From c2efd2cbfb19808cd4bf5f2f0cf62455f80f1a2f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marek=20Ol=C5=A1=C3=A1k?= <marek.olsak@amd.com>
Date: Wed, 23 Oct 2019 21:01:38 -0400
Subject: [PATCH] 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@lists.freedesktop.org>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
---
 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 ca72968053a..47b8dcd407c 100644
--- a/src/util/u_queue.c
+++ b/src/util/u_queue.c
@@ -647,6 +647,13 @@ 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);