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Subject: RE: flock/posix lock question
Date: Fri, 10 Sep 2004 16:41:50 -0500
Message-ID: <7A8F92187EF7A249BF847F1BF4903C046306E5@ausx2kmpc103.aus.amer.dell.com>
Thread-Topic: flock/posix lock question
Thread-Index: AcSXfr0aomLk/XJMTCOZBH5sE5sjQgAABNRQ
From: <Stuart_Hayes@Dell.com>
To: <linux-kernel@vger.kernel.org>
Cc: <Stuart_Hayes@Dell.com>
Sender: linux-kernel-owner@vger.kernel.org
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Hello--

This question regards file locks and code in fs/locks.c.

I am seeing the kernel get stuck in posix_locks_deadlock() checking for 
deadlocks.  It appears that samba (smbd) is getting both an flock and a 
posix lock for the same file, which results in a circular dependency in 
the blocked_list... and posix_locks_deadlock() is getting stuck in that
circle.  
The circular dependency gets into the blocked_list because deadlock 
situations aren't checked for when inserting flock requests into the 
blocked_list.

Since flocks aren't supposed to do any deadlock checking, it seems like
the 
right solution to this would be to modify posix_locks_deadlock() to only

check for deadlock situations with other posix locks and lock requests,
and 
ignore flocks.  Of course, samba should also probably be fixed so that
it 
doesn't do that, too... but it shouldn't be able to cause a kernel hang
by 
doing so.

Does this sound correct?  Am I missing something?

(I am seeing this on a RHEL3 update 3 (2.4.21-20) kernel.)

Thanks!
Stuart


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