libgomp: Fix segfault with posthumous orphan tasks [PR104385]

The following patch fixes crashes with posthumous orphan tasks.
When a parent task finishes, gomp_clear_parent clears the parent
pointers of its children tasks present in the parent->children_queue.
But children that are still waiting for dependencies aren't in that
queue yet, they will be added there only when the sibling they are
waiting for exits.  Unfortunately we were adding those tasks into
the queues with the original task->parent which then causes crashes
because that task is gone and freed.  The following patch fixes that
by clearing the parent field when we schedule such task for running
by adding it into the queues and we know that the sibling task which
is about to finish has NULL parent.

2022-02-08  Jakub Jelinek  <jakub@redhat.com>

	PR libgomp/104385
	* task.c (gomp_task_run_post_handle_dependers): If parent is NULL,
	clear task->parent.
	* testsuite/libgomp.c/pr104385.c: New test.

diff --git a/libgomp/task.c b/libgomp/task.c
index 53072d8ea81fa059df0c34f76f3689e05d2aa6f8..828348c4cf4815a3d71e531ae1100392126bd43a 100644 (file)
--- a/libgomp/task.c
+++ b/libgomp/task.c
@@ -1248,6 +1248,8 @@ gomp_task_run_post_handle_dependers (struct gomp_task *child_task,
                }
            }
        }
+      else
+       task->parent = NULL;
       if (taskgroup)
        {
          priority_queue_insert (PQ_TASKGROUP, &taskgroup->taskgroup_queue,

diff --git a/libgomp/testsuite/libgomp.c/pr104385.c b/libgomp/testsuite/libgomp.c/pr104385.c
new file mode 100644 (file)
index 0000000..07495e6
--- /dev/null
+++ b/libgomp/testsuite/libgomp.c/pr104385.c
@@ -0,0 +1,26 @@
+/* PR libgomp/104385 */
+
+#include <unistd.h>
+
+int
+main ()
+{
+  int j = 0;
+  #pragma omp parallel shared(j) num_threads(2)
+  {
+    #pragma omp barrier
+    #pragma omp master
+    #pragma omp task shared(j)
+    {
+      #pragma omp task depend(out: j) shared(j)
+      {
+        usleep (10000);
+        j = 1;
+      }
+
+      #pragma omp task depend(inout: j) shared(j)
+      j += 1;
+    }
+  }
+  return j - 2;
+}