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egl/wayland: wait for compositor to release shm buffers

Browse source 
Some Wayland compositors, notably Exo, do not always release buffers
fast enough, and not in sync with their frame callbacks, to guarantee
that a free buffer is available the next time a client calls
`eglSwapBuffers()`.

This currently leads to a crash in `dri2_wl_swrast_get_backbuffer_data()`
with the swrast backend. To avoid this, simply block until the
compositor releases a buffer eventually.

While arguably compositors should release buffers they don't need any
more for the next frame, this can be quite complex depending on
the architecture - notably multi-process/IPC in case of Exo.

cc: mesa-stable

Signed-off-by: Robert Mader <robert.mader@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24091>
(cherry picked from commit 74451ed3f0)
This commit is contained in:
Robert Mader 2023-07-11 16:24:41 +02:00 • committed by Dylan Baker
parent ddffe6e8a1
commit 6fea9af930
2 changed files with 10 additions and 6 deletions
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2
.pick_status.json
View file

@ -124,7 +124,7 @@
"description": "egl/wayland: wait for compositor to release shm buffers",
"nominated": true,
"nomination_type": 0,
"resolution": 0,
"resolution": 1,
"main_sha": null,
"because_sha": null,
"notes": null

14
src/egl/drivers/dri2/platform_wayland.c
View file

@ -2454,7 +2454,7 @@ swrast_update_buffers(struct dri2_egl_surface *dri2_surf)
}
/* else choose any another free location */
if (!dri2_surf->back) {
while (!dri2_surf->back) {
for (int i = 0; i < ARRAY_SIZE(dri2_surf->color_buffers); i++) {
if (!dri2_surf->color_buffers[i].locked) {
dri2_surf->back = &dri2_surf->color_buffers[i];
@ -2472,11 +2472,15 @@ swrast_update_buffers(struct dri2_egl_surface *dri2_surf)
break;
}
}
}
if (!dri2_surf->back) {
_eglError(EGL_BAD_ALLOC, "failed to find free buffer");
return -1;
/* wait for the compositor to release a buffer */
if (!dri2_surf->back) {
if (wl_display_dispatch_queue(dri2_dpy->wl_dpy, dri2_surf->wl_queue) ==
-1) {
_eglError(EGL_BAD_ALLOC, "waiting for a free buffer failed");
return -1;
}
}
}
dri2_surf->back->locked = true;