present: Avoid crashes in DebugPresent(), a bit more info.

DebugPresent() crashed the server when a dri3 drawable
was closed while a pageflipped present was still pending,
due to vblank->window-> Null-Ptr deref, so debug builds
caused new problems to debug.

E.g.,

glXSwapBuffers(...);
glXDestroyWindow(...);
-> Pageflip for non-existent window completes -> boom.

Also often happens when switching desktop compositor on/off
due to Present unflips, or when logging out of session.

Also add info if a Present is queued for copyswap or pageflip,
if the present is vsynced, and the serial no of the Present
request, to aid debugging of pageflip and vsync issues. The
serial number is useful as Mesa's dri3/present backend encodes
its sendSBC in the serial number, so one can easily correlate
server debug output with Mesa and with the SBC values returned
to actual OpenGL client applications via OML_sync_control and
INTEL_swap_events extension, makes debugging quite a bit more
easy.

Please also cherry-pick this for a 1.16.x stable update.

Signed-off-by: Mario Kleiner <mario.kleiner.de@gmail.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Keith Packard <keithp@keithp.com>

1 files changed, 4 insertions, 4 deletions

diff --git a/present/present.c b/present/present.c
index ac9047edb..e5d3fd551 100644
--- a/present/present.c
+++ b/present/present.c
@@ -440,7 +440,7 @@ present_flip_notify(present_vblank_ptr vblank, uint64_t ust, uint64_t crtc_msc)
     DebugPresent(("\tn %lld %p %8lld: %08lx -> %08lx\n",
                   vblank->event_id, vblank, vblank->target_msc,
                   vblank->pixmap ? vblank->pixmap->drawable.id : 0,
-                  vblank->window->drawable.id));
+                  vblank->window ? vblank->window->drawable.id : 0));
 
     assert (vblank == screen_priv->flip_pending);
 
@@ -859,10 +859,10 @@ present_pixmap(WindowPtr window,
     }
 
     if (pixmap)
-        DebugPresent(("q %lld %p %8lld: %08lx -> %08lx (crtc %p)\n",
+        DebugPresent(("q %lld %p %8lld: %08lx -> %08lx (crtc %p) flip %d vsync %d serial %d\n",
                       vblank->event_id, vblank, target_msc,
                       vblank->pixmap->drawable.id, vblank->window->drawable.id,
-                      target_crtc));
+                      target_crtc, vblank->flip, vblank->sync_flip, vblank->serial));
 
     xorg_list_add(&vblank->event_queue, &present_exec_queue);
     vblank->queued = TRUE;
@@ -955,7 +955,7 @@ present_vblank_destroy(present_vblank_ptr vblank)
     DebugPresent(("\td %lld %p %8lld: %08lx -> %08lx\n",
                   vblank->event_id, vblank, vblank->target_msc,
                   vblank->pixmap ? vblank->pixmap->drawable.id : 0,
-                  vblank->window->drawable.id));
+                  vblank->window ? vblank->window->drawable.id : 0));
 
     /* Drop pixmap reference */
     if (vblank->pixmap)