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

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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
This commit is contained in:
Chris Wilson 2020-01-28 17:16:14 +00:00
parent ba12993c52
commit 8a5746982e
1 changed files with 1 additions and 1 deletions
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2
drivers/gpu/drm/i915/gt/intel_lrc.c
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@ -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();