drm/i915: Avoid stalling on pending flips for legacy cursor updates

The legacy cursor ioctl expects to be asynchronous with respect to other
screen updates, in particular page flips. As X updates the cursor from a
signal context, if the cursor blocks then it will stall both the input
and output chains causing bad stuttering and horrible UX.

Reported-and-tested-by: Rafael Ristovski <[email protected]>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94980
Fixes: 5008e874edd34 ("drm/i915: Make wait_for_flips interruptible.")
Suggested-by: Maarten Lankhorst <[email protected]>
Signed-off-by: Chris Wilson <[email protected]>
Cc: Maarten Lankhorst <[email protected]>
Cc: Ville Syrjälä <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: [email protected]
Link: http://patchwork.freedesktop.org/patch/msgid/[email protected]
Acked-by: Daniel Vetter <[email protected]>
Reviewed-by: Maarten Lankhorst <[email protected]>

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 4cca155376bed01a21b584154e814b89b047e73f..c5b9687091f44b21b2fa41fa66e65d3ab3d3ce42 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -13446,6 +13446,9 @@ static int intel_atomic_prepare_commit(struct drm_device *dev,
        }
 
        for_each_crtc_in_state(state, crtc, crtc_state, i) {
+               if (state->legacy_cursor_update)
+                       continue;
+
                ret = intel_crtc_wait_for_pending_flips(crtc);
                if (ret)
                        return ret;