[Bug 93992] New: Xorg stuck in Uninterruptible IO state after a crash

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=93992

            Bug ID: 93992
           Summary: Xorg stuck in Uninterruptible IO state after a crash
           Product: xorg
           Version: 7.7 (2012.06)
          Hardware: x86 (IA32)
                OS: Linux (All)
            Status: NEW
          Severity: major
          Priority: medium
         Component: Driver/intel
          Assignee: chris at chris-wilson.co.uk
          Reporter: franck.delache at grassvalley.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org

On a fresh boot, the first time I start the XServer it crashes with the
following fatal server error:
[    13.722] (EE) xf86OpenConsole: VT_ACTIVATE failed: Input/output error
[    13.723] (EE) 
[    13.723] (EE) 

It did not cause me much trouble, since systemd will restart the XServer
automatically, and it is transparent for me (the crash happens very early
during boot-up).

Now I had one situation, where the XServer didn't terminate after the same
crash. I see the same fatal server error in the Xorg.0.log file, but the Xorg
process is stuck in Ds state (uninterruptible IO wait), and will never die.
Since the process is not dead, systemd will never try to restart the XServer.
Which is more problematic.

I tried to attach gdb on the Xorg process with no luck (as if gdb wait for the
process to get out of the Ds state). strace does the same thing.

The only information I can get is the main thread stack through
/proc/pid/stack:
root at kxslot12:~# cat /proc/1858/stack 
[<c138b085>] __drm_modeset_lock_all+0xf5/0x100
[<c138b09a>] drm_modeset_lock_all+0xa/0x30
[<c136fa4b>] drm_fb_helper_restore_fbdev_mode_unlocked+0x1b/0x70
[<c13f2f68>] intel_fbdev_restore_mode+0x18/0x40
[<c1415095>] i915_driver_lastclose+0x35/0x40
[<c1373365>] drm_lastclose+0x25/0x110
[<c13736e7>] drm_release+0x297/0x460
[<c1125ef3>] __fput+0xc3/0x1b0
[<c1126018>] ____fput+0x8/0x10
[<c10595a9>] task_work_run+0x79/0x90
[<c1045d3d>] do_exit+0x26d/0x990
[<c104654f>] do_group_exit+0x2f/0x90
[<c104f5d2>] get_signal+0x182/0x590
[<c1001a09>] do_signal+0x19/0x980
[<c10023c5>] do_notify_resume+0x55/0x70
[<c17574b7>] work_notifysig+0x24/0x29
[<ffffffff>] 0xffffffff

Note that this problem happens on an Intel Corporation 3rd Gen Core processor
Graphics Controller. I tried to reproduce this with different graphic
controller (915GM and 945GM) but couldn't.

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