Date: Tue, 24 Mar 2009 22:08:07 +0200 From: Kostik Belousov <kostikbel@gmail.com> To: Jaakko Heinonen <jh@saunalahti.fi> Cc: 7ogcg7g02@sneakemail.com, freebsd-current@freebsd.org Subject: Re: panic: Bad link elm, nfsd related? Message-ID: <20090324200807.GK31897@deviant.kiev.zoral.com.ua> In-Reply-To: <20090324180437.GA952@a91-153-125-115.elisa-laajakaista.fi> References: <20090323140820.GA37093@zeeb.org> <20090324180437.GA952@a91-153-125-115.elisa-laajakaista.fi>
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On Tue, Mar 24, 2009 at 08:04:38PM +0200, Jaakko Heinonen wrote:
> On 2009-03-23, Matthew West wrote:
> > After 1-2 weeks, the system will panic with the following:
> >=20
> > ----------
> > panic: Bad link elm 0xffffff0011febc00 next->prev !=3D elm
>=20
> It looks like an attempt to remove xprt twice from tail queue due to
> race. Does this patch make any difference?
>=20
> %%%
> Index: sys/rpc/svc.c
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> --- sys/rpc/svc.c (revision 189918)
> +++ sys/rpc/svc.c (working copy)
> @@ -296,8 +296,10 @@ xprt_unregister_locked(SVCXPRT *xprt)
> TAILQ_REMOVE(&pool->sp_active, xprt, xp_alink);
> xprt->xp_active =3D FALSE;
> }
> - TAILQ_REMOVE(&pool->sp_xlist, xprt, xp_link);
> - xprt->xp_registered =3D FALSE;
> + if (xprt->xp_registered) {
> + TAILQ_REMOVE(&pool->sp_xlist, xprt, xp_link);
> + xprt->xp_registered =3D FALSE;
> + }
> }
> =20
> void
> %%%
>=20
> This was also reported by Edward Fisk (Cc'd) in PR 132068.
Yes, I did it, and discussed exactly the same change with dfr@.
The patch only fixes symptom, the real problem is double unreg.
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