diff options
| -rw-r--r-- | include/linux/cgroup.h | 552 |
1 files changed, 271 insertions, 281 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 96a2ecd5aa69..82319fb31cfe 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -22,16 +22,189 @@ #ifdef CONFIG_CGROUPS -extern int cgroup_init_early(void); -extern int cgroup_init(void); -extern void cgroup_fork(struct task_struct *p); -extern void cgroup_post_fork(struct task_struct *p); -extern void cgroup_exit(struct task_struct *p); -extern int cgroupstats_build(struct cgroupstats *stats, - struct dentry *dentry); +/* a css_task_iter should be treated as an opaque object */ +struct css_task_iter { + struct cgroup_subsys *ss; + + struct list_head *cset_pos; + struct list_head *cset_head; + + struct list_head *task_pos; + struct list_head *tasks_head; + struct list_head *mg_tasks_head; +}; + +extern struct cgroup_root cgrp_dfl_root; +extern struct css_set init_css_set; + +#define SUBSYS(_x) extern struct cgroup_subsys _x ## _cgrp_subsys; +#include <linux/cgroup_subsys.h> +#undef SUBSYS + +bool css_has_online_children(struct cgroup_subsys_state *css); +struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss); +struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgroup, + struct cgroup_subsys *ss); +struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry, + struct cgroup_subsys *ss); + +bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor); +int cgroup_attach_task_all(struct task_struct *from, struct task_struct *); +int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from); + +int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts); +int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts); +int cgroup_rm_cftypes(struct cftype *cfts); + +char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen); +int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry); +int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns, + struct pid *pid, struct task_struct *tsk); + +void cgroup_fork(struct task_struct *p); +void cgroup_post_fork(struct task_struct *p); +void cgroup_exit(struct task_struct *p); + +int cgroup_init_early(void); +int cgroup_init(void); + +/* + * Iteration helpers and macros. + */ + +struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos, + struct cgroup_subsys_state *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); +struct cgroup_subsys_state *css_next_descendant_post(struct cgroup_subsys_state *pos, + struct cgroup_subsys_state *css); + +struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset); +struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset); + +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); + +/** + * css_for_each_child - iterate through children of a css + * @pos: the css * to use as the loop cursor + * @parent: css whose children to walk + * + * Walk @parent's children. Must be called under rcu_read_lock(). + * + * If a subsystem synchronizes ->css_online() and the start of iteration, a + * css which finished ->css_online() is guaranteed to be visible in the + * future iterations and will stay visible until the last reference is put. + * A css which hasn't finished ->css_online() or already finished + * ->css_offline() may show up during traversal. It's each subsystem's + * responsibility to synchronize against on/offlining. + * + * It is allowed to temporarily drop RCU read lock during iteration. The + * caller is responsible for ensuring that @pos remains accessible until + * the start of the next iteration by, for example, bumping the css refcnt. + */ +#define css_for_each_child(pos, parent) \ + for ((pos) = css_next_child(NULL, (parent)); (pos); \ + (pos) = css_next_child((pos), (parent))) + +/** + * css_for_each_descendant_pre - pre-order walk of a css's descendants + * @pos: the css * to use as the loop cursor + * @root: css whose descendants to walk + * + * Walk @root's descendants. @root is included in the iteration and the + * first node to be visited. Must be called under rcu_read_lock(). + * + * If a subsystem synchronizes ->css_online() and the start of iteration, a + * css which finished ->css_online() is guaranteed to be visible in the + * future iterations and will stay visible until the last reference is put. + * A css which hasn't finished ->css_online() or already finished + * ->css_offline() may show up during traversal. It's each subsystem's + * responsibility to synchronize against on/offlining. + * + * For example, the following guarantees that a descendant can't escape + * state updates of its ancestors. + * + * my_online(@css) + * { + * Lock @css's parent and @css; + * Inherit state from the parent; + * Unlock both. + * } + * + * my_update_state(@css) + * { + * css_for_each_descendant_pre(@pos, @css) { + * Lock @pos; + * if (@pos == @css) + * Update @css's state; + * else + * Verify @pos is alive and inherit state from its parent; + * Unlock @pos; + * } + * } + * + * As long as the inheriting step, including checking the parent state, is + * enclosed inside @pos locking, double-locking the parent isn't necessary + * while inheriting. The state update to the parent is guaranteed to be + * visible by walking order and, as long as inheriting operations to the + * same @pos are atomic to each other, multiple updates racing each other + * still result in the correct state. It's guaranateed that at least one + * inheritance happens for any css after the latest update to its parent. + * + * If checking parent's state requires locking the parent, each inheriting + * iteration should lock and unlock both @pos->parent and @pos. + * + * Alternatively, a subsystem may choose to use a single global lock to + * synchronize ->css_online() and ->css_offline() against tree-walking + * operations. + * + * It is allowed to temporarily drop RCU read lock during iteration. The + * caller is responsible for ensuring that @pos remains accessible until + * the start of the next iteration by, for example, bumping the css refcnt. + */ +#define css_for_each_descendant_pre(pos, css) \ + for ((pos) = css_next_descendant_pre(NULL, (css)); (pos); \ + (pos) = css_next_descendant_pre((pos), (css))) + +/** + * css_for_each_descendant_post - post-order walk of a css's descendants + * @pos: the css * to use as the loop cursor + * @css: css whose descendants to walk + * + * Similar to css_for_each_descendant_pre() but performs post-order + * traversal instead. @root is included in the iteration and the last + * node to be visited. + * + * If a subsystem synchronizes ->css_online() and the start of iteration, a + * css which finished ->css_online() is guaranteed to be visible in the + * future iterations and will stay visible until the last reference is put. + * A css which hasn't finished ->css_online() or already finished + * ->css_offline() may show up during traversal. It's each subsystem's + * responsibility to synchronize against on/offlining. + * + * Note that the walk visibility guarantee example described in pre-order + * walk doesn't apply the same to post-order walks. + */ +#define css_for_each_descendant_post(pos, css) \ + for ((pos) = css_next_descendant_post(NULL, (css)); (pos); \ + (pos) = css_next_descendant_post((pos), (css))) + +/** + * cgroup_taskset_for_each - iterate cgroup_taskset + * @task: the loop cursor + * @tset: taskset to iterate + */ +#define cgroup_taskset_for_each(task, tset) \ + for ((task) = cgroup_taskset_first((tset)); (task); \ + (task) = cgroup_taskset_next((tset))) -extern int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns, - struct pid *pid, struct task_struct *tsk); +/* + * Inline functions. + */ /** * css_get - obtain a reference on the specified css @@ -118,8 +291,87 @@ static inline void css_put_many(struct cgroup_subsys_state *css, unsigned int n) percpu_ref_put_many(&css->refcnt, n); } -extern struct cgroup_root cgrp_dfl_root; -extern struct css_set init_css_set; +/** + * task_css_set_check - obtain a task's css_set with extra access conditions + * @task: the task to obtain css_set for + * @__c: extra condition expression to be passed to rcu_dereference_check() + * + * A task's css_set is RCU protected, initialized and exited while holding + * task_lock(), and can only be modified while holding both cgroup_mutex + * and task_lock() while the task is alive. This macro verifies that the + * caller is inside proper critical section and returns @task's css_set. + * + * The caller can also specify additional allowed conditions via @__c, such + * as locks used during the cgroup_subsys::attach() methods. + */ +#ifdef CONFIG_PROVE_RCU +extern struct mutex cgroup_mutex; +extern struct rw_semaphore css_set_rwsem; +#define task_css_set_check(task, __c) \ + rcu_dereference_check((task)->cgroups, \ + lockdep_is_held(&cgroup_mutex) || \ + lockdep_is_held(&css_set_rwsem) || \ + ((task)->flags & PF_EXITING) || (__c)) +#else +#define task_css_set_check(task, __c) \ + rcu_dereference((task)->cgroups) +#endif + +/** + * task_css_check - obtain css for (task, subsys) w/ extra access conds + * @task: the target task + * @subsys_id: the target subsystem ID + * @__c: extra condition expression to be passed to rcu_dereference_check() + * + * Return the cgroup_subsys_state for the (@task, @subsys_id) pair. The + * synchronization rules are the same as task_css_set_check(). + */ +#define task_css_check(task, subsys_id, __c) \ + task_css_set_check((task), (__c))->subsys[(subsys_id)] + +/** + * task_css_set - obtain a task's css_set + * @task: the task to obtain css_set for + * + * See task_css_set_check(). + */ +static inline struct css_set *task_css_set(struct task_struct *task) +{ + return task_css_set_check(task, false); +} + +/** + * task_css - obtain css for (task, subsys) + * @task: the target task + * @subsys_id: the target subsystem ID + * + * See task_css_check(). + */ +static inline struct cgroup_subsys_state *task_css(struct task_struct *task, + int subsys_id) +{ + return task_css_check(task, subsys_id, false); +} + +/** + * task_css_is_root - test whether a task belongs to the root css + * @task: the target task + * @subsys_id: the target subsystem ID + * + * Test whether @task belongs to the root css on the specified subsystem. + * May be invoked in any context. + */ +static inline bool task_css_is_root(struct task_struct *task, int subsys_id) +{ + return task_css_check(task, subsys_id, true) == + init_css_set.subsys[subsys_id]; +} + +static inline struct cgroup *task_cgroup(struct task_struct *task, + int subsys_id) +{ + return task_css(task, subsys_id)->cgroup; +} /** * cgroup_on_dfl - test whether a cgroup is on the default hierarchy @@ -236,284 +488,22 @@ static inline void pr_cont_cgroup_path(struct cgroup *cgrp) pr_cont_kernfs_path(cgrp->kn); } -char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen); - -int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts); -int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts); -int cgroup_rm_cftypes(struct cftype *cfts); - -bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor); - -struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset); -struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset); - -/** - * cgroup_taskset_for_each - iterate cgroup_taskset - * @task: the loop cursor - * @tset: taskset to iterate - */ -#define cgroup_taskset_for_each(task, tset) \ - for ((task) = cgroup_taskset_first((tset)); (task); \ - (task) = cgroup_taskset_next((tset))) - -#define SUBSYS(_x) extern struct cgroup_subsys _x ## _cgrp_subsys; -#include <linux/cgroup_subsys.h> -#undef SUBSYS - -/** - * task_css_set_check - obtain a task's css_set with extra access conditions - * @task: the task to obtain css_set for - * @__c: extra condition expression to be passed to rcu_dereference_check() - * - * A task's css_set is RCU protected, initialized and exited while holding - * task_lock(), and can only be modified while holding both cgroup_mutex - * and task_lock() while the task is alive. This macro verifies that the - * caller is inside proper critical section and returns @task's css_set. - * - * The caller can also specify additional allowed conditions via @__c, such - * as locks used during the cgroup_subsys::attach() methods. - */ -#ifdef CONFIG_PROVE_RCU -extern struct mutex cgroup_mutex; -extern struct rw_semaphore css_set_rwsem; -#define task_css_set_check(task, __c) \ - rcu_dereference_check((task)->cgroups, \ - lockdep_is_held(&cgroup_mutex) || \ - lockdep_is_held(&css_set_rwsem) || \ - ((task)->flags & PF_EXITING) || (__c)) -#else -#define task_css_set_check(task, __c) \ - rcu_dereference((task)->cgroups) -#endif - -/** - * task_css_check - obtain css for (task, subsys) w/ extra access conds - * @task: the target task - * @subsys_id: the target subsystem ID - * @__c: extra condition expression to be passed to rcu_dereference_check() - * - * Return the cgroup_subsys_state for the (@task, @subsys_id) pair. The - * synchronization rules are the same as task_css_set_check(). - */ -#define task_css_check(task, subsys_id, __c) \ - task_css_set_check((task), (__c))->subsys[(subsys_id)] - -/** - * task_css_set - obtain a task's css_set - * @task: the task to obtain css_set for - * - * See task_css_set_check(). - */ -static inline struct css_set *task_css_set(struct task_struct *task) -{ - return task_css_set_check(task, false); -} - -/** - * task_css - obtain css for (task, subsys) - * @task: the target task - * @subsys_id: the target subsystem ID - * - * See task_css_check(). - */ -static inline struct cgroup_subsys_state *task_css(struct task_struct *task, - int subsys_id) -{ - return task_css_check(task, subsys_id, false); -} - -/** - * task_css_is_root - test whether a task belongs to the root css - * @task: the target task - * @subsys_id: the target subsystem ID - * - * Test whether @task belongs to the root css on the specified subsystem. - * May be invoked in any context. - */ -static inline bool task_css_is_root(struct task_struct *task, int subsys_id) -{ - return task_css_check(task, subsys_id, true) == - init_css_set.subsys[subsys_id]; -} - -static inline struct cgroup *task_cgroup(struct task_struct *task, - int subsys_id) -{ - return task_css(task, subsys_id)->cgroup; -} - -struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos, - struct cgroup_subsys_state *parent); - -struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss); - -/** - * css_for_each_child - iterate through children of a css - * @pos: the css * to use as the loop cursor - * @parent: css whose children to walk - * - * Walk @parent's children. Must be called under rcu_read_lock(). - * - * If a subsystem synchronizes ->css_online() and the start of iteration, a - * css which finished ->css_online() is guaranteed to be visible in the - * future iterations and will stay visible until the last reference is put. - * A css which hasn't finished ->css_online() or already finished - * ->css_offline() may show up during traversal. It's each subsystem's - * responsibility to synchronize against on/offlining. - * - * It is allowed to temporarily drop RCU read lock during iteration. The - * caller is responsible for ensuring that @pos remains accessible until - * the start of the next iteration by, for example, bumping the css refcnt. - */ -#define css_for_each_child(pos, parent) \ - for ((pos) = css_next_child(NULL, (parent)); (pos); \ - (pos) = css_next_child((pos), (parent))) - -struct cgroup_subsys_state * -css_next_descendant_pre(struct cgroup_subsys_state *pos, - struct cgroup_subsys_state *css); - -struct cgroup_subsys_state * -css_rightmost_descendant(struct cgroup_subsys_state *pos); - -/** - * css_for_each_descendant_pre - pre-order walk of a css's descendants - * @pos: the css * to use as the loop cursor - * @root: css whose descendants to walk - * - * Walk @root's descendants. @root is included in the iteration and the - * first node to be visited. Must be called under rcu_read_lock(). - * - * If a subsystem synchronizes ->css_online() and the start of iteration, a - * css which finished ->css_online() is guaranteed to be visible in the - * future iterations and will stay visible until the last reference is put. - * A css which hasn't finished ->css_online() or already finished - * ->css_offline() may show up during traversal. It's each subsystem's - * responsibility to synchronize against on/offlining. - * - * For example, the following guarantees that a descendant can't escape - * state updates of its ancestors. - * - * my_online(@css) - * { - * Lock @css's parent and @css; - * Inherit state from the parent; - * Unlock both. - * } - * - * my_update_state(@css) - * { - * css_for_each_descendant_pre(@pos, @css) { - * Lock @pos; - * if (@pos == @css) - * Update @css's state; - * else - * Verify @pos is alive and inherit state from its parent; - * Unlock @pos; - * } - * } - * - * As long as the inheriting step, including checking the parent state, is - * enclosed inside @pos locking, double-locking the parent isn't necessary - * while inheriting. The state update to the parent is guaranteed to be - * visible by walking order and, as long as inheriting operations to the - * same @pos are atomic to each other, multiple updates racing each other - * still result in the correct state. It's guaranateed that at least one - * inheritance happens for any css after the latest update to its parent. - * - * If checking parent's state requires locking the parent, each inheriting - * iteration should lock and unlock both @pos->parent and @pos. - * - * Alternatively, a subsystem may choose to use a single global lock to - * synchronize ->css_online() and ->css_offline() against tree-walking - * operations. - * - * It is allowed to temporarily drop RCU read lock during iteration. The - * caller is responsible for ensuring that @pos remains accessible until - * the start of the next iteration by, for example, bumping the css refcnt. - */ -#define css_for_each_descendant_pre(pos, css) \ - for ((pos) = css_next_descendant_pre(NULL, (css)); (pos); \ - (pos) = css_next_descendant_pre((pos), (css))) - -struct cgroup_subsys_state * -css_next_descendant_post(struct cgroup_subsys_state *pos, - struct cgroup_subsys_state *css); - -/** - * css_for_each_descendant_post - post-order walk of a css's descendants - * @pos: the css * to use as the loop cursor - * @css: css whose descendants to walk - * - * Similar to css_for_each_descendant_pre() but performs post-order - * traversal instead. @root is included in the iteration and the last - * node to be visited. - * - * If a subsystem synchronizes ->css_online() and the start of iteration, a - * css which finished ->css_online() is guaranteed to be visible in the - * future iterations and will stay visible until the last reference is put. - * A css which hasn't finished ->css_online() or already finished - * ->css_offline() may show up during traversal. It's each subsystem's - * responsibility to synchronize against on/offlining. - * - * Note that the walk visibility guarantee example described in pre-order - * walk doesn't apply the same to post-order walks. - */ -#define css_for_each_descendant_post(pos, css) \ - for ((pos) = css_next_descendant_post(NULL, (css)); (pos); \ - (pos) = css_next_descendant_post((pos), (css))) - -bool css_has_online_children(struct cgroup_subsys_state *css); - -/* A css_task_iter should be treated as an opaque object */ -struct css_task_iter { - struct cgroup_subsys *ss; - - struct list_head *cset_pos; - struct list_head *cset_head; - - struct list_head *task_pos; - struct list_head *tasks_head; - struct list_head *mg_tasks_head; -}; - -void css_task_iter_start(struct cgroup_subsys_state *css, - struct css_task_iter *it); -struct task_struct *css_task_iter_next(struct css_task_iter *it); -void css_task_iter_end(struct css_task_iter *it); - -int cgroup_attach_task_all(struct task_struct *from, struct task_struct *); -int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from); - -struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgroup, - struct cgroup_subsys *ss); -struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry, - struct cgroup_subsys *ss); - #else /* !CONFIG_CGROUPS */ struct cgroup_subsys_state; -static inline int cgroup_init_early(void) { return 0; } -static inline int cgroup_init(void) { return 0; } +static inline void css_put(struct cgroup_subsys_state *css) {} +static inline int cgroup_attach_task_all(struct task_struct *from, + struct task_struct *t) { return 0; } +static inline int cgroupstats_build(struct cgroupstats *stats, + struct dentry *dentry) { return -EINVAL; } + static inline void cgroup_fork(struct task_struct *p) {} static inline void cgroup_post_fork(struct task_struct *p) {} static inline void cgroup_exit(struct task_struct *p) {} -static inline int cgroupstats_build(struct cgroupstats *stats, - struct dentry *dentry) -{ - return -EINVAL; -} - -static inline void css_put(struct cgroup_subsys_state *css) {} - -/* No cgroups - nothing to do */ -static inline int cgroup_attach_task_all(struct task_struct *from, - struct task_struct *t) -{ - return 0; -} +static inline int cgroup_init_early(void) { return 0; } +static inline int cgroup_init(void) { return 0; } #endif /* !CONFIG_CGROUPS */ |