Re: 2.6.21-rc suspend regression: sysfs deadlock

Oliver Neukum
2007-03-07T14:39:03Z

Am Mittwoch, 7. März 2007 02:56 schrieb Linus Torvalds:
> Anyway, I'm unable to revert the broken commit, since there are now other
> changes that depend on it, but can somebody *please* do that? I'll apply
> Hugh's silly patch in the meantime, just to avoid the lockup.

As you like it. This patch reverts it.

Regards
Oliver

Signed-off-by: Oliver Neukum <oliver@neukum.name>
-----

--- orig/fs/sysfs/inode.c 2007-03-07 10:49:42.000000000 +0100
+++ linux-2.6.21-rc3/fs/sysfs/inode.c 2007-03-07 10:52:56.000000000 +0100
@@ -220,20 +220,6 @@
return NULL;
}

-static inline void orphan_all_buffers(struct inode *node)
-{
- struct sysfs_buffer_collection *set = node->i_private;
- struct sysfs_buffer *buf;
-
- mutex_lock_nested(&node->i_mutex, I_MUTEX_CHILD);
- if (node->i_private) {
- list_for_each_entry(buf, &set->associates, associates)
- buf->orphaned = 1;
- }
- mutex_unlock(&node->i_mutex);
-}
-
-
/*
* Unhashes the dentry corresponding to given sysfs_dirent
* Called with parent inode's i_mutex held.
@@ -241,23 +227,16 @@
void sysfs_drop_dentry(struct sysfs_dirent * sd, struct dentry * parent)
{
struct dentry * dentry = sd->s_dentry;
- struct inode *inode;

if (dentry) {
spin_lock(&dcache_lock);
spin_lock(&dentry->d_lock);
if (!(d_unhashed(dentry) && dentry->d_inode)) {
- inode = dentry->d_inode;
- spin_lock(&inode->i_lock);
- __iget(inode);
- spin_unlock(&inode->i_lock);
dget_locked(dentry);
__d_drop(dentry);
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);
--- orig/fs/sysfs/file.c 2007-03-07 10:37:28.000000000 +0100
+++ linux-2.6.21-rc3/fs/sysfs/file.c 2007-03-07 10:54:00.000000000 +0100
@@ -7,7 +7,6 @@
#include <linux/kobject.h>
#include <linux/namei.h>
#include <linux/poll.h>
-#include <linux/list.h>
#include <asm/uaccess.h>
#include <asm/semaphore.h>

@@ -52,30 +51,6 @@
};

/**
- * add_to_collection - add buffer to a collection
- * @buffer: buffer to be added
- * @node: inode of set to add to
- */
-
-static inline void
-add_to_collection(struct sysfs_buffer *buffer, struct inode *node)
-{
- struct sysfs_buffer_collection *set = node->i_private;
-
- mutex_lock(&node->i_mutex);
- list_add(&buffer->associates, &set->associates);
- mutex_unlock(&node->i_mutex);
-}
-
-static inline void
-remove_from_collection(struct sysfs_buffer *buffer, struct inode *node)
-{
- mutex_lock(&node->i_mutex);
- list_del(&buffer->associates);
- mutex_unlock(&node->i_mutex);
-}
-
-/**
* fill_read_buffer - allocate and fill buffer from object.
* @dentry: dentry pointer.
* @buffer: data buffer for file.
@@ -168,10 +143,6 @@
ssize_t retval = 0;

down(&buffer->sem);
- if (buffer->orphaned) {
- retval = -ENODEV;
- goto out;
- }
if (buffer->needs_read_fill) {
if ((retval = fill_read_buffer(file->f_path.dentry,buffer)))
goto out;
@@ -261,16 +232,11 @@
ssize_t len;

down(&buffer->sem);
- if (buffer->orphaned) {
- len = -ENODEV;
- goto out;
- }
len = fill_write_buffer(buffer, buf, count);
if (len > 0)
len = flush_write_buffer(file->f_path.dentry, buffer, len);
if (len > 0)
*ppos += len;
-out:
up(&buffer->sem);
return len;
}
@@ -279,7 +245,6 @@
{
struct kobject *kobj = sysfs_get_kobject(file->f_path.dentry->d_parent);
struct attribute * attr = to_attr(file->f_path.dentry);
- struct sysfs_buffer_collection *set;
struct sysfs_buffer * buffer;
struct sysfs_ops * ops = NULL;
int error = 0;
@@ -309,18 +274,6 @@
if (!ops)
goto Eaccess;

- /* make sure we have a collection to add our buffers to */
- mutex_lock(&inode->i_mutex);
- if (!(set = inode->i_private)) {
- if (!(set = inode->i_private = kmalloc(sizeof(struct sysfs_buffer_collection), GFP_KERNEL))) {
- error = -ENOMEM;
- goto Done;
- } else {
- INIT_LIST_HEAD(&set->associates);
- }
- }
- mutex_unlock(&inode->i_mutex);
-
/* File needs write support.
* The inode's perms must say it's ok,
* and we must have a store method.
@@ -346,11 +299,9 @@
*/
buffer = kzalloc(sizeof(struct sysfs_buffer), GFP_KERNEL);
if (buffer) {
- INIT_LIST_HEAD(&buffer->associates);
init_MUTEX(&buffer->sem);
buffer->needs_read_fill = 1;
buffer->ops = ops;
- add_to_collection(buffer, inode);
file->private_data = buffer;
} else
error = -ENOMEM;
@@ -375,8 +326,6 @@
struct module * owner = attr->owner;
struct sysfs_buffer * buffer = filp->private_data;

- if (buffer)
- remove_from_collection(buffer, inode);
kobject_put(kobj);
/* After this point, attr should not be accessed. */
module_put(owner);
--- orig/fs/sysfs/mount.c 2007-03-07 10:37:50.000000000 +0100
+++ linux-2.6.21-rc3/fs/sysfs/mount.c 2007-03-07 10:38:14.000000000 +0100
@@ -19,12 +19,9 @@
struct super_block * sysfs_sb = NULL;
struct kmem_cache *sysfs_dir_cachep;

-static void sysfs_clear_inode(struct inode *inode);
-
static const struct super_operations sysfs_ops = {
.statfs = simple_statfs,
.drop_inode = sysfs_delete_inode,
- .clear_inode = sysfs_clear_inode,
};

static struct sysfs_dirent sysfs_root = {
@@ -35,11 +32,6 @@
.s_iattr = NULL,
};

-static void sysfs_clear_inode(struct inode *inode)
-{
- kfree(inode->i_private);
-}
-
static int sysfs_fill_super(struct super_block *sb, void *data, int silent)
{
struct inode *inode;
--- orig/fs/sysfs/sysfs.h 2007-03-07 10:38:44.000000000 +0100
+++ linux-2.6.21-rc3/fs/sysfs/sysfs.h 2007-03-07 10:39:26.000000000 +0100
@@ -46,21 +46,15 @@
};

struct sysfs_buffer {
- struct list_head associates;
size_t count;
loff_t pos;
char * page;
struct sysfs_ops * ops;
struct semaphore sem;
- int orphaned;
int needs_read_fill;
int event;
};

-struct sysfs_buffer_collection {
- struct list_head associates;
-};
-
static inline struct kobject * to_kobj(struct dentry * dentry)
{
struct sysfs_dirent * sd = dentry->d_fsdata;