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From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org,
	linux-rt-users <linux-rt-users@vger.kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Carsten Emde <C.Emde@osadl.org>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	John Kacur <jkacur@redhat.com>,
	Paul Gortmaker <paul.gortmaker@windriver.com>,
	Julia Cartwright <julia@ni.com>,
	Daniel Wagner <daniel.wagner@siemens.com>,
	tom.zanussi@linux.intel.com
Subject: [PATCH RT 4/6] drm/i915: Dont disable interrupts independently of the lock
Date: Fri, 24 May 2019 23:32:36 -0400	[thread overview]
Message-ID: <20190525033315.775106086@goodmis.org> (raw)
In-Reply-To: 20190525033232.795741612@goodmis.org

4.19.37-rt20-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

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>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 drivers/gpu/drm/i915/i915_request.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index 5c2c93cbab12..7124510b9131 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -356,9 +356,7 @@ static void __retire_engine_request(struct intel_engine_cs *engine,
 
 	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);
@@ -372,9 +370,7 @@ static void __retire_engine_request(struct intel_engine_cs *engine,
 		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
-- 
2.20.1



  parent reply	other threads:[~2019-05-25  3:33 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-25  3:32 [PATCH RT 0/6] Linux 4.19.37-rt20-rc1 Steven Rostedt
2019-05-25  3:32 ` [PATCH RT 1/6] powerpc/pseries/iommu: Use a locallock instead local_irq_save() Steven Rostedt
2019-05-25  3:32 ` [PATCH RT 2/6] powerpc: reshuffle TIF bits Steven Rostedt
2019-05-25  3:32 ` [PATCH RT 3/6] tty/sysrq: Convert show_lock to raw_spinlock_t Steven Rostedt
2019-05-25  3:32 ` Steven Rostedt [this message]
2019-05-25  3:32 ` [PATCH RT 5/6] sched/completion: Fix a lockup in wait_for_completion() Steven Rostedt
2019-05-25  3:32 ` [PATCH RT 6/6] Linux 4.19.37-rt20-rc1 Steven Rostedt

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