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List:       freebsd-bugs
Subject:    Re: kern/14486: repeated arrival/departure of disks leads to panic
From:       Bruce Evans <bde () zeta ! org ! au>
Date:       1999-10-29 12:10:01
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The following reply was made to PR kern/14486; it has been noted by GNATS.

From: Bruce Evans <bde@zeta.org.au>
To: Matthew Jacob <mjacob@feral.com>
Cc: FreeBSD-gnats-submit@FreeBSD.ORG
Subject: Re: kern/14486: repeated arrival/departure of disks leads to panic
 in dscheck
Date: Fri, 29 Oct 1999 22:01:28 +1000 (EST)

 > >Description:
 > 
 > repeated arrivals/departures of disks, sometimes with the labels changed,
 > yields a panic:
 > 
 > Stopped at      dscheck+0x53:   movl    0x10(%edx),%esi
 > db> t
 > dscheck(c3327a38,0) at dscheck+0x53
 > diskstrategy(c3327a38,c0ae4780,200,c0a4db80,0) at diskstrategy+0xad
 > readdisklabel(c0ae4780,c0a51600,c0a4db80,c0b1e8e0,c0a4db80) at readdisklabel+0x5
 > 3
 > dsopen(c0a4db80,2000,0,c0b1e8ec,c0b1e8f0) at dsopen+0x248
 > diskopen(c0a4db80,1,2000,c7c77800,0) at diskopen+0xdb
 
 Rev.1.39 of scsi_da.c (actually, all revs. of subr_disk.c) seems to be
 quite buggy.  diskopen(), at least, doesn't seem to do sufficient locking.
 The old daopen() holds a lock for essentially the whole open, but
 diskopen() allows concurrent opens (and closes!).  Bad things probably
 happen if the label is changed.  Even null changes may cause problems if
 they are not atomic.
 
 Bruce
 
 


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