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io_uring: synchronise ev_posted() with waitqueues

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waitqueue_active() needs smp_mb() to be in sync with waitqueues
modification, but we miss it in io_cqring_ev_posted*() apart from
cq_wait() case.

Take an smb_mb() out of wq_has_sleeper() making it waitqueue_active(),
and place it a few lines before, so it can synchronise other
waitqueue_active() as well.

The patch doesn't add any additional overhead, so even if there are
no problems currently, it's just safer to have it this way.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2021-01-07 03:15:43 +00:00 committed by Jens Axboe
parent 4aa84f2ffa
commit b1445e59cc
1 changed files with 8 additions and 2 deletions
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10
fs/io_uring.c
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@ -1700,13 +1700,16 @@ static inline unsigned __io_cqring_events(struct io_ring_ctx *ctx)
static void io_cqring_ev_posted(struct io_ring_ctx *ctx)
{
/* see waitqueue_active() comment */
smp_mb();
if (waitqueue_active(&ctx->wait))
wake_up(&ctx->wait);
if (ctx->sq_data && waitqueue_active(&ctx->sq_data->wait))
wake_up(&ctx->sq_data->wait);
if (io_should_trigger_evfd(ctx))
eventfd_signal(ctx->cq_ev_fd, 1);
if (wq_has_sleeper(&ctx->cq_wait)) {
if (waitqueue_active(&ctx->cq_wait)) {
wake_up_interruptible(&ctx->cq_wait);
kill_fasync(&ctx->cq_fasync, SIGIO, POLL_IN);
}
@ -1714,13 +1717,16 @@ 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 (waitqueue_active(&ctx->wait))
wake_up(&ctx->wait);
}
if (io_should_trigger_evfd(ctx))
eventfd_signal(ctx->cq_ev_fd, 1);
if (wq_has_sleeper(&ctx->cq_wait)) {
if (waitqueue_active(&ctx->cq_wait)) {
wake_up_interruptible(&ctx->cq_wait);
kill_fasync(&ctx->cq_fasync, SIGIO, POLL_IN);
}