drm/i915: Fix races on fbdev
authorLukas Wunner <lukas@wunner.de>
Wed, 9 Mar 2016 11:52:53 +0000 (12:52 +0100)
committerDaniel Vetter <daniel.vetter@ffwll.ch>
Wed, 30 Mar 2016 06:23:41 +0000 (08:23 +0200)
commita7442b93cf32c1e1ddb721a26cd1f92302e2a222
treeed0e8f9b8cf0a4b151dacbf94c1e9f608e8ca3f5
parent583349896482ed1d6af3cd75b2a15bb334df2777
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.fagerlind@gmail.com>
Reported-by: "Li, Weinan Z" <weinan.z.li@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@vger.kernel.org
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20160309115147.67B2B6E0D3@gabe.freedesktop.org
drivers/gpu/drm/i915/i915_dma.c
drivers/gpu/drm/i915/intel_fbdev.c