drm/i915: Flush the execution-callbacks on retiring

In the unlikely case the request completes while we regard it as not even
executing on the GPU (see the next patch!), we have to flush any pending
execution callbacks at retirement and ensure that we do not add any
more.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190618074153.16055-4-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_request.c

@@ -119,6 +119,50 @@ const struct dma_fence_ops i915_fence_ops = {
 	.release = i915_fence_release,
 };
 
+static void irq_execute_cb(struct irq_work *wrk)
+{
+	struct execute_cb *cb = container_of(wrk, typeof(*cb), work);
+
+	i915_sw_fence_complete(cb->fence);
+	kmem_cache_free(global.slab_execute_cbs, cb);
+}
+
+static void irq_execute_cb_hook(struct irq_work *wrk)
+{
+	struct execute_cb *cb = container_of(wrk, typeof(*cb), work);
+
+	cb->hook(container_of(cb->fence, struct i915_request, submit),
+		 &cb->signal->fence);
+	i915_request_put(cb->signal);
+
+	irq_execute_cb(wrk);
+}
+
+static void __notify_execute_cb(struct i915_request *rq)
+{
+	struct execute_cb *cb;
+
+	lockdep_assert_held(&rq->lock);
+
+	if (list_empty(&rq->execute_cb))
+		return;
+
+	list_for_each_entry(cb, &rq->execute_cb, link)
+		irq_work_queue(&cb->work);
+
+	/*
+	 * XXX Rollback on __i915_request_unsubmit()
+	 *
+	 * In the future, perhaps when we have an active time-slicing scheduler,
+	 * it will be interesting to unsubmit parallel execution and remove
+	 * busywaits from the GPU until their master is restarted. This is
+	 * quite hairy, we have to carefully rollback the fence and do a
+	 * preempt-to-idle cycle on the target engine, all the while the
+	 * master execute_cb may refire.
+	 */
+	INIT_LIST_HEAD(&rq->execute_cb);
+}
+
 static inline void
 i915_request_remove_from_client(struct i915_request *request)
 {
@@ -246,6 +290,11 @@ static bool i915_request_retire(struct i915_request *rq)
 		GEM_BUG_ON(!atomic_read(&rq->i915->gt_pm.rps.num_waiters));
 		atomic_dec(&rq->i915->gt_pm.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(!list_empty(&rq->execute_cb));
 	spin_unlock(&rq->lock);
 
 	local_irq_enable();
@@ -285,50 +334,6 @@ void i915_request_retire_upto(struct i915_request *rq)
 	} while (i915_request_retire(tmp) && tmp != rq);
 }
 
-static void irq_execute_cb(struct irq_work *wrk)
-{
-	struct execute_cb *cb = container_of(wrk, typeof(*cb), work);
-
-	i915_sw_fence_complete(cb->fence);
-	kmem_cache_free(global.slab_execute_cbs, cb);
-}
-
-static void irq_execute_cb_hook(struct irq_work *wrk)
-{
-	struct execute_cb *cb = container_of(wrk, typeof(*cb), work);
-
-	cb->hook(container_of(cb->fence, struct i915_request, submit),
-		 &cb->signal->fence);
-	i915_request_put(cb->signal);
-
-	irq_execute_cb(wrk);
-}
-
-static void __notify_execute_cb(struct i915_request *rq)
-{
-	struct execute_cb *cb;
-
-	lockdep_assert_held(&rq->lock);
-
-	if (list_empty(&rq->execute_cb))
-		return;
-
-	list_for_each_entry(cb, &rq->execute_cb, link)
-		irq_work_queue(&cb->work);
-
-	/*
-	 * XXX Rollback on __i915_request_unsubmit()
-	 *
-	 * In the future, perhaps when we have an active time-slicing scheduler,
-	 * it will be interesting to unsubmit parallel execution and remove
-	 * busywaits from the GPU until their master is restarted. This is
-	 * quite hairy, we have to carefully rollback the fence and do a
-	 * preempt-to-idle cycle on the target engine, all the while the
-	 * master execute_cb may refire.
-	 */
-	INIT_LIST_HEAD(&rq->execute_cb);
-}
-
 static int
 __i915_request_await_execution(struct i915_request *rq,
 			       struct i915_request *signal,