[Intel-gfx] [REGRESSION] system hang on ILK/SNB/IVB

Daniel Vetter daniel at ffwll.ch
Wed Mar 30 18:47:12 UTC 2016

On Wed, Mar 30, 2016 at 08:20:26PM +0300, Gabriel Feceoru wrote:
> This commit causes a hang while running kms suspend tests
> (kms_pipe_crc_basic at suspend-read-crc-pipe-*) on ILK/SNB/IVB, affecting CI.
> Probably the same problem with the one in v2, but on older HW.

I did check the patchwork/BAT-CI results and it looked clean. Is this a
new machine? Should I just revert for now until we have a proper fix?

> commit a7442b93cf32c1e1ddb721a26cd1f92302e2a222
> Author: Lukas Wunner <lukas at wunner.de>
> Date:   Wed Mar 9 12:52:53 2016 +0100
>     drm/i915: Fix races on fbdev
>     The ->lastclose callback invokes intel_fbdev_restore_mode() and has
>     been witnessed to run before intel_fbdev_initial_config_async()
>     has finished.
>     We might likewise receive hotplug events before we've had a chance to
>     fully set up the fbdev.
>     Fix by waiting for the asynchronous thread to finish.
>     v2:
>     An async_synchronize_full() was also added to intel_fbdev_set_suspend()
>     in v1 which turned out to be entirely gratuitous. It caused a deadlock
>     on suspend (discovered by CI, thanks to Damien Lespiau and Tomi Sarvela
>     for CI support) and was unnecessary since a device is never suspended
>     until its ->probe callback (and all asynchronous tasks it scheduled)
>     have finished. See dpm_prepare(), which calls wait_for_device_probe(),
>     which calls async_synchronize_full().
>     Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93580
>     Reported-by: Gustav F├Ągerlind <gustav.fagerlind at gmail.com>
>     Reported-by: "Li, Weinan Z" <weinan.z.li at intel.com>
>     Cc: Chris Wilson <chris at chris-wilson.co.uk>
>     Cc: stable at vger.kernel.org
>     Signed-off-by: Lukas Wunner <lukas at wunner.de>
>     Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
>     Link: http://patchwork.freedesktop.org/patch/msgid/20160309115147.67B2B6E0D3@gabe.freedesktop.org
> Regards,
> Gabriel

Daniel Vetter
Software Engineer, Intel Corporation

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