[OpenMP] Possible fix for sporadic test failure from loop_dispatch.c

[hbae]

Summary

This patch tries to fix sporadic test failure after the change https://reviews.llvm.org/D122107.
Made the test wait until every thread has at least one loop iteration.
We may need to relax the check if this does not fix the problem.

[protze.joachim]

Thanks for the fix! I'm quite confident that this change will fix the sporiadic test failures (most probably under high system load).

I suggest to refer D122107 in the commit message.
And I also suggest to use the actual team size in the OMPT_WAIT, just to prevent deadlock in case less threads are provided.

openmp/runtime/test/ompt/worksharing/for/loop_dispatch.c

26

36

[hbae]

Applied suggested changes.

[protze.joachim]

lgtm now

openmp/runtime/test/ompt/worksharing/for/loop_dispatch.c

 // RUN: %libomp-compile-and-run | %sort-threads | FileCheck %s
 // REQUIRES: ompt
 // XFAIL: gcc
 // GCC doesn't call runtime for static schedule
 
 #include "callback.h"
 
 #define WORK_SIZE 64
 
 int main() {
   int i;
+  int wait_s = 0;
 
 #pragma omp parallel num_threads(4)
   {
+    int wait_id = 0;
+    int team_size = omp_get_num_threads();
 #pragma omp for schedule(static, WORK_SIZE / 4)
     for (i = 0; i < WORK_SIZE; i++) {}
 
 #pragma omp for schedule(dynamic)
     for (i = 0; i < WORK_SIZE; i++) {
-      // Make every iteration takes at least 1ms.
-      delay(1000);
+      if (wait_id == 0) {
+        // Wait until every thread has at least one iteration assigned
+        OMPT_SIGNAL(wait_s);
+        OMPT_WAIT(wait_s, team_size);
+        wait_id++;
+      }
     }
 
 #pragma omp for schedule(guided)
     for (i = 0; i < WORK_SIZE; i++) {
-      // Make every iteration takes at least 1ms.
-      delay(1000);
+      if (wait_id == 1) {
+        // Wait until every thread has at least one iteration assigned
+        OMPT_SIGNAL(wait_s);
+        OMPT_WAIT(wait_s, 2 * team_size);
+        wait_id++;
+      }
     }
   }
 
   return 0;
 }
 
 // CHECK-NOT: {{^}}0: Could not register callback 'ompt_callback_parallel_begin'
 // CHECK-NOT: {{^}}0: Could not register callback 'ompt_callback_implicit_task'