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Date: Sun, 7 Jun 2026 12:40:55 +0200
From: "Christian A. Ehrhardt" <lk@c--e.de>
To: Jens Axboe <axboe@kernel.dk>
Cc: Tip ten Brink <tip@tenbrinkmeijs.com>, io-uring@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] iouring: Fix min_timeout behaviour
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 <9f94f066-ea36-443e-b989-cf920ff9d27e@kernel.dk>
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On Sat, Jun 06, 2026 at 03:55:18PM -0600, Jens Axboe wrote:
> On 6/6/26 2:11 PM, Christian A. Ehrhardt wrote:
> > The wakeup condition if a min timeout is present and has
> > expired is that at least _one_ CQE was posted. Thus set
> > the cq_tail target to ->cq_min_tail + 1. Without this
> > commit a spurious wakeup can result in a premature wakeup
> > because io_should_wake() will return true even if _no_ CQE
> > was posted at all.
> > 
> > Tested by running the liburing testsuite with no regressions.
> > 
> > Additionally, tested by turning all calls to schedule() in
> > io_uring/wait.c into calls to schedule_timeout(1) to force
> > the spurious wakeups. With these spurious wakeups the
> > min-timeout.t test fails before and passes after this commit.
> 
> Either this or the test case is broken, with or without the change
> you sent for the test case. I'll take a look, but it's definitely
> not passing as-is.

I also tested with the zig reproducer from
	https://github.com/axboe/liburing/issues/1477
and with the spurious wakeups the reproducer shows the premature
wakeup without any CQE posted, too. It seems that the missing "+1"
is an oversight that got introduced between v1 and v2 of the commit
that fixed the above issue.


Best regards,
Christian