#include <linux/atomic.h>
+/*
+ * cgroup_mutex is the master lock. Any modification to cgroup or its
+ * hierarchy must be performed while holding it.
+ *
+ * cgroup_root_mutex nests inside cgroup_mutex and should be held to modify
+ * cgroupfs_root of any cgroup hierarchy - subsys list, flags,
+ * release_agent_path and so on. Modifying requires both cgroup_mutex and
+ * cgroup_root_mutex. Readers can acquire either of the two. This is to
+ * break the following locking order cycle.
+ *
+ * A. cgroup_mutex -> cred_guard_mutex -> s_type->i_mutex_key -> namespace_sem
+ * B. namespace_sem -> cgroup_mutex
+ *
+ * B happens only through cgroup_show_options() and using cgroup_root_mutex
+ * breaks it.
+ */
static DEFINE_MUTEX(cgroup_mutex);
+static DEFINE_MUTEX(cgroup_root_mutex);
/*
* Generate an array of cgroup subsystem pointers. At boot time, this is
* -> cgroup_mkdir.
*/
-static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode);
+static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode);
static struct dentry *cgroup_lookup(struct inode *, struct dentry *, struct nameidata *);
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
static int cgroup_populate_dir(struct cgroup *cgrp);
static int alloc_css_id(struct cgroup_subsys *ss,
struct cgroup *parent, struct cgroup *child);
-static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb)
+static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb)
{
struct inode *inode = new_inode(sb);
*
* CGRP_WAIT_ON_RMDIR flag is set under cgroup's inode->i_mutex;
*/
-DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq);
+static DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq);
static void cgroup_wakeup_rmdir_waiter(struct cgroup *cgrp)
{
int i;
BUG_ON(!mutex_is_locked(&cgroup_mutex));
+ BUG_ON(!mutex_is_locked(&cgroup_root_mutex));
removed_bits = root->actual_subsys_bits & ~final_bits;
added_bits = final_bits & ~root->actual_subsys_bits;
return 0;
}
-static int cgroup_show_options(struct seq_file *seq, struct vfsmount *vfs)
+static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
{
- struct cgroupfs_root *root = vfs->mnt_sb->s_fs_info;
+ struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
struct cgroup_subsys *ss;
- mutex_lock(&cgroup_mutex);
+ mutex_lock(&cgroup_root_mutex);
for_each_subsys(root, ss)
seq_printf(seq, ",%s", ss->name);
if (test_bit(ROOT_NOPREFIX, &root->flags))
seq_puts(seq, ",clone_children");
if (strlen(root->name))
seq_printf(seq, ",name=%s", root->name);
- mutex_unlock(&cgroup_mutex);
+ mutex_unlock(&cgroup_root_mutex);
return 0;
}
/*
* If the 'all' option was specified select all the subsystems,
- * otherwise 'all, 'none' and a subsystem name options were not
- * specified, let's default to 'all'
+ * otherwise if 'none', 'name=' and a subsystem name options
+ * were not specified, let's default to 'all'
*/
- if (all_ss || (!all_ss && !one_ss && !opts->none)) {
+ if (all_ss || (!one_ss && !opts->none && !opts->name)) {
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
if (ss == NULL)
mutex_lock(&cgrp->dentry->d_inode->i_mutex);
mutex_lock(&cgroup_mutex);
+ mutex_lock(&cgroup_root_mutex);
/* See what subsystems are wanted */
ret = parse_cgroupfs_options(data, &opts);
out_unlock:
kfree(opts.release_agent);
kfree(opts.name);
+ mutex_unlock(&cgroup_root_mutex);
mutex_unlock(&cgroup_mutex);
mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
return ret;
int ret = 0;
struct super_block *sb;
struct cgroupfs_root *new_root;
+ struct inode *inode;
/* First find the desired set of subsystems */
mutex_lock(&cgroup_mutex);
/* We used the new root structure, so this is a new hierarchy */
struct list_head tmp_cg_links;
struct cgroup *root_cgrp = &root->top_cgroup;
- struct inode *inode;
struct cgroupfs_root *existing_root;
const struct cred *cred;
int i;
mutex_lock(&inode->i_mutex);
mutex_lock(&cgroup_mutex);
+ mutex_lock(&cgroup_root_mutex);
- if (strlen(root->name)) {
- /* Check for name clashes with existing mounts */
- for_each_active_root(existing_root) {
- if (!strcmp(existing_root->name, root->name)) {
- ret = -EBUSY;
- mutex_unlock(&cgroup_mutex);
- mutex_unlock(&inode->i_mutex);
- goto drop_new_super;
- }
- }
- }
+ /* Check for name clashes with existing mounts */
+ ret = -EBUSY;
+ if (strlen(root->name))
+ for_each_active_root(existing_root)
+ if (!strcmp(existing_root->name, root->name))
+ goto unlock_drop;
/*
* We're accessing css_set_count without locking
* have some link structures left over
*/
ret = allocate_cg_links(css_set_count, &tmp_cg_links);
- if (ret) {
- mutex_unlock(&cgroup_mutex);
- mutex_unlock(&inode->i_mutex);
- goto drop_new_super;
- }
+ if (ret)
+ goto unlock_drop;
ret = rebind_subsystems(root, root->subsys_bits);
if (ret == -EBUSY) {
- mutex_unlock(&cgroup_mutex);
- mutex_unlock(&inode->i_mutex);
free_cg_links(&tmp_cg_links);
- goto drop_new_super;
+ goto unlock_drop;
}
/*
* There must be no failure case after here, since rebinding
cred = override_creds(&init_cred);
cgroup_populate_dir(root_cgrp);
revert_creds(cred);
+ mutex_unlock(&cgroup_root_mutex);
mutex_unlock(&cgroup_mutex);
mutex_unlock(&inode->i_mutex);
} else {
kfree(opts.name);
return dget(sb->s_root);
+ unlock_drop:
+ mutex_unlock(&cgroup_root_mutex);
+ mutex_unlock(&cgroup_mutex);
+ mutex_unlock(&inode->i_mutex);
drop_new_super:
deactivate_locked_super(sb);
drop_modules:
BUG_ON(!list_empty(&cgrp->sibling));
mutex_lock(&cgroup_mutex);
+ mutex_lock(&cgroup_root_mutex);
/* Rebind all subsystems back to the default hierarchy */
ret = rebind_subsystems(root, 0);
root_count--;
}
+ mutex_unlock(&cgroup_root_mutex);
mutex_unlock(&cgroup_mutex);
kill_litter_super(sb);
}
EXPORT_SYMBOL_GPL(cgroup_path);
+/*
+ * Control Group taskset
+ */
+struct task_and_cgroup {
+ struct task_struct *task;
+ struct cgroup *cgrp;
+};
+
+struct cgroup_taskset {
+ struct task_and_cgroup single;
+ struct flex_array *tc_array;
+ int tc_array_len;
+ int idx;
+ struct cgroup *cur_cgrp;
+};
+
+/**
+ * cgroup_taskset_first - reset taskset and return the first task
+ * @tset: taskset of interest
+ *
+ * @tset iteration is initialized and the first task is returned.
+ */
+struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset)
+{
+ if (tset->tc_array) {
+ tset->idx = 0;
+ return cgroup_taskset_next(tset);
+ } else {
+ tset->cur_cgrp = tset->single.cgrp;
+ return tset->single.task;
+ }
+}
+EXPORT_SYMBOL_GPL(cgroup_taskset_first);
+
+/**
+ * cgroup_taskset_next - iterate to the next task in taskset
+ * @tset: taskset of interest
+ *
+ * Return the next task in @tset. Iteration must have been initialized
+ * with cgroup_taskset_first().
+ */
+struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset)
+{
+ struct task_and_cgroup *tc;
+
+ if (!tset->tc_array || tset->idx >= tset->tc_array_len)
+ return NULL;
+
+ tc = flex_array_get(tset->tc_array, tset->idx++);
+ tset->cur_cgrp = tc->cgrp;
+ return tc->task;
+}
+EXPORT_SYMBOL_GPL(cgroup_taskset_next);
+
+/**
+ * cgroup_taskset_cur_cgroup - return the matching cgroup for the current task
+ * @tset: taskset of interest
+ *
+ * Return the cgroup for the current (last returned) task of @tset. This
+ * function must be preceded by either cgroup_taskset_first() or
+ * cgroup_taskset_next().
+ */
+struct cgroup *cgroup_taskset_cur_cgroup(struct cgroup_taskset *tset)
+{
+ return tset->cur_cgrp;
+}
+EXPORT_SYMBOL_GPL(cgroup_taskset_cur_cgroup);
+
+/**
+ * cgroup_taskset_size - return the number of tasks in taskset
+ * @tset: taskset of interest
+ */
+int cgroup_taskset_size(struct cgroup_taskset *tset)
+{
+ return tset->tc_array ? tset->tc_array_len : 1;
+}
+EXPORT_SYMBOL_GPL(cgroup_taskset_size);
+
+
/*
* cgroup_task_migrate - move a task from one cgroup to another.
*
* 'guarantee' is set if the caller promises that a new css_set for the task
* will already exist. If not set, this function might sleep, and can fail with
- * -ENOMEM. Otherwise, it can only fail with -ESRCH.
+ * -ENOMEM. Must be called with cgroup_mutex and threadgroup locked.
*/
static int cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp,
struct task_struct *tsk, bool guarantee)
struct css_set *newcg;
/*
- * get old css_set. we need to take task_lock and refcount it, because
- * an exiting task can change its css_set to init_css_set and drop its
- * old one without taking cgroup_mutex.
+ * We are synchronized through threadgroup_lock() against PF_EXITING
+ * setting such that we can't race against cgroup_exit() changing the
+ * css_set to init_css_set and dropping the old one.
*/
- task_lock(tsk);
+ WARN_ON_ONCE(tsk->flags & PF_EXITING);
oldcg = tsk->cgroups;
- get_css_set(oldcg);
- task_unlock(tsk);
/* locate or allocate a new css_set for this task. */
if (guarantee) {
might_sleep();
/* find_css_set will give us newcg already referenced. */
newcg = find_css_set(oldcg, cgrp);
- if (!newcg) {
- put_css_set(oldcg);
+ if (!newcg)
return -ENOMEM;
- }
}
- put_css_set(oldcg);
- /* if PF_EXITING is set, the tsk->cgroups pointer is no longer safe. */
task_lock(tsk);
- if (tsk->flags & PF_EXITING) {
- task_unlock(tsk);
- put_css_set(newcg);
- return -ESRCH;
- }
rcu_assign_pointer(tsk->cgroups, newcg);
task_unlock(tsk);
* @cgrp: the cgroup the task is attaching to
* @tsk: the task to be attached
*
- * Call holding cgroup_mutex. May take task_lock of
- * the task 'tsk' during call.
+ * Call with cgroup_mutex and threadgroup locked. May take task_lock of
+ * @tsk during call.
*/
int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
{
struct cgroup_subsys *ss, *failed_ss = NULL;
struct cgroup *oldcgrp;
struct cgroupfs_root *root = cgrp->root;
+ struct cgroup_taskset tset = { };
+
+ /* @tsk either already exited or can't exit until the end */
+ if (tsk->flags & PF_EXITING)
+ return -ESRCH;
/* Nothing to do if the task is already in that cgroup */
oldcgrp = task_cgroup_from_root(tsk, root);
if (cgrp == oldcgrp)
return 0;
+ tset.single.task = tsk;
+ tset.single.cgrp = oldcgrp;
+
for_each_subsys(root, ss) {
if (ss->can_attach) {
- retval = ss->can_attach(ss, cgrp, tsk);
+ retval = ss->can_attach(ss, cgrp, &tset);
if (retval) {
/*
* Remember on which subsystem the can_attach()
goto out;
}
}
- if (ss->can_attach_task) {
- retval = ss->can_attach_task(cgrp, tsk);
- if (retval) {
- failed_ss = ss;
- goto out;
- }
- }
}
retval = cgroup_task_migrate(cgrp, oldcgrp, tsk, false);
goto out;
for_each_subsys(root, ss) {
- if (ss->pre_attach)
- ss->pre_attach(cgrp);
- if (ss->attach_task)
- ss->attach_task(cgrp, tsk);
if (ss->attach)
- ss->attach(ss, cgrp, oldcgrp, tsk);
+ ss->attach(ss, cgrp, &tset);
}
synchronize_rcu();
*/
break;
if (ss->cancel_attach)
- ss->cancel_attach(ss, cgrp, tsk);
+ ss->cancel_attach(ss, cgrp, &tset);
}
}
return retval;
read_lock(&css_set_lock);
newcg = find_existing_css_set(cg, cgrp, template);
- if (newcg)
- get_css_set(newcg);
read_unlock(&css_set_lock);
/* doesn't exist at all? */
if (!newcg)
return false;
/* see if it's already in the list */
- list_for_each_entry(cg_entry, newcg_list, links) {
- if (cg_entry->cg == newcg) {
- put_css_set(newcg);
+ list_for_each_entry(cg_entry, newcg_list, links)
+ if (cg_entry->cg == newcg)
return true;
- }
- }
/* not found */
- put_css_set(newcg);
return false;
}
* @cgrp: the cgroup to attach to
* @leader: the threadgroup leader task_struct of the group to be attached
*
- * Call holding cgroup_mutex and the threadgroup_fork_lock of the leader. Will
- * take task_lock of each thread in leader's threadgroup individually in turn.
+ * Call holding cgroup_mutex and the group_rwsem of the leader. Will take
+ * task_lock of each thread in leader's threadgroup individually in turn.
*/
-int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
+static int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
{
int retval, i, group_size;
struct cgroup_subsys *ss, *failed_ss = NULL;
- bool cancel_failed_ss = false;
/* guaranteed to be initialized later, but the compiler needs this */
- struct cgroup *oldcgrp = NULL;
struct css_set *oldcg;
struct cgroupfs_root *root = cgrp->root;
/* threadgroup list cursor and array */
struct task_struct *tsk;
+ struct task_and_cgroup *tc;
struct flex_array *group;
+ struct cgroup_taskset tset = { };
/*
* we need to make sure we have css_sets for all the tasks we're
* going to move -before- we actually start moving them, so that in
* step 0: in order to do expensive, possibly blocking operations for
* every thread, we cannot iterate the thread group list, since it needs
* rcu or tasklist locked. instead, build an array of all threads in the
- * group - threadgroup_fork_lock prevents new threads from appearing,
- * and if threads exit, this will just be an over-estimate.
+ * group - group_rwsem prevents new threads from appearing, and if
+ * threads exit, this will just be an over-estimate.
*/
group_size = get_nr_threads(leader);
/* flex_array supports very large thread-groups better than kmalloc. */
- group = flex_array_alloc(sizeof(struct task_struct *), group_size,
- GFP_KERNEL);
+ group = flex_array_alloc(sizeof(*tc), group_size, GFP_KERNEL);
if (!group)
return -ENOMEM;
/* pre-allocate to guarantee space while iterating in rcu read-side. */
retval = -EAGAIN;
goto out_free_group_list;
}
- /* take a reference on each task in the group to go in the array. */
+
tsk = leader;
i = 0;
do {
+ struct task_and_cgroup ent;
+
+ /* @tsk either already exited or can't exit until the end */
+ if (tsk->flags & PF_EXITING)
+ continue;
+
/* as per above, nr_threads may decrease, but not increase. */
BUG_ON(i >= group_size);
- get_task_struct(tsk);
/*
* saying GFP_ATOMIC has no effect here because we did prealloc
* earlier, but it's good form to communicate our expectations.
*/
- retval = flex_array_put_ptr(group, i, tsk, GFP_ATOMIC);
+ ent.task = tsk;
+ ent.cgrp = task_cgroup_from_root(tsk, root);
+ /* nothing to do if this task is already in the cgroup */
+ if (ent.cgrp == cgrp)
+ continue;
+ retval = flex_array_put(group, i, &ent, GFP_ATOMIC);
BUG_ON(retval != 0);
i++;
} while_each_thread(leader, tsk);
/* remember the number of threads in the array for later. */
group_size = i;
+ tset.tc_array = group;
+ tset.tc_array_len = group_size;
read_unlock(&tasklist_lock);
+ /* methods shouldn't be called if no task is actually migrating */
+ retval = 0;
+ if (!group_size)
+ goto out_free_group_list;
+
/*
* step 1: check that we can legitimately attach to the cgroup.
*/
for_each_subsys(root, ss) {
if (ss->can_attach) {
- retval = ss->can_attach(ss, cgrp, leader);
+ retval = ss->can_attach(ss, cgrp, &tset);
if (retval) {
failed_ss = ss;
goto out_cancel_attach;
}
}
- /* a callback to be run on every thread in the threadgroup. */
- if (ss->can_attach_task) {
- /* run on each task in the threadgroup. */
- for (i = 0; i < group_size; i++) {
- tsk = flex_array_get_ptr(group, i);
- retval = ss->can_attach_task(cgrp, tsk);
- if (retval) {
- failed_ss = ss;
- cancel_failed_ss = true;
- goto out_cancel_attach;
- }
- }
- }
}
/*
*/
INIT_LIST_HEAD(&newcg_list);
for (i = 0; i < group_size; i++) {
- tsk = flex_array_get_ptr(group, i);
- /* nothing to do if this task is already in the cgroup */
- oldcgrp = task_cgroup_from_root(tsk, root);
- if (cgrp == oldcgrp)
- continue;
- /* get old css_set pointer */
- task_lock(tsk);
- oldcg = tsk->cgroups;
- get_css_set(oldcg);
- task_unlock(tsk);
- /* see if the new one for us is already in the list? */
- if (css_set_check_fetched(cgrp, tsk, oldcg, &newcg_list)) {
- /* was already there, nothing to do. */
- put_css_set(oldcg);
- } else {
- /* we don't already have it. get new one. */
+ tc = flex_array_get(group, i);
+ oldcg = tc->task->cgroups;
+
+ /* if we don't already have it in the list get a new one */
+ if (!css_set_check_fetched(cgrp, tc->task, oldcg,
+ &newcg_list)) {
retval = css_set_prefetch(cgrp, oldcg, &newcg_list);
- put_css_set(oldcg);
if (retval)
goto out_list_teardown;
}
}
/*
- * step 3: now that we're guaranteed success wrt the css_sets, proceed
- * to move all tasks to the new cgroup, calling ss->attach_task for each
- * one along the way. there are no failure cases after here, so this is
- * the commit point.
+ * step 3: now that we're guaranteed success wrt the css_sets,
+ * proceed to move all tasks to the new cgroup. There are no
+ * failure cases after here, so this is the commit point.
*/
- for_each_subsys(root, ss) {
- if (ss->pre_attach)
- ss->pre_attach(cgrp);
- }
for (i = 0; i < group_size; i++) {
- tsk = flex_array_get_ptr(group, i);
- /* leave current thread as it is if it's already there */
- oldcgrp = task_cgroup_from_root(tsk, root);
- if (cgrp == oldcgrp)
- continue;
- /* if the thread is PF_EXITING, it can just get skipped. */
- retval = cgroup_task_migrate(cgrp, oldcgrp, tsk, true);
- if (retval == 0) {
- /* attach each task to each subsystem */
- for_each_subsys(root, ss) {
- if (ss->attach_task)
- ss->attach_task(cgrp, tsk);
- }
- } else {
- BUG_ON(retval != -ESRCH);
- }
+ tc = flex_array_get(group, i);
+ retval = cgroup_task_migrate(cgrp, tc->cgrp, tc->task, true);
+ BUG_ON(retval);
}
/* nothing is sensitive to fork() after this point. */
/*
- * step 4: do expensive, non-thread-specific subsystem callbacks.
- * TODO: if ever a subsystem needs to know the oldcgrp for each task
- * being moved, this call will need to be reworked to communicate that.
+ * step 4: do subsystem attach callbacks.
*/
for_each_subsys(root, ss) {
if (ss->attach)
- ss->attach(ss, cgrp, oldcgrp, leader);
+ ss->attach(ss, cgrp, &tset);
}
/*
/* same deal as in cgroup_attach_task */
if (retval) {
for_each_subsys(root, ss) {
- if (ss == failed_ss) {
- if (cancel_failed_ss && ss->cancel_attach)
- ss->cancel_attach(ss, cgrp, leader);
+ if (ss == failed_ss)
break;
- }
if (ss->cancel_attach)
- ss->cancel_attach(ss, cgrp, leader);
+ ss->cancel_attach(ss, cgrp, &tset);
}
}
- /* clean up the array of referenced threads in the group. */
- for (i = 0; i < group_size; i++) {
- tsk = flex_array_get_ptr(group, i);
- put_task_struct(tsk);
- }
out_free_group_list:
flex_array_free(group);
return retval;
/*
* Find the task_struct of the task to attach by vpid and pass it along to the
- * function to attach either it or all tasks in its threadgroup. Will take
- * cgroup_mutex; may take task_lock of task.
+ * function to attach either it or all tasks in its threadgroup. Will lock
+ * cgroup_mutex and threadgroup; may take task_lock of task.
*/
static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
{
* detect it later.
*/
tsk = tsk->group_leader;
- } else if (tsk->flags & PF_EXITING) {
- /* optimization for the single-task-only case */
- rcu_read_unlock();
- cgroup_unlock();
- return -ESRCH;
}
-
/*
* even if we're attaching all tasks in the thread group, we
* only need to check permissions on one of them.
get_task_struct(tsk);
}
- if (threadgroup) {
- threadgroup_fork_write_lock(tsk);
+ threadgroup_lock(tsk);
+
+ if (threadgroup)
ret = cgroup_attach_proc(cgrp, tsk);
- threadgroup_fork_write_unlock(tsk);
- } else {
+ else
ret = cgroup_attach_task(cgrp, tsk);
- }
+
+ threadgroup_unlock(tsk);
+
put_task_struct(tsk);
cgroup_unlock();
return ret;
return -EINVAL;
if (!cgroup_lock_live_group(cgrp))
return -ENODEV;
+ mutex_lock(&cgroup_root_mutex);
strcpy(cgrp->root->release_agent_path, buffer);
+ mutex_unlock(&cgroup_root_mutex);
cgroup_unlock();
return 0;
}
return __d_cft(file->f_dentry);
}
-static int cgroup_create_file(struct dentry *dentry, mode_t mode,
+static int cgroup_create_file(struct dentry *dentry, umode_t mode,
struct super_block *sb)
{
struct inode *inode;
* @mode: mode to set on new directory.
*/
static int cgroup_create_dir(struct cgroup *cgrp, struct dentry *dentry,
- mode_t mode)
+ umode_t mode)
{
struct dentry *parent;
int error = 0;
* returns S_IRUGO if it has only a read handler
* returns S_IWUSR if it has only a write hander
*/
-static mode_t cgroup_file_mode(const struct cftype *cft)
+static umode_t cgroup_file_mode(const struct cftype *cft)
{
- mode_t mode = 0;
+ umode_t mode = 0;
if (cft->mode)
return cft->mode;
struct dentry *dir = cgrp->dentry;
struct dentry *dentry;
int error;
- mode_t mode;
+ umode_t mode;
char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
}
void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
+ __acquires(css_set_lock)
{
/*
* The first time anyone tries to iterate across a cgroup,
}
void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
+ __releases(css_set_lock)
{
read_unlock(&css_set_lock);
}
* Must be called with the mutex on the parent inode held
*/
static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
- mode_t mode)
+ umode_t mode)
{
struct cgroup *cgrp;
struct cgroupfs_root *root = parent->root;
return err;
}
-static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode)
+static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
struct cgroup *c_parent = dentry->d_parent->d_fsdata;
*
* A pointer to the shared css_set was automatically copied in
* fork.c by dup_task_struct(). However, we ignore that copy, since
- * it was not made under the protection of RCU or cgroup_mutex, so
- * might no longer be a valid cgroup pointer. cgroup_attach_task() might
- * have already changed current->cgroups, allowing the previously
- * referenced cgroup group to be removed and freed.
+ * it was not made under the protection of RCU, cgroup_mutex or
+ * threadgroup_change_begin(), so it might no longer be a valid
+ * cgroup pointer. cgroup_attach_task() might have already changed
+ * current->cgroups, allowing the previously referenced cgroup
+ * group to be removed and freed.
+ *
+ * Outside the pointer validity we also need to process the css_set
+ * inheritance between threadgoup_change_begin() and
+ * threadgoup_change_end(), this way there is no leak in any process
+ * wide migration performed by cgroup_attach_proc() that could otherwise
+ * miss a thread because it is too early or too late in the fork stage.
*
* At the point that cgroup_fork() is called, 'current' is the parent
* task, and the passed argument 'child' points to the child task.
*/
void cgroup_fork(struct task_struct *child)
{
- task_lock(current);
+ /*
+ * We don't need to task_lock() current because current->cgroups
+ * can't be changed concurrently here. The parent obviously hasn't
+ * exited and called cgroup_exit(), and we are synchronized against
+ * cgroup migration through threadgroup_change_begin().
+ */
child->cgroups = current->cgroups;
get_css_set(child->cgroups);
- task_unlock(current);
INIT_LIST_HEAD(&child->cg_list);
}
{
if (use_task_css_set_links) {
write_lock(&css_set_lock);
- task_lock(child);
- if (list_empty(&child->cg_list))
+ if (list_empty(&child->cg_list)) {
+ /*
+ * It's safe to use child->cgroups without task_lock()
+ * here because we are protected through
+ * threadgroup_change_begin() against concurrent
+ * css_set change in cgroup_task_migrate(). Also
+ * the task can't exit at that point until
+ * wake_up_new_task() is called, so we are protected
+ * against cgroup_exit() setting child->cgroup to
+ * init_css_set.
+ */
list_add(&child->cg_list, &child->cgroups->tasks);
- task_unlock(child);
+ }
write_unlock(&css_set_lock);
}
}
git.openpandora.org / pandora-kernel.git / blobdiff