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Once a device is disabled, it doesn't have a sprite pointer anymore. If an event is still in the queue and processed after DisableDevice finished, a dereference causes a crash. Example backtrace (crash forced by injecting an event at the right time): (EE) 0: /opt/xorg/bin/Xorg (OsSigHandler+0x3c) [0x48d334] (EE) 1: /lib64/libpthread.so.0 (__restore_rt+0x0) [0x37fcc0f74f] (EE) 2: /opt/xorg/bin/Xorg (mieqMoveToNewScreen+0x38) [0x609240] (EE) 3: /opt/xorg/bin/Xorg (mieqProcessDeviceEvent+0xd4) [0x609389] (EE) 4: /opt/xorg/bin/Xorg (mieqProcessInputEvents+0x206) [0x609720] (EE) 5: /opt/xorg/bin/Xorg (ProcessInputEvents+0xd) [0x4aeb58] (EE) 6: /opt/xorg/bin/Xorg (xf86VTSwitch+0x1a6) [0x4af457] (EE) 7: /opt/xorg/bin/Xorg (xf86Wakeup+0x2bf) [0x4af0a7] (EE) 8: /opt/xorg/bin/Xorg (WakeupHandler+0x83) [0x4445cb] (EE) 9: /opt/xorg/bin/Xorg (WaitForSomething+0x3fe) [0x491bf6] (EE) 10: /opt/xorg/bin/Xorg (Dispatch+0x97) [0x435748] (EE) 11: /opt/xorg/bin/Xorg (dix_main+0x61d) [0x4438a9] (EE) 12: /opt/xorg/bin/Xorg (main+0x28) [0x49ba28] (EE) 13: /lib64/libc.so.6 (__libc_start_main+0xf5) [0x37fc821d65] (EE) 14: /opt/xorg/bin/Xorg (_start+0x29) [0x425e69] (EE) 15: ? (?+0x29) [0x29] xf86VTSwitch() calls ProcessInputEvents() before disabling a device, and DisableDevice() calls mieqProcessInputEvents() again when flushing touches and button events. Between that and disabling the device (which causes new events to be refused) there is a window where events may be triggered and enqueued. On the next call to PIE that event is processed on a now defunct device, causing the crash. The simplest fix to this is to discard events from disabled devices. We flush the queue often enough before disabling that when we get here, we really don't care about the events from this device. X.Org Bug 77884 <http://bugs.freedesktop.org/show_bug.cgi?id=77884> Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net> Reported-by: Maarten Lankhorst <maarten.lankhorst@canonical.com> Tested-by: Maarten Lankhorst <maarten.lankhorst@canonical.com> Reviewed-by: Keith Packard <keithp@keithp.com> Signed-off-by: Keith Packard <keithp@keithp.com>
X Server
The X server accepts requests from client applications to create windows,
which are (normally rectangular) "virtual screens" that the client program
can draw into.
Windows are then composed on the actual screen by the X server
(or by a separate composite manager) as directed by the window manager,
which usually communicates with the user via graphical controls such as buttons
and draggable titlebars and borders.
For a comprehensive overview of X Server and X Window System, consult the
following article:
http://en.wikipedia.org/wiki/X_server
All questions regarding this software should be directed at the
Xorg mailing list:
http://lists.freedesktop.org/mailman/listinfo/xorg
Please submit bug reports to the Xorg bugzilla:
https://bugs.freedesktop.org/enter_bug.cgi?product=xorg
The master development code repository can be found at:
git://anongit.freedesktop.org/git/xorg/xserver
http://cgit.freedesktop.org/xorg/xserver
For patch submission instructions, see:
http://www.x.org/wiki/Development/Documentation/SubmittingPatches
For more information on the git code manager, see:
http://wiki.x.org/wiki/GitPage