openmp: Notify team barrier of pending tasks in omp_fulfill_event

The team barrier should be notified of any new tasks that become runnable
as the result of a completing task, otherwise the barrier threads might
not resume processing available tasks, resulting in a hang.

2021-05-17  Kwok Cheung Yeung  <kcy@codesourcery.com>

	libgomp/
	* task.c (omp_fulfill_event): Call gomp_team_barrier_set_task_pending
	if new tasks generated.
	* testsuite/libgomp.c-c++-common/task-detach-13.c: New.

libgomp/task.c

@@ -2460,6 +2460,7 @@ omp_fulfill_event (omp_event_handle_t event)
   if (new_tasks > 0)
     {
       /* Wake up threads to run new tasks.  */
+      gomp_team_barrier_set_task_pending (&team->barrier);
       do_wake = team->nthreads - team->task_running_count;
       if (do_wake > new_tasks)
 	do_wake = new_tasks;

libgomp/testsuite/libgomp.c-c++-common/task-detach-13.c

@@ -0,0 +1,59 @@
+/* { dg-do run { target *-*-linux* *-*-gnu* *-*-freebsd* } } */
+/* { dg-timeout 10 } */
+
+/* Test that omp_fulfill_event works when called from an external
+   non-OpenMP thread.  */
+
+#include <omp.h>
+#include <unistd.h>
+#include <pthread.h>
+#include <stdio.h>
+
+int finished = 0;
+int event_pending = 0;
+omp_event_handle_t detach_event;
+
+void *
+fulfill_thread (void *)
+{
+  while (!__atomic_load_n (&finished, __ATOMIC_RELAXED))
+    {
+      if (__atomic_load_n (&event_pending, __ATOMIC_ACQUIRE))
+	{
+	  omp_fulfill_event (detach_event);
+	  __atomic_store_n (&event_pending, 0, __ATOMIC_RELEASE);
+	}
+
+      sleep(1);
+    }
+
+  return 0;
+}
+
+int
+main (void)
+{
+  pthread_t thr;
+  int dep;
+  pthread_create (&thr, NULL, fulfill_thread, 0);
+
+  #pragma omp parallel
+    #pragma omp single
+    {
+      omp_event_handle_t ev;
+
+      #pragma omp task depend (out: dep) detach (ev)
+      {
+	detach_event = ev;
+	__atomic_store_n (&event_pending, 1, __ATOMIC_RELEASE);
+      }
+
+      #pragma omp task depend (in: dep)
+      {
+	__atomic_store_n (&finished, 1, __ATOMIC_RELAXED);
+      }
+    }
+
+  pthread_join (thr, 0);
+  return 0;
+}