Commit 793c2261 authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915/gt: Protect execlists_hold/unhold from new waiters 



As we may add new waiters to a request as it is being run, we need to
mark the list iteration as being safe for concurrent addition.

v2: Mika spotted that we used the same trick for signalers_list, so warn
the compiler about the lockless walk there as well.

Fixes: 32ff621f ("drm/i915/gt: Allow temporary suspension of inflight requests")
Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: default avatarMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200207110213.2734386-1-chris@chris-wilson.co.uk
parent 5eae8ca3

drivers/gpu/drm/i915/gt/intel_lrc.c

+8 −3
Original line number Diff line number Diff line
@@ -1620,6 +1620,11 @@ last_active(const struct intel_engine_execlists *execlists) 
				     &(rq__)->sched.waiters_list, \

				     wait_link)



#define for_each_signaler(p__, rq__) \

	list_for_each_entry_lockless(p__, \

				     &(rq__)->sched.signalers_list, \

				     signal_link)



static void defer_request(struct i915_request *rq, struct list_head * const pl)

{

	LIST_HEAD(list);
@@ -2378,7 +2383,7 @@ static void __execlists_hold(struct i915_request *rq) 
		list_move_tail(&rq->sched.link, &rq->engine->active.hold);

		i915_request_set_hold(rq);



		list_for_each_entry(p, &rq->sched.waiters_list, wait_link) {

		for_each_waiter(p, rq) {

			struct i915_request *w =

				container_of(p->waiter, typeof(*w), sched);
@@ -2464,7 +2469,7 @@ static bool hold_request(const struct i915_request *rq) 
	 * If one of our ancestors is on hold, we must also be on hold,

	 * otherwise we will bypass it and execute before it.

	 */

	list_for_each_entry(p, &rq->sched.signalers_list, signal_link) {

	for_each_signaler(p, rq) {

		const struct i915_request *s =

			container_of(p->signaler, typeof(*s), sched);
@@ -2496,7 +2501,7 @@ static void __execlists_unhold(struct i915_request *rq) 
		RQ_TRACE(rq, "hold release\n");



		/* Also release any children on this engine that are ready */

		list_for_each_entry(p, &rq->sched.waiters_list, wait_link) {

		for_each_waiter(p, rq) {

			struct i915_request *w =

				container_of(p->waiter, typeof(*w), sched);

drivers/gpu/drm/i915/i915_scheduler.c

+1 −1
Original line number Diff line number Diff line
@@ -433,7 +433,7 @@ bool __i915_sched_node_add_dependency(struct i915_sched_node *node, 
			node->flags |= I915_SCHED_HAS_SEMAPHORE_CHAIN;



		/* All set, now publish. Beware the lockless walkers. */

		list_add(&dep->signal_link, &node->signalers_list);

		list_add_rcu(&dep->signal_link, &node->signalers_list);

		list_add_rcu(&dep->wait_link, &signal->waiters_list);



		/*

CRA Git | Maintained and supported by SUSTech CRA and CCSE