Date: Thu, 1 Feb 2007 18:46:31 +0200 From: Kostik Belousov <kostikbel@gmail.com> To: Guy Helmer <ghelmer@palisadesys.com> Cc: freebsd-stable@freebsd.org Subject: Re: 6.2 amd64 panic: lockmgr: thread 0xffffff009f9fd000, not exclusive lock holder 0xffffff003961c000 unlocking Message-ID: <20070201164631.GJ56152@deviant.kiev.zoral.com.ua> In-Reply-To: <20070201163826.GI56152@deviant.kiev.zoral.com.ua> References: <45C0C749.1040300@palisadesys.com> <45C20F00.4010900@palisadesys.com> <20070201163826.GI56152@deviant.kiev.zoral.com.ua>
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On Thu, Feb 01, 2007 at 06:38:26PM +0200, Kostik Belousov wrote:
> On Thu, Feb 01, 2007 at 10:02:08AM -0600, Guy Helmer wrote:
> vn_lock with LK_EXCLUSIVE|LK_RETRY flags combination shall not fail. It s=
hould
> return even dead vnodes locked.
>=20
> I suspect that in fact this is race with exec(). Could you reproduce the
> panic ? And then, with this patch ?
>=20
> Index: fs/procfs/procfs.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
> RCS file: /usr/local/arch/ncvs/src/sys/fs/procfs/procfs.c,v
> retrieving revision 1.14
> diff -u -r1.14 procfs.c
> --- fs/procfs/procfs.c 5 Jun 2006 16:41:27 -0000 1.14
> +++ fs/procfs/procfs.c 1 Feb 2007 16:37:43 -0000
> @@ -69,10 +69,12 @@
> {
> char *fullpath =3D "unknown";
> char *freepath =3D NULL;
> + struct vnode *textvp;
> =20
> - vn_lock(p->p_textvp, LK_EXCLUSIVE | LK_RETRY, td);
> - vn_fullpath(td, p->p_textvp, &fullpath, &freepath);
> - VOP_UNLOCK(p->p_textvp, 0, td);
> + textvp =3D p->p_textvp;
> + vn_lock(textvp, LK_EXCLUSIVE | LK_RETRY, td);
> + vn_fullpath(td, textvp, &fullpath, &freepath);
> + VOP_UNLOCK(textvp, 0, td);
> sbuf_printf(sb, "%s", fullpath);
> if (freepath)
> free(freepath, M_TEMP);
That patch is incorrect as well: textvp may be reclaimed while waiting for
lock. Below is better version.
Index: fs/procfs/procfs.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
RCS file: /usr/local/arch/ncvs/src/sys/fs/procfs/procfs.c,v
retrieving revision 1.14
diff -u -r1.14 procfs.c
--- fs/procfs/procfs.c 5 Jun 2006 16:41:27 -0000 1.14
+++ fs/procfs/procfs.c 1 Feb 2007 16:44:41 -0000
@@ -69,10 +69,17 @@
{
char *fullpath =3D "unknown";
char *freepath =3D NULL;
+ struct vnode *textvp;
+ int err;
=20
- vn_lock(p->p_textvp, LK_EXCLUSIVE | LK_RETRY, td);
- vn_fullpath(td, p->p_textvp, &fullpath, &freepath);
- VOP_UNLOCK(p->p_textvp, 0, td);
+ textvp =3D p->p_textvp;
+ VI_LOCK(textvp);
+ vholdl(textvp);
+ err =3D vn_lock(textvp, LK_EXCLUSIVE | LK_INTERLOCK, td);
+ vdrop(textvp);
+ if (err)
+ vn_fullpath(td, textvp, &fullpath, &freepath);
+ VOP_UNLOCK(textvp, 0, td);
sbuf_printf(sb, "%s", fullpath);
if (freepath)
free(freepath, M_TEMP);
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