2 * Generic process-grouping system.
4 * Based originally on the cpuset system, extracted by Paul Menage
5 * Copyright (C) 2006 Google, Inc
7 * Notifications support
8 * Copyright (C) 2009 Nokia Corporation
9 * Author: Kirill A. Shutemov
11 * Copyright notices from the original cpuset code:
12 * --------------------------------------------------
13 * Copyright (C) 2003 BULL SA.
14 * Copyright (C) 2004-2006 Silicon Graphics, Inc.
16 * Portions derived from Patrick Mochel's sysfs code.
17 * sysfs is Copyright (c) 2001-3 Patrick Mochel
19 * 2003-10-10 Written by Simon Derr.
20 * 2003-10-22 Updates by Stephen Hemminger.
21 * 2004 May-July Rework by Paul Jackson.
22 * ---------------------------------------------------
24 * This file is subject to the terms and conditions of the GNU General Public
25 * License. See the file COPYING in the main directory of the Linux
26 * distribution for more details.
29 #include <linux/cgroup.h>
30 #include <linux/cred.h>
31 #include <linux/ctype.h>
32 #include <linux/errno.h>
33 #include <linux/init_task.h>
34 #include <linux/kernel.h>
35 #include <linux/list.h>
37 #include <linux/mutex.h>
38 #include <linux/mount.h>
39 #include <linux/pagemap.h>
40 #include <linux/proc_fs.h>
41 #include <linux/rcupdate.h>
42 #include <linux/sched.h>
43 #include <linux/slab.h>
44 #include <linux/spinlock.h>
45 #include <linux/rwsem.h>
46 #include <linux/string.h>
47 #include <linux/sort.h>
48 #include <linux/kmod.h>
49 #include <linux/delayacct.h>
50 #include <linux/cgroupstats.h>
51 #include <linux/hashtable.h>
52 #include <linux/pid_namespace.h>
53 #include <linux/idr.h>
54 #include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
55 #include <linux/kthread.h>
56 #include <linux/delay.h>
58 #include <linux/atomic.h>
61 * pidlists linger the following amount before being destroyed. The goal
62 * is avoiding frequent destruction in the middle of consecutive read calls
63 * Expiring in the middle is a performance problem not a correctness one.
64 * 1 sec should be enough.
66 #define CGROUP_PIDLIST_DESTROY_DELAY HZ
68 #define CGROUP_FILE_NAME_MAX (MAX_CGROUP_TYPE_NAMELEN + \
72 * cgroup_tree_mutex nests above cgroup_mutex and protects cftypes, file
73 * creation/removal and hierarchy changing operations including cgroup
74 * creation, removal, css association and controller rebinding. This outer
75 * lock is needed mainly to resolve the circular dependency between kernfs
76 * active ref and cgroup_mutex. cgroup_tree_mutex nests above both.
78 static DEFINE_MUTEX(cgroup_tree_mutex);
81 * cgroup_mutex is the master lock. Any modification to cgroup or its
82 * hierarchy must be performed while holding it.
84 * css_set_rwsem protects task->cgroups pointer, the list of css_set
85 * objects, and the chain of tasks off each css_set.
87 * These locks are exported if CONFIG_PROVE_RCU so that accessors in
88 * cgroup.h can use them for lockdep annotations.
90 #ifdef CONFIG_PROVE_RCU
91 DEFINE_MUTEX(cgroup_mutex);
92 DECLARE_RWSEM(css_set_rwsem);
93 EXPORT_SYMBOL_GPL(cgroup_mutex);
94 EXPORT_SYMBOL_GPL(css_set_rwsem);
96 static DEFINE_MUTEX(cgroup_mutex);
97 static DECLARE_RWSEM(css_set_rwsem);
101 * Protects cgroup_subsys->release_agent_path. Modifying it also requires
102 * cgroup_mutex. Reading requires either cgroup_mutex or this spinlock.
104 static DEFINE_SPINLOCK(release_agent_path_lock);
106 #define cgroup_assert_mutexes_or_rcu_locked() \
107 rcu_lockdep_assert(rcu_read_lock_held() || \
108 lockdep_is_held(&cgroup_tree_mutex) || \
109 lockdep_is_held(&cgroup_mutex), \
110 "cgroup_[tree_]mutex or RCU read lock required");
113 * cgroup destruction makes heavy use of work items and there can be a lot
114 * of concurrent destructions. Use a separate workqueue so that cgroup
115 * destruction work items don't end up filling up max_active of system_wq
116 * which may lead to deadlock.
118 static struct workqueue_struct *cgroup_destroy_wq;
121 * pidlist destructions need to be flushed on cgroup destruction. Use a
122 * separate workqueue as flush domain.
124 static struct workqueue_struct *cgroup_pidlist_destroy_wq;
126 /* generate an array of cgroup subsystem pointers */
127 #define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys,
128 static struct cgroup_subsys *cgroup_subsys[] = {
129 #include <linux/cgroup_subsys.h>
133 /* array of cgroup subsystem names */
134 #define SUBSYS(_x) [_x ## _cgrp_id] = #_x,
135 static const char *cgroup_subsys_name[] = {
136 #include <linux/cgroup_subsys.h>
141 * The default hierarchy, reserved for the subsystems that are otherwise
142 * unattached - it never has more than a single cgroup, and all tasks are
143 * part of that cgroup.
145 struct cgroup_root cgrp_dfl_root;
148 * The default hierarchy always exists but is hidden until mounted for the
149 * first time. This is for backward compatibility.
151 static bool cgrp_dfl_root_visible;
153 /* The list of hierarchy roots */
155 static LIST_HEAD(cgroup_roots);
156 static int cgroup_root_count;
158 /* hierarchy ID allocation and mapping, protected by cgroup_mutex */
159 static DEFINE_IDR(cgroup_hierarchy_idr);
162 * Assign a monotonically increasing serial number to cgroups. It
163 * guarantees cgroups with bigger numbers are newer than those with smaller
164 * numbers. Also, as cgroups are always appended to the parent's
165 * ->children list, it guarantees that sibling cgroups are always sorted in
166 * the ascending serial number order on the list. Protected by
169 static u64 cgroup_serial_nr_next = 1;
171 /* This flag indicates whether tasks in the fork and exit paths should
172 * check for fork/exit handlers to call. This avoids us having to do
173 * extra work in the fork/exit path if none of the subsystems need to
176 static int need_forkexit_callback __read_mostly;
178 static struct cftype cgroup_base_files[];
180 static void cgroup_put(struct cgroup *cgrp);
181 static int rebind_subsystems(struct cgroup_root *dst_root,
182 unsigned long ss_mask);
183 static void cgroup_destroy_css_killed(struct cgroup *cgrp);
184 static int cgroup_destroy_locked(struct cgroup *cgrp);
185 static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss);
186 static void kill_css(struct cgroup_subsys_state *css);
187 static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
189 static void cgroup_pidlist_destroy_all(struct cgroup *cgrp);
192 * cgroup_css - obtain a cgroup's css for the specified subsystem
193 * @cgrp: the cgroup of interest
194 * @ss: the subsystem of interest (%NULL returns the dummy_css)
196 * Return @cgrp's css (cgroup_subsys_state) associated with @ss. This
197 * function must be called either under cgroup_mutex or rcu_read_lock() and
198 * the caller is responsible for pinning the returned css if it wants to
199 * keep accessing it outside the said locks. This function may return
200 * %NULL if @cgrp doesn't have @subsys_id enabled.
202 static struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp,
203 struct cgroup_subsys *ss)
206 return rcu_dereference_check(cgrp->subsys[ss->id],
207 lockdep_is_held(&cgroup_tree_mutex) ||
208 lockdep_is_held(&cgroup_mutex));
210 return &cgrp->dummy_css;
214 * cgroup_e_css - obtain a cgroup's effective css for the specified subsystem
215 * @cgrp: the cgroup of interest
216 * @ss: the subsystem of interest (%NULL returns the dummy_css)
218 * Similar to cgroup_css() but returns the effctive css, which is defined
219 * as the matching css of the nearest ancestor including self which has @ss
220 * enabled. If @ss is associated with the hierarchy @cgrp is on, this
221 * function is guaranteed to return non-NULL css.
223 static struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp,
224 struct cgroup_subsys *ss)
226 lockdep_assert_held(&cgroup_mutex);
229 return &cgrp->dummy_css;
231 if (!(cgrp->root->subsys_mask & (1 << ss->id)))
234 while (cgrp->parent &&
235 !(cgrp->parent->child_subsys_mask & (1 << ss->id)))
238 return cgroup_css(cgrp, ss);
241 /* convenient tests for these bits */
242 static inline bool cgroup_is_dead(const struct cgroup *cgrp)
244 return test_bit(CGRP_DEAD, &cgrp->flags);
247 struct cgroup_subsys_state *seq_css(struct seq_file *seq)
249 struct kernfs_open_file *of = seq->private;
250 struct cgroup *cgrp = of->kn->parent->priv;
251 struct cftype *cft = seq_cft(seq);
254 * This is open and unprotected implementation of cgroup_css().
255 * seq_css() is only called from a kernfs file operation which has
256 * an active reference on the file. Because all the subsystem
257 * files are drained before a css is disassociated with a cgroup,
258 * the matching css from the cgroup's subsys table is guaranteed to
259 * be and stay valid until the enclosing operation is complete.
262 return rcu_dereference_raw(cgrp->subsys[cft->ss->id]);
264 return &cgrp->dummy_css;
266 EXPORT_SYMBOL_GPL(seq_css);
269 * cgroup_is_descendant - test ancestry
270 * @cgrp: the cgroup to be tested
271 * @ancestor: possible ancestor of @cgrp
273 * Test whether @cgrp is a descendant of @ancestor. It also returns %true
274 * if @cgrp == @ancestor. This function is safe to call as long as @cgrp
275 * and @ancestor are accessible.
277 bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor)
280 if (cgrp == ancestor)
287 static int cgroup_is_releasable(const struct cgroup *cgrp)
290 (1 << CGRP_RELEASABLE) |
291 (1 << CGRP_NOTIFY_ON_RELEASE);
292 return (cgrp->flags & bits) == bits;
295 static int notify_on_release(const struct cgroup *cgrp)
297 return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
301 * for_each_css - iterate all css's of a cgroup
302 * @css: the iteration cursor
303 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
304 * @cgrp: the target cgroup to iterate css's of
306 * Should be called under cgroup_[tree_]mutex.
308 #define for_each_css(css, ssid, cgrp) \
309 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
310 if (!((css) = rcu_dereference_check( \
311 (cgrp)->subsys[(ssid)], \
312 lockdep_is_held(&cgroup_tree_mutex) || \
313 lockdep_is_held(&cgroup_mutex)))) { } \
317 * for_each_e_css - iterate all effective css's of a cgroup
318 * @css: the iteration cursor
319 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
320 * @cgrp: the target cgroup to iterate css's of
322 * Should be called under cgroup_[tree_]mutex.
324 #define for_each_e_css(css, ssid, cgrp) \
325 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
326 if (!((css) = cgroup_e_css(cgrp, cgroup_subsys[(ssid)]))) \
331 * for_each_subsys - iterate all enabled cgroup subsystems
332 * @ss: the iteration cursor
333 * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
335 #define for_each_subsys(ss, ssid) \
336 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT && \
337 (((ss) = cgroup_subsys[ssid]) || true); (ssid)++)
339 /* iterate across the hierarchies */
340 #define for_each_root(root) \
341 list_for_each_entry((root), &cgroup_roots, root_list)
343 /* iterate over child cgrps, lock should be held throughout iteration */
344 #define cgroup_for_each_live_child(child, cgrp) \
345 list_for_each_entry((child), &(cgrp)->children, sibling) \
346 if (({ lockdep_assert_held(&cgroup_tree_mutex); \
347 cgroup_is_dead(child); })) \
352 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
353 * @cgrp: the cgroup to be checked for liveness
355 * On success, returns true; the mutex should be later unlocked. On
356 * failure returns false with no lock held.
358 static bool cgroup_lock_live_group(struct cgroup *cgrp)
360 mutex_lock(&cgroup_mutex);
361 if (cgroup_is_dead(cgrp)) {
362 mutex_unlock(&cgroup_mutex);
368 /* the list of cgroups eligible for automatic release. Protected by
369 * release_list_lock */
370 static LIST_HEAD(release_list);
371 static DEFINE_RAW_SPINLOCK(release_list_lock);
372 static void cgroup_release_agent(struct work_struct *work);
373 static DECLARE_WORK(release_agent_work, cgroup_release_agent);
374 static void check_for_release(struct cgroup *cgrp);
377 * A cgroup can be associated with multiple css_sets as different tasks may
378 * belong to different cgroups on different hierarchies. In the other
379 * direction, a css_set is naturally associated with multiple cgroups.
380 * This M:N relationship is represented by the following link structure
381 * which exists for each association and allows traversing the associations
384 struct cgrp_cset_link {
385 /* the cgroup and css_set this link associates */
387 struct css_set *cset;
389 /* list of cgrp_cset_links anchored at cgrp->cset_links */
390 struct list_head cset_link;
392 /* list of cgrp_cset_links anchored at css_set->cgrp_links */
393 struct list_head cgrp_link;
397 * The default css_set - used by init and its children prior to any
398 * hierarchies being mounted. It contains a pointer to the root state
399 * for each subsystem. Also used to anchor the list of css_sets. Not
400 * reference-counted, to improve performance when child cgroups
401 * haven't been created.
403 static struct css_set init_css_set = {
404 .refcount = ATOMIC_INIT(1),
405 .cgrp_links = LIST_HEAD_INIT(init_css_set.cgrp_links),
406 .tasks = LIST_HEAD_INIT(init_css_set.tasks),
407 .mg_tasks = LIST_HEAD_INIT(init_css_set.mg_tasks),
408 .mg_preload_node = LIST_HEAD_INIT(init_css_set.mg_preload_node),
409 .mg_node = LIST_HEAD_INIT(init_css_set.mg_node),
412 static int css_set_count = 1; /* 1 for init_css_set */
415 * hash table for cgroup groups. This improves the performance to find
416 * an existing css_set. This hash doesn't (currently) take into
417 * account cgroups in empty hierarchies.
419 #define CSS_SET_HASH_BITS 7
420 static DEFINE_HASHTABLE(css_set_table, CSS_SET_HASH_BITS);
422 static unsigned long css_set_hash(struct cgroup_subsys_state *css[])
424 unsigned long key = 0UL;
425 struct cgroup_subsys *ss;
428 for_each_subsys(ss, i)
429 key += (unsigned long)css[i];
430 key = (key >> 16) ^ key;
435 static void put_css_set_locked(struct css_set *cset, bool taskexit)
437 struct cgrp_cset_link *link, *tmp_link;
438 struct cgroup_subsys *ss;
441 lockdep_assert_held(&css_set_rwsem);
443 if (!atomic_dec_and_test(&cset->refcount))
446 /* This css_set is dead. unlink it and release cgroup refcounts */
447 for_each_subsys(ss, ssid)
448 list_del(&cset->e_cset_node[ssid]);
449 hash_del(&cset->hlist);
452 list_for_each_entry_safe(link, tmp_link, &cset->cgrp_links, cgrp_link) {
453 struct cgroup *cgrp = link->cgrp;
455 list_del(&link->cset_link);
456 list_del(&link->cgrp_link);
458 /* @cgrp can't go away while we're holding css_set_rwsem */
459 if (list_empty(&cgrp->cset_links) && notify_on_release(cgrp)) {
461 set_bit(CGRP_RELEASABLE, &cgrp->flags);
462 check_for_release(cgrp);
468 kfree_rcu(cset, rcu_head);
471 static void put_css_set(struct css_set *cset, bool taskexit)
474 * Ensure that the refcount doesn't hit zero while any readers
475 * can see it. Similar to atomic_dec_and_lock(), but for an
478 if (atomic_add_unless(&cset->refcount, -1, 1))
481 down_write(&css_set_rwsem);
482 put_css_set_locked(cset, taskexit);
483 up_write(&css_set_rwsem);
487 * refcounted get/put for css_set objects
489 static inline void get_css_set(struct css_set *cset)
491 atomic_inc(&cset->refcount);
495 * compare_css_sets - helper function for find_existing_css_set().
496 * @cset: candidate css_set being tested
497 * @old_cset: existing css_set for a task
498 * @new_cgrp: cgroup that's being entered by the task
499 * @template: desired set of css pointers in css_set (pre-calculated)
501 * Returns true if "cset" matches "old_cset" except for the hierarchy
502 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
504 static bool compare_css_sets(struct css_set *cset,
505 struct css_set *old_cset,
506 struct cgroup *new_cgrp,
507 struct cgroup_subsys_state *template[])
509 struct list_head *l1, *l2;
512 * On the default hierarchy, there can be csets which are
513 * associated with the same set of cgroups but different csses.
514 * Let's first ensure that csses match.
516 if (memcmp(template, cset->subsys, sizeof(cset->subsys)))
520 * Compare cgroup pointers in order to distinguish between
521 * different cgroups in hierarchies. As different cgroups may
522 * share the same effective css, this comparison is always
525 l1 = &cset->cgrp_links;
526 l2 = &old_cset->cgrp_links;
528 struct cgrp_cset_link *link1, *link2;
529 struct cgroup *cgrp1, *cgrp2;
533 /* See if we reached the end - both lists are equal length. */
534 if (l1 == &cset->cgrp_links) {
535 BUG_ON(l2 != &old_cset->cgrp_links);
538 BUG_ON(l2 == &old_cset->cgrp_links);
540 /* Locate the cgroups associated with these links. */
541 link1 = list_entry(l1, struct cgrp_cset_link, cgrp_link);
542 link2 = list_entry(l2, struct cgrp_cset_link, cgrp_link);
545 /* Hierarchies should be linked in the same order. */
546 BUG_ON(cgrp1->root != cgrp2->root);
549 * If this hierarchy is the hierarchy of the cgroup
550 * that's changing, then we need to check that this
551 * css_set points to the new cgroup; if it's any other
552 * hierarchy, then this css_set should point to the
553 * same cgroup as the old css_set.
555 if (cgrp1->root == new_cgrp->root) {
556 if (cgrp1 != new_cgrp)
567 * find_existing_css_set - init css array and find the matching css_set
568 * @old_cset: the css_set that we're using before the cgroup transition
569 * @cgrp: the cgroup that we're moving into
570 * @template: out param for the new set of csses, should be clear on entry
572 static struct css_set *find_existing_css_set(struct css_set *old_cset,
574 struct cgroup_subsys_state *template[])
576 struct cgroup_root *root = cgrp->root;
577 struct cgroup_subsys *ss;
578 struct css_set *cset;
583 * Build the set of subsystem state objects that we want to see in the
584 * new css_set. while subsystems can change globally, the entries here
585 * won't change, so no need for locking.
587 for_each_subsys(ss, i) {
588 if (root->subsys_mask & (1UL << i)) {
590 * @ss is in this hierarchy, so we want the
591 * effective css from @cgrp.
593 template[i] = cgroup_e_css(cgrp, ss);
596 * @ss is not in this hierarchy, so we don't want
599 template[i] = old_cset->subsys[i];
603 key = css_set_hash(template);
604 hash_for_each_possible(css_set_table, cset, hlist, key) {
605 if (!compare_css_sets(cset, old_cset, cgrp, template))
608 /* This css_set matches what we need */
612 /* No existing cgroup group matched */
616 static void free_cgrp_cset_links(struct list_head *links_to_free)
618 struct cgrp_cset_link *link, *tmp_link;
620 list_for_each_entry_safe(link, tmp_link, links_to_free, cset_link) {
621 list_del(&link->cset_link);
627 * allocate_cgrp_cset_links - allocate cgrp_cset_links
628 * @count: the number of links to allocate
629 * @tmp_links: list_head the allocated links are put on
631 * Allocate @count cgrp_cset_link structures and chain them on @tmp_links
632 * through ->cset_link. Returns 0 on success or -errno.
634 static int allocate_cgrp_cset_links(int count, struct list_head *tmp_links)
636 struct cgrp_cset_link *link;
639 INIT_LIST_HEAD(tmp_links);
641 for (i = 0; i < count; i++) {
642 link = kzalloc(sizeof(*link), GFP_KERNEL);
644 free_cgrp_cset_links(tmp_links);
647 list_add(&link->cset_link, tmp_links);
653 * link_css_set - a helper function to link a css_set to a cgroup
654 * @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()
655 * @cset: the css_set to be linked
656 * @cgrp: the destination cgroup
658 static void link_css_set(struct list_head *tmp_links, struct css_set *cset,
661 struct cgrp_cset_link *link;
663 BUG_ON(list_empty(tmp_links));
665 if (cgroup_on_dfl(cgrp))
666 cset->dfl_cgrp = cgrp;
668 link = list_first_entry(tmp_links, struct cgrp_cset_link, cset_link);
671 list_move(&link->cset_link, &cgrp->cset_links);
673 * Always add links to the tail of the list so that the list
674 * is sorted by order of hierarchy creation
676 list_add_tail(&link->cgrp_link, &cset->cgrp_links);
680 * find_css_set - return a new css_set with one cgroup updated
681 * @old_cset: the baseline css_set
682 * @cgrp: the cgroup to be updated
684 * Return a new css_set that's equivalent to @old_cset, but with @cgrp
685 * substituted into the appropriate hierarchy.
687 static struct css_set *find_css_set(struct css_set *old_cset,
690 struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT] = { };
691 struct css_set *cset;
692 struct list_head tmp_links;
693 struct cgrp_cset_link *link;
694 struct cgroup_subsys *ss;
698 lockdep_assert_held(&cgroup_mutex);
700 /* First see if we already have a cgroup group that matches
702 down_read(&css_set_rwsem);
703 cset = find_existing_css_set(old_cset, cgrp, template);
706 up_read(&css_set_rwsem);
711 cset = kzalloc(sizeof(*cset), GFP_KERNEL);
715 /* Allocate all the cgrp_cset_link objects that we'll need */
716 if (allocate_cgrp_cset_links(cgroup_root_count, &tmp_links) < 0) {
721 atomic_set(&cset->refcount, 1);
722 INIT_LIST_HEAD(&cset->cgrp_links);
723 INIT_LIST_HEAD(&cset->tasks);
724 INIT_LIST_HEAD(&cset->mg_tasks);
725 INIT_LIST_HEAD(&cset->mg_preload_node);
726 INIT_LIST_HEAD(&cset->mg_node);
727 INIT_HLIST_NODE(&cset->hlist);
729 /* Copy the set of subsystem state objects generated in
730 * find_existing_css_set() */
731 memcpy(cset->subsys, template, sizeof(cset->subsys));
733 down_write(&css_set_rwsem);
734 /* Add reference counts and links from the new css_set. */
735 list_for_each_entry(link, &old_cset->cgrp_links, cgrp_link) {
736 struct cgroup *c = link->cgrp;
738 if (c->root == cgrp->root)
740 link_css_set(&tmp_links, cset, c);
743 BUG_ON(!list_empty(&tmp_links));
747 /* Add @cset to the hash table */
748 key = css_set_hash(cset->subsys);
749 hash_add(css_set_table, &cset->hlist, key);
751 for_each_subsys(ss, ssid)
752 list_add_tail(&cset->e_cset_node[ssid],
753 &cset->subsys[ssid]->cgroup->e_csets[ssid]);
755 up_write(&css_set_rwsem);
760 static struct cgroup_root *cgroup_root_from_kf(struct kernfs_root *kf_root)
762 struct cgroup *root_cgrp = kf_root->kn->priv;
764 return root_cgrp->root;
767 static int cgroup_init_root_id(struct cgroup_root *root)
771 lockdep_assert_held(&cgroup_mutex);
773 id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, 0, 0, GFP_KERNEL);
777 root->hierarchy_id = id;
781 static void cgroup_exit_root_id(struct cgroup_root *root)
783 lockdep_assert_held(&cgroup_mutex);
785 if (root->hierarchy_id) {
786 idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
787 root->hierarchy_id = 0;
791 static void cgroup_free_root(struct cgroup_root *root)
794 /* hierarhcy ID shoulid already have been released */
795 WARN_ON_ONCE(root->hierarchy_id);
797 idr_destroy(&root->cgroup_idr);
802 static void cgroup_destroy_root(struct cgroup_root *root)
804 struct cgroup *cgrp = &root->cgrp;
805 struct cgrp_cset_link *link, *tmp_link;
807 mutex_lock(&cgroup_tree_mutex);
808 mutex_lock(&cgroup_mutex);
810 BUG_ON(atomic_read(&root->nr_cgrps));
811 BUG_ON(!list_empty(&cgrp->children));
813 /* Rebind all subsystems back to the default hierarchy */
814 rebind_subsystems(&cgrp_dfl_root, root->subsys_mask);
817 * Release all the links from cset_links to this hierarchy's
820 down_write(&css_set_rwsem);
822 list_for_each_entry_safe(link, tmp_link, &cgrp->cset_links, cset_link) {
823 list_del(&link->cset_link);
824 list_del(&link->cgrp_link);
827 up_write(&css_set_rwsem);
829 if (!list_empty(&root->root_list)) {
830 list_del(&root->root_list);
834 cgroup_exit_root_id(root);
836 mutex_unlock(&cgroup_mutex);
837 mutex_unlock(&cgroup_tree_mutex);
839 kernfs_destroy_root(root->kf_root);
840 cgroup_free_root(root);
843 /* look up cgroup associated with given css_set on the specified hierarchy */
844 static struct cgroup *cset_cgroup_from_root(struct css_set *cset,
845 struct cgroup_root *root)
847 struct cgroup *res = NULL;
849 lockdep_assert_held(&cgroup_mutex);
850 lockdep_assert_held(&css_set_rwsem);
852 if (cset == &init_css_set) {
855 struct cgrp_cset_link *link;
857 list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
858 struct cgroup *c = link->cgrp;
860 if (c->root == root) {
872 * Return the cgroup for "task" from the given hierarchy. Must be
873 * called with cgroup_mutex and css_set_rwsem held.
875 static struct cgroup *task_cgroup_from_root(struct task_struct *task,
876 struct cgroup_root *root)
879 * No need to lock the task - since we hold cgroup_mutex the
880 * task can't change groups, so the only thing that can happen
881 * is that it exits and its css is set back to init_css_set.
883 return cset_cgroup_from_root(task_css_set(task), root);
887 * A task must hold cgroup_mutex to modify cgroups.
889 * Any task can increment and decrement the count field without lock.
890 * So in general, code holding cgroup_mutex can't rely on the count
891 * field not changing. However, if the count goes to zero, then only
892 * cgroup_attach_task() can increment it again. Because a count of zero
893 * means that no tasks are currently attached, therefore there is no
894 * way a task attached to that cgroup can fork (the other way to
895 * increment the count). So code holding cgroup_mutex can safely
896 * assume that if the count is zero, it will stay zero. Similarly, if
897 * a task holds cgroup_mutex on a cgroup with zero count, it
898 * knows that the cgroup won't be removed, as cgroup_rmdir()
901 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
902 * (usually) take cgroup_mutex. These are the two most performance
903 * critical pieces of code here. The exception occurs on cgroup_exit(),
904 * when a task in a notify_on_release cgroup exits. Then cgroup_mutex
905 * is taken, and if the cgroup count is zero, a usermode call made
906 * to the release agent with the name of the cgroup (path relative to
907 * the root of cgroup file system) as the argument.
909 * A cgroup can only be deleted if both its 'count' of using tasks
910 * is zero, and its list of 'children' cgroups is empty. Since all
911 * tasks in the system use _some_ cgroup, and since there is always at
912 * least one task in the system (init, pid == 1), therefore, root cgroup
913 * always has either children cgroups and/or using tasks. So we don't
914 * need a special hack to ensure that root cgroup cannot be deleted.
916 * P.S. One more locking exception. RCU is used to guard the
917 * update of a tasks cgroup pointer by cgroup_attach_task()
920 static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask);
921 static struct kernfs_syscall_ops cgroup_kf_syscall_ops;
922 static const struct file_operations proc_cgroupstats_operations;
924 static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,
927 if (cft->ss && !(cft->flags & CFTYPE_NO_PREFIX) &&
928 !(cgrp->root->flags & CGRP_ROOT_NOPREFIX))
929 snprintf(buf, CGROUP_FILE_NAME_MAX, "%s.%s",
930 cft->ss->name, cft->name);
932 strncpy(buf, cft->name, CGROUP_FILE_NAME_MAX);
937 * cgroup_file_mode - deduce file mode of a control file
938 * @cft: the control file in question
940 * returns cft->mode if ->mode is not 0
941 * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
942 * returns S_IRUGO if it has only a read handler
943 * returns S_IWUSR if it has only a write hander
945 static umode_t cgroup_file_mode(const struct cftype *cft)
952 if (cft->read_u64 || cft->read_s64 || cft->seq_show)
955 if (cft->write_u64 || cft->write_s64 || cft->write_string ||
962 static void cgroup_free_fn(struct work_struct *work)
964 struct cgroup *cgrp = container_of(work, struct cgroup, destroy_work);
966 atomic_dec(&cgrp->root->nr_cgrps);
967 cgroup_pidlist_destroy_all(cgrp);
971 * We get a ref to the parent, and put the ref when this
972 * cgroup is being freed, so it's guaranteed that the
973 * parent won't be destroyed before its children.
975 cgroup_put(cgrp->parent);
976 kernfs_put(cgrp->kn);
980 * This is root cgroup's refcnt reaching zero, which
981 * indicates that the root should be released.
983 cgroup_destroy_root(cgrp->root);
987 static void cgroup_free_rcu(struct rcu_head *head)
989 struct cgroup *cgrp = container_of(head, struct cgroup, rcu_head);
991 INIT_WORK(&cgrp->destroy_work, cgroup_free_fn);
992 queue_work(cgroup_destroy_wq, &cgrp->destroy_work);
995 static void cgroup_get(struct cgroup *cgrp)
997 WARN_ON_ONCE(cgroup_is_dead(cgrp));
998 WARN_ON_ONCE(atomic_read(&cgrp->refcnt) <= 0);
999 atomic_inc(&cgrp->refcnt);
1002 static void cgroup_put(struct cgroup *cgrp)
1004 if (!atomic_dec_and_test(&cgrp->refcnt))
1006 if (WARN_ON_ONCE(cgrp->parent && !cgroup_is_dead(cgrp)))
1010 * XXX: cgrp->id is only used to look up css's. As cgroup and
1011 * css's lifetimes will be decoupled, it should be made
1012 * per-subsystem and moved to css->id so that lookups are
1013 * successful until the target css is released.
1015 mutex_lock(&cgroup_mutex);
1016 idr_remove(&cgrp->root->cgroup_idr, cgrp->id);
1017 mutex_unlock(&cgroup_mutex);
1020 call_rcu(&cgrp->rcu_head, cgroup_free_rcu);
1023 static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
1025 char name[CGROUP_FILE_NAME_MAX];
1027 lockdep_assert_held(&cgroup_tree_mutex);
1028 kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name));
1032 * cgroup_clear_dir - remove subsys files in a cgroup directory
1033 * @cgrp: target cgroup
1034 * @subsys_mask: mask of the subsystem ids whose files should be removed
1036 static void cgroup_clear_dir(struct cgroup *cgrp, unsigned long subsys_mask)
1038 struct cgroup_subsys *ss;
1041 for_each_subsys(ss, i) {
1042 struct cftype *cfts;
1044 if (!test_bit(i, &subsys_mask))
1046 list_for_each_entry(cfts, &ss->cfts, node)
1047 cgroup_addrm_files(cgrp, cfts, false);
1051 static int rebind_subsystems(struct cgroup_root *dst_root,
1052 unsigned long ss_mask)
1054 struct cgroup_subsys *ss;
1057 lockdep_assert_held(&cgroup_tree_mutex);
1058 lockdep_assert_held(&cgroup_mutex);
1060 for_each_subsys(ss, ssid) {
1061 if (!(ss_mask & (1 << ssid)))
1064 /* if @ss has non-root csses attached to it, can't move */
1065 if (css_next_child(NULL, cgroup_css(&ss->root->cgrp, ss)))
1068 /* can't move between two non-dummy roots either */
1069 if (ss->root != &cgrp_dfl_root && dst_root != &cgrp_dfl_root)
1073 ret = cgroup_populate_dir(&dst_root->cgrp, ss_mask);
1075 if (dst_root != &cgrp_dfl_root)
1079 * Rebinding back to the default root is not allowed to
1080 * fail. Using both default and non-default roots should
1081 * be rare. Moving subsystems back and forth even more so.
1082 * Just warn about it and continue.
1084 if (cgrp_dfl_root_visible) {
1085 pr_warning("cgroup: failed to create files (%d) while rebinding 0x%lx to default root\n",
1087 pr_warning("cgroup: you may retry by moving them to a different hierarchy and unbinding\n");
1092 * Nothing can fail from this point on. Remove files for the
1093 * removed subsystems and rebind each subsystem.
1095 mutex_unlock(&cgroup_mutex);
1096 for_each_subsys(ss, ssid)
1097 if (ss_mask & (1 << ssid))
1098 cgroup_clear_dir(&ss->root->cgrp, 1 << ssid);
1099 mutex_lock(&cgroup_mutex);
1101 for_each_subsys(ss, ssid) {
1102 struct cgroup_root *src_root;
1103 struct cgroup_subsys_state *css;
1104 struct css_set *cset;
1106 if (!(ss_mask & (1 << ssid)))
1109 src_root = ss->root;
1110 css = cgroup_css(&src_root->cgrp, ss);
1112 WARN_ON(!css || cgroup_css(&dst_root->cgrp, ss));
1114 RCU_INIT_POINTER(src_root->cgrp.subsys[ssid], NULL);
1115 rcu_assign_pointer(dst_root->cgrp.subsys[ssid], css);
1116 ss->root = dst_root;
1117 css->cgroup = &dst_root->cgrp;
1119 down_write(&css_set_rwsem);
1120 hash_for_each(css_set_table, i, cset, hlist)
1121 list_move_tail(&cset->e_cset_node[ss->id],
1122 &dst_root->cgrp.e_csets[ss->id]);
1123 up_write(&css_set_rwsem);
1125 src_root->subsys_mask &= ~(1 << ssid);
1126 src_root->cgrp.child_subsys_mask &= ~(1 << ssid);
1128 /* default hierarchy doesn't enable controllers by default */
1129 dst_root->subsys_mask |= 1 << ssid;
1130 if (dst_root != &cgrp_dfl_root)
1131 dst_root->cgrp.child_subsys_mask |= 1 << ssid;
1137 kernfs_activate(dst_root->cgrp.kn);
1141 static int cgroup_show_options(struct seq_file *seq,
1142 struct kernfs_root *kf_root)
1144 struct cgroup_root *root = cgroup_root_from_kf(kf_root);
1145 struct cgroup_subsys *ss;
1148 for_each_subsys(ss, ssid)
1149 if (root->subsys_mask & (1 << ssid))
1150 seq_printf(seq, ",%s", ss->name);
1151 if (root->flags & CGRP_ROOT_SANE_BEHAVIOR)
1152 seq_puts(seq, ",sane_behavior");
1153 if (root->flags & CGRP_ROOT_NOPREFIX)
1154 seq_puts(seq, ",noprefix");
1155 if (root->flags & CGRP_ROOT_XATTR)
1156 seq_puts(seq, ",xattr");
1158 spin_lock(&release_agent_path_lock);
1159 if (strlen(root->release_agent_path))
1160 seq_printf(seq, ",release_agent=%s", root->release_agent_path);
1161 spin_unlock(&release_agent_path_lock);
1163 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags))
1164 seq_puts(seq, ",clone_children");
1165 if (strlen(root->name))
1166 seq_printf(seq, ",name=%s", root->name);
1170 struct cgroup_sb_opts {
1171 unsigned long subsys_mask;
1172 unsigned long flags;
1173 char *release_agent;
1174 bool cpuset_clone_children;
1176 /* User explicitly requested empty subsystem */
1181 * Convert a hierarchy specifier into a bitmask of subsystems and
1182 * flags. Call with cgroup_mutex held to protect the cgroup_subsys[]
1183 * array. This function takes refcounts on subsystems to be used, unless it
1184 * returns error, in which case no refcounts are taken.
1186 static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
1188 char *token, *o = data;
1189 bool all_ss = false, one_ss = false;
1190 unsigned long mask = (unsigned long)-1;
1191 struct cgroup_subsys *ss;
1194 BUG_ON(!mutex_is_locked(&cgroup_mutex));
1196 #ifdef CONFIG_CPUSETS
1197 mask = ~(1UL << cpuset_cgrp_id);
1200 memset(opts, 0, sizeof(*opts));
1202 while ((token = strsep(&o, ",")) != NULL) {
1205 if (!strcmp(token, "none")) {
1206 /* Explicitly have no subsystems */
1210 if (!strcmp(token, "all")) {
1211 /* Mutually exclusive option 'all' + subsystem name */
1217 if (!strcmp(token, "__DEVEL__sane_behavior")) {
1218 opts->flags |= CGRP_ROOT_SANE_BEHAVIOR;
1221 if (!strcmp(token, "noprefix")) {
1222 opts->flags |= CGRP_ROOT_NOPREFIX;
1225 if (!strcmp(token, "clone_children")) {
1226 opts->cpuset_clone_children = true;
1229 if (!strcmp(token, "xattr")) {
1230 opts->flags |= CGRP_ROOT_XATTR;
1233 if (!strncmp(token, "release_agent=", 14)) {
1234 /* Specifying two release agents is forbidden */
1235 if (opts->release_agent)
1237 opts->release_agent =
1238 kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
1239 if (!opts->release_agent)
1243 if (!strncmp(token, "name=", 5)) {
1244 const char *name = token + 5;
1245 /* Can't specify an empty name */
1248 /* Must match [\w.-]+ */
1249 for (i = 0; i < strlen(name); i++) {
1253 if ((c == '.') || (c == '-') || (c == '_'))
1257 /* Specifying two names is forbidden */
1260 opts->name = kstrndup(name,
1261 MAX_CGROUP_ROOT_NAMELEN - 1,
1269 for_each_subsys(ss, i) {
1270 if (strcmp(token, ss->name))
1275 /* Mutually exclusive option 'all' + subsystem name */
1278 set_bit(i, &opts->subsys_mask);
1283 if (i == CGROUP_SUBSYS_COUNT)
1287 /* Consistency checks */
1289 if (opts->flags & CGRP_ROOT_SANE_BEHAVIOR) {
1290 pr_warning("cgroup: sane_behavior: this is still under development and its behaviors will change, proceed at your own risk\n");
1292 if ((opts->flags & (CGRP_ROOT_NOPREFIX | CGRP_ROOT_XATTR)) ||
1293 opts->cpuset_clone_children || opts->release_agent ||
1295 pr_err("cgroup: sane_behavior: noprefix, xattr, clone_children, release_agent and name are not allowed\n");
1300 * If the 'all' option was specified select all the
1301 * subsystems, otherwise if 'none', 'name=' and a subsystem
1302 * name options were not specified, let's default to 'all'
1304 if (all_ss || (!one_ss && !opts->none && !opts->name))
1305 for_each_subsys(ss, i)
1307 set_bit(i, &opts->subsys_mask);
1310 * We either have to specify by name or by subsystems. (So
1311 * all empty hierarchies must have a name).
1313 if (!opts->subsys_mask && !opts->name)
1318 * Option noprefix was introduced just for backward compatibility
1319 * with the old cpuset, so we allow noprefix only if mounting just
1320 * the cpuset subsystem.
1322 if ((opts->flags & CGRP_ROOT_NOPREFIX) && (opts->subsys_mask & mask))
1326 /* Can't specify "none" and some subsystems */
1327 if (opts->subsys_mask && opts->none)
1333 static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data)
1336 struct cgroup_root *root = cgroup_root_from_kf(kf_root);
1337 struct cgroup_sb_opts opts;
1338 unsigned long added_mask, removed_mask;
1340 if (root->flags & CGRP_ROOT_SANE_BEHAVIOR) {
1341 pr_err("cgroup: sane_behavior: remount is not allowed\n");
1345 mutex_lock(&cgroup_tree_mutex);
1346 mutex_lock(&cgroup_mutex);
1348 /* See what subsystems are wanted */
1349 ret = parse_cgroupfs_options(data, &opts);
1353 if (opts.subsys_mask != root->subsys_mask || opts.release_agent)
1354 pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
1355 task_tgid_nr(current), current->comm);
1357 added_mask = opts.subsys_mask & ~root->subsys_mask;
1358 removed_mask = root->subsys_mask & ~opts.subsys_mask;
1360 /* Don't allow flags or name to change at remount */
1361 if (((opts.flags ^ root->flags) & CGRP_ROOT_OPTION_MASK) ||
1362 (opts.name && strcmp(opts.name, root->name))) {
1363 pr_err("cgroup: option or name mismatch, new: 0x%lx \"%s\", old: 0x%lx \"%s\"\n",
1364 opts.flags & CGRP_ROOT_OPTION_MASK, opts.name ?: "",
1365 root->flags & CGRP_ROOT_OPTION_MASK, root->name);
1370 /* remounting is not allowed for populated hierarchies */
1371 if (!list_empty(&root->cgrp.children)) {
1376 ret = rebind_subsystems(root, added_mask);
1380 rebind_subsystems(&cgrp_dfl_root, removed_mask);
1382 if (opts.release_agent) {
1383 spin_lock(&release_agent_path_lock);
1384 strcpy(root->release_agent_path, opts.release_agent);
1385 spin_unlock(&release_agent_path_lock);
1388 kfree(opts.release_agent);
1390 mutex_unlock(&cgroup_mutex);
1391 mutex_unlock(&cgroup_tree_mutex);
1396 * To reduce the fork() overhead for systems that are not actually using
1397 * their cgroups capability, we don't maintain the lists running through
1398 * each css_set to its tasks until we see the list actually used - in other
1399 * words after the first mount.
1401 static bool use_task_css_set_links __read_mostly;
1403 static void cgroup_enable_task_cg_lists(void)
1405 struct task_struct *p, *g;
1407 down_write(&css_set_rwsem);
1409 if (use_task_css_set_links)
1412 use_task_css_set_links = true;
1415 * We need tasklist_lock because RCU is not safe against
1416 * while_each_thread(). Besides, a forking task that has passed
1417 * cgroup_post_fork() without seeing use_task_css_set_links = 1
1418 * is not guaranteed to have its child immediately visible in the
1419 * tasklist if we walk through it with RCU.
1421 read_lock(&tasklist_lock);
1422 do_each_thread(g, p) {
1423 WARN_ON_ONCE(!list_empty(&p->cg_list) ||
1424 task_css_set(p) != &init_css_set);
1427 * We should check if the process is exiting, otherwise
1428 * it will race with cgroup_exit() in that the list
1429 * entry won't be deleted though the process has exited.
1430 * Do it while holding siglock so that we don't end up
1431 * racing against cgroup_exit().
1433 spin_lock_irq(&p->sighand->siglock);
1434 if (!(p->flags & PF_EXITING)) {
1435 struct css_set *cset = task_css_set(p);
1437 list_add(&p->cg_list, &cset->tasks);
1440 spin_unlock_irq(&p->sighand->siglock);
1441 } while_each_thread(g, p);
1442 read_unlock(&tasklist_lock);
1444 up_write(&css_set_rwsem);
1447 static void init_cgroup_housekeeping(struct cgroup *cgrp)
1449 struct cgroup_subsys *ss;
1452 atomic_set(&cgrp->refcnt, 1);
1453 INIT_LIST_HEAD(&cgrp->sibling);
1454 INIT_LIST_HEAD(&cgrp->children);
1455 INIT_LIST_HEAD(&cgrp->cset_links);
1456 INIT_LIST_HEAD(&cgrp->release_list);
1457 INIT_LIST_HEAD(&cgrp->pidlists);
1458 mutex_init(&cgrp->pidlist_mutex);
1459 cgrp->dummy_css.cgroup = cgrp;
1461 for_each_subsys(ss, ssid)
1462 INIT_LIST_HEAD(&cgrp->e_csets[ssid]);
1464 init_waitqueue_head(&cgrp->offline_waitq);
1467 static void init_cgroup_root(struct cgroup_root *root,
1468 struct cgroup_sb_opts *opts)
1470 struct cgroup *cgrp = &root->cgrp;
1472 INIT_LIST_HEAD(&root->root_list);
1473 atomic_set(&root->nr_cgrps, 1);
1475 init_cgroup_housekeeping(cgrp);
1476 idr_init(&root->cgroup_idr);
1478 root->flags = opts->flags;
1479 if (opts->release_agent)
1480 strcpy(root->release_agent_path, opts->release_agent);
1482 strcpy(root->name, opts->name);
1483 if (opts->cpuset_clone_children)
1484 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags);
1487 static int cgroup_setup_root(struct cgroup_root *root, unsigned long ss_mask)
1489 LIST_HEAD(tmp_links);
1490 struct cgroup *root_cgrp = &root->cgrp;
1491 struct css_set *cset;
1494 lockdep_assert_held(&cgroup_tree_mutex);
1495 lockdep_assert_held(&cgroup_mutex);
1497 ret = idr_alloc(&root->cgroup_idr, root_cgrp, 0, 1, GFP_KERNEL);
1500 root_cgrp->id = ret;
1503 * We're accessing css_set_count without locking css_set_rwsem here,
1504 * but that's OK - it can only be increased by someone holding
1505 * cgroup_lock, and that's us. The worst that can happen is that we
1506 * have some link structures left over
1508 ret = allocate_cgrp_cset_links(css_set_count, &tmp_links);
1512 ret = cgroup_init_root_id(root);
1516 root->kf_root = kernfs_create_root(&cgroup_kf_syscall_ops,
1517 KERNFS_ROOT_CREATE_DEACTIVATED,
1519 if (IS_ERR(root->kf_root)) {
1520 ret = PTR_ERR(root->kf_root);
1523 root_cgrp->kn = root->kf_root->kn;
1525 ret = cgroup_addrm_files(root_cgrp, cgroup_base_files, true);
1529 ret = rebind_subsystems(root, ss_mask);
1534 * There must be no failure case after here, since rebinding takes
1535 * care of subsystems' refcounts, which are explicitly dropped in
1536 * the failure exit path.
1538 list_add(&root->root_list, &cgroup_roots);
1539 cgroup_root_count++;
1542 * Link the root cgroup in this hierarchy into all the css_set
1545 down_write(&css_set_rwsem);
1546 hash_for_each(css_set_table, i, cset, hlist)
1547 link_css_set(&tmp_links, cset, root_cgrp);
1548 up_write(&css_set_rwsem);
1550 BUG_ON(!list_empty(&root_cgrp->children));
1551 BUG_ON(atomic_read(&root->nr_cgrps) != 1);
1553 kernfs_activate(root_cgrp->kn);
1558 kernfs_destroy_root(root->kf_root);
1559 root->kf_root = NULL;
1561 cgroup_exit_root_id(root);
1563 free_cgrp_cset_links(&tmp_links);
1567 static struct dentry *cgroup_mount(struct file_system_type *fs_type,
1568 int flags, const char *unused_dev_name,
1571 struct cgroup_root *root;
1572 struct cgroup_sb_opts opts;
1573 struct dentry *dentry;
1578 * The first time anyone tries to mount a cgroup, enable the list
1579 * linking each css_set to its tasks and fix up all existing tasks.
1581 if (!use_task_css_set_links)
1582 cgroup_enable_task_cg_lists();
1584 mutex_lock(&cgroup_tree_mutex);
1585 mutex_lock(&cgroup_mutex);
1587 /* First find the desired set of subsystems */
1588 ret = parse_cgroupfs_options(data, &opts);
1592 /* look for a matching existing root */
1593 if (!opts.subsys_mask && !opts.none && !opts.name) {
1594 cgrp_dfl_root_visible = true;
1595 root = &cgrp_dfl_root;
1596 cgroup_get(&root->cgrp);
1601 for_each_root(root) {
1602 bool name_match = false;
1604 if (root == &cgrp_dfl_root)
1608 * If we asked for a name then it must match. Also, if
1609 * name matches but sybsys_mask doesn't, we should fail.
1610 * Remember whether name matched.
1613 if (strcmp(opts.name, root->name))
1619 * If we asked for subsystems (or explicitly for no
1620 * subsystems) then they must match.
1622 if ((opts.subsys_mask || opts.none) &&
1623 (opts.subsys_mask != root->subsys_mask)) {
1630 if ((root->flags ^ opts.flags) & CGRP_ROOT_OPTION_MASK) {
1631 if ((root->flags | opts.flags) & CGRP_ROOT_SANE_BEHAVIOR) {
1632 pr_err("cgroup: sane_behavior: new mount options should match the existing superblock\n");
1636 pr_warning("cgroup: new mount options do not match the existing superblock, will be ignored\n");
1641 * A root's lifetime is governed by its root cgroup. Zero
1642 * ref indicate that the root is being destroyed. Wait for
1643 * destruction to complete so that the subsystems are free.
1644 * We can use wait_queue for the wait but this path is
1645 * super cold. Let's just sleep for a bit and retry.
1647 if (!atomic_inc_not_zero(&root->cgrp.refcnt)) {
1648 mutex_unlock(&cgroup_mutex);
1649 mutex_unlock(&cgroup_tree_mutex);
1651 mutex_lock(&cgroup_tree_mutex);
1652 mutex_lock(&cgroup_mutex);
1661 * No such thing, create a new one. name= matching without subsys
1662 * specification is allowed for already existing hierarchies but we
1663 * can't create new one without subsys specification.
1665 if (!opts.subsys_mask && !opts.none) {
1670 root = kzalloc(sizeof(*root), GFP_KERNEL);
1676 init_cgroup_root(root, &opts);
1678 ret = cgroup_setup_root(root, opts.subsys_mask);
1680 cgroup_free_root(root);
1683 mutex_unlock(&cgroup_mutex);
1684 mutex_unlock(&cgroup_tree_mutex);
1686 kfree(opts.release_agent);
1690 return ERR_PTR(ret);
1692 dentry = kernfs_mount(fs_type, flags, root->kf_root, &new_sb);
1693 if (IS_ERR(dentry) || !new_sb)
1694 cgroup_put(&root->cgrp);
1698 static void cgroup_kill_sb(struct super_block *sb)
1700 struct kernfs_root *kf_root = kernfs_root_from_sb(sb);
1701 struct cgroup_root *root = cgroup_root_from_kf(kf_root);
1703 cgroup_put(&root->cgrp);
1707 static struct file_system_type cgroup_fs_type = {
1709 .mount = cgroup_mount,
1710 .kill_sb = cgroup_kill_sb,
1713 static struct kobject *cgroup_kobj;
1716 * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
1717 * @task: target task
1718 * @buf: the buffer to write the path into
1719 * @buflen: the length of the buffer
1721 * Determine @task's cgroup on the first (the one with the lowest non-zero
1722 * hierarchy_id) cgroup hierarchy and copy its path into @buf. This
1723 * function grabs cgroup_mutex and shouldn't be used inside locks used by
1724 * cgroup controller callbacks.
1726 * Return value is the same as kernfs_path().
1728 char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
1730 struct cgroup_root *root;
1731 struct cgroup *cgrp;
1732 int hierarchy_id = 1;
1735 mutex_lock(&cgroup_mutex);
1736 down_read(&css_set_rwsem);
1738 root = idr_get_next(&cgroup_hierarchy_idr, &hierarchy_id);
1741 cgrp = task_cgroup_from_root(task, root);
1742 path = cgroup_path(cgrp, buf, buflen);
1744 /* if no hierarchy exists, everyone is in "/" */
1745 if (strlcpy(buf, "/", buflen) < buflen)
1749 up_read(&css_set_rwsem);
1750 mutex_unlock(&cgroup_mutex);
1753 EXPORT_SYMBOL_GPL(task_cgroup_path);
1755 /* used to track tasks and other necessary states during migration */
1756 struct cgroup_taskset {
1757 /* the src and dst cset list running through cset->mg_node */
1758 struct list_head src_csets;
1759 struct list_head dst_csets;
1762 * Fields for cgroup_taskset_*() iteration.
1764 * Before migration is committed, the target migration tasks are on
1765 * ->mg_tasks of the csets on ->src_csets. After, on ->mg_tasks of
1766 * the csets on ->dst_csets. ->csets point to either ->src_csets
1767 * or ->dst_csets depending on whether migration is committed.
1769 * ->cur_csets and ->cur_task point to the current task position
1772 struct list_head *csets;
1773 struct css_set *cur_cset;
1774 struct task_struct *cur_task;
1778 * cgroup_taskset_first - reset taskset and return the first task
1779 * @tset: taskset of interest
1781 * @tset iteration is initialized and the first task is returned.
1783 struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset)
1785 tset->cur_cset = list_first_entry(tset->csets, struct css_set, mg_node);
1786 tset->cur_task = NULL;
1788 return cgroup_taskset_next(tset);
1792 * cgroup_taskset_next - iterate to the next task in taskset
1793 * @tset: taskset of interest
1795 * Return the next task in @tset. Iteration must have been initialized
1796 * with cgroup_taskset_first().
1798 struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset)
1800 struct css_set *cset = tset->cur_cset;
1801 struct task_struct *task = tset->cur_task;
1803 while (&cset->mg_node != tset->csets) {
1805 task = list_first_entry(&cset->mg_tasks,
1806 struct task_struct, cg_list);
1808 task = list_next_entry(task, cg_list);
1810 if (&task->cg_list != &cset->mg_tasks) {
1811 tset->cur_cset = cset;
1812 tset->cur_task = task;
1816 cset = list_next_entry(cset, mg_node);
1824 * cgroup_task_migrate - move a task from one cgroup to another.
1825 * @old_cgrp; the cgroup @tsk is being migrated from
1826 * @tsk: the task being migrated
1827 * @new_cset: the new css_set @tsk is being attached to
1829 * Must be called with cgroup_mutex, threadgroup and css_set_rwsem locked.
1831 static void cgroup_task_migrate(struct cgroup *old_cgrp,
1832 struct task_struct *tsk,
1833 struct css_set *new_cset)
1835 struct css_set *old_cset;
1837 lockdep_assert_held(&cgroup_mutex);
1838 lockdep_assert_held(&css_set_rwsem);
1841 * We are synchronized through threadgroup_lock() against PF_EXITING
1842 * setting such that we can't race against cgroup_exit() changing the
1843 * css_set to init_css_set and dropping the old one.
1845 WARN_ON_ONCE(tsk->flags & PF_EXITING);
1846 old_cset = task_css_set(tsk);
1848 get_css_set(new_cset);
1849 rcu_assign_pointer(tsk->cgroups, new_cset);
1852 * Use move_tail so that cgroup_taskset_first() still returns the
1853 * leader after migration. This works because cgroup_migrate()
1854 * ensures that the dst_cset of the leader is the first on the
1855 * tset's dst_csets list.
1857 list_move_tail(&tsk->cg_list, &new_cset->mg_tasks);
1860 * We just gained a reference on old_cset by taking it from the
1861 * task. As trading it for new_cset is protected by cgroup_mutex,
1862 * we're safe to drop it here; it will be freed under RCU.
1864 set_bit(CGRP_RELEASABLE, &old_cgrp->flags);
1865 put_css_set_locked(old_cset, false);
1869 * cgroup_migrate_finish - cleanup after attach
1870 * @preloaded_csets: list of preloaded css_sets
1872 * Undo cgroup_migrate_add_src() and cgroup_migrate_prepare_dst(). See
1873 * those functions for details.
1875 static void cgroup_migrate_finish(struct list_head *preloaded_csets)
1877 struct css_set *cset, *tmp_cset;
1879 lockdep_assert_held(&cgroup_mutex);
1881 down_write(&css_set_rwsem);
1882 list_for_each_entry_safe(cset, tmp_cset, preloaded_csets, mg_preload_node) {
1883 cset->mg_src_cgrp = NULL;
1884 cset->mg_dst_cset = NULL;
1885 list_del_init(&cset->mg_preload_node);
1886 put_css_set_locked(cset, false);
1888 up_write(&css_set_rwsem);
1892 * cgroup_migrate_add_src - add a migration source css_set
1893 * @src_cset: the source css_set to add
1894 * @dst_cgrp: the destination cgroup
1895 * @preloaded_csets: list of preloaded css_sets
1897 * Tasks belonging to @src_cset are about to be migrated to @dst_cgrp. Pin
1898 * @src_cset and add it to @preloaded_csets, which should later be cleaned
1899 * up by cgroup_migrate_finish().
1901 * This function may be called without holding threadgroup_lock even if the
1902 * target is a process. Threads may be created and destroyed but as long
1903 * as cgroup_mutex is not dropped, no new css_set can be put into play and
1904 * the preloaded css_sets are guaranteed to cover all migrations.
1906 static void cgroup_migrate_add_src(struct css_set *src_cset,
1907 struct cgroup *dst_cgrp,
1908 struct list_head *preloaded_csets)
1910 struct cgroup *src_cgrp;
1912 lockdep_assert_held(&cgroup_mutex);
1913 lockdep_assert_held(&css_set_rwsem);
1915 src_cgrp = cset_cgroup_from_root(src_cset, dst_cgrp->root);
1917 if (!list_empty(&src_cset->mg_preload_node))
1920 WARN_ON(src_cset->mg_src_cgrp);
1921 WARN_ON(!list_empty(&src_cset->mg_tasks));
1922 WARN_ON(!list_empty(&src_cset->mg_node));
1924 src_cset->mg_src_cgrp = src_cgrp;
1925 get_css_set(src_cset);
1926 list_add(&src_cset->mg_preload_node, preloaded_csets);
1930 * cgroup_migrate_prepare_dst - prepare destination css_sets for migration
1931 * @dst_cgrp: the destination cgroup (may be %NULL)
1932 * @preloaded_csets: list of preloaded source css_sets
1934 * Tasks are about to be moved to @dst_cgrp and all the source css_sets
1935 * have been preloaded to @preloaded_csets. This function looks up and
1936 * pins all destination css_sets, links each to its source, and append them
1937 * to @preloaded_csets. If @dst_cgrp is %NULL, the destination of each
1938 * source css_set is assumed to be its cgroup on the default hierarchy.
1940 * This function must be called after cgroup_migrate_add_src() has been
1941 * called on each migration source css_set. After migration is performed
1942 * using cgroup_migrate(), cgroup_migrate_finish() must be called on
1945 static int cgroup_migrate_prepare_dst(struct cgroup *dst_cgrp,
1946 struct list_head *preloaded_csets)
1949 struct css_set *src_cset, *tmp_cset;
1951 lockdep_assert_held(&cgroup_mutex);
1954 * Except for the root, child_subsys_mask must be zero for a cgroup
1955 * with tasks so that child cgroups don't compete against tasks.
1957 if (dst_cgrp && cgroup_on_dfl(dst_cgrp) && dst_cgrp->parent &&
1958 dst_cgrp->child_subsys_mask)
1961 /* look up the dst cset for each src cset and link it to src */
1962 list_for_each_entry_safe(src_cset, tmp_cset, preloaded_csets, mg_preload_node) {
1963 struct css_set *dst_cset;
1965 dst_cset = find_css_set(src_cset,
1966 dst_cgrp ?: src_cset->dfl_cgrp);
1970 WARN_ON_ONCE(src_cset->mg_dst_cset || dst_cset->mg_dst_cset);
1973 * If src cset equals dst, it's noop. Drop the src.
1974 * cgroup_migrate() will skip the cset too. Note that we
1975 * can't handle src == dst as some nodes are used by both.
1977 if (src_cset == dst_cset) {
1978 src_cset->mg_src_cgrp = NULL;
1979 list_del_init(&src_cset->mg_preload_node);
1980 put_css_set(src_cset, false);
1981 put_css_set(dst_cset, false);
1985 src_cset->mg_dst_cset = dst_cset;
1987 if (list_empty(&dst_cset->mg_preload_node))
1988 list_add(&dst_cset->mg_preload_node, &csets);
1990 put_css_set(dst_cset, false);
1993 list_splice_tail(&csets, preloaded_csets);
1996 cgroup_migrate_finish(&csets);
2001 * cgroup_migrate - migrate a process or task to a cgroup
2002 * @cgrp: the destination cgroup
2003 * @leader: the leader of the process or the task to migrate
2004 * @threadgroup: whether @leader points to the whole process or a single task
2006 * Migrate a process or task denoted by @leader to @cgrp. If migrating a
2007 * process, the caller must be holding threadgroup_lock of @leader. The
2008 * caller is also responsible for invoking cgroup_migrate_add_src() and
2009 * cgroup_migrate_prepare_dst() on the targets before invoking this
2010 * function and following up with cgroup_migrate_finish().
2012 * As long as a controller's ->can_attach() doesn't fail, this function is
2013 * guaranteed to succeed. This means that, excluding ->can_attach()
2014 * failure, when migrating multiple targets, the success or failure can be
2015 * decided for all targets by invoking group_migrate_prepare_dst() before
2016 * actually starting migrating.
2018 static int cgroup_migrate(struct cgroup *cgrp, struct task_struct *leader,
2021 struct cgroup_taskset tset = {
2022 .src_csets = LIST_HEAD_INIT(tset.src_csets),
2023 .dst_csets = LIST_HEAD_INIT(tset.dst_csets),
2024 .csets = &tset.src_csets,
2026 struct cgroup_subsys_state *css, *failed_css = NULL;
2027 struct css_set *cset, *tmp_cset;
2028 struct task_struct *task, *tmp_task;
2032 * Prevent freeing of tasks while we take a snapshot. Tasks that are
2033 * already PF_EXITING could be freed from underneath us unless we
2034 * take an rcu_read_lock.
2036 down_write(&css_set_rwsem);
2040 /* @task either already exited or can't exit until the end */
2041 if (task->flags & PF_EXITING)
2044 /* leave @task alone if post_fork() hasn't linked it yet */
2045 if (list_empty(&task->cg_list))
2048 cset = task_css_set(task);
2049 if (!cset->mg_src_cgrp)
2053 * cgroup_taskset_first() must always return the leader.
2054 * Take care to avoid disturbing the ordering.
2056 list_move_tail(&task->cg_list, &cset->mg_tasks);
2057 if (list_empty(&cset->mg_node))
2058 list_add_tail(&cset->mg_node, &tset.src_csets);
2059 if (list_empty(&cset->mg_dst_cset->mg_node))
2060 list_move_tail(&cset->mg_dst_cset->mg_node,
2065 } while_each_thread(leader, task);
2067 up_write(&css_set_rwsem);
2069 /* methods shouldn't be called if no task is actually migrating */
2070 if (list_empty(&tset.src_csets))
2073 /* check that we can legitimately attach to the cgroup */
2074 for_each_e_css(css, i, cgrp) {
2075 if (css->ss->can_attach) {
2076 ret = css->ss->can_attach(css, &tset);
2079 goto out_cancel_attach;
2085 * Now that we're guaranteed success, proceed to move all tasks to
2086 * the new cgroup. There are no failure cases after here, so this
2087 * is the commit point.
2089 down_write(&css_set_rwsem);
2090 list_for_each_entry(cset, &tset.src_csets, mg_node) {
2091 list_for_each_entry_safe(task, tmp_task, &cset->mg_tasks, cg_list)
2092 cgroup_task_migrate(cset->mg_src_cgrp, task,
2095 up_write(&css_set_rwsem);
2098 * Migration is committed, all target tasks are now on dst_csets.
2099 * Nothing is sensitive to fork() after this point. Notify
2100 * controllers that migration is complete.
2102 tset.csets = &tset.dst_csets;
2104 for_each_e_css(css, i, cgrp)
2105 if (css->ss->attach)
2106 css->ss->attach(css, &tset);
2109 goto out_release_tset;
2112 for_each_e_css(css, i, cgrp) {
2113 if (css == failed_css)
2115 if (css->ss->cancel_attach)
2116 css->ss->cancel_attach(css, &tset);
2119 down_write(&css_set_rwsem);
2120 list_splice_init(&tset.dst_csets, &tset.src_csets);
2121 list_for_each_entry_safe(cset, tmp_cset, &tset.src_csets, mg_node) {
2122 list_splice_tail_init(&cset->mg_tasks, &cset->tasks);
2123 list_del_init(&cset->mg_node);
2125 up_write(&css_set_rwsem);
2130 * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
2131 * @dst_cgrp: the cgroup to attach to
2132 * @leader: the task or the leader of the threadgroup to be attached
2133 * @threadgroup: attach the whole threadgroup?
2135 * Call holding cgroup_mutex and threadgroup_lock of @leader.
2137 static int cgroup_attach_task(struct cgroup *dst_cgrp,
2138 struct task_struct *leader, bool threadgroup)
2140 LIST_HEAD(preloaded_csets);
2141 struct task_struct *task;
2144 /* look up all src csets */
2145 down_read(&css_set_rwsem);
2149 cgroup_migrate_add_src(task_css_set(task), dst_cgrp,
2153 } while_each_thread(leader, task);
2155 up_read(&css_set_rwsem);
2157 /* prepare dst csets and commit */
2158 ret = cgroup_migrate_prepare_dst(dst_cgrp, &preloaded_csets);
2160 ret = cgroup_migrate(dst_cgrp, leader, threadgroup);
2162 cgroup_migrate_finish(&preloaded_csets);
2167 * Find the task_struct of the task to attach by vpid and pass it along to the
2168 * function to attach either it or all tasks in its threadgroup. Will lock
2169 * cgroup_mutex and threadgroup.
2171 static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
2173 struct task_struct *tsk;
2174 const struct cred *cred = current_cred(), *tcred;
2177 if (!cgroup_lock_live_group(cgrp))
2183 tsk = find_task_by_vpid(pid);
2187 goto out_unlock_cgroup;
2190 * even if we're attaching all tasks in the thread group, we
2191 * only need to check permissions on one of them.
2193 tcred = __task_cred(tsk);
2194 if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
2195 !uid_eq(cred->euid, tcred->uid) &&
2196 !uid_eq(cred->euid, tcred->suid)) {
2199 goto out_unlock_cgroup;
2205 tsk = tsk->group_leader;
2208 * Workqueue threads may acquire PF_NO_SETAFFINITY and become
2209 * trapped in a cpuset, or RT worker may be born in a cgroup
2210 * with no rt_runtime allocated. Just say no.
2212 if (tsk == kthreadd_task || (tsk->flags & PF_NO_SETAFFINITY)) {
2215 goto out_unlock_cgroup;
2218 get_task_struct(tsk);
2221 threadgroup_lock(tsk);
2223 if (!thread_group_leader(tsk)) {
2225 * a race with de_thread from another thread's exec()
2226 * may strip us of our leadership, if this happens,
2227 * there is no choice but to throw this task away and
2228 * try again; this is
2229 * "double-double-toil-and-trouble-check locking".
2231 threadgroup_unlock(tsk);
2232 put_task_struct(tsk);
2233 goto retry_find_task;
2237 ret = cgroup_attach_task(cgrp, tsk, threadgroup);
2239 threadgroup_unlock(tsk);
2241 put_task_struct(tsk);
2243 mutex_unlock(&cgroup_mutex);
2248 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
2249 * @from: attach to all cgroups of a given task
2250 * @tsk: the task to be attached
2252 int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
2254 struct cgroup_root *root;
2257 mutex_lock(&cgroup_mutex);
2258 for_each_root(root) {
2259 struct cgroup *from_cgrp;
2261 if (root == &cgrp_dfl_root)
2264 down_read(&css_set_rwsem);
2265 from_cgrp = task_cgroup_from_root(from, root);
2266 up_read(&css_set_rwsem);
2268 retval = cgroup_attach_task(from_cgrp, tsk, false);
2272 mutex_unlock(&cgroup_mutex);
2276 EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
2278 static int cgroup_tasks_write(struct cgroup_subsys_state *css,
2279 struct cftype *cft, u64 pid)
2281 return attach_task_by_pid(css->cgroup, pid, false);
2284 static int cgroup_procs_write(struct cgroup_subsys_state *css,
2285 struct cftype *cft, u64 tgid)
2287 return attach_task_by_pid(css->cgroup, tgid, true);
2290 static int cgroup_release_agent_write(struct cgroup_subsys_state *css,
2291 struct cftype *cft, char *buffer)
2293 struct cgroup_root *root = css->cgroup->root;
2295 BUILD_BUG_ON(sizeof(root->release_agent_path) < PATH_MAX);
2296 if (!cgroup_lock_live_group(css->cgroup))
2298 spin_lock(&release_agent_path_lock);
2299 strlcpy(root->release_agent_path, buffer,
2300 sizeof(root->release_agent_path));
2301 spin_unlock(&release_agent_path_lock);
2302 mutex_unlock(&cgroup_mutex);
2306 static int cgroup_release_agent_show(struct seq_file *seq, void *v)
2308 struct cgroup *cgrp = seq_css(seq)->cgroup;
2310 if (!cgroup_lock_live_group(cgrp))
2312 seq_puts(seq, cgrp->root->release_agent_path);
2313 seq_putc(seq, '\n');
2314 mutex_unlock(&cgroup_mutex);
2318 static int cgroup_sane_behavior_show(struct seq_file *seq, void *v)
2320 struct cgroup *cgrp = seq_css(seq)->cgroup;
2322 seq_printf(seq, "%d\n", cgroup_sane_behavior(cgrp));
2326 static void cgroup_print_ss_mask(struct seq_file *seq, unsigned int ss_mask)
2328 struct cgroup_subsys *ss;
2329 bool printed = false;
2332 for_each_subsys(ss, ssid) {
2333 if (ss_mask & (1 << ssid)) {
2336 seq_printf(seq, "%s", ss->name);
2341 seq_putc(seq, '\n');
2344 /* show controllers which are currently attached to the default hierarchy */
2345 static int cgroup_root_controllers_show(struct seq_file *seq, void *v)
2347 struct cgroup *cgrp = seq_css(seq)->cgroup;
2349 cgroup_print_ss_mask(seq, cgrp->root->subsys_mask);
2353 /* show controllers which are enabled from the parent */
2354 static int cgroup_controllers_show(struct seq_file *seq, void *v)
2356 struct cgroup *cgrp = seq_css(seq)->cgroup;
2358 cgroup_print_ss_mask(seq, cgrp->parent->child_subsys_mask);
2362 /* show controllers which are enabled for a given cgroup's children */
2363 static int cgroup_subtree_control_show(struct seq_file *seq, void *v)
2365 struct cgroup *cgrp = seq_css(seq)->cgroup;
2367 cgroup_print_ss_mask(seq, cgrp->child_subsys_mask);
2372 * cgroup_update_dfl_csses - update css assoc of a subtree in default hierarchy
2373 * @cgrp: root of the subtree to update csses for
2375 * @cgrp's child_subsys_mask has changed and its subtree's (self excluded)
2376 * css associations need to be updated accordingly. This function looks up
2377 * all css_sets which are attached to the subtree, creates the matching
2378 * updated css_sets and migrates the tasks to the new ones.
2380 static int cgroup_update_dfl_csses(struct cgroup *cgrp)
2382 LIST_HEAD(preloaded_csets);
2383 struct cgroup_subsys_state *css;
2384 struct css_set *src_cset;
2387 lockdep_assert_held(&cgroup_tree_mutex);
2388 lockdep_assert_held(&cgroup_mutex);
2390 /* look up all csses currently attached to @cgrp's subtree */
2391 down_read(&css_set_rwsem);
2392 css_for_each_descendant_pre(css, cgroup_css(cgrp, NULL)) {
2393 struct cgrp_cset_link *link;
2395 /* self is not affected by child_subsys_mask change */
2396 if (css->cgroup == cgrp)
2399 list_for_each_entry(link, &css->cgroup->cset_links, cset_link)
2400 cgroup_migrate_add_src(link->cset, cgrp,
2403 up_read(&css_set_rwsem);
2405 /* NULL dst indicates self on default hierarchy */
2406 ret = cgroup_migrate_prepare_dst(NULL, &preloaded_csets);
2410 list_for_each_entry(src_cset, &preloaded_csets, mg_preload_node) {
2411 struct task_struct *last_task = NULL, *task;
2413 /* src_csets precede dst_csets, break on the first dst_cset */
2414 if (!src_cset->mg_src_cgrp)
2418 * All tasks in src_cset need to be migrated to the
2419 * matching dst_cset. Empty it process by process. We
2420 * walk tasks but migrate processes. The leader might even
2421 * belong to a different cset but such src_cset would also
2422 * be among the target src_csets because the default
2423 * hierarchy enforces per-process membership.
2426 down_read(&css_set_rwsem);
2427 task = list_first_entry_or_null(&src_cset->tasks,
2428 struct task_struct, cg_list);
2430 task = task->group_leader;
2431 WARN_ON_ONCE(!task_css_set(task)->mg_src_cgrp);
2432 get_task_struct(task);
2434 up_read(&css_set_rwsem);
2439 /* guard against possible infinite loop */
2440 if (WARN(last_task == task,
2441 "cgroup: update_dfl_csses failed to make progress, aborting in inconsistent state\n"))
2445 threadgroup_lock(task);
2446 /* raced against de_thread() from another thread? */
2447 if (!thread_group_leader(task)) {
2448 threadgroup_unlock(task);
2449 put_task_struct(task);
2453 ret = cgroup_migrate(src_cset->dfl_cgrp, task, true);
2455 threadgroup_unlock(task);
2456 put_task_struct(task);
2458 if (WARN(ret, "cgroup: failed to update controllers for the default hierarchy (%d), further operations may crash or hang\n", ret))
2464 cgroup_migrate_finish(&preloaded_csets);
2468 /* change the enabled child controllers for a cgroup in the default hierarchy */
2469 static int cgroup_subtree_control_write(struct cgroup_subsys_state *dummy_css,
2470 struct cftype *cft, char *buffer)
2472 unsigned long enable_req = 0, disable_req = 0, enable, disable;
2473 struct cgroup *cgrp = dummy_css->cgroup, *child;
2474 struct cgroup_subsys *ss;
2479 * Parse input - white space separated list of subsystem names
2480 * prefixed with either + or -.
2483 while ((tok = strsep(&p, " \t\n"))) {
2484 for_each_subsys(ss, ssid) {
2485 if (ss->disabled || strcmp(tok + 1, ss->name))
2489 enable_req |= 1 << ssid;
2490 disable_req &= ~(1 << ssid);
2491 } else if (*tok == '-') {
2492 disable_req |= 1 << ssid;
2493 enable_req &= ~(1 << ssid);
2499 if (ssid == CGROUP_SUBSYS_COUNT)
2504 * We're gonna grab cgroup_tree_mutex which nests outside kernfs
2505 * active_ref. cgroup_lock_live_group() already provides enough
2506 * protection. Ensure @cgrp stays accessible and break the
2507 * active_ref protection.
2510 kernfs_break_active_protection(cgrp->control_kn);
2512 enable = enable_req;
2513 disable = disable_req;
2515 mutex_lock(&cgroup_tree_mutex);
2517 for_each_subsys(ss, ssid) {
2518 if (enable & (1 << ssid)) {
2519 if (cgrp->child_subsys_mask & (1 << ssid)) {
2520 enable &= ~(1 << ssid);
2525 * Because css offlining is asynchronous, userland
2526 * might try to re-enable the same controller while
2527 * the previous instance is still around. In such
2528 * cases, wait till it's gone using offline_waitq.
2530 cgroup_for_each_live_child(child, cgrp) {
2533 if (!cgroup_css(child, ss))
2536 prepare_to_wait(&child->offline_waitq, &wait,
2537 TASK_UNINTERRUPTIBLE);
2538 mutex_unlock(&cgroup_tree_mutex);
2540 finish_wait(&child->offline_waitq, &wait);
2544 /* unavailable or not enabled on the parent? */
2545 if (!(cgrp_dfl_root.subsys_mask & (1 << ssid)) ||
2547 !(cgrp->parent->child_subsys_mask & (1 << ssid)))) {
2549 goto out_unlock_tree;
2551 } else if (disable & (1 << ssid)) {
2552 if (!(cgrp->child_subsys_mask & (1 << ssid))) {
2553 disable &= ~(1 << ssid);
2557 /* a child has it enabled? */
2558 cgroup_for_each_live_child(child, cgrp) {
2559 if (child->child_subsys_mask & (1 << ssid)) {
2561 goto out_unlock_tree;
2567 if (!enable && !disable) {
2569 goto out_unlock_tree;
2572 if (!cgroup_lock_live_group(cgrp)) {
2574 goto out_unlock_tree;
2578 * Except for the root, child_subsys_mask must be zero for a cgroup
2579 * with tasks so that child cgroups don't compete against tasks.
2581 if (enable && cgrp->parent && !list_empty(&cgrp->cset_links)) {
2587 * Create csses for enables and update child_subsys_mask. This
2588 * changes cgroup_e_css() results which in turn makes the
2589 * subsequent cgroup_update_dfl_csses() associate all tasks in the
2590 * subtree to the updated csses.
2592 for_each_subsys(ss, ssid) {
2593 if (!(enable & (1 << ssid)))
2596 cgroup_for_each_live_child(child, cgrp) {
2597 ret = create_css(child, ss);
2603 cgrp->child_subsys_mask |= enable;
2604 cgrp->child_subsys_mask &= ~disable;
2606 ret = cgroup_update_dfl_csses(cgrp);
2610 /* all tasks are now migrated away from the old csses, kill them */
2611 for_each_subsys(ss, ssid) {
2612 if (!(disable & (1 << ssid)))
2615 cgroup_for_each_live_child(child, cgrp)
2616 kill_css(cgroup_css(child, ss));
2619 kernfs_activate(cgrp->kn);
2622 mutex_unlock(&cgroup_mutex);
2624 mutex_unlock(&cgroup_tree_mutex);
2625 kernfs_unbreak_active_protection(cgrp->control_kn);
2630 cgrp->child_subsys_mask &= ~enable;
2631 cgrp->child_subsys_mask |= disable;
2633 for_each_subsys(ss, ssid) {
2634 if (!(enable & (1 << ssid)))
2637 cgroup_for_each_live_child(child, cgrp) {
2638 struct cgroup_subsys_state *css = cgroup_css(child, ss);
2646 static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf,
2647 size_t nbytes, loff_t off)
2649 struct cgroup *cgrp = of->kn->parent->priv;
2650 struct cftype *cft = of->kn->priv;
2651 struct cgroup_subsys_state *css;
2655 * kernfs guarantees that a file isn't deleted with operations in
2656 * flight, which means that the matching css is and stays alive and
2657 * doesn't need to be pinned. The RCU locking is not necessary
2658 * either. It's just for the convenience of using cgroup_css().
2661 css = cgroup_css(cgrp, cft->ss);
2664 if (cft->write_string) {
2665 ret = cft->write_string(css, cft, strstrip(buf));
2666 } else if (cft->write_u64) {
2667 unsigned long long v;
2668 ret = kstrtoull(buf, 0, &v);
2670 ret = cft->write_u64(css, cft, v);
2671 } else if (cft->write_s64) {
2673 ret = kstrtoll(buf, 0, &v);
2675 ret = cft->write_s64(css, cft, v);
2676 } else if (cft->trigger) {
2677 ret = cft->trigger(css, (unsigned int)cft->private);
2682 return ret ?: nbytes;
2685 static void *cgroup_seqfile_start(struct seq_file *seq, loff_t *ppos)
2687 return seq_cft(seq)->seq_start(seq, ppos);
2690 static void *cgroup_seqfile_next(struct seq_file *seq, void *v, loff_t *ppos)
2692 return seq_cft(seq)->seq_next(seq, v, ppos);
2695 static void cgroup_seqfile_stop(struct seq_file *seq, void *v)
2697 seq_cft(seq)->seq_stop(seq, v);
2700 static int cgroup_seqfile_show(struct seq_file *m, void *arg)
2702 struct cftype *cft = seq_cft(m);
2703 struct cgroup_subsys_state *css = seq_css(m);
2706 return cft->seq_show(m, arg);
2709 seq_printf(m, "%llu\n", cft->read_u64(css, cft));
2710 else if (cft->read_s64)
2711 seq_printf(m, "%lld\n", cft->read_s64(css, cft));
2717 static struct kernfs_ops cgroup_kf_single_ops = {
2718 .atomic_write_len = PAGE_SIZE,
2719 .write = cgroup_file_write,
2720 .seq_show = cgroup_seqfile_show,
2723 static struct kernfs_ops cgroup_kf_ops = {
2724 .atomic_write_len = PAGE_SIZE,
2725 .write = cgroup_file_write,
2726 .seq_start = cgroup_seqfile_start,
2727 .seq_next = cgroup_seqfile_next,
2728 .seq_stop = cgroup_seqfile_stop,
2729 .seq_show = cgroup_seqfile_show,
2733 * cgroup_rename - Only allow simple rename of directories in place.
2735 static int cgroup_rename(struct kernfs_node *kn, struct kernfs_node *new_parent,
2736 const char *new_name_str)
2738 struct cgroup *cgrp = kn->priv;
2741 if (kernfs_type(kn) != KERNFS_DIR)
2743 if (kn->parent != new_parent)
2747 * This isn't a proper migration and its usefulness is very
2748 * limited. Disallow if sane_behavior.
2750 if (cgroup_sane_behavior(cgrp))
2754 * We're gonna grab cgroup_tree_mutex which nests outside kernfs
2755 * active_ref. kernfs_rename() doesn't require active_ref
2756 * protection. Break them before grabbing cgroup_tree_mutex.
2758 kernfs_break_active_protection(new_parent);
2759 kernfs_break_active_protection(kn);
2761 mutex_lock(&cgroup_tree_mutex);
2762 mutex_lock(&cgroup_mutex);
2764 ret = kernfs_rename(kn, new_parent, new_name_str);
2766 mutex_unlock(&cgroup_mutex);
2767 mutex_unlock(&cgroup_tree_mutex);
2769 kernfs_unbreak_active_protection(kn);
2770 kernfs_unbreak_active_protection(new_parent);
2774 /* set uid and gid of cgroup dirs and files to that of the creator */
2775 static int cgroup_kn_set_ugid(struct kernfs_node *kn)
2777 struct iattr iattr = { .ia_valid = ATTR_UID | ATTR_GID,
2778 .ia_uid = current_fsuid(),
2779 .ia_gid = current_fsgid(), };
2781 if (uid_eq(iattr.ia_uid, GLOBAL_ROOT_UID) &&
2782 gid_eq(iattr.ia_gid, GLOBAL_ROOT_GID))
2785 return kernfs_setattr(kn, &iattr);
2788 static int cgroup_add_file(struct cgroup *cgrp, struct cftype *cft)
2790 char name[CGROUP_FILE_NAME_MAX];
2791 struct kernfs_node *kn;
2792 struct lock_class_key *key = NULL;
2795 #ifdef CONFIG_DEBUG_LOCK_ALLOC
2796 key = &cft->lockdep_key;
2798 kn = __kernfs_create_file(cgrp->kn, cgroup_file_name(cgrp, cft, name),
2799 cgroup_file_mode(cft), 0, cft->kf_ops, cft,
2804 ret = cgroup_kn_set_ugid(kn);
2810 if (cft->seq_show == cgroup_subtree_control_show)
2811 cgrp->control_kn = kn;
2816 * cgroup_addrm_files - add or remove files to a cgroup directory
2817 * @cgrp: the target cgroup
2818 * @cfts: array of cftypes to be added
2819 * @is_add: whether to add or remove
2821 * Depending on @is_add, add or remove files defined by @cfts on @cgrp.
2822 * For removals, this function never fails. If addition fails, this
2823 * function doesn't remove files already added. The caller is responsible
2826 static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
2832 lockdep_assert_held(&cgroup_tree_mutex);
2834 for (cft = cfts; cft->name[0] != '\0'; cft++) {
2835 /* does cft->flags tell us to skip this file on @cgrp? */
2836 if ((cft->flags & CFTYPE_ONLY_ON_DFL) && !cgroup_on_dfl(cgrp))
2838 if ((cft->flags & CFTYPE_INSANE) && cgroup_sane_behavior(cgrp))
2840 if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
2842 if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent)
2846 ret = cgroup_add_file(cgrp, cft);
2848 pr_warn("cgroup_addrm_files: failed to add %s, err=%d\n",
2853 cgroup_rm_file(cgrp, cft);
2859 static int cgroup_apply_cftypes(struct cftype *cfts, bool is_add)
2862 struct cgroup_subsys *ss = cfts[0].ss;
2863 struct cgroup *root = &ss->root->cgrp;
2864 struct cgroup_subsys_state *css;
2867 lockdep_assert_held(&cgroup_tree_mutex);
2869 /* add/rm files for all cgroups created before */
2870 css_for_each_descendant_pre(css, cgroup_css(root, ss)) {
2871 struct cgroup *cgrp = css->cgroup;
2873 if (cgroup_is_dead(cgrp))
2876 ret = cgroup_addrm_files(cgrp, cfts, is_add);
2882 kernfs_activate(root->kn);
2886 static void cgroup_exit_cftypes(struct cftype *cfts)
2890 for (cft = cfts; cft->name[0] != '\0'; cft++) {
2891 /* free copy for custom atomic_write_len, see init_cftypes() */
2892 if (cft->max_write_len && cft->max_write_len != PAGE_SIZE)
2899 static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
2903 for (cft = cfts; cft->name[0] != '\0'; cft++) {
2904 struct kernfs_ops *kf_ops;
2906 WARN_ON(cft->ss || cft->kf_ops);
2909 kf_ops = &cgroup_kf_ops;
2911 kf_ops = &cgroup_kf_single_ops;
2914 * Ugh... if @cft wants a custom max_write_len, we need to
2915 * make a copy of kf_ops to set its atomic_write_len.
2917 if (cft->max_write_len && cft->max_write_len != PAGE_SIZE) {
2918 kf_ops = kmemdup(kf_ops, sizeof(*kf_ops), GFP_KERNEL);
2920 cgroup_exit_cftypes(cfts);
2923 kf_ops->atomic_write_len = cft->max_write_len;
2926 cft->kf_ops = kf_ops;
2933 static int cgroup_rm_cftypes_locked(struct cftype *cfts)
2935 lockdep_assert_held(&cgroup_tree_mutex);
2937 if (!cfts || !cfts[0].ss)
2940 list_del(&cfts->node);
2941 cgroup_apply_cftypes(cfts, false);
2942 cgroup_exit_cftypes(cfts);
2947 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
2948 * @cfts: zero-length name terminated array of cftypes
2950 * Unregister @cfts. Files described by @cfts are removed from all
2951 * existing cgroups and all future cgroups won't have them either. This
2952 * function can be called anytime whether @cfts' subsys is attached or not.
2954 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
2957 int cgroup_rm_cftypes(struct cftype *cfts)
2961 mutex_lock(&cgroup_tree_mutex);
2962 ret = cgroup_rm_cftypes_locked(cfts);
2963 mutex_unlock(&cgroup_tree_mutex);
2968 * cgroup_add_cftypes - add an array of cftypes to a subsystem
2969 * @ss: target cgroup subsystem
2970 * @cfts: zero-length name terminated array of cftypes
2972 * Register @cfts to @ss. Files described by @cfts are created for all
2973 * existing cgroups to which @ss is attached and all future cgroups will
2974 * have them too. This function can be called anytime whether @ss is
2977 * Returns 0 on successful registration, -errno on failure. Note that this
2978 * function currently returns 0 as long as @cfts registration is successful
2979 * even if some file creation attempts on existing cgroups fail.
2981 int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
2985 if (!cfts || cfts[0].name[0] == '\0')
2988 ret = cgroup_init_cftypes(ss, cfts);
2992 mutex_lock(&cgroup_tree_mutex);
2994 list_add_tail(&cfts->node, &ss->cfts);
2995 ret = cgroup_apply_cftypes(cfts, true);
2997 cgroup_rm_cftypes_locked(cfts);
2999 mutex_unlock(&cgroup_tree_mutex);
3004 * cgroup_task_count - count the number of tasks in a cgroup.
3005 * @cgrp: the cgroup in question
3007 * Return the number of tasks in the cgroup.
3009 static int cgroup_task_count(const struct cgroup *cgrp)
3012 struct cgrp_cset_link *link;
3014 down_read(&css_set_rwsem);
3015 list_for_each_entry(link, &cgrp->cset_links, cset_link)
3016 count += atomic_read(&link->cset->refcount);
3017 up_read(&css_set_rwsem);
3022 * css_next_child - find the next child of a given css
3023 * @pos_css: the current position (%NULL to initiate traversal)
3024 * @parent_css: css whose children to walk
3026 * This function returns the next child of @parent_css and should be called
3027 * under either cgroup_mutex or RCU read lock. The only requirement is
3028 * that @parent_css and @pos_css are accessible. The next sibling is
3029 * guaranteed to be returned regardless of their states.
3031 struct cgroup_subsys_state *
3032 css_next_child(struct cgroup_subsys_state *pos_css,
3033 struct cgroup_subsys_state *parent_css)
3035 struct cgroup *pos = pos_css ? pos_css->cgroup : NULL;
3036 struct cgroup *cgrp = parent_css->cgroup;
3037 struct cgroup *next;
3039 cgroup_assert_mutexes_or_rcu_locked();
3042 * @pos could already have been removed. Once a cgroup is removed,
3043 * its ->sibling.next is no longer updated when its next sibling
3044 * changes. As CGRP_DEAD assertion is serialized and happens
3045 * before the cgroup is taken off the ->sibling list, if we see it
3046 * unasserted, it's guaranteed that the next sibling hasn't
3047 * finished its grace period even if it's already removed, and thus
3048 * safe to dereference from this RCU critical section. If
3049 * ->sibling.next is inaccessible, cgroup_is_dead() is guaranteed
3050 * to be visible as %true here.
3052 * If @pos is dead, its next pointer can't be dereferenced;
3053 * however, as each cgroup is given a monotonically increasing
3054 * unique serial number and always appended to the sibling list,
3055 * the next one can be found by walking the parent's children until
3056 * we see a cgroup with higher serial number than @pos's. While
3057 * this path can be slower, it's taken only when either the current
3058 * cgroup is removed or iteration and removal race.
3061 next = list_entry_rcu(cgrp->children.next, struct cgroup, sibling);
3062 } else if (likely(!cgroup_is_dead(pos))) {
3063 next = list_entry_rcu(pos->sibling.next, struct cgroup, sibling);
3065 list_for_each_entry_rcu(next, &cgrp->children, sibling)
3066 if (next->serial_nr > pos->serial_nr)
3071 * @next, if not pointing to the head, can be dereferenced and is
3072 * the next sibling; however, it might have @ss disabled. If so,
3073 * fast-forward to the next enabled one.
3075 while (&next->sibling != &cgrp->children) {
3076 struct cgroup_subsys_state *next_css = cgroup_css(next, parent_css->ss);
3080 next = list_entry_rcu(next->sibling.next, struct cgroup, sibling);
3086 * css_next_descendant_pre - find the next descendant for pre-order walk
3087 * @pos: the current position (%NULL to initiate traversal)
3088 * @root: css whose descendants to walk
3090 * To be used by css_for_each_descendant_pre(). Find the next descendant
3091 * to visit for pre-order traversal of @root's descendants. @root is
3092 * included in the iteration and the first node to be visited.
3094 * While this function requires cgroup_mutex or RCU read locking, it
3095 * doesn't require the whole traversal to be contained in a single critical
3096 * section. This function will return the correct next descendant as long
3097 * as both @pos and @root are accessible and @pos is a descendant of @root.
3099 struct cgroup_subsys_state *
3100 css_next_descendant_pre(struct cgroup_subsys_state *pos,
3101 struct cgroup_subsys_state *root)
3103 struct cgroup_subsys_state *next;
3105 cgroup_assert_mutexes_or_rcu_locked();
3107 /* if first iteration, visit @root */
3111 /* visit the first child if exists */
3112 next = css_next_child(NULL, pos);
3116 /* no child, visit my or the closest ancestor's next sibling */
3117 while (pos != root) {
3118 next = css_next_child(pos, css_parent(pos));
3121 pos = css_parent(pos);
3128 * css_rightmost_descendant - return the rightmost descendant of a css
3129 * @pos: css of interest
3131 * Return the rightmost descendant of @pos. If there's no descendant, @pos
3132 * is returned. This can be used during pre-order traversal to skip
3135 * While this function requires cgroup_mutex or RCU read locking, it
3136 * doesn't require the whole traversal to be contained in a single critical
3137 * section. This function will return the correct rightmost descendant as
3138 * long as @pos is accessible.
3140 struct cgroup_subsys_state *
3141 css_rightmost_descendant(struct cgroup_subsys_state *pos)
3143 struct cgroup_subsys_state *last, *tmp;
3145 cgroup_assert_mutexes_or_rcu_locked();
3149 /* ->prev isn't RCU safe, walk ->next till the end */
3151 css_for_each_child(tmp, last)
3158 static struct cgroup_subsys_state *
3159 css_leftmost_descendant(struct cgroup_subsys_state *pos)
3161 struct cgroup_subsys_state *last;
3165 pos = css_next_child(NULL, pos);
3172 * css_next_descendant_post - find the next descendant for post-order walk
3173 * @pos: the current position (%NULL to initiate traversal)
3174 * @root: css whose descendants to walk
3176 * To be used by css_for_each_descendant_post(). Find the next descendant
3177 * to visit for post-order traversal of @root's descendants. @root is
3178 * included in the iteration and the last node to be visited.
3180 * While this function requires cgroup_mutex or RCU read locking, it
3181 * doesn't require the whole traversal to be contained in a single critical
3182 * section. This function will return the correct next descendant as long
3183 * as both @pos and @cgroup are accessible and @pos is a descendant of
3186 struct cgroup_subsys_state *
3187 css_next_descendant_post(struct cgroup_subsys_state *pos,
3188 struct cgroup_subsys_state *root)
3190 struct cgroup_subsys_state *next;
3192 cgroup_assert_mutexes_or_rcu_locked();
3194 /* if first iteration, visit leftmost descendant which may be @root */
3196 return css_leftmost_descendant(root);
3198 /* if we visited @root, we're done */
3202 /* if there's an unvisited sibling, visit its leftmost descendant */
3203 next = css_next_child(pos, css_parent(pos));
3205 return css_leftmost_descendant(next);
3207 /* no sibling left, visit parent */
3208 return css_parent(pos);
3212 * css_advance_task_iter - advance a task itererator to the next css_set
3213 * @it: the iterator to advance
3215 * Advance @it to the next css_set to walk.
3217 static void css_advance_task_iter(struct css_task_iter *it)
3219 struct list_head *l = it->cset_pos;
3220 struct cgrp_cset_link *link;
3221 struct css_set *cset;
3223 /* Advance to the next non-empty css_set */
3226 if (l == it->cset_head) {
3227 it->cset_pos = NULL;
3232 cset = container_of(l, struct css_set,
3233 e_cset_node[it->ss->id]);
3235 link = list_entry(l, struct cgrp_cset_link, cset_link);
3238 } while (list_empty(&cset->tasks) && list_empty(&cset->mg_tasks));
3242 if (!list_empty(&cset->tasks))
3243 it->task_pos = cset->tasks.next;
3245 it->task_pos = cset->mg_tasks.next;
3247 it->tasks_head = &cset->tasks;
3248 it->mg_tasks_head = &cset->mg_tasks;
3252 * css_task_iter_start - initiate task iteration
3253 * @css: the css to walk tasks of
3254 * @it: the task iterator to use
3256 * Initiate iteration through the tasks of @css. The caller can call
3257 * css_task_iter_next() to walk through the tasks until the function
3258 * returns NULL. On completion of iteration, css_task_iter_end() must be
3261 * Note that this function acquires a lock which is released when the
3262 * iteration finishes. The caller can't sleep while iteration is in
3265 void css_task_iter_start(struct cgroup_subsys_state *css,
3266 struct css_task_iter *it)
3267 __acquires(css_set_rwsem)
3269 /* no one should try to iterate before mounting cgroups */
3270 WARN_ON_ONCE(!use_task_css_set_links);
3272 down_read(&css_set_rwsem);
3277 it->cset_pos = &css->cgroup->e_csets[css->ss->id];
3279 it->cset_pos = &css->cgroup->cset_links;
3281 it->cset_head = it->cset_pos;
3283 css_advance_task_iter(it);
3287 * css_task_iter_next - return the next task for the iterator
3288 * @it: the task iterator being iterated
3290 * The "next" function for task iteration. @it should have been
3291 * initialized via css_task_iter_start(). Returns NULL when the iteration
3294 struct task_struct *css_task_iter_next(struct css_task_iter *it)
3296 struct task_struct *res;
3297 struct list_head *l = it->task_pos;
3299 /* If the iterator cg is NULL, we have no tasks */
3302 res = list_entry(l, struct task_struct, cg_list);
3305 * Advance iterator to find next entry. cset->tasks is consumed
3306 * first and then ->mg_tasks. After ->mg_tasks, we move onto the
3311 if (l == it->tasks_head)
3312 l = it->mg_tasks_head->next;
3314 if (l == it->mg_tasks_head)
3315 css_advance_task_iter(it);
3323 * css_task_iter_end - finish task iteration
3324 * @it: the task iterator to finish
3326 * Finish task iteration started by css_task_iter_start().
3328 void css_task_iter_end(struct css_task_iter *it)
3329 __releases(css_set_rwsem)
3331 up_read(&css_set_rwsem);
3335 * cgroup_trasnsfer_tasks - move tasks from one cgroup to another
3336 * @to: cgroup to which the tasks will be moved
3337 * @from: cgroup in which the tasks currently reside
3339 * Locking rules between cgroup_post_fork() and the migration path
3340 * guarantee that, if a task is forking while being migrated, the new child
3341 * is guaranteed to be either visible in the source cgroup after the
3342 * parent's migration is complete or put into the target cgroup. No task
3343 * can slip out of migration through forking.
3345 int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
3347 LIST_HEAD(preloaded_csets);
3348 struct cgrp_cset_link *link;
3349 struct css_task_iter it;
3350 struct task_struct *task;
3353 mutex_lock(&cgroup_mutex);
3355 /* all tasks in @from are being moved, all csets are source */
3356 down_read(&css_set_rwsem);
3357 list_for_each_entry(link, &from->cset_links, cset_link)
3358 cgroup_migrate_add_src(link->cset, to, &preloaded_csets);
3359 up_read(&css_set_rwsem);
3361 ret = cgroup_migrate_prepare_dst(to, &preloaded_csets);
3366 * Migrate tasks one-by-one until @form is empty. This fails iff
3367 * ->can_attach() fails.
3370 css_task_iter_start(&from->dummy_css, &it);
3371 task = css_task_iter_next(&it);
3373 get_task_struct(task);
3374 css_task_iter_end(&it);
3377 ret = cgroup_migrate(to, task, false);
3378 put_task_struct(task);
3380 } while (task && !ret);
3382 cgroup_migrate_finish(&preloaded_csets);
3383 mutex_unlock(&cgroup_mutex);
3388 * Stuff for reading the 'tasks'/'procs' files.
3390 * Reading this file can return large amounts of data if a cgroup has
3391 * *lots* of attached tasks. So it may need several calls to read(),
3392 * but we cannot guarantee that the information we produce is correct
3393 * unless we produce it entirely atomically.
3397 /* which pidlist file are we talking about? */
3398 enum cgroup_filetype {
3404 * A pidlist is a list of pids that virtually represents the contents of one
3405 * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
3406 * a pair (one each for procs, tasks) for each pid namespace that's relevant
3409 struct cgroup_pidlist {
3411 * used to find which pidlist is wanted. doesn't change as long as
3412 * this particular list stays in the list.
3414 struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;
3417 /* how many elements the above list has */
3419 /* each of these stored in a list by its cgroup */
3420 struct list_head links;
3421 /* pointer to the cgroup we belong to, for list removal purposes */
3422 struct cgroup *owner;
3423 /* for delayed destruction */
3424 struct delayed_work destroy_dwork;
3428 * The following two functions "fix" the issue where there are more pids
3429 * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
3430 * TODO: replace with a kernel-wide solution to this problem
3432 #define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
3433 static void *pidlist_allocate(int count)
3435 if (PIDLIST_TOO_LARGE(count))
3436 return vmalloc(count * sizeof(pid_t));
3438 return kmalloc(count * sizeof(pid_t), GFP_KERNEL);
3441 static void pidlist_free(void *p)
3443 if (is_vmalloc_addr(p))
3450 * Used to destroy all pidlists lingering waiting for destroy timer. None
3451 * should be left afterwards.
3453 static void cgroup_pidlist_destroy_all(struct cgroup *cgrp)
3455 struct cgroup_pidlist *l, *tmp_l;
3457 mutex_lock(&cgrp->pidlist_mutex);
3458 list_for_each_entry_safe(l, tmp_l, &cgrp->pidlists, links)
3459 mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork, 0);
3460 mutex_unlock(&cgrp->pidlist_mutex);
3462 flush_workqueue(cgroup_pidlist_destroy_wq);
3463 BUG_ON(!list_empty(&cgrp->pidlists));
3466 static void cgroup_pidlist_destroy_work_fn(struct work_struct *work)
3468 struct delayed_work *dwork = to_delayed_work(work);
3469 struct cgroup_pidlist *l = container_of(dwork, struct cgroup_pidlist,
3471 struct cgroup_pidlist *tofree = NULL;
3473 mutex_lock(&l->owner->pidlist_mutex);
3476 * Destroy iff we didn't get queued again. The state won't change
3477 * as destroy_dwork can only be queued while locked.
3479 if (!delayed_work_pending(dwork)) {
3480 list_del(&l->links);
3481 pidlist_free(l->list);
3482 put_pid_ns(l->key.ns);
3486 mutex_unlock(&l->owner->pidlist_mutex);
3491 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
3492 * Returns the number of unique elements.
3494 static int pidlist_uniq(pid_t *list, int length)
3499 * we presume the 0th element is unique, so i starts at 1. trivial
3500 * edge cases first; no work needs to be done for either
3502 if (length == 0 || length == 1)
3504 /* src and dest walk down the list; dest counts unique elements */
3505 for (src = 1; src < length; src++) {
3506 /* find next unique element */
3507 while (list[src] == list[src-1]) {
3512 /* dest always points to where the next unique element goes */
3513 list[dest] = list[src];
3521 * The two pid files - task and cgroup.procs - guaranteed that the result
3522 * is sorted, which forced this whole pidlist fiasco. As pid order is
3523 * different per namespace, each namespace needs differently sorted list,
3524 * making it impossible to use, for example, single rbtree of member tasks
3525 * sorted by task pointer. As pidlists can be fairly large, allocating one
3526 * per open file is dangerous, so cgroup had to implement shared pool of
3527 * pidlists keyed by cgroup and namespace.
3529 * All this extra complexity was caused by the original implementation
3530 * committing to an entirely unnecessary property. In the long term, we
3531 * want to do away with it. Explicitly scramble sort order if
3532 * sane_behavior so that no such expectation exists in the new interface.
3534 * Scrambling is done by swapping every two consecutive bits, which is
3535 * non-identity one-to-one mapping which disturbs sort order sufficiently.
3537 static pid_t pid_fry(pid_t pid)
3539 unsigned a = pid & 0x55555555;
3540 unsigned b = pid & 0xAAAAAAAA;
3542 return (a << 1) | (b >> 1);
3545 static pid_t cgroup_pid_fry(struct cgroup *cgrp, pid_t pid)
3547 if (cgroup_sane_behavior(cgrp))
3548 return pid_fry(pid);
3553 static int cmppid(const void *a, const void *b)
3555 return *(pid_t *)a - *(pid_t *)b;
3558 static int fried_cmppid(const void *a, const void *b)
3560 return pid_fry(*(pid_t *)a) - pid_fry(*(pid_t *)b);
3563 static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
3564 enum cgroup_filetype type)
3566 struct cgroup_pidlist *l;
3567 /* don't need task_nsproxy() if we're looking at ourself */
3568 struct pid_namespace *ns = task_active_pid_ns(current);
3570 lockdep_assert_held(&cgrp->pidlist_mutex);
3572 list_for_each_entry(l, &cgrp->pidlists, links)
3573 if (l->key.type == type && l->key.ns == ns)
3579 * find the appropriate pidlist for our purpose (given procs vs tasks)
3580 * returns with the lock on that pidlist already held, and takes care
3581 * of the use count, or returns NULL with no locks held if we're out of
3584 static struct cgroup_pidlist *cgroup_pidlist_find_create(struct cgroup *cgrp,
3585 enum cgroup_filetype type)
3587 struct cgroup_pidlist *l;
3589 lockdep_assert_held(&cgrp->pidlist_mutex);
3591 l = cgroup_pidlist_find(cgrp, type);
3595 /* entry not found; create a new one */
3596 l = kzalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
3600 INIT_DELAYED_WORK(&l->destroy_dwork, cgroup_pidlist_destroy_work_fn);
3602 /* don't need task_nsproxy() if we're looking at ourself */
3603 l->key.ns = get_pid_ns(task_active_pid_ns(current));
3605 list_add(&l->links, &cgrp->pidlists);
3610 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
3612 static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
3613 struct cgroup_pidlist **lp)
3617 int pid, n = 0; /* used for populating the array */
3618 struct css_task_iter it;
3619 struct task_struct *tsk;
3620 struct cgroup_pidlist *l;
3622 lockdep_assert_held(&cgrp->pidlist_mutex);
3625 * If cgroup gets more users after we read count, we won't have
3626 * enough space - tough. This race is indistinguishable to the
3627 * caller from the case that the additional cgroup users didn't
3628 * show up until sometime later on.
3630 length = cgroup_task_count(cgrp);
3631 array = pidlist_allocate(length);
3634 /* now, populate the array */
3635 css_task_iter_start(&cgrp->dummy_css, &it);
3636 while ((tsk = css_task_iter_next(&it))) {
3637 if (unlikely(n == length))
3639 /* get tgid or pid for procs or tasks file respectively */
3640 if (type == CGROUP_FILE_PROCS)
3641 pid = task_tgid_vnr(tsk);
3643 pid = task_pid_vnr(tsk);
3644 if (pid > 0) /* make sure to only use valid results */
3647 css_task_iter_end(&it);
3649 /* now sort & (if procs) strip out duplicates */
3650 if (cgroup_sane_behavior(cgrp))
3651 sort(array, length, sizeof(pid_t), fried_cmppid, NULL);
3653 sort(array, length, sizeof(pid_t), cmppid, NULL);
3654 if (type == CGROUP_FILE_PROCS)
3655 length = pidlist_uniq(array, length);
3657 l = cgroup_pidlist_find_create(cgrp, type);
3659 mutex_unlock(&cgrp->pidlist_mutex);
3660 pidlist_free(array);
3664 /* store array, freeing old if necessary */
3665 pidlist_free(l->list);
3673 * cgroupstats_build - build and fill cgroupstats
3674 * @stats: cgroupstats to fill information into
3675 * @dentry: A dentry entry belonging to the cgroup for which stats have
3678 * Build and fill cgroupstats so that taskstats can export it to user
3681 int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
3683 struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
3684 struct cgroup *cgrp;
3685 struct css_task_iter it;
3686 struct task_struct *tsk;
3688 /* it should be kernfs_node belonging to cgroupfs and is a directory */
3689 if (dentry->d_sb->s_type != &cgroup_fs_type || !kn ||
3690 kernfs_type(kn) != KERNFS_DIR)
3693 mutex_lock(&cgroup_mutex);
3696 * We aren't being called from kernfs and there's no guarantee on
3697 * @kn->priv's validity. For this and css_tryget_from_dir(),
3698 * @kn->priv is RCU safe. Let's do the RCU dancing.
3701 cgrp = rcu_dereference(kn->priv);
3702 if (!cgrp || cgroup_is_dead(cgrp)) {
3704 mutex_unlock(&cgroup_mutex);
3709 css_task_iter_start(&cgrp->dummy_css, &it);
3710 while ((tsk = css_task_iter_next(&it))) {
3711 switch (tsk->state) {
3713 stats->nr_running++;
3715 case TASK_INTERRUPTIBLE:
3716 stats->nr_sleeping++;
3718 case TASK_UNINTERRUPTIBLE:
3719 stats->nr_uninterruptible++;
3722 stats->nr_stopped++;
3725 if (delayacct_is_task_waiting_on_io(tsk))
3726 stats->nr_io_wait++;
3730 css_task_iter_end(&it);
3732 mutex_unlock(&cgroup_mutex);
3738 * seq_file methods for the tasks/procs files. The seq_file position is the
3739 * next pid to display; the seq_file iterator is a pointer to the pid
3740 * in the cgroup->l->list array.
3743 static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
3746 * Initially we receive a position value that corresponds to
3747 * one more than the last pid shown (or 0 on the first call or
3748 * after a seek to the start). Use a binary-search to find the
3749 * next pid to display, if any
3751 struct kernfs_open_file *of = s->private;
3752 struct cgroup *cgrp = seq_css(s)->cgroup;
3753 struct cgroup_pidlist *l;
3754 enum cgroup_filetype type = seq_cft(s)->private;
3755 int index = 0, pid = *pos;
3758 mutex_lock(&cgrp->pidlist_mutex);
3761 * !NULL @of->priv indicates that this isn't the first start()
3762 * after open. If the matching pidlist is around, we can use that.
3763 * Look for it. Note that @of->priv can't be used directly. It
3764 * could already have been destroyed.
3767 of->priv = cgroup_pidlist_find(cgrp, type);
3770 * Either this is the first start() after open or the matching
3771 * pidlist has been destroyed inbetween. Create a new one.
3774 ret = pidlist_array_load(cgrp, type,
3775 (struct cgroup_pidlist **)&of->priv);
3777 return ERR_PTR(ret);
3782 int end = l->length;
3784 while (index < end) {
3785 int mid = (index + end) / 2;
3786 if (cgroup_pid_fry(cgrp, l->list[mid]) == pid) {
3789 } else if (cgroup_pid_fry(cgrp, l->list[mid]) <= pid)
3795 /* If we're off the end of the array, we're done */
3796 if (index >= l->length)
3798 /* Update the abstract position to be the actual pid that we found */
3799 iter = l->list + index;
3800 *pos = cgroup_pid_fry(cgrp, *iter);
3804 static void cgroup_pidlist_stop(struct seq_file *s, void *v)
3806 struct kernfs_open_file *of = s->private;
3807 struct cgroup_pidlist *l = of->priv;
3810 mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork,
3811 CGROUP_PIDLIST_DESTROY_DELAY);
3812 mutex_unlock(&seq_css(s)->cgroup->pidlist_mutex);
3815 static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
3817 struct kernfs_open_file *of = s->private;
3818 struct cgroup_pidlist *l = of->priv;
3820 pid_t *end = l->list + l->length;
3822 * Advance to the next pid in the array. If this goes off the
3829 *pos = cgroup_pid_fry(seq_css(s)->cgroup, *p);
3834 static int cgroup_pidlist_show(struct seq_file *s, void *v)
3836 return seq_printf(s, "%d\n", *(int *)v);
3840 * seq_operations functions for iterating on pidlists through seq_file -
3841 * independent of whether it's tasks or procs
3843 static const struct seq_operations cgroup_pidlist_seq_operations = {
3844 .start = cgroup_pidlist_start,
3845 .stop = cgroup_pidlist_stop,
3846 .next = cgroup_pidlist_next,
3847 .show = cgroup_pidlist_show,
3850 static u64 cgroup_read_notify_on_release(struct cgroup_subsys_state *css,
3853 return notify_on_release(css->cgroup);
3856 static int cgroup_write_notify_on_release(struct cgroup_subsys_state *css,
3857 struct cftype *cft, u64 val)
3859 clear_bit(CGRP_RELEASABLE, &css->cgroup->flags);
3861 set_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
3863 clear_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
3867 static u64 cgroup_clone_children_read(struct cgroup_subsys_state *css,
3870 return test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
3873 static int cgroup_clone_children_write(struct cgroup_subsys_state *css,
3874 struct cftype *cft, u64 val)
3877 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
3879 clear_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
3883 static struct cftype cgroup_base_files[] = {
3885 .name = "cgroup.procs",
3886 .seq_start = cgroup_pidlist_start,
3887 .seq_next = cgroup_pidlist_next,
3888 .seq_stop = cgroup_pidlist_stop,
3889 .seq_show = cgroup_pidlist_show,
3890 .private = CGROUP_FILE_PROCS,
3891 .write_u64 = cgroup_procs_write,
3892 .mode = S_IRUGO | S_IWUSR,
3895 .name = "cgroup.clone_children",
3896 .flags = CFTYPE_INSANE,
3897 .read_u64 = cgroup_clone_children_read,
3898 .write_u64 = cgroup_clone_children_write,
3901 .name = "cgroup.sane_behavior",
3902 .flags = CFTYPE_ONLY_ON_ROOT,
3903 .seq_show = cgroup_sane_behavior_show,
3906 .name = "cgroup.controllers",
3907 .flags = CFTYPE_ONLY_ON_DFL | CFTYPE_ONLY_ON_ROOT,
3908 .seq_show = cgroup_root_controllers_show,
3911 .name = "cgroup.controllers",
3912 .flags = CFTYPE_ONLY_ON_DFL | CFTYPE_NOT_ON_ROOT,
3913 .seq_show = cgroup_controllers_show,
3916 .name = "cgroup.subtree_control",
3917 .flags = CFTYPE_ONLY_ON_DFL,
3918 .seq_show = cgroup_subtree_control_show,
3919 .write_string = cgroup_subtree_control_write,
3923 * Historical crazy stuff. These don't have "cgroup." prefix and
3924 * don't exist if sane_behavior. If you're depending on these, be
3925 * prepared to be burned.
3929 .flags = CFTYPE_INSANE, /* use "procs" instead */
3930 .seq_start = cgroup_pidlist_start,
3931 .seq_next = cgroup_pidlist_next,
3932 .seq_stop = cgroup_pidlist_stop,
3933 .seq_show = cgroup_pidlist_show,
3934 .private = CGROUP_FILE_TASKS,
3935 .write_u64 = cgroup_tasks_write,
3936 .mode = S_IRUGO | S_IWUSR,
3939 .name = "notify_on_release",
3940 .flags = CFTYPE_INSANE,
3941 .read_u64 = cgroup_read_notify_on_release,
3942 .write_u64 = cgroup_write_notify_on_release,
3945 .name = "release_agent",
3946 .flags = CFTYPE_INSANE | CFTYPE_ONLY_ON_ROOT,
3947 .seq_show = cgroup_release_agent_show,
3948 .write_string = cgroup_release_agent_write,
3949 .max_write_len = PATH_MAX - 1,
3955 * cgroup_populate_dir - create subsys files in a cgroup directory
3956 * @cgrp: target cgroup
3957 * @subsys_mask: mask of the subsystem ids whose files should be added
3959 * On failure, no file is added.
3961 static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask)
3963 struct cgroup_subsys *ss;
3966 /* process cftsets of each subsystem */
3967 for_each_subsys(ss, i) {
3968 struct cftype *cfts;
3970 if (!test_bit(i, &subsys_mask))
3973 list_for_each_entry(cfts, &ss->cfts, node) {
3974 ret = cgroup_addrm_files(cgrp, cfts, true);
3981 cgroup_clear_dir(cgrp, subsys_mask);
3986 * css destruction is four-stage process.
3988 * 1. Destruction starts. Killing of the percpu_ref is initiated.
3989 * Implemented in kill_css().
3991 * 2. When the percpu_ref is confirmed to be visible as killed on all CPUs
3992 * and thus css_tryget() is guaranteed to fail, the css can be offlined
3993 * by invoking offline_css(). After offlining, the base ref is put.
3994 * Implemented in css_killed_work_fn().
3996 * 3. When the percpu_ref reaches zero, the only possible remaining
3997 * accessors are inside RCU read sections. css_release() schedules the
4000 * 4. After the grace period, the css can be freed. Implemented in
4001 * css_free_work_fn().
4003 * It is actually hairier because both step 2 and 4 require process context
4004 * and thus involve punting to css->destroy_work adding two additional
4005 * steps to the already complex sequence.
4007 static void css_free_work_fn(struct work_struct *work)
4009 struct cgroup_subsys_state *css =
4010 container_of(work, struct cgroup_subsys_state, destroy_work);
4011 struct cgroup *cgrp = css->cgroup;
4014 css_put(css->parent);
4016 css->ss->css_free(css);
4020 static void css_free_rcu_fn(struct rcu_head *rcu_head)
4022 struct cgroup_subsys_state *css =
4023 container_of(rcu_head, struct cgroup_subsys_state, rcu_head);
4025 INIT_WORK(&css->destroy_work, css_free_work_fn);
4026 queue_work(cgroup_destroy_wq, &css->destroy_work);
4029 static void css_release(struct percpu_ref *ref)
4031 struct cgroup_subsys_state *css =
4032 container_of(ref, struct cgroup_subsys_state, refcnt);
4034 RCU_INIT_POINTER(css->cgroup->subsys[css->ss->id], NULL);
4035 call_rcu(&css->rcu_head, css_free_rcu_fn);
4038 static void init_css(struct cgroup_subsys_state *css, struct cgroup_subsys *ss,
4039 struct cgroup *cgrp)
4046 css->parent = cgroup_css(cgrp->parent, ss);
4048 css->flags |= CSS_ROOT;
4050 BUG_ON(cgroup_css(cgrp, ss));
4053 /* invoke ->css_online() on a new CSS and mark it online if successful */
4054 static int online_css(struct cgroup_subsys_state *css)
4056 struct cgroup_subsys *ss = css->ss;
4059 lockdep_assert_held(&cgroup_tree_mutex);
4060 lockdep_assert_held(&cgroup_mutex);
4063 ret = ss->css_online(css);
4065 css->flags |= CSS_ONLINE;
4066 css->cgroup->nr_css++;
4067 rcu_assign_pointer(css->cgroup->subsys[ss->id], css);
4072 /* if the CSS is online, invoke ->css_offline() on it and mark it offline */
4073 static void offline_css(struct cgroup_subsys_state *css)
4075 struct cgroup_subsys *ss = css->ss;
4077 lockdep_assert_held(&cgroup_tree_mutex);
4078 lockdep_assert_held(&cgroup_mutex);
4080 if (!(css->flags & CSS_ONLINE))
4083 if (ss->css_offline)
4084 ss->css_offline(css);
4086 css->flags &= ~CSS_ONLINE;
4087 css->cgroup->nr_css--;
4088 RCU_INIT_POINTER(css->cgroup->subsys[ss->id], NULL);
4090 wake_up_all(&css->cgroup->offline_waitq);
4094 * create_css - create a cgroup_subsys_state
4095 * @cgrp: the cgroup new css will be associated with
4096 * @ss: the subsys of new css
4098 * Create a new css associated with @cgrp - @ss pair. On success, the new
4099 * css is online and installed in @cgrp with all interface files created.
4100 * Returns 0 on success, -errno on failure.
4102 static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss)
4104 struct cgroup *parent = cgrp->parent;
4105 struct cgroup_subsys_state *css;
4108 lockdep_assert_held(&cgroup_mutex);
4110 css = ss->css_alloc(cgroup_css(parent, ss));
4112 return PTR_ERR(css);
4114 err = percpu_ref_init(&css->refcnt, css_release);
4118 init_css(css, ss, cgrp);
4120 err = cgroup_populate_dir(cgrp, 1 << ss->id);
4122 goto err_free_percpu_ref;
4124 err = online_css(css);
4129 css_get(css->parent);
4131 if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
4133 pr_warning("cgroup: %s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n",
4134 current->comm, current->pid, ss->name);
4135 if (!strcmp(ss->name, "memory"))
4136 pr_warning("cgroup: \"memory\" requires setting use_hierarchy to 1 on the root.\n");
4137 ss->warned_broken_hierarchy = true;
4143 cgroup_clear_dir(css->cgroup, 1 << css->ss->id);
4144 err_free_percpu_ref:
4145 percpu_ref_cancel_init(&css->refcnt);
4152 * cgroup_create - create a cgroup
4153 * @parent: cgroup that will be parent of the new cgroup
4154 * @name: name of the new cgroup
4155 * @mode: mode to set on new cgroup
4157 static long cgroup_create(struct cgroup *parent, const char *name,
4160 struct cgroup *cgrp;
4161 struct cgroup_root *root = parent->root;
4163 struct cgroup_subsys *ss;
4164 struct kernfs_node *kn;
4166 /* allocate the cgroup and its ID, 0 is reserved for the root */
4167 cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
4171 mutex_lock(&cgroup_tree_mutex);
4174 * Only live parents can have children. Note that the liveliness
4175 * check isn't strictly necessary because cgroup_mkdir() and
4176 * cgroup_rmdir() are fully synchronized by i_mutex; however, do it
4177 * anyway so that locking is contained inside cgroup proper and we
4178 * don't get nasty surprises if we ever grow another caller.
4180 if (!cgroup_lock_live_group(parent)) {
4182 goto err_unlock_tree;
4186 * Temporarily set the pointer to NULL, so idr_find() won't return
4187 * a half-baked cgroup.
4189 cgrp->id = idr_alloc(&root->cgroup_idr, NULL, 1, 0, GFP_KERNEL);
4195 init_cgroup_housekeeping(cgrp);
4197 cgrp->parent = parent;
4198 cgrp->dummy_css.parent = &parent->dummy_css;
4199 cgrp->root = parent->root;
4201 if (notify_on_release(parent))
4202 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
4204 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags))
4205 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
4207 /* create the directory */
4208 kn = kernfs_create_dir(parent->kn, name, mode, cgrp);
4216 * This extra ref will be put in cgroup_free_fn() and guarantees
4217 * that @cgrp->kn is always accessible.
4221 cgrp->serial_nr = cgroup_serial_nr_next++;
4223 /* allocation complete, commit to creation */
4224 list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);
4225 atomic_inc(&root->nr_cgrps);
4229 * @cgrp is now fully operational. If something fails after this
4230 * point, it'll be released via the normal destruction path.
4232 idr_replace(&root->cgroup_idr, cgrp, cgrp->id);
4234 err = cgroup_kn_set_ugid(kn);
4238 err = cgroup_addrm_files(cgrp, cgroup_base_files, true);
4242 /* let's create and online css's */
4243 for_each_subsys(ss, ssid) {
4244 if (parent->child_subsys_mask & (1 << ssid)) {
4245 err = create_css(cgrp, ss);
4252 * On the default hierarchy, a child doesn't automatically inherit
4253 * child_subsys_mask from the parent. Each is configured manually.
4255 if (!cgroup_on_dfl(cgrp))
4256 cgrp->child_subsys_mask = parent->child_subsys_mask;
4258 kernfs_activate(kn);
4260 mutex_unlock(&cgroup_mutex);
4261 mutex_unlock(&cgroup_tree_mutex);
4266 idr_remove(&root->cgroup_idr, cgrp->id);
4268 mutex_unlock(&cgroup_mutex);
4270 mutex_unlock(&cgroup_tree_mutex);
4275 cgroup_destroy_locked(cgrp);
4276 mutex_unlock(&cgroup_mutex);
4277 mutex_unlock(&cgroup_tree_mutex);
4281 static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
4284 struct cgroup *parent = parent_kn->priv;
4288 * cgroup_create() grabs cgroup_tree_mutex which nests outside
4289 * kernfs active_ref and cgroup_create() already synchronizes
4290 * properly against removal through cgroup_lock_live_group().
4291 * Break it before calling cgroup_create().
4294 kernfs_break_active_protection(parent_kn);
4296 ret = cgroup_create(parent, name, mode);
4298 kernfs_unbreak_active_protection(parent_kn);
4304 * This is called when the refcnt of a css is confirmed to be killed.
4305 * css_tryget() is now guaranteed to fail.
4307 static void css_killed_work_fn(struct work_struct *work)
4309 struct cgroup_subsys_state *css =
4310 container_of(work, struct cgroup_subsys_state, destroy_work);
4311 struct cgroup *cgrp = css->cgroup;
4313 mutex_lock(&cgroup_tree_mutex);
4314 mutex_lock(&cgroup_mutex);
4317 * css_tryget() is guaranteed to fail now. Tell subsystems to
4318 * initate destruction.
4323 * If @cgrp is marked dead, it's waiting for refs of all css's to
4324 * be disabled before proceeding to the second phase of cgroup
4325 * destruction. If we are the last one, kick it off.
4327 if (!cgrp->nr_css && cgroup_is_dead(cgrp))
4328 cgroup_destroy_css_killed(cgrp);
4330 mutex_unlock(&cgroup_mutex);
4331 mutex_unlock(&cgroup_tree_mutex);
4334 * Put the css refs from kill_css(). Each css holds an extra
4335 * reference to the cgroup's dentry and cgroup removal proceeds
4336 * regardless of css refs. On the last put of each css, whenever
4337 * that may be, the extra dentry ref is put so that dentry
4338 * destruction happens only after all css's are released.
4343 /* css kill confirmation processing requires process context, bounce */
4344 static void css_killed_ref_fn(struct percpu_ref *ref)
4346 struct cgroup_subsys_state *css =
4347 container_of(ref, struct cgroup_subsys_state, refcnt);
4349 INIT_WORK(&css->destroy_work, css_killed_work_fn);
4350 queue_work(cgroup_destroy_wq, &css->destroy_work);
4354 * kill_css - destroy a css
4355 * @css: css to destroy
4357 * This function initiates destruction of @css by removing cgroup interface
4358 * files and putting its base reference. ->css_offline() will be invoked
4359 * asynchronously once css_tryget() is guaranteed to fail and when the
4360 * reference count reaches zero, @css will be released.
4362 static void kill_css(struct cgroup_subsys_state *css)
4364 lockdep_assert_held(&cgroup_tree_mutex);
4367 * This must happen before css is disassociated with its cgroup.
4368 * See seq_css() for details.
4370 cgroup_clear_dir(css->cgroup, 1 << css->ss->id);
4373 * Killing would put the base ref, but we need to keep it alive
4374 * until after ->css_offline().
4379 * cgroup core guarantees that, by the time ->css_offline() is
4380 * invoked, no new css reference will be given out via
4381 * css_tryget(). We can't simply call percpu_ref_kill() and
4382 * proceed to offlining css's because percpu_ref_kill() doesn't
4383 * guarantee that the ref is seen as killed on all CPUs on return.
4385 * Use percpu_ref_kill_and_confirm() to get notifications as each
4386 * css is confirmed to be seen as killed on all CPUs.
4388 percpu_ref_kill_and_confirm(&css->refcnt, css_killed_ref_fn);
4392 * cgroup_destroy_locked - the first stage of cgroup destruction
4393 * @cgrp: cgroup to be destroyed
4395 * css's make use of percpu refcnts whose killing latency shouldn't be
4396 * exposed to userland and are RCU protected. Also, cgroup core needs to
4397 * guarantee that css_tryget() won't succeed by the time ->css_offline() is
4398 * invoked. To satisfy all the requirements, destruction is implemented in
4399 * the following two steps.
4401 * s1. Verify @cgrp can be destroyed and mark it dying. Remove all
4402 * userland visible parts and start killing the percpu refcnts of
4403 * css's. Set up so that the next stage will be kicked off once all
4404 * the percpu refcnts are confirmed to be killed.
4406 * s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the
4407 * rest of destruction. Once all cgroup references are gone, the
4408 * cgroup is RCU-freed.
4410 * This function implements s1. After this step, @cgrp is gone as far as
4411 * the userland is concerned and a new cgroup with the same name may be
4412 * created. As cgroup doesn't care about the names internally, this
4413 * doesn't cause any problem.
4415 static int cgroup_destroy_locked(struct cgroup *cgrp)
4416 __releases(&cgroup_mutex) __acquires(&cgroup_mutex)
4418 struct cgroup *child;
4419 struct cgroup_subsys_state *css;
4423 lockdep_assert_held(&cgroup_tree_mutex);
4424 lockdep_assert_held(&cgroup_mutex);
4427 * css_set_rwsem synchronizes access to ->cset_links and prevents
4428 * @cgrp from being removed while put_css_set() is in progress.
4430 down_read(&css_set_rwsem);
4431 empty = list_empty(&cgrp->cset_links);
4432 up_read(&css_set_rwsem);
4437 * Make sure there's no live children. We can't test ->children
4438 * emptiness as dead children linger on it while being destroyed;
4439 * otherwise, "rmdir parent/child parent" may fail with -EBUSY.
4443 list_for_each_entry_rcu(child, &cgrp->children, sibling) {
4444 empty = cgroup_is_dead(child);
4453 * Mark @cgrp dead. This prevents further task migration and child
4454 * creation by disabling cgroup_lock_live_group(). Note that
4455 * CGRP_DEAD assertion is depended upon by css_next_child() to
4456 * resume iteration after dropping RCU read lock. See
4457 * css_next_child() for details.
4459 set_bit(CGRP_DEAD, &cgrp->flags);
4462 * Initiate massacre of all css's. cgroup_destroy_css_killed()
4463 * will be invoked to perform the rest of destruction once the
4464 * percpu refs of all css's are confirmed to be killed. This
4465 * involves removing the subsystem's files, drop cgroup_mutex.
4467 mutex_unlock(&cgroup_mutex);
4468 for_each_css(css, ssid, cgrp)
4470 mutex_lock(&cgroup_mutex);
4472 /* CGRP_DEAD is set, remove from ->release_list for the last time */
4473 raw_spin_lock(&release_list_lock);
4474 if (!list_empty(&cgrp->release_list))
4475 list_del_init(&cgrp->release_list);
4476 raw_spin_unlock(&release_list_lock);
4479 * If @cgrp has css's attached, the second stage of cgroup
4480 * destruction is kicked off from css_killed_work_fn() after the
4481 * refs of all attached css's are killed. If @cgrp doesn't have
4482 * any css, we kick it off here.
4485 cgroup_destroy_css_killed(cgrp);
4487 /* remove @cgrp directory along with the base files */
4488 mutex_unlock(&cgroup_mutex);
4491 * There are two control paths which try to determine cgroup from
4492 * dentry without going through kernfs - cgroupstats_build() and
4493 * css_tryget_from_dir(). Those are supported by RCU protecting
4494 * clearing of cgrp->kn->priv backpointer, which should happen
4495 * after all files under it have been removed.
4497 kernfs_remove(cgrp->kn); /* @cgrp has an extra ref on its kn */
4498 RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv, NULL);
4500 mutex_lock(&cgroup_mutex);
4506 * cgroup_destroy_css_killed - the second step of cgroup destruction
4507 * @work: cgroup->destroy_free_work
4509 * This function is invoked from a work item for a cgroup which is being
4510 * destroyed after all css's are offlined and performs the rest of
4511 * destruction. This is the second step of destruction described in the
4512 * comment above cgroup_destroy_locked().
4514 static void cgroup_destroy_css_killed(struct cgroup *cgrp)
4516 struct cgroup *parent = cgrp->parent;
4518 lockdep_assert_held(&cgroup_tree_mutex);
4519 lockdep_assert_held(&cgroup_mutex);
4521 /* delete this cgroup from parent->children */
4522 list_del_rcu(&cgrp->sibling);
4526 set_bit(CGRP_RELEASABLE, &parent->flags);
4527 check_for_release(parent);
4530 static int cgroup_rmdir(struct kernfs_node *kn)
4532 struct cgroup *cgrp = kn->priv;
4536 * This is self-destruction but @kn can't be removed while this
4537 * callback is in progress. Let's break active protection. Once
4538 * the protection is broken, @cgrp can be destroyed at any point.
4539 * Pin it so that it stays accessible.
4542 kernfs_break_active_protection(kn);
4544 mutex_lock(&cgroup_tree_mutex);
4545 mutex_lock(&cgroup_mutex);
4548 * @cgrp might already have been destroyed while we're trying to
4551 if (!cgroup_is_dead(cgrp))
4552 ret = cgroup_destroy_locked(cgrp);
4554 mutex_unlock(&cgroup_mutex);
4555 mutex_unlock(&cgroup_tree_mutex);
4557 kernfs_unbreak_active_protection(kn);
4562 static struct kernfs_syscall_ops cgroup_kf_syscall_ops = {
4563 .remount_fs = cgroup_remount,
4564 .show_options = cgroup_show_options,
4565 .mkdir = cgroup_mkdir,
4566 .rmdir = cgroup_rmdir,
4567 .rename = cgroup_rename,
4570 static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
4572 struct cgroup_subsys_state *css;
4574 printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
4576 mutex_lock(&cgroup_tree_mutex);
4577 mutex_lock(&cgroup_mutex);
4579 INIT_LIST_HEAD(&ss->cfts);
4581 /* Create the root cgroup state for this subsystem */
4582 ss->root = &cgrp_dfl_root;
4583 css = ss->css_alloc(cgroup_css(&cgrp_dfl_root.cgrp, ss));
4584 /* We don't handle early failures gracefully */
4585 BUG_ON(IS_ERR(css));
4586 init_css(css, ss, &cgrp_dfl_root.cgrp);
4588 /* Update the init_css_set to contain a subsys
4589 * pointer to this state - since the subsystem is
4590 * newly registered, all tasks and hence the
4591 * init_css_set is in the subsystem's root cgroup. */
4592 init_css_set.subsys[ss->id] = css;
4594 need_forkexit_callback |= ss->fork || ss->exit;
4596 /* At system boot, before all subsystems have been
4597 * registered, no tasks have been forked, so we don't
4598 * need to invoke fork callbacks here. */
4599 BUG_ON(!list_empty(&init_task.tasks));
4601 BUG_ON(online_css(css));
4603 cgrp_dfl_root.subsys_mask |= 1 << ss->id;
4605 mutex_unlock(&cgroup_mutex);
4606 mutex_unlock(&cgroup_tree_mutex);
4610 * cgroup_init_early - cgroup initialization at system boot
4612 * Initialize cgroups at system boot, and initialize any
4613 * subsystems that request early init.
4615 int __init cgroup_init_early(void)
4617 static struct cgroup_sb_opts __initdata opts =
4618 { .flags = CGRP_ROOT_SANE_BEHAVIOR };
4619 struct cgroup_subsys *ss;
4622 init_cgroup_root(&cgrp_dfl_root, &opts);
4623 RCU_INIT_POINTER(init_task.cgroups, &init_css_set);
4625 for_each_subsys(ss, i) {
4626 WARN(!ss->css_alloc || !ss->css_free || ss->name || ss->id,
4627 "invalid cgroup_subsys %d:%s css_alloc=%p css_free=%p name:id=%d:%s\n",
4628 i, cgroup_subsys_name[i], ss->css_alloc, ss->css_free,
4630 WARN(strlen(cgroup_subsys_name[i]) > MAX_CGROUP_TYPE_NAMELEN,
4631 "cgroup_subsys_name %s too long\n", cgroup_subsys_name[i]);
4634 ss->name = cgroup_subsys_name[i];
4637 cgroup_init_subsys(ss);
4643 * cgroup_init - cgroup initialization
4645 * Register cgroup filesystem and /proc file, and initialize
4646 * any subsystems that didn't request early init.
4648 int __init cgroup_init(void)
4650 struct cgroup_subsys *ss;
4654 BUG_ON(cgroup_init_cftypes(NULL, cgroup_base_files));
4656 mutex_lock(&cgroup_tree_mutex);
4657 mutex_lock(&cgroup_mutex);
4659 /* Add init_css_set to the hash table */
4660 key = css_set_hash(init_css_set.subsys);
4661 hash_add(css_set_table, &init_css_set.hlist, key);
4663 BUG_ON(cgroup_setup_root(&cgrp_dfl_root, 0));
4665 mutex_unlock(&cgroup_mutex);
4666 mutex_unlock(&cgroup_tree_mutex);
4668 for_each_subsys(ss, ssid) {
4669 if (!ss->early_init)
4670 cgroup_init_subsys(ss);
4672 list_add_tail(&init_css_set.e_cset_node[ssid],
4673 &cgrp_dfl_root.cgrp.e_csets[ssid]);
4676 * cftype registration needs kmalloc and can't be done
4677 * during early_init. Register base cftypes separately.
4679 if (ss->base_cftypes)
4680 WARN_ON(cgroup_add_cftypes(ss, ss->base_cftypes));
4683 cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
4687 err = register_filesystem(&cgroup_fs_type);
4689 kobject_put(cgroup_kobj);
4693 proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
4697 static int __init cgroup_wq_init(void)
4700 * There isn't much point in executing destruction path in
4701 * parallel. Good chunk is serialized with cgroup_mutex anyway.
4702 * Use 1 for @max_active.
4704 * We would prefer to do this in cgroup_init() above, but that
4705 * is called before init_workqueues(): so leave this until after.
4707 cgroup_destroy_wq = alloc_workqueue("cgroup_destroy", 0, 1);
4708 BUG_ON(!cgroup_destroy_wq);
4711 * Used to destroy pidlists and separate to serve as flush domain.
4712 * Cap @max_active to 1 too.
4714 cgroup_pidlist_destroy_wq = alloc_workqueue("cgroup_pidlist_destroy",
4716 BUG_ON(!cgroup_pidlist_destroy_wq);
4720 core_initcall(cgroup_wq_init);
4723 * proc_cgroup_show()
4724 * - Print task's cgroup paths into seq_file, one line for each hierarchy
4725 * - Used for /proc/<pid>/cgroup.
4728 /* TODO: Use a proper seq_file iterator */
4729 int proc_cgroup_show(struct seq_file *m, void *v)
4732 struct task_struct *tsk;
4735 struct cgroup_root *root;
4738 buf = kmalloc(PATH_MAX, GFP_KERNEL);
4744 tsk = get_pid_task(pid, PIDTYPE_PID);
4750 mutex_lock(&cgroup_mutex);
4751 down_read(&css_set_rwsem);
4753 for_each_root(root) {
4754 struct cgroup_subsys *ss;
4755 struct cgroup *cgrp;
4756 int ssid, count = 0;
4758 if (root == &cgrp_dfl_root && !cgrp_dfl_root_visible)
4761 seq_printf(m, "%d:", root->hierarchy_id);
4762 for_each_subsys(ss, ssid)
4763 if (root->subsys_mask & (1 << ssid))
4764 seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
4765 if (strlen(root->name))
4766 seq_printf(m, "%sname=%s", count ? "," : "",
4769 cgrp = task_cgroup_from_root(tsk, root);
4770 path = cgroup_path(cgrp, buf, PATH_MAX);
4772 retval = -ENAMETOOLONG;
4780 up_read(&css_set_rwsem);
4781 mutex_unlock(&cgroup_mutex);
4782 put_task_struct(tsk);
4789 /* Display information about each subsystem and each hierarchy */
4790 static int proc_cgroupstats_show(struct seq_file *m, void *v)
4792 struct cgroup_subsys *ss;
4795 seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
4797 * ideally we don't want subsystems moving around while we do this.
4798 * cgroup_mutex is also necessary to guarantee an atomic snapshot of
4799 * subsys/hierarchy state.
4801 mutex_lock(&cgroup_mutex);
4803 for_each_subsys(ss, i)
4804 seq_printf(m, "%s\t%d\t%d\t%d\n",
4805 ss->name, ss->root->hierarchy_id,
4806 atomic_read(&ss->root->nr_cgrps), !ss->disabled);
4808 mutex_unlock(&cgroup_mutex);
4812 static int cgroupstats_open(struct inode *inode, struct file *file)
4814 return single_open(file, proc_cgroupstats_show, NULL);
4817 static const struct file_operations proc_cgroupstats_operations = {
4818 .open = cgroupstats_open,
4820 .llseek = seq_lseek,
4821 .release = single_release,
4825 * cgroup_fork - initialize cgroup related fields during copy_process()
4826 * @child: pointer to task_struct of forking parent process.
4828 * A task is associated with the init_css_set until cgroup_post_fork()
4829 * attaches it to the parent's css_set. Empty cg_list indicates that
4830 * @child isn't holding reference to its css_set.
4832 void cgroup_fork(struct task_struct *child)
4834 RCU_INIT_POINTER(child->cgroups, &init_css_set);
4835 INIT_LIST_HEAD(&child->cg_list);
4839 * cgroup_post_fork - called on a new task after adding it to the task list
4840 * @child: the task in question
4842 * Adds the task to the list running through its css_set if necessary and
4843 * call the subsystem fork() callbacks. Has to be after the task is
4844 * visible on the task list in case we race with the first call to
4845 * cgroup_task_iter_start() - to guarantee that the new task ends up on its
4848 void cgroup_post_fork(struct task_struct *child)
4850 struct cgroup_subsys *ss;
4854 * This may race against cgroup_enable_task_cg_links(). As that
4855 * function sets use_task_css_set_links before grabbing
4856 * tasklist_lock and we just went through tasklist_lock to add
4857 * @child, it's guaranteed that either we see the set
4858 * use_task_css_set_links or cgroup_enable_task_cg_lists() sees
4859 * @child during its iteration.
4861 * If we won the race, @child is associated with %current's
4862 * css_set. Grabbing css_set_rwsem guarantees both that the
4863 * association is stable, and, on completion of the parent's
4864 * migration, @child is visible in the source of migration or
4865 * already in the destination cgroup. This guarantee is necessary
4866 * when implementing operations which need to migrate all tasks of
4867 * a cgroup to another.
4869 * Note that if we lose to cgroup_enable_task_cg_links(), @child
4870 * will remain in init_css_set. This is safe because all tasks are
4871 * in the init_css_set before cg_links is enabled and there's no
4872 * operation which transfers all tasks out of init_css_set.
4874 if (use_task_css_set_links) {
4875 struct css_set *cset;
4877 down_write(&css_set_rwsem);
4878 cset = task_css_set(current);
4879 if (list_empty(&child->cg_list)) {
4880 rcu_assign_pointer(child->cgroups, cset);
4881 list_add(&child->cg_list, &cset->tasks);
4884 up_write(&css_set_rwsem);
4888 * Call ss->fork(). This must happen after @child is linked on
4889 * css_set; otherwise, @child might change state between ->fork()
4890 * and addition to css_set.
4892 if (need_forkexit_callback) {
4893 for_each_subsys(ss, i)
4900 * cgroup_exit - detach cgroup from exiting task
4901 * @tsk: pointer to task_struct of exiting process
4903 * Description: Detach cgroup from @tsk and release it.
4905 * Note that cgroups marked notify_on_release force every task in
4906 * them to take the global cgroup_mutex mutex when exiting.
4907 * This could impact scaling on very large systems. Be reluctant to
4908 * use notify_on_release cgroups where very high task exit scaling
4909 * is required on large systems.
4911 * We set the exiting tasks cgroup to the root cgroup (top_cgroup). We
4912 * call cgroup_exit() while the task is still competent to handle
4913 * notify_on_release(), then leave the task attached to the root cgroup in
4914 * each hierarchy for the remainder of its exit. No need to bother with
4915 * init_css_set refcnting. init_css_set never goes away and we can't race
4916 * with migration path - PF_EXITING is visible to migration path.
4918 void cgroup_exit(struct task_struct *tsk)
4920 struct cgroup_subsys *ss;
4921 struct css_set *cset;
4922 bool put_cset = false;
4926 * Unlink from @tsk from its css_set. As migration path can't race
4927 * with us, we can check cg_list without grabbing css_set_rwsem.
4929 if (!list_empty(&tsk->cg_list)) {
4930 down_write(&css_set_rwsem);
4931 list_del_init(&tsk->cg_list);
4932 up_write(&css_set_rwsem);
4936 /* Reassign the task to the init_css_set. */
4937 cset = task_css_set(tsk);
4938 RCU_INIT_POINTER(tsk->cgroups, &init_css_set);
4940 if (need_forkexit_callback) {
4941 /* see cgroup_post_fork() for details */
4942 for_each_subsys(ss, i) {
4944 struct cgroup_subsys_state *old_css = cset->subsys[i];
4945 struct cgroup_subsys_state *css = task_css(tsk, i);
4947 ss->exit(css, old_css, tsk);
4953 put_css_set(cset, true);
4956 static void check_for_release(struct cgroup *cgrp)
4958 if (cgroup_is_releasable(cgrp) &&
4959 list_empty(&cgrp->cset_links) && list_empty(&cgrp->children)) {
4961 * Control Group is currently removeable. If it's not
4962 * already queued for a userspace notification, queue
4965 int need_schedule_work = 0;
4967 raw_spin_lock(&release_list_lock);
4968 if (!cgroup_is_dead(cgrp) &&
4969 list_empty(&cgrp->release_list)) {
4970 list_add(&cgrp->release_list, &release_list);
4971 need_schedule_work = 1;
4973 raw_spin_unlock(&release_list_lock);
4974 if (need_schedule_work)
4975 schedule_work(&release_agent_work);
4980 * Notify userspace when a cgroup is released, by running the
4981 * configured release agent with the name of the cgroup (path
4982 * relative to the root of cgroup file system) as the argument.
4984 * Most likely, this user command will try to rmdir this cgroup.
4986 * This races with the possibility that some other task will be
4987 * attached to this cgroup before it is removed, or that some other
4988 * user task will 'mkdir' a child cgroup of this cgroup. That's ok.
4989 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
4990 * unused, and this cgroup will be reprieved from its death sentence,
4991 * to continue to serve a useful existence. Next time it's released,
4992 * we will get notified again, if it still has 'notify_on_release' set.
4994 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
4995 * means only wait until the task is successfully execve()'d. The
4996 * separate release agent task is forked by call_usermodehelper(),
4997 * then control in this thread returns here, without waiting for the
4998 * release agent task. We don't bother to wait because the caller of
4999 * this routine has no use for the exit status of the release agent
5000 * task, so no sense holding our caller up for that.
5002 static void cgroup_release_agent(struct work_struct *work)
5004 BUG_ON(work != &release_agent_work);
5005 mutex_lock(&cgroup_mutex);
5006 raw_spin_lock(&release_list_lock);
5007 while (!list_empty(&release_list)) {
5008 char *argv[3], *envp[3];
5010 char *pathbuf = NULL, *agentbuf = NULL, *path;
5011 struct cgroup *cgrp = list_entry(release_list.next,
5014 list_del_init(&cgrp->release_list);
5015 raw_spin_unlock(&release_list_lock);
5016 pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
5019 path = cgroup_path(cgrp, pathbuf, PATH_MAX);
5022 agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
5027 argv[i++] = agentbuf;
5032 /* minimal command environment */
5033 envp[i++] = "HOME=/";
5034 envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
5037 /* Drop the lock while we invoke the usermode helper,
5038 * since the exec could involve hitting disk and hence
5039 * be a slow process */
5040 mutex_unlock(&cgroup_mutex);
5041 call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
5042 mutex_lock(&cgroup_mutex);
5046 raw_spin_lock(&release_list_lock);
5048 raw_spin_unlock(&release_list_lock);
5049 mutex_unlock(&cgroup_mutex);
5052 static int __init cgroup_disable(char *str)
5054 struct cgroup_subsys *ss;
5058 while ((token = strsep(&str, ",")) != NULL) {
5062 for_each_subsys(ss, i) {
5063 if (!strcmp(token, ss->name)) {
5065 printk(KERN_INFO "Disabling %s control group"
5066 " subsystem\n", ss->name);
5073 __setup("cgroup_disable=", cgroup_disable);
5076 * css_tryget_from_dir - get corresponding css from the dentry of a cgroup dir
5077 * @dentry: directory dentry of interest
5078 * @ss: subsystem of interest
5080 * If @dentry is a directory for a cgroup which has @ss enabled on it, try
5081 * to get the corresponding css and return it. If such css doesn't exist
5082 * or can't be pinned, an ERR_PTR value is returned.
5084 struct cgroup_subsys_state *css_tryget_from_dir(struct dentry *dentry,
5085 struct cgroup_subsys *ss)
5087 struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
5088 struct cgroup_subsys_state *css = NULL;
5089 struct cgroup *cgrp;
5091 /* is @dentry a cgroup dir? */
5092 if (dentry->d_sb->s_type != &cgroup_fs_type || !kn ||
5093 kernfs_type(kn) != KERNFS_DIR)
5094 return ERR_PTR(-EBADF);
5099 * This path doesn't originate from kernfs and @kn could already
5100 * have been or be removed at any point. @kn->priv is RCU
5101 * protected for this access. See destroy_locked() for details.
5103 cgrp = rcu_dereference(kn->priv);
5105 css = cgroup_css(cgrp, ss);
5107 if (!css || !css_tryget(css))
5108 css = ERR_PTR(-ENOENT);
5115 * css_from_id - lookup css by id
5116 * @id: the cgroup id
5117 * @ss: cgroup subsys to be looked into
5119 * Returns the css if there's valid one with @id, otherwise returns NULL.
5120 * Should be called under rcu_read_lock().
5122 struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss)
5124 struct cgroup *cgrp;
5126 cgroup_assert_mutexes_or_rcu_locked();
5128 cgrp = idr_find(&ss->root->cgroup_idr, id);
5130 return cgroup_css(cgrp, ss);
5134 #ifdef CONFIG_CGROUP_DEBUG
5135 static struct cgroup_subsys_state *
5136 debug_css_alloc(struct cgroup_subsys_state *parent_css)
5138 struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);
5141 return ERR_PTR(-ENOMEM);
5146 static void debug_css_free(struct cgroup_subsys_state *css)
5151 static u64 debug_taskcount_read(struct cgroup_subsys_state *css,
5154 return cgroup_task_count(css->cgroup);
5157 static u64 current_css_set_read(struct cgroup_subsys_state *css,
5160 return (u64)(unsigned long)current->cgroups;
5163 static u64 current_css_set_refcount_read(struct cgroup_subsys_state *css,
5169 count = atomic_read(&task_css_set(current)->refcount);
5174 static int current_css_set_cg_links_read(struct seq_file *seq, void *v)
5176 struct cgrp_cset_link *link;
5177 struct css_set *cset;
5180 name_buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
5184 down_read(&css_set_rwsem);
5186 cset = rcu_dereference(current->cgroups);
5187 list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
5188 struct cgroup *c = link->cgrp;
5190 cgroup_name(c, name_buf, NAME_MAX + 1);
5191 seq_printf(seq, "Root %d group %s\n",
5192 c->root->hierarchy_id, name_buf);
5195 up_read(&css_set_rwsem);
5200 #define MAX_TASKS_SHOWN_PER_CSS 25
5201 static int cgroup_css_links_read(struct seq_file *seq, void *v)
5203 struct cgroup_subsys_state *css = seq_css(seq);
5204 struct cgrp_cset_link *link;
5206 down_read(&css_set_rwsem);
5207 list_for_each_entry(link, &css->cgroup->cset_links, cset_link) {
5208 struct css_set *cset = link->cset;
5209 struct task_struct *task;
5212 seq_printf(seq, "css_set %p\n", cset);
5214 list_for_each_entry(task, &cset->tasks, cg_list) {
5215 if (count++ > MAX_TASKS_SHOWN_PER_CSS)
5217 seq_printf(seq, " task %d\n", task_pid_vnr(task));
5220 list_for_each_entry(task, &cset->mg_tasks, cg_list) {
5221 if (count++ > MAX_TASKS_SHOWN_PER_CSS)
5223 seq_printf(seq, " task %d\n", task_pid_vnr(task));
5227 seq_puts(seq, " ...\n");
5229 up_read(&css_set_rwsem);
5233 static u64 releasable_read(struct cgroup_subsys_state *css, struct cftype *cft)
5235 return test_bit(CGRP_RELEASABLE, &css->cgroup->flags);
5238 static struct cftype debug_files[] = {
5240 .name = "taskcount",
5241 .read_u64 = debug_taskcount_read,
5245 .name = "current_css_set",
5246 .read_u64 = current_css_set_read,
5250 .name = "current_css_set_refcount",
5251 .read_u64 = current_css_set_refcount_read,
5255 .name = "current_css_set_cg_links",
5256 .seq_show = current_css_set_cg_links_read,
5260 .name = "cgroup_css_links",
5261 .seq_show = cgroup_css_links_read,
5265 .name = "releasable",
5266 .read_u64 = releasable_read,
5272 struct cgroup_subsys debug_cgrp_subsys = {
5273 .css_alloc = debug_css_alloc,
5274 .css_free = debug_css_free,
5275 .base_cftypes = debug_files,
5277 #endif /* CONFIG_CGROUP_DEBUG */