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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 10 Apr 2019 11:01:37 +0200
Subject: [PATCH] drm/i915: Don't disable interrupts independently of the
lock
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.2/older/patches-5.2.10-rt5.tar.xz
The locks (timeline->lock and rq->lock) need to be taken with disabled
interrupts. This is done in __retire_engine_request() 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 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@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
@@ -202,9 +202,7 @@ static void __retire_engine_request(stru
GEM_BUG_ON(!i915_request_completed(rq));
- local_irq_disable();
-
- spin_lock(&engine->timeline.lock);
+ spin_lock_irq(&engine->timeline.lock);
GEM_BUG_ON(!list_is_first(&rq->link, &engine->timeline.requests));
list_del_init(&rq->link);
spin_unlock(&engine->timeline.lock);
@@ -219,9 +217,7 @@ static void __retire_engine_request(stru
GEM_BUG_ON(!atomic_read(&rq->i915->gt_pm.rps.num_waiters));
atomic_dec(&rq->i915->gt_pm.rps.num_waiters);
}
- spin_unlock(&rq->lock);
-
- local_irq_enable();
+ spin_unlock_irq(&rq->lock);
/*
* The backing object for the context is done after switching to the
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