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drm/i915: Fix races on fbdev

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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
This commit is contained in:
Lukas Wunner 2016-03-09 12:52:53 +01:00 committed by Daniel Vetter
parent 5833498964
commit a7442b93cf
2 changed files with 6 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
drivers/gpu/drm/i915/i915_dma.c
View File

@ -493,11 +493,9 @@ static int i915_load_modeset_init(struct drm_device *dev)
* Some ports require correctly set-up hpd registers for detection to
* work properly (leading to ghost connected connector status), e.g. VGA
* on gm45. Hence we can only set up the initial fbdev config after hpd
* irqs are fully enabled. Now we should scan for the initial config
* only once hotplug handling is enabled, but due to screwed-up locking
* around kms/fbdev init we can't protect the fdbev initial config
* scanning against hotplug events. Hence do this first and ignore the
* tiny window where we will loose hotplug notifactions.
* irqs are fully enabled. We protect the fbdev initial config scanning
* against hotplug events by waiting in intel_fbdev_output_poll_changed
* until the asynchronous thread has finished.
*/
intel_fbdev_initial_config_async(dev);

3
drivers/gpu/drm/i915/intel_fbdev.c
View File

@ -808,6 +808,8 @@ void intel_fbdev_set_suspend(struct drm_device *dev, int state, bool synchronous
void intel_fbdev_output_poll_changed(struct drm_device *dev)
{
struct drm_i915_private *dev_priv = dev->dev_private;
async_synchronize_full();
if (dev_priv->fbdev)
drm_fb_helper_hotplug_event(&dev_priv->fbdev->helper);
}
@ -819,6 +821,7 @@ void intel_fbdev_restore_mode(struct drm_device *dev)
struct intel_fbdev *ifbdev = dev_priv->fbdev;
struct drm_fb_helper *fb_helper;
async_synchronize_full();
if (!ifbdev)
return;