From: Ken Brown <kbrown@cornell.edu>
To: cygwin-developers@cygwin.com
Subject: Re: thread safety of fhandler_base_overlapped
Date: Mon, 20 Dec 2021 18:48:42 -0500 [thread overview]
Message-ID: <a9dc6337-57cc-6eb6-73ef-3460fbaa2a30@cornell.edu> (raw)
In-Reply-To: <vrita6guzxpb.fsf@gmail.com>
On 12/20/2021 6:02 PM, David McFarland wrote:
> I'm seeing a problem where occasionally write() returns EAGAIN on a
> blocking pipe. I believe this happens when multiple threads are writing
> concurrently to the pipe, and the overlapped structure is modified by
> one thread while another one is between calls to WFMO and
> GetOverlappedResult.
>
> I found this change:
>
> =====
> commit 2a4b1de773e6159ea8197b6fc3f7e4845479b476
> Author: Corinna Vinschen <corinna@vinschen.de>
> Date: Mon Mar 23 21:06:00 2020 +0100
>
> Cygwin: serial: use per call OVERLAPPED structs
>
> Sharing the OVERLAPPED struct and event object in there between
> read and select calls in the fhandler might have been a nice
> optimization way back when, but it is a dangerous, not thread-safe
> approach. Fix this by creating per-fhandler, per-call OVERLAPPED
> structs and event objects on demand.
>
> Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
> =====
>
> which seems to fix a similar problem in fhandler_serial.
>
> Is is possible that this needs to be done for fhandler_base_overlapped
> as well? I'll try using per-call buffers to see if it fixes my problem.
fhandler_base_overlapped was removed in commit f002d02b17. Are you looking at
an old version of the sources?
Ken
next prev parent reply other threads:[~2021-12-20 23:48 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-20 23:02 David McFarland
2021-12-20 23:48 ` Ken Brown [this message]
2021-12-20 23:58 ` Takashi Yano
2021-12-21 0:03 ` Takashi Yano
2021-12-21 0:59 ` David McFarland
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