Date: Sat, 7 Dec 2002 15:33:26 -0800 From: Kris Kennaway <kris@obsecurity.org> To: Robert Watson <rwatson@FreeBSD.ORG> Cc: Kris Kennaway <kris@obsecurity.org>, Lars Eggert <larse@ISI.EDU>, current@FreeBSD.ORG, jhb@FreeBSD.ORG, alfred@FreeBSD.org Subject: Re: LOR: filedesc structure -> pipe mutex Message-ID: <20021207233326.GA75251@rot13.obsecurity.org> In-Reply-To: <Pine.NEB.3.96L.1021207085646.9402G-100000@fledge.watson.org> References: <20021207043355.GA75597@rot13.obsecurity.org> <Pine.NEB.3.96L.1021207085646.9402G-100000@fledge.watson.org>
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On Sat, Dec 07, 2002 at 08:58:26AM -0500, Robert Watson wrote:
> On Fri, 6 Dec 2002, Kris Kennaway wrote:
>=20
> > On Fri, Dec 06, 2002 at 07:18:03PM -0800, Lars Eggert wrote:
> >=20
> > > >I'm getting this too:
> >=20
> > After discussing this with various people on IRC, it was determined that
> > this is not the place where the reversal is occurring, but since witness
> > doesn't have the lock order defined it has to guess, and in this
> > instance it is guessing the wrong way around. After adding the lock
> > order to subr_witness.c I now get this:=20
>=20
> Yeah, we're exchanging some out-of-band e-mail on this: the basic problem
> is that:
>=20
> filedesc>pipe
> pipe>sigio
> sigio>proc
> proc>filedesc
>=20
> We're talking about some possible solutions, including deferred
> signalling, etc, etc.=20
Here's another panic I got overnight:
lock order reversal
1st 0xc4cbcd80 pipe mutex (pipe mutex) @ /local0/src-client/sys/kern/sys_p=
ipe.c:465
2nd 0xc044e780 sigio lock (sigio lock) @ /local0/src-client/sys/kern/kern_=
sig.c:2225
Debugger("witness_lock")
Stopped at Debugger+0x54: xchgl %ebx,in_Debugger.0
db> trace
Debugger(c03efc85,c044e780,c04141a3,c04141a3,c0416b5c) at Debugger+0x54
witness_lock(c044e780,8,c0416b5c,8b1,c4cbcd80) at witness_lock+0x667
_mtx_lock_flags(c044e780,0,c0416b5c,8b1,23) at _mtx_lock_flags+0xb1
pgsigio(c5cf3cf8,17,0,1ad,0) at pgsigio+0x30
pipe_read(c63b2c6c,d9539c7c,c4e91f00,0,c67608c0) at pipe_read+0x516
dofileread(c67608c0,c63b2c6c,4,bfbff533,1) at dofileread+0xd2
read(c67608c0,d9539d10,c043094c,407,3) at read+0x6b
syscall(2f,2f,2f,0,bfbff534) at syscall+0x28e
Xint0x80_syscall() at Xint0x80_syscall+0x1d
--- syscall (3, FreeBSD ELF32, read), eip =3D 0x2812d1c8, esp =3D 0xbfbff50=
0, ebp =3D 0xbfbff700 ---
db>
Kris
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