io_uring: refactor io_cqring_wake()

Instead of smp_mb() + __io_cqring_wake() in __io_cq_unlock_post_flush()
use equivalent io_cqring_wake(). With that we can clean it up further
and remove __io_cqring_wake().
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/662ee5d898168ac206be06038525e97b64072a46.1680782017.git.asml.silence@gmail.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/io_uring.c

@@ -640,10 +640,8 @@ static inline void __io_cq_unlock_post_flush(struct io_ring_ctx *ctx)
 	 * it will re-check the wakeup conditions once we return we can safely
 	 * skip waking it up.
 	 */
-	if (!(ctx->flags & IORING_SETUP_DEFER_TASKRUN)) {
-		smp_mb();
-		__io_cqring_wake(ctx);
-	}
+	if (!(ctx->flags & IORING_SETUP_DEFER_TASKRUN))
+		io_cqring_wake(ctx);
 }
 
 void io_cq_unlock_post(struct io_ring_ctx *ctx)

io_uring/io_uring.h

@@ -228,8 +228,7 @@ static inline void io_poll_wq_wake(struct io_ring_ctx *ctx)
 				poll_to_key(EPOLL_URING_WAKE | EPOLLIN));
 }
 
-/* requires smb_mb() prior, see wq_has_sleeper() */
-static inline void __io_cqring_wake(struct io_ring_ctx *ctx)
+static inline void io_cqring_wake(struct io_ring_ctx *ctx)
 {
 	/*
 	 * Trigger waitqueue handler on all waiters on our waitqueue. This
@@ -241,17 +240,11 @@ static inline void __io_cqring_wake(struct io_ring_ctx *ctx)
 	 * waitqueue handlers, we know we have a dependency between eventfd or
 	 * epoll and should terminate multishot poll at that point.
 	 */
-	if (waitqueue_active(&ctx->cq_wait))
+	if (wq_has_sleeper(&ctx->cq_wait))
 		__wake_up(&ctx->cq_wait, TASK_NORMAL, 0,
 				poll_to_key(EPOLL_URING_WAKE | EPOLLIN));
 }
 
-static inline void io_cqring_wake(struct io_ring_ctx *ctx)
-{
-	smp_mb();
-	__io_cqring_wake(ctx);
-}
-
 static inline bool io_sqring_full(struct io_ring_ctx *ctx)
 {
 	struct io_rings *r = ctx->rings;