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To: Mike Silbersack <silby@silby.com>
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Date: Sat, 06 Dec 2003 18:05:52 -0800
From: Peter Wemm <peter@wemm.org>
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cc: Alan Cox <alc@FreeBSD.org>
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Subject: Re: cvs commit: src/sys/vm vm_mmap.c 
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Mike Silbersack wrote:
> 
> WHOOOOOOOOOOO HOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
> 
> I'm not sure if any has realized it yet, but I think that this may be our
> first actual deadlock condition.  This means that we're actually locking
> things!

Heh, I can add a few deadlocks too if that'll get some more cheers :-)

> Congrats,
> 
> Mike "Silby" Silbersack
> 
> 
> On Fri, 5 Dec 2003, Alan Cox wrote:
> 
> > alc         2003/12/05 21:45:32 PST
> >
> >   FreeBSD src repository
> >
> >   Modified files:
> >     sys/vm               vm_mmap.c
> >   Log:
> >   Fix a deadlock between vm_fault() and vm_mmap(): The expected lock orderi
    ng
> >   between vm_map and vnode locks is that vm_map locks are acquired first.  
    In
> >   revision 1.150 mmap(2) was changed to pass a locked vnode into vm_mmap().
> >   This creates a lock-order reversal when vm_mmap() calls one of the vm_map
> >   routines that acquires a vm_map lock.  The solution implemented herein is
> >   to release the vnode lock in mmap() before calling vm_mmap() and reacquir
    e
> >   this lock if necessary in vm_mmap().
> >
> >   Approved by:    re (scottl)
> >   Reviewed by:    jeff, kan, rwatson
> >
> >   Revision  Changes    Path
> >   1.174     +13 -4     src/sys/vm/vm_mmap.c
> >
> 

Cheers,
-Peter
--
Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com
"All of this is for nothing if we don't go to the stars" - JMS/B5