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Date:      Sun, 3 Mar 1996 07:26:55 +1000
From:      Bruce Evans <bde@zeta.org.au>
To:        jhay@mikom.csir.co.za, terry@lambert.org
Cc:        freebsd-current@FreeBSD.ORG
Subject:   Re: rename panics kernel
Message-ID:  <199603022126.HAA21506@godzilla.zeta.org.au>

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Yet more on this...

>> > Resently I got a "panic : vrele : negative reference count".
>> > The vrele() was called from rename().
>> > 
>> > I tried a simple script to exercise rename (attached below) and a
>> > current system seems to panic (trapped in ufs_rename).  There's a race
>> > condition lurking, it seems. I havent tried other than the sticky /tmp
>> > directory as the source and target files parent directory. Also the
>> > test was run under root's account, if it matters.
>> > 
>> > Rename exercise:
>> > ------
>> > #!/bin/sh
>> > a=/tmp/foo.now
>> > b=/tmp/foo.prev
>> > while true
>> > do
>> >         for n in 1 2 3 4 5 6 7 8 9 0
>> >         do
>> >                 (mv $a $b ; touch $a) &
>> >         done
>> >         wait
>> > done
>> > ------

This is a very versatile test :-).  I still haven't got it to panic for
rename with my own version of -current (my previous report about this
was misleading), but it caused the following problems:

On system b which has 16MB memory and 64MB swap, the script was killed
after about 5 hours with a "swap_pager: out of swap space" error.  The
system was otherwise inactive apart from running standard daemons.

On system c which has 8MB memory and 32MB swap, the script always causes 
a "vm_fork: u_map allocation failed" after about 1 minute.

Bruce



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