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Task Control Groups: automatic userspace notification of idle cgroups 

Add the following files to the cgroup filesystem:

notify_on_release - configures/reports whether the cgroup subsystem should
attempt to run a release script when this cgroup becomes unused

release_agent - configures/reports the release agent to be used for this
hierarchy (top level in each hierarchy only)

releasable - reports whether this cgroup would have been auto-released if
notify_on_release was true and a release agent was configured (mainly useful
for debugging)

To avoid locking issues, invoking the userspace release agent is done via a
workqueue task; cgroups that need to have their release agents invoked by
the workqueue task are linked on to a list.

[pj@sgi.com: Need to include kmod.h]
Signed-off-by: Paul Menage <menage@google.com>
Cc: Serge E. Hallyn <serue@us.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: Kirill Korotaev <dev@openvz.org>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Paul Menage 2007-10-18 23:39:38 -07:00 committed by Linus Torvalds
parent 817929ec27
commit 81a6a5cdd2
2 changed files with 394 additions and 43 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
include/linux/cgroup.h
View File

@ -77,10 +77,11 @@ static inline void css_get(struct cgroup_subsys_state *css)
* css_get()
*/
extern void __css_put(struct cgroup_subsys_state *css);
static inline void css_put(struct cgroup_subsys_state *css)
{
if (!test_bit(CSS_ROOT, &css->flags))
atomic_dec(&css->refcnt);
__css_put(css);
}
struct cgroup {
@ -112,6 +113,13 @@ struct cgroup {
* tasks in this cgroup. Protected by css_set_lock
*/
struct list_head css_sets;
/*
* Linked list running through all cgroups that can
* potentially be reaped by the release agent. Protected by
* release_list_lock
*/
struct list_head release_list;
};
/* A css_set is a structure holding pointers to a set of
@ -293,7 +301,6 @@ struct task_struct *cgroup_iter_next(struct cgroup *cont,
struct cgroup_iter *it);
void cgroup_iter_end(struct cgroup *cont, struct cgroup_iter *it);
#else /* !CONFIG_CGROUPS */
static inline int cgroup_init_early(void) { return 0; }

426
kernel/cgroup.c
View File

@ -43,8 +43,11 @@
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/sort.h>
#include <linux/kmod.h>
#include <asm/atomic.h>
static DEFINE_MUTEX(cgroup_mutex);
/* Generate an array of cgroup subsystem pointers */
#define SUBSYS(_x) &_x ## _subsys,
@ -83,6 +86,13 @@ struct cgroupfs_root {
/* Hierarchy-specific flags */
unsigned long flags;
/* The path to use for release notifications. No locking
* between setting and use - so if userspace updates this
* while child cgroups exist, you could miss a
* notification. We ensure that it's always a valid
* NUL-terminated string */
char release_agent_path[PATH_MAX];
};
@ -110,7 +120,13 @@ static int need_forkexit_callback;
/* bits in struct cgroup flags field */
enum {
/* Control Group is dead */
CONT_REMOVED,
/* Control Group has previously had a child cgroup or a task,
* but no longer (only if CONT_NOTIFY_ON_RELEASE is set) */
CONT_RELEASABLE,
/* Control Group requires release notifications to userspace */
CONT_NOTIFY_ON_RELEASE,
};
/* convenient tests for these bits */
@ -124,6 +140,19 @@ enum {
ROOT_NOPREFIX, /* mounted subsystems have no named prefix */
};
inline int cgroup_is_releasable(const struct cgroup *cont)
{
const int bits =
(1 << CONT_RELEASABLE) |
(1 << CONT_NOTIFY_ON_RELEASE);
return (cont->flags & bits) == bits;
}
inline int notify_on_release(const struct cgroup *cont)
{
return test_bit(CONT_NOTIFY_ON_RELEASE, &cont->flags);
}
/*
* for_each_subsys() allows you to iterate on each subsystem attached to
* an active hierarchy
@ -135,6 +164,14 @@ list_for_each_entry(_ss, &_root->subsys_list, sibling)
#define for_each_root(_root) \
list_for_each_entry(_root, &roots, root_list)
/* the list of cgroups eligible for automatic release. Protected by
* release_list_lock */
static LIST_HEAD(release_list);
static DEFINE_SPINLOCK(release_list_lock);
static void cgroup_release_agent(struct work_struct *work);
static DECLARE_WORK(release_agent_work, cgroup_release_agent);
static void check_for_release(struct cgroup *cont);
/* Link structure for associating css_set objects with cgroups */
struct cg_cgroup_link {
/*
@ -189,11 +226,8 @@ static int use_task_css_set_links;
/*
* unlink a css_set from the list and free it
*/
static void release_css_set(struct kref *k)
static void unlink_css_set(struct css_set *cg)
{
struct css_set *cg = container_of(k, struct css_set, ref);
int i;
write_lock(&css_set_lock);
list_del(&cg->list);
css_set_count--;
@ -206,11 +240,39 @@ static void release_css_set(struct kref *k)
kfree(link);
}
write_unlock(&css_set_lock);
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)
atomic_dec(&cg->subsys[i]->cgroup->count);
}
static void __release_css_set(struct kref *k, int taskexit)
{
int i;
struct css_set *cg = container_of(k, struct css_set, ref);
unlink_css_set(cg);
rcu_read_lock();
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup *cont = cg->subsys[i]->cgroup;
if (atomic_dec_and_test(&cont->count) &&
notify_on_release(cont)) {
if (taskexit)
set_bit(CONT_RELEASABLE, &cont->flags);
check_for_release(cont);
}
}
rcu_read_unlock();
kfree(cg);
}
static void release_css_set(struct kref *k)
{
__release_css_set(k, 0);
}
static void release_css_set_taskexit(struct kref *k)
{
__release_css_set(k, 1);
}
/*
* refcounted get/put for css_set objects
*/
@ -224,6 +286,11 @@ static inline void put_css_set(struct css_set *cg)
kref_put(&cg->ref, release_css_set);
}
static inline void put_css_set_taskexit(struct css_set *cg)
{
kref_put(&cg->ref, release_css_set_taskexit);
}
/*
* find_existing_css_set() is a helper for
* find_css_set(), and checks to see whether an existing
@ -465,8 +532,6 @@ static struct css_set *find_css_set(
* update of a tasks cgroup pointer by attach_task()
*/
static DEFINE_MUTEX(cgroup_mutex);
/**
* cgroup_lock - lock out any changes to cgroup structures
*
@ -526,6 +591,13 @@ static void cgroup_diput(struct dentry *dentry, struct inode *inode)
if (S_ISDIR(inode->i_mode)) {
struct cgroup *cont = dentry->d_fsdata;
BUG_ON(!(cgroup_is_removed(cont)));
/* It's possible for external users to be holding css
* reference counts on a cgroup; css_put() needs to
* be able to access the cgroup after decrementing
* the reference count in order to know if it needs to
* queue the cgroup to be handled by the release
* agent */
synchronize_rcu();
kfree(cont);
}
iput(inode);
@ -657,6 +729,8 @@ static int cgroup_show_options(struct seq_file *seq, struct vfsmount *vfs)
seq_printf(seq, ",%s", ss->name);
if (test_bit(ROOT_NOPREFIX, &root->flags))
seq_puts(seq, ",noprefix");
if (strlen(root->release_agent_path))
seq_printf(seq, ",release_agent=%s", root->release_agent_path);
mutex_unlock(&cgroup_mutex);
return 0;
}
@ -664,6 +738,7 @@ static int cgroup_show_options(struct seq_file *seq, struct vfsmount *vfs)
struct cgroup_sb_opts {
unsigned long subsys_bits;
unsigned long flags;
char *release_agent;
};
/* Convert a hierarchy specifier into a bitmask of subsystems and
@ -675,6 +750,7 @@ static int parse_cgroupfs_options(char *data,
opts->subsys_bits = 0;
opts->flags = 0;
opts->release_agent = NULL;
while ((token = strsep(&o, ",")) != NULL) {
if (!*token)
@ -683,6 +759,15 @@ static int parse_cgroupfs_options(char *data,
opts->subsys_bits = (1 << CGROUP_SUBSYS_COUNT) - 1;
} else if (!strcmp(token, "noprefix")) {
set_bit(ROOT_NOPREFIX, &opts->flags);
} else if (!strncmp(token, "release_agent=", 14)) {
/* Specifying two release agents is forbidden */
if (opts->release_agent)
return -EINVAL;
opts->release_agent = kzalloc(PATH_MAX, GFP_KERNEL);
if (!opts->release_agent)
return -ENOMEM;
strncpy(opts->release_agent, token + 14, PATH_MAX - 1);
opts->release_agent[PATH_MAX - 1] = 0;
} else {
struct cgroup_subsys *ss;
int i;
@ -732,7 +817,11 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data)
if (!ret)
cgroup_populate_dir(cont);
if (opts.release_agent)
strcpy(root->release_agent_path, opts.release_agent);
out_unlock:
if (opts.release_agent)
kfree(opts.release_agent);
mutex_unlock(&cgroup_mutex);
mutex_unlock(&cont->dentry->d_inode->i_mutex);
return ret;
@ -756,6 +845,7 @@ static void init_cgroup_root(struct cgroupfs_root *root)
INIT_LIST_HEAD(&cont->sibling);
INIT_LIST_HEAD(&cont->children);
INIT_LIST_HEAD(&cont->css_sets);
INIT_LIST_HEAD(&cont->release_list);
}
static int cgroup_test_super(struct super_block *sb, void *data)
@ -830,8 +920,11 @@ static int cgroup_get_sb(struct file_system_type *fs_type,
/* First find the desired set of subsystems */
ret = parse_cgroupfs_options(data, &opts);
if (ret)
if (ret) {
if (opts.release_agent)
kfree(opts.release_agent);
return ret;
}
root = kzalloc(sizeof(*root), GFP_KERNEL);
if (!root)
@ -840,6 +933,10 @@ static int cgroup_get_sb(struct file_system_type *fs_type,
init_cgroup_root(root);
root->subsys_bits = opts.subsys_bits;
root->flags = opts.flags;
if (opts.release_agent) {
strcpy(root->release_agent_path, opts.release_agent);
kfree(opts.release_agent);
}
sb = sget(fs_type, cgroup_test_super, cgroup_set_super, root);
@ -1120,7 +1217,7 @@ static int attach_task(struct cgroup *cont, struct task_struct *tsk)
ss->attach(ss, cont, oldcont, tsk);
}
}
set_bit(CONT_RELEASABLE, &oldcont->flags);
synchronize_rcu();
put_css_set(cg);
return 0;
@ -1170,6 +1267,9 @@ enum cgroup_filetype {
FILE_ROOT,
FILE_DIR,
FILE_TASKLIST,
FILE_NOTIFY_ON_RELEASE,
FILE_RELEASABLE,
FILE_RELEASE_AGENT,
};
static ssize_t cgroup_write_uint(struct cgroup *cont, struct cftype *cft,
@ -1240,6 +1340,32 @@ static ssize_t cgroup_common_file_write(struct cgroup *cont,
case FILE_TASKLIST:
retval = attach_task_by_pid(cont, buffer);
break;
case FILE_NOTIFY_ON_RELEASE:
clear_bit(CONT_RELEASABLE, &cont->flags);
if (simple_strtoul(buffer, NULL, 10) != 0)
set_bit(CONT_NOTIFY_ON_RELEASE, &cont->flags);
else
clear_bit(CONT_NOTIFY_ON_RELEASE, &cont->flags);
break;
case FILE_RELEASE_AGENT:
{
struct cgroupfs_root *root = cont->root;
/* Strip trailing newline */
if (nbytes && (buffer[nbytes-1] == '\n')) {
buffer[nbytes-1] = 0;
}
if (nbytes < sizeof(root->release_agent_path)) {
/* We never write anything other than '\0'
* into the last char of release_agent_path,
* so it always remains a NUL-terminated
* string */
strncpy(root->release_agent_path, buffer, nbytes);
root->release_agent_path[nbytes] = 0;
} else {
retval = -ENOSPC;
}
break;
}
default:
retval = -EINVAL;
goto out2;
@ -1281,6 +1407,49 @@ static ssize_t cgroup_read_uint(struct cgroup *cont, struct cftype *cft,
return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
}
static ssize_t cgroup_common_file_read(struct cgroup *cont,
struct cftype *cft,
struct file *file,
char __user *buf,
size_t nbytes, loff_t *ppos)
{
enum cgroup_filetype type = cft->private;
char *page;
ssize_t retval = 0;
char *s;
if (!(page = (char *)__get_free_page(GFP_KERNEL)))
return -ENOMEM;
s = page;
switch (type) {
case FILE_RELEASE_AGENT:
{
struct cgroupfs_root *root;
size_t n;
mutex_lock(&cgroup_mutex);
root = cont->root;
n = strnlen(root->release_agent_path,
sizeof(root->release_agent_path));
n = min(n, (size_t) PAGE_SIZE);
strncpy(s, root->release_agent_path, n);
mutex_unlock(&cgroup_mutex);
s += n;
break;
}
default:
retval = -EINVAL;
goto out;
}
*s++ = '\n';
retval = simple_read_from_buffer(buf, nbytes, ppos, page, s - page);
out:
free_page((unsigned long)page);
return retval;
}
static ssize_t cgroup_file_read(struct file *file, char __user *buf,
size_t nbytes, loff_t *ppos)
{
@ -1699,16 +1868,49 @@ static int cgroup_tasks_release(struct inode *unused_inode,
return 0;
}
static u64 cgroup_read_notify_on_release(struct cgroup *cont,
struct cftype *cft)
{
return notify_on_release(cont);
}
static u64 cgroup_read_releasable(struct cgroup *cont, struct cftype *cft)
{
return test_bit(CONT_RELEASABLE, &cont->flags);
}
/*
* for the common functions, 'private' gives the type of file
*/
static struct cftype cft_tasks = {
.name = "tasks",
.open = cgroup_tasks_open,
.read = cgroup_tasks_read,
static struct cftype files[] = {
{
.name = "tasks",
.open = cgroup_tasks_open,
.read = cgroup_tasks_read,
.write = cgroup_common_file_write,
.release = cgroup_tasks_release,
.private = FILE_TASKLIST,
},
{
.name = "notify_on_release",
.read_uint = cgroup_read_notify_on_release,
.write = cgroup_common_file_write,
.private = FILE_NOTIFY_ON_RELEASE,
},
{
.name = "releasable",
.read_uint = cgroup_read_releasable,
.private = FILE_RELEASABLE,
}
};
static struct cftype cft_release_agent = {
.name = "release_agent",
.read = cgroup_common_file_read,
.write = cgroup_common_file_write,
.release = cgroup_tasks_release,
.private = FILE_TASKLIST,
.private = FILE_RELEASE_AGENT,
};
static int cgroup_populate_dir(struct cgroup *cont)
@ -1719,10 +1921,15 @@ static int cgroup_populate_dir(struct cgroup *cont)
/* First clear out any existing files */
cgroup_clear_directory(cont->dentry);
err = cgroup_add_file(cont, NULL, &cft_tasks);
err = cgroup_add_files(cont, NULL, files, ARRAY_SIZE(files));
if (err < 0)
return err;
if (cont == cont->top_cgroup) {
if ((err = cgroup_add_file(cont, NULL, &cft_release_agent)) < 0)
return err;
}
for_each_subsys(cont->root, ss) {
if (ss->populate && (err = ss->populate(ss, cont)) < 0)
return err;
@ -1779,6 +1986,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
INIT_LIST_HEAD(&cont->sibling);
INIT_LIST_HEAD(&cont->children);
INIT_LIST_HEAD(&cont->css_sets);
INIT_LIST_HEAD(&cont->release_list);
cont->parent = parent;
cont->root = parent->root;
@ -1840,6 +2048,38 @@ static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode)
return cgroup_create(c_parent, dentry, mode | S_IFDIR);
}
static inline int cgroup_has_css_refs(struct cgroup *cont)
{
/* Check the reference count on each subsystem. Since we
* already established that there are no tasks in the
* cgroup, if the css refcount is also 0, then there should
* be no outstanding references, so the subsystem is safe to
* destroy. We scan across all subsystems rather than using
* the per-hierarchy linked list of mounted subsystems since
* we can be called via check_for_release() with no
* synchronization other than RCU, and the subsystem linked
* list isn't RCU-safe */
int i;
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
struct cgroup_subsys_state *css;
/* Skip subsystems not in this hierarchy */
if (ss->root != cont->root)
continue;
css = cont->subsys[ss->subsys_id];
/* When called from check_for_release() it's possible
* that by this point the cgroup has been removed
* and the css deleted. But a false-positive doesn't
* matter, since it can only happen if the cgroup
* has been deleted and hence no longer needs the
* release agent to be called anyway. */
if (css && atomic_read(&css->refcnt)) {
return 1;
}
}
return 0;
}
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
{
struct cgroup *cont = dentry->d_fsdata;
@ -1848,7 +2088,6 @@ static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
struct cgroup_subsys *ss;
struct super_block *sb;
struct cgroupfs_root *root;
int css_busy = 0;
/* the vfs holds both inode->i_mutex already */
@ -1866,20 +2105,7 @@ static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
root = cont->root;
sb = root->sb;
/* Check the reference count on each subsystem. Since we
* already established that there are no tasks in the
* cgroup, if the css refcount is also 0, then there should
* be no outstanding references, so the subsystem is safe to
* destroy */
for_each_subsys(root, ss) {
struct cgroup_subsys_state *css;
css = cont->subsys[ss->subsys_id];
if (atomic_read(&css->refcnt)) {
css_busy = 1;
break;
}
}
if (css_busy) {
if (cgroup_has_css_refs(cont)) {
mutex_unlock(&cgroup_mutex);
return -EBUSY;
}
@ -1889,7 +2115,11 @@ static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
ss->destroy(ss, cont);
}
spin_lock(&release_list_lock);
set_bit(CONT_REMOVED, &cont->flags);
if (!list_empty(&cont->release_list))
list_del(&cont->release_list);
spin_unlock(&release_list_lock);
/* delete my sibling from parent->children */
list_del(&cont->sibling);
spin_lock(&cont->dentry->d_lock);
@ -1901,6 +2131,9 @@ static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
dput(d);
root->number_of_cgroups--;
set_bit(CONT_RELEASABLE, &parent->flags);
check_for_release(parent);
mutex_unlock(&cgroup_mutex);
/* Drop the active superblock reference that we took when we
* created the cgroup */
@ -1938,15 +2171,15 @@ static void cgroup_init_subsys(struct cgroup_subsys *ss)
/* If this subsystem requested that it be notified with fork
* events, we should send it one now for every process in the
* system */
if (ss->fork) {
struct task_struct *g, *p;
if (ss->fork) {
struct task_struct *g, *p;
read_lock(&tasklist_lock);
do_each_thread(g, p) {
ss->fork(ss, p);
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
}
read_lock(&tasklist_lock);
do_each_thread(g, p) {
ss->fork(ss, p);
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
}
need_forkexit_callback |= ss->fork || ss->exit;
@ -2263,7 +2496,7 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
tsk->cgroups = &init_css_set;
task_unlock(tsk);
if (cg)
put_css_set(cg);
put_css_set_taskexit(cg);
}
/**
@ -2374,7 +2607,10 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys)
out_release:
mutex_unlock(&inode->i_mutex);
mutex_lock(&cgroup_mutex);
put_css_set(cg);
mutex_unlock(&cgroup_mutex);
deactivate_super(parent->root->sb);
return ret;
}
@ -2404,3 +2640,111 @@ int cgroup_is_descendant(const struct cgroup *cont)
ret = (cont == target);
return ret;
}
static void check_for_release(struct cgroup *cont)
{
/* All of these checks rely on RCU to keep the cgroup
* structure alive */
if (cgroup_is_releasable(cont) && !atomic_read(&cont->count)
&& list_empty(&cont->children) && !cgroup_has_css_refs(cont)) {
/* Control Group is currently removeable. If it's not
* already queued for a userspace notification, queue
* it now */
int need_schedule_work = 0;
spin_lock(&release_list_lock);
if (!cgroup_is_removed(cont) &&
list_empty(&cont->release_list)) {
list_add(&cont->release_list, &release_list);
need_schedule_work = 1;
}
spin_unlock(&release_list_lock);
if (need_schedule_work)
schedule_work(&release_agent_work);
}
}
void __css_put(struct cgroup_subsys_state *css)
{
struct cgroup *cont = css->cgroup;
rcu_read_lock();
if (atomic_dec_and_test(&css->refcnt) && notify_on_release(cont)) {
set_bit(CONT_RELEASABLE, &cont->flags);
check_for_release(cont);
}
rcu_read_unlock();
}
/*
* Notify userspace when a cgroup is released, by running the
* configured release agent with the name of the cgroup (path
* relative to the root of cgroup file system) as the argument.
*
* Most likely, this user command will try to rmdir this cgroup.
*
* This races with the possibility that some other task will be
* attached to this cgroup before it is removed, or that some other
* user task will 'mkdir' a child cgroup of this cgroup. That's ok.
* The presumed 'rmdir' will fail quietly if this cgroup is no longer
* unused, and this cgroup will be reprieved from its death sentence,
* to continue to serve a useful existence. Next time it's released,
* we will get notified again, if it still has 'notify_on_release' set.
*
* The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
* means only wait until the task is successfully execve()'d. The
* separate release agent task is forked by call_usermodehelper(),
* then control in this thread returns here, without waiting for the
* release agent task. We don't bother to wait because the caller of
* this routine has no use for the exit status of the release agent
* task, so no sense holding our caller up for that.
*
*/
static void cgroup_release_agent(struct work_struct *work)
{
BUG_ON(work != &release_agent_work);
mutex_lock(&cgroup_mutex);
spin_lock(&release_list_lock);
while (!list_empty(&release_list)) {
char *argv[3], *envp[3];
int i;
char *pathbuf;
struct cgroup *cont = list_entry(release_list.next,
struct cgroup,
release_list);
list_del_init(&cont->release_list);
spin_unlock(&release_list_lock);
pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
if (!pathbuf) {
spin_lock(&release_list_lock);
continue;
}
if (cgroup_path(cont, pathbuf, PAGE_SIZE) < 0) {
kfree(pathbuf);
spin_lock(&release_list_lock);
continue;
}
i = 0;
argv[i++] = cont->root->release_agent_path;
argv[i++] = (char *)pathbuf;
argv[i] = NULL;
i = 0;
/* minimal command environment */
envp[i++] = "HOME=/";
envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
envp[i] = NULL;
/* Drop the lock while we invoke the usermode helper,
* since the exec could involve hitting disk and hence
* be a slow process */
mutex_unlock(&cgroup_mutex);
call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
kfree(pathbuf);
mutex_lock(&cgroup_mutex);
spin_lock(&release_list_lock);
}
spin_unlock(&release_list_lock);
mutex_unlock(&cgroup_mutex);
}