Edit File: 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 */