Quoting Sebastian Andrzej Siewior (2019-10-10 19:26:10)
On 2019-10-10 19:11:27 [+0100], Chris Wilson wrote:
--- a/drivers/gpu/drm/i915/i915_request.c +++ b/drivers/gpu/drm/i915/i915_request.c @@ -251,15 +251,13 @@ static bool i915_request_retire(struct i active->retire(active, rq); }
local_irq_disable();/* * We only loosely track inflight requests across preemption, * and so we may find ourselves attempting to retire a _completed_ * request that we have removed from the HW and put back on a run * queue. */spin_lock(&rq->engine->active.lock);
spin_lock_irq(&rq->engine->active.lock); list_del(&rq->sched.link); spin_unlock(&rq->engine->active.lock);@@ -278,9 +276,7 @@ static bool i915_request_retire(struct i __notify_execute_cb(rq); } GEM_BUG_ON(!list_empty(&rq->execute_cb));
spin_unlock(&rq->lock);local_irq_enable();
spin_unlock_irq(&rq->lock);Nothing screams about the imbalance? irq off from one lock to the other?
There is no imbalance, is there? Interrupts are disabled as part of acquiring the first lock and enabled again as part of releasing the second lock. It may not look beautiful.
Sure, it's at the same scope, I just expect at some point lockdep to complain :)
I'm just not sure if this
| spin_lock_irq(&rq->engine->active.lock); | list_del(&rq->sched.link); | spin_unlock_irq(&rq->engine->active.lock); | | spin_lock_irq(&rq->lock); | i915_request_mark_complete(rq); … | spin_unlock_irq(&rq->lock);
has been avoided because an interrupt here could change something or if this is just an optimisation.
Just avoiding the back-to-back enable/disable. -Chris