From owner-freebsd-questions  Fri May  7  0:41: 5 1999
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To: "Sameer R. Manek" <manek@ecst.csuchico.edu>
Cc: freebsd-questions@FreeBSD.ORG, freebsd-hackers@FreeBSD.ORG
Subject: Re: bug with lockf(3)? 
In-reply-to: Your message of "Thu, 06 May 1999 22:31:35 PDT."
             <Pine.GHP.4.05.9905062228500.7884-100000@polio.ecst.csuchico.edu> 
From: David Greenman <dg@root.com>
Reply-To: dg@root.com
Date: Fri, 07 May 1999 00:37:36 -0700
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>I had posted this originally to freebsd-stable but didn't get any response
>from that list.
>
>On freebsd 3-1-stable I'm not sure if this is a bug or my misinterpetation
>of how lockf() works. But here's the situation.
>
>Given 2 processes A and B, both with open file descriptors to a file,
>using open ("file.txt",O_RDWR)
>A calls lockf (fd,F_LOCK,0) and proceeds to read/write to file 
>while file is still locked....including using lseek to jump to the
>begining of the file
>B calls lockf (fd,F_LOCK,0) and enters blocked state
>A calls lockf (fd,F_ULOCK,0)
>B is still in blocked state, until A exit(3)s.
>
>According to the man page:
>     F_LOCK and F_TLOCK requests differ only by the action taken if the
>section is not available.  F_LOCK blocks the calling process until the
>section is available.  F_TLOCK makes the function fail if the section is
>already locked by another process.

   Does the same problem occur when using flock()?

-DG

David Greenman
Co-founder/Principal Architect, The FreeBSD Project - http://www.freebsd.org
Creator of high-performance Internet servers - http://www.terasolutions.com


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