#ifndef _LINUX_CGROUP_H
#define _LINUX_CGROUP_H
/*
* cgroup interface
*
* Copyright (C) 2003 BULL SA
* Copyright (C) 2004-2006 Silicon Graphics, Inc.
*
*/
#include <linux/sched.h>
#include <linux/cpumask.h>
#include <linux/nodemask.h>
#include <linux/rculist.h>
#include <linux/cgroupstats.h>
#include <linux/rwsem.h>
#include <linux/fs.h>
#include <linux/seq_file.h>
#include <linux/kernfs.h>
#include <linux/cgroup-defs.h>
#ifdef CONFIG_CGROUPS
extern int cgroup_init_early(void);
extern int cgroup_init(void);
extern void cgroup_fork(struct task_struct *p);
extern void cgroup_post_fork(struct task_struct *p);
extern void cgroup_exit(struct task_struct *p);
extern int cgroupstats_build(struct cgroupstats *stats,
struct dentry *dentry);
extern int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
struct pid *pid, struct task_struct *tsk);
/**
* css_get - obtain a reference on the specified css
* @css: target css
*
* The caller must already have a reference.
*/
static inline void css_get(struct cgroup_subsys_state *css)
{
if (!(css->flags & CSS_NO_REF))
percpu_ref_get(&css->refcnt);
}
/**
* css_get_many - obtain references on the specified css
* @css: target css
* @n: number of references to get
*
* The caller must already have a reference.
*/
static inline void css_get_many(struct cgroup_subsys_state *css, unsigned int n)
{
if (!(css->flags & CSS_NO_REF))
percpu_ref_get_many(&css->refcnt, n);
}
/**
* css_tryget - try to obtain a reference on the specified css
* @css: target css
*
* Obtain a reference on @css unless it already has reached zero and is
* being released. This function doesn't care whether @css is on or
* offline. The caller naturally needs to ensure that @css is accessible
* but doesn't have to be holding a reference on it - IOW, RCU protected
* access is good enough for this function. Returns %true if a reference
* count was successfully obtained; %false otherwise.
*/
static inline bool css_tryget(struct cgroup_subsys_state *css)
{
if (!(css->flags & CSS_NO_REF))
return percpu_ref_tryget(&css->refcnt);
return true;
}
/**
* css_tryget_online - try to obtain a reference on the specified css if online
* @css: target css
*
* Obtain a reference on @css if it's online. The caller naturally needs
* to ensure that @css is accessible but doesn't have to be holding a
* reference on it - IOW, RCU protected access is good enough for this
* function. Returns %true if a reference count was successfully obtained;
* %false otherwise.
*/
static inline bool css_tryget_online(struct cgroup_subsys_state *css)
{
if (!(css->flags & CSS_NO_REF))
return percpu_ref_tryget_live(&css->refcnt);
return true;
}
/**
* css_put - put a css reference
* @css: target css
*
* Put a reference obtained via css_get() and css_tryget_online().
*/
static inline void css_put(struct cgroup_subsys_state *css)
{
if (!(css->flags & CSS_NO_REF))
percpu_ref_put(&css->refcnt);
}
/**
* css_put_many - put css references
* @css: target css
* @n: number of references to put
*
* Put references obtained via css_get() and css_tryget_online().
*/
static inline void css_put_many(struct cgroup_subsys_state *css, unsigned int n)
{
if (!(css->flags & CSS_NO_REF))
percpu_ref_put_many(&css->refcnt, n);
}
extern struct cgroup_root cgrp_dfl_root;
extern struct css_set init_css_set;
/**
* cgroup_on_dfl - test whether a cgroup is on the default hierarchy
* @cgrp: the cgroup of interest
*
* The default hierarchy is the v2 interface of cgroup and this function
* can be used to test whether a cgroup is on the default hierarchy for
* cases where a subsystem should behave differnetly depending on the
* interface version.
*
* The set of behaviors which change on the default hierarchy are still
* being determined and the mount option is prefixed with __DEVEL__.
*
* List of changed behaviors:
*
* - Mount options "noprefix", "xattr", "clone_children", "release_agent"
* and "name" are disallowed.
*
* - When mounting an existing superblock, mount options should match.
*
* - Remount is disallowed.
*
* - rename(2) is disallowed.
*
* - "tasks" is removed. Everything should be at process granularity. Use
* "cgroup.procs" instead.
*
* - "cgroup.procs" is not sorted. pids will be unique unless they got
* recycled inbetween reads.
*
* - "release_agent" and "notify_on_release" are removed. Replacement
* notification mechanism will be implemented.
*
* - "cgroup.clone_children" is removed.
*
* - "cgroup.subtree_populated" is available. Its value is 0 if the cgroup
* and its descendants contain no task; otherwise, 1. The file also
* generates kernfs notification which can be monitored through poll and
* [di]notify when the value of the file changes.
*
* - cpuset: tasks will be kept in empty cpusets when hotplug happens and
* take masks of ancestors with non-empty cpus/mems, instead of being
* moved to an ancestor.
*
* - cpuset: a task can be moved into an empty cpuset, and again it takes
* masks of ancestors.
*
* - memcg: use_hierarchy is on by default and the cgroup file for the flag
* is not created.
*
* - blkcg: blk-throttle becomes properly hierarchical.
*
* - debug: disallowed on the default hierarchy.
*/
static inline bool cgroup_on_dfl(const struct cgroup *cgrp)
{
return cgrp->root == &cgrp_dfl_root;
}
/* no synchronization, the result can only be used as a hint */
static inline bool cgroup_has_tasks(struct cgroup *cgrp)
{
return !list_empty(&cgrp->cset_links);
}
/* returns ino associated with a cgroup */
static inline ino_t cgroup_ino(struct cgroup *cgrp)
{
return cgrp->kn->ino;
}
/* cft/css accessors for cftype->write() operation */
static inline struct cftype *of_cft(struct kernfs_open_file *of)
{
return of->kn->priv;
}
struct cgroup_subsys_state *of_css(struct kernfs_open_file *of);
/* cft/css accessors for cftype->seq_*() operations */
static inline struct cftype *seq_cft(struct seq_file *seq)
{
return of_cft(seq->private);
}
static inline struct cgroup_subsys_state *seq_css(struct seq_file *seq)
{
return of_css(seq->private);
}
/*
* Name / path handling functions. All are thin wrappers around the kernfs
* counterparts and can be called under any context.
*/
static inline int cgroup_name(struct cgroup *cgrp, char *buf, size_t buflen)
{
return kernfs_name(cgrp->kn, buf, buflen);
}
static inline char * __must_check cgroup_path(struct cgroup *cgrp, char *buf,
size_t buflen)
{
return kernfs_path(cgrp->kn, buf, buflen);
}
static inline void pr_cont_cgroup_name(struct cgroup *cgrp)
{
pr_cont_kernfs_name(cgrp->kn);
}
static inline void pr_cont_cgroup_path(struct cgroup *cgrp)
{
pr_cont_kernfs_path(cgrp->kn);
}
char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen);
int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
int cgroup_rm_cftypes(struct cftype *cfts);
bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor);
struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset);
struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset);
/**
* cgroup_taskset_for_each - iterate cgroup_taskset
* @task: the loop cursor
* @tset: taskset to iterate
*/
#define cgroup_taskset_for_each(task, tset) \
for ((task) = cgroup_taskset_first((tset)); (task); \
(task) = cgroup_taskset_next((tset)))
#define SUBSYS(_x) extern struct cgroup_subsys _x ## _cgrp_subsys;
#include <linux/cgroup_subsys.h>
#undef SUBSYS
/**
* task_css_set_check - obtain a task's css_set with extra access conditions
* @task: the task to obtain css_set for
* @__c: extra condition expression to be passed to rcu_dereference_check()
*
* A task's css_set is RCU protected, initialized and exited while holding
* task_lock(), and can only be modified while holding both cgroup_mutex
* and task_lock() while the task is alive. This macro verifies that the
* caller is inside proper critical section and returns @task's css_set.
*
* The caller can also specify additional allowed conditions via @__c, such
* as locks used during the cgroup_subsys::attach() methods.
*/
#ifdef CONFIG_PROVE_RCU
extern struct mutex cgroup_mutex;
extern struct rw_semaphore css_set_rwsem;
#define task_css_set_check(task, __c) \
rcu_dereference_check((task)->cgroups, \
lockdep_is_held(&cgroup_mutex) || \
lockdep_is_held(&css_set_rwsem) || \
((task)->flags & PF_EXITING) || (__c))
#else
#define task_css_set_check(task, __c) \
rcu_dereference((task)->cgroups)
#endif
/**
* task_css_check - obtain css for (task, subsys) w/ extra access conds
* @task: the target task
* @subsys_id: the target subsystem ID
* @__c: extra condition expression to be passed to rcu_dereference_check()
*
* Return the cgroup_subsys_state for the (@task, @subsys_id) pair. The
* synchronization rules are the same as task_css_set_check().
*/
#define task_css_check(task, subsys_id, __c) \
task_css_set_check((task), (__c))->subsys[(subsys_id)]
/**
* task_css_set - obtain a task's css_set
* @task: the task to obtain css_set for
*
* See task_css_set_check().
*/
static inline struct css_set *task_css_set(struct task_struct *task)
{
return task_css_set_check(task, false);
}
/**
* task_css - obtain css for (task, subsys)
* @task: the target task
* @subsys_id: the target subsystem ID
*
* See task_css_check().
*/
static inline struct cgroup_subsys_state *task_css(struct task_struct *task,
int subsys_id)
{
return task_css_check(task, subsys_id, false);
}
/**
* task_css_is_root - test whether a task belongs to the root css
* @task: the target task
* @subsys_id: the target subsystem ID
*
* Test whether @task belongs to the root css on the specified subsystem.
* May be invoked in any context.
*/
static inline bool task_css_is_root(struct task_struct *task, int subsys_id)
{
return task_css_check(task, subsys_id, true) ==
init_css_set.subsys[subsys_id];
}
static inline struct cgroup *task_cgroup(struct task_struct *task,
int subsys_id)
{
return task_css(task, subsys_id)->cgroup;
}
struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos,
struct cgroup_subsys_state *parent);
struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss);
/**
* css_for_each_child - iterate through children of a css
* @pos: the css * to use as the loop cursor
* @parent: css whose children to walk
*
* Walk @parent's children. Must be called under rcu_read_lock().
*
* If a subsystem synchronizes ->css_online() and the start of iteration, a
* css which finished ->css_online() is guaranteed to be visible in the
* future iterations and will stay visible until the last reference is put.
* A css which hasn't finished ->css_online() or already finished
* ->css_offline() may show up during traversal. It's each subsystem's
* responsibility to synchronize against on/offlining.
*
* It is allowed to temporarily drop RCU read lock during iteration. The
* caller is responsible for ensuring that @pos remains accessible until
* the start of the next iteration by, for example, bumping the css refcnt.
*/
#define css_for_each_child(pos, parent) \
for ((pos) = css_next_child(NULL, (parent)); (pos); \
(pos) = css_next_child((pos), (parent)))
struct cgroup_subsys_state *
css_next_descendant_pre(struct cgroup_subsys_state *pos,
struct cgroup_subsys_state *css);
struct cgroup_subsys_state *
css_rightmost_descendant(struct cgroup_subsys_state *pos);
/**
* css_for_each_descendant_pre - pre-order walk of a css's descendants
* @pos: the css * to use as the loop cursor
* @root: css whose descendants to walk
*
* Walk @root's descendants. @root is included in the iteration and the
* first node to be visited. Must be called under rcu_read_lock().
*
* If a subsystem synchronizes ->css_online() and the start of iteration, a
* css which finished ->css_online() is guaranteed to be visible in the
* future iterations and will stay visible until the last reference is put.
* A css which hasn't finished ->css_online() or already finished
* ->css_offline() may show up during traversal. It's each subsystem's
* responsibility to synchronize against on/offlining.
*
* For example, the following guarantees that a descendant can't escape
* state updates of its ancestors.
*
* my_online(@css)
* {
* Lock @css's parent and @css;
* Inherit state from the parent;
* Unlock both.
* }
*
* my_update_state(@css)
* {
* css_for_each_descendant_pre(@pos, @css) {
* Lock @pos;
* if (@pos == @css)
* Update @css's state;
* else
* Verify @pos is alive and inherit state from its parent;
* Unlock @pos;
* }
* }
*
* As long as the inheriting step, including checking the parent state, is
* enclosed inside @pos locking, double-locking the parent isn't necessary
* while inheriting. The state update to the parent is guaranteed to be
* visible by walking order and, as long as inheriting operations to the
* same @pos are atomic to each other, multiple updates racing each other
* still result in the correct state. It's guaranateed that at least one
* inheritance happens for any css after the latest update to its parent.
*
* If checking parent's state requires locking the parent, each inheriting
* iteration should lock and unlock both @pos->parent and @pos.
*
* Alternatively, a subsystem may choose to use a single global lock to
* synchronize ->css_online() and ->css_offline() against tree-walking
* operations.
*
* It is allowed to temporarily drop RCU read lock during iteration. The
* caller is responsible for ensuring that @pos remains accessible until
* the start of the next iteration by, for example, bumping the css refcnt.
*/
#define css_for_each_descendant_pre(pos, css) \
for ((pos) = css_next_descendant_pre(NULL, (css)); (pos); \
(pos) = css_next_descendant_pre((pos), (css)))
struct cgroup_subsys_state *
css_next_descendant_post(struct cgroup_subsys_state *pos,
struct cgroup_subsys_state *css);
/**
* css_for_each_descendant_post - post-order walk of a css's descendants
* @pos: the css * to use as the loop cursor
* @css: css whose descendants to walk
*
* Similar to css_for_each_descendant_pre() but performs post-order
* traversal instead. @root is included in the iteration and the last
* node to be visited.
*
* If a subsystem synchronizes ->css_online() and the start of iteration, a
* css which finished ->css_online() is guaranteed to be visible in the
* future iterations and will stay visible until the last reference is put.
* A css which hasn't finished ->css_online() or already finished
* ->css_offline() may show up during traversal. It's each subsystem's
* responsibility to synchronize against on/offlining.
*
* Note that the walk visibility guarantee example described in pre-order
* walk doesn't apply the same to post-order walks.
*/
#define css_for_each_descendant_post(pos, css) \
for ((pos) = css_next_descendant_post(NULL, (css)); (pos); \
(pos) = css_next_descendant_post((pos), (css)))
bool css_has_online_children(struct cgroup_subsys_state *css);
/* A css_task_iter should be treated as an opaque object */
struct css_task_iter {
struct cgroup_subsys *ss;
struct list_head *cset_pos;
struct list_head *cset_head;
struct list_head *task_pos;
struct list_head *tasks_head;
struct list_head *mg_tasks_head;
};
void css_task_iter_start(struct cgroup_subsys_state *css,
struct css_task_iter *it);
struct task_struct *css_task_iter_next(struct css_task_iter *it);
void css_task_iter_end(struct css_task_iter *it);
int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgroup,
struct cgroup_subsys *ss);
struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
struct cgroup_subsys *ss);
#else /* !CONFIG_CGROUPS */
struct cgroup_subsys_state;
static inline int cgroup_init_early(void) { return 0; }
static inline int cgroup_init(void) { return 0; }
static inline void cgroup_fork(struct task_struct *p) {}
static inline void cgroup_post_fork(struct task_struct *p) {}
static inline void cgroup_exit(struct task_struct *p) {}
static inline int cgroupstats_build(struct cgroupstats *stats,
struct dentry *dentry)
{
return -EINVAL;
}
static inline void css_put(struct cgroup_subsys_state *css) {}
/* No cgroups - nothing to do */
static inline int cgroup_attach_task_all(struct task_struct *from,
struct task_struct *t)
{
return 0;
}
#endif /* !CONFIG_CGROUPS */
#endif /* _LINUX_CGROUP_H */
