[Intel-gfx] [PATCH] drm/i915: Don't disable interrupts independently of the lock

[Sebastian Andrzej Siewior]

The locks (active.lock and rq->lock) need to be taken with disabled
interrupts. This is done in i915_request_retire() by disabling the
interrupts independently of the locks itself.
While local_irq_disable()+spin_lock() equals spin_lock_irq() on vanilla
it does not on PREEMPT_RT. Also, it is not obvious if there is a special reason
to why the interrupts are disabled independently of the lock.

Enable/disable interrupts as part of the locking instruction.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy at linutronix.de>
---
 drivers/gpu/drm/i915/i915_request.c |    8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

--- 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);
 
 	remove_from_client(rq);
 	list_del(&rq->link);