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Date: Tue, 27 Oct 2015 14:28:33 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: gawk: Bad File Descriptor error with concurrent readonly access to a network file
Message-ID: <20151027132833.GT5319@calimero.vinschen.de>
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On Oct 27 06:48, Matt D. wrote:
> I haven't had an opportunity to look into it but I've also encountered
> errors when performing a parallel make build (make -j) on a large C++
> project which has multiple interdependencies across a network share with =
too
> many threads.
>=20
> The reported "Bad File Descriptor" is the same error that I get.

That's fine and all, but it doesn't add any new info to the case.

>=20
> Matt D.
>=20
> On 10/27/2015 5:52 AM, Corinna Vinschen wrote:
> >On Sep 25 16:31, Vermessung AVT - Wolfgang Rieger wrote:
> >>1) Concurrent read access to the setup files was possible and worked
> >>fine with local files (24 hrs testing with millions of file accesses
> >>in 4 parallel jobs).
> >>2) However, when the file to be read (datafile.txt) is stored on a
> >>network share on a file server - which is the case in our working
> >>environment - the error could be reproduced. The number of Bad file
> >>descriptor errors seems to be related to the work load at the server
> >>where the file resides.
> >>3) The MS copy command shows no such error, even with network files.
> >>So we can substitute the cat's by copy's. For gawk, however, there is
> >>no shell alternative.
> >>
> >>It looks like there is a small time frame in opening files when the
> >>server file is non-accessible to other processes. If a parallel job
> >>happens to access the same file within that short time period while
> >>another process is opening it, the "Bad File Descriptor" error is
> >>thrown.
> >
> >Cygwin uses full sharing for all files it opens, unless the file is
> >opened in very specific circumstances (e.g, creating a symlink, deleting
> >a file).  "Bad file descriptor" doesn't point to a sharing problem.
> >It seems the handle is unusable or something.
> >
> >I tried your testcase and I can't reproduce the problem in my
> >environment.  Have you tried catching a trace of the problem via
> >strace?  It would be helpful to see where the EBADF occurs.

I'm running the testscript for a few hours now, with a server under heavy
load, but I still can't reproduce it.

Is this a bad interaction with some virus scanner, perhaps?


Corinna

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

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