From: "Stefan Bühler" <source@stbuehler.de>
To: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: [PATCH barrier cleanup v1 2/7] io_uring: remove unnecessary barrier before wq_has_sleeper
Date: Wed, 24 Apr 2019 23:54:17 +0200 [thread overview]
Message-ID: <20190424215422.7404-2-source@stbuehler.de> (raw)
In-Reply-To: <20190424215422.7404-1-source@stbuehler.de>
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 --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)
--
2.20.1
next prev parent reply other threads:[~2019-04-24 21:54 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-14 16:44 io_uring memory ordering (and broken queue-is-full checks) Stefan Bühler
2019-04-17 15:02 ` Jens Axboe
2019-04-19 9:29 ` Stefan Bühler
2019-04-19 9:57 ` [PATCH v1 1/3] io_uring: fix race condition reading SQ entries Stefan Bühler
2019-04-19 9:57 ` [PATCH v1 2/3] io_uring: fix race condition when sq threads goes sleeping Stefan Bühler
2019-04-19 9:57 ` [PATCH v1 3/3] io_uring: fix poll full SQ detection Stefan Bühler
2019-04-22 17:04 ` io_uring memory ordering (and broken queue-is-full checks) Jens Axboe
2019-04-24 21:54 ` [PATCH barrier cleanup v1 1/7] io_uring: fix notes on barriers Stefan Bühler
2019-04-24 21:54 ` Stefan Bühler [this message]
2019-04-24 21:54 ` [PATCH barrier cleanup v1 3/7] io_uring: remove unnecessary barrier before reading cq head Stefan Bühler
2019-04-24 21:54 ` [PATCH barrier cleanup v1 4/7] io_uring: remove unnecessary barrier after updating SQ head Stefan Bühler
2019-04-24 21:54 ` [PATCH barrier cleanup v1 5/7] io_uring: remove unnecessary barrier before reading SQ tail Stefan Bühler
2019-04-24 21:54 ` [PATCH barrier cleanup v1 6/7] io_uring: remove unnecessary barrier after incrementing dropped counter Stefan Bühler
2019-04-24 21:54 ` [PATCH barrier cleanup v1 7/7] io_uring: remove unnecessary barrier after unsetting IORING_SQ_NEED_WAKEUP Stefan Bühler
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