Re: 2.6.20-rc2-mm1: INFO: possible recursive locking detected in con_close

Frederik Deweerdt
2006-12-29T11:02:30Z

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On Thu, Dec 28, 2006 at 10:25:12PM +0100, Laurent Riffard wrote:
> Le 28.12.2006 11:42, Andrew Morton a écrit :
> >ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.20-rc2/2.6.20-rc2-mm1/
>
> Hello,
>
> got this with 2.6.20-rc2-mm1, reverting
> gregkh-driver-driver-core-fix-race-in-sysfs-between-sysfs_remove_file-and-read-write.patch made it disappear.
>
Hi,

This is due to sysfs_hash_and_remove() holding dir->d_inode->i_mutex
before calling sysfs_drop_dentry() which calls orphan_all_buffers()
which in turn takes node->i_mutex.
The following patch solves the problem by defering the buffers orphaning
after the dir->d_inode->imutex is released. Not sure it's the best
solution though, Greg?

Regards,
Frederik

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

diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index 8c533cb..7cac0b6 100644
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -230,10 +230,10 @@ static inline void orphan_all_buffers(struct inode *node)
* Unhashes the dentry corresponding to given sysfs_dirent
* Called with parent inode's i_mutex held.
*/
-void sysfs_drop_dentry(struct sysfs_dirent * sd, struct dentry * parent)
+struct inode *sysfs_drop_dentry(struct sysfs_dirent * sd, struct dentry * parent)
{
struct dentry * dentry = sd->s_dentry;
- struct inode *inode;
+ struct inode *inode = NULL;

if (dentry) {
spin_lock(&dcache_lock);
@@ -248,19 +248,19 @@ void sysfs_drop_dentry(struct sysfs_dirent * sd, struct dentry * parent)
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
simple_unlink(parent->d_inode, dentry);
- orphan_all_buffers(inode);
- iput(inode);
} else {
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
}
}
+ return inode;
}

int sysfs_hash_and_remove(struct dentry * dir, const char * name)
{
struct sysfs_dirent * sd;
struct sysfs_dirent * parent_sd;
+ struct inode *inode;
int found = 0;

if (!dir)
@@ -277,7 +277,7 @@ int sysfs_hash_and_remove(struct dentry * dir, const char * name)
continue;
if (!strcmp(sysfs_get_name(sd), name)) {
list_del_init(&sd->s_sibling);
- sysfs_drop_dentry(sd, dir);
+ inode = sysfs_drop_dentry(sd, dir);
sysfs_put(sd);
found = 1;
break;
@@ -285,5 +285,10 @@ int sysfs_hash_and_remove(struct dentry * dir, const char * name)
}
mutex_unlock(&dir->d_inode->i_mutex);

+ if (found == 1 && inode) {
+ orphan_all_buffers(inode);
+ iput(inode);
+ }
+
return found ? 0 : -ENOENT;
}
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index 5100a12..ef9d217 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -17,7 +17,7 @@ extern int sysfs_create_subdir(struct kobject *, const char *, struct dentry **)
extern void sysfs_remove_subdir(struct dentry *);

extern const unsigned char * sysfs_get_name(struct sysfs_dirent *sd);
-extern void sysfs_drop_dentry(struct sysfs_dirent *sd, struct dentry *parent);
+extern struct inode * sysfs_drop_dentry(struct sysfs_dirent *sd, struct dentry *parent);
extern int sysfs_setattr(struct dentry *dentry, struct iattr *iattr);

extern struct rw_semaphore sysfs_rename_sem;