From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: cygwin-patches@cygwin.com
Subject: Re: Fix nanosleep returning negative rem
Date: Wed, 21 Jul 2021 10:39:39 +0200 [thread overview]
Message-ID: <YPfdSyPTCdSWhRv/@calimero.vinschen.de> (raw)
In-Reply-To: <000201d77d7a$2faae510$8f00af30$@cl.cam.ac.uk>
Hi David,
On Jul 20 16:16, David Allsopp wrote:
> I've pushed a repro case for this to
> https://github.com/dra27/cygwin-nanosleep-bug.git
>
> Originally noticed as the main CI system for OCaml has been failing
> sporadically for the signal.ml test mentioned in that repo. This morning I
> tried hammering that test on my dev machine and discovered that it fails
> very frequently. No idea if that's drivers, Windows 10 updates, number of
> cores or what, but it was definitely happening, and easily.
>
> Drilling further, it appears that NtQueryTimer is able to return a negative
> value in the TimeRemaining field even when SignalState is false. The values
> I've seen have always been < 15ms - i.e. less than the timer resolution, so
> I wonder if there is a point at which the timer has elapsed but has not been
> signalled, but WaitForMultipleObjects returns because of the EINTR signal.
> Mildly surprising that it seems to be so reproducible.
>
> Anyway, a patch is attached which simply guards a negative return value. The
> test on tbi.SignalState is in theory unnecessary.
Thanks for the patch, I think your patch is fine. However, I'd like
to dig a bit into this to see what exactly happens. Do you have a
very simple testcase in plain C, by any chance?
Thanks,
Corinna
next prev parent reply other threads:[~2021-07-21 8:39 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-20 15:16 David Allsopp
2021-07-21 8:39 ` Corinna Vinschen [this message]
2021-07-21 9:07 ` David Allsopp
2021-07-21 9:30 ` Corinna Vinschen
2021-07-21 9:33 ` Corinna Vinschen
2021-07-21 16:02 ` David Allsopp
2021-07-21 17:57 ` Lavrentiev, Anton (NIH/NLM/NCBI) [C]
2021-07-22 8:01 ` Corinna Vinschen
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