The patch below does not apply to the 6.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y git checkout FETCH_HEAD git cherry-pick -x e15cb2200b934e507273510ba6bc747d5cde24a3 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025122915-sensually-wasting-f5f8@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From e15cb2200b934e507273510ba6bc747d5cde24a3 Mon Sep 17 00:00:00 2001 From: Jens Axboe axboe@kernel.dk Date: Tue, 9 Dec 2025 13:25:23 -0700 Subject: [PATCH] io_uring: fix min_wait wakeups for SQPOLL
Using min_wait, two timeouts are given:
1) The min_wait timeout, within which up to 'wait_nr' events are waited for. 2) The overall long timeout, which is entered if no events are generated in the min_wait window.
If the min_wait has expired, any event being posted must wake the task. For SQPOLL, that isn't the case, as it won't trigger the io_has_work() condition, as it will have already processed the task_work that happened when an event was posted. This causes any event to trigger post the min_wait to not always cause the waiting application to wakeup, and instead it will wait until the overall timeout has expired. This can be shown in a test case that has a 1 second min_wait, with a 5 second overall wait, even if an event triggers after 1.5 seconds:
axboe@m2max-kvm /d/iouring-mre (master)> zig-out/bin/iouring info: MIN_TIMEOUT supported: true, features: 0x3ffff info: Testing: min_wait=1000ms, timeout=5s, wait_nr=4 info: 1 cqes in 5000.2ms
where the expected result should be:
axboe@m2max-kvm /d/iouring-mre (master)> zig-out/bin/iouring info: MIN_TIMEOUT supported: true, features: 0x3ffff info: Testing: min_wait=1000ms, timeout=5s, wait_nr=4 info: 1 cqes in 1500.3ms
When the min_wait timeout triggers, reset the number of completions needed to wake the task. This should ensure that any future events will wake the task, regardless of how many events it originally wanted to wait for.
Reported-by: Tip ten Brink tip@tenbrinkmeijs.com Cc: stable@vger.kernel.org Fixes: 1100c4a2656d ("io_uring: add support for batch wait timeout") Link: https://github.com/axboe/liburing/issues/1477 Signed-off-by: Jens Axboe axboe@kernel.dk
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 5d130c578435..6cb24cdf8e68 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -2536,6 +2536,9 @@ static enum hrtimer_restart io_cqring_min_timer_wakeup(struct hrtimer *timer) goto out_wake; }
+ /* any generated CQE posted past this time should wake us up */ + iowq->cq_tail = iowq->cq_min_tail; + hrtimer_update_function(&iowq->t, io_cqring_timer_wakeup); hrtimer_set_expires(timer, iowq->timeout); return HRTIMER_RESTART;