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wsi/x11: Avoid non-causal present timings when not flipping.

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This is not an issue on Xwl since it goes through frame callback
mechanism + explicit sync and this issue has only been observed on X11.

Signed-off-by: Hans-Kristian Arntzen <post@arntzen-software.no>
Reviewed-by: Mario Kleiner <mario.kleiner.de@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/39551>
This commit is contained in:
Hans-Kristian Arntzen 2026-02-19 15:31:15 +01:00 • committed by Marge Bot
parent 02337d2b65
commit e0abbc613d
1 changed files with 31 additions and 4 deletions
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35
src/vulkan/wsi/wsi_common_x11.c
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@ -1293,6 +1293,7 @@ struct x11_swapchain {
struct wsi_image_timing_request timing_request;
bool has_reliable_msc;
bool last_complete_is_flip;
struct x11_image images[0];
};
@ -1396,6 +1397,8 @@ static void x11_present_complete(struct x11_swapchain *swapchain,
struct x11_image *image, uint32_t index,
uint64_t msc, uint64_t ust, bool flip)
{
swapchain->last_complete_is_flip = flip;
/* Update estimate for refresh rate. */
if (swapchain->base.present_timing.active)
x11_present_update_refresh_cycle_estimate(swapchain, msc, ust, flip);
@ -1994,6 +1997,25 @@ x11_needs_wait_for_fences(const struct wsi_device *wsi_device,
}
}
static bool
x11_swapchain_present_timing_is_out_of_order_completion(
const struct x11_swapchain *chain,
struct wsi_x11_connection *wsi_conn,
const struct wsi_image_timing_request *request)
{
/* On native X11, COMPLETE can be called even before the GPU is done rendering when not flipping.
* This creates a lot of confusion for present timing since we have no way to
* guarantee anything useful.
*
* The transition between blit and flip could create a small blip where timings are not quite accurate,
* since we base our decisions on the previously completed frame.
*
* The primary way this weirdness manifests for present timing is that COMPLETE may get signaled,
* but the timestamp query has not yet been written and we cannot properly report timestamps.
*/
return !chain->last_complete_is_flip && !wsi_conn->is_xwayland && (request->feedback || request->time);
}
/* This matches Wayland. */
#define X11_SWAPCHAIN_MAILBOX_IMAGES 4
@ -2485,10 +2507,15 @@ x11_manage_present_queue(void *state)
VkPresentModeKHR present_mode = chain->images[image_index].present_mode;
if (x11_needs_wait_for_fences(chain->base.wsi, wsi_conn,
present_mode) &&
/* not necessary with explicit sync */
!chain->base.image_info.explicit_sync) {
/* Not necessary to block when we have explicit sync */
bool need_fence_wait =
x11_needs_wait_for_fences(chain->base.wsi, wsi_conn, present_mode) &&
!chain->base.image_info.explicit_sync;
bool need_timing_fence_wait = x11_swapchain_present_timing_is_out_of_order_completion(
chain, wsi_conn, &chain->images[image_index].timing_request);
if (need_fence_wait || need_timing_fence_wait) {
MESA_TRACE_SCOPE("wait fence");
result = chain->base.wsi->WaitForFences(chain->base.device, 1,
&chain->base.fences[image_index],