Current File : //lib/modules/3.10.0-1160.83.1.el7.centos.plus.x86_64/build/include/linux/cgroup.h
#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/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>
#include <linux/fs.h>
#ifdef CONFIG_CGROUP_PIDS
void cgroup_pids_release(struct task_struct *task);
#else
static inline void cgroup_pids_release(struct task_struct *task) {}
#endif
#ifdef CONFIG_CGROUPS
struct cgroupfs_root;
struct cgroup_subsys;
struct inode;
struct cgroup;
struct css_id;
struct eventfd_ctx;
/*
* Define the enumeration of all cgroup subsystems.
*
* We define ids for builtin subsystems and then modular ones.
*
* NOTE: Theres some real hackery going on here. Initially in RHEL7, the
* netprio cgroup was built as a module, but in 7.3 we had need to make it
* builtin. The cgroup design caused this move to create LOTS of false positive
* ABI breaks. AS such, we use this ENABLE_NETPRIO_NOW macro to direct where in
* the cgroup_subsys_id ennumeration the netprio subsys id is defined, thereby
* avoiding those false positives. Please be very careful making further
* modifications to this ennumeration
*/
#define SUBSYS(_x) _x ## _subsys_id,
#define SUBSYS_TAG(_t) CGROUP_ ## _t, \
__unused_tag_ ## _t = CGROUP_ ## _t - 1,
enum cgroup_subsys_id {
#define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
#include <linux/cgroup_subsys.h>
#undef IS_SUBSYS_ENABLED
CGROUP_BUILTIN_SUBSYS_COUNT,
__CGROUP_SUBSYS_TEMP_PLACEHOLDER = CGROUP_BUILTIN_SUBSYS_COUNT - 1,
#undef SUBSYS_TAG
#define IS_SUBSYS_ENABLED(option) IS_MODULE(option)
#define ENABLE_NETPRIO_NOW
#include <linux/cgroup_subsys.h>
#undef ENABLE_NETPRIO_NOW
#undef IS_SUBSYS_ENABLED
CGROUP_SUBSYS_COUNT,
};
#undef SUBSYS
#define CGROUP_CANFORK_COUNT (CGROUP_CANFORK_END - CGROUP_CANFORK_START)
extern int cgroup_init_early(void);
extern int cgroup_init(void);
extern void cgroup_fork(struct task_struct *p);
extern int cgroup_can_fork(struct task_struct *p,
void *ss_priv[CGROUP_CANFORK_COUNT]);
extern void cgroup_cancel_fork(struct task_struct *p,
void *ss_priv[CGROUP_CANFORK_COUNT]);
extern void cgroup_post_fork(struct task_struct *p,
void *old_ss_priv[CGROUP_CANFORK_COUNT]);
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 int proc_cgroup_show(struct seq_file *, void *);
/* 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))
__css_put(css);
}
/* bits in struct cgroup flags field */
enum {
/* Control Group is dead */
CGRP_REMOVED,
/*
* Control Group has previously had a child cgroup or a task,
* but no longer (only if CGRP_NOTIFY_ON_RELEASE is set)
*/
CGRP_RELEASABLE,
/* Control Group requires release notifications to userspace */
CGRP_NOTIFY_ON_RELEASE,
/*
* 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.
*/
CGRP_CPUSET_CLONE_CHILDREN,
/* see the comment above CGRP_ROOT_SANE_BEHAVIOR for details */
CGRP_SANE_BEHAVIOR,
};
struct cgroup_name {
struct rcu_head rcu_head;
char name[];
};
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 */
/*
* This is a copy of dentry->d_name, and it's needed because
* we can't use dentry->d_name in cgroup_path().
*
* You must acquire rcu_read_lock() to access cgrp->name, and
* the only place that can change it is rename(), which is
* protected by parent dir's i_mutex.
*
* Normally you should use cgroup_name() wrapper rather than
* access it directly.
*/
struct cgroup_name __rcu *name;
/* Private pointers for each registered subsystem */
struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
struct cgroupfs_root *root;
/*
* 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;
};
#define MAX_CGROUP_ROOT_NAMELEN 64
/* cgroupfs_root->flags */
enum {
/*
* Unfortunately, cgroup core and various controllers are riddled
* with idiosyncrasies and pointless options. The following flag,
* when set, will force sane behavior - some options are forced on,
* others are disallowed, and some controllers will change their
* hierarchical or other behaviors.
*
* The set of behaviors affected by this flag are still being
* determined and developed and the mount option for this flag is
* prefixed with __DEVEL__. The prefix will be dropped once we
* reach the point where all behaviors are compatible with the
* planned unified hierarchy, which will automatically turn on this
* flag.
*
* The followings are the behaviors currently affected this flag.
*
* - Mount options "noprefix" and "clone_children" are disallowed.
* Also, cgroupfs file cgroup.clone_children is not created.
*
* - When mounting an existing superblock, mount options should
* match.
*
* - Remount is disallowed.
*
* - 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.
*
* The followings are planned changes.
*
* - release_agent will be disallowed once replacement notification
* mechanism is implemented.
*/
CGRP_ROOT_SANE_BEHAVIOR = (1 << 0),
CGRP_ROOT_NOPREFIX = (1 << 1), /* mounted subsystems have no named prefix */
CGRP_ROOT_XATTR = (1 << 2), /* supports extended attributes */
/*
* Enable cpuset controller in v1 cgroup to use v2 behavior.
*/
CGRP_ROOT_CPUSET_V2_MODE = (1 << 3),
};
/*
* A cgroupfs_root represents the root of a cgroup hierarchy, and may be
* associated with a superblock to form an active hierarchy. This is
* internal to cgroup core. Don't access directly from controllers.
*/
struct cgroupfs_root {
struct super_block *sb;
/*
* The bitmask of subsystems intended to be attached to this
* hierarchy
*/
unsigned long subsys_mask;
/* Unique id for this hierarchy. */
int hierarchy_id;
/* The bitmask of subsystems currently attached to this hierarchy */
unsigned long actual_subsys_mask;
/* A list running through the attached subsystems */
struct list_head subsys_list;
/* The root cgroup for this hierarchy */
struct cgroup top_cgroup;
/* Tracks how many cgroups are currently defined in hierarchy.*/
int number_of_cgroups;
/* A list running through the active hierarchies */
struct list_head root_list;
/* All cgroups on this root, cgroup_mutex protected */
struct list_head allcg_list;
/* Hierarchy-specific flags */
unsigned long flags;
/* IDs for cgroups in this hierarchy */
struct ida cgroup_ida;
/* The path to use for release notifications. */
char release_agent_path[PATH_MAX];
/* The name for this hierarchy - may be empty */
char name[MAX_CGROUP_ROOT_NAMELEN];
};
/*
* 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 CFTYPE_INSANE (1U << 2) /* don't create if sane_behavior */
#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;
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;
};
/*
* See the comment above CGRP_ROOT_SANE_BEHAVIOR for details. This
* function can be called as long as @cgrp is accessible.
*/
static inline bool cgroup_sane_behavior(const struct cgroup *cgrp)
{
return cgrp->root->flags & CGRP_ROOT_SANE_BEHAVIOR;
}
/* Caller should hold rcu_read_lock() */
static inline const char *cgroup_name(const struct cgroup *cgrp)
{
return rcu_dereference(cgrp->name)->name;
}
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);
bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor);
int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen);
int cgroup_task_count(const struct cgroup *cgrp);
/*
* 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);
RH_KABI_REPLACE(void (*fork)(struct task_struct *task),
void (*fork)(struct task_struct *task, void *priv))
void (*exit)(struct cgroup *cgrp, struct cgroup *old_cgrp,
struct task_struct *task);
void (*bind)(struct cgroup *root);
int subsys_id;
int disabled;
int early_init;
/*
* True if this subsys uses ID. ID is not available before cgroup_init()
* (not available in early_init time.)
*/
RH_KABI_DEPRECATE(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;
#define MAX_CGROUP_TYPE_NAMELEN 32
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 */
RH_KABI_DEPRECATE(struct idr, idr)
RH_KABI_DEPRECATE(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;
RH_KABI_EXTEND(int (*can_fork)(struct task_struct *task, void **priv_p))
RH_KABI_EXTEND(void (*cancel_fork)(struct task_struct *task, void *priv))
};
#define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys;
#define ENABLE_NETPRIO_NOW
#define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
#include <linux/cgroup_subsys.h>
#undef ENABLE_NETPRIO_NOW
#undef IS_SUBSYS_ENABLED
#undef SUBSYS
static inline struct cgroup_subsys_state *cgroup_subsys_state(
struct cgroup *cgrp, int subsys_id)
{
return cgrp->subsys[subsys_id];
}
/**
* 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;
#define task_css_set_check(task, __c) \
rcu_dereference_check((task)->cgroups, \
lockdep_is_held(&(task)->alloc_lock) || \
lockdep_is_held(&cgroup_mutex) || (__c))
#else
#define task_css_set_check(task, __c) \
rcu_dereference((task)->cgroups)
#endif
/**
* task_subsys_state_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_subsys_state_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_subsys_state - obtain css for (task, subsys)
* @task: the target task
* @subsys_id: the target subsystem ID
*
* See task_subsys_state_check().
*/
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;
}
/**
* task_get_css - find and get the css for (task, subsys)
* @task: the target task
* @subsys_id: the target subsystem ID
*
* Find the css for the (@task, @subsys_id) combination, increment a
* reference on and return it. This function is guaranteed to return a
* valid css.
*/
static inline struct cgroup_subsys_state *
task_get_css(struct task_struct *task, int subsys_id)
{
struct cgroup_subsys_state *css;
rcu_read_lock();
while (true) {
css = task_subsys_state(task, subsys_id);
if (likely(css_tryget(css)))
break;
cpu_relax();
}
rcu_read_unlock();
return css;
}
/**
* 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_online() 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_all(struct task_struct *from, struct task_struct *);
int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id);
#else /* !CONFIG_CGROUPS */
#define CGROUP_CANFORK_COUNT 0
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 int cgroup_can_fork(struct task_struct *p,
void *ss_priv[CGROUP_CANFORK_COUNT])
{ return 0; }
static inline void cgroup_cancel_fork(struct task_struct *p,
void *ss_priv[CGROUP_CANFORK_COUNT]) {}
static inline void cgroup_post_fork(struct task_struct *p,
void *ss_priv[CGROUP_CANFORK_COUNT]) {}
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 */
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