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Subject:	Re: gawk: Bad File Descriptor error with concurrent readonly access to a network file
To:	cygwin AT cygwin DOT com
References:	<AB495CE313664A489959F8DEF45069A90188AA0710 AT EXSRV01 DOT avt-imst DOT local> <20151027095243 DOT GQ5319 AT calimero DOT vinschen DOT de>
From:	"Matt D." <matt AT codespunk DOT com>
Message-ID:	<562F566D.3020406@codespunk.com>
Date:	Tue, 27 Oct 2015 06:48:13 -0400
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In-Reply-To:	<20151027095243.GQ5319@calimero.vinschen.de>

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.

The reported "Bad File Descriptor" is the same error that I get.

Matt D.

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.
>
>
> Corinna
>

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