loader/dri3: Use dri3_wait_for_event_locked in loader_dri3_wait_for_msc

Before, if one thread ended up waiting in dri3_wait_for_event_locked
and another one in loader_dri3_wait_for_msc at the same time, one thread
could end up processing an event the other thread was waiting for, which
could result in the latter thread waiting longer than necessary
(possibly indefinitely).

Noticed by inspection.

v2:
* Drop xcb_flush call from loader_dri3_wait_for_msc in favour of the one
  in dri3_wait_for_event_locked (Kenneth Graunke)

Fixes: 7b0e8264dd21 "loader/dri3: Try to make sure we only process our
                     own NotifyMSC events"

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5368>

diff --git a/src/loader/loader_dri3_helper.c b/src/loader/loader_dri3_helper.c
index 622c238d950c99e89b69de8482eb3040b9be9b2b..425faba8f640a8ac770895a92262dcc695348edd 100644 (file)
--- a/src/loader/loader_dri3_helper.c
+++ b/src/loader/loader_dri3_helper.c
@@ -577,22 +577,16 @@ loader_dri3_wait_for_msc(struct loader_dri3_drawable *draw,
                                                      target_msc,
                                                      divisor,
                                                      remainder);
-   xcb_generic_event_t *ev;
    unsigned full_sequence;
 
    mtx_lock(&draw->mtx);
-   xcb_flush(draw->conn);
 
    /* Wait for the event */
    do {
-      ev = xcb_wait_for_special_event(draw->conn, draw->special_event);
-      if (!ev) {
+      if (!dri3_wait_for_event_locked(draw, &full_sequence)) {
          mtx_unlock(&draw->mtx);
          return false;
       }
-
-      full_sequence = ev->full_sequence;
-      dri3_handle_present_event(draw, (void *) ev);
    } while (full_sequence != cookie.sequence || draw->notify_msc < target_msc);
 
    *ust = draw->notify_ust;