We are using the i915_request.lock to serialise adding an execution callback with __i915_request_submit. However, if we use an atomic llist_add to serialise multiple waiters and then check to see if the request is already executing, we can remove the irq-spinlock.
Signed-off-by: Chris Wilson <[email protected]> --- drivers/gpu/drm/i915/i915_request.c | 37 +++++++---------------------- 1 file changed, 8 insertions(+), 29 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c index 0b2fe55e6194..7a287358785d 100644 --- a/drivers/gpu/drm/i915/i915_request.c +++ b/drivers/gpu/drm/i915/i915_request.c @@ -190,13 +190,11 @@ static void __notify_execute_cb(struct i915_request *rq) { struct execute_cb *cb, *cn; - lockdep_assert_held(&rq->lock); - - GEM_BUG_ON(!i915_request_is_active(rq)); if (llist_empty(&rq->execute_cb)) return; - llist_for_each_entry_safe(cb, cn, rq->execute_cb.first, work.llnode) + llist_for_each_entry_safe(cb, cn, + llist_del_all(&rq->execute_cb), work.llnode) irq_work_queue(&cb->work); /* @@ -209,7 +207,6 @@ static void __notify_execute_cb(struct i915_request *rq) * preempt-to-idle cycle on the target engine, all the while the * master execute_cb may refire. */ - init_llist_head(&rq->execute_cb); } static inline void @@ -323,12 +320,8 @@ bool i915_request_retire(struct i915_request *rq) GEM_BUG_ON(!atomic_read(&rq->engine->gt->rps.num_waiters)); atomic_dec(&rq->engine->gt->rps.num_waiters); } - if (!test_bit(I915_FENCE_FLAG_ACTIVE, &rq->fence.flags)) { - set_bit(I915_FENCE_FLAG_ACTIVE, &rq->fence.flags); - __notify_execute_cb(rq); - } - GEM_BUG_ON(!llist_empty(&rq->execute_cb)); spin_unlock_irq(&rq->lock); + __notify_execute_cb(rq); remove_from_client(rq); __list_del_entry(&rq->link); /* poison neither prev/next (RCU walks) */ @@ -357,12 +350,6 @@ void i915_request_retire_upto(struct i915_request *rq) } while (i915_request_retire(tmp) && tmp != rq); } -static void __llist_add(struct llist_node *node, struct llist_head *head) -{ - node->next = head->first; - head->first = node; -} - static struct i915_request * const * __engine_active(struct intel_engine_cs *engine) { @@ -439,18 +426,11 @@ __await_execution(struct i915_request *rq, cb->work.func = irq_execute_cb_hook; } - spin_lock_irq(&signal->lock); - if (i915_request_is_active(signal) || __request_in_flight(signal)) { - if (hook) { - hook(rq, &signal->fence); - i915_request_put(signal); - } - i915_sw_fence_complete(cb->fence); - kmem_cache_free(global.slab_execute_cbs, cb); - } else { - __llist_add(&cb->work.llnode, &signal->execute_cb); + if (llist_add(&cb->work.llnode, &signal->execute_cb)) { + if (i915_request_is_active(signal) || + __request_in_flight(signal)) + __notify_execute_cb(signal); } - spin_unlock_irq(&signal->lock); return 0; } @@ -565,19 +545,18 @@ bool __i915_request_submit(struct i915_request *request) list_move_tail(&request->sched.link, &engine->active.requests); clear_bit(I915_FENCE_FLAG_PQUEUE, &request->fence.flags); } + __notify_execute_cb(request); /* We may be recursing from the signal callback of another i915 fence */ if (!i915_request_signaled(request)) { spin_lock_nested(&request->lock, SINGLE_DEPTH_NESTING); - __notify_execute_cb(request); if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &request->fence.flags) && !i915_request_enable_breadcrumb(request)) intel_engine_signal_breadcrumbs(engine); spin_unlock(&request->lock); - GEM_BUG_ON(!llist_empty(&request->execute_cb)); } return result; -- 2.20.1 _______________________________________________ Intel-gfx mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/intel-gfx
