1 #ifndef _LINUX_CGROUP_H
2 #define _LINUX_CGROUP_H
6 * Copyright (C) 2003 BULL SA
7 * Copyright (C) 2004-2006 Silicon Graphics, Inc.
11 #include <linux/sched.h>
12 #include <linux/cpumask.h>
13 #include <linux/nodemask.h>
14 #include <linux/rculist.h>
15 #include <linux/cgroupstats.h>
17 #include <linux/seq_file.h>
18 #include <linux/kernfs.h>
19 #include <linux/jump_label.h>
21 #include <linux/cgroup-defs.h>
26 * All weight knobs on the default hierarhcy should use the following min,
27 * default and max values. The default value is the logarithmic center of
28 * MIN and MAX and allows 100x to be expressed in both directions.
30 #define CGROUP_WEIGHT_MIN 1
31 #define CGROUP_WEIGHT_DFL 100
32 #define CGROUP_WEIGHT_MAX 10000
34 /* a css_task_iter should be treated as an opaque object */
35 struct css_task_iter {
36 struct cgroup_subsys *ss;
38 struct list_head *cset_pos;
39 struct list_head *cset_head;
41 struct list_head *task_pos;
42 struct list_head *tasks_head;
43 struct list_head *mg_tasks_head;
45 struct css_set *cur_cset;
46 struct task_struct *cur_task;
47 struct list_head iters_node; /* css_set->task_iters */
50 extern struct cgroup_root cgrp_dfl_root;
51 extern struct css_set init_css_set;
53 #define SUBSYS(_x) extern struct cgroup_subsys _x ## _cgrp_subsys;
54 #include <linux/cgroup_subsys.h>
58 extern struct static_key_true _x ## _cgrp_subsys_enabled_key; \
59 extern struct static_key_true _x ## _cgrp_subsys_on_dfl_key;
60 #include <linux/cgroup_subsys.h>
64 * cgroup_subsys_enabled - fast test on whether a subsys is enabled
65 * @ss: subsystem in question
67 #define cgroup_subsys_enabled(ss) \
68 static_branch_likely(&ss ## _enabled_key)
71 * cgroup_subsys_on_dfl - fast test on whether a subsys is on default hierarchy
72 * @ss: subsystem in question
74 #define cgroup_subsys_on_dfl(ss) \
75 static_branch_likely(&ss ## _on_dfl_key)
77 bool css_has_online_children(struct cgroup_subsys_state *css);
78 struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss);
79 struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgroup,
80 struct cgroup_subsys *ss);
81 struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
82 struct cgroup_subsys *ss);
84 bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor);
85 int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
86 int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
88 int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
89 int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
90 int cgroup_rm_cftypes(struct cftype *cfts);
91 void cgroup_file_notify(struct cgroup_file *cfile);
93 char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen);
94 int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry);
95 int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
96 struct pid *pid, struct task_struct *tsk);
98 void cgroup_fork(struct task_struct *p);
99 extern int cgroup_can_fork(struct task_struct *p);
100 extern void cgroup_cancel_fork(struct task_struct *p);
101 extern void cgroup_post_fork(struct task_struct *p);
102 void cgroup_exit(struct task_struct *p);
103 void cgroup_free(struct task_struct *p);
105 int cgroup_init_early(void);
106 int cgroup_init(void);
109 * Iteration helpers and macros.
112 struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos,
113 struct cgroup_subsys_state *parent);
114 struct cgroup_subsys_state *css_next_descendant_pre(struct cgroup_subsys_state *pos,
115 struct cgroup_subsys_state *css);
116 struct cgroup_subsys_state *css_rightmost_descendant(struct cgroup_subsys_state *pos);
117 struct cgroup_subsys_state *css_next_descendant_post(struct cgroup_subsys_state *pos,
118 struct cgroup_subsys_state *css);
120 struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset,
121 struct cgroup_subsys_state **dst_cssp);
122 struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset,
123 struct cgroup_subsys_state **dst_cssp);
125 void css_task_iter_start(struct cgroup_subsys_state *css,
126 struct css_task_iter *it);
127 struct task_struct *css_task_iter_next(struct css_task_iter *it);
128 void css_task_iter_end(struct css_task_iter *it);
131 * css_for_each_child - iterate through children of a css
132 * @pos: the css * to use as the loop cursor
133 * @parent: css whose children to walk
135 * Walk @parent's children. Must be called under rcu_read_lock().
137 * If a subsystem synchronizes ->css_online() and the start of iteration, a
138 * css which finished ->css_online() is guaranteed to be visible in the
139 * future iterations and will stay visible until the last reference is put.
140 * A css which hasn't finished ->css_online() or already finished
141 * ->css_offline() may show up during traversal. It's each subsystem's
142 * responsibility to synchronize against on/offlining.
144 * It is allowed to temporarily drop RCU read lock during iteration. The
145 * caller is responsible for ensuring that @pos remains accessible until
146 * the start of the next iteration by, for example, bumping the css refcnt.
148 #define css_for_each_child(pos, parent) \
149 for ((pos) = css_next_child(NULL, (parent)); (pos); \
150 (pos) = css_next_child((pos), (parent)))
153 * css_for_each_descendant_pre - pre-order walk of a css's descendants
154 * @pos: the css * to use as the loop cursor
155 * @root: css whose descendants to walk
157 * Walk @root's descendants. @root is included in the iteration and the
158 * first node to be visited. Must be called under rcu_read_lock().
160 * If a subsystem synchronizes ->css_online() and the start of iteration, a
161 * css which finished ->css_online() is guaranteed to be visible in the
162 * future iterations and will stay visible until the last reference is put.
163 * A css which hasn't finished ->css_online() or already finished
164 * ->css_offline() may show up during traversal. It's each subsystem's
165 * responsibility to synchronize against on/offlining.
167 * For example, the following guarantees that a descendant can't escape
168 * state updates of its ancestors.
172 * Lock @css's parent and @css;
173 * Inherit state from the parent;
177 * my_update_state(@css)
179 * css_for_each_descendant_pre(@pos, @css) {
182 * Update @css's state;
184 * Verify @pos is alive and inherit state from its parent;
189 * As long as the inheriting step, including checking the parent state, is
190 * enclosed inside @pos locking, double-locking the parent isn't necessary
191 * while inheriting. The state update to the parent is guaranteed to be
192 * visible by walking order and, as long as inheriting operations to the
193 * same @pos are atomic to each other, multiple updates racing each other
194 * still result in the correct state. It's guaranateed that at least one
195 * inheritance happens for any css after the latest update to its parent.
197 * If checking parent's state requires locking the parent, each inheriting
198 * iteration should lock and unlock both @pos->parent and @pos.
200 * Alternatively, a subsystem may choose to use a single global lock to
201 * synchronize ->css_online() and ->css_offline() against tree-walking
204 * It is allowed to temporarily drop RCU read lock during iteration. The
205 * caller is responsible for ensuring that @pos remains accessible until
206 * the start of the next iteration by, for example, bumping the css refcnt.
208 #define css_for_each_descendant_pre(pos, css) \
209 for ((pos) = css_next_descendant_pre(NULL, (css)); (pos); \
210 (pos) = css_next_descendant_pre((pos), (css)))
213 * css_for_each_descendant_post - post-order walk of a css's descendants
214 * @pos: the css * to use as the loop cursor
215 * @css: css whose descendants to walk
217 * Similar to css_for_each_descendant_pre() but performs post-order
218 * traversal instead. @root is included in the iteration and the last
219 * node to be visited.
221 * If a subsystem synchronizes ->css_online() and the start of iteration, a
222 * css which finished ->css_online() is guaranteed to be visible in the
223 * future iterations and will stay visible until the last reference is put.
224 * A css which hasn't finished ->css_online() or already finished
225 * ->css_offline() may show up during traversal. It's each subsystem's
226 * responsibility to synchronize against on/offlining.
228 * Note that the walk visibility guarantee example described in pre-order
229 * walk doesn't apply the same to post-order walks.
231 #define css_for_each_descendant_post(pos, css) \
232 for ((pos) = css_next_descendant_post(NULL, (css)); (pos); \
233 (pos) = css_next_descendant_post((pos), (css)))
236 * cgroup_taskset_for_each - iterate cgroup_taskset
237 * @task: the loop cursor
238 * @dst_css: the destination css
239 * @tset: taskset to iterate
241 * @tset may contain multiple tasks and they may belong to multiple
244 * On the v2 hierarchy, there may be tasks from multiple processes and they
245 * may not share the source or destination csses.
247 * On traditional hierarchies, when there are multiple tasks in @tset, if a
248 * task of a process is in @tset, all tasks of the process are in @tset.
249 * Also, all are guaranteed to share the same source and destination csses.
251 * Iteration is not in any specific order.
253 #define cgroup_taskset_for_each(task, dst_css, tset) \
254 for ((task) = cgroup_taskset_first((tset), &(dst_css)); \
256 (task) = cgroup_taskset_next((tset), &(dst_css)))
259 * cgroup_taskset_for_each_leader - iterate group leaders in a cgroup_taskset
260 * @leader: the loop cursor
261 * @dst_css: the destination css
262 * @tset: takset to iterate
264 * Iterate threadgroup leaders of @tset. For single-task migrations, @tset
265 * may not contain any.
267 #define cgroup_taskset_for_each_leader(leader, dst_css, tset) \
268 for ((leader) = cgroup_taskset_first((tset), &(dst_css)); \
270 (leader) = cgroup_taskset_next((tset), &(dst_css))) \
271 if ((leader) != (leader)->group_leader) \
280 * css_get - obtain a reference on the specified css
283 * The caller must already have a reference.
285 static inline void css_get(struct cgroup_subsys_state *css)
287 if (!(css->flags & CSS_NO_REF))
288 percpu_ref_get(&css->refcnt);
292 * css_get_many - obtain references on the specified css
294 * @n: number of references to get
296 * The caller must already have a reference.
298 static inline void css_get_many(struct cgroup_subsys_state *css, unsigned int n)
300 if (!(css->flags & CSS_NO_REF))
301 percpu_ref_get_many(&css->refcnt, n);
305 * css_tryget - try to obtain a reference on the specified css
308 * Obtain a reference on @css unless it already has reached zero and is
309 * being released. This function doesn't care whether @css is on or
310 * offline. The caller naturally needs to ensure that @css is accessible
311 * but doesn't have to be holding a reference on it - IOW, RCU protected
312 * access is good enough for this function. Returns %true if a reference
313 * count was successfully obtained; %false otherwise.
315 static inline bool css_tryget(struct cgroup_subsys_state *css)
317 if (!(css->flags & CSS_NO_REF))
318 return percpu_ref_tryget(&css->refcnt);
323 * css_tryget_online - try to obtain a reference on the specified css if online
326 * Obtain a reference on @css if it's online. The caller naturally needs
327 * to ensure that @css is accessible but doesn't have to be holding a
328 * reference on it - IOW, RCU protected access is good enough for this
329 * function. Returns %true if a reference count was successfully obtained;
332 static inline bool css_tryget_online(struct cgroup_subsys_state *css)
334 if (!(css->flags & CSS_NO_REF))
335 return percpu_ref_tryget_live(&css->refcnt);
340 * css_put - put a css reference
343 * Put a reference obtained via css_get() and css_tryget_online().
345 static inline void css_put(struct cgroup_subsys_state *css)
347 if (!(css->flags & CSS_NO_REF))
348 percpu_ref_put(&css->refcnt);
352 * css_put_many - put css references
354 * @n: number of references to put
356 * Put references obtained via css_get() and css_tryget_online().
358 static inline void css_put_many(struct cgroup_subsys_state *css, unsigned int n)
360 if (!(css->flags & CSS_NO_REF))
361 percpu_ref_put_many(&css->refcnt, n);
365 * task_css_set_check - obtain a task's css_set with extra access conditions
366 * @task: the task to obtain css_set for
367 * @__c: extra condition expression to be passed to rcu_dereference_check()
369 * A task's css_set is RCU protected, initialized and exited while holding
370 * task_lock(), and can only be modified while holding both cgroup_mutex
371 * and task_lock() while the task is alive. This macro verifies that the
372 * caller is inside proper critical section and returns @task's css_set.
374 * The caller can also specify additional allowed conditions via @__c, such
375 * as locks used during the cgroup_subsys::attach() methods.
377 #ifdef CONFIG_PROVE_RCU
378 extern struct mutex cgroup_mutex;
379 extern spinlock_t css_set_lock;
380 #define task_css_set_check(task, __c) \
381 rcu_dereference_check((task)->cgroups, \
382 lockdep_is_held(&cgroup_mutex) || \
383 lockdep_is_held(&css_set_lock) || \
384 ((task)->flags & PF_EXITING) || (__c))
386 #define task_css_set_check(task, __c) \
387 rcu_dereference((task)->cgroups)
391 * task_css_check - obtain css for (task, subsys) w/ extra access conds
392 * @task: the target task
393 * @subsys_id: the target subsystem ID
394 * @__c: extra condition expression to be passed to rcu_dereference_check()
396 * Return the cgroup_subsys_state for the (@task, @subsys_id) pair. The
397 * synchronization rules are the same as task_css_set_check().
399 #define task_css_check(task, subsys_id, __c) \
400 task_css_set_check((task), (__c))->subsys[(subsys_id)]
403 * task_css_set - obtain a task's css_set
404 * @task: the task to obtain css_set for
406 * See task_css_set_check().
408 static inline struct css_set *task_css_set(struct task_struct *task)
410 return task_css_set_check(task, false);
414 * task_css - obtain css for (task, subsys)
415 * @task: the target task
416 * @subsys_id: the target subsystem ID
418 * See task_css_check().
420 static inline struct cgroup_subsys_state *task_css(struct task_struct *task,
423 return task_css_check(task, subsys_id, false);
427 * task_get_css - find and get the css for (task, subsys)
428 * @task: the target task
429 * @subsys_id: the target subsystem ID
431 * Find the css for the (@task, @subsys_id) combination, increment a
432 * reference on and return it. This function is guaranteed to return a
435 static inline struct cgroup_subsys_state *
436 task_get_css(struct task_struct *task, int subsys_id)
438 struct cgroup_subsys_state *css;
442 css = task_css(task, subsys_id);
443 if (likely(css_tryget_online(css)))
452 * task_css_is_root - test whether a task belongs to the root css
453 * @task: the target task
454 * @subsys_id: the target subsystem ID
456 * Test whether @task belongs to the root css on the specified subsystem.
457 * May be invoked in any context.
459 static inline bool task_css_is_root(struct task_struct *task, int subsys_id)
461 return task_css_check(task, subsys_id, true) ==
462 init_css_set.subsys[subsys_id];
465 static inline struct cgroup *task_cgroup(struct task_struct *task,
468 return task_css(task, subsys_id)->cgroup;
471 /* no synchronization, the result can only be used as a hint */
472 static inline bool cgroup_is_populated(struct cgroup *cgrp)
474 return cgrp->populated_cnt;
477 /* returns ino associated with a cgroup */
478 static inline ino_t cgroup_ino(struct cgroup *cgrp)
480 return cgrp->kn->ino;
483 /* cft/css accessors for cftype->write() operation */
484 static inline struct cftype *of_cft(struct kernfs_open_file *of)
489 struct cgroup_subsys_state *of_css(struct kernfs_open_file *of);
491 /* cft/css accessors for cftype->seq_*() operations */
492 static inline struct cftype *seq_cft(struct seq_file *seq)
494 return of_cft(seq->private);
497 static inline struct cgroup_subsys_state *seq_css(struct seq_file *seq)
499 return of_css(seq->private);
503 * Name / path handling functions. All are thin wrappers around the kernfs
504 * counterparts and can be called under any context.
507 static inline int cgroup_name(struct cgroup *cgrp, char *buf, size_t buflen)
509 return kernfs_name(cgrp->kn, buf, buflen);
512 static inline char * __must_check cgroup_path(struct cgroup *cgrp, char *buf,
515 return kernfs_path(cgrp->kn, buf, buflen);
518 static inline void pr_cont_cgroup_name(struct cgroup *cgrp)
520 pr_cont_kernfs_name(cgrp->kn);
523 static inline void pr_cont_cgroup_path(struct cgroup *cgrp)
525 pr_cont_kernfs_path(cgrp->kn);
528 #else /* !CONFIG_CGROUPS */
530 struct cgroup_subsys_state;
532 static inline void css_put(struct cgroup_subsys_state *css) {}
533 static inline int cgroup_attach_task_all(struct task_struct *from,
534 struct task_struct *t) { return 0; }
535 static inline int cgroupstats_build(struct cgroupstats *stats,
536 struct dentry *dentry) { return -EINVAL; }
538 static inline void cgroup_fork(struct task_struct *p) {}
539 static inline int cgroup_can_fork(struct task_struct *p) { return 0; }
540 static inline void cgroup_cancel_fork(struct task_struct *p) {}
541 static inline void cgroup_post_fork(struct task_struct *p) {}
542 static inline void cgroup_exit(struct task_struct *p) {}
543 static inline void cgroup_free(struct task_struct *p) {}
545 static inline int cgroup_init_early(void) { return 0; }
546 static inline int cgroup_init(void) { return 0; }
548 #endif /* !CONFIG_CGROUPS */
550 #endif /* _LINUX_CGROUP_H */