[Wayland-bugs] [Bug 108249] [xwayland] Crash in Xpresent code on resume from suspend

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=108249

--- Comment #1 from Olivier Fourdan <fourdan at xfce.org> ---
So, looking further into the backtrace, we see that:

(gdb) f 10
#10 present_wnmd_flip (damage=0xf4eee0, sync_flip=0, pixmap=0xf507a0,
target_msc=268904, event_id=1985548, crtc=0xaa85b0, 
    window=0xf4ee90) at present_wnmd.c:358
358         present_screen_priv_ptr     screen_priv =
present_screen_priv(screen);
(gdb) p screen
$2 = (ScreenPtr) 0xf000000000034

(that's a bogus value ^^^)

That's coming from:

 353                      PixmapPtr pixmap,
 354                      Bool sync_flip,
 355                      RegionPtr damage)
 356    {
 357        ScreenPtr                   screen = crtc->pScreen;
 358        present_screen_priv_ptr     screen_priv =
present_screen_priv(screen);
 359    

And so is the RRCrtcPtr:

(gdb) p *crtc
$5 = {id = 0, pScreen = 0xf000000000034, mode = 0x63736e552f6b6447, x =
1684368481, y = 4804676, ...

So my guess is that the undock removes outputs, on resume Xwayland gets all the
events at once, the xwl_present_sync_callback() occurs after the
xwl_output_remove() has destroyed the xwl_output->randr_crtc so we're pointeing
at freed memory here.

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