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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
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2 changed files with 6 additions and 5 deletions
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@ -493,11 +493,9 @@ static int i915_load_modeset_init(struct drm_device *dev)
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* Some ports require correctly set-up hpd registers for detection to
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* work properly (leading to ghost connected connector status), e.g. VGA
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* on gm45. Hence we can only set up the initial fbdev config after hpd
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* irqs are fully enabled. Now we should scan for the initial config
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* only once hotplug handling is enabled, but due to screwed-up locking
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* around kms/fbdev init we can't protect the fdbev initial config
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* scanning against hotplug events. Hence do this first and ignore the
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* tiny window where we will loose hotplug notifactions.
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* irqs are fully enabled. We protect the fbdev initial config scanning
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* against hotplug events by waiting in intel_fbdev_output_poll_changed
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* until the asynchronous thread has finished.
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*/
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intel_fbdev_initial_config_async(dev);
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@ -808,6 +808,8 @@ void intel_fbdev_set_suspend(struct drm_device *dev, int state, bool synchronous
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void intel_fbdev_output_poll_changed(struct drm_device *dev)
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{
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struct drm_i915_private *dev_priv = dev->dev_private;
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async_synchronize_full();
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if (dev_priv->fbdev)
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drm_fb_helper_hotplug_event(&dev_priv->fbdev->helper);
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}
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@ -819,6 +821,7 @@ void intel_fbdev_restore_mode(struct drm_device *dev)
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struct intel_fbdev *ifbdev = dev_priv->fbdev;
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struct drm_fb_helper *fb_helper;
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async_synchronize_full();
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if (!ifbdev)
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return;
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