[Bug 89035] New: zbarcam causes Xorg to hang when using a compositing window manager

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=89035

            Bug ID: 89035
           Summary: zbarcam causes Xorg to hang when using a compositing
                    window manager
           Product: DRI
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: lantw44 at gmail.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

When I run zbarcam with a non-compositing window manager, such as openbox and
xfwm with compositing disabled, it works mostly fine although it may cause the
kernel to show some error:

[drm:ilk_display_irq_handler] *ERROR* Pipe A FIFO underrun
[drm:cpt_set_fifo_underrun_reporting] *ERROR* uncleared pch fifo underrun on
pch transcoder A
[drm:cpt_serr_int_handler] *ERROR* PCH transcoder A FIFO underrun


When I run zbarcam with a compositing window manager, such as gnome-shell
(mutter) and xfwm with compositing enabled, it also shows the above error, but
it stops showing the video captured by the webcam and shows the zbar logo
instead after the window is moved. If I keep moving the window for more than 30
seconds, it causes Xorg to hang and it tells me to report the bug here. The
system may crash after showing the error.

[drm] stuck on render ring
[drm] GPU HANG: ecode 0:0x84fefffc, in Xorg.bin [1114], reason: Ring hung,
action: reset
[drm] GPU hangs can indicate a bug anywhere in the entire gfx stack, including
userspace.
[drm] Please file a _new_ bug report on bugs.freedesktop.org against DRI ->
DRM/Intel
[drm] drm/i915 developers can then reassign to the right component if it's not
a kernel issue.
[drm] The gpu crash dump is required to analyze gpu hangs, so please always
attach it.
[drm] GPU crash dump saved to /sys/class/drm/card0/error
[drm] stuck on render ring
[drm] GPU HANG: ecode 0:0x84fefffc, in Xorg.bin [1114], reason: Ring hung,
action: reset


Hardware:
Intel Core i7-2640M CPU @ 2.80GHz
Intel Sandybridge Mobile

Software:
Linux 3.18.5
Xorg 1.16.3
Mesa 10.4.3
xf86-video-intel 2.99.916

Window Managers:
GNOME Shell 3.14.3 (Mutter 3.14.3)
Openbox 3.5.2
Xfwm 4.10.1

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