6.2 amd64 panic: lockmgr: thread 0xffffff009f9fd000, not exclusive lock holder 0xffffff003961c000 unlocking

[Guy Helmer]

Guy Helmer wrote:
> Does this make sense to anyone (it doesn't to me - procfs_doprofile 
> simply locks, calls vn_fullpath, and unlocks)?  I was trying to track 
> down a hang by running a system under stress, and instead got this 
> panic as a result of a process running a perl script that looks 
> through /proc/; it occurred on a very busy system with lots of process 
> churn.
Does this change to src/sys/fs/procfs.c make sense?  From my reading, it 
is possible for vn_lock(9) to fail...

Index: procfs.c
===================================================================
RCS file: /home/ncvs/src/sys/fs/procfs/procfs.c,v
retrieving revision 1.12.2.1
diff -u -r1.12.2.1 procfs.c
--- procfs.c    14 Jun 2006 21:20:39 -0000      1.12.2.1
+++ procfs.c    1 Feb 2007 15:19:30 -0000
@@ -69,8 +69,11 @@
 {
 	char *fullpath = "unknown";
 	char *freepath = NULL;
+	int err;
 
-	vn_lock(p->p_textvp, LK_EXCLUSIVE | LK_RETRY, td);
+	if ((err = vn_lock(p->p_textvp, LK_EXCLUSIVE | LK_RETRY, td)) != 0) {
+		return (err);
+	}
 	vn_fullpath(td, p->p_textvp, &fullpath, &freepath);
 	VOP_UNLOCK(p->p_textvp, 0, td);
 	sbuf_printf(sb, "%s", fullpath);