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 cgroup_addrm_files(struct cgroup
*cgrp
, struct cftype cfts
[],
187 static void cgroup_pidlist_destroy_all(struct cgroup
*cgrp
);
190 * cgroup_css - obtain a cgroup's css for the specified subsystem
191 * @cgrp: the cgroup of interest
192 * @ss: the subsystem of interest (%NULL returns the dummy_css)
194 * Return @cgrp's css (cgroup_subsys_state) associated with @ss. This
195 * function must be called either under cgroup_mutex or rcu_read_lock() and
196 * the caller is responsible for pinning the returned css if it wants to
197 * keep accessing it outside the said locks. This function may return
198 * %NULL if @cgrp doesn't have @subsys_id enabled.
200 static struct cgroup_subsys_state
*cgroup_css(struct cgroup
*cgrp
,
201 struct cgroup_subsys
*ss
)
204 return rcu_dereference_check(cgrp
->subsys
[ss
->id
],
205 lockdep_is_held(&cgroup_tree_mutex
) ||
206 lockdep_is_held(&cgroup_mutex
));
208 return &cgrp
->dummy_css
;
212 * cgroup_e_css - obtain a cgroup's effective css for the specified subsystem
213 * @cgrp: the cgroup of interest
214 * @ss: the subsystem of interest (%NULL returns the dummy_css)
216 * Similar to cgroup_css() but returns the effctive css, which is defined
217 * as the matching css of the nearest ancestor including self which has @ss
218 * enabled. If @ss is associated with the hierarchy @cgrp is on, this
219 * function is guaranteed to return non-NULL css.
221 static struct cgroup_subsys_state
*cgroup_e_css(struct cgroup
*cgrp
,
222 struct cgroup_subsys
*ss
)
224 lockdep_assert_held(&cgroup_mutex
);
227 return &cgrp
->dummy_css
;
229 if (!(cgrp
->root
->subsys_mask
& (1 << ss
->id
)))
232 while (cgrp
->parent
&&
233 !(cgrp
->parent
->child_subsys_mask
& (1 << ss
->id
)))
236 return cgroup_css(cgrp
, ss
);
239 /* convenient tests for these bits */
240 static inline bool cgroup_is_dead(const struct cgroup
*cgrp
)
242 return test_bit(CGRP_DEAD
, &cgrp
->flags
);
245 struct cgroup_subsys_state
*seq_css(struct seq_file
*seq
)
247 struct kernfs_open_file
*of
= seq
->private;
248 struct cgroup
*cgrp
= of
->kn
->parent
->priv
;
249 struct cftype
*cft
= seq_cft(seq
);
252 * This is open and unprotected implementation of cgroup_css().
253 * seq_css() is only called from a kernfs file operation which has
254 * an active reference on the file. Because all the subsystem
255 * files are drained before a css is disassociated with a cgroup,
256 * the matching css from the cgroup's subsys table is guaranteed to
257 * be and stay valid until the enclosing operation is complete.
260 return rcu_dereference_raw(cgrp
->subsys
[cft
->ss
->id
]);
262 return &cgrp
->dummy_css
;
264 EXPORT_SYMBOL_GPL(seq_css
);
267 * cgroup_is_descendant - test ancestry
268 * @cgrp: the cgroup to be tested
269 * @ancestor: possible ancestor of @cgrp
271 * Test whether @cgrp is a descendant of @ancestor. It also returns %true
272 * if @cgrp == @ancestor. This function is safe to call as long as @cgrp
273 * and @ancestor are accessible.
275 bool cgroup_is_descendant(struct cgroup
*cgrp
, struct cgroup
*ancestor
)
278 if (cgrp
== ancestor
)
285 static int cgroup_is_releasable(const struct cgroup
*cgrp
)
288 (1 << CGRP_RELEASABLE
) |
289 (1 << CGRP_NOTIFY_ON_RELEASE
);
290 return (cgrp
->flags
& bits
) == bits
;
293 static int notify_on_release(const struct cgroup
*cgrp
)
295 return test_bit(CGRP_NOTIFY_ON_RELEASE
, &cgrp
->flags
);
299 * for_each_css - iterate all css's of a cgroup
300 * @css: the iteration cursor
301 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
302 * @cgrp: the target cgroup to iterate css's of
304 * Should be called under cgroup_[tree_]mutex.
306 #define for_each_css(css, ssid, cgrp) \
307 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
308 if (!((css) = rcu_dereference_check( \
309 (cgrp)->subsys[(ssid)], \
310 lockdep_is_held(&cgroup_tree_mutex) || \
311 lockdep_is_held(&cgroup_mutex)))) { } \
315 * for_each_e_css - iterate all effective css's of a cgroup
316 * @css: the iteration cursor
317 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
318 * @cgrp: the target cgroup to iterate css's of
320 * Should be called under cgroup_[tree_]mutex.
322 #define for_each_e_css(css, ssid, cgrp) \
323 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
324 if (!((css) = cgroup_e_css(cgrp, cgroup_subsys[(ssid)]))) \
329 * for_each_subsys - iterate all enabled cgroup subsystems
330 * @ss: the iteration cursor
331 * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
333 #define for_each_subsys(ss, ssid) \
334 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT && \
335 (((ss) = cgroup_subsys[ssid]) || true); (ssid)++)
337 /* iterate across the hierarchies */
338 #define for_each_root(root) \
339 list_for_each_entry((root), &cgroup_roots, root_list)
342 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
343 * @cgrp: the cgroup to be checked for liveness
345 * On success, returns true; the mutex should be later unlocked. On
346 * failure returns false with no lock held.
348 static bool cgroup_lock_live_group(struct cgroup
*cgrp
)
350 mutex_lock(&cgroup_mutex
);
351 if (cgroup_is_dead(cgrp
)) {
352 mutex_unlock(&cgroup_mutex
);
358 /* the list of cgroups eligible for automatic release. Protected by
359 * release_list_lock */
360 static LIST_HEAD(release_list
);
361 static DEFINE_RAW_SPINLOCK(release_list_lock
);
362 static void cgroup_release_agent(struct work_struct
*work
);
363 static DECLARE_WORK(release_agent_work
, cgroup_release_agent
);
364 static void check_for_release(struct cgroup
*cgrp
);
367 * A cgroup can be associated with multiple css_sets as different tasks may
368 * belong to different cgroups on different hierarchies. In the other
369 * direction, a css_set is naturally associated with multiple cgroups.
370 * This M:N relationship is represented by the following link structure
371 * which exists for each association and allows traversing the associations
374 struct cgrp_cset_link
{
375 /* the cgroup and css_set this link associates */
377 struct css_set
*cset
;
379 /* list of cgrp_cset_links anchored at cgrp->cset_links */
380 struct list_head cset_link
;
382 /* list of cgrp_cset_links anchored at css_set->cgrp_links */
383 struct list_head cgrp_link
;
387 * The default css_set - used by init and its children prior to any
388 * hierarchies being mounted. It contains a pointer to the root state
389 * for each subsystem. Also used to anchor the list of css_sets. Not
390 * reference-counted, to improve performance when child cgroups
391 * haven't been created.
393 static struct css_set init_css_set
= {
394 .refcount
= ATOMIC_INIT(1),
395 .cgrp_links
= LIST_HEAD_INIT(init_css_set
.cgrp_links
),
396 .tasks
= LIST_HEAD_INIT(init_css_set
.tasks
),
397 .mg_tasks
= LIST_HEAD_INIT(init_css_set
.mg_tasks
),
398 .mg_preload_node
= LIST_HEAD_INIT(init_css_set
.mg_preload_node
),
399 .mg_node
= LIST_HEAD_INIT(init_css_set
.mg_node
),
402 static int css_set_count
= 1; /* 1 for init_css_set */
405 * hash table for cgroup groups. This improves the performance to find
406 * an existing css_set. This hash doesn't (currently) take into
407 * account cgroups in empty hierarchies.
409 #define CSS_SET_HASH_BITS 7
410 static DEFINE_HASHTABLE(css_set_table
, CSS_SET_HASH_BITS
);
412 static unsigned long css_set_hash(struct cgroup_subsys_state
*css
[])
414 unsigned long key
= 0UL;
415 struct cgroup_subsys
*ss
;
418 for_each_subsys(ss
, i
)
419 key
+= (unsigned long)css
[i
];
420 key
= (key
>> 16) ^ key
;
425 static void put_css_set_locked(struct css_set
*cset
, bool taskexit
)
427 struct cgrp_cset_link
*link
, *tmp_link
;
428 struct cgroup_subsys
*ss
;
431 lockdep_assert_held(&css_set_rwsem
);
433 if (!atomic_dec_and_test(&cset
->refcount
))
436 /* This css_set is dead. unlink it and release cgroup refcounts */
437 for_each_subsys(ss
, ssid
)
438 list_del(&cset
->e_cset_node
[ssid
]);
439 hash_del(&cset
->hlist
);
442 list_for_each_entry_safe(link
, tmp_link
, &cset
->cgrp_links
, cgrp_link
) {
443 struct cgroup
*cgrp
= link
->cgrp
;
445 list_del(&link
->cset_link
);
446 list_del(&link
->cgrp_link
);
448 /* @cgrp can't go away while we're holding css_set_rwsem */
449 if (list_empty(&cgrp
->cset_links
) && notify_on_release(cgrp
)) {
451 set_bit(CGRP_RELEASABLE
, &cgrp
->flags
);
452 check_for_release(cgrp
);
458 kfree_rcu(cset
, rcu_head
);
461 static void put_css_set(struct css_set
*cset
, bool taskexit
)
464 * Ensure that the refcount doesn't hit zero while any readers
465 * can see it. Similar to atomic_dec_and_lock(), but for an
468 if (atomic_add_unless(&cset
->refcount
, -1, 1))
471 down_write(&css_set_rwsem
);
472 put_css_set_locked(cset
, taskexit
);
473 up_write(&css_set_rwsem
);
477 * refcounted get/put for css_set objects
479 static inline void get_css_set(struct css_set
*cset
)
481 atomic_inc(&cset
->refcount
);
485 * compare_css_sets - helper function for find_existing_css_set().
486 * @cset: candidate css_set being tested
487 * @old_cset: existing css_set for a task
488 * @new_cgrp: cgroup that's being entered by the task
489 * @template: desired set of css pointers in css_set (pre-calculated)
491 * Returns true if "cset" matches "old_cset" except for the hierarchy
492 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
494 static bool compare_css_sets(struct css_set
*cset
,
495 struct css_set
*old_cset
,
496 struct cgroup
*new_cgrp
,
497 struct cgroup_subsys_state
*template[])
499 struct list_head
*l1
, *l2
;
502 * On the default hierarchy, there can be csets which are
503 * associated with the same set of cgroups but different csses.
504 * Let's first ensure that csses match.
506 if (memcmp(template, cset
->subsys
, sizeof(cset
->subsys
)))
510 * Compare cgroup pointers in order to distinguish between
511 * different cgroups in hierarchies. As different cgroups may
512 * share the same effective css, this comparison is always
515 l1
= &cset
->cgrp_links
;
516 l2
= &old_cset
->cgrp_links
;
518 struct cgrp_cset_link
*link1
, *link2
;
519 struct cgroup
*cgrp1
, *cgrp2
;
523 /* See if we reached the end - both lists are equal length. */
524 if (l1
== &cset
->cgrp_links
) {
525 BUG_ON(l2
!= &old_cset
->cgrp_links
);
528 BUG_ON(l2
== &old_cset
->cgrp_links
);
530 /* Locate the cgroups associated with these links. */
531 link1
= list_entry(l1
, struct cgrp_cset_link
, cgrp_link
);
532 link2
= list_entry(l2
, struct cgrp_cset_link
, cgrp_link
);
535 /* Hierarchies should be linked in the same order. */
536 BUG_ON(cgrp1
->root
!= cgrp2
->root
);
539 * If this hierarchy is the hierarchy of the cgroup
540 * that's changing, then we need to check that this
541 * css_set points to the new cgroup; if it's any other
542 * hierarchy, then this css_set should point to the
543 * same cgroup as the old css_set.
545 if (cgrp1
->root
== new_cgrp
->root
) {
546 if (cgrp1
!= new_cgrp
)
557 * find_existing_css_set - init css array and find the matching css_set
558 * @old_cset: the css_set that we're using before the cgroup transition
559 * @cgrp: the cgroup that we're moving into
560 * @template: out param for the new set of csses, should be clear on entry
562 static struct css_set
*find_existing_css_set(struct css_set
*old_cset
,
564 struct cgroup_subsys_state
*template[])
566 struct cgroup_root
*root
= cgrp
->root
;
567 struct cgroup_subsys
*ss
;
568 struct css_set
*cset
;
573 * Build the set of subsystem state objects that we want to see in the
574 * new css_set. while subsystems can change globally, the entries here
575 * won't change, so no need for locking.
577 for_each_subsys(ss
, i
) {
578 if (root
->subsys_mask
& (1UL << i
)) {
580 * @ss is in this hierarchy, so we want the
581 * effective css from @cgrp.
583 template[i
] = cgroup_e_css(cgrp
, ss
);
586 * @ss is not in this hierarchy, so we don't want
589 template[i
] = old_cset
->subsys
[i
];
593 key
= css_set_hash(template);
594 hash_for_each_possible(css_set_table
, cset
, hlist
, key
) {
595 if (!compare_css_sets(cset
, old_cset
, cgrp
, template))
598 /* This css_set matches what we need */
602 /* No existing cgroup group matched */
606 static void free_cgrp_cset_links(struct list_head
*links_to_free
)
608 struct cgrp_cset_link
*link
, *tmp_link
;
610 list_for_each_entry_safe(link
, tmp_link
, links_to_free
, cset_link
) {
611 list_del(&link
->cset_link
);
617 * allocate_cgrp_cset_links - allocate cgrp_cset_links
618 * @count: the number of links to allocate
619 * @tmp_links: list_head the allocated links are put on
621 * Allocate @count cgrp_cset_link structures and chain them on @tmp_links
622 * through ->cset_link. Returns 0 on success or -errno.
624 static int allocate_cgrp_cset_links(int count
, struct list_head
*tmp_links
)
626 struct cgrp_cset_link
*link
;
629 INIT_LIST_HEAD(tmp_links
);
631 for (i
= 0; i
< count
; i
++) {
632 link
= kzalloc(sizeof(*link
), GFP_KERNEL
);
634 free_cgrp_cset_links(tmp_links
);
637 list_add(&link
->cset_link
, tmp_links
);
643 * link_css_set - a helper function to link a css_set to a cgroup
644 * @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()
645 * @cset: the css_set to be linked
646 * @cgrp: the destination cgroup
648 static void link_css_set(struct list_head
*tmp_links
, struct css_set
*cset
,
651 struct cgrp_cset_link
*link
;
653 BUG_ON(list_empty(tmp_links
));
654 link
= list_first_entry(tmp_links
, struct cgrp_cset_link
, cset_link
);
657 list_move(&link
->cset_link
, &cgrp
->cset_links
);
659 * Always add links to the tail of the list so that the list
660 * is sorted by order of hierarchy creation
662 list_add_tail(&link
->cgrp_link
, &cset
->cgrp_links
);
666 * find_css_set - return a new css_set with one cgroup updated
667 * @old_cset: the baseline css_set
668 * @cgrp: the cgroup to be updated
670 * Return a new css_set that's equivalent to @old_cset, but with @cgrp
671 * substituted into the appropriate hierarchy.
673 static struct css_set
*find_css_set(struct css_set
*old_cset
,
676 struct cgroup_subsys_state
*template[CGROUP_SUBSYS_COUNT
] = { };
677 struct css_set
*cset
;
678 struct list_head tmp_links
;
679 struct cgrp_cset_link
*link
;
680 struct cgroup_subsys
*ss
;
684 lockdep_assert_held(&cgroup_mutex
);
686 /* First see if we already have a cgroup group that matches
688 down_read(&css_set_rwsem
);
689 cset
= find_existing_css_set(old_cset
, cgrp
, template);
692 up_read(&css_set_rwsem
);
697 cset
= kzalloc(sizeof(*cset
), GFP_KERNEL
);
701 /* Allocate all the cgrp_cset_link objects that we'll need */
702 if (allocate_cgrp_cset_links(cgroup_root_count
, &tmp_links
) < 0) {
707 atomic_set(&cset
->refcount
, 1);
708 INIT_LIST_HEAD(&cset
->cgrp_links
);
709 INIT_LIST_HEAD(&cset
->tasks
);
710 INIT_LIST_HEAD(&cset
->mg_tasks
);
711 INIT_LIST_HEAD(&cset
->mg_preload_node
);
712 INIT_LIST_HEAD(&cset
->mg_node
);
713 INIT_HLIST_NODE(&cset
->hlist
);
715 /* Copy the set of subsystem state objects generated in
716 * find_existing_css_set() */
717 memcpy(cset
->subsys
, template, sizeof(cset
->subsys
));
719 down_write(&css_set_rwsem
);
720 /* Add reference counts and links from the new css_set. */
721 list_for_each_entry(link
, &old_cset
->cgrp_links
, cgrp_link
) {
722 struct cgroup
*c
= link
->cgrp
;
724 if (c
->root
== cgrp
->root
)
726 link_css_set(&tmp_links
, cset
, c
);
729 BUG_ON(!list_empty(&tmp_links
));
733 /* Add @cset to the hash table */
734 key
= css_set_hash(cset
->subsys
);
735 hash_add(css_set_table
, &cset
->hlist
, key
);
737 for_each_subsys(ss
, ssid
)
738 list_add_tail(&cset
->e_cset_node
[ssid
],
739 &cset
->subsys
[ssid
]->cgroup
->e_csets
[ssid
]);
741 up_write(&css_set_rwsem
);
746 static struct cgroup_root
*cgroup_root_from_kf(struct kernfs_root
*kf_root
)
748 struct cgroup
*root_cgrp
= kf_root
->kn
->priv
;
750 return root_cgrp
->root
;
753 static int cgroup_init_root_id(struct cgroup_root
*root
)
757 lockdep_assert_held(&cgroup_mutex
);
759 id
= idr_alloc_cyclic(&cgroup_hierarchy_idr
, root
, 0, 0, GFP_KERNEL
);
763 root
->hierarchy_id
= id
;
767 static void cgroup_exit_root_id(struct cgroup_root
*root
)
769 lockdep_assert_held(&cgroup_mutex
);
771 if (root
->hierarchy_id
) {
772 idr_remove(&cgroup_hierarchy_idr
, root
->hierarchy_id
);
773 root
->hierarchy_id
= 0;
777 static void cgroup_free_root(struct cgroup_root
*root
)
780 /* hierarhcy ID shoulid already have been released */
781 WARN_ON_ONCE(root
->hierarchy_id
);
783 idr_destroy(&root
->cgroup_idr
);
788 static void cgroup_destroy_root(struct cgroup_root
*root
)
790 struct cgroup
*cgrp
= &root
->cgrp
;
791 struct cgrp_cset_link
*link
, *tmp_link
;
793 mutex_lock(&cgroup_tree_mutex
);
794 mutex_lock(&cgroup_mutex
);
796 BUG_ON(atomic_read(&root
->nr_cgrps
));
797 BUG_ON(!list_empty(&cgrp
->children
));
799 /* Rebind all subsystems back to the default hierarchy */
800 rebind_subsystems(&cgrp_dfl_root
, root
->subsys_mask
);
803 * Release all the links from cset_links to this hierarchy's
806 down_write(&css_set_rwsem
);
808 list_for_each_entry_safe(link
, tmp_link
, &cgrp
->cset_links
, cset_link
) {
809 list_del(&link
->cset_link
);
810 list_del(&link
->cgrp_link
);
813 up_write(&css_set_rwsem
);
815 if (!list_empty(&root
->root_list
)) {
816 list_del(&root
->root_list
);
820 cgroup_exit_root_id(root
);
822 mutex_unlock(&cgroup_mutex
);
823 mutex_unlock(&cgroup_tree_mutex
);
825 kernfs_destroy_root(root
->kf_root
);
826 cgroup_free_root(root
);
829 /* look up cgroup associated with given css_set on the specified hierarchy */
830 static struct cgroup
*cset_cgroup_from_root(struct css_set
*cset
,
831 struct cgroup_root
*root
)
833 struct cgroup
*res
= NULL
;
835 lockdep_assert_held(&cgroup_mutex
);
836 lockdep_assert_held(&css_set_rwsem
);
838 if (cset
== &init_css_set
) {
841 struct cgrp_cset_link
*link
;
843 list_for_each_entry(link
, &cset
->cgrp_links
, cgrp_link
) {
844 struct cgroup
*c
= link
->cgrp
;
846 if (c
->root
== root
) {
858 * Return the cgroup for "task" from the given hierarchy. Must be
859 * called with cgroup_mutex and css_set_rwsem held.
861 static struct cgroup
*task_cgroup_from_root(struct task_struct
*task
,
862 struct cgroup_root
*root
)
865 * No need to lock the task - since we hold cgroup_mutex the
866 * task can't change groups, so the only thing that can happen
867 * is that it exits and its css is set back to init_css_set.
869 return cset_cgroup_from_root(task_css_set(task
), root
);
873 * A task must hold cgroup_mutex to modify cgroups.
875 * Any task can increment and decrement the count field without lock.
876 * So in general, code holding cgroup_mutex can't rely on the count
877 * field not changing. However, if the count goes to zero, then only
878 * cgroup_attach_task() can increment it again. Because a count of zero
879 * means that no tasks are currently attached, therefore there is no
880 * way a task attached to that cgroup can fork (the other way to
881 * increment the count). So code holding cgroup_mutex can safely
882 * assume that if the count is zero, it will stay zero. Similarly, if
883 * a task holds cgroup_mutex on a cgroup with zero count, it
884 * knows that the cgroup won't be removed, as cgroup_rmdir()
887 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
888 * (usually) take cgroup_mutex. These are the two most performance
889 * critical pieces of code here. The exception occurs on cgroup_exit(),
890 * when a task in a notify_on_release cgroup exits. Then cgroup_mutex
891 * is taken, and if the cgroup count is zero, a usermode call made
892 * to the release agent with the name of the cgroup (path relative to
893 * the root of cgroup file system) as the argument.
895 * A cgroup can only be deleted if both its 'count' of using tasks
896 * is zero, and its list of 'children' cgroups is empty. Since all
897 * tasks in the system use _some_ cgroup, and since there is always at
898 * least one task in the system (init, pid == 1), therefore, root cgroup
899 * always has either children cgroups and/or using tasks. So we don't
900 * need a special hack to ensure that root cgroup cannot be deleted.
902 * P.S. One more locking exception. RCU is used to guard the
903 * update of a tasks cgroup pointer by cgroup_attach_task()
906 static int cgroup_populate_dir(struct cgroup
*cgrp
, unsigned long subsys_mask
);
907 static struct kernfs_syscall_ops cgroup_kf_syscall_ops
;
908 static const struct file_operations proc_cgroupstats_operations
;
910 static char *cgroup_file_name(struct cgroup
*cgrp
, const struct cftype
*cft
,
913 if (cft
->ss
&& !(cft
->flags
& CFTYPE_NO_PREFIX
) &&
914 !(cgrp
->root
->flags
& CGRP_ROOT_NOPREFIX
))
915 snprintf(buf
, CGROUP_FILE_NAME_MAX
, "%s.%s",
916 cft
->ss
->name
, cft
->name
);
918 strncpy(buf
, cft
->name
, CGROUP_FILE_NAME_MAX
);
923 * cgroup_file_mode - deduce file mode of a control file
924 * @cft: the control file in question
926 * returns cft->mode if ->mode is not 0
927 * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
928 * returns S_IRUGO if it has only a read handler
929 * returns S_IWUSR if it has only a write hander
931 static umode_t
cgroup_file_mode(const struct cftype
*cft
)
938 if (cft
->read_u64
|| cft
->read_s64
|| cft
->seq_show
)
941 if (cft
->write_u64
|| cft
->write_s64
|| cft
->write_string
||
948 static void cgroup_free_fn(struct work_struct
*work
)
950 struct cgroup
*cgrp
= container_of(work
, struct cgroup
, destroy_work
);
952 atomic_dec(&cgrp
->root
->nr_cgrps
);
953 cgroup_pidlist_destroy_all(cgrp
);
957 * We get a ref to the parent, and put the ref when this
958 * cgroup is being freed, so it's guaranteed that the
959 * parent won't be destroyed before its children.
961 cgroup_put(cgrp
->parent
);
962 kernfs_put(cgrp
->kn
);
966 * This is root cgroup's refcnt reaching zero, which
967 * indicates that the root should be released.
969 cgroup_destroy_root(cgrp
->root
);
973 static void cgroup_free_rcu(struct rcu_head
*head
)
975 struct cgroup
*cgrp
= container_of(head
, struct cgroup
, rcu_head
);
977 INIT_WORK(&cgrp
->destroy_work
, cgroup_free_fn
);
978 queue_work(cgroup_destroy_wq
, &cgrp
->destroy_work
);
981 static void cgroup_get(struct cgroup
*cgrp
)
983 WARN_ON_ONCE(cgroup_is_dead(cgrp
));
984 WARN_ON_ONCE(atomic_read(&cgrp
->refcnt
) <= 0);
985 atomic_inc(&cgrp
->refcnt
);
988 static void cgroup_put(struct cgroup
*cgrp
)
990 if (!atomic_dec_and_test(&cgrp
->refcnt
))
992 if (WARN_ON_ONCE(cgrp
->parent
&& !cgroup_is_dead(cgrp
)))
996 * XXX: cgrp->id is only used to look up css's. As cgroup and
997 * css's lifetimes will be decoupled, it should be made
998 * per-subsystem and moved to css->id so that lookups are
999 * successful until the target css is released.
1001 mutex_lock(&cgroup_mutex
);
1002 idr_remove(&cgrp
->root
->cgroup_idr
, cgrp
->id
);
1003 mutex_unlock(&cgroup_mutex
);
1006 call_rcu(&cgrp
->rcu_head
, cgroup_free_rcu
);
1009 static void cgroup_rm_file(struct cgroup
*cgrp
, const struct cftype
*cft
)
1011 char name
[CGROUP_FILE_NAME_MAX
];
1013 lockdep_assert_held(&cgroup_tree_mutex
);
1014 kernfs_remove_by_name(cgrp
->kn
, cgroup_file_name(cgrp
, cft
, name
));
1018 * cgroup_clear_dir - remove subsys files in a cgroup directory
1019 * @cgrp: target cgroup
1020 * @subsys_mask: mask of the subsystem ids whose files should be removed
1022 static void cgroup_clear_dir(struct cgroup
*cgrp
, unsigned long subsys_mask
)
1024 struct cgroup_subsys
*ss
;
1027 for_each_subsys(ss
, i
) {
1028 struct cftype
*cfts
;
1030 if (!test_bit(i
, &subsys_mask
))
1032 list_for_each_entry(cfts
, &ss
->cfts
, node
)
1033 cgroup_addrm_files(cgrp
, cfts
, false);
1037 static int rebind_subsystems(struct cgroup_root
*dst_root
,
1038 unsigned long ss_mask
)
1040 struct cgroup_subsys
*ss
;
1043 lockdep_assert_held(&cgroup_tree_mutex
);
1044 lockdep_assert_held(&cgroup_mutex
);
1046 for_each_subsys(ss
, ssid
) {
1047 if (!(ss_mask
& (1 << ssid
)))
1050 /* if @ss is on the dummy_root, we can always move it */
1051 if (ss
->root
== &cgrp_dfl_root
)
1054 /* if @ss has non-root cgroups attached to it, can't move */
1055 if (!list_empty(&ss
->root
->cgrp
.children
))
1058 /* can't move between two non-dummy roots either */
1059 if (dst_root
!= &cgrp_dfl_root
)
1063 ret
= cgroup_populate_dir(&dst_root
->cgrp
, ss_mask
);
1065 if (dst_root
!= &cgrp_dfl_root
)
1069 * Rebinding back to the default root is not allowed to
1070 * fail. Using both default and non-default roots should
1071 * be rare. Moving subsystems back and forth even more so.
1072 * Just warn about it and continue.
1074 if (cgrp_dfl_root_visible
) {
1075 pr_warning("cgroup: failed to create files (%d) while rebinding 0x%lx to default root\n",
1077 pr_warning("cgroup: you may retry by moving them to a different hierarchy and unbinding\n");
1082 * Nothing can fail from this point on. Remove files for the
1083 * removed subsystems and rebind each subsystem.
1085 mutex_unlock(&cgroup_mutex
);
1086 for_each_subsys(ss
, ssid
)
1087 if (ss_mask
& (1 << ssid
))
1088 cgroup_clear_dir(&ss
->root
->cgrp
, 1 << ssid
);
1089 mutex_lock(&cgroup_mutex
);
1091 for_each_subsys(ss
, ssid
) {
1092 struct cgroup_root
*src_root
;
1093 struct cgroup_subsys_state
*css
;
1094 struct css_set
*cset
;
1096 if (!(ss_mask
& (1 << ssid
)))
1099 src_root
= ss
->root
;
1100 css
= cgroup_css(&src_root
->cgrp
, ss
);
1102 WARN_ON(!css
|| cgroup_css(&dst_root
->cgrp
, ss
));
1104 RCU_INIT_POINTER(src_root
->cgrp
.subsys
[ssid
], NULL
);
1105 rcu_assign_pointer(dst_root
->cgrp
.subsys
[ssid
], css
);
1106 ss
->root
= dst_root
;
1107 css
->cgroup
= &dst_root
->cgrp
;
1109 down_write(&css_set_rwsem
);
1110 hash_for_each(css_set_table
, i
, cset
, hlist
)
1111 list_move_tail(&cset
->e_cset_node
[ss
->id
],
1112 &dst_root
->cgrp
.e_csets
[ss
->id
]);
1113 up_write(&css_set_rwsem
);
1115 src_root
->subsys_mask
&= ~(1 << ssid
);
1116 src_root
->cgrp
.child_subsys_mask
&= ~(1 << ssid
);
1118 dst_root
->subsys_mask
|= 1 << ssid
;
1119 dst_root
->cgrp
.child_subsys_mask
|= 1 << ssid
;
1125 kernfs_activate(dst_root
->cgrp
.kn
);
1129 static int cgroup_show_options(struct seq_file
*seq
,
1130 struct kernfs_root
*kf_root
)
1132 struct cgroup_root
*root
= cgroup_root_from_kf(kf_root
);
1133 struct cgroup_subsys
*ss
;
1136 for_each_subsys(ss
, ssid
)
1137 if (root
->subsys_mask
& (1 << ssid
))
1138 seq_printf(seq
, ",%s", ss
->name
);
1139 if (root
->flags
& CGRP_ROOT_SANE_BEHAVIOR
)
1140 seq_puts(seq
, ",sane_behavior");
1141 if (root
->flags
& CGRP_ROOT_NOPREFIX
)
1142 seq_puts(seq
, ",noprefix");
1143 if (root
->flags
& CGRP_ROOT_XATTR
)
1144 seq_puts(seq
, ",xattr");
1146 spin_lock(&release_agent_path_lock
);
1147 if (strlen(root
->release_agent_path
))
1148 seq_printf(seq
, ",release_agent=%s", root
->release_agent_path
);
1149 spin_unlock(&release_agent_path_lock
);
1151 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN
, &root
->cgrp
.flags
))
1152 seq_puts(seq
, ",clone_children");
1153 if (strlen(root
->name
))
1154 seq_printf(seq
, ",name=%s", root
->name
);
1158 struct cgroup_sb_opts
{
1159 unsigned long subsys_mask
;
1160 unsigned long flags
;
1161 char *release_agent
;
1162 bool cpuset_clone_children
;
1164 /* User explicitly requested empty subsystem */
1169 * Convert a hierarchy specifier into a bitmask of subsystems and
1170 * flags. Call with cgroup_mutex held to protect the cgroup_subsys[]
1171 * array. This function takes refcounts on subsystems to be used, unless it
1172 * returns error, in which case no refcounts are taken.
1174 static int parse_cgroupfs_options(char *data
, struct cgroup_sb_opts
*opts
)
1176 char *token
, *o
= data
;
1177 bool all_ss
= false, one_ss
= false;
1178 unsigned long mask
= (unsigned long)-1;
1179 struct cgroup_subsys
*ss
;
1182 BUG_ON(!mutex_is_locked(&cgroup_mutex
));
1184 #ifdef CONFIG_CPUSETS
1185 mask
= ~(1UL << cpuset_cgrp_id
);
1188 memset(opts
, 0, sizeof(*opts
));
1190 while ((token
= strsep(&o
, ",")) != NULL
) {
1193 if (!strcmp(token
, "none")) {
1194 /* Explicitly have no subsystems */
1198 if (!strcmp(token
, "all")) {
1199 /* Mutually exclusive option 'all' + subsystem name */
1205 if (!strcmp(token
, "__DEVEL__sane_behavior")) {
1206 opts
->flags
|= CGRP_ROOT_SANE_BEHAVIOR
;
1209 if (!strcmp(token
, "noprefix")) {
1210 opts
->flags
|= CGRP_ROOT_NOPREFIX
;
1213 if (!strcmp(token
, "clone_children")) {
1214 opts
->cpuset_clone_children
= true;
1217 if (!strcmp(token
, "xattr")) {
1218 opts
->flags
|= CGRP_ROOT_XATTR
;
1221 if (!strncmp(token
, "release_agent=", 14)) {
1222 /* Specifying two release agents is forbidden */
1223 if (opts
->release_agent
)
1225 opts
->release_agent
=
1226 kstrndup(token
+ 14, PATH_MAX
- 1, GFP_KERNEL
);
1227 if (!opts
->release_agent
)
1231 if (!strncmp(token
, "name=", 5)) {
1232 const char *name
= token
+ 5;
1233 /* Can't specify an empty name */
1236 /* Must match [\w.-]+ */
1237 for (i
= 0; i
< strlen(name
); i
++) {
1241 if ((c
== '.') || (c
== '-') || (c
== '_'))
1245 /* Specifying two names is forbidden */
1248 opts
->name
= kstrndup(name
,
1249 MAX_CGROUP_ROOT_NAMELEN
- 1,
1257 for_each_subsys(ss
, i
) {
1258 if (strcmp(token
, ss
->name
))
1263 /* Mutually exclusive option 'all' + subsystem name */
1266 set_bit(i
, &opts
->subsys_mask
);
1271 if (i
== CGROUP_SUBSYS_COUNT
)
1275 /* Consistency checks */
1277 if (opts
->flags
& CGRP_ROOT_SANE_BEHAVIOR
) {
1278 pr_warning("cgroup: sane_behavior: this is still under development and its behaviors will change, proceed at your own risk\n");
1280 if ((opts
->flags
& (CGRP_ROOT_NOPREFIX
| CGRP_ROOT_XATTR
)) ||
1281 opts
->cpuset_clone_children
|| opts
->release_agent
||
1283 pr_err("cgroup: sane_behavior: noprefix, xattr, clone_children, release_agent and name are not allowed\n");
1288 * If the 'all' option was specified select all the
1289 * subsystems, otherwise if 'none', 'name=' and a subsystem
1290 * name options were not specified, let's default to 'all'
1292 if (all_ss
|| (!one_ss
&& !opts
->none
&& !opts
->name
))
1293 for_each_subsys(ss
, i
)
1295 set_bit(i
, &opts
->subsys_mask
);
1298 * We either have to specify by name or by subsystems. (So
1299 * all empty hierarchies must have a name).
1301 if (!opts
->subsys_mask
&& !opts
->name
)
1306 * Option noprefix was introduced just for backward compatibility
1307 * with the old cpuset, so we allow noprefix only if mounting just
1308 * the cpuset subsystem.
1310 if ((opts
->flags
& CGRP_ROOT_NOPREFIX
) && (opts
->subsys_mask
& mask
))
1314 /* Can't specify "none" and some subsystems */
1315 if (opts
->subsys_mask
&& opts
->none
)
1321 static int cgroup_remount(struct kernfs_root
*kf_root
, int *flags
, char *data
)
1324 struct cgroup_root
*root
= cgroup_root_from_kf(kf_root
);
1325 struct cgroup_sb_opts opts
;
1326 unsigned long added_mask
, removed_mask
;
1328 if (root
->flags
& CGRP_ROOT_SANE_BEHAVIOR
) {
1329 pr_err("cgroup: sane_behavior: remount is not allowed\n");
1333 mutex_lock(&cgroup_tree_mutex
);
1334 mutex_lock(&cgroup_mutex
);
1336 /* See what subsystems are wanted */
1337 ret
= parse_cgroupfs_options(data
, &opts
);
1341 if (opts
.subsys_mask
!= root
->subsys_mask
|| opts
.release_agent
)
1342 pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
1343 task_tgid_nr(current
), current
->comm
);
1345 added_mask
= opts
.subsys_mask
& ~root
->subsys_mask
;
1346 removed_mask
= root
->subsys_mask
& ~opts
.subsys_mask
;
1348 /* Don't allow flags or name to change at remount */
1349 if (((opts
.flags
^ root
->flags
) & CGRP_ROOT_OPTION_MASK
) ||
1350 (opts
.name
&& strcmp(opts
.name
, root
->name
))) {
1351 pr_err("cgroup: option or name mismatch, new: 0x%lx \"%s\", old: 0x%lx \"%s\"\n",
1352 opts
.flags
& CGRP_ROOT_OPTION_MASK
, opts
.name
?: "",
1353 root
->flags
& CGRP_ROOT_OPTION_MASK
, root
->name
);
1358 /* remounting is not allowed for populated hierarchies */
1359 if (!list_empty(&root
->cgrp
.children
)) {
1364 ret
= rebind_subsystems(root
, added_mask
);
1368 rebind_subsystems(&cgrp_dfl_root
, removed_mask
);
1370 if (opts
.release_agent
) {
1371 spin_lock(&release_agent_path_lock
);
1372 strcpy(root
->release_agent_path
, opts
.release_agent
);
1373 spin_unlock(&release_agent_path_lock
);
1376 kfree(opts
.release_agent
);
1378 mutex_unlock(&cgroup_mutex
);
1379 mutex_unlock(&cgroup_tree_mutex
);
1384 * To reduce the fork() overhead for systems that are not actually using
1385 * their cgroups capability, we don't maintain the lists running through
1386 * each css_set to its tasks until we see the list actually used - in other
1387 * words after the first mount.
1389 static bool use_task_css_set_links __read_mostly
;
1391 static void cgroup_enable_task_cg_lists(void)
1393 struct task_struct
*p
, *g
;
1395 down_write(&css_set_rwsem
);
1397 if (use_task_css_set_links
)
1400 use_task_css_set_links
= true;
1403 * We need tasklist_lock because RCU is not safe against
1404 * while_each_thread(). Besides, a forking task that has passed
1405 * cgroup_post_fork() without seeing use_task_css_set_links = 1
1406 * is not guaranteed to have its child immediately visible in the
1407 * tasklist if we walk through it with RCU.
1409 read_lock(&tasklist_lock
);
1410 do_each_thread(g
, p
) {
1411 WARN_ON_ONCE(!list_empty(&p
->cg_list
) ||
1412 task_css_set(p
) != &init_css_set
);
1415 * We should check if the process is exiting, otherwise
1416 * it will race with cgroup_exit() in that the list
1417 * entry won't be deleted though the process has exited.
1418 * Do it while holding siglock so that we don't end up
1419 * racing against cgroup_exit().
1421 spin_lock_irq(&p
->sighand
->siglock
);
1422 if (!(p
->flags
& PF_EXITING
)) {
1423 struct css_set
*cset
= task_css_set(p
);
1425 list_add(&p
->cg_list
, &cset
->tasks
);
1428 spin_unlock_irq(&p
->sighand
->siglock
);
1429 } while_each_thread(g
, p
);
1430 read_unlock(&tasklist_lock
);
1432 up_write(&css_set_rwsem
);
1435 static void init_cgroup_housekeeping(struct cgroup
*cgrp
)
1437 struct cgroup_subsys
*ss
;
1440 atomic_set(&cgrp
->refcnt
, 1);
1441 INIT_LIST_HEAD(&cgrp
->sibling
);
1442 INIT_LIST_HEAD(&cgrp
->children
);
1443 INIT_LIST_HEAD(&cgrp
->cset_links
);
1444 INIT_LIST_HEAD(&cgrp
->release_list
);
1445 INIT_LIST_HEAD(&cgrp
->pidlists
);
1446 mutex_init(&cgrp
->pidlist_mutex
);
1447 cgrp
->dummy_css
.cgroup
= cgrp
;
1449 for_each_subsys(ss
, ssid
)
1450 INIT_LIST_HEAD(&cgrp
->e_csets
[ssid
]);
1453 static void init_cgroup_root(struct cgroup_root
*root
,
1454 struct cgroup_sb_opts
*opts
)
1456 struct cgroup
*cgrp
= &root
->cgrp
;
1458 INIT_LIST_HEAD(&root
->root_list
);
1459 atomic_set(&root
->nr_cgrps
, 1);
1461 init_cgroup_housekeeping(cgrp
);
1462 idr_init(&root
->cgroup_idr
);
1464 root
->flags
= opts
->flags
;
1465 if (opts
->release_agent
)
1466 strcpy(root
->release_agent_path
, opts
->release_agent
);
1468 strcpy(root
->name
, opts
->name
);
1469 if (opts
->cpuset_clone_children
)
1470 set_bit(CGRP_CPUSET_CLONE_CHILDREN
, &root
->cgrp
.flags
);
1473 static int cgroup_setup_root(struct cgroup_root
*root
, unsigned long ss_mask
)
1475 LIST_HEAD(tmp_links
);
1476 struct cgroup
*root_cgrp
= &root
->cgrp
;
1477 struct css_set
*cset
;
1480 lockdep_assert_held(&cgroup_tree_mutex
);
1481 lockdep_assert_held(&cgroup_mutex
);
1483 ret
= idr_alloc(&root
->cgroup_idr
, root_cgrp
, 0, 1, GFP_KERNEL
);
1486 root_cgrp
->id
= ret
;
1489 * We're accessing css_set_count without locking css_set_rwsem here,
1490 * but that's OK - it can only be increased by someone holding
1491 * cgroup_lock, and that's us. The worst that can happen is that we
1492 * have some link structures left over
1494 ret
= allocate_cgrp_cset_links(css_set_count
, &tmp_links
);
1498 ret
= cgroup_init_root_id(root
);
1502 root
->kf_root
= kernfs_create_root(&cgroup_kf_syscall_ops
,
1503 KERNFS_ROOT_CREATE_DEACTIVATED
,
1505 if (IS_ERR(root
->kf_root
)) {
1506 ret
= PTR_ERR(root
->kf_root
);
1509 root_cgrp
->kn
= root
->kf_root
->kn
;
1511 ret
= cgroup_addrm_files(root_cgrp
, cgroup_base_files
, true);
1515 ret
= rebind_subsystems(root
, ss_mask
);
1520 * There must be no failure case after here, since rebinding takes
1521 * care of subsystems' refcounts, which are explicitly dropped in
1522 * the failure exit path.
1524 list_add(&root
->root_list
, &cgroup_roots
);
1525 cgroup_root_count
++;
1528 * Link the root cgroup in this hierarchy into all the css_set
1531 down_write(&css_set_rwsem
);
1532 hash_for_each(css_set_table
, i
, cset
, hlist
)
1533 link_css_set(&tmp_links
, cset
, root_cgrp
);
1534 up_write(&css_set_rwsem
);
1536 BUG_ON(!list_empty(&root_cgrp
->children
));
1537 BUG_ON(atomic_read(&root
->nr_cgrps
) != 1);
1539 kernfs_activate(root_cgrp
->kn
);
1544 kernfs_destroy_root(root
->kf_root
);
1545 root
->kf_root
= NULL
;
1547 cgroup_exit_root_id(root
);
1549 free_cgrp_cset_links(&tmp_links
);
1553 static struct dentry
*cgroup_mount(struct file_system_type
*fs_type
,
1554 int flags
, const char *unused_dev_name
,
1557 struct cgroup_root
*root
;
1558 struct cgroup_sb_opts opts
;
1559 struct dentry
*dentry
;
1564 * The first time anyone tries to mount a cgroup, enable the list
1565 * linking each css_set to its tasks and fix up all existing tasks.
1567 if (!use_task_css_set_links
)
1568 cgroup_enable_task_cg_lists();
1570 mutex_lock(&cgroup_tree_mutex
);
1571 mutex_lock(&cgroup_mutex
);
1573 /* First find the desired set of subsystems */
1574 ret
= parse_cgroupfs_options(data
, &opts
);
1578 /* look for a matching existing root */
1579 if (!opts
.subsys_mask
&& !opts
.none
&& !opts
.name
) {
1580 cgrp_dfl_root_visible
= true;
1581 root
= &cgrp_dfl_root
;
1582 cgroup_get(&root
->cgrp
);
1587 for_each_root(root
) {
1588 bool name_match
= false;
1590 if (root
== &cgrp_dfl_root
)
1594 * If we asked for a name then it must match. Also, if
1595 * name matches but sybsys_mask doesn't, we should fail.
1596 * Remember whether name matched.
1599 if (strcmp(opts
.name
, root
->name
))
1605 * If we asked for subsystems (or explicitly for no
1606 * subsystems) then they must match.
1608 if ((opts
.subsys_mask
|| opts
.none
) &&
1609 (opts
.subsys_mask
!= root
->subsys_mask
)) {
1616 if ((root
->flags
^ opts
.flags
) & CGRP_ROOT_OPTION_MASK
) {
1617 if ((root
->flags
| opts
.flags
) & CGRP_ROOT_SANE_BEHAVIOR
) {
1618 pr_err("cgroup: sane_behavior: new mount options should match the existing superblock\n");
1622 pr_warning("cgroup: new mount options do not match the existing superblock, will be ignored\n");
1627 * A root's lifetime is governed by its root cgroup. Zero
1628 * ref indicate that the root is being destroyed. Wait for
1629 * destruction to complete so that the subsystems are free.
1630 * We can use wait_queue for the wait but this path is
1631 * super cold. Let's just sleep for a bit and retry.
1633 if (!atomic_inc_not_zero(&root
->cgrp
.refcnt
)) {
1634 mutex_unlock(&cgroup_mutex
);
1635 mutex_unlock(&cgroup_tree_mutex
);
1637 mutex_lock(&cgroup_tree_mutex
);
1638 mutex_lock(&cgroup_mutex
);
1647 * No such thing, create a new one. name= matching without subsys
1648 * specification is allowed for already existing hierarchies but we
1649 * can't create new one without subsys specification.
1651 if (!opts
.subsys_mask
&& !opts
.none
) {
1656 root
= kzalloc(sizeof(*root
), GFP_KERNEL
);
1662 init_cgroup_root(root
, &opts
);
1664 ret
= cgroup_setup_root(root
, opts
.subsys_mask
);
1666 cgroup_free_root(root
);
1669 mutex_unlock(&cgroup_mutex
);
1670 mutex_unlock(&cgroup_tree_mutex
);
1672 kfree(opts
.release_agent
);
1676 return ERR_PTR(ret
);
1678 dentry
= kernfs_mount(fs_type
, flags
, root
->kf_root
, &new_sb
);
1679 if (IS_ERR(dentry
) || !new_sb
)
1680 cgroup_put(&root
->cgrp
);
1684 static void cgroup_kill_sb(struct super_block
*sb
)
1686 struct kernfs_root
*kf_root
= kernfs_root_from_sb(sb
);
1687 struct cgroup_root
*root
= cgroup_root_from_kf(kf_root
);
1689 cgroup_put(&root
->cgrp
);
1693 static struct file_system_type cgroup_fs_type
= {
1695 .mount
= cgroup_mount
,
1696 .kill_sb
= cgroup_kill_sb
,
1699 static struct kobject
*cgroup_kobj
;
1702 * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
1703 * @task: target task
1704 * @buf: the buffer to write the path into
1705 * @buflen: the length of the buffer
1707 * Determine @task's cgroup on the first (the one with the lowest non-zero
1708 * hierarchy_id) cgroup hierarchy and copy its path into @buf. This
1709 * function grabs cgroup_mutex and shouldn't be used inside locks used by
1710 * cgroup controller callbacks.
1712 * Return value is the same as kernfs_path().
1714 char *task_cgroup_path(struct task_struct
*task
, char *buf
, size_t buflen
)
1716 struct cgroup_root
*root
;
1717 struct cgroup
*cgrp
;
1718 int hierarchy_id
= 1;
1721 mutex_lock(&cgroup_mutex
);
1722 down_read(&css_set_rwsem
);
1724 root
= idr_get_next(&cgroup_hierarchy_idr
, &hierarchy_id
);
1727 cgrp
= task_cgroup_from_root(task
, root
);
1728 path
= cgroup_path(cgrp
, buf
, buflen
);
1730 /* if no hierarchy exists, everyone is in "/" */
1731 if (strlcpy(buf
, "/", buflen
) < buflen
)
1735 up_read(&css_set_rwsem
);
1736 mutex_unlock(&cgroup_mutex
);
1739 EXPORT_SYMBOL_GPL(task_cgroup_path
);
1741 /* used to track tasks and other necessary states during migration */
1742 struct cgroup_taskset
{
1743 /* the src and dst cset list running through cset->mg_node */
1744 struct list_head src_csets
;
1745 struct list_head dst_csets
;
1748 * Fields for cgroup_taskset_*() iteration.
1750 * Before migration is committed, the target migration tasks are on
1751 * ->mg_tasks of the csets on ->src_csets. After, on ->mg_tasks of
1752 * the csets on ->dst_csets. ->csets point to either ->src_csets
1753 * or ->dst_csets depending on whether migration is committed.
1755 * ->cur_csets and ->cur_task point to the current task position
1758 struct list_head
*csets
;
1759 struct css_set
*cur_cset
;
1760 struct task_struct
*cur_task
;
1764 * cgroup_taskset_first - reset taskset and return the first task
1765 * @tset: taskset of interest
1767 * @tset iteration is initialized and the first task is returned.
1769 struct task_struct
*cgroup_taskset_first(struct cgroup_taskset
*tset
)
1771 tset
->cur_cset
= list_first_entry(tset
->csets
, struct css_set
, mg_node
);
1772 tset
->cur_task
= NULL
;
1774 return cgroup_taskset_next(tset
);
1778 * cgroup_taskset_next - iterate to the next task in taskset
1779 * @tset: taskset of interest
1781 * Return the next task in @tset. Iteration must have been initialized
1782 * with cgroup_taskset_first().
1784 struct task_struct
*cgroup_taskset_next(struct cgroup_taskset
*tset
)
1786 struct css_set
*cset
= tset
->cur_cset
;
1787 struct task_struct
*task
= tset
->cur_task
;
1789 while (&cset
->mg_node
!= tset
->csets
) {
1791 task
= list_first_entry(&cset
->mg_tasks
,
1792 struct task_struct
, cg_list
);
1794 task
= list_next_entry(task
, cg_list
);
1796 if (&task
->cg_list
!= &cset
->mg_tasks
) {
1797 tset
->cur_cset
= cset
;
1798 tset
->cur_task
= task
;
1802 cset
= list_next_entry(cset
, mg_node
);
1810 * cgroup_task_migrate - move a task from one cgroup to another.
1811 * @old_cgrp; the cgroup @tsk is being migrated from
1812 * @tsk: the task being migrated
1813 * @new_cset: the new css_set @tsk is being attached to
1815 * Must be called with cgroup_mutex, threadgroup and css_set_rwsem locked.
1817 static void cgroup_task_migrate(struct cgroup
*old_cgrp
,
1818 struct task_struct
*tsk
,
1819 struct css_set
*new_cset
)
1821 struct css_set
*old_cset
;
1823 lockdep_assert_held(&cgroup_mutex
);
1824 lockdep_assert_held(&css_set_rwsem
);
1827 * We are synchronized through threadgroup_lock() against PF_EXITING
1828 * setting such that we can't race against cgroup_exit() changing the
1829 * css_set to init_css_set and dropping the old one.
1831 WARN_ON_ONCE(tsk
->flags
& PF_EXITING
);
1832 old_cset
= task_css_set(tsk
);
1834 get_css_set(new_cset
);
1835 rcu_assign_pointer(tsk
->cgroups
, new_cset
);
1838 * Use move_tail so that cgroup_taskset_first() still returns the
1839 * leader after migration. This works because cgroup_migrate()
1840 * ensures that the dst_cset of the leader is the first on the
1841 * tset's dst_csets list.
1843 list_move_tail(&tsk
->cg_list
, &new_cset
->mg_tasks
);
1846 * We just gained a reference on old_cset by taking it from the
1847 * task. As trading it for new_cset is protected by cgroup_mutex,
1848 * we're safe to drop it here; it will be freed under RCU.
1850 set_bit(CGRP_RELEASABLE
, &old_cgrp
->flags
);
1851 put_css_set_locked(old_cset
, false);
1855 * cgroup_migrate_finish - cleanup after attach
1856 * @preloaded_csets: list of preloaded css_sets
1858 * Undo cgroup_migrate_add_src() and cgroup_migrate_prepare_dst(). See
1859 * those functions for details.
1861 static void cgroup_migrate_finish(struct list_head
*preloaded_csets
)
1863 struct css_set
*cset
, *tmp_cset
;
1865 lockdep_assert_held(&cgroup_mutex
);
1867 down_write(&css_set_rwsem
);
1868 list_for_each_entry_safe(cset
, tmp_cset
, preloaded_csets
, mg_preload_node
) {
1869 cset
->mg_src_cgrp
= NULL
;
1870 cset
->mg_dst_cset
= NULL
;
1871 list_del_init(&cset
->mg_preload_node
);
1872 put_css_set_locked(cset
, false);
1874 up_write(&css_set_rwsem
);
1878 * cgroup_migrate_add_src - add a migration source css_set
1879 * @src_cset: the source css_set to add
1880 * @dst_cgrp: the destination cgroup
1881 * @preloaded_csets: list of preloaded css_sets
1883 * Tasks belonging to @src_cset are about to be migrated to @dst_cgrp. Pin
1884 * @src_cset and add it to @preloaded_csets, which should later be cleaned
1885 * up by cgroup_migrate_finish().
1887 * This function may be called without holding threadgroup_lock even if the
1888 * target is a process. Threads may be created and destroyed but as long
1889 * as cgroup_mutex is not dropped, no new css_set can be put into play and
1890 * the preloaded css_sets are guaranteed to cover all migrations.
1892 static void cgroup_migrate_add_src(struct css_set
*src_cset
,
1893 struct cgroup
*dst_cgrp
,
1894 struct list_head
*preloaded_csets
)
1896 struct cgroup
*src_cgrp
;
1898 lockdep_assert_held(&cgroup_mutex
);
1899 lockdep_assert_held(&css_set_rwsem
);
1901 src_cgrp
= cset_cgroup_from_root(src_cset
, dst_cgrp
->root
);
1903 /* nothing to do if this cset already belongs to the cgroup */
1904 if (src_cgrp
== dst_cgrp
)
1907 if (!list_empty(&src_cset
->mg_preload_node
))
1910 WARN_ON(src_cset
->mg_src_cgrp
);
1911 WARN_ON(!list_empty(&src_cset
->mg_tasks
));
1912 WARN_ON(!list_empty(&src_cset
->mg_node
));
1914 src_cset
->mg_src_cgrp
= src_cgrp
;
1915 get_css_set(src_cset
);
1916 list_add(&src_cset
->mg_preload_node
, preloaded_csets
);
1920 * cgroup_migrate_prepare_dst - prepare destination css_sets for migration
1921 * @dst_cgrp: the destination cgroup
1922 * @preloaded_csets: list of preloaded source css_sets
1924 * Tasks are about to be moved to @dst_cgrp and all the source css_sets
1925 * have been preloaded to @preloaded_csets. This function looks up and
1926 * pins all destination css_sets, links each to its source, and put them on
1929 * This function must be called after cgroup_migrate_add_src() has been
1930 * called on each migration source css_set. After migration is performed
1931 * using cgroup_migrate(), cgroup_migrate_finish() must be called on
1934 static int cgroup_migrate_prepare_dst(struct cgroup
*dst_cgrp
,
1935 struct list_head
*preloaded_csets
)
1938 struct css_set
*src_cset
;
1940 lockdep_assert_held(&cgroup_mutex
);
1942 /* look up the dst cset for each src cset and link it to src */
1943 list_for_each_entry(src_cset
, preloaded_csets
, mg_preload_node
) {
1944 struct css_set
*dst_cset
;
1946 dst_cset
= find_css_set(src_cset
, dst_cgrp
);
1950 WARN_ON_ONCE(src_cset
->mg_dst_cset
|| dst_cset
->mg_dst_cset
);
1951 src_cset
->mg_dst_cset
= dst_cset
;
1953 if (list_empty(&dst_cset
->mg_preload_node
))
1954 list_add(&dst_cset
->mg_preload_node
, &csets
);
1956 put_css_set(dst_cset
, false);
1959 list_splice(&csets
, preloaded_csets
);
1962 cgroup_migrate_finish(&csets
);
1967 * cgroup_migrate - migrate a process or task to a cgroup
1968 * @cgrp: the destination cgroup
1969 * @leader: the leader of the process or the task to migrate
1970 * @threadgroup: whether @leader points to the whole process or a single task
1972 * Migrate a process or task denoted by @leader to @cgrp. If migrating a
1973 * process, the caller must be holding threadgroup_lock of @leader. The
1974 * caller is also responsible for invoking cgroup_migrate_add_src() and
1975 * cgroup_migrate_prepare_dst() on the targets before invoking this
1976 * function and following up with cgroup_migrate_finish().
1978 * As long as a controller's ->can_attach() doesn't fail, this function is
1979 * guaranteed to succeed. This means that, excluding ->can_attach()
1980 * failure, when migrating multiple targets, the success or failure can be
1981 * decided for all targets by invoking group_migrate_prepare_dst() before
1982 * actually starting migrating.
1984 static int cgroup_migrate(struct cgroup
*cgrp
, struct task_struct
*leader
,
1987 struct cgroup_taskset tset
= {
1988 .src_csets
= LIST_HEAD_INIT(tset
.src_csets
),
1989 .dst_csets
= LIST_HEAD_INIT(tset
.dst_csets
),
1990 .csets
= &tset
.src_csets
,
1992 struct cgroup_subsys_state
*css
, *failed_css
= NULL
;
1993 struct css_set
*cset
, *tmp_cset
;
1994 struct task_struct
*task
, *tmp_task
;
1998 * Prevent freeing of tasks while we take a snapshot. Tasks that are
1999 * already PF_EXITING could be freed from underneath us unless we
2000 * take an rcu_read_lock.
2002 down_write(&css_set_rwsem
);
2006 /* @task either already exited or can't exit until the end */
2007 if (task
->flags
& PF_EXITING
)
2010 /* leave @task alone if post_fork() hasn't linked it yet */
2011 if (list_empty(&task
->cg_list
))
2014 cset
= task_css_set(task
);
2015 if (!cset
->mg_src_cgrp
)
2019 * cgroup_taskset_first() must always return the leader.
2020 * Take care to avoid disturbing the ordering.
2022 list_move_tail(&task
->cg_list
, &cset
->mg_tasks
);
2023 if (list_empty(&cset
->mg_node
))
2024 list_add_tail(&cset
->mg_node
, &tset
.src_csets
);
2025 if (list_empty(&cset
->mg_dst_cset
->mg_node
))
2026 list_move_tail(&cset
->mg_dst_cset
->mg_node
,
2031 } while_each_thread(leader
, task
);
2033 up_write(&css_set_rwsem
);
2035 /* methods shouldn't be called if no task is actually migrating */
2036 if (list_empty(&tset
.src_csets
))
2039 /* check that we can legitimately attach to the cgroup */
2040 for_each_e_css(css
, i
, cgrp
) {
2041 if (css
->ss
->can_attach
) {
2042 ret
= css
->ss
->can_attach(css
, &tset
);
2045 goto out_cancel_attach
;
2051 * Now that we're guaranteed success, proceed to move all tasks to
2052 * the new cgroup. There are no failure cases after here, so this
2053 * is the commit point.
2055 down_write(&css_set_rwsem
);
2056 list_for_each_entry(cset
, &tset
.src_csets
, mg_node
) {
2057 list_for_each_entry_safe(task
, tmp_task
, &cset
->mg_tasks
, cg_list
)
2058 cgroup_task_migrate(cset
->mg_src_cgrp
, task
,
2061 up_write(&css_set_rwsem
);
2064 * Migration is committed, all target tasks are now on dst_csets.
2065 * Nothing is sensitive to fork() after this point. Notify
2066 * controllers that migration is complete.
2068 tset
.csets
= &tset
.dst_csets
;
2070 for_each_e_css(css
, i
, cgrp
)
2071 if (css
->ss
->attach
)
2072 css
->ss
->attach(css
, &tset
);
2075 goto out_release_tset
;
2078 for_each_e_css(css
, i
, cgrp
) {
2079 if (css
== failed_css
)
2081 if (css
->ss
->cancel_attach
)
2082 css
->ss
->cancel_attach(css
, &tset
);
2085 down_write(&css_set_rwsem
);
2086 list_splice_init(&tset
.dst_csets
, &tset
.src_csets
);
2087 list_for_each_entry_safe(cset
, tmp_cset
, &tset
.src_csets
, mg_node
) {
2088 list_splice_tail_init(&cset
->mg_tasks
, &cset
->tasks
);
2089 list_del_init(&cset
->mg_node
);
2091 up_write(&css_set_rwsem
);
2096 * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
2097 * @dst_cgrp: the cgroup to attach to
2098 * @leader: the task or the leader of the threadgroup to be attached
2099 * @threadgroup: attach the whole threadgroup?
2101 * Call holding cgroup_mutex and threadgroup_lock of @leader.
2103 static int cgroup_attach_task(struct cgroup
*dst_cgrp
,
2104 struct task_struct
*leader
, bool threadgroup
)
2106 LIST_HEAD(preloaded_csets
);
2107 struct task_struct
*task
;
2110 /* look up all src csets */
2111 down_read(&css_set_rwsem
);
2115 cgroup_migrate_add_src(task_css_set(task
), dst_cgrp
,
2119 } while_each_thread(leader
, task
);
2121 up_read(&css_set_rwsem
);
2123 /* prepare dst csets and commit */
2124 ret
= cgroup_migrate_prepare_dst(dst_cgrp
, &preloaded_csets
);
2126 ret
= cgroup_migrate(dst_cgrp
, leader
, threadgroup
);
2128 cgroup_migrate_finish(&preloaded_csets
);
2133 * Find the task_struct of the task to attach by vpid and pass it along to the
2134 * function to attach either it or all tasks in its threadgroup. Will lock
2135 * cgroup_mutex and threadgroup.
2137 static int attach_task_by_pid(struct cgroup
*cgrp
, u64 pid
, bool threadgroup
)
2139 struct task_struct
*tsk
;
2140 const struct cred
*cred
= current_cred(), *tcred
;
2143 if (!cgroup_lock_live_group(cgrp
))
2149 tsk
= find_task_by_vpid(pid
);
2153 goto out_unlock_cgroup
;
2156 * even if we're attaching all tasks in the thread group, we
2157 * only need to check permissions on one of them.
2159 tcred
= __task_cred(tsk
);
2160 if (!uid_eq(cred
->euid
, GLOBAL_ROOT_UID
) &&
2161 !uid_eq(cred
->euid
, tcred
->uid
) &&
2162 !uid_eq(cred
->euid
, tcred
->suid
)) {
2165 goto out_unlock_cgroup
;
2171 tsk
= tsk
->group_leader
;
2174 * Workqueue threads may acquire PF_NO_SETAFFINITY and become
2175 * trapped in a cpuset, or RT worker may be born in a cgroup
2176 * with no rt_runtime allocated. Just say no.
2178 if (tsk
== kthreadd_task
|| (tsk
->flags
& PF_NO_SETAFFINITY
)) {
2181 goto out_unlock_cgroup
;
2184 get_task_struct(tsk
);
2187 threadgroup_lock(tsk
);
2189 if (!thread_group_leader(tsk
)) {
2191 * a race with de_thread from another thread's exec()
2192 * may strip us of our leadership, if this happens,
2193 * there is no choice but to throw this task away and
2194 * try again; this is
2195 * "double-double-toil-and-trouble-check locking".
2197 threadgroup_unlock(tsk
);
2198 put_task_struct(tsk
);
2199 goto retry_find_task
;
2203 ret
= cgroup_attach_task(cgrp
, tsk
, threadgroup
);
2205 threadgroup_unlock(tsk
);
2207 put_task_struct(tsk
);
2209 mutex_unlock(&cgroup_mutex
);
2214 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
2215 * @from: attach to all cgroups of a given task
2216 * @tsk: the task to be attached
2218 int cgroup_attach_task_all(struct task_struct
*from
, struct task_struct
*tsk
)
2220 struct cgroup_root
*root
;
2223 mutex_lock(&cgroup_mutex
);
2224 for_each_root(root
) {
2225 struct cgroup
*from_cgrp
;
2227 if (root
== &cgrp_dfl_root
)
2230 down_read(&css_set_rwsem
);
2231 from_cgrp
= task_cgroup_from_root(from
, root
);
2232 up_read(&css_set_rwsem
);
2234 retval
= cgroup_attach_task(from_cgrp
, tsk
, false);
2238 mutex_unlock(&cgroup_mutex
);
2242 EXPORT_SYMBOL_GPL(cgroup_attach_task_all
);
2244 static int cgroup_tasks_write(struct cgroup_subsys_state
*css
,
2245 struct cftype
*cft
, u64 pid
)
2247 return attach_task_by_pid(css
->cgroup
, pid
, false);
2250 static int cgroup_procs_write(struct cgroup_subsys_state
*css
,
2251 struct cftype
*cft
, u64 tgid
)
2253 return attach_task_by_pid(css
->cgroup
, tgid
, true);
2256 static int cgroup_release_agent_write(struct cgroup_subsys_state
*css
,
2257 struct cftype
*cft
, char *buffer
)
2259 struct cgroup_root
*root
= css
->cgroup
->root
;
2261 BUILD_BUG_ON(sizeof(root
->release_agent_path
) < PATH_MAX
);
2262 if (!cgroup_lock_live_group(css
->cgroup
))
2264 spin_lock(&release_agent_path_lock
);
2265 strlcpy(root
->release_agent_path
, buffer
,
2266 sizeof(root
->release_agent_path
));
2267 spin_unlock(&release_agent_path_lock
);
2268 mutex_unlock(&cgroup_mutex
);
2272 static int cgroup_release_agent_show(struct seq_file
*seq
, void *v
)
2274 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2276 if (!cgroup_lock_live_group(cgrp
))
2278 seq_puts(seq
, cgrp
->root
->release_agent_path
);
2279 seq_putc(seq
, '\n');
2280 mutex_unlock(&cgroup_mutex
);
2284 static int cgroup_sane_behavior_show(struct seq_file
*seq
, void *v
)
2286 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2288 seq_printf(seq
, "%d\n", cgroup_sane_behavior(cgrp
));
2292 static ssize_t
cgroup_file_write(struct kernfs_open_file
*of
, char *buf
,
2293 size_t nbytes
, loff_t off
)
2295 struct cgroup
*cgrp
= of
->kn
->parent
->priv
;
2296 struct cftype
*cft
= of
->kn
->priv
;
2297 struct cgroup_subsys_state
*css
;
2301 * kernfs guarantees that a file isn't deleted with operations in
2302 * flight, which means that the matching css is and stays alive and
2303 * doesn't need to be pinned. The RCU locking is not necessary
2304 * either. It's just for the convenience of using cgroup_css().
2307 css
= cgroup_css(cgrp
, cft
->ss
);
2310 if (cft
->write_string
) {
2311 ret
= cft
->write_string(css
, cft
, strstrip(buf
));
2312 } else if (cft
->write_u64
) {
2313 unsigned long long v
;
2314 ret
= kstrtoull(buf
, 0, &v
);
2316 ret
= cft
->write_u64(css
, cft
, v
);
2317 } else if (cft
->write_s64
) {
2319 ret
= kstrtoll(buf
, 0, &v
);
2321 ret
= cft
->write_s64(css
, cft
, v
);
2322 } else if (cft
->trigger
) {
2323 ret
= cft
->trigger(css
, (unsigned int)cft
->private);
2328 return ret
?: nbytes
;
2331 static void *cgroup_seqfile_start(struct seq_file
*seq
, loff_t
*ppos
)
2333 return seq_cft(seq
)->seq_start(seq
, ppos
);
2336 static void *cgroup_seqfile_next(struct seq_file
*seq
, void *v
, loff_t
*ppos
)
2338 return seq_cft(seq
)->seq_next(seq
, v
, ppos
);
2341 static void cgroup_seqfile_stop(struct seq_file
*seq
, void *v
)
2343 seq_cft(seq
)->seq_stop(seq
, v
);
2346 static int cgroup_seqfile_show(struct seq_file
*m
, void *arg
)
2348 struct cftype
*cft
= seq_cft(m
);
2349 struct cgroup_subsys_state
*css
= seq_css(m
);
2352 return cft
->seq_show(m
, arg
);
2355 seq_printf(m
, "%llu\n", cft
->read_u64(css
, cft
));
2356 else if (cft
->read_s64
)
2357 seq_printf(m
, "%lld\n", cft
->read_s64(css
, cft
));
2363 static struct kernfs_ops cgroup_kf_single_ops
= {
2364 .atomic_write_len
= PAGE_SIZE
,
2365 .write
= cgroup_file_write
,
2366 .seq_show
= cgroup_seqfile_show
,
2369 static struct kernfs_ops cgroup_kf_ops
= {
2370 .atomic_write_len
= PAGE_SIZE
,
2371 .write
= cgroup_file_write
,
2372 .seq_start
= cgroup_seqfile_start
,
2373 .seq_next
= cgroup_seqfile_next
,
2374 .seq_stop
= cgroup_seqfile_stop
,
2375 .seq_show
= cgroup_seqfile_show
,
2379 * cgroup_rename - Only allow simple rename of directories in place.
2381 static int cgroup_rename(struct kernfs_node
*kn
, struct kernfs_node
*new_parent
,
2382 const char *new_name_str
)
2384 struct cgroup
*cgrp
= kn
->priv
;
2387 if (kernfs_type(kn
) != KERNFS_DIR
)
2389 if (kn
->parent
!= new_parent
)
2393 * This isn't a proper migration and its usefulness is very
2394 * limited. Disallow if sane_behavior.
2396 if (cgroup_sane_behavior(cgrp
))
2400 * We're gonna grab cgroup_tree_mutex which nests outside kernfs
2401 * active_ref. kernfs_rename() doesn't require active_ref
2402 * protection. Break them before grabbing cgroup_tree_mutex.
2404 kernfs_break_active_protection(new_parent
);
2405 kernfs_break_active_protection(kn
);
2407 mutex_lock(&cgroup_tree_mutex
);
2408 mutex_lock(&cgroup_mutex
);
2410 ret
= kernfs_rename(kn
, new_parent
, new_name_str
);
2412 mutex_unlock(&cgroup_mutex
);
2413 mutex_unlock(&cgroup_tree_mutex
);
2415 kernfs_unbreak_active_protection(kn
);
2416 kernfs_unbreak_active_protection(new_parent
);
2420 /* set uid and gid of cgroup dirs and files to that of the creator */
2421 static int cgroup_kn_set_ugid(struct kernfs_node
*kn
)
2423 struct iattr iattr
= { .ia_valid
= ATTR_UID
| ATTR_GID
,
2424 .ia_uid
= current_fsuid(),
2425 .ia_gid
= current_fsgid(), };
2427 if (uid_eq(iattr
.ia_uid
, GLOBAL_ROOT_UID
) &&
2428 gid_eq(iattr
.ia_gid
, GLOBAL_ROOT_GID
))
2431 return kernfs_setattr(kn
, &iattr
);
2434 static int cgroup_add_file(struct cgroup
*cgrp
, struct cftype
*cft
)
2436 char name
[CGROUP_FILE_NAME_MAX
];
2437 struct kernfs_node
*kn
;
2438 struct lock_class_key
*key
= NULL
;
2441 #ifdef CONFIG_DEBUG_LOCK_ALLOC
2442 key
= &cft
->lockdep_key
;
2444 kn
= __kernfs_create_file(cgrp
->kn
, cgroup_file_name(cgrp
, cft
, name
),
2445 cgroup_file_mode(cft
), 0, cft
->kf_ops
, cft
,
2450 ret
= cgroup_kn_set_ugid(kn
);
2457 * cgroup_addrm_files - add or remove files to a cgroup directory
2458 * @cgrp: the target cgroup
2459 * @cfts: array of cftypes to be added
2460 * @is_add: whether to add or remove
2462 * Depending on @is_add, add or remove files defined by @cfts on @cgrp.
2463 * For removals, this function never fails. If addition fails, this
2464 * function doesn't remove files already added. The caller is responsible
2467 static int cgroup_addrm_files(struct cgroup
*cgrp
, struct cftype cfts
[],
2473 lockdep_assert_held(&cgroup_tree_mutex
);
2475 for (cft
= cfts
; cft
->name
[0] != '\0'; cft
++) {
2476 /* does cft->flags tell us to skip this file on @cgrp? */
2477 if ((cft
->flags
& CFTYPE_ONLY_ON_DFL
) && !cgroup_on_dfl(cgrp
))
2479 if ((cft
->flags
& CFTYPE_INSANE
) && cgroup_sane_behavior(cgrp
))
2481 if ((cft
->flags
& CFTYPE_NOT_ON_ROOT
) && !cgrp
->parent
)
2483 if ((cft
->flags
& CFTYPE_ONLY_ON_ROOT
) && cgrp
->parent
)
2487 ret
= cgroup_add_file(cgrp
, cft
);
2489 pr_warn("cgroup_addrm_files: failed to add %s, err=%d\n",
2494 cgroup_rm_file(cgrp
, cft
);
2500 static int cgroup_apply_cftypes(struct cftype
*cfts
, bool is_add
)
2503 struct cgroup_subsys
*ss
= cfts
[0].ss
;
2504 struct cgroup
*root
= &ss
->root
->cgrp
;
2505 struct cgroup_subsys_state
*css
;
2508 lockdep_assert_held(&cgroup_tree_mutex
);
2510 /* add/rm files for all cgroups created before */
2511 css_for_each_descendant_pre(css
, cgroup_css(root
, ss
)) {
2512 struct cgroup
*cgrp
= css
->cgroup
;
2514 if (cgroup_is_dead(cgrp
))
2517 ret
= cgroup_addrm_files(cgrp
, cfts
, is_add
);
2523 kernfs_activate(root
->kn
);
2527 static void cgroup_exit_cftypes(struct cftype
*cfts
)
2531 for (cft
= cfts
; cft
->name
[0] != '\0'; cft
++) {
2532 /* free copy for custom atomic_write_len, see init_cftypes() */
2533 if (cft
->max_write_len
&& cft
->max_write_len
!= PAGE_SIZE
)
2540 static int cgroup_init_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
2544 for (cft
= cfts
; cft
->name
[0] != '\0'; cft
++) {
2545 struct kernfs_ops
*kf_ops
;
2547 WARN_ON(cft
->ss
|| cft
->kf_ops
);
2550 kf_ops
= &cgroup_kf_ops
;
2552 kf_ops
= &cgroup_kf_single_ops
;
2555 * Ugh... if @cft wants a custom max_write_len, we need to
2556 * make a copy of kf_ops to set its atomic_write_len.
2558 if (cft
->max_write_len
&& cft
->max_write_len
!= PAGE_SIZE
) {
2559 kf_ops
= kmemdup(kf_ops
, sizeof(*kf_ops
), GFP_KERNEL
);
2561 cgroup_exit_cftypes(cfts
);
2564 kf_ops
->atomic_write_len
= cft
->max_write_len
;
2567 cft
->kf_ops
= kf_ops
;
2574 static int cgroup_rm_cftypes_locked(struct cftype
*cfts
)
2576 lockdep_assert_held(&cgroup_tree_mutex
);
2578 if (!cfts
|| !cfts
[0].ss
)
2581 list_del(&cfts
->node
);
2582 cgroup_apply_cftypes(cfts
, false);
2583 cgroup_exit_cftypes(cfts
);
2588 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
2589 * @cfts: zero-length name terminated array of cftypes
2591 * Unregister @cfts. Files described by @cfts are removed from all
2592 * existing cgroups and all future cgroups won't have them either. This
2593 * function can be called anytime whether @cfts' subsys is attached or not.
2595 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
2598 int cgroup_rm_cftypes(struct cftype
*cfts
)
2602 mutex_lock(&cgroup_tree_mutex
);
2603 ret
= cgroup_rm_cftypes_locked(cfts
);
2604 mutex_unlock(&cgroup_tree_mutex
);
2609 * cgroup_add_cftypes - add an array of cftypes to a subsystem
2610 * @ss: target cgroup subsystem
2611 * @cfts: zero-length name terminated array of cftypes
2613 * Register @cfts to @ss. Files described by @cfts are created for all
2614 * existing cgroups to which @ss is attached and all future cgroups will
2615 * have them too. This function can be called anytime whether @ss is
2618 * Returns 0 on successful registration, -errno on failure. Note that this
2619 * function currently returns 0 as long as @cfts registration is successful
2620 * even if some file creation attempts on existing cgroups fail.
2622 int cgroup_add_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
2626 if (!cfts
|| cfts
[0].name
[0] == '\0')
2629 ret
= cgroup_init_cftypes(ss
, cfts
);
2633 mutex_lock(&cgroup_tree_mutex
);
2635 list_add_tail(&cfts
->node
, &ss
->cfts
);
2636 ret
= cgroup_apply_cftypes(cfts
, true);
2638 cgroup_rm_cftypes_locked(cfts
);
2640 mutex_unlock(&cgroup_tree_mutex
);
2645 * cgroup_task_count - count the number of tasks in a cgroup.
2646 * @cgrp: the cgroup in question
2648 * Return the number of tasks in the cgroup.
2650 static int cgroup_task_count(const struct cgroup
*cgrp
)
2653 struct cgrp_cset_link
*link
;
2655 down_read(&css_set_rwsem
);
2656 list_for_each_entry(link
, &cgrp
->cset_links
, cset_link
)
2657 count
+= atomic_read(&link
->cset
->refcount
);
2658 up_read(&css_set_rwsem
);
2663 * css_next_child - find the next child of a given css
2664 * @pos_css: the current position (%NULL to initiate traversal)
2665 * @parent_css: css whose children to walk
2667 * This function returns the next child of @parent_css and should be called
2668 * under either cgroup_mutex or RCU read lock. The only requirement is
2669 * that @parent_css and @pos_css are accessible. The next sibling is
2670 * guaranteed to be returned regardless of their states.
2672 struct cgroup_subsys_state
*
2673 css_next_child(struct cgroup_subsys_state
*pos_css
,
2674 struct cgroup_subsys_state
*parent_css
)
2676 struct cgroup
*pos
= pos_css
? pos_css
->cgroup
: NULL
;
2677 struct cgroup
*cgrp
= parent_css
->cgroup
;
2678 struct cgroup
*next
;
2680 cgroup_assert_mutexes_or_rcu_locked();
2683 * @pos could already have been removed. Once a cgroup is removed,
2684 * its ->sibling.next is no longer updated when its next sibling
2685 * changes. As CGRP_DEAD assertion is serialized and happens
2686 * before the cgroup is taken off the ->sibling list, if we see it
2687 * unasserted, it's guaranteed that the next sibling hasn't
2688 * finished its grace period even if it's already removed, and thus
2689 * safe to dereference from this RCU critical section. If
2690 * ->sibling.next is inaccessible, cgroup_is_dead() is guaranteed
2691 * to be visible as %true here.
2693 * If @pos is dead, its next pointer can't be dereferenced;
2694 * however, as each cgroup is given a monotonically increasing
2695 * unique serial number and always appended to the sibling list,
2696 * the next one can be found by walking the parent's children until
2697 * we see a cgroup with higher serial number than @pos's. While
2698 * this path can be slower, it's taken only when either the current
2699 * cgroup is removed or iteration and removal race.
2702 next
= list_entry_rcu(cgrp
->children
.next
, struct cgroup
, sibling
);
2703 } else if (likely(!cgroup_is_dead(pos
))) {
2704 next
= list_entry_rcu(pos
->sibling
.next
, struct cgroup
, sibling
);
2706 list_for_each_entry_rcu(next
, &cgrp
->children
, sibling
)
2707 if (next
->serial_nr
> pos
->serial_nr
)
2711 if (&next
->sibling
== &cgrp
->children
)
2714 return cgroup_css(next
, parent_css
->ss
);
2718 * css_next_descendant_pre - find the next descendant for pre-order walk
2719 * @pos: the current position (%NULL to initiate traversal)
2720 * @root: css whose descendants to walk
2722 * To be used by css_for_each_descendant_pre(). Find the next descendant
2723 * to visit for pre-order traversal of @root's descendants. @root is
2724 * included in the iteration and the first node to be visited.
2726 * While this function requires cgroup_mutex or RCU read locking, it
2727 * doesn't require the whole traversal to be contained in a single critical
2728 * section. This function will return the correct next descendant as long
2729 * as both @pos and @root are accessible and @pos is a descendant of @root.
2731 struct cgroup_subsys_state
*
2732 css_next_descendant_pre(struct cgroup_subsys_state
*pos
,
2733 struct cgroup_subsys_state
*root
)
2735 struct cgroup_subsys_state
*next
;
2737 cgroup_assert_mutexes_or_rcu_locked();
2739 /* if first iteration, visit @root */
2743 /* visit the first child if exists */
2744 next
= css_next_child(NULL
, pos
);
2748 /* no child, visit my or the closest ancestor's next sibling */
2749 while (pos
!= root
) {
2750 next
= css_next_child(pos
, css_parent(pos
));
2753 pos
= css_parent(pos
);
2760 * css_rightmost_descendant - return the rightmost descendant of a css
2761 * @pos: css of interest
2763 * Return the rightmost descendant of @pos. If there's no descendant, @pos
2764 * is returned. This can be used during pre-order traversal to skip
2767 * While this function requires cgroup_mutex or RCU read locking, it
2768 * doesn't require the whole traversal to be contained in a single critical
2769 * section. This function will return the correct rightmost descendant as
2770 * long as @pos is accessible.
2772 struct cgroup_subsys_state
*
2773 css_rightmost_descendant(struct cgroup_subsys_state
*pos
)
2775 struct cgroup_subsys_state
*last
, *tmp
;
2777 cgroup_assert_mutexes_or_rcu_locked();
2781 /* ->prev isn't RCU safe, walk ->next till the end */
2783 css_for_each_child(tmp
, last
)
2790 static struct cgroup_subsys_state
*
2791 css_leftmost_descendant(struct cgroup_subsys_state
*pos
)
2793 struct cgroup_subsys_state
*last
;
2797 pos
= css_next_child(NULL
, pos
);
2804 * css_next_descendant_post - find the next descendant for post-order walk
2805 * @pos: the current position (%NULL to initiate traversal)
2806 * @root: css whose descendants to walk
2808 * To be used by css_for_each_descendant_post(). Find the next descendant
2809 * to visit for post-order traversal of @root's descendants. @root is
2810 * included in the iteration and the last node to be visited.
2812 * While this function requires cgroup_mutex or RCU read locking, it
2813 * doesn't require the whole traversal to be contained in a single critical
2814 * section. This function will return the correct next descendant as long
2815 * as both @pos and @cgroup are accessible and @pos is a descendant of
2818 struct cgroup_subsys_state
*
2819 css_next_descendant_post(struct cgroup_subsys_state
*pos
,
2820 struct cgroup_subsys_state
*root
)
2822 struct cgroup_subsys_state
*next
;
2824 cgroup_assert_mutexes_or_rcu_locked();
2826 /* if first iteration, visit leftmost descendant which may be @root */
2828 return css_leftmost_descendant(root
);
2830 /* if we visited @root, we're done */
2834 /* if there's an unvisited sibling, visit its leftmost descendant */
2835 next
= css_next_child(pos
, css_parent(pos
));
2837 return css_leftmost_descendant(next
);
2839 /* no sibling left, visit parent */
2840 return css_parent(pos
);
2844 * css_advance_task_iter - advance a task itererator to the next css_set
2845 * @it: the iterator to advance
2847 * Advance @it to the next css_set to walk.
2849 static void css_advance_task_iter(struct css_task_iter
*it
)
2851 struct list_head
*l
= it
->cset_link
;
2852 struct cgrp_cset_link
*link
;
2853 struct css_set
*cset
;
2855 /* Advance to the next non-empty css_set */
2858 if (l
== &it
->origin_css
->cgroup
->cset_links
) {
2859 it
->cset_link
= NULL
;
2862 link
= list_entry(l
, struct cgrp_cset_link
, cset_link
);
2864 } while (list_empty(&cset
->tasks
) && list_empty(&cset
->mg_tasks
));
2868 if (!list_empty(&cset
->tasks
))
2869 it
->task
= cset
->tasks
.next
;
2871 it
->task
= cset
->mg_tasks
.next
;
2875 * css_task_iter_start - initiate task iteration
2876 * @css: the css to walk tasks of
2877 * @it: the task iterator to use
2879 * Initiate iteration through the tasks of @css. The caller can call
2880 * css_task_iter_next() to walk through the tasks until the function
2881 * returns NULL. On completion of iteration, css_task_iter_end() must be
2884 * Note that this function acquires a lock which is released when the
2885 * iteration finishes. The caller can't sleep while iteration is in
2888 void css_task_iter_start(struct cgroup_subsys_state
*css
,
2889 struct css_task_iter
*it
)
2890 __acquires(css_set_rwsem
)
2892 /* no one should try to iterate before mounting cgroups */
2893 WARN_ON_ONCE(!use_task_css_set_links
);
2895 down_read(&css_set_rwsem
);
2897 it
->origin_css
= css
;
2898 it
->cset_link
= &css
->cgroup
->cset_links
;
2900 css_advance_task_iter(it
);
2904 * css_task_iter_next - return the next task for the iterator
2905 * @it: the task iterator being iterated
2907 * The "next" function for task iteration. @it should have been
2908 * initialized via css_task_iter_start(). Returns NULL when the iteration
2911 struct task_struct
*css_task_iter_next(struct css_task_iter
*it
)
2913 struct task_struct
*res
;
2914 struct list_head
*l
= it
->task
;
2915 struct cgrp_cset_link
*link
= list_entry(it
->cset_link
,
2916 struct cgrp_cset_link
, cset_link
);
2918 /* If the iterator cg is NULL, we have no tasks */
2921 res
= list_entry(l
, struct task_struct
, cg_list
);
2924 * Advance iterator to find next entry. cset->tasks is consumed
2925 * first and then ->mg_tasks. After ->mg_tasks, we move onto the
2930 if (l
== &link
->cset
->tasks
)
2931 l
= link
->cset
->mg_tasks
.next
;
2933 if (l
== &link
->cset
->mg_tasks
)
2934 css_advance_task_iter(it
);
2942 * css_task_iter_end - finish task iteration
2943 * @it: the task iterator to finish
2945 * Finish task iteration started by css_task_iter_start().
2947 void css_task_iter_end(struct css_task_iter
*it
)
2948 __releases(css_set_rwsem
)
2950 up_read(&css_set_rwsem
);
2954 * cgroup_trasnsfer_tasks - move tasks from one cgroup to another
2955 * @to: cgroup to which the tasks will be moved
2956 * @from: cgroup in which the tasks currently reside
2958 * Locking rules between cgroup_post_fork() and the migration path
2959 * guarantee that, if a task is forking while being migrated, the new child
2960 * is guaranteed to be either visible in the source cgroup after the
2961 * parent's migration is complete or put into the target cgroup. No task
2962 * can slip out of migration through forking.
2964 int cgroup_transfer_tasks(struct cgroup
*to
, struct cgroup
*from
)
2966 LIST_HEAD(preloaded_csets
);
2967 struct cgrp_cset_link
*link
;
2968 struct css_task_iter it
;
2969 struct task_struct
*task
;
2972 mutex_lock(&cgroup_mutex
);
2974 /* all tasks in @from are being moved, all csets are source */
2975 down_read(&css_set_rwsem
);
2976 list_for_each_entry(link
, &from
->cset_links
, cset_link
)
2977 cgroup_migrate_add_src(link
->cset
, to
, &preloaded_csets
);
2978 up_read(&css_set_rwsem
);
2980 ret
= cgroup_migrate_prepare_dst(to
, &preloaded_csets
);
2985 * Migrate tasks one-by-one until @form is empty. This fails iff
2986 * ->can_attach() fails.
2989 css_task_iter_start(&from
->dummy_css
, &it
);
2990 task
= css_task_iter_next(&it
);
2992 get_task_struct(task
);
2993 css_task_iter_end(&it
);
2996 ret
= cgroup_migrate(to
, task
, false);
2997 put_task_struct(task
);
2999 } while (task
&& !ret
);
3001 cgroup_migrate_finish(&preloaded_csets
);
3002 mutex_unlock(&cgroup_mutex
);
3007 * Stuff for reading the 'tasks'/'procs' files.
3009 * Reading this file can return large amounts of data if a cgroup has
3010 * *lots* of attached tasks. So it may need several calls to read(),
3011 * but we cannot guarantee that the information we produce is correct
3012 * unless we produce it entirely atomically.
3016 /* which pidlist file are we talking about? */
3017 enum cgroup_filetype
{
3023 * A pidlist is a list of pids that virtually represents the contents of one
3024 * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
3025 * a pair (one each for procs, tasks) for each pid namespace that's relevant
3028 struct cgroup_pidlist
{
3030 * used to find which pidlist is wanted. doesn't change as long as
3031 * this particular list stays in the list.
3033 struct { enum cgroup_filetype type
; struct pid_namespace
*ns
; } key
;
3036 /* how many elements the above list has */
3038 /* each of these stored in a list by its cgroup */
3039 struct list_head links
;
3040 /* pointer to the cgroup we belong to, for list removal purposes */
3041 struct cgroup
*owner
;
3042 /* for delayed destruction */
3043 struct delayed_work destroy_dwork
;
3047 * The following two functions "fix" the issue where there are more pids
3048 * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
3049 * TODO: replace with a kernel-wide solution to this problem
3051 #define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
3052 static void *pidlist_allocate(int count
)
3054 if (PIDLIST_TOO_LARGE(count
))
3055 return vmalloc(count
* sizeof(pid_t
));
3057 return kmalloc(count
* sizeof(pid_t
), GFP_KERNEL
);
3060 static void pidlist_free(void *p
)
3062 if (is_vmalloc_addr(p
))
3069 * Used to destroy all pidlists lingering waiting for destroy timer. None
3070 * should be left afterwards.
3072 static void cgroup_pidlist_destroy_all(struct cgroup
*cgrp
)
3074 struct cgroup_pidlist
*l
, *tmp_l
;
3076 mutex_lock(&cgrp
->pidlist_mutex
);
3077 list_for_each_entry_safe(l
, tmp_l
, &cgrp
->pidlists
, links
)
3078 mod_delayed_work(cgroup_pidlist_destroy_wq
, &l
->destroy_dwork
, 0);
3079 mutex_unlock(&cgrp
->pidlist_mutex
);
3081 flush_workqueue(cgroup_pidlist_destroy_wq
);
3082 BUG_ON(!list_empty(&cgrp
->pidlists
));
3085 static void cgroup_pidlist_destroy_work_fn(struct work_struct
*work
)
3087 struct delayed_work
*dwork
= to_delayed_work(work
);
3088 struct cgroup_pidlist
*l
= container_of(dwork
, struct cgroup_pidlist
,
3090 struct cgroup_pidlist
*tofree
= NULL
;
3092 mutex_lock(&l
->owner
->pidlist_mutex
);
3095 * Destroy iff we didn't get queued again. The state won't change
3096 * as destroy_dwork can only be queued while locked.
3098 if (!delayed_work_pending(dwork
)) {
3099 list_del(&l
->links
);
3100 pidlist_free(l
->list
);
3101 put_pid_ns(l
->key
.ns
);
3105 mutex_unlock(&l
->owner
->pidlist_mutex
);
3110 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
3111 * Returns the number of unique elements.
3113 static int pidlist_uniq(pid_t
*list
, int length
)
3118 * we presume the 0th element is unique, so i starts at 1. trivial
3119 * edge cases first; no work needs to be done for either
3121 if (length
== 0 || length
== 1)
3123 /* src and dest walk down the list; dest counts unique elements */
3124 for (src
= 1; src
< length
; src
++) {
3125 /* find next unique element */
3126 while (list
[src
] == list
[src
-1]) {
3131 /* dest always points to where the next unique element goes */
3132 list
[dest
] = list
[src
];
3140 * The two pid files - task and cgroup.procs - guaranteed that the result
3141 * is sorted, which forced this whole pidlist fiasco. As pid order is
3142 * different per namespace, each namespace needs differently sorted list,
3143 * making it impossible to use, for example, single rbtree of member tasks
3144 * sorted by task pointer. As pidlists can be fairly large, allocating one
3145 * per open file is dangerous, so cgroup had to implement shared pool of
3146 * pidlists keyed by cgroup and namespace.
3148 * All this extra complexity was caused by the original implementation
3149 * committing to an entirely unnecessary property. In the long term, we
3150 * want to do away with it. Explicitly scramble sort order if
3151 * sane_behavior so that no such expectation exists in the new interface.
3153 * Scrambling is done by swapping every two consecutive bits, which is
3154 * non-identity one-to-one mapping which disturbs sort order sufficiently.
3156 static pid_t
pid_fry(pid_t pid
)
3158 unsigned a
= pid
& 0x55555555;
3159 unsigned b
= pid
& 0xAAAAAAAA;
3161 return (a
<< 1) | (b
>> 1);
3164 static pid_t
cgroup_pid_fry(struct cgroup
*cgrp
, pid_t pid
)
3166 if (cgroup_sane_behavior(cgrp
))
3167 return pid_fry(pid
);
3172 static int cmppid(const void *a
, const void *b
)
3174 return *(pid_t
*)a
- *(pid_t
*)b
;
3177 static int fried_cmppid(const void *a
, const void *b
)
3179 return pid_fry(*(pid_t
*)a
) - pid_fry(*(pid_t
*)b
);
3182 static struct cgroup_pidlist
*cgroup_pidlist_find(struct cgroup
*cgrp
,
3183 enum cgroup_filetype type
)
3185 struct cgroup_pidlist
*l
;
3186 /* don't need task_nsproxy() if we're looking at ourself */
3187 struct pid_namespace
*ns
= task_active_pid_ns(current
);
3189 lockdep_assert_held(&cgrp
->pidlist_mutex
);
3191 list_for_each_entry(l
, &cgrp
->pidlists
, links
)
3192 if (l
->key
.type
== type
&& l
->key
.ns
== ns
)
3198 * find the appropriate pidlist for our purpose (given procs vs tasks)
3199 * returns with the lock on that pidlist already held, and takes care
3200 * of the use count, or returns NULL with no locks held if we're out of
3203 static struct cgroup_pidlist
*cgroup_pidlist_find_create(struct cgroup
*cgrp
,
3204 enum cgroup_filetype type
)
3206 struct cgroup_pidlist
*l
;
3208 lockdep_assert_held(&cgrp
->pidlist_mutex
);
3210 l
= cgroup_pidlist_find(cgrp
, type
);
3214 /* entry not found; create a new one */
3215 l
= kzalloc(sizeof(struct cgroup_pidlist
), GFP_KERNEL
);
3219 INIT_DELAYED_WORK(&l
->destroy_dwork
, cgroup_pidlist_destroy_work_fn
);
3221 /* don't need task_nsproxy() if we're looking at ourself */
3222 l
->key
.ns
= get_pid_ns(task_active_pid_ns(current
));
3224 list_add(&l
->links
, &cgrp
->pidlists
);
3229 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
3231 static int pidlist_array_load(struct cgroup
*cgrp
, enum cgroup_filetype type
,
3232 struct cgroup_pidlist
**lp
)
3236 int pid
, n
= 0; /* used for populating the array */
3237 struct css_task_iter it
;
3238 struct task_struct
*tsk
;
3239 struct cgroup_pidlist
*l
;
3241 lockdep_assert_held(&cgrp
->pidlist_mutex
);
3244 * If cgroup gets more users after we read count, we won't have
3245 * enough space - tough. This race is indistinguishable to the
3246 * caller from the case that the additional cgroup users didn't
3247 * show up until sometime later on.
3249 length
= cgroup_task_count(cgrp
);
3250 array
= pidlist_allocate(length
);
3253 /* now, populate the array */
3254 css_task_iter_start(&cgrp
->dummy_css
, &it
);
3255 while ((tsk
= css_task_iter_next(&it
))) {
3256 if (unlikely(n
== length
))
3258 /* get tgid or pid for procs or tasks file respectively */
3259 if (type
== CGROUP_FILE_PROCS
)
3260 pid
= task_tgid_vnr(tsk
);
3262 pid
= task_pid_vnr(tsk
);
3263 if (pid
> 0) /* make sure to only use valid results */
3266 css_task_iter_end(&it
);
3268 /* now sort & (if procs) strip out duplicates */
3269 if (cgroup_sane_behavior(cgrp
))
3270 sort(array
, length
, sizeof(pid_t
), fried_cmppid
, NULL
);
3272 sort(array
, length
, sizeof(pid_t
), cmppid
, NULL
);
3273 if (type
== CGROUP_FILE_PROCS
)
3274 length
= pidlist_uniq(array
, length
);
3276 l
= cgroup_pidlist_find_create(cgrp
, type
);
3278 mutex_unlock(&cgrp
->pidlist_mutex
);
3279 pidlist_free(array
);
3283 /* store array, freeing old if necessary */
3284 pidlist_free(l
->list
);
3292 * cgroupstats_build - build and fill cgroupstats
3293 * @stats: cgroupstats to fill information into
3294 * @dentry: A dentry entry belonging to the cgroup for which stats have
3297 * Build and fill cgroupstats so that taskstats can export it to user
3300 int cgroupstats_build(struct cgroupstats
*stats
, struct dentry
*dentry
)
3302 struct kernfs_node
*kn
= kernfs_node_from_dentry(dentry
);
3303 struct cgroup
*cgrp
;
3304 struct css_task_iter it
;
3305 struct task_struct
*tsk
;
3307 /* it should be kernfs_node belonging to cgroupfs and is a directory */
3308 if (dentry
->d_sb
->s_type
!= &cgroup_fs_type
|| !kn
||
3309 kernfs_type(kn
) != KERNFS_DIR
)
3312 mutex_lock(&cgroup_mutex
);
3315 * We aren't being called from kernfs and there's no guarantee on
3316 * @kn->priv's validity. For this and css_tryget_from_dir(),
3317 * @kn->priv is RCU safe. Let's do the RCU dancing.
3320 cgrp
= rcu_dereference(kn
->priv
);
3321 if (!cgrp
|| cgroup_is_dead(cgrp
)) {
3323 mutex_unlock(&cgroup_mutex
);
3328 css_task_iter_start(&cgrp
->dummy_css
, &it
);
3329 while ((tsk
= css_task_iter_next(&it
))) {
3330 switch (tsk
->state
) {
3332 stats
->nr_running
++;
3334 case TASK_INTERRUPTIBLE
:
3335 stats
->nr_sleeping
++;
3337 case TASK_UNINTERRUPTIBLE
:
3338 stats
->nr_uninterruptible
++;
3341 stats
->nr_stopped
++;
3344 if (delayacct_is_task_waiting_on_io(tsk
))
3345 stats
->nr_io_wait
++;
3349 css_task_iter_end(&it
);
3351 mutex_unlock(&cgroup_mutex
);
3357 * seq_file methods for the tasks/procs files. The seq_file position is the
3358 * next pid to display; the seq_file iterator is a pointer to the pid
3359 * in the cgroup->l->list array.
3362 static void *cgroup_pidlist_start(struct seq_file
*s
, loff_t
*pos
)
3365 * Initially we receive a position value that corresponds to
3366 * one more than the last pid shown (or 0 on the first call or
3367 * after a seek to the start). Use a binary-search to find the
3368 * next pid to display, if any
3370 struct kernfs_open_file
*of
= s
->private;
3371 struct cgroup
*cgrp
= seq_css(s
)->cgroup
;
3372 struct cgroup_pidlist
*l
;
3373 enum cgroup_filetype type
= seq_cft(s
)->private;
3374 int index
= 0, pid
= *pos
;
3377 mutex_lock(&cgrp
->pidlist_mutex
);
3380 * !NULL @of->priv indicates that this isn't the first start()
3381 * after open. If the matching pidlist is around, we can use that.
3382 * Look for it. Note that @of->priv can't be used directly. It
3383 * could already have been destroyed.
3386 of
->priv
= cgroup_pidlist_find(cgrp
, type
);
3389 * Either this is the first start() after open or the matching
3390 * pidlist has been destroyed inbetween. Create a new one.
3393 ret
= pidlist_array_load(cgrp
, type
,
3394 (struct cgroup_pidlist
**)&of
->priv
);
3396 return ERR_PTR(ret
);
3401 int end
= l
->length
;
3403 while (index
< end
) {
3404 int mid
= (index
+ end
) / 2;
3405 if (cgroup_pid_fry(cgrp
, l
->list
[mid
]) == pid
) {
3408 } else if (cgroup_pid_fry(cgrp
, l
->list
[mid
]) <= pid
)
3414 /* If we're off the end of the array, we're done */
3415 if (index
>= l
->length
)
3417 /* Update the abstract position to be the actual pid that we found */
3418 iter
= l
->list
+ index
;
3419 *pos
= cgroup_pid_fry(cgrp
, *iter
);
3423 static void cgroup_pidlist_stop(struct seq_file
*s
, void *v
)
3425 struct kernfs_open_file
*of
= s
->private;
3426 struct cgroup_pidlist
*l
= of
->priv
;
3429 mod_delayed_work(cgroup_pidlist_destroy_wq
, &l
->destroy_dwork
,
3430 CGROUP_PIDLIST_DESTROY_DELAY
);
3431 mutex_unlock(&seq_css(s
)->cgroup
->pidlist_mutex
);
3434 static void *cgroup_pidlist_next(struct seq_file
*s
, void *v
, loff_t
*pos
)
3436 struct kernfs_open_file
*of
= s
->private;
3437 struct cgroup_pidlist
*l
= of
->priv
;
3439 pid_t
*end
= l
->list
+ l
->length
;
3441 * Advance to the next pid in the array. If this goes off the
3448 *pos
= cgroup_pid_fry(seq_css(s
)->cgroup
, *p
);
3453 static int cgroup_pidlist_show(struct seq_file
*s
, void *v
)
3455 return seq_printf(s
, "%d\n", *(int *)v
);
3459 * seq_operations functions for iterating on pidlists through seq_file -
3460 * independent of whether it's tasks or procs
3462 static const struct seq_operations cgroup_pidlist_seq_operations
= {
3463 .start
= cgroup_pidlist_start
,
3464 .stop
= cgroup_pidlist_stop
,
3465 .next
= cgroup_pidlist_next
,
3466 .show
= cgroup_pidlist_show
,
3469 static u64
cgroup_read_notify_on_release(struct cgroup_subsys_state
*css
,
3472 return notify_on_release(css
->cgroup
);
3475 static int cgroup_write_notify_on_release(struct cgroup_subsys_state
*css
,
3476 struct cftype
*cft
, u64 val
)
3478 clear_bit(CGRP_RELEASABLE
, &css
->cgroup
->flags
);
3480 set_bit(CGRP_NOTIFY_ON_RELEASE
, &css
->cgroup
->flags
);
3482 clear_bit(CGRP_NOTIFY_ON_RELEASE
, &css
->cgroup
->flags
);
3486 static u64
cgroup_clone_children_read(struct cgroup_subsys_state
*css
,
3489 return test_bit(CGRP_CPUSET_CLONE_CHILDREN
, &css
->cgroup
->flags
);
3492 static int cgroup_clone_children_write(struct cgroup_subsys_state
*css
,
3493 struct cftype
*cft
, u64 val
)
3496 set_bit(CGRP_CPUSET_CLONE_CHILDREN
, &css
->cgroup
->flags
);
3498 clear_bit(CGRP_CPUSET_CLONE_CHILDREN
, &css
->cgroup
->flags
);
3502 static struct cftype cgroup_base_files
[] = {
3504 .name
= "cgroup.procs",
3505 .seq_start
= cgroup_pidlist_start
,
3506 .seq_next
= cgroup_pidlist_next
,
3507 .seq_stop
= cgroup_pidlist_stop
,
3508 .seq_show
= cgroup_pidlist_show
,
3509 .private = CGROUP_FILE_PROCS
,
3510 .write_u64
= cgroup_procs_write
,
3511 .mode
= S_IRUGO
| S_IWUSR
,
3514 .name
= "cgroup.clone_children",
3515 .flags
= CFTYPE_INSANE
,
3516 .read_u64
= cgroup_clone_children_read
,
3517 .write_u64
= cgroup_clone_children_write
,
3520 .name
= "cgroup.sane_behavior",
3521 .flags
= CFTYPE_ONLY_ON_ROOT
,
3522 .seq_show
= cgroup_sane_behavior_show
,
3526 * Historical crazy stuff. These don't have "cgroup." prefix and
3527 * don't exist if sane_behavior. If you're depending on these, be
3528 * prepared to be burned.
3532 .flags
= CFTYPE_INSANE
, /* use "procs" instead */
3533 .seq_start
= cgroup_pidlist_start
,
3534 .seq_next
= cgroup_pidlist_next
,
3535 .seq_stop
= cgroup_pidlist_stop
,
3536 .seq_show
= cgroup_pidlist_show
,
3537 .private = CGROUP_FILE_TASKS
,
3538 .write_u64
= cgroup_tasks_write
,
3539 .mode
= S_IRUGO
| S_IWUSR
,
3542 .name
= "notify_on_release",
3543 .flags
= CFTYPE_INSANE
,
3544 .read_u64
= cgroup_read_notify_on_release
,
3545 .write_u64
= cgroup_write_notify_on_release
,
3548 .name
= "release_agent",
3549 .flags
= CFTYPE_INSANE
| CFTYPE_ONLY_ON_ROOT
,
3550 .seq_show
= cgroup_release_agent_show
,
3551 .write_string
= cgroup_release_agent_write
,
3552 .max_write_len
= PATH_MAX
- 1,
3558 * cgroup_populate_dir - create subsys files in a cgroup directory
3559 * @cgrp: target cgroup
3560 * @subsys_mask: mask of the subsystem ids whose files should be added
3562 * On failure, no file is added.
3564 static int cgroup_populate_dir(struct cgroup
*cgrp
, unsigned long subsys_mask
)
3566 struct cgroup_subsys
*ss
;
3569 /* process cftsets of each subsystem */
3570 for_each_subsys(ss
, i
) {
3571 struct cftype
*cfts
;
3573 if (!test_bit(i
, &subsys_mask
))
3576 list_for_each_entry(cfts
, &ss
->cfts
, node
) {
3577 ret
= cgroup_addrm_files(cgrp
, cfts
, true);
3584 cgroup_clear_dir(cgrp
, subsys_mask
);
3589 * css destruction is four-stage process.
3591 * 1. Destruction starts. Killing of the percpu_ref is initiated.
3592 * Implemented in kill_css().
3594 * 2. When the percpu_ref is confirmed to be visible as killed on all CPUs
3595 * and thus css_tryget() is guaranteed to fail, the css can be offlined
3596 * by invoking offline_css(). After offlining, the base ref is put.
3597 * Implemented in css_killed_work_fn().
3599 * 3. When the percpu_ref reaches zero, the only possible remaining
3600 * accessors are inside RCU read sections. css_release() schedules the
3603 * 4. After the grace period, the css can be freed. Implemented in
3604 * css_free_work_fn().
3606 * It is actually hairier because both step 2 and 4 require process context
3607 * and thus involve punting to css->destroy_work adding two additional
3608 * steps to the already complex sequence.
3610 static void css_free_work_fn(struct work_struct
*work
)
3612 struct cgroup_subsys_state
*css
=
3613 container_of(work
, struct cgroup_subsys_state
, destroy_work
);
3614 struct cgroup
*cgrp
= css
->cgroup
;
3617 css_put(css
->parent
);
3619 css
->ss
->css_free(css
);
3623 static void css_free_rcu_fn(struct rcu_head
*rcu_head
)
3625 struct cgroup_subsys_state
*css
=
3626 container_of(rcu_head
, struct cgroup_subsys_state
, rcu_head
);
3628 INIT_WORK(&css
->destroy_work
, css_free_work_fn
);
3629 queue_work(cgroup_destroy_wq
, &css
->destroy_work
);
3632 static void css_release(struct percpu_ref
*ref
)
3634 struct cgroup_subsys_state
*css
=
3635 container_of(ref
, struct cgroup_subsys_state
, refcnt
);
3637 RCU_INIT_POINTER(css
->cgroup
->subsys
[css
->ss
->id
], NULL
);
3638 call_rcu(&css
->rcu_head
, css_free_rcu_fn
);
3641 static void init_css(struct cgroup_subsys_state
*css
, struct cgroup_subsys
*ss
,
3642 struct cgroup
*cgrp
)
3649 css
->parent
= cgroup_css(cgrp
->parent
, ss
);
3651 css
->flags
|= CSS_ROOT
;
3653 BUG_ON(cgroup_css(cgrp
, ss
));
3656 /* invoke ->css_online() on a new CSS and mark it online if successful */
3657 static int online_css(struct cgroup_subsys_state
*css
)
3659 struct cgroup_subsys
*ss
= css
->ss
;
3662 lockdep_assert_held(&cgroup_tree_mutex
);
3663 lockdep_assert_held(&cgroup_mutex
);
3666 ret
= ss
->css_online(css
);
3668 css
->flags
|= CSS_ONLINE
;
3669 css
->cgroup
->nr_css
++;
3670 rcu_assign_pointer(css
->cgroup
->subsys
[ss
->id
], css
);
3675 /* if the CSS is online, invoke ->css_offline() on it and mark it offline */
3676 static void offline_css(struct cgroup_subsys_state
*css
)
3678 struct cgroup_subsys
*ss
= css
->ss
;
3680 lockdep_assert_held(&cgroup_tree_mutex
);
3681 lockdep_assert_held(&cgroup_mutex
);
3683 if (!(css
->flags
& CSS_ONLINE
))
3686 if (ss
->css_offline
)
3687 ss
->css_offline(css
);
3689 css
->flags
&= ~CSS_ONLINE
;
3690 css
->cgroup
->nr_css
--;
3691 RCU_INIT_POINTER(css
->cgroup
->subsys
[ss
->id
], css
);
3695 * create_css - create a cgroup_subsys_state
3696 * @cgrp: the cgroup new css will be associated with
3697 * @ss: the subsys of new css
3699 * Create a new css associated with @cgrp - @ss pair. On success, the new
3700 * css is online and installed in @cgrp with all interface files created.
3701 * Returns 0 on success, -errno on failure.
3703 static int create_css(struct cgroup
*cgrp
, struct cgroup_subsys
*ss
)
3705 struct cgroup
*parent
= cgrp
->parent
;
3706 struct cgroup_subsys_state
*css
;
3709 lockdep_assert_held(&cgroup_mutex
);
3711 css
= ss
->css_alloc(cgroup_css(parent
, ss
));
3713 return PTR_ERR(css
);
3715 err
= percpu_ref_init(&css
->refcnt
, css_release
);
3719 init_css(css
, ss
, cgrp
);
3721 err
= cgroup_populate_dir(cgrp
, 1 << ss
->id
);
3723 goto err_free_percpu_ref
;
3725 err
= online_css(css
);
3730 css_get(css
->parent
);
3732 if (ss
->broken_hierarchy
&& !ss
->warned_broken_hierarchy
&&
3734 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",
3735 current
->comm
, current
->pid
, ss
->name
);
3736 if (!strcmp(ss
->name
, "memory"))
3737 pr_warning("cgroup: \"memory\" requires setting use_hierarchy to 1 on the root.\n");
3738 ss
->warned_broken_hierarchy
= true;
3744 cgroup_clear_dir(css
->cgroup
, 1 << css
->ss
->id
);
3745 err_free_percpu_ref
:
3746 percpu_ref_cancel_init(&css
->refcnt
);
3753 * cgroup_create - create a cgroup
3754 * @parent: cgroup that will be parent of the new cgroup
3755 * @name: name of the new cgroup
3756 * @mode: mode to set on new cgroup
3758 static long cgroup_create(struct cgroup
*parent
, const char *name
,
3761 struct cgroup
*cgrp
;
3762 struct cgroup_root
*root
= parent
->root
;
3764 struct cgroup_subsys
*ss
;
3765 struct kernfs_node
*kn
;
3768 * XXX: The default hierarchy isn't fully implemented yet. Block
3769 * !root cgroup creation on it for now.
3771 if (root
== &cgrp_dfl_root
)
3774 /* allocate the cgroup and its ID, 0 is reserved for the root */
3775 cgrp
= kzalloc(sizeof(*cgrp
), GFP_KERNEL
);
3779 mutex_lock(&cgroup_tree_mutex
);
3782 * Only live parents can have children. Note that the liveliness
3783 * check isn't strictly necessary because cgroup_mkdir() and
3784 * cgroup_rmdir() are fully synchronized by i_mutex; however, do it
3785 * anyway so that locking is contained inside cgroup proper and we
3786 * don't get nasty surprises if we ever grow another caller.
3788 if (!cgroup_lock_live_group(parent
)) {
3790 goto err_unlock_tree
;
3794 * Temporarily set the pointer to NULL, so idr_find() won't return
3795 * a half-baked cgroup.
3797 cgrp
->id
= idr_alloc(&root
->cgroup_idr
, NULL
, 1, 0, GFP_KERNEL
);
3803 init_cgroup_housekeeping(cgrp
);
3805 cgrp
->parent
= parent
;
3806 cgrp
->dummy_css
.parent
= &parent
->dummy_css
;
3807 cgrp
->root
= parent
->root
;
3809 if (notify_on_release(parent
))
3810 set_bit(CGRP_NOTIFY_ON_RELEASE
, &cgrp
->flags
);
3812 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN
, &parent
->flags
))
3813 set_bit(CGRP_CPUSET_CLONE_CHILDREN
, &cgrp
->flags
);
3815 /* create the directory */
3816 kn
= kernfs_create_dir(parent
->kn
, name
, mode
, cgrp
);
3824 * This extra ref will be put in cgroup_free_fn() and guarantees
3825 * that @cgrp->kn is always accessible.
3829 cgrp
->serial_nr
= cgroup_serial_nr_next
++;
3831 /* allocation complete, commit to creation */
3832 list_add_tail_rcu(&cgrp
->sibling
, &cgrp
->parent
->children
);
3833 atomic_inc(&root
->nr_cgrps
);
3837 * @cgrp is now fully operational. If something fails after this
3838 * point, it'll be released via the normal destruction path.
3840 idr_replace(&root
->cgroup_idr
, cgrp
, cgrp
->id
);
3842 err
= cgroup_kn_set_ugid(kn
);
3846 err
= cgroup_addrm_files(cgrp
, cgroup_base_files
, true);
3850 /* let's create and online css's */
3851 for_each_subsys(ss
, ssid
) {
3852 if (parent
->child_subsys_mask
& (1 << ssid
)) {
3853 err
= create_css(cgrp
, ss
);
3859 cgrp
->child_subsys_mask
= parent
->child_subsys_mask
;
3861 kernfs_activate(kn
);
3863 mutex_unlock(&cgroup_mutex
);
3864 mutex_unlock(&cgroup_tree_mutex
);
3869 idr_remove(&root
->cgroup_idr
, cgrp
->id
);
3871 mutex_unlock(&cgroup_mutex
);
3873 mutex_unlock(&cgroup_tree_mutex
);
3878 cgroup_destroy_locked(cgrp
);
3879 mutex_unlock(&cgroup_mutex
);
3880 mutex_unlock(&cgroup_tree_mutex
);
3884 static int cgroup_mkdir(struct kernfs_node
*parent_kn
, const char *name
,
3887 struct cgroup
*parent
= parent_kn
->priv
;
3891 * cgroup_create() grabs cgroup_tree_mutex which nests outside
3892 * kernfs active_ref and cgroup_create() already synchronizes
3893 * properly against removal through cgroup_lock_live_group().
3894 * Break it before calling cgroup_create().
3897 kernfs_break_active_protection(parent_kn
);
3899 ret
= cgroup_create(parent
, name
, mode
);
3901 kernfs_unbreak_active_protection(parent_kn
);
3907 * This is called when the refcnt of a css is confirmed to be killed.
3908 * css_tryget() is now guaranteed to fail.
3910 static void css_killed_work_fn(struct work_struct
*work
)
3912 struct cgroup_subsys_state
*css
=
3913 container_of(work
, struct cgroup_subsys_state
, destroy_work
);
3914 struct cgroup
*cgrp
= css
->cgroup
;
3916 mutex_lock(&cgroup_tree_mutex
);
3917 mutex_lock(&cgroup_mutex
);
3920 * css_tryget() is guaranteed to fail now. Tell subsystems to
3921 * initate destruction.
3926 * If @cgrp is marked dead, it's waiting for refs of all css's to
3927 * be disabled before proceeding to the second phase of cgroup
3928 * destruction. If we are the last one, kick it off.
3930 if (!cgrp
->nr_css
&& cgroup_is_dead(cgrp
))
3931 cgroup_destroy_css_killed(cgrp
);
3933 mutex_unlock(&cgroup_mutex
);
3934 mutex_unlock(&cgroup_tree_mutex
);
3937 * Put the css refs from kill_css(). Each css holds an extra
3938 * reference to the cgroup's dentry and cgroup removal proceeds
3939 * regardless of css refs. On the last put of each css, whenever
3940 * that may be, the extra dentry ref is put so that dentry
3941 * destruction happens only after all css's are released.
3946 /* css kill confirmation processing requires process context, bounce */
3947 static void css_killed_ref_fn(struct percpu_ref
*ref
)
3949 struct cgroup_subsys_state
*css
=
3950 container_of(ref
, struct cgroup_subsys_state
, refcnt
);
3952 INIT_WORK(&css
->destroy_work
, css_killed_work_fn
);
3953 queue_work(cgroup_destroy_wq
, &css
->destroy_work
);
3957 * kill_css - destroy a css
3958 * @css: css to destroy
3960 * This function initiates destruction of @css by removing cgroup interface
3961 * files and putting its base reference. ->css_offline() will be invoked
3962 * asynchronously once css_tryget() is guaranteed to fail and when the
3963 * reference count reaches zero, @css will be released.
3965 static void kill_css(struct cgroup_subsys_state
*css
)
3967 lockdep_assert_held(&cgroup_tree_mutex
);
3970 * This must happen before css is disassociated with its cgroup.
3971 * See seq_css() for details.
3973 cgroup_clear_dir(css
->cgroup
, 1 << css
->ss
->id
);
3976 * Killing would put the base ref, but we need to keep it alive
3977 * until after ->css_offline().
3982 * cgroup core guarantees that, by the time ->css_offline() is
3983 * invoked, no new css reference will be given out via
3984 * css_tryget(). We can't simply call percpu_ref_kill() and
3985 * proceed to offlining css's because percpu_ref_kill() doesn't
3986 * guarantee that the ref is seen as killed on all CPUs on return.
3988 * Use percpu_ref_kill_and_confirm() to get notifications as each
3989 * css is confirmed to be seen as killed on all CPUs.
3991 percpu_ref_kill_and_confirm(&css
->refcnt
, css_killed_ref_fn
);
3995 * cgroup_destroy_locked - the first stage of cgroup destruction
3996 * @cgrp: cgroup to be destroyed
3998 * css's make use of percpu refcnts whose killing latency shouldn't be
3999 * exposed to userland and are RCU protected. Also, cgroup core needs to
4000 * guarantee that css_tryget() won't succeed by the time ->css_offline() is
4001 * invoked. To satisfy all the requirements, destruction is implemented in
4002 * the following two steps.
4004 * s1. Verify @cgrp can be destroyed and mark it dying. Remove all
4005 * userland visible parts and start killing the percpu refcnts of
4006 * css's. Set up so that the next stage will be kicked off once all
4007 * the percpu refcnts are confirmed to be killed.
4009 * s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the
4010 * rest of destruction. Once all cgroup references are gone, the
4011 * cgroup is RCU-freed.
4013 * This function implements s1. After this step, @cgrp is gone as far as
4014 * the userland is concerned and a new cgroup with the same name may be
4015 * created. As cgroup doesn't care about the names internally, this
4016 * doesn't cause any problem.
4018 static int cgroup_destroy_locked(struct cgroup
*cgrp
)
4019 __releases(&cgroup_mutex
) __acquires(&cgroup_mutex
)
4021 struct cgroup
*child
;
4022 struct cgroup_subsys_state
*css
;
4026 lockdep_assert_held(&cgroup_tree_mutex
);
4027 lockdep_assert_held(&cgroup_mutex
);
4030 * css_set_rwsem synchronizes access to ->cset_links and prevents
4031 * @cgrp from being removed while put_css_set() is in progress.
4033 down_read(&css_set_rwsem
);
4034 empty
= list_empty(&cgrp
->cset_links
);
4035 up_read(&css_set_rwsem
);
4040 * Make sure there's no live children. We can't test ->children
4041 * emptiness as dead children linger on it while being destroyed;
4042 * otherwise, "rmdir parent/child parent" may fail with -EBUSY.
4046 list_for_each_entry_rcu(child
, &cgrp
->children
, sibling
) {
4047 empty
= cgroup_is_dead(child
);
4056 * Mark @cgrp dead. This prevents further task migration and child
4057 * creation by disabling cgroup_lock_live_group(). Note that
4058 * CGRP_DEAD assertion is depended upon by css_next_child() to
4059 * resume iteration after dropping RCU read lock. See
4060 * css_next_child() for details.
4062 set_bit(CGRP_DEAD
, &cgrp
->flags
);
4065 * Initiate massacre of all css's. cgroup_destroy_css_killed()
4066 * will be invoked to perform the rest of destruction once the
4067 * percpu refs of all css's are confirmed to be killed. This
4068 * involves removing the subsystem's files, drop cgroup_mutex.
4070 mutex_unlock(&cgroup_mutex
);
4071 for_each_css(css
, ssid
, cgrp
)
4073 mutex_lock(&cgroup_mutex
);
4075 /* CGRP_DEAD is set, remove from ->release_list for the last time */
4076 raw_spin_lock(&release_list_lock
);
4077 if (!list_empty(&cgrp
->release_list
))
4078 list_del_init(&cgrp
->release_list
);
4079 raw_spin_unlock(&release_list_lock
);
4082 * If @cgrp has css's attached, the second stage of cgroup
4083 * destruction is kicked off from css_killed_work_fn() after the
4084 * refs of all attached css's are killed. If @cgrp doesn't have
4085 * any css, we kick it off here.
4088 cgroup_destroy_css_killed(cgrp
);
4090 /* remove @cgrp directory along with the base files */
4091 mutex_unlock(&cgroup_mutex
);
4094 * There are two control paths which try to determine cgroup from
4095 * dentry without going through kernfs - cgroupstats_build() and
4096 * css_tryget_from_dir(). Those are supported by RCU protecting
4097 * clearing of cgrp->kn->priv backpointer, which should happen
4098 * after all files under it have been removed.
4100 kernfs_remove(cgrp
->kn
); /* @cgrp has an extra ref on its kn */
4101 RCU_INIT_POINTER(*(void __rcu __force
**)&cgrp
->kn
->priv
, NULL
);
4103 mutex_lock(&cgroup_mutex
);
4109 * cgroup_destroy_css_killed - the second step of cgroup destruction
4110 * @work: cgroup->destroy_free_work
4112 * This function is invoked from a work item for a cgroup which is being
4113 * destroyed after all css's are offlined and performs the rest of
4114 * destruction. This is the second step of destruction described in the
4115 * comment above cgroup_destroy_locked().
4117 static void cgroup_destroy_css_killed(struct cgroup
*cgrp
)
4119 struct cgroup
*parent
= cgrp
->parent
;
4121 lockdep_assert_held(&cgroup_tree_mutex
);
4122 lockdep_assert_held(&cgroup_mutex
);
4124 /* delete this cgroup from parent->children */
4125 list_del_rcu(&cgrp
->sibling
);
4129 set_bit(CGRP_RELEASABLE
, &parent
->flags
);
4130 check_for_release(parent
);
4133 static int cgroup_rmdir(struct kernfs_node
*kn
)
4135 struct cgroup
*cgrp
= kn
->priv
;
4139 * This is self-destruction but @kn can't be removed while this
4140 * callback is in progress. Let's break active protection. Once
4141 * the protection is broken, @cgrp can be destroyed at any point.
4142 * Pin it so that it stays accessible.
4145 kernfs_break_active_protection(kn
);
4147 mutex_lock(&cgroup_tree_mutex
);
4148 mutex_lock(&cgroup_mutex
);
4151 * @cgrp might already have been destroyed while we're trying to
4154 if (!cgroup_is_dead(cgrp
))
4155 ret
= cgroup_destroy_locked(cgrp
);
4157 mutex_unlock(&cgroup_mutex
);
4158 mutex_unlock(&cgroup_tree_mutex
);
4160 kernfs_unbreak_active_protection(kn
);
4165 static struct kernfs_syscall_ops cgroup_kf_syscall_ops
= {
4166 .remount_fs
= cgroup_remount
,
4167 .show_options
= cgroup_show_options
,
4168 .mkdir
= cgroup_mkdir
,
4169 .rmdir
= cgroup_rmdir
,
4170 .rename
= cgroup_rename
,
4173 static void __init
cgroup_init_subsys(struct cgroup_subsys
*ss
)
4175 struct cgroup_subsys_state
*css
;
4177 printk(KERN_INFO
"Initializing cgroup subsys %s\n", ss
->name
);
4179 mutex_lock(&cgroup_tree_mutex
);
4180 mutex_lock(&cgroup_mutex
);
4182 INIT_LIST_HEAD(&ss
->cfts
);
4184 /* Create the root cgroup state for this subsystem */
4185 ss
->root
= &cgrp_dfl_root
;
4186 css
= ss
->css_alloc(cgroup_css(&cgrp_dfl_root
.cgrp
, ss
));
4187 /* We don't handle early failures gracefully */
4188 BUG_ON(IS_ERR(css
));
4189 init_css(css
, ss
, &cgrp_dfl_root
.cgrp
);
4191 /* Update the init_css_set to contain a subsys
4192 * pointer to this state - since the subsystem is
4193 * newly registered, all tasks and hence the
4194 * init_css_set is in the subsystem's root cgroup. */
4195 init_css_set
.subsys
[ss
->id
] = css
;
4197 need_forkexit_callback
|= ss
->fork
|| ss
->exit
;
4199 /* At system boot, before all subsystems have been
4200 * registered, no tasks have been forked, so we don't
4201 * need to invoke fork callbacks here. */
4202 BUG_ON(!list_empty(&init_task
.tasks
));
4204 BUG_ON(online_css(css
));
4206 cgrp_dfl_root
.subsys_mask
|= 1 << ss
->id
;
4208 mutex_unlock(&cgroup_mutex
);
4209 mutex_unlock(&cgroup_tree_mutex
);
4213 * cgroup_init_early - cgroup initialization at system boot
4215 * Initialize cgroups at system boot, and initialize any
4216 * subsystems that request early init.
4218 int __init
cgroup_init_early(void)
4220 static struct cgroup_sb_opts __initdata opts
=
4221 { .flags
= CGRP_ROOT_SANE_BEHAVIOR
};
4222 struct cgroup_subsys
*ss
;
4225 init_cgroup_root(&cgrp_dfl_root
, &opts
);
4226 RCU_INIT_POINTER(init_task
.cgroups
, &init_css_set
);
4228 for_each_subsys(ss
, i
) {
4229 WARN(!ss
->css_alloc
|| !ss
->css_free
|| ss
->name
|| ss
->id
,
4230 "invalid cgroup_subsys %d:%s css_alloc=%p css_free=%p name:id=%d:%s\n",
4231 i
, cgroup_subsys_name
[i
], ss
->css_alloc
, ss
->css_free
,
4233 WARN(strlen(cgroup_subsys_name
[i
]) > MAX_CGROUP_TYPE_NAMELEN
,
4234 "cgroup_subsys_name %s too long\n", cgroup_subsys_name
[i
]);
4237 ss
->name
= cgroup_subsys_name
[i
];
4240 cgroup_init_subsys(ss
);
4246 * cgroup_init - cgroup initialization
4248 * Register cgroup filesystem and /proc file, and initialize
4249 * any subsystems that didn't request early init.
4251 int __init
cgroup_init(void)
4253 struct cgroup_subsys
*ss
;
4257 BUG_ON(cgroup_init_cftypes(NULL
, cgroup_base_files
));
4259 mutex_lock(&cgroup_tree_mutex
);
4260 mutex_lock(&cgroup_mutex
);
4262 /* Add init_css_set to the hash table */
4263 key
= css_set_hash(init_css_set
.subsys
);
4264 hash_add(css_set_table
, &init_css_set
.hlist
, key
);
4266 BUG_ON(cgroup_setup_root(&cgrp_dfl_root
, 0));
4268 mutex_unlock(&cgroup_mutex
);
4269 mutex_unlock(&cgroup_tree_mutex
);
4271 for_each_subsys(ss
, ssid
) {
4272 if (!ss
->early_init
)
4273 cgroup_init_subsys(ss
);
4275 list_add_tail(&init_css_set
.e_cset_node
[ssid
],
4276 &cgrp_dfl_root
.cgrp
.e_csets
[ssid
]);
4279 * cftype registration needs kmalloc and can't be done
4280 * during early_init. Register base cftypes separately.
4282 if (ss
->base_cftypes
)
4283 WARN_ON(cgroup_add_cftypes(ss
, ss
->base_cftypes
));
4286 cgroup_kobj
= kobject_create_and_add("cgroup", fs_kobj
);
4290 err
= register_filesystem(&cgroup_fs_type
);
4292 kobject_put(cgroup_kobj
);
4296 proc_create("cgroups", 0, NULL
, &proc_cgroupstats_operations
);
4300 static int __init
cgroup_wq_init(void)
4303 * There isn't much point in executing destruction path in
4304 * parallel. Good chunk is serialized with cgroup_mutex anyway.
4305 * Use 1 for @max_active.
4307 * We would prefer to do this in cgroup_init() above, but that
4308 * is called before init_workqueues(): so leave this until after.
4310 cgroup_destroy_wq
= alloc_workqueue("cgroup_destroy", 0, 1);
4311 BUG_ON(!cgroup_destroy_wq
);
4314 * Used to destroy pidlists and separate to serve as flush domain.
4315 * Cap @max_active to 1 too.
4317 cgroup_pidlist_destroy_wq
= alloc_workqueue("cgroup_pidlist_destroy",
4319 BUG_ON(!cgroup_pidlist_destroy_wq
);
4323 core_initcall(cgroup_wq_init
);
4326 * proc_cgroup_show()
4327 * - Print task's cgroup paths into seq_file, one line for each hierarchy
4328 * - Used for /proc/<pid>/cgroup.
4331 /* TODO: Use a proper seq_file iterator */
4332 int proc_cgroup_show(struct seq_file
*m
, void *v
)
4335 struct task_struct
*tsk
;
4338 struct cgroup_root
*root
;
4341 buf
= kmalloc(PATH_MAX
, GFP_KERNEL
);
4347 tsk
= get_pid_task(pid
, PIDTYPE_PID
);
4353 mutex_lock(&cgroup_mutex
);
4354 down_read(&css_set_rwsem
);
4356 for_each_root(root
) {
4357 struct cgroup_subsys
*ss
;
4358 struct cgroup
*cgrp
;
4359 int ssid
, count
= 0;
4361 if (root
== &cgrp_dfl_root
&& !cgrp_dfl_root_visible
)
4364 seq_printf(m
, "%d:", root
->hierarchy_id
);
4365 for_each_subsys(ss
, ssid
)
4366 if (root
->subsys_mask
& (1 << ssid
))
4367 seq_printf(m
, "%s%s", count
++ ? "," : "", ss
->name
);
4368 if (strlen(root
->name
))
4369 seq_printf(m
, "%sname=%s", count
? "," : "",
4372 cgrp
= task_cgroup_from_root(tsk
, root
);
4373 path
= cgroup_path(cgrp
, buf
, PATH_MAX
);
4375 retval
= -ENAMETOOLONG
;
4383 up_read(&css_set_rwsem
);
4384 mutex_unlock(&cgroup_mutex
);
4385 put_task_struct(tsk
);
4392 /* Display information about each subsystem and each hierarchy */
4393 static int proc_cgroupstats_show(struct seq_file
*m
, void *v
)
4395 struct cgroup_subsys
*ss
;
4398 seq_puts(m
, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
4400 * ideally we don't want subsystems moving around while we do this.
4401 * cgroup_mutex is also necessary to guarantee an atomic snapshot of
4402 * subsys/hierarchy state.
4404 mutex_lock(&cgroup_mutex
);
4406 for_each_subsys(ss
, i
)
4407 seq_printf(m
, "%s\t%d\t%d\t%d\n",
4408 ss
->name
, ss
->root
->hierarchy_id
,
4409 atomic_read(&ss
->root
->nr_cgrps
), !ss
->disabled
);
4411 mutex_unlock(&cgroup_mutex
);
4415 static int cgroupstats_open(struct inode
*inode
, struct file
*file
)
4417 return single_open(file
, proc_cgroupstats_show
, NULL
);
4420 static const struct file_operations proc_cgroupstats_operations
= {
4421 .open
= cgroupstats_open
,
4423 .llseek
= seq_lseek
,
4424 .release
= single_release
,
4428 * cgroup_fork - initialize cgroup related fields during copy_process()
4429 * @child: pointer to task_struct of forking parent process.
4431 * A task is associated with the init_css_set until cgroup_post_fork()
4432 * attaches it to the parent's css_set. Empty cg_list indicates that
4433 * @child isn't holding reference to its css_set.
4435 void cgroup_fork(struct task_struct
*child
)
4437 RCU_INIT_POINTER(child
->cgroups
, &init_css_set
);
4438 INIT_LIST_HEAD(&child
->cg_list
);
4442 * cgroup_post_fork - called on a new task after adding it to the task list
4443 * @child: the task in question
4445 * Adds the task to the list running through its css_set if necessary and
4446 * call the subsystem fork() callbacks. Has to be after the task is
4447 * visible on the task list in case we race with the first call to
4448 * cgroup_task_iter_start() - to guarantee that the new task ends up on its
4451 void cgroup_post_fork(struct task_struct
*child
)
4453 struct cgroup_subsys
*ss
;
4457 * This may race against cgroup_enable_task_cg_links(). As that
4458 * function sets use_task_css_set_links before grabbing
4459 * tasklist_lock and we just went through tasklist_lock to add
4460 * @child, it's guaranteed that either we see the set
4461 * use_task_css_set_links or cgroup_enable_task_cg_lists() sees
4462 * @child during its iteration.
4464 * If we won the race, @child is associated with %current's
4465 * css_set. Grabbing css_set_rwsem guarantees both that the
4466 * association is stable, and, on completion of the parent's
4467 * migration, @child is visible in the source of migration or
4468 * already in the destination cgroup. This guarantee is necessary
4469 * when implementing operations which need to migrate all tasks of
4470 * a cgroup to another.
4472 * Note that if we lose to cgroup_enable_task_cg_links(), @child
4473 * will remain in init_css_set. This is safe because all tasks are
4474 * in the init_css_set before cg_links is enabled and there's no
4475 * operation which transfers all tasks out of init_css_set.
4477 if (use_task_css_set_links
) {
4478 struct css_set
*cset
;
4480 down_write(&css_set_rwsem
);
4481 cset
= task_css_set(current
);
4482 if (list_empty(&child
->cg_list
)) {
4483 rcu_assign_pointer(child
->cgroups
, cset
);
4484 list_add(&child
->cg_list
, &cset
->tasks
);
4487 up_write(&css_set_rwsem
);
4491 * Call ss->fork(). This must happen after @child is linked on
4492 * css_set; otherwise, @child might change state between ->fork()
4493 * and addition to css_set.
4495 if (need_forkexit_callback
) {
4496 for_each_subsys(ss
, i
)
4503 * cgroup_exit - detach cgroup from exiting task
4504 * @tsk: pointer to task_struct of exiting process
4506 * Description: Detach cgroup from @tsk and release it.
4508 * Note that cgroups marked notify_on_release force every task in
4509 * them to take the global cgroup_mutex mutex when exiting.
4510 * This could impact scaling on very large systems. Be reluctant to
4511 * use notify_on_release cgroups where very high task exit scaling
4512 * is required on large systems.
4514 * We set the exiting tasks cgroup to the root cgroup (top_cgroup). We
4515 * call cgroup_exit() while the task is still competent to handle
4516 * notify_on_release(), then leave the task attached to the root cgroup in
4517 * each hierarchy for the remainder of its exit. No need to bother with
4518 * init_css_set refcnting. init_css_set never goes away and we can't race
4519 * with migration path - PF_EXITING is visible to migration path.
4521 void cgroup_exit(struct task_struct
*tsk
)
4523 struct cgroup_subsys
*ss
;
4524 struct css_set
*cset
;
4525 bool put_cset
= false;
4529 * Unlink from @tsk from its css_set. As migration path can't race
4530 * with us, we can check cg_list without grabbing css_set_rwsem.
4532 if (!list_empty(&tsk
->cg_list
)) {
4533 down_write(&css_set_rwsem
);
4534 list_del_init(&tsk
->cg_list
);
4535 up_write(&css_set_rwsem
);
4539 /* Reassign the task to the init_css_set. */
4540 cset
= task_css_set(tsk
);
4541 RCU_INIT_POINTER(tsk
->cgroups
, &init_css_set
);
4543 if (need_forkexit_callback
) {
4544 /* see cgroup_post_fork() for details */
4545 for_each_subsys(ss
, i
) {
4547 struct cgroup_subsys_state
*old_css
= cset
->subsys
[i
];
4548 struct cgroup_subsys_state
*css
= task_css(tsk
, i
);
4550 ss
->exit(css
, old_css
, tsk
);
4556 put_css_set(cset
, true);
4559 static void check_for_release(struct cgroup
*cgrp
)
4561 if (cgroup_is_releasable(cgrp
) &&
4562 list_empty(&cgrp
->cset_links
) && list_empty(&cgrp
->children
)) {
4564 * Control Group is currently removeable. If it's not
4565 * already queued for a userspace notification, queue
4568 int need_schedule_work
= 0;
4570 raw_spin_lock(&release_list_lock
);
4571 if (!cgroup_is_dead(cgrp
) &&
4572 list_empty(&cgrp
->release_list
)) {
4573 list_add(&cgrp
->release_list
, &release_list
);
4574 need_schedule_work
= 1;
4576 raw_spin_unlock(&release_list_lock
);
4577 if (need_schedule_work
)
4578 schedule_work(&release_agent_work
);
4583 * Notify userspace when a cgroup is released, by running the
4584 * configured release agent with the name of the cgroup (path
4585 * relative to the root of cgroup file system) as the argument.
4587 * Most likely, this user command will try to rmdir this cgroup.
4589 * This races with the possibility that some other task will be
4590 * attached to this cgroup before it is removed, or that some other
4591 * user task will 'mkdir' a child cgroup of this cgroup. That's ok.
4592 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
4593 * unused, and this cgroup will be reprieved from its death sentence,
4594 * to continue to serve a useful existence. Next time it's released,
4595 * we will get notified again, if it still has 'notify_on_release' set.
4597 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
4598 * means only wait until the task is successfully execve()'d. The
4599 * separate release agent task is forked by call_usermodehelper(),
4600 * then control in this thread returns here, without waiting for the
4601 * release agent task. We don't bother to wait because the caller of
4602 * this routine has no use for the exit status of the release agent
4603 * task, so no sense holding our caller up for that.
4605 static void cgroup_release_agent(struct work_struct
*work
)
4607 BUG_ON(work
!= &release_agent_work
);
4608 mutex_lock(&cgroup_mutex
);
4609 raw_spin_lock(&release_list_lock
);
4610 while (!list_empty(&release_list
)) {
4611 char *argv
[3], *envp
[3];
4613 char *pathbuf
= NULL
, *agentbuf
= NULL
, *path
;
4614 struct cgroup
*cgrp
= list_entry(release_list
.next
,
4617 list_del_init(&cgrp
->release_list
);
4618 raw_spin_unlock(&release_list_lock
);
4619 pathbuf
= kmalloc(PATH_MAX
, GFP_KERNEL
);
4622 path
= cgroup_path(cgrp
, pathbuf
, PATH_MAX
);
4625 agentbuf
= kstrdup(cgrp
->root
->release_agent_path
, GFP_KERNEL
);
4630 argv
[i
++] = agentbuf
;
4635 /* minimal command environment */
4636 envp
[i
++] = "HOME=/";
4637 envp
[i
++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
4640 /* Drop the lock while we invoke the usermode helper,
4641 * since the exec could involve hitting disk and hence
4642 * be a slow process */
4643 mutex_unlock(&cgroup_mutex
);
4644 call_usermodehelper(argv
[0], argv
, envp
, UMH_WAIT_EXEC
);
4645 mutex_lock(&cgroup_mutex
);
4649 raw_spin_lock(&release_list_lock
);
4651 raw_spin_unlock(&release_list_lock
);
4652 mutex_unlock(&cgroup_mutex
);
4655 static int __init
cgroup_disable(char *str
)
4657 struct cgroup_subsys
*ss
;
4661 while ((token
= strsep(&str
, ",")) != NULL
) {
4665 for_each_subsys(ss
, i
) {
4666 if (!strcmp(token
, ss
->name
)) {
4668 printk(KERN_INFO
"Disabling %s control group"
4669 " subsystem\n", ss
->name
);
4676 __setup("cgroup_disable=", cgroup_disable
);
4679 * css_tryget_from_dir - get corresponding css from the dentry of a cgroup dir
4680 * @dentry: directory dentry of interest
4681 * @ss: subsystem of interest
4683 * If @dentry is a directory for a cgroup which has @ss enabled on it, try
4684 * to get the corresponding css and return it. If such css doesn't exist
4685 * or can't be pinned, an ERR_PTR value is returned.
4687 struct cgroup_subsys_state
*css_tryget_from_dir(struct dentry
*dentry
,
4688 struct cgroup_subsys
*ss
)
4690 struct kernfs_node
*kn
= kernfs_node_from_dentry(dentry
);
4691 struct cgroup_subsys_state
*css
= NULL
;
4692 struct cgroup
*cgrp
;
4694 /* is @dentry a cgroup dir? */
4695 if (dentry
->d_sb
->s_type
!= &cgroup_fs_type
|| !kn
||
4696 kernfs_type(kn
) != KERNFS_DIR
)
4697 return ERR_PTR(-EBADF
);
4702 * This path doesn't originate from kernfs and @kn could already
4703 * have been or be removed at any point. @kn->priv is RCU
4704 * protected for this access. See destroy_locked() for details.
4706 cgrp
= rcu_dereference(kn
->priv
);
4708 css
= cgroup_css(cgrp
, ss
);
4710 if (!css
|| !css_tryget(css
))
4711 css
= ERR_PTR(-ENOENT
);
4718 * css_from_id - lookup css by id
4719 * @id: the cgroup id
4720 * @ss: cgroup subsys to be looked into
4722 * Returns the css if there's valid one with @id, otherwise returns NULL.
4723 * Should be called under rcu_read_lock().
4725 struct cgroup_subsys_state
*css_from_id(int id
, struct cgroup_subsys
*ss
)
4727 struct cgroup
*cgrp
;
4729 cgroup_assert_mutexes_or_rcu_locked();
4731 cgrp
= idr_find(&ss
->root
->cgroup_idr
, id
);
4733 return cgroup_css(cgrp
, ss
);
4737 #ifdef CONFIG_CGROUP_DEBUG
4738 static struct cgroup_subsys_state
*
4739 debug_css_alloc(struct cgroup_subsys_state
*parent_css
)
4741 struct cgroup_subsys_state
*css
= kzalloc(sizeof(*css
), GFP_KERNEL
);
4744 return ERR_PTR(-ENOMEM
);
4749 static void debug_css_free(struct cgroup_subsys_state
*css
)
4754 static u64
debug_taskcount_read(struct cgroup_subsys_state
*css
,
4757 return cgroup_task_count(css
->cgroup
);
4760 static u64
current_css_set_read(struct cgroup_subsys_state
*css
,
4763 return (u64
)(unsigned long)current
->cgroups
;
4766 static u64
current_css_set_refcount_read(struct cgroup_subsys_state
*css
,
4772 count
= atomic_read(&task_css_set(current
)->refcount
);
4777 static int current_css_set_cg_links_read(struct seq_file
*seq
, void *v
)
4779 struct cgrp_cset_link
*link
;
4780 struct css_set
*cset
;
4783 name_buf
= kmalloc(NAME_MAX
+ 1, GFP_KERNEL
);
4787 down_read(&css_set_rwsem
);
4789 cset
= rcu_dereference(current
->cgroups
);
4790 list_for_each_entry(link
, &cset
->cgrp_links
, cgrp_link
) {
4791 struct cgroup
*c
= link
->cgrp
;
4793 cgroup_name(c
, name_buf
, NAME_MAX
+ 1);
4794 seq_printf(seq
, "Root %d group %s\n",
4795 c
->root
->hierarchy_id
, name_buf
);
4798 up_read(&css_set_rwsem
);
4803 #define MAX_TASKS_SHOWN_PER_CSS 25
4804 static int cgroup_css_links_read(struct seq_file
*seq
, void *v
)
4806 struct cgroup_subsys_state
*css
= seq_css(seq
);
4807 struct cgrp_cset_link
*link
;
4809 down_read(&css_set_rwsem
);
4810 list_for_each_entry(link
, &css
->cgroup
->cset_links
, cset_link
) {
4811 struct css_set
*cset
= link
->cset
;
4812 struct task_struct
*task
;
4815 seq_printf(seq
, "css_set %p\n", cset
);
4817 list_for_each_entry(task
, &cset
->tasks
, cg_list
) {
4818 if (count
++ > MAX_TASKS_SHOWN_PER_CSS
)
4820 seq_printf(seq
, " task %d\n", task_pid_vnr(task
));
4823 list_for_each_entry(task
, &cset
->mg_tasks
, cg_list
) {
4824 if (count
++ > MAX_TASKS_SHOWN_PER_CSS
)
4826 seq_printf(seq
, " task %d\n", task_pid_vnr(task
));
4830 seq_puts(seq
, " ...\n");
4832 up_read(&css_set_rwsem
);
4836 static u64
releasable_read(struct cgroup_subsys_state
*css
, struct cftype
*cft
)
4838 return test_bit(CGRP_RELEASABLE
, &css
->cgroup
->flags
);
4841 static struct cftype debug_files
[] = {
4843 .name
= "taskcount",
4844 .read_u64
= debug_taskcount_read
,
4848 .name
= "current_css_set",
4849 .read_u64
= current_css_set_read
,
4853 .name
= "current_css_set_refcount",
4854 .read_u64
= current_css_set_refcount_read
,
4858 .name
= "current_css_set_cg_links",
4859 .seq_show
= current_css_set_cg_links_read
,
4863 .name
= "cgroup_css_links",
4864 .seq_show
= cgroup_css_links_read
,
4868 .name
= "releasable",
4869 .read_u64
= releasable_read
,
4875 struct cgroup_subsys debug_cgrp_subsys
= {
4876 .css_alloc
= debug_css_alloc
,
4877 .css_free
= debug_css_free
,
4878 .base_cftypes
= debug_files
,
4880 #endif /* CONFIG_CGROUP_DEBUG */