linux-kernel - Re: [git pull] Re: fs/dcache.c - BUG: soft lockup - CPU#5 stuck for 22s! [systemd-udevd:1667]

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Sat, 31 May 2014 07:48:19 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Josh Boyer <jwboyer@...oraproject.org>
cc:	Al Viro <viro@...iv.linux.org.uk>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Miklos Szeredi <mszeredi@...e.cz>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [git pull] Re: fs/dcache.c - BUG: soft lockup - CPU#5 stuck for
 22s! [systemd-udevd:1667]



On Sat, 31 May 2014, Josh Boyer wrote:
> 
> One of my machines got the lockdep report below when booting a kernel
> that contained these patches. 

I think this is just a lacking annotation.

We do nest dentry d_lock locking, and in order to avoid ABBA deadlocks the 
rule is that we lock things in topological order (parent dentry first). 
lock_parent() is very careful about that, but doesn't actually tell 
lockdep about it.

This trivial oneliner should fix it.

			Linus

---
 fs/dcache.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index bce851dc03ef..be2bea834bf4 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -553,7 +553,7 @@ again:
 	}
 	rcu_read_unlock();
 	if (parent != dentry)
-		spin_lock(&dentry->d_lock);
+		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
 	else
 		parent = NULL;
 	return parent;
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/