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: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20180625054741.3919-1-dhinakaran.pandiyan@intel.com
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