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Commit b66255f0 authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915: Refactor wakeup of the next breadcrumb waiter 



Refactor the common task of updating the first_waiter, serialised with
the interrupt handler. When we update the first_waiter, we also need to
wakeup the new bottom-half in order to complete the actions that we may
have delegated to it (such as checking the irq-seqno coherency or waking
up other lower priority concurrent waiters).

Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: default avatarMika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170303171422.4735-1-chris@chris-wilson.co.uk
parent 24754d75

drivers/gpu/drm/i915/intel_breadcrumbs.c

+18 −30
Original line number Diff line number Diff line
@@ -287,6 +287,22 @@ static inline void __intel_breadcrumbs_finish(struct intel_breadcrumbs *b, 
	wake_up_process(wait->tsk); /* implicit smp_wmb() */

}



static inline void __intel_breadcrumbs_next(struct intel_engine_cs *engine,

					    struct rb_node *next)

{

	struct intel_breadcrumbs *b = &engine->breadcrumbs;



	GEM_BUG_ON(!b->irq_armed);

	b->first_wait = to_wait(next);



	/* We always wake up the next waiter that takes over as the bottom-half

	 * as we may delegate not only the irq-seqno barrier to the next waiter

	 * but also the task of waking up concurrent waiters.

	 */

	if (next)

		wake_up_process(to_wait(next)->tsk);

}



static bool __intel_engine_add_wait(struct intel_engine_cs *engine,

				    struct intel_wait *wait)

{
@@ -357,21 +373,7 @@ static bool __intel_engine_add_wait(struct intel_engine_cs *engine, 
		GEM_BUG_ON(!next && !first);

		if (next && next != &wait->node) {

			GEM_BUG_ON(first);

			b->first_wait = to_wait(next);

			/* As there is a delay between reading the current

			 * seqno, processing the completed tasks and selecting

			 * the next waiter, we may have missed the interrupt

			 * and so need for the next bottom-half to wakeup.

			 *

			 * Also as we enable the IRQ, we may miss the

			 * interrupt for that seqno, so we have to wake up

			 * the next bottom-half in order to do a coherent check

			 * in case the seqno passed.

			 */

			__intel_breadcrumbs_enable_irq(b);

			if (test_bit(ENGINE_IRQ_BREADCRUMB,

				     &engine->irq_posted))

				wake_up_process(to_wait(next)->tsk);

			__intel_breadcrumbs_next(engine, next);

		}



		do {
@@ -473,21 +475,7 @@ static void __intel_engine_remove_wait(struct intel_engine_cs *engine, 
			}

		}



		if (next) {

			/* In our haste, we may have completed the first waiter

			 * before we enabled the interrupt. Do so now as we

			 * have a second waiter for a future seqno. Afterwards,

			 * we have to wake up that waiter in case we missed

			 * the interrupt, or if we have to handle an

			 * exception rather than a seqno completion.

			 */

			b->first_wait = to_wait(next);

			if (b->first_wait->seqno != wait->seqno)

				__intel_breadcrumbs_enable_irq(b);

			wake_up_process(b->first_wait->tsk);

		} else {

			b->first_wait = NULL;

		}

		__intel_breadcrumbs_next(engine, next);

	} else {

		GEM_BUG_ON(rb_first(&b->waiters) == &wait->node);

	}