Mesa (staging/19.2): util/u_queue: skip util_queue_finish if num_threads is 0

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Module: Mesa
Branch: staging/19.2
Commit: 340849f311eea4d0d17267da9f1f6a153695f19f
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=340849f311eea4d0d17267da9f1f6a153695f19f

Author: Marek Olšák <marek.olsak at amd.com>
Date:   Wed Oct 23 21:01:38 2019 -0400

util/u_queue: skip util_queue_finish if num_threads is 0

This fixes a deadlock in pthread_barrier_destroy.

Cc: 19.1 19.2 <mesa-stable at lists.freedesktop.org>
Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
(cherry picked from commit c2efd2cbfb19808cd4bf5f2f0cf62455f80f1a2f)

---

 src/util/u_queue.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/util/u_queue.c b/src/util/u_queue.c
index 81225a80faa..9a51b71cfe1 100644
--- a/src/util/u_queue.c
+++ b/src/util/u_queue.c
@@ -637,6 +637,13 @@ util_queue_finish(struct util_queue *queue)
     * wait for it exclusively.
     */
    mtx_lock(&queue->finish_lock);
+
+   /* The number of threads can be changed to 0, e.g. by the atexit handler. */
+   if (!queue->num_threads) {
+      mtx_unlock(&queue->finish_lock);
+      return;
+   }
+
    fences = malloc(queue->num_threads * sizeof(*fences));
    util_barrier_init(&barrier, queue->num_threads);