It turned out that with recent changes that call into dri3 from
glFinish(),
it appears like different thread end up waiting for X events
simultaneously,
causing deadlocks since they steal events from eachoter and update
the dri3
counters behind eachothers backs.
This patch intends to improve on that. It allows at most one thread at a
time to wait on events for a single drawable. If another thread
intends to
do the same, it's put to sleep until the first thread finishes
waiting, and
then it rechecks counters and optionally retries the waiting. Threads
that
poll for X events never pulls X events off the event queue if there are
other threads waiting for events on that drawable. Counters in the
dri3 drawable structure are protected by a mutex. Finally, the mutex we
introduce is never held while waiting for the X server to avoid
unnecessary stalls.
This does not make dri3 drawables completely thread-safe but at least
it's a
first step.
Bugzilla:
https://urldefense.proofpoint.com/v2/url?u=https-3A__bugs.freedesktop.org_show-5Fbug.cgi-3Fid-3D102358&d=DwICaQ&c=uilaK90D4TOVoH58JNXRgQ&r=wnSlgOCqfpNS4d02vP68_E9q2BNMCwfD2OZ_6dCFVQQ&m=yqE5Xb9bQg5hA8gP7s0b3dSSZoPWaAEKACqD8qfhdZo&s=wf-xBzPlZ805RCV1hnDgoyW0fYe2ZX3Qwie66SU936g&e=
Fixes: d5ba75f8881 "st/dri2 Plumb the flush_swapbuffer functionality
through to dri3"
Signed-off-by: Thomas Hellstrom <thellst...@vmware.com>
---
src/loader/loader_dri3_helper.c | 77
+++++++++++++++++++++++++++++++----------
src/loader/loader_dri3_helper.h | 10 ++++++
2 files changed, 69 insertions(+), 18 deletions(-)
diff --git a/src/loader/loader_dri3_helper.c
b/src/loader/loader_dri3_helper.c
index 19ab581..7e6b8b2 100644
--- a/src/loader/loader_dri3_helper.c
+++ b/src/loader/loader_dri3_helper.c
@@ -32,7 +32,6 @@
#include <X11/Xlib-xcb.h>
-#include <c11/threads.h>
#include "loader_dri3_helper.h"
/* From xmlpool/options.h, user exposed so should be stable */
@@ -186,8 +185,11 @@ dri3_fence_await(xcb_connection_t *c, struct
loader_dri3_drawable *draw,
{
xcb_flush(c);
xshmfence_await(buffer->shm_fence);
- if (draw)
+ if (draw) {
+ mtx_lock(&draw->mtx);
dri3_flush_present_events(draw);
+ mtx_unlock(&draw->mtx);
+ }
}
static void
@@ -245,6 +247,9 @@ loader_dri3_drawable_fini(struct
loader_dri3_drawable *draw)
xcb_discard_reply(draw->conn, cookie.sequence);
xcb_unregister_for_special_event(draw->conn,
draw->special_event);
}
+
+ cnd_destroy(&draw->event_cnd);
+ mtx_destroy(&draw->mtx);
}
int
@@ -276,6 +281,8 @@ loader_dri3_drawable_init(xcb_connection_t *conn,
draw->cur_blit_source = -1;
draw->back_format = __DRI_IMAGE_FORMAT_NONE;
+ mtx_init(&draw->mtx, mtx_plain);
+ cnd_init(&draw->event_cnd);
if (draw->ext->config)
draw->ext->config->configQueryi(draw->dri_screen,
@@ -407,13 +414,27 @@ dri3_handle_present_event(struct
loader_dri3_drawable *draw,
}
static bool
-dri3_wait_for_event(struct loader_dri3_drawable *draw)
+dri3_wait_for_event_locked(struct loader_dri3_drawable *draw)
{
xcb_generic_event_t *ev;
xcb_present_generic_event_t *ge;
xcb_flush(draw->conn);
