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drm/i915: Don't disable interrupts independently of the lock

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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.
Chris Wilson confirmed that local_irq_disable() was just introduced as
an optimisation to avoid enabling/disabling interrupts during
lock/unlock combo.

Enable/disable interrupts as part of the locking instruction.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20191017161352.e5z3ugse7gxl5ari@linutronix.de
This commit is contained in:
Sebastian Andrzej Siewior 2019-10-17 18:13:52 +02:00 committed by Chris Wilson
parent e9768bfe87
commit 1dfffa0051
1 changed files with 4 additions and 8 deletions
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12
drivers/gpu/drm/i915/i915_request.c
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@ -206,14 +206,14 @@ static void remove_from_engine(struct i915_request *rq)
* check that the rq still belongs to the newly locked engine.
*/
locked = READ_ONCE(rq->engine);
spin_lock(&locked->active.lock);
spin_lock_irq(&locked->active.lock);
while (unlikely(locked != (engine = READ_ONCE(rq->engine)))) {
spin_unlock(&locked->active.lock);
spin_lock(&engine->active.lock);
locked = engine;
}
list_del(&rq->sched.link);
spin_unlock(&locked->active.lock);
spin_unlock_irq(&locked->active.lock);
}
bool i915_request_retire(struct i915_request *rq)
@ -242,8 +242,6 @@ bool i915_request_retire(struct i915_request *rq)
&i915_request_timeline(rq)->requests));
rq->ring->head = rq->postfix;
local_irq_disable();
/*
* We only loosely track inflight requests across preemption,
* and so we may find ourselves attempting to retire a _completed_
@ -252,7 +250,7 @@ bool i915_request_retire(struct i915_request *rq)
*/
remove_from_engine(rq);
spin_lock(&rq->lock);
spin_lock_irq(&rq->lock);
i915_request_mark_complete(rq);
if (!i915_request_signaled(rq))
dma_fence_signal_locked(&rq->fence);
@ -267,9 +265,7 @@ bool i915_request_retire(struct i915_request *rq)
__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);