linux-kernel - Re: [-mm patch] lockdep: possible deadlock in sysfs

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Date:	Fri, 5 Jan 2007 16:42:52 +0000
From:	Frederik Deweerdt <deweerdt@...e.fr>
To:	Oliver Neukum <oliver@...kum.org>
Cc:	Andrew Morton <akpm@...l.org>, linux-kernel@...r.kernel.org,
	greg@...ah.com, maneesh@...ibm.com, oliver@...kum.name
Subject: Re: [-mm patch] lockdep: possible deadlock in sysfs

On Fri, Jan 05, 2007 at 04:13:25PM +0100, Oliver Neukum wrote:
> Am Freitag, 5. Januar 2007 13:16 schrieb Frederik Deweerdt:
> > On Thu, Jan 04, 2007 at 10:02:00PM -0800, Andrew Morton wrote:
> > > 
> > > 	ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.20-rc3/2.6.20-rc3-mm1/
> > > 
> are you sure there's a code path that takes these locks in the reverse order?
> I've looked through the code twice and not found any. It doesn't make much
> sense to first lock the file and afterwards the directory.
You're right, an annotation should be enough, what do you think?

Regards,
Frederik


Signed-off-by: Frederik Deweerdt <frederik.deweerdt@...il.com>

diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index 8c533cb..3b5574b 100644
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -214,7 +214,7 @@ static inline void orphan_all_buffers(st
 	struct sysfs_buffer_collection *set = node->i_private;
 	struct sysfs_buffer *buf;
 
-	mutex_lock(&node->i_mutex);
+	mutex_lock_nested(&node->i_mutex, I_MUTEX_CHILD);
 	if (node->i_private) {
 		list_for_each_entry(buf, &set->associates, associates) {
 			down(&buf->sem);
@@ -271,7 +271,7 @@ int sysfs_hash_and_remove(struct dentry
 		return -ENOENT;
 
 	parent_sd = dir->d_fsdata;
-	mutex_lock(&dir->d_inode->i_mutex);
+	mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);
 	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
 		if (!sd->s_element)
 			continue;
 
> Regarding your patch, it should work, but I don't see the need for it.
> 
> 	Regards
> 		Oliver
> -
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