Mesa (staging/20.2): vulkan/wsi: fix possible random stalls in wsi_display_wait_for_event

[GitLab Mirror]

Module: Mesa
Branch: staging/20.2
Commit: 0bc9a81733e975aaacab65a67f7eec3dd4f639c2
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=0bc9a81733e975aaacab65a67f7eec3dd4f639c2

Author: Marcin Ślusarz <marcin.slusarz at intel.com>
Date:   Fri Oct 16 20:07:28 2020 +0200

vulkan/wsi: fix possible random stalls in wsi_display_wait_for_event

pthread_cond_broadcast man page says this:
"The pthread_cond_broadcast() or pthread_cond_signal() functions may
 be called by a thread whether or not it currently owns the mutex that
 threads calling pthread_cond_wait() or pthread_cond_timedwait() have
 associated with the condition variable during their waits; however,
 if predictable scheduling behavior is required, then that mutex shall
 be locked by the thread calling pthread_cond_broadcast() or
 pthread_cond_signal()."

Found by reading the code.
Compile tested only.

Fixes: da997ebec92 ("vulkan: Add KHR_display extension using DRM [v10]")

Signed-off-by: Marcin Ślusarz <marcin.slusarz at intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7197>
(cherry picked from commit 440813114281bfd05c2b0d26c6488d1410790be4)

---

 .pick_status.json                   | 2 +-
 src/vulkan/wsi/wsi_common_display.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/.pick_status.json b/.pick_status.json
index d15e4552bf5..171ae40b136 100644
--- a/.pick_status.json
+++ b/.pick_status.json
@@ -166,7 +166,7 @@
         "description": "vulkan/wsi: fix possible random stalls in wsi_display_wait_for_event",
         "nominated": true,
         "nomination_type": 1,
-        "resolution": 0,
+        "resolution": 1,
         "master_sha": null,
         "because_sha": "da997ebec92942193955386535813374286b7fb1"
     },
diff --git a/src/vulkan/wsi/wsi_common_display.c b/src/vulkan/wsi/wsi_common_display.c
index b05d7cc479d..e77211cf0a1 100644
--- a/src/vulkan/wsi/wsi_common_display.c
+++ b/src/vulkan/wsi/wsi_common_display.c
@@ -1209,8 +1209,8 @@ wsi_display_wait_thread(void *data)
       if (ret > 0) {
          pthread_mutex_lock(&wsi->wait_mutex);
          (void) drmHandleEvent(wsi->fd, &event_context);
-         pthread_mutex_unlock(&wsi->wait_mutex);
          pthread_cond_broadcast(&wsi->wait_cond);
+         pthread_mutex_unlock(&wsi->wait_mutex);
       }
    }
    return NULL;