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#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>
#include <linux/percpu-refcount.h>
#ifdef CONFIG_CGROUPS
struct cgroupfs_root;
struct cgroup_subsys;
struct inode;
struct cgroup;
struct css_id;
struct eventfd_ctx;
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, 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 *);
/*
* Define the enumeration of all cgroup subsystems.
*
* We define ids for builtin subsystems and then modular ones.
*/
#define SUBSYS(_x) _x ## _subsys_id,
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,
#define IS_SUBSYS_ENABLED(option) IS_MODULE(option)
#include <linux/cgroup_subsys.h>
#undef IS_SUBSYS_ENABLED
CGROUP_SUBSYS_COUNT,
};
#undef SUBSYS
/* Per-subsystem/per-cgroup state maintained by the system. */
struct cgroup_subsys_state {
/* the cgroup that this css is attached to */
struct cgroup *cgroup;
/* the cgroup subsystem that this css is attached to */
struct cgroup_subsys *ss;
/* reference count - access via css_[try]get() and css_put() */
struct percpu_ref refcnt;
/* the parent css */
struct cgroup_subsys_state *parent;
unsigned long flags;
/* ID for this css, if possible */
struct css_id __rcu *id;
/* percpu_ref killing and RCU release */
struct rcu_head rcu_head;
struct work_struct destroy_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() */
};
/**
* 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)
{
/* We don't need to reference count the root state */
if (!(css->flags & CSS_ROOT))
percpu_ref_get(&css->refcnt);
}
/**
* css_tryget - try to obtain a reference on the specified css
* @css: target css
*
* Obtain a reference on @css if it's alive. 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_ROOT)
return true;
return percpu_ref_tryget(&css->refcnt);
}
/**
* css_put - put a css reference
* @css: target css
*
* Put a reference obtained via css_get() and css_tryget().
*/
static inline void css_put(struct cgroup_subsys_state *css)
{
if (!(css->flags & CSS_ROOT))
percpu_ref_put(&css->refcnt);
}
/* bits in struct cgroup flags field */
enum {
/* Control Group is dead */
CGRP_DEAD,
/*
* 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 */
/*
* idr allocated in-hierarchy ID.
*
* The ID of the root cgroup is always 0, and a new cgroup
* will be assigned with a smallest available ID.
*
* Allocating/Removing ID must be protected by cgroup_mutex.
*/
int id;
/* the number of attached css's */
int nr_css;
/*
* 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 */
/*
* Monotonically increasing unique serial number which defines a
* uniform order among all cgroups. It's guaranteed that all
* ->children lists are in the ascending order of ->serial_nr.
* It's used to allow interrupting and resuming iterations.
*/
u64 serial_nr;
/*
* 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 __rcu *subsys[CGROUP_SUBSYS_COUNT];
struct cgroupfs_root *root;
/*
* List of cgrp_cset_links pointing at css_sets with tasks in this
* cgroup. Protected by css_set_lock.
*/
struct list_head cset_links;
/*
* 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;
/* dummy css with NULL ->ss, points back to this cgroup */
struct cgroup_subsys_state dummy_css;
/* For css percpu_ref killing and RCU-protected deletion */
struct rcu_head rcu_head;
struct work_struct destroy_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.
*
* - rename(2) is disallowed.
*
* - "tasks" is removed. Everything should be at process
* granularity. Use "cgroup.procs" instead.
*
* - "release_agent" and "notify_on_release" are removed.
* Replacement notification mechanism will be implemented.
*
* - 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.
*/
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 */
/* mount options live below bit 16 */
CGRP_ROOT_OPTION_MASK = (1 << 16) - 1,
CGRP_ROOT_SUBSYS_BOUND = (1 << 16), /* subsystems finished binding */
};
/*
* 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 attached to this hierarchy */
unsigned long subsys_mask;
/* Unique id for this hierarchy. */
int hierarchy_id;
/* 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;
/* Hierarchy-specific flags */
unsigned long flags;
/* IDs for cgroups in this hierarchy */
struct idr cgroup_idr;
/* 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 cgrp_cset_links pointing at cgroups referenced from this
* css_set. Protected by css_set_lock.
*/
struct list_head cgrp_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 */
enum {
CFTYPE_ONLY_ON_ROOT = (1 << 0), /* only create on root cgrp */
CFTYPE_NOT_ON_ROOT = (1 << 1), /* don't create on root cgrp */
CFTYPE_INSANE = (1 << 2), /* don't create if sane_behavior */
CFTYPE_NO_PREFIX = (1 << 3), /* (DON'T USE FOR NEW FILES) no subsys prefix */
};
#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;
/*
* The subsys this file belongs to. Initialized automatically
* during registration. NULL for cgroup core files.
*/
struct cgroup_subsys *ss;
int (*open)(struct inode *inode, struct file *file);
ssize_t (*read)(struct cgroup_subsys_state *css, 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_subsys_state *css, struct cftype *cft);
/*
* read_s64() is a signed version of read_u64()
*/
s64 (*read_s64)(struct cgroup_subsys_state *css, 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_subsys_state *css, 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_subsys_state *css,
struct cftype *cft, struct seq_file *m);
ssize_t (*write)(struct cgroup_subsys_state *css, 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_subsys_state *css, struct cftype *cft,
u64 val);
/*
* write_s64() is a signed version of write_u64()
*/
int (*write_s64)(struct cgroup_subsys_state *css, 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_subsys_state *css, 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_subsys_state *css, 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_subsys_state *css,
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_subsys_state *css,
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;
};
/*
* 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 cftype *cfts);
bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor);
int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen);
int task_cgroup_path(struct task_struct *task, char *buf, size_t 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_subsys_state *cgroup_taskset_cur_css(struct cgroup_taskset *tset,
int subsys_id);
int cgroup_taskset_size(struct cgroup_taskset *tset);
/**
* cgroup_taskset_for_each - iterate cgroup_taskset
* @task: the loop cursor
* @skip_css: skip if task's css matches this, %NULL to iterate through all
* @tset: taskset to iterate
*/
#define cgroup_taskset_for_each(task, skip_css, tset) \
for ((task) = cgroup_taskset_first((tset)); (task); \
(task) = cgroup_taskset_next((tset))) \
if (!(skip_css) || \
cgroup_taskset_cur_css((tset), \
(skip_css)->ss->subsys_id) != (skip_css))
/*
* Control Group subsystem type.
* See Documentation/cgroups/cgroups.txt for details
*/
struct cgroup_subsys {
struct cgroup_subsys_state *(*css_alloc)(struct cgroup_subsys_state *parent_css);
int (*css_online)(struct cgroup_subsys_state *css);
void (*css_offline)(struct cgroup_subsys_state *css);
void (*css_free)(struct cgroup_subsys_state *css);
int (*can_attach)(struct cgroup_subsys_state *css,
struct cgroup_taskset *tset);
void (*cancel_attach)(struct cgroup_subsys_state *css,
struct cgroup_taskset *tset);
void (*attach)(struct cgroup_subsys_state *css,
struct cgroup_taskset *tset);
void (*fork)(struct task_struct *task);
void (*exit)(struct cgroup_subsys_state *css,
struct cgroup_subsys_state *old_css,
struct task_struct *task);
void (*bind)(struct cgroup_subsys_state *root_css);
int subsys_id;
int disabled;
int early_init;
/*
* 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;
/* 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 IS_SUBSYS_ENABLED
#undef SUBSYS
/**
* css_parent - find the parent css
* @css: the target cgroup_subsys_state
*
* Return the parent css of @css. This function is guaranteed to return
* non-NULL parent as long as @css isn't the root.
*/
static inline
struct cgroup_subsys_state *css_parent(struct cgroup_subsys_state *css)
{
return css->parent;
}
/**
* 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_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);
}
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(). A child
* css 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 css which finished ->css_online() is
* guaranteed to be visible in the future iterations.
*
* 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(). A
* descendant css 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 css 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(@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. Note that the walk visibility guarantee 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)))
/* A css_task_iter should be treated as an opaque object */
struct css_task_iter {
struct cgroup_subsys_state *origin_css;
struct list_head *cset_link;
struct list_head *task;
};
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 css_scan_tasks(struct cgroup_subsys_state *css,
bool (*test)(struct task_struct *, void *),
void (*process)(struct task_struct *, void *),
void *data, struct ptr_heap *heap);
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 *css_from_dir(struct dentry *dentry,
struct cgroup_subsys *ss);
#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 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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