtime/src/kmp_settings.cpp
  openmp/runtime/test/tasking/hidden_helper_task/single_helper_thread.c


Index: openmp/runtime/test/tasking/hidden_helper_task/single_helper_thread.c
===================================================================
--- /dev/null
+++ openmp/runtime/test/tasking/hidden_helper_task/single_helper_thread.c
@@ -0,0 +1,21 @@
+// RUN: %libomp-compile && env LIBOMP_NUM_HIDDEN_HELPER_THREADS=1 %libomp-run
+
+// The test checks that "devide-by-0" bug fixed in runtime.
+// The fix is to increment number of threads by 1 if positive,
+// so that operation
+//   (gtid) % (__kmp_hidden_helper_threads_num - 1)
+// does not cause crash.
+
+#include <stdio.h>
+#include <omp.h>
+
+int main(){
+#pragma omp target nowait
+   {
+      printf("----- in  target region\n");
+   }
+  printf("------ before taskwait\n");
+#pragma omp taskwait
+  printf("passed\n");
+  return 0;
+}
Index: openmp/runtime/src/kmp_settings.cpp
===================================================================
--- openmp/runtime/src/kmp_settings.cpp
+++ openmp/runtime/src/kmp_settings.cpp
@@ -1245,13 +1245,25 @@
   // task
   if (__kmp_hidden_helper_threads_num == 0) {
     __kmp_enable_hidden_helper = FALSE;
+  } else {
+    // Since the main thread of hidden helper team dooes not participate
+    // in tasks execution let's increment the number of threads by one
+    // so that requested number of threads do actual job.
+    __kmp_hidden_helper_threads_num++;
   }
 } // __kmp_stg_parse_num_hidden_helper_threads
 
 static void __kmp_stg_print_num_hidden_helper_threads(kmp_str_buf_t *buffer,
                                                       char const *name,
                                                       void *data) {
-  __kmp_stg_print_int(buffer, name, __kmp_hidden_helper_threads_num);
+  if (__kmp_hidden_helper_threads_num == 0) {
+    __kmp_stg_print_int(buffer, name, __kmp_hidden_helper_threads_num);
+  } else {
+    KMP_DEBUG_ASSERT(__kmp_hidden_helper_threads_num > 1);
+    // Let's exclude the main thread of hidden helper team and print
+    // number of worker threads those do actual job.
+    __kmp_stg_print_int(buffer, name, __kmp_hidden_helper_threads_num - 1);
+  }
 } // __kmp_stg_print_num_hidden_helper_threads
 
 static void __kmp_stg_parse_use_hidden_helper(char const *name,


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