blob: 900af5964f5543f6dd1b5308419e93c70cb0ca07 [file] [log] [blame]
* 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/rcupdate.h>
#include <linux/rculist.h>
#include <linux/cgroupstats.h>
#include <linux/prio_heap.h>
#include <linux/rwsem.h>
#include <linux/idr.h>
#include <linux/workqueue.h>
#include <linux/xattr.h>
struct cgroupfs_root;
struct cgroup_subsys;
struct inode;
struct cgroup;
struct css_id;
extern int cgroup_init_early(void);
extern int cgroup_init(void);
extern void cgroup_lock(void);
extern int cgroup_lock_is_held(void);
extern bool cgroup_lock_live_group(struct cgroup *cgrp);
extern void cgroup_unlock(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, int run_callbacks);
extern int cgroupstats_build(struct cgroupstats *stats,
struct dentry *dentry);
extern int cgroup_load_subsys(struct cgroup_subsys *ss);
extern void cgroup_unload_subsys(struct cgroup_subsys *ss);
extern const struct file_operations proc_cgroup_operations;
/* Define the enumeration of all builtin cgroup subsystems */
#define SUBSYS(_x) _x ## _subsys_id,
#define IS_SUBSYS_ENABLED(option) IS_ENABLED(option)
enum cgroup_subsys_id {
#include <linux/cgroup_subsys.h>
#undef SUBSYS
/* Per-subsystem/per-cgroup state maintained by the system. */
struct cgroup_subsys_state {
* The cgroup that this subsystem is attached to. Useful
* for subsystems that want to know about the cgroup
* hierarchy structure
struct cgroup *cgroup;
* State maintained by the cgroup system to allow subsystems
* to be "busy". Should be accessed via css_get(),
* css_tryget() and css_put().
atomic_t refcnt;
unsigned long flags;
/* ID for this css, if possible */
struct css_id __rcu *id;
/* Used to put @cgroup->dentry on the last css_put() */
struct work_struct dput_work;
/* bits in struct cgroup_subsys_state flags field */
enum {
CSS_ROOT = (1 << 0), /* this CSS is the root of the subsystem */
CSS_ONLINE = (1 << 1), /* between ->css_online() and ->css_offline() */
/* Caller must verify that the css is not for root cgroup */
static inline void __css_get(struct cgroup_subsys_state *css, int count)
atomic_add(count, &css->refcnt);
* Call css_get() to hold a reference on the css; it can be used
* for a reference obtained via:
* - an existing ref-counted reference to the css
* - task->cgroups for a locked task
static inline void css_get(struct cgroup_subsys_state *css)
/* We don't need to reference count the root state */
if (!(css->flags & CSS_ROOT))
__css_get(css, 1);
* Call css_tryget() to take a reference on a css if your existing
* (known-valid) reference isn't already ref-counted. Returns false if
* the css has been destroyed.
extern bool __css_tryget(struct cgroup_subsys_state *css);
static inline bool css_tryget(struct cgroup_subsys_state *css)
if (css->flags & CSS_ROOT)
return true;
return __css_tryget(css);
* css_put() should be called to release a reference taken by
* css_get() or css_tryget()
extern void __css_put(struct cgroup_subsys_state *css);
static inline void css_put(struct cgroup_subsys_state *css)
if (!(css->flags & CSS_ROOT))
/* bits in struct cgroup flags field */
enum {
/* Control Group is dead */
* Control Group has previously had a child cgroup or a task,
* but no longer (only if CGRP_NOTIFY_ON_RELEASE is set)
/* Control Group requires release notifications to userspace */
* Clone the parent's configuration when creating a new child
* cpuset cgroup. For historical reasons, this option can be
* specified at mount time and thus is implemented here.
struct cgroup {
unsigned long flags; /* "unsigned long" so bitops work */
* count users of this cgroup. >0 means busy, but doesn't
* necessarily indicate the number of tasks in the cgroup
atomic_t count;
int id; /* ida allocated in-hierarchy ID */
* We link our 'sibling' struct into our parent's 'children'.
* Our children link their 'sibling' into our 'children'.
struct list_head sibling; /* my parent's children */
struct list_head children; /* my children */
struct list_head files; /* my files */
struct cgroup *parent; /* my parent */
struct dentry *dentry; /* cgroup fs entry, RCU protected */
/* Private pointers for each registered subsystem */
struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
struct cgroupfs_root *root;
struct cgroup *top_cgroup;
* List of cg_cgroup_links pointing at css_sets with
* tasks in this cgroup. Protected by css_set_lock
struct list_head css_sets;
struct list_head allcg_node; /* cgroupfs_root->allcg_list */
struct list_head cft_q_node; /* used during cftype add/rm */
* 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;
* list of pidlists, up to two for each namespace (one for procs, one
* for tasks); created on demand.
struct list_head pidlists;
struct mutex pidlist_mutex;
/* For RCU-protected deletion */
struct rcu_head rcu_head;
struct work_struct free_work;
/* List of events which userspace want to receive */
struct list_head event_list;
spinlock_t event_list_lock;
/* directory xattrs */
struct simple_xattrs xattrs;
* A css_set is a structure holding pointers to a set of
* cgroup_subsys_state objects. This saves space in the task struct
* object and speeds up fork()/exit(), since a single inc/dec and a
* list_add()/del() can bump the reference count on the entire cgroup
* set for a task.
struct css_set {
/* Reference count */
atomic_t refcount;
* List running through all cgroup groups in the same hash
* slot. Protected by css_set_lock
struct hlist_node hlist;
* List running through all tasks using this cgroup
* group. Protected by css_set_lock
struct list_head tasks;
* List of cg_cgroup_link objects on link chains from
* cgroups referenced from this css_set. Protected by
* css_set_lock
struct list_head cg_links;
* Set of subsystem states, one for each subsystem. This array
* is immutable after creation apart from the init_css_set
* during subsystem registration (at boot time) and modular subsystem
* loading/unloading.
struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
/* For RCU-protected deletion */
struct rcu_head rcu_head;
* cgroup_map_cb is an abstract callback API for reporting map-valued
* control files
struct cgroup_map_cb {
int (*fill)(struct cgroup_map_cb *cb, const char *key, u64 value);
void *state;
* struct cftype: handler definitions for cgroup control files
* When reading/writing to a file:
* - the cgroup to use is file->f_dentry->d_parent->d_fsdata
* - the 'cftype' of the file is file->f_dentry->d_fsdata
/* cftype->flags */
#define CFTYPE_ONLY_ON_ROOT (1U << 0) /* only create on root cg */
#define CFTYPE_NOT_ON_ROOT (1U << 1) /* don't create on root cg */
#define MAX_CFTYPE_NAME 64
struct cftype {
* By convention, the name should begin with the name of the
* subsystem, followed by a period. Zero length string indicates
* end of cftype array.
char name[MAX_CFTYPE_NAME];
int private;
* If not 0, file mode is set to this value, otherwise it will
* be figured out automatically
umode_t mode;
* If non-zero, defines the maximum length of string that can
* be passed to write_string; defaults to 64
size_t max_write_len;
/* CFTYPE_* flags */
unsigned int flags;
/* file xattrs */
struct simple_xattrs xattrs;
int (*open)(struct inode *inode, struct file *file);
ssize_t (*read)(struct cgroup *cgrp, struct cftype *cft,
struct file *file,
char __user *buf, size_t nbytes, loff_t *ppos);
* read_u64() is a shortcut for the common case of returning a
* single integer. Use it in place of read()
u64 (*read_u64)(struct cgroup *cgrp, struct cftype *cft);
* read_s64() is a signed version of read_u64()
s64 (*read_s64)(struct cgroup *cgrp, struct cftype *cft);
* read_map() is used for defining a map of key/value
* pairs. It should call cb->fill(cb, key, value) for each
* entry. The key/value pairs (and their ordering) should not
* change between reboots.
int (*read_map)(struct cgroup *cont, struct cftype *cft,
struct cgroup_map_cb *cb);
* read_seq_string() is used for outputting a simple sequence
* using seqfile.
int (*read_seq_string)(struct cgroup *cont, struct cftype *cft,
struct seq_file *m);
ssize_t (*write)(struct cgroup *cgrp, struct cftype *cft,
struct file *file,
const char __user *buf, size_t nbytes, loff_t *ppos);
* write_u64() is a shortcut for the common case of accepting
* a single integer (as parsed by simple_strtoull) from
* userspace. Use in place of write(); return 0 or error.
int (*write_u64)(struct cgroup *cgrp, struct cftype *cft, u64 val);
* write_s64() is a signed version of write_u64()
int (*write_s64)(struct cgroup *cgrp, struct cftype *cft, s64 val);
* write_string() is passed a nul-terminated kernelspace
* buffer of maximum length determined by max_write_len.
* Returns 0 or -ve error code.
int (*write_string)(struct cgroup *cgrp, struct cftype *cft,
const char *buffer);
* trigger() callback can be used to get some kick from the
* userspace, when the actual string written is not important
* at all. The private field can be used to determine the
* kick type for multiplexing.
int (*trigger)(struct cgroup *cgrp, unsigned int event);
int (*release)(struct inode *inode, struct file *file);
* register_event() callback will be used to add new userspace
* waiter for changes related to the cftype. Implement it if
* you want to provide this functionality. Use eventfd_signal()
* on eventfd to send notification to userspace.
int (*register_event)(struct cgroup *cgrp, struct cftype *cft,
struct eventfd_ctx *eventfd, const char *args);
* unregister_event() callback will be called when userspace
* closes the eventfd or on cgroup removing.
* This callback must be implemented, if you want provide
* notification functionality.
void (*unregister_event)(struct cgroup *cgrp, struct cftype *cft,
struct eventfd_ctx *eventfd);
* cftype_sets describe cftypes belonging to a subsystem and are chained at
* cgroup_subsys->cftsets. Each cftset points to an array of cftypes
* terminated by zero length name.
struct cftype_set {
struct list_head node; /* chained at subsys->cftsets */
struct cftype *cfts;
struct cgroup_scanner {
struct cgroup *cg;
int (*test_task)(struct task_struct *p, struct cgroup_scanner *scan);
void (*process_task)(struct task_struct *p,
struct cgroup_scanner *scan);
struct ptr_heap *heap;
void *data;
int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
int cgroup_is_removed(const struct cgroup *cgrp);
int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen);
int cgroup_task_count(const struct cgroup *cgrp);
/* Return true if cgrp is a descendant of the task's cgroup */
int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task);
* Control Group taskset, used to pass around set of tasks to cgroup_subsys
* methods.
struct cgroup_taskset;
struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset);
struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset);
struct cgroup *cgroup_taskset_cur_cgroup(struct cgroup_taskset *tset);
int cgroup_taskset_size(struct cgroup_taskset *tset);
* cgroup_taskset_for_each - iterate cgroup_taskset
* @task: the loop cursor
* @skip_cgrp: skip if task's cgroup matches this, %NULL to iterate through all
* @tset: taskset to iterate
#define cgroup_taskset_for_each(task, skip_cgrp, tset) \
for ((task) = cgroup_taskset_first((tset)); (task); \
(task) = cgroup_taskset_next((tset))) \
if (!(skip_cgrp) || \
cgroup_taskset_cur_cgroup((tset)) != (skip_cgrp))
* Control Group subsystem type.
* See Documentation/cgroups/cgroups.txt for details
struct cgroup_subsys {
struct cgroup_subsys_state *(*css_alloc)(struct cgroup *cgrp);
int (*css_online)(struct cgroup *cgrp);
void (*css_offline)(struct cgroup *cgrp);
void (*css_free)(struct cgroup *cgrp);
int (*can_attach)(struct cgroup *cgrp, struct cgroup_taskset *tset);
void (*cancel_attach)(struct cgroup *cgrp, struct cgroup_taskset *tset);
void (*attach)(struct cgroup *cgrp, struct cgroup_taskset *tset);
void (*fork)(struct task_struct *task);
void (*exit)(struct cgroup *cgrp, struct cgroup *old_cgrp,
struct task_struct *task);
void (*bind)(struct cgroup *root);
int subsys_id;
int active;
int disabled;
int early_init;
* True if this subsys uses ID. ID is not available before cgroup_init()
* (not available in early_init time.)
bool use_id;
* If %false, this subsystem is properly hierarchical -
* configuration, resource accounting and restriction on a parent
* cgroup cover those of its children. If %true, hierarchy support
* is broken in some ways - some subsystems ignore hierarchy
* completely while others are only implemented half-way.
* It's now disallowed to create nested cgroups if the subsystem is
* broken and cgroup core will emit a warning message on such
* cases. Eventually, all subsystems will be made properly
* hierarchical and this will go away.
bool broken_hierarchy;
bool warned_broken_hierarchy;
const char *name;
* Link to parent, and list entry in parent's children.
* Protected by cgroup_lock()
struct cgroupfs_root *root;
struct list_head sibling;
/* used when use_id == true */
struct idr idr;
spinlock_t id_lock;
/* list of cftype_sets */
struct list_head cftsets;
/* base cftypes, automatically [de]registered with subsys itself */
struct cftype *base_cftypes;
struct cftype_set base_cftset;
/* should be defined only by modular subsystems */
struct module *module;
#define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys;
#define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
#include <linux/cgroup_subsys.h>
#undef SUBSYS
static inline struct cgroup_subsys_state *cgroup_subsys_state(
struct cgroup *cgrp, int subsys_id)
return cgrp->subsys[subsys_id];
* function to get the cgroup_subsys_state which allows for extra
* rcu_dereference_check() conditions, such as locks used during the
* cgroup_subsys::attach() methods.
#define task_subsys_state_check(task, subsys_id, __c) \
rcu_dereference_check(task->cgroups->subsys[subsys_id], \
lockdep_is_held(&task->alloc_lock) || \
cgroup_lock_is_held() || (__c))
static inline struct cgroup_subsys_state *
task_subsys_state(struct task_struct *task, int subsys_id)
return task_subsys_state_check(task, subsys_id, false);
static inline struct cgroup* task_cgroup(struct task_struct *task,
int subsys_id)
return task_subsys_state(task, subsys_id)->cgroup;
* cgroup_for_each_child - iterate through children of a cgroup
* @pos: the cgroup * to use as the loop cursor
* @cgroup: cgroup whose children to walk
* Walk @cgroup's children. Must be called under rcu_read_lock(). A child
* cgroup which hasn't finished ->css_online() or already has finished
* ->css_offline() may show up during traversal and it's each subsystem's
* responsibility to verify that each @pos is alive.
* If a subsystem synchronizes against the parent in its ->css_online() and
* before starting iterating, a cgroup which finished ->css_online() is
* guaranteed to be visible in the future iterations.
#define cgroup_for_each_child(pos, cgroup) \
list_for_each_entry_rcu(pos, &(cgroup)->children, sibling)
struct cgroup *cgroup_next_descendant_pre(struct cgroup *pos,
struct cgroup *cgroup);
struct cgroup *cgroup_rightmost_descendant(struct cgroup *pos);
* cgroup_for_each_descendant_pre - pre-order walk of a cgroup's descendants
* @pos: the cgroup * to use as the loop cursor
* @cgroup: cgroup whose descendants to walk
* Walk @cgroup's descendants. Must be called under rcu_read_lock(). A
* descendant cgroup which hasn't finished ->css_online() or already has
* finished ->css_offline() may show up during traversal and it's each
* subsystem's responsibility to verify that each @pos is alive.
* If a subsystem synchronizes against the parent in its ->css_online() and
* before starting iterating, and synchronizes against @pos on each
* iteration, any descendant cgroup which finished ->css_offline() is
* guaranteed to be visible in the future iterations.
* In other words, the following guarantees that a descendant can't escape
* state updates of its ancestors.
* my_online(@cgrp)
* {
* Lock @cgrp->parent and @cgrp;
* Inherit state from @cgrp->parent;
* Unlock both.
* }
* my_update_state(@cgrp)
* {
* Lock @cgrp;
* Update @cgrp's state;
* Unlock @cgrp;
* cgroup_for_each_descendant_pre(@pos, @cgrp) {
* Lock @pos;
* Verify @pos is alive and inherit state from @pos->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 cgroup 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.
#define cgroup_for_each_descendant_pre(pos, cgroup) \
for (pos = cgroup_next_descendant_pre(NULL, (cgroup)); (pos); \
pos = cgroup_next_descendant_pre((pos), (cgroup)))
struct cgroup *cgroup_next_descendant_post(struct cgroup *pos,
struct cgroup *cgroup);
* cgroup_for_each_descendant_post - post-order walk of a cgroup's descendants
* @pos: the cgroup * to use as the loop cursor
* @cgroup: cgroup whose descendants to walk
* Similar to cgroup_for_each_descendant_pre() but performs post-order
* traversal instead. Note that the walk visibility guarantee described in
* pre-order walk doesn't apply the same to post-order walks.
#define cgroup_for_each_descendant_post(pos, cgroup) \
for (pos = cgroup_next_descendant_post(NULL, (cgroup)); (pos); \
pos = cgroup_next_descendant_post((pos), (cgroup)))
/* A cgroup_iter should be treated as an opaque object */
struct cgroup_iter {
struct list_head *cg_link;
struct list_head *task;
* To iterate across the tasks in a cgroup:
* 1) call cgroup_iter_start to initialize an iterator
* 2) call cgroup_iter_next() to retrieve member tasks until it
* returns NULL or until you want to end the iteration
* 3) call cgroup_iter_end() to destroy the iterator.
* Or, call cgroup_scan_tasks() to iterate through every task in a
* cgroup - cgroup_scan_tasks() holds the css_set_lock when calling
* the test_task() callback, but not while calling the process_task()
* callback.
void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it);
struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
struct cgroup_iter *it);
void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it);
int cgroup_scan_tasks(struct cgroup_scanner *scan);
int cgroup_attach_task(struct cgroup *, struct task_struct *);
int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
* CSS ID is ID for cgroup_subsys_state structs under subsys. This only works
* if cgroup_subsys.use_id == true. It can be used for looking up and scanning.
* CSS ID is assigned at cgroup allocation (create) automatically
* and removed when subsys calls free_css_id() function. This is because
* the lifetime of cgroup_subsys_state is subsys's matter.
* Looking up and scanning function should be called under rcu_read_lock().
* Taking cgroup_mutex is not necessary for following calls.
* But the css returned by this routine can be "not populated yet" or "being
* destroyed". The caller should check css and cgroup's status.
* Typically Called at ->destroy(), or somewhere the subsys frees
* cgroup_subsys_state.
void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css);
/* Find a cgroup_subsys_state which has given ID */
struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id);
* Get a cgroup whose id is greater than or equal to id under tree of root.
* Returning a cgroup_subsys_state or NULL.
struct cgroup_subsys_state *css_get_next(struct cgroup_subsys *ss, int id,
struct cgroup_subsys_state *root, int *foundid);
/* Returns true if root is ancestor of cg */
bool css_is_ancestor(struct cgroup_subsys_state *cg,
const struct cgroup_subsys_state *root);
/* Get id and depth of css */
unsigned short css_id(struct cgroup_subsys_state *css);
unsigned short css_depth(struct cgroup_subsys_state *css);
struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id);
#else /* !CONFIG_CGROUPS */
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, int callbacks) {}
static inline void cgroup_lock(void) {}
static inline void cgroup_unlock(void) {}
static inline int cgroupstats_build(struct cgroupstats *stats,
struct dentry *dentry)
return -EINVAL;
/* 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 */