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Commit a5cae7b8 authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915/breadcrumbs: Disable interrupt bottom-half first on idling 



Before walking the rbtree of waiters (marking them as complete and waking
them), decouple the interrupt handler. This prevents a race between the
missed waiter waking up and removing its intel_wait (which skips
checking the lock) and the interrupt handler dereferencing the
intel_wait. (Though we do not expect to encounter waiters during idle!)

Fixes: e1c0c91b ("drm/i915: Wake up all waiters before idling")
Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170315210726.12095-3-chris@chris-wilson.co.uk
parent 429732e8

drivers/gpu/drm/i915/intel_breadcrumbs.c

+8 −7
Original line number Diff line number Diff line
@@ -179,7 +179,7 @@ void __intel_engine_disarm_breadcrumbs(struct intel_engine_cs *engine) 
void intel_engine_disarm_breadcrumbs(struct intel_engine_cs *engine)

{

	struct intel_breadcrumbs *b = &engine->breadcrumbs;

	struct intel_wait *wait, *n;

	struct intel_wait *wait, *n, *first;



	if (!b->irq_armed)

		return;
@@ -190,18 +190,19 @@ void intel_engine_disarm_breadcrumbs(struct intel_engine_cs *engine) 
	 */



	spin_lock_irq(&b->rb_lock);



	spin_lock(&b->irq_lock);

	first = fetch_and_zero(&b->irq_wait);

	__intel_engine_disarm_breadcrumbs(engine);

	spin_unlock(&b->irq_lock);



	rbtree_postorder_for_each_entry_safe(wait, n, &b->waiters, node) {

		RB_CLEAR_NODE(&wait->node);

		if (wake_up_process(wait->tsk) && wait == b->irq_wait)

		if (wake_up_process(wait->tsk) && wait == first)

			missed_breadcrumb(engine);

	}

	b->waiters = RB_ROOT;



	spin_lock(&b->irq_lock);

	b->irq_wait = NULL;

	__intel_engine_disarm_breadcrumbs(engine);

	spin_unlock(&b->irq_lock);



	spin_unlock_irq(&b->rb_lock);

}