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io_uring/wait: no early -ETIME if min_wait finds work

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When the min wait time is over and there is work to run, which for
DEFER_TASKRUN includes task_work that was queued lazily and didn't wake
the waiter, io_cqring_min_timer_wakeup() ends the wait via
io_cqring_timer_wakeup(). That flags it as timed out. io_cqring_wait()
runs the work, leaves the loop, and returns 0 if the CQ ring holds
something.

Running task_work doesn't have to result in a CQE, though. A poll wake up
can turn out to be spurious, for instance if somebody else has read the
data by the time the request is retried. The application then gets -ETIME
once the min wait time has passed, no matter how far away the timeout it
asked for is.

Wake the task without declaring a timeout. From now on a single CQE
satisfies the wait, like in the case where the timer is switched over to
the normal timeout. If running the work doesn't post one, the loop in
io_cqring_wait() goes back to sleep with the normal timeout.

Fixes: 1100c4a265 ("io_uring: add support for batch wait timeout")
Assisted-by: LLM
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Link: https://patch.msgid.link/20261015-b4-io-uring-fixes-v1-32-c1556f5d7bf5@toxicpanda.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Josef Bacik 2026-10-15 19:30:56 +00:00 committed by Jens Axboe
parent dad82eb180
commit 83cce67298
1 changed files with 10 additions and 3 deletions
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13
io_uring/wait.c
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@ -77,9 +77,16 @@ static enum hrtimer_restart io_cqring_min_timer_wakeup(struct hrtimer *timer)
if (iowq->timeout == KTIME_MAX ||
ktime_compare(iowq->min_timeout, iowq->timeout) >= 0)
goto out_wake;
/* work we may need to run, wake function will see if we need to wake */
if (io_has_work(ctx))
goto out_wake;
/*
* Work we need to run. It isn't known if that is going to post a CQE,
* so this isn't a timeout. Carry on with the normal one if it doesn't.
*/
if (io_has_work(ctx)) {
iowq->min_timeout = 0;
iowq->cq_tail = iowq->cq_min_tail + 1;
wake_up_process(iowq->wq.private);
return HRTIMER_NORESTART;
}
/* got events since we started waiting, min timeout is done */
scoped_guard(rcu) {
struct io_rings *rings = io_get_rings(ctx);