io_uring: replace cmpxchg in fallback with xchg

io_run_ctx_fallback() can use xchg() instead of cmpxchg(). It's simpler
and faster.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 62a7354..57c7833 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -8484,15 +8484,11 @@ static int io_remove_personalities(int id, void *p, void *data)
 
 static bool io_run_ctx_fallback(struct io_ring_ctx *ctx)
 {
-       struct callback_head *work, *head, *next;
+       struct callback_head *work, *next;
        bool executed = false;
 
        do {
-               do {
-                       head = NULL;
-                       work = READ_ONCE(ctx->exit_task_work);
-               } while (cmpxchg(&ctx->exit_task_work, work, head) != work);
-
+               work = xchg(&ctx->exit_task_work, NULL);
                if (!work)
                        break;