From 68eb4ccc96da66116ccac4679b34c606e078119c Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Fri, 7 Feb 2020 11:02:13 +0000 Subject: [PATCH] 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: 7de814b5692e ("drm/i915/gt: Allow temporary suspension of inflight requests") Signed-off-by: Chris Wilson Cc: Tvrtko Ursulin Cc: Mika Kuoppala Reviewed-by: Mika Kuoppala Link: https://patchwork.freedesktop.org/patch/msgid/20200207110213.2734386-1-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/gt/intel_lrc.c | 11 ++++++++--- drivers/gpu/drm/i915/i915_scheduler.c | 2 +- 2 files changed, 9 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c index 9808244cb8feb..77bd8d8c027ea 100644 --- a/drivers/gpu/drm/i915/gt/intel_lrc.c +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c @@ -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); diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c index 34b654b4e58af..e19a37a83397e 100644 --- a/drivers/gpu/drm/i915/i915_scheduler.c +++ b/drivers/gpu/drm/i915/i915_scheduler.c @@ -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); /* -- 2.39.5