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io_uring: fix missing mb() before waitqueue_active 

In case of !SQPOLL, io_cqring_ev_posted_iopoll() doesn't provide a
memory barrier required by waitqueue_active(&ctx->poll_wait). There is
a wq_has_sleeper(), which does smb_mb() inside, but it's called only for
SQPOLL.

Fixes: 5fd4617840 ("io_uring: be smarter about waking multiple CQ ring waiters")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/2982e53bcea2274006ed435ee2a77197107d8a29.1631130542.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2021-09-08 20:49:17 +01:00 committed by Jens Axboe
parent 713b9825a4
commit c57a91fb1c
1 changed files with 4 additions and 1 deletions
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5
fs/io_uring.c
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@ -1619,8 +1619,11 @@ static void io_cqring_ev_posted(struct io_ring_ctx *ctx)
static void io_cqring_ev_posted_iopoll(struct io_ring_ctx *ctx)
{
/* see waitqueue_active() comment */
smp_mb();
if (ctx->flags & IORING_SETUP_SQPOLL) {
if (wq_has_sleeper(&ctx->cq_wait))
if (waitqueue_active(&ctx->cq_wait))
wake_up_all(&ctx->cq_wait);
}
if (io_should_trigger_evfd(ctx))