From: "Stefan Bühler" <source@stbuehler.de>
To: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: [PATCH v1 3/3] io_uring: fix poll full SQ detection
Date: Fri, 19 Apr 2019 11:57:46 +0200 [thread overview]
Message-ID: <20190419095746.22894-3-source@stbuehler.de> (raw)
In-Reply-To: <20190419095746.22894-1-source@stbuehler.de>
io_uring_poll shouldn't signal EPOLLOUT | EPOLLWRNORM if the queue is
full; the old check would always signal EPOLLOUT | EPOLLWRNORM (unless
there were U32_MAX - 1 entries in the SQ queue).
Signed-off-by: Stefan Bühler <source@stbuehler.de>
---
fs/io_uring.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 912b0b304d90..047a0aa7a58c 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2576,7 +2576,8 @@ static __poll_t io_uring_poll(struct file *file, poll_table *wait)
poll_wait(file, &ctx->cq_wait, wait);
/* See comment at the top of this file */
smp_rmb();
- if (READ_ONCE(ctx->sq_ring->r.tail) + 1 != ctx->cached_sq_head)
+ if (READ_ONCE(ctx->sq_ring->r.tail) - ctx->cached_sq_head !=
+ ctx->sq_ring->ring_entries)
mask |= EPOLLOUT | EPOLLWRNORM;
if (READ_ONCE(ctx->cq_ring->r.head) != ctx->cached_cq_tail)
mask |= EPOLLIN | EPOLLRDNORM;
--
2.20.1
next prev parent reply other threads:[~2019-04-19 18:49 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 ` Stefan Bühler [this message]
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 ` [PATCH barrier cleanup v1 2/7] io_uring: remove unnecessary barrier before wq_has_sleeper Stefan Bühler
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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