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Date: Tue, 27 Oct 2015 10:52:43 +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: <20151027095243.GQ5319@calimero.vinschen.de>
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References: <AB495CE313664A489959F8DEF45069A90188AA0710 AT EXSRV01 DOT avt-imst DOT local>
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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.
>=20
> 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.


Corinna

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

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