diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c index af2f78e040d7..a59b803aef92 100644 --- a/drivers/gpu/drm/i915/i915_request.c +++ b/drivers/gpu/drm/i915/i915_request.c @@ -756,34 +756,37 @@ err_unlock: static int i915_request_await_start(struct i915_request *rq, struct i915_request *signal) { - struct intel_timeline *tl; struct dma_fence *fence; int err; GEM_BUG_ON(i915_request_timeline(rq) == rcu_access_pointer(signal->timeline)); + fence = NULL; rcu_read_lock(); - tl = rcu_dereference(signal->timeline); - if (i915_request_started(signal) || !kref_get_unless_zero(&tl->kref)) - tl = NULL; - rcu_read_unlock(); - if (!tl) /* already started or maybe even completed */ - return 0; + spin_lock_irq(&signal->lock); + if (!i915_request_started(signal) && + !list_is_first(&signal->link, + &rcu_dereference(signal->timeline)->requests)) { + struct i915_request *prev = list_prev_entry(signal, link); - fence = ERR_PTR(-EAGAIN); - if (mutex_trylock(&tl->mutex)) { - fence = NULL; - if (!i915_request_started(signal) && - !list_is_first(&signal->link, &tl->requests)) { - signal = list_prev_entry(signal, link); - fence = dma_fence_get(&signal->fence); + /* + * Peek at the request before us in the timeline. That + * request will only be valid before it is retired, so + * after acquiring a reference to it, confirm that it is + * still part of the signaler's timeline. + */ + if (i915_request_get_rcu(prev)) { + if (list_next_entry(prev, link) == signal) + fence = &prev->fence; + else + i915_request_put(prev); } - mutex_unlock(&tl->mutex); } - intel_timeline_put(tl); - if (IS_ERR_OR_NULL(fence)) - return PTR_ERR_OR_ZERO(fence); + spin_unlock_irq(&signal->lock); + rcu_read_unlock(); + if (!fence) + return 0; err = 0; if (intel_timeline_sync_is_later(i915_request_timeline(rq), fence))