Commit 8a574698 authored by Chris Wilson's avatar 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: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: default avatarMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200128171614.3845825-1-chris@chris-wilson.co.uk
parent ba12993c
...@@ -2347,7 +2347,7 @@ static void process_csb(struct intel_engine_cs *engine) ...@@ -2347,7 +2347,7 @@ static void process_csb(struct intel_engine_cs *engine)
static void __execlists_submission_tasklet(struct intel_engine_cs *const engine) static void __execlists_submission_tasklet(struct intel_engine_cs *const engine)
{ {
lockdep_assert_held(&engine->active.lock); 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 */ rcu_read_lock(); /* protect peeking at execlists->active */
execlists_dequeue(engine); execlists_dequeue(engine);
rcu_read_unlock(); rcu_read_unlock();
......
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