diff mbox series

[barrier,cleanup,v1,2/7] io_uring: remove unnecessary barrier before wq_has_sleeper

Message ID 20190424215422.7404-2-source@stbuehler.de (mailing list archive)
State Accepted, archived
Headers show
Series [barrier,cleanup,v1,1/7] io_uring: fix notes on barriers | expand

Commit Message

Stefan Bühler April 24, 2019, 9:54 p.m. UTC 
wq_has_sleeper has a full barrier internally. The smp_rmb barrier in
io_uring_poll synchronizes with it.

Signed-off-by: Stefan Bühler <source@stbuehler.de>
---
 fs/io_uring.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)
diff mbox series

Patch

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 7025e9830abe..1f4419f38ef1 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -418,12 +418,6 @@  static void io_commit_cqring(struct io_ring_ctx *ctx)
 		/* order cqe stores with ring update */
 		smp_store_release(&ring->r.tail, ctx->cached_cq_tail);
 
-		/*
-		 * Write sider barrier of tail update, app has read side. See
-		 * comment at the top of this file.
-		 */
-		smp_wmb();
-
 		if (wq_has_sleeper(&ctx->cq_wait)) {
 			wake_up_interruptible(&ctx->cq_wait);
 			kill_fasync(&ctx->cq_fasync, SIGIO, POLL_IN);
@@ -2674,7 +2668,9 @@  static __poll_t io_uring_poll(struct file *file, poll_table *wait)
 	__poll_t mask = 0;
 
 	poll_wait(file, &ctx->cq_wait, wait);
-	/* See comment at the top of this file */
+	/* synchronizes with barrier from wq_has_sleeper call in
+	 * io_commit_cqring
+	 */
 	smp_rmb();
 	if (READ_ONCE(ctx->sq_ring->r.tail) - ctx->cached_sq_head !=
 	    ctx->sq_ring->ring_entries)