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Date: Thu, 12 Jan 2017 16:00:50 +0100
From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: cygwin@cygwin.com
Subject: Re: hang on 'cat /proc/mounts' when one of the network drives is on a 'down' system
Message-ID: <20170112150050.GB12383@calimero.vinschen.de>
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References: <5875B7F6.8090406@tlinx.org> <20170111201635.GA29910@calimero.vinschen.de> <5876F43E.7010608@tlinx.org>
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On Jan 11 19:13, L. A. Walsh wrote:
> Corinna Vinschen wrote:
> > I know why this happens but I don't see an easy way around that.
> > Basically the problem is that Cygwin has no control over the OS mount
> > points (i. e., drive letter mapping and volume ireparse points).  Given
> > that, apart from C: maybe, the drive letter mapping can change any time,
> > Cygwin doesn't cache the information but requests it every time it needs
> > it.  This includes information required in /proc/mounts, here basically
> > the FS type.  This in turn requires to open a handle to the FS, which
> > may result in the observed hang.
> ----
>    Thanks for the explanation.  Looking at my ".bashrc",
> I can't figure out why needed this so I can comment it out.
> However, as an "aside", I'm not sure why my workaround
> didn't work...though I might guess.
>=20
> I tried using 'timeout' from 'coreutils-8.23-4' like:
> readarray -t proc_mounts< <(timeout -k 2 1 cat /proc/mounts)
>=20
> I had hoped that w/cat hanging, timeout waits 1 second (2nd
> number), and if no response after the #secs after -k (2)
> then it's suppose to try to kill it.
>=20
> I'm guessing that since it's a cygwin signal, it is probably
> waiting for Win to return to cygwin land so cygwin can
> process the signal -- but since it's off in la la land,
> cygwin doesn't get a chance to clean up.

Exactly.  The hanging call is just some NtOpenFile call on the
filesystem.  The timeout is an unfortunate effect of accessing
a remote drive.  One problem here is that Cygwin doesn't support
interrupting of synchroneous Windows I/O calls from the signal
handler.  That's something I'm planning to do at one point, but
don't hold your breath.


Corinna

--=20
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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