Commit 8a574698 authored Jan 28, 2020 by Chris Wilson

drm/i915/execlist: Mark up racy read of execlists->pending[0]



We write to execlists->pending[0] in process_csb() to acknowledge the
completion of the ESLP update, outside of the main spinlock. When we
check the current status of the previous submission in
__execlists_submission_tasklet() we should therefore use READ_ONCE() to
reflect and document the unsynchronized read.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200128171614.3845825-1-chris@chris-wilson.co.uk

parent ba12993c

drivers/gpu/drm/i915/gt/intel_lrc.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -2347,7 +2347,7 @@ static void process_csb(struct intel_engine_cs *engine)
		static void __execlists_submission_tasklet(struct intel_engine_cs *const engine)
		{
		lockdep_assert_held(&engine->active.lock);
		if (!engine->execlists.pending[0]) {
		if (!READ_ONCE(engine->execlists.pending[0])) {
		rcu_read_lock(); /* protect peeking at execlists->active */
		execlists_dequeue(engine);
		rcu_read_unlock();

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