[gcc/devel/omp/gcc-11] openmp: Notify team barrier of pending tasks in omp_fulfill_event

[gcc/devel/omp/gcc-11] openmp: Notify team barrier of pending tasks in omp_fulfill_event

[Kwok Yeung]

https://gcc.gnu.org/g:a21ebe77c5b93e7cdcf2ad3e8ea159fa54708343

commit a21ebe77c5b93e7cdcf2ad3e8ea159fa54708343
Author: Kwok Cheung Yeung <kcy@codesourcery.com>
Date:   Fri May 14 09:59:11 2021 -0700

    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.
    
    (cherry picked from commit ba886d0c488ebea2eb2df95c2069a3e207704dac)

Diff:
---
 libgomp/ChangeLog.omp                              |  9 ++++
 libgomp/task.c                                     |  1 +
 .../libgomp.c-c++-common/task-detach-13.c          | 59 ++++++++++++++++++++++
 3 files changed, 69 insertions(+)

diff --git a/libgomp/ChangeLog.omp b/libgomp/ChangeLog.omp
index 028ddc24841..94bc2a48017 100644
--- a/libgomp/ChangeLog.omp
+++ b/libgomp/ChangeLog.omp
@@ -1,3 +1,12 @@
+2021-05-17  Kwok Cheung Yeung  <kcy@codesourcery.com>
+
+	Backport from mainline
+	2021-05-17  Kwok Cheung Yeung  <kcy@codesourcery.com>
+
+	* 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.
+
 2021-05-17  Tobias Burnus  <tobias@codesourcery.com>
 
 	Backported from master:
diff --git a/libgomp/task.c b/libgomp/task.c
index 1c73c759a8d..feb4796a3ac 100644
--- a/libgomp/task.c
+++ b/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;
diff --git a/libgomp/testsuite/libgomp.c-c++-common/task-detach-13.c b/libgomp/testsuite/libgomp.c-c++-common/task-detach-13.c
new file mode 100644
index 00000000000..9622fd8251f
--- /dev/null
+++ b/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;
+}