drm/i915/execlists: Protect peeking at execlists->active
authorChris Wilson <chris@chris-wilson.co.uk>
Wed, 9 Oct 2019 10:09:54 +0000 (11:09 +0100)
committerChris Wilson <chris@chris-wilson.co.uk>
Wed, 9 Oct 2019 18:46:40 +0000 (19:46 +0100)
commitc949ae431467764277cdd88d7c26ff963a9db40a
tree46321fab5e4279e890276f0b44f48a9ebfd0c9e9
parent2a86972f60fcfaa0daa02b9fe461935ea2063791
drm/i915/execlists: Protect peeking at execlists->active

Now that we dropped the engine->active.lock serialisation from around
process_csb(), direct submission can run concurrently to the interrupt
handler. As such execlists->active may be advanced as we dequeue,
dropping the reference to the request. We need to employ our RCU request
protection to ensure that the request is not freed too early.

Fixes: df403069029d ("drm/i915/execlists: Lift process_csb() out of the irq-off spinlock")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191009100955.21477-1-chris@chris-wilson.co.uk
drivers/gpu/drm/i915/gt/intel_lrc.c