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From: Chris Wilson <chris@chris-wilson.co.uk>
To: intel-gfx@lists.freedesktop.org
Subject: [PATCH 2/2] drm/i915: Protect request peeking with RCU
Date: Mon,  4 Nov 2019 09:01:58 +0000	[thread overview]
Message-ID: <20191104090158.2959-2-chris@chris-wilson.co.uk> (raw)
In-Reply-To: <20191104090158.2959-1-chris@chris-wilson.co.uk>

Since the execlists_active() is no longer protected by the
engine->active.lock, we need to protect the request pointer with RCU to
prevent it being freed as we evaluate whether or not we need to preempt.

Fixes: df403069029d ("drm/i915/execlists: Lift process_csb() out of the irq-off spinlock")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
---
 drivers/gpu/drm/i915/i915_scheduler.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c
index d2edb527dcb8..010d67f48ad9 100644
--- a/drivers/gpu/drm/i915/i915_scheduler.c
+++ b/drivers/gpu/drm/i915/i915_scheduler.c
@@ -202,21 +202,26 @@ static void kick_submission(struct intel_engine_cs *engine,
 	if (prio <= engine->execlists.queue_priority_hint)
 		return;
 
+	rcu_read_lock();
+
 	/* Nothing currently active? We're overdue for a submission! */
 	inflight = execlists_active(&engine->execlists);
 	if (!inflight)
-		return;
+		goto unlock;
 
 	/*
 	 * If we are already the currently executing context, don't
 	 * bother evaluating if we should preempt ourselves.
 	 */
 	if (inflight->hw_context == rq->hw_context)
-		return;
+		goto unlock;
 
 	engine->execlists.queue_priority_hint = prio;
 	if (need_preempt(prio, rq_prio(inflight)))
 		tasklet_hi_schedule(&engine->execlists.tasklet);
+
+unlock:
+	rcu_read_unlock();
 }
 
 static void __i915_schedule(struct i915_sched_node *node,
-- 
2.24.0.rc2

_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

WARNING: multiple messages have this Message-ID (diff)
From: Chris Wilson <chris@chris-wilson.co.uk>
To: intel-gfx@lists.freedesktop.org
Subject: [Intel-gfx] [PATCH 2/2] drm/i915: Protect request peeking with RCU
Date: Mon,  4 Nov 2019 09:01:58 +0000	[thread overview]
Message-ID: <20191104090158.2959-2-chris@chris-wilson.co.uk> (raw)
Message-ID: <20191104090158.uv6cI0IT4wHHU29yOwrn0Ug0MgnTIIYk1e4qtg4AQrs@z> (raw)
In-Reply-To: <20191104090158.2959-1-chris@chris-wilson.co.uk>

Since the execlists_active() is no longer protected by the
engine->active.lock, we need to protect the request pointer with RCU to
prevent it being freed as we evaluate whether or not we need to preempt.

Fixes: df403069029d ("drm/i915/execlists: Lift process_csb() out of the irq-off spinlock")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
---
 drivers/gpu/drm/i915/i915_scheduler.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c
index d2edb527dcb8..010d67f48ad9 100644
--- a/drivers/gpu/drm/i915/i915_scheduler.c
+++ b/drivers/gpu/drm/i915/i915_scheduler.c
@@ -202,21 +202,26 @@ static void kick_submission(struct intel_engine_cs *engine,
 	if (prio <= engine->execlists.queue_priority_hint)
 		return;
 
+	rcu_read_lock();
+
 	/* Nothing currently active? We're overdue for a submission! */
 	inflight = execlists_active(&engine->execlists);
 	if (!inflight)
-		return;
+		goto unlock;
 
 	/*
 	 * If we are already the currently executing context, don't
 	 * bother evaluating if we should preempt ourselves.
 	 */
 	if (inflight->hw_context == rq->hw_context)
-		return;
+		goto unlock;
 
 	engine->execlists.queue_priority_hint = prio;
 	if (need_preempt(prio, rq_prio(inflight)))
 		tasklet_hi_schedule(&engine->execlists.tasklet);
+
+unlock:
+	rcu_read_unlock();
 }
 
 static void __i915_schedule(struct i915_sched_node *node,
-- 
2.24.0.rc2

_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

  reply	other threads:[~2019-11-04  9:02 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-04  9:01 [PATCH 1/2] drm/i915/gt: Drop false assertion on user_forcewake Chris Wilson
2019-11-04  9:01 ` [Intel-gfx] " Chris Wilson
2019-11-04  9:01 ` Chris Wilson [this message]
2019-11-04  9:01   ` [Intel-gfx] [PATCH 2/2] drm/i915: Protect request peeking with RCU Chris Wilson
2019-11-04  9:59   ` Mika Kuoppala
2019-11-04  9:59     ` [Intel-gfx] " Mika Kuoppala
2019-11-04  9:38 ` [PATCH 1/2] drm/i915/gt: Drop false assertion on user_forcewake Mika Kuoppala
2019-11-04  9:38   ` [Intel-gfx] " Mika Kuoppala

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