Commit c12e0643 authored by Dhinakaran Pandiyan's avatar Dhinakaran Pandiyan

drm/i915/psr: Fix race in intel_psr_work()

Commit 5422b37c ("drm/i915/psr: Kill delays when activating psr
back.") switched from delayed work to the plain variant and while doing so
removed the check for work_busy() before scheduling a PSR activation.
This appears to cause consecutive executions of psr_activate() in this
scenario - after a worker picks up the PSR work item for execution and
before the work function can acquire the PSR mutex, a psr_flush() can
get hold of the mutex and schedule another PSR work. Without a psr_exit()
between the two psr_activate() calls, warning messages get printed.
Further, since we drop the mutex in the midst of psr_work() to wait for
PSR to idle, another work item can also get scheduled. Fix this by
returning if PSR was already active.

Fixes: 5422b37c ("drm/i915/psr: Kill delays when activating psr back.")
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=106948
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: default avatarDhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Reviewed-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: default avatarRodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180625054741.3919-1-dhinakaran.pandiyan@intel.com
parent cf5d862d
......@@ -758,7 +758,7 @@ static void intel_psr_work(struct work_struct *work)
* recheck. Since psr_flush first clears this and then reschedules we
* won't ever miss a flush when bailing out here.
*/
if (dev_priv->psr.busy_frontbuffer_bits)
if (dev_priv->psr.busy_frontbuffer_bits || dev_priv->psr.active)
goto unlock;
intel_psr_activate(dev_priv->psr.enabled);
......
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