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 should
> return even dead vnodes locked.
>
> I suspect that in fact this is race with exec(). Could you reproduce the
> panic ? And then, with this patch ?
>
> Index: fs/procfs/procfs.c
> ===================================================================
> 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 = "unknown";
> char *freepath = NULL;
> + struct vnode *textvp;
>
> - 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 = 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
===================================================================
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 = "unknown";
char *freepath = NULL;
+ struct vnode *textvp;
+ int err;
- 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 = p->p_textvp;
+ VI_LOCK(textvp);
+ vholdl(textvp);
+ err = 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);
pgpL5QSfNynWi.pgp
Description: PGP signature
