Re: Lockdep splat in autofs with 2.6.39-rc2

[Steven Rostedt <rostedt@goodmis.org>]

On Thu, Apr 07, 2011 at 03:44:03PM -0400, Nick Bowler wrote:
> Just saw this on 2.6.39-rc2 after half a day or so of uptime.  I've
> never seen it before today so it may be a regression from 2.6.38.
> Nothing seems have failed as a result.  Please let me know if you
> need any more info.
>

Could you try this patch. I know it may be hard to reproduce, but the
issue is that we are recursing down the locks in a tree/list and we changed a
lock from being nested to being a parent. This patch tells lockdep about
what we did.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>


diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
index 450f529..1feb68e 100644
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -124,6 +124,7 @@ start:
 	/* Negative dentry - try next */
 	if (!simple_positive(q)) {
 		spin_unlock(&p->d_lock);
+		lock_set_subclass(&q->d_lock.dep_map, 0, _RET_IP_);
 		p = q;
 		goto again;
 	}
@@ -186,6 +187,7 @@ again:
 	/* Negative dentry - try next */
 	if (!simple_positive(ret)) {
 		spin_unlock(&p->d_lock);
+		lock_set_subclass(&ret->d_lock.dep_map, 0, _RET_IP_);
 		p = ret;
 		goto again;
 	}