This commit causes a hang while running kms suspend tests (kms_pipe_crc_basic@suspend-read-crc-pipe-*) on ILK/SNB/IVB, affecting CI.

Probably the same problem with the one in v2, but on older HW.


commit a7442b93cf32c1e1ddb721a26cd1f92302e2a222
Author: Lukas Wunner <lu...@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 Fägerlind <gustav.fagerl...@gmail.com>
    Reported-by: "Li, Weinan Z" <weinan.z...@intel.com>
    Cc: Chris Wilson <ch...@chris-wilson.co.uk>
    Cc: sta...@vger.kernel.org
    Signed-off-by: Lukas Wunner <lu...@wunner.de>
    Signed-off-by: Daniel Vetter <daniel.vet...@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20160309115147.67b2b6e...@gabe.freedesktop.org


Regards,
Gabriel
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