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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
31 #include <linux/cgroup.h>
32 #include <linux/cred.h>
33 #include <linux/ctype.h>
34 #include <linux/errno.h>
35 #include <linux/init_task.h>
36 #include <linux/kernel.h>
37 #include <linux/list.h>
38 #include <linux/magic.h>
40 #include <linux/mutex.h>
41 #include <linux/mount.h>
42 #include <linux/pagemap.h>
43 #include <linux/proc_fs.h>
44 #include <linux/rcupdate.h>
45 #include <linux/sched.h>
46 #include <linux/slab.h>
47 #include <linux/spinlock.h>
48 #include <linux/rwsem.h>
49 #include <linux/string.h>
50 #include <linux/sort.h>
51 #include <linux/kmod.h>
52 #include <linux/delayacct.h>
53 #include <linux/cgroupstats.h>
54 #include <linux/hashtable.h>
55 #include <linux/pid_namespace.h>
56 #include <linux/idr.h>
57 #include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
58 #include <linux/kthread.h>
59 #include <linux/delay.h>
61 #include <linux/atomic.h>
64 * pidlists linger the following amount before being destroyed. The goal
65 * is avoiding frequent destruction in the middle of consecutive read calls
66 * Expiring in the middle is a performance problem not a correctness one.
67 * 1 sec should be enough.
69 #define CGROUP_PIDLIST_DESTROY_DELAY HZ
71 #define CGROUP_FILE_NAME_MAX (MAX_CGROUP_TYPE_NAMELEN + \
75 * cgroup_mutex is the master lock. Any modification to cgroup or its
76 * hierarchy must be performed while holding it.
78 * css_set_rwsem protects task->cgroups pointer, the list of css_set
79 * objects, and the chain of tasks off each css_set.
81 * These locks are exported if CONFIG_PROVE_RCU so that accessors in
82 * cgroup.h can use them for lockdep annotations.
84 #ifdef CONFIG_PROVE_RCU
85 DEFINE_MUTEX(cgroup_mutex
);
86 DECLARE_RWSEM(css_set_rwsem
);
87 EXPORT_SYMBOL_GPL(cgroup_mutex
);
88 EXPORT_SYMBOL_GPL(css_set_rwsem
);
90 static DEFINE_MUTEX(cgroup_mutex
);
91 static DECLARE_RWSEM(css_set_rwsem
);
95 * Protects cgroup_idr and css_idr so that IDs can be released without
96 * grabbing cgroup_mutex.
98 static DEFINE_SPINLOCK(cgroup_idr_lock
);
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_mutex_or_rcu_locked() \
107 rcu_lockdep_assert(rcu_read_lock_held() || \
108 lockdep_is_held(&cgroup_mutex), \
109 "cgroup_mutex or RCU read lock required");
112 * cgroup destruction makes heavy use of work items and there can be a lot
113 * of concurrent destructions. Use a separate workqueue so that cgroup
114 * destruction work items don't end up filling up max_active of system_wq
115 * which may lead to deadlock.
117 static struct workqueue_struct
*cgroup_destroy_wq
;
120 * pidlist destructions need to be flushed on cgroup destruction. Use a
121 * separate workqueue as flush domain.
123 static struct workqueue_struct
*cgroup_pidlist_destroy_wq
;
125 /* generate an array of cgroup subsystem pointers */
126 #define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys,
127 static struct cgroup_subsys
*cgroup_subsys
[] = {
128 #include <linux/cgroup_subsys.h>
132 /* array of cgroup subsystem names */
133 #define SUBSYS(_x) [_x ## _cgrp_id] = #_x,
134 static const char *cgroup_subsys_name
[] = {
135 #include <linux/cgroup_subsys.h>
140 * The default hierarchy, reserved for the subsystems that are otherwise
141 * unattached - it never has more than a single cgroup, and all tasks are
142 * part of that cgroup.
144 struct cgroup_root cgrp_dfl_root
;
147 * The default hierarchy always exists but is hidden until mounted for the
148 * first time. This is for backward compatibility.
150 static bool cgrp_dfl_root_visible
;
153 * Set by the boot param of the same name and makes subsystems with NULL
154 * ->dfl_files to use ->legacy_files on the default hierarchy.
156 static bool cgroup_legacy_files_on_dfl
;
158 /* some controllers are not supported in the default hierarchy */
159 static unsigned int cgrp_dfl_root_inhibit_ss_mask
;
161 /* The list of hierarchy roots */
163 static LIST_HEAD(cgroup_roots
);
164 static int cgroup_root_count
;
166 /* hierarchy ID allocation and mapping, protected by cgroup_mutex */
167 static DEFINE_IDR(cgroup_hierarchy_idr
);
170 * Assign a monotonically increasing serial number to csses. It guarantees
171 * cgroups with bigger numbers are newer than those with smaller numbers.
172 * Also, as csses are always appended to the parent's ->children list, it
173 * guarantees that sibling csses are always sorted in the ascending serial
174 * number order on the list. Protected by cgroup_mutex.
176 static u64 css_serial_nr_next
= 1;
178 /* This flag indicates whether tasks in the fork and exit paths should
179 * check for fork/exit handlers to call. This avoids us having to do
180 * extra work in the fork/exit path if none of the subsystems need to
183 static int need_forkexit_callback __read_mostly
;
185 static struct cftype cgroup_dfl_base_files
[];
186 static struct cftype cgroup_legacy_base_files
[];
188 static void cgroup_put(struct cgroup
*cgrp
);
189 static int rebind_subsystems(struct cgroup_root
*dst_root
,
190 unsigned int ss_mask
);
191 static int cgroup_destroy_locked(struct cgroup
*cgrp
);
192 static int create_css(struct cgroup
*cgrp
, struct cgroup_subsys
*ss
,
194 static void css_release(struct percpu_ref
*ref
);
195 static void kill_css(struct cgroup_subsys_state
*css
);
196 static int cgroup_addrm_files(struct cgroup
*cgrp
, struct cftype cfts
[],
198 static void cgroup_pidlist_destroy_all(struct cgroup
*cgrp
);
200 /* IDR wrappers which synchronize using cgroup_idr_lock */
201 static int cgroup_idr_alloc(struct idr
*idr
, void *ptr
, int start
, int end
,
206 idr_preload(gfp_mask
);
207 spin_lock_bh(&cgroup_idr_lock
);
208 ret
= idr_alloc(idr
, ptr
, start
, end
, gfp_mask
);
209 spin_unlock_bh(&cgroup_idr_lock
);
214 static void *cgroup_idr_replace(struct idr
*idr
, void *ptr
, int id
)
218 spin_lock_bh(&cgroup_idr_lock
);
219 ret
= idr_replace(idr
, ptr
, id
);
220 spin_unlock_bh(&cgroup_idr_lock
);
224 static void cgroup_idr_remove(struct idr
*idr
, int id
)
226 spin_lock_bh(&cgroup_idr_lock
);
228 spin_unlock_bh(&cgroup_idr_lock
);
231 static struct cgroup
*cgroup_parent(struct cgroup
*cgrp
)
233 struct cgroup_subsys_state
*parent_css
= cgrp
->self
.parent
;
236 return container_of(parent_css
, struct cgroup
, self
);
241 * cgroup_css - obtain a cgroup's css for the specified subsystem
242 * @cgrp: the cgroup of interest
243 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
245 * Return @cgrp's css (cgroup_subsys_state) associated with @ss. This
246 * function must be called either under cgroup_mutex or rcu_read_lock() and
247 * the caller is responsible for pinning the returned css if it wants to
248 * keep accessing it outside the said locks. This function may return
249 * %NULL if @cgrp doesn't have @subsys_id enabled.
251 static struct cgroup_subsys_state
*cgroup_css(struct cgroup
*cgrp
,
252 struct cgroup_subsys
*ss
)
255 return rcu_dereference_check(cgrp
->subsys
[ss
->id
],
256 lockdep_is_held(&cgroup_mutex
));
262 * cgroup_e_css - obtain a cgroup's effective css for the specified subsystem
263 * @cgrp: the cgroup of interest
264 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
266 * Similar to cgroup_css() but returns the effctive css, which is defined
267 * as the matching css of the nearest ancestor including self which has @ss
268 * enabled. If @ss is associated with the hierarchy @cgrp is on, this
269 * function is guaranteed to return non-NULL css.
271 static struct cgroup_subsys_state
*cgroup_e_css(struct cgroup
*cgrp
,
272 struct cgroup_subsys
*ss
)
274 lockdep_assert_held(&cgroup_mutex
);
279 if (!(cgrp
->root
->subsys_mask
& (1 << ss
->id
)))
282 while (cgroup_parent(cgrp
) &&
283 !(cgroup_parent(cgrp
)->child_subsys_mask
& (1 << ss
->id
)))
284 cgrp
= cgroup_parent(cgrp
);
286 return cgroup_css(cgrp
, ss
);
289 /* convenient tests for these bits */
290 static inline bool cgroup_is_dead(const struct cgroup
*cgrp
)
292 return !(cgrp
->self
.flags
& CSS_ONLINE
);
295 struct cgroup_subsys_state
*of_css(struct kernfs_open_file
*of
)
297 struct cgroup
*cgrp
= of
->kn
->parent
->priv
;
298 struct cftype
*cft
= of_cft(of
);
301 * This is open and unprotected implementation of cgroup_css().
302 * seq_css() is only called from a kernfs file operation which has
303 * an active reference on the file. Because all the subsystem
304 * files are drained before a css is disassociated with a cgroup,
305 * the matching css from the cgroup's subsys table is guaranteed to
306 * be and stay valid until the enclosing operation is complete.
309 return rcu_dereference_raw(cgrp
->subsys
[cft
->ss
->id
]);
313 EXPORT_SYMBOL_GPL(of_css
);
316 * cgroup_is_descendant - test ancestry
317 * @cgrp: the cgroup to be tested
318 * @ancestor: possible ancestor of @cgrp
320 * Test whether @cgrp is a descendant of @ancestor. It also returns %true
321 * if @cgrp == @ancestor. This function is safe to call as long as @cgrp
322 * and @ancestor are accessible.
324 bool cgroup_is_descendant(struct cgroup
*cgrp
, struct cgroup
*ancestor
)
327 if (cgrp
== ancestor
)
329 cgrp
= cgroup_parent(cgrp
);
334 static int cgroup_is_releasable(const struct cgroup
*cgrp
)
337 (1 << CGRP_RELEASABLE
) |
338 (1 << CGRP_NOTIFY_ON_RELEASE
);
339 return (cgrp
->flags
& bits
) == bits
;
342 static int notify_on_release(const struct cgroup
*cgrp
)
344 return test_bit(CGRP_NOTIFY_ON_RELEASE
, &cgrp
->flags
);
348 * for_each_css - iterate all css's of a cgroup
349 * @css: the iteration cursor
350 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
351 * @cgrp: the target cgroup to iterate css's of
353 * Should be called under cgroup_[tree_]mutex.
355 #define for_each_css(css, ssid, cgrp) \
356 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
357 if (!((css) = rcu_dereference_check( \
358 (cgrp)->subsys[(ssid)], \
359 lockdep_is_held(&cgroup_mutex)))) { } \
363 * for_each_e_css - iterate all effective css's of a cgroup
364 * @css: the iteration cursor
365 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
366 * @cgrp: the target cgroup to iterate css's of
368 * Should be called under cgroup_[tree_]mutex.
370 #define for_each_e_css(css, ssid, cgrp) \
371 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
372 if (!((css) = cgroup_e_css(cgrp, cgroup_subsys[(ssid)]))) \
377 * for_each_subsys - iterate all enabled cgroup subsystems
378 * @ss: the iteration cursor
379 * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
381 #define for_each_subsys(ss, ssid) \
382 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT && \
383 (((ss) = cgroup_subsys[ssid]) || true); (ssid)++)
385 /* iterate across the hierarchies */
386 #define for_each_root(root) \
387 list_for_each_entry((root), &cgroup_roots, root_list)
389 /* iterate over child cgrps, lock should be held throughout iteration */
390 #define cgroup_for_each_live_child(child, cgrp) \
391 list_for_each_entry((child), &(cgrp)->self.children, self.sibling) \
392 if (({ lockdep_assert_held(&cgroup_mutex); \
393 cgroup_is_dead(child); })) \
397 /* the list of cgroups eligible for automatic release. Protected by
398 * release_list_lock */
399 static LIST_HEAD(release_list
);
400 static DEFINE_RAW_SPINLOCK(release_list_lock
);
401 static void cgroup_release_agent(struct work_struct
*work
);
402 static DECLARE_WORK(release_agent_work
, cgroup_release_agent
);
403 static void check_for_release(struct cgroup
*cgrp
);
406 * A cgroup can be associated with multiple css_sets as different tasks may
407 * belong to different cgroups on different hierarchies. In the other
408 * direction, a css_set is naturally associated with multiple cgroups.
409 * This M:N relationship is represented by the following link structure
410 * which exists for each association and allows traversing the associations
413 struct cgrp_cset_link
{
414 /* the cgroup and css_set this link associates */
416 struct css_set
*cset
;
418 /* list of cgrp_cset_links anchored at cgrp->cset_links */
419 struct list_head cset_link
;
421 /* list of cgrp_cset_links anchored at css_set->cgrp_links */
422 struct list_head cgrp_link
;
426 * The default css_set - used by init and its children prior to any
427 * hierarchies being mounted. It contains a pointer to the root state
428 * for each subsystem. Also used to anchor the list of css_sets. Not
429 * reference-counted, to improve performance when child cgroups
430 * haven't been created.
432 struct css_set init_css_set
= {
433 .refcount
= ATOMIC_INIT(1),
434 .cgrp_links
= LIST_HEAD_INIT(init_css_set
.cgrp_links
),
435 .tasks
= LIST_HEAD_INIT(init_css_set
.tasks
),
436 .mg_tasks
= LIST_HEAD_INIT(init_css_set
.mg_tasks
),
437 .mg_preload_node
= LIST_HEAD_INIT(init_css_set
.mg_preload_node
),
438 .mg_node
= LIST_HEAD_INIT(init_css_set
.mg_node
),
441 static int css_set_count
= 1; /* 1 for init_css_set */
444 * cgroup_update_populated - updated populated count of a cgroup
445 * @cgrp: the target cgroup
446 * @populated: inc or dec populated count
448 * @cgrp is either getting the first task (css_set) or losing the last.
449 * Update @cgrp->populated_cnt accordingly. The count is propagated
450 * towards root so that a given cgroup's populated_cnt is zero iff the
451 * cgroup and all its descendants are empty.
453 * @cgrp's interface file "cgroup.populated" is zero if
454 * @cgrp->populated_cnt is zero and 1 otherwise. When @cgrp->populated_cnt
455 * changes from or to zero, userland is notified that the content of the
456 * interface file has changed. This can be used to detect when @cgrp and
457 * its descendants become populated or empty.
459 static void cgroup_update_populated(struct cgroup
*cgrp
, bool populated
)
461 lockdep_assert_held(&css_set_rwsem
);
467 trigger
= !cgrp
->populated_cnt
++;
469 trigger
= !--cgrp
->populated_cnt
;
474 if (cgrp
->populated_kn
)
475 kernfs_notify(cgrp
->populated_kn
);
476 cgrp
= cgroup_parent(cgrp
);
481 * hash table for cgroup groups. This improves the performance to find
482 * an existing css_set. This hash doesn't (currently) take into
483 * account cgroups in empty hierarchies.
485 #define CSS_SET_HASH_BITS 7
486 static DEFINE_HASHTABLE(css_set_table
, CSS_SET_HASH_BITS
);
488 static unsigned long css_set_hash(struct cgroup_subsys_state
*css
[])
490 unsigned long key
= 0UL;
491 struct cgroup_subsys
*ss
;
494 for_each_subsys(ss
, i
)
495 key
+= (unsigned long)css
[i
];
496 key
= (key
>> 16) ^ key
;
501 static void put_css_set_locked(struct css_set
*cset
, bool taskexit
)
503 struct cgrp_cset_link
*link
, *tmp_link
;
504 struct cgroup_subsys
*ss
;
507 lockdep_assert_held(&css_set_rwsem
);
509 if (!atomic_dec_and_test(&cset
->refcount
))
512 /* This css_set is dead. unlink it and release cgroup refcounts */
513 for_each_subsys(ss
, ssid
)
514 list_del(&cset
->e_cset_node
[ssid
]);
515 hash_del(&cset
->hlist
);
518 list_for_each_entry_safe(link
, tmp_link
, &cset
->cgrp_links
, cgrp_link
) {
519 struct cgroup
*cgrp
= link
->cgrp
;
521 list_del(&link
->cset_link
);
522 list_del(&link
->cgrp_link
);
524 /* @cgrp can't go away while we're holding css_set_rwsem */
525 if (list_empty(&cgrp
->cset_links
)) {
526 cgroup_update_populated(cgrp
, false);
527 if (notify_on_release(cgrp
)) {
529 set_bit(CGRP_RELEASABLE
, &cgrp
->flags
);
530 check_for_release(cgrp
);
537 kfree_rcu(cset
, rcu_head
);
540 static void put_css_set(struct css_set
*cset
, bool taskexit
)
543 * Ensure that the refcount doesn't hit zero while any readers
544 * can see it. Similar to atomic_dec_and_lock(), but for an
547 if (atomic_add_unless(&cset
->refcount
, -1, 1))
550 down_write(&css_set_rwsem
);
551 put_css_set_locked(cset
, taskexit
);
552 up_write(&css_set_rwsem
);
556 * refcounted get/put for css_set objects
558 static inline void get_css_set(struct css_set
*cset
)
560 atomic_inc(&cset
->refcount
);
564 * compare_css_sets - helper function for find_existing_css_set().
565 * @cset: candidate css_set being tested
566 * @old_cset: existing css_set for a task
567 * @new_cgrp: cgroup that's being entered by the task
568 * @template: desired set of css pointers in css_set (pre-calculated)
570 * Returns true if "cset" matches "old_cset" except for the hierarchy
571 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
573 static bool compare_css_sets(struct css_set
*cset
,
574 struct css_set
*old_cset
,
575 struct cgroup
*new_cgrp
,
576 struct cgroup_subsys_state
*template[])
578 struct list_head
*l1
, *l2
;
581 * On the default hierarchy, there can be csets which are
582 * associated with the same set of cgroups but different csses.
583 * Let's first ensure that csses match.
585 if (memcmp(template, cset
->subsys
, sizeof(cset
->subsys
)))
589 * Compare cgroup pointers in order to distinguish between
590 * different cgroups in hierarchies. As different cgroups may
591 * share the same effective css, this comparison is always
594 l1
= &cset
->cgrp_links
;
595 l2
= &old_cset
->cgrp_links
;
597 struct cgrp_cset_link
*link1
, *link2
;
598 struct cgroup
*cgrp1
, *cgrp2
;
602 /* See if we reached the end - both lists are equal length. */
603 if (l1
== &cset
->cgrp_links
) {
604 BUG_ON(l2
!= &old_cset
->cgrp_links
);
607 BUG_ON(l2
== &old_cset
->cgrp_links
);
609 /* Locate the cgroups associated with these links. */
610 link1
= list_entry(l1
, struct cgrp_cset_link
, cgrp_link
);
611 link2
= list_entry(l2
, struct cgrp_cset_link
, cgrp_link
);
614 /* Hierarchies should be linked in the same order. */
615 BUG_ON(cgrp1
->root
!= cgrp2
->root
);
618 * If this hierarchy is the hierarchy of the cgroup
619 * that's changing, then we need to check that this
620 * css_set points to the new cgroup; if it's any other
621 * hierarchy, then this css_set should point to the
622 * same cgroup as the old css_set.
624 if (cgrp1
->root
== new_cgrp
->root
) {
625 if (cgrp1
!= new_cgrp
)
636 * find_existing_css_set - init css array and find the matching css_set
637 * @old_cset: the css_set that we're using before the cgroup transition
638 * @cgrp: the cgroup that we're moving into
639 * @template: out param for the new set of csses, should be clear on entry
641 static struct css_set
*find_existing_css_set(struct css_set
*old_cset
,
643 struct cgroup_subsys_state
*template[])
645 struct cgroup_root
*root
= cgrp
->root
;
646 struct cgroup_subsys
*ss
;
647 struct css_set
*cset
;
652 * Build the set of subsystem state objects that we want to see in the
653 * new css_set. while subsystems can change globally, the entries here
654 * won't change, so no need for locking.
656 for_each_subsys(ss
, i
) {
657 if (root
->subsys_mask
& (1UL << i
)) {
659 * @ss is in this hierarchy, so we want the
660 * effective css from @cgrp.
662 template[i
] = cgroup_e_css(cgrp
, ss
);
665 * @ss is not in this hierarchy, so we don't want
668 template[i
] = old_cset
->subsys
[i
];
672 key
= css_set_hash(template);
673 hash_for_each_possible(css_set_table
, cset
, hlist
, key
) {
674 if (!compare_css_sets(cset
, old_cset
, cgrp
, template))
677 /* This css_set matches what we need */
681 /* No existing cgroup group matched */
685 static void free_cgrp_cset_links(struct list_head
*links_to_free
)
687 struct cgrp_cset_link
*link
, *tmp_link
;
689 list_for_each_entry_safe(link
, tmp_link
, links_to_free
, cset_link
) {
690 list_del(&link
->cset_link
);
696 * allocate_cgrp_cset_links - allocate cgrp_cset_links
697 * @count: the number of links to allocate
698 * @tmp_links: list_head the allocated links are put on
700 * Allocate @count cgrp_cset_link structures and chain them on @tmp_links
701 * through ->cset_link. Returns 0 on success or -errno.
703 static int allocate_cgrp_cset_links(int count
, struct list_head
*tmp_links
)
705 struct cgrp_cset_link
*link
;
708 INIT_LIST_HEAD(tmp_links
);
710 for (i
= 0; i
< count
; i
++) {
711 link
= kzalloc(sizeof(*link
), GFP_KERNEL
);
713 free_cgrp_cset_links(tmp_links
);
716 list_add(&link
->cset_link
, tmp_links
);
722 * link_css_set - a helper function to link a css_set to a cgroup
723 * @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()
724 * @cset: the css_set to be linked
725 * @cgrp: the destination cgroup
727 static void link_css_set(struct list_head
*tmp_links
, struct css_set
*cset
,
730 struct cgrp_cset_link
*link
;
732 BUG_ON(list_empty(tmp_links
));
734 if (cgroup_on_dfl(cgrp
))
735 cset
->dfl_cgrp
= cgrp
;
737 link
= list_first_entry(tmp_links
, struct cgrp_cset_link
, cset_link
);
741 if (list_empty(&cgrp
->cset_links
))
742 cgroup_update_populated(cgrp
, true);
743 list_move(&link
->cset_link
, &cgrp
->cset_links
);
746 * Always add links to the tail of the list so that the list
747 * is sorted by order of hierarchy creation
749 list_add_tail(&link
->cgrp_link
, &cset
->cgrp_links
);
753 * find_css_set - return a new css_set with one cgroup updated
754 * @old_cset: the baseline css_set
755 * @cgrp: the cgroup to be updated
757 * Return a new css_set that's equivalent to @old_cset, but with @cgrp
758 * substituted into the appropriate hierarchy.
760 static struct css_set
*find_css_set(struct css_set
*old_cset
,
763 struct cgroup_subsys_state
*template[CGROUP_SUBSYS_COUNT
] = { };
764 struct css_set
*cset
;
765 struct list_head tmp_links
;
766 struct cgrp_cset_link
*link
;
767 struct cgroup_subsys
*ss
;
771 lockdep_assert_held(&cgroup_mutex
);
773 /* First see if we already have a cgroup group that matches
775 down_read(&css_set_rwsem
);
776 cset
= find_existing_css_set(old_cset
, cgrp
, template);
779 up_read(&css_set_rwsem
);
784 cset
= kzalloc(sizeof(*cset
), GFP_KERNEL
);
788 /* Allocate all the cgrp_cset_link objects that we'll need */
789 if (allocate_cgrp_cset_links(cgroup_root_count
, &tmp_links
) < 0) {
794 atomic_set(&cset
->refcount
, 1);
795 INIT_LIST_HEAD(&cset
->cgrp_links
);
796 INIT_LIST_HEAD(&cset
->tasks
);
797 INIT_LIST_HEAD(&cset
->mg_tasks
);
798 INIT_LIST_HEAD(&cset
->mg_preload_node
);
799 INIT_LIST_HEAD(&cset
->mg_node
);
800 INIT_HLIST_NODE(&cset
->hlist
);
802 /* Copy the set of subsystem state objects generated in
803 * find_existing_css_set() */
804 memcpy(cset
->subsys
, template, sizeof(cset
->subsys
));
806 down_write(&css_set_rwsem
);
807 /* Add reference counts and links from the new css_set. */
808 list_for_each_entry(link
, &old_cset
->cgrp_links
, cgrp_link
) {
809 struct cgroup
*c
= link
->cgrp
;
811 if (c
->root
== cgrp
->root
)
813 link_css_set(&tmp_links
, cset
, c
);
816 BUG_ON(!list_empty(&tmp_links
));
820 /* Add @cset to the hash table */
821 key
= css_set_hash(cset
->subsys
);
822 hash_add(css_set_table
, &cset
->hlist
, key
);
824 for_each_subsys(ss
, ssid
)
825 list_add_tail(&cset
->e_cset_node
[ssid
],
826 &cset
->subsys
[ssid
]->cgroup
->e_csets
[ssid
]);
828 up_write(&css_set_rwsem
);
833 static struct cgroup_root
*cgroup_root_from_kf(struct kernfs_root
*kf_root
)
835 struct cgroup
*root_cgrp
= kf_root
->kn
->priv
;
837 return root_cgrp
->root
;
840 static int cgroup_init_root_id(struct cgroup_root
*root
)
844 lockdep_assert_held(&cgroup_mutex
);
846 id
= idr_alloc_cyclic(&cgroup_hierarchy_idr
, root
, 0, 0, GFP_KERNEL
);
850 root
->hierarchy_id
= id
;
854 static void cgroup_exit_root_id(struct cgroup_root
*root
)
856 lockdep_assert_held(&cgroup_mutex
);
858 if (root
->hierarchy_id
) {
859 idr_remove(&cgroup_hierarchy_idr
, root
->hierarchy_id
);
860 root
->hierarchy_id
= 0;
864 static void cgroup_free_root(struct cgroup_root
*root
)
867 /* hierarhcy ID shoulid already have been released */
868 WARN_ON_ONCE(root
->hierarchy_id
);
870 idr_destroy(&root
->cgroup_idr
);
875 static void cgroup_destroy_root(struct cgroup_root
*root
)
877 struct cgroup
*cgrp
= &root
->cgrp
;
878 struct cgrp_cset_link
*link
, *tmp_link
;
880 mutex_lock(&cgroup_mutex
);
882 BUG_ON(atomic_read(&root
->nr_cgrps
));
883 BUG_ON(!list_empty(&cgrp
->self
.children
));
885 /* Rebind all subsystems back to the default hierarchy */
886 rebind_subsystems(&cgrp_dfl_root
, root
->subsys_mask
);
889 * Release all the links from cset_links to this hierarchy's
892 down_write(&css_set_rwsem
);
894 list_for_each_entry_safe(link
, tmp_link
, &cgrp
->cset_links
, cset_link
) {
895 list_del(&link
->cset_link
);
896 list_del(&link
->cgrp_link
);
899 up_write(&css_set_rwsem
);
901 if (!list_empty(&root
->root_list
)) {
902 list_del(&root
->root_list
);
906 cgroup_exit_root_id(root
);
908 mutex_unlock(&cgroup_mutex
);
910 kernfs_destroy_root(root
->kf_root
);
911 cgroup_free_root(root
);
914 /* look up cgroup associated with given css_set on the specified hierarchy */
915 static struct cgroup
*cset_cgroup_from_root(struct css_set
*cset
,
916 struct cgroup_root
*root
)
918 struct cgroup
*res
= NULL
;
920 lockdep_assert_held(&cgroup_mutex
);
921 lockdep_assert_held(&css_set_rwsem
);
923 if (cset
== &init_css_set
) {
926 struct cgrp_cset_link
*link
;
928 list_for_each_entry(link
, &cset
->cgrp_links
, cgrp_link
) {
929 struct cgroup
*c
= link
->cgrp
;
931 if (c
->root
== root
) {
943 * Return the cgroup for "task" from the given hierarchy. Must be
944 * called with cgroup_mutex and css_set_rwsem held.
946 static struct cgroup
*task_cgroup_from_root(struct task_struct
*task
,
947 struct cgroup_root
*root
)
950 * No need to lock the task - since we hold cgroup_mutex the
951 * task can't change groups, so the only thing that can happen
952 * is that it exits and its css is set back to init_css_set.
954 return cset_cgroup_from_root(task_css_set(task
), root
);
958 * A task must hold cgroup_mutex to modify cgroups.
960 * Any task can increment and decrement the count field without lock.
961 * So in general, code holding cgroup_mutex can't rely on the count
962 * field not changing. However, if the count goes to zero, then only
963 * cgroup_attach_task() can increment it again. Because a count of zero
964 * means that no tasks are currently attached, therefore there is no
965 * way a task attached to that cgroup can fork (the other way to
966 * increment the count). So code holding cgroup_mutex can safely
967 * assume that if the count is zero, it will stay zero. Similarly, if
968 * a task holds cgroup_mutex on a cgroup with zero count, it
969 * knows that the cgroup won't be removed, as cgroup_rmdir()
972 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
973 * (usually) take cgroup_mutex. These are the two most performance
974 * critical pieces of code here. The exception occurs on cgroup_exit(),
975 * when a task in a notify_on_release cgroup exits. Then cgroup_mutex
976 * is taken, and if the cgroup count is zero, a usermode call made
977 * to the release agent with the name of the cgroup (path relative to
978 * the root of cgroup file system) as the argument.
980 * A cgroup can only be deleted if both its 'count' of using tasks
981 * is zero, and its list of 'children' cgroups is empty. Since all
982 * tasks in the system use _some_ cgroup, and since there is always at
983 * least one task in the system (init, pid == 1), therefore, root cgroup
984 * always has either children cgroups and/or using tasks. So we don't
985 * need a special hack to ensure that root cgroup cannot be deleted.
987 * P.S. One more locking exception. RCU is used to guard the
988 * update of a tasks cgroup pointer by cgroup_attach_task()
991 static int cgroup_populate_dir(struct cgroup
*cgrp
, unsigned int subsys_mask
);
992 static struct kernfs_syscall_ops cgroup_kf_syscall_ops
;
993 static const struct file_operations proc_cgroupstats_operations
;
995 static char *cgroup_file_name(struct cgroup
*cgrp
, const struct cftype
*cft
,
998 if (cft
->ss
&& !(cft
->flags
& CFTYPE_NO_PREFIX
) &&
999 !(cgrp
->root
->flags
& CGRP_ROOT_NOPREFIX
))
1000 snprintf(buf
, CGROUP_FILE_NAME_MAX
, "%s.%s",
1001 cft
->ss
->name
, cft
->name
);
1003 strncpy(buf
, cft
->name
, CGROUP_FILE_NAME_MAX
);
1008 * cgroup_file_mode - deduce file mode of a control file
1009 * @cft: the control file in question
1011 * returns cft->mode if ->mode is not 0
1012 * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
1013 * returns S_IRUGO if it has only a read handler
1014 * returns S_IWUSR if it has only a write hander
1016 static umode_t
cgroup_file_mode(const struct cftype
*cft
)
1023 if (cft
->read_u64
|| cft
->read_s64
|| cft
->seq_show
)
1026 if (cft
->write_u64
|| cft
->write_s64
|| cft
->write
)
1032 static void cgroup_get(struct cgroup
*cgrp
)
1034 WARN_ON_ONCE(cgroup_is_dead(cgrp
));
1035 css_get(&cgrp
->self
);
1038 static void cgroup_put(struct cgroup
*cgrp
)
1040 css_put(&cgrp
->self
);
1044 * cgroup_refresh_child_subsys_mask - update child_subsys_mask
1045 * @cgrp: the target cgroup
1047 * On the default hierarchy, a subsystem may request other subsystems to be
1048 * enabled together through its ->depends_on mask. In such cases, more
1049 * subsystems than specified in "cgroup.subtree_control" may be enabled.
1051 * This function determines which subsystems need to be enabled given the
1052 * current @cgrp->subtree_control and records it in
1053 * @cgrp->child_subsys_mask. The resulting mask is always a superset of
1054 * @cgrp->subtree_control and follows the usual hierarchy rules.
1056 static void cgroup_refresh_child_subsys_mask(struct cgroup
*cgrp
)
1058 struct cgroup
*parent
= cgroup_parent(cgrp
);
1059 unsigned int cur_ss_mask
= cgrp
->subtree_control
;
1060 struct cgroup_subsys
*ss
;
1063 lockdep_assert_held(&cgroup_mutex
);
1065 if (!cgroup_on_dfl(cgrp
)) {
1066 cgrp
->child_subsys_mask
= cur_ss_mask
;
1071 unsigned int new_ss_mask
= cur_ss_mask
;
1073 for_each_subsys(ss
, ssid
)
1074 if (cur_ss_mask
& (1 << ssid
))
1075 new_ss_mask
|= ss
->depends_on
;
1078 * Mask out subsystems which aren't available. This can
1079 * happen only if some depended-upon subsystems were bound
1080 * to non-default hierarchies.
1083 new_ss_mask
&= parent
->child_subsys_mask
;
1085 new_ss_mask
&= cgrp
->root
->subsys_mask
;
1087 if (new_ss_mask
== cur_ss_mask
)
1089 cur_ss_mask
= new_ss_mask
;
1092 cgrp
->child_subsys_mask
= cur_ss_mask
;
1096 * cgroup_kn_unlock - unlocking helper for cgroup kernfs methods
1097 * @kn: the kernfs_node being serviced
1099 * This helper undoes cgroup_kn_lock_live() and should be invoked before
1100 * the method finishes if locking succeeded. Note that once this function
1101 * returns the cgroup returned by cgroup_kn_lock_live() may become
1102 * inaccessible any time. If the caller intends to continue to access the
1103 * cgroup, it should pin it before invoking this function.
1105 static void cgroup_kn_unlock(struct kernfs_node
*kn
)
1107 struct cgroup
*cgrp
;
1109 if (kernfs_type(kn
) == KERNFS_DIR
)
1112 cgrp
= kn
->parent
->priv
;
1114 mutex_unlock(&cgroup_mutex
);
1116 kernfs_unbreak_active_protection(kn
);
1121 * cgroup_kn_lock_live - locking helper for cgroup kernfs methods
1122 * @kn: the kernfs_node being serviced
1124 * This helper is to be used by a cgroup kernfs method currently servicing
1125 * @kn. It breaks the active protection, performs cgroup locking and
1126 * verifies that the associated cgroup is alive. Returns the cgroup if
1127 * alive; otherwise, %NULL. A successful return should be undone by a
1128 * matching cgroup_kn_unlock() invocation.
1130 * Any cgroup kernfs method implementation which requires locking the
1131 * associated cgroup should use this helper. It avoids nesting cgroup
1132 * locking under kernfs active protection and allows all kernfs operations
1133 * including self-removal.
1135 static struct cgroup
*cgroup_kn_lock_live(struct kernfs_node
*kn
)
1137 struct cgroup
*cgrp
;
1139 if (kernfs_type(kn
) == KERNFS_DIR
)
1142 cgrp
= kn
->parent
->priv
;
1145 * We're gonna grab cgroup_mutex which nests outside kernfs
1146 * active_ref. cgroup liveliness check alone provides enough
1147 * protection against removal. Ensure @cgrp stays accessible and
1148 * break the active_ref protection.
1151 kernfs_break_active_protection(kn
);
1153 mutex_lock(&cgroup_mutex
);
1155 if (!cgroup_is_dead(cgrp
))
1158 cgroup_kn_unlock(kn
);
1162 static void cgroup_rm_file(struct cgroup
*cgrp
, const struct cftype
*cft
)
1164 char name
[CGROUP_FILE_NAME_MAX
];
1166 lockdep_assert_held(&cgroup_mutex
);
1167 kernfs_remove_by_name(cgrp
->kn
, cgroup_file_name(cgrp
, cft
, name
));
1171 * cgroup_clear_dir - remove subsys files in a cgroup directory
1172 * @cgrp: target cgroup
1173 * @subsys_mask: mask of the subsystem ids whose files should be removed
1175 static void cgroup_clear_dir(struct cgroup
*cgrp
, unsigned int subsys_mask
)
1177 struct cgroup_subsys
*ss
;
1180 for_each_subsys(ss
, i
) {
1181 struct cftype
*cfts
;
1183 if (!(subsys_mask
& (1 << i
)))
1185 list_for_each_entry(cfts
, &ss
->cfts
, node
)
1186 cgroup_addrm_files(cgrp
, cfts
, false);
1190 static int rebind_subsystems(struct cgroup_root
*dst_root
, unsigned int ss_mask
)
1192 struct cgroup_subsys
*ss
;
1193 unsigned int tmp_ss_mask
;
1196 lockdep_assert_held(&cgroup_mutex
);
1198 for_each_subsys(ss
, ssid
) {
1199 if (!(ss_mask
& (1 << ssid
)))
1202 /* if @ss has non-root csses attached to it, can't move */
1203 if (css_next_child(NULL
, cgroup_css(&ss
->root
->cgrp
, ss
)))
1206 /* can't move between two non-dummy roots either */
1207 if (ss
->root
!= &cgrp_dfl_root
&& dst_root
!= &cgrp_dfl_root
)
1211 /* skip creating root files on dfl_root for inhibited subsystems */
1212 tmp_ss_mask
= ss_mask
;
1213 if (dst_root
== &cgrp_dfl_root
)
1214 tmp_ss_mask
&= ~cgrp_dfl_root_inhibit_ss_mask
;
1216 ret
= cgroup_populate_dir(&dst_root
->cgrp
, tmp_ss_mask
);
1218 if (dst_root
!= &cgrp_dfl_root
)
1222 * Rebinding back to the default root is not allowed to
1223 * fail. Using both default and non-default roots should
1224 * be rare. Moving subsystems back and forth even more so.
1225 * Just warn about it and continue.
1227 if (cgrp_dfl_root_visible
) {
1228 pr_warn("failed to create files (%d) while rebinding 0x%x to default root\n",
1230 pr_warn("you may retry by moving them to a different hierarchy and unbinding\n");
1235 * Nothing can fail from this point on. Remove files for the
1236 * removed subsystems and rebind each subsystem.
1238 for_each_subsys(ss
, ssid
)
1239 if (ss_mask
& (1 << ssid
))
1240 cgroup_clear_dir(&ss
->root
->cgrp
, 1 << ssid
);
1242 for_each_subsys(ss
, ssid
) {
1243 struct cgroup_root
*src_root
;
1244 struct cgroup_subsys_state
*css
;
1245 struct css_set
*cset
;
1247 if (!(ss_mask
& (1 << ssid
)))
1250 src_root
= ss
->root
;
1251 css
= cgroup_css(&src_root
->cgrp
, ss
);
1253 WARN_ON(!css
|| cgroup_css(&dst_root
->cgrp
, ss
));
1255 RCU_INIT_POINTER(src_root
->cgrp
.subsys
[ssid
], NULL
);
1256 rcu_assign_pointer(dst_root
->cgrp
.subsys
[ssid
], css
);
1257 ss
->root
= dst_root
;
1258 css
->cgroup
= &dst_root
->cgrp
;
1260 down_write(&css_set_rwsem
);
1261 hash_for_each(css_set_table
, i
, cset
, hlist
)
1262 list_move_tail(&cset
->e_cset_node
[ss
->id
],
1263 &dst_root
->cgrp
.e_csets
[ss
->id
]);
1264 up_write(&css_set_rwsem
);
1266 src_root
->subsys_mask
&= ~(1 << ssid
);
1267 src_root
->cgrp
.subtree_control
&= ~(1 << ssid
);
1268 cgroup_refresh_child_subsys_mask(&src_root
->cgrp
);
1270 /* default hierarchy doesn't enable controllers by default */
1271 dst_root
->subsys_mask
|= 1 << ssid
;
1272 if (dst_root
!= &cgrp_dfl_root
) {
1273 dst_root
->cgrp
.subtree_control
|= 1 << ssid
;
1274 cgroup_refresh_child_subsys_mask(&dst_root
->cgrp
);
1281 kernfs_activate(dst_root
->cgrp
.kn
);
1285 static int cgroup_show_options(struct seq_file
*seq
,
1286 struct kernfs_root
*kf_root
)
1288 struct cgroup_root
*root
= cgroup_root_from_kf(kf_root
);
1289 struct cgroup_subsys
*ss
;
1292 for_each_subsys(ss
, ssid
)
1293 if (root
->subsys_mask
& (1 << ssid
))
1294 seq_printf(seq
, ",%s", ss
->name
);
1295 if (root
->flags
& CGRP_ROOT_NOPREFIX
)
1296 seq_puts(seq
, ",noprefix");
1297 if (root
->flags
& CGRP_ROOT_XATTR
)
1298 seq_puts(seq
, ",xattr");
1300 spin_lock(&release_agent_path_lock
);
1301 if (strlen(root
->release_agent_path
))
1302 seq_printf(seq
, ",release_agent=%s", root
->release_agent_path
);
1303 spin_unlock(&release_agent_path_lock
);
1305 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN
, &root
->cgrp
.flags
))
1306 seq_puts(seq
, ",clone_children");
1307 if (strlen(root
->name
))
1308 seq_printf(seq
, ",name=%s", root
->name
);
1312 struct cgroup_sb_opts
{
1313 unsigned int subsys_mask
;
1315 char *release_agent
;
1316 bool cpuset_clone_children
;
1318 /* User explicitly requested empty subsystem */
1322 static int parse_cgroupfs_options(char *data
, struct cgroup_sb_opts
*opts
)
1324 char *token
, *o
= data
;
1325 bool all_ss
= false, one_ss
= false;
1326 unsigned int mask
= -1U;
1327 struct cgroup_subsys
*ss
;
1331 #ifdef CONFIG_CPUSETS
1332 mask
= ~(1U << cpuset_cgrp_id
);
1335 memset(opts
, 0, sizeof(*opts
));
1337 while ((token
= strsep(&o
, ",")) != NULL
) {
1342 if (!strcmp(token
, "none")) {
1343 /* Explicitly have no subsystems */
1347 if (!strcmp(token
, "all")) {
1348 /* Mutually exclusive option 'all' + subsystem name */
1354 if (!strcmp(token
, "__DEVEL__sane_behavior")) {
1355 opts
->flags
|= CGRP_ROOT_SANE_BEHAVIOR
;
1358 if (!strcmp(token
, "noprefix")) {
1359 opts
->flags
|= CGRP_ROOT_NOPREFIX
;
1362 if (!strcmp(token
, "clone_children")) {
1363 opts
->cpuset_clone_children
= true;
1366 if (!strcmp(token
, "xattr")) {
1367 opts
->flags
|= CGRP_ROOT_XATTR
;
1370 if (!strncmp(token
, "release_agent=", 14)) {
1371 /* Specifying two release agents is forbidden */
1372 if (opts
->release_agent
)
1374 opts
->release_agent
=
1375 kstrndup(token
+ 14, PATH_MAX
- 1, GFP_KERNEL
);
1376 if (!opts
->release_agent
)
1380 if (!strncmp(token
, "name=", 5)) {
1381 const char *name
= token
+ 5;
1382 /* Can't specify an empty name */
1385 /* Must match [\w.-]+ */
1386 for (i
= 0; i
< strlen(name
); i
++) {
1390 if ((c
== '.') || (c
== '-') || (c
== '_'))
1394 /* Specifying two names is forbidden */
1397 opts
->name
= kstrndup(name
,
1398 MAX_CGROUP_ROOT_NAMELEN
- 1,
1406 for_each_subsys(ss
, i
) {
1407 if (strcmp(token
, ss
->name
))
1412 /* Mutually exclusive option 'all' + subsystem name */
1415 opts
->subsys_mask
|= (1 << i
);
1420 if (i
== CGROUP_SUBSYS_COUNT
)
1424 if (opts
->flags
& CGRP_ROOT_SANE_BEHAVIOR
) {
1425 pr_warn("sane_behavior: this is still under development and its behaviors will change, proceed at your own risk\n");
1427 pr_err("sane_behavior: no other mount options allowed\n");
1434 * If the 'all' option was specified select all the subsystems,
1435 * otherwise if 'none', 'name=' and a subsystem name options were
1436 * not specified, let's default to 'all'
1438 if (all_ss
|| (!one_ss
&& !opts
->none
&& !opts
->name
))
1439 for_each_subsys(ss
, i
)
1441 opts
->subsys_mask
|= (1 << i
);
1444 * We either have to specify by name or by subsystems. (So all
1445 * empty hierarchies must have a name).
1447 if (!opts
->subsys_mask
&& !opts
->name
)
1451 * Option noprefix was introduced just for backward compatibility
1452 * with the old cpuset, so we allow noprefix only if mounting just
1453 * the cpuset subsystem.
1455 if ((opts
->flags
& CGRP_ROOT_NOPREFIX
) && (opts
->subsys_mask
& mask
))
1458 /* Can't specify "none" and some subsystems */
1459 if (opts
->subsys_mask
&& opts
->none
)
1465 static int cgroup_remount(struct kernfs_root
*kf_root
, int *flags
, char *data
)
1468 struct cgroup_root
*root
= cgroup_root_from_kf(kf_root
);
1469 struct cgroup_sb_opts opts
;
1470 unsigned int added_mask
, removed_mask
;
1472 if (root
== &cgrp_dfl_root
) {
1473 pr_err("remount is not allowed\n");
1477 mutex_lock(&cgroup_mutex
);
1479 /* See what subsystems are wanted */
1480 ret
= parse_cgroupfs_options(data
, &opts
);
1484 if (opts
.subsys_mask
!= root
->subsys_mask
|| opts
.release_agent
)
1485 pr_warn("option changes via remount are deprecated (pid=%d comm=%s)\n",
1486 task_tgid_nr(current
), current
->comm
);
1488 added_mask
= opts
.subsys_mask
& ~root
->subsys_mask
;
1489 removed_mask
= root
->subsys_mask
& ~opts
.subsys_mask
;
1491 /* Don't allow flags or name to change at remount */
1492 if ((opts
.flags
^ root
->flags
) ||
1493 (opts
.name
&& strcmp(opts
.name
, root
->name
))) {
1494 pr_err("option or name mismatch, new: 0x%x \"%s\", old: 0x%x \"%s\"\n",
1495 opts
.flags
, opts
.name
?: "", root
->flags
, root
->name
);
1500 /* remounting is not allowed for populated hierarchies */
1501 if (!list_empty(&root
->cgrp
.self
.children
)) {
1506 ret
= rebind_subsystems(root
, added_mask
);
1510 rebind_subsystems(&cgrp_dfl_root
, removed_mask
);
1512 if (opts
.release_agent
) {
1513 spin_lock(&release_agent_path_lock
);
1514 strcpy(root
->release_agent_path
, opts
.release_agent
);
1515 spin_unlock(&release_agent_path_lock
);
1518 kfree(opts
.release_agent
);
1520 mutex_unlock(&cgroup_mutex
);
1525 * To reduce the fork() overhead for systems that are not actually using
1526 * their cgroups capability, we don't maintain the lists running through
1527 * each css_set to its tasks until we see the list actually used - in other
1528 * words after the first mount.
1530 static bool use_task_css_set_links __read_mostly
;
1532 static void cgroup_enable_task_cg_lists(void)
1534 struct task_struct
*p
, *g
;
1536 down_write(&css_set_rwsem
);
1538 if (use_task_css_set_links
)
1541 use_task_css_set_links
= true;
1544 * We need tasklist_lock because RCU is not safe against
1545 * while_each_thread(). Besides, a forking task that has passed
1546 * cgroup_post_fork() without seeing use_task_css_set_links = 1
1547 * is not guaranteed to have its child immediately visible in the
1548 * tasklist if we walk through it with RCU.
1550 read_lock(&tasklist_lock
);
1551 do_each_thread(g
, p
) {
1552 WARN_ON_ONCE(!list_empty(&p
->cg_list
) ||
1553 task_css_set(p
) != &init_css_set
);
1556 * We should check if the process is exiting, otherwise
1557 * it will race with cgroup_exit() in that the list
1558 * entry won't be deleted though the process has exited.
1559 * Do it while holding siglock so that we don't end up
1560 * racing against cgroup_exit().
1562 spin_lock_irq(&p
->sighand
->siglock
);
1563 if (!(p
->flags
& PF_EXITING
)) {
1564 struct css_set
*cset
= task_css_set(p
);
1566 list_add(&p
->cg_list
, &cset
->tasks
);
1569 spin_unlock_irq(&p
->sighand
->siglock
);
1570 } while_each_thread(g
, p
);
1571 read_unlock(&tasklist_lock
);
1573 up_write(&css_set_rwsem
);
1576 static void init_cgroup_housekeeping(struct cgroup
*cgrp
)
1578 struct cgroup_subsys
*ss
;
1581 INIT_LIST_HEAD(&cgrp
->self
.sibling
);
1582 INIT_LIST_HEAD(&cgrp
->self
.children
);
1583 INIT_LIST_HEAD(&cgrp
->cset_links
);
1584 INIT_LIST_HEAD(&cgrp
->release_list
);
1585 INIT_LIST_HEAD(&cgrp
->pidlists
);
1586 mutex_init(&cgrp
->pidlist_mutex
);
1587 cgrp
->self
.cgroup
= cgrp
;
1588 cgrp
->self
.flags
|= CSS_ONLINE
;
1590 for_each_subsys(ss
, ssid
)
1591 INIT_LIST_HEAD(&cgrp
->e_csets
[ssid
]);
1593 init_waitqueue_head(&cgrp
->offline_waitq
);
1596 static void init_cgroup_root(struct cgroup_root
*root
,
1597 struct cgroup_sb_opts
*opts
)
1599 struct cgroup
*cgrp
= &root
->cgrp
;
1601 INIT_LIST_HEAD(&root
->root_list
);
1602 atomic_set(&root
->nr_cgrps
, 1);
1604 init_cgroup_housekeeping(cgrp
);
1605 idr_init(&root
->cgroup_idr
);
1607 root
->flags
= opts
->flags
;
1608 if (opts
->release_agent
)
1609 strcpy(root
->release_agent_path
, opts
->release_agent
);
1611 strcpy(root
->name
, opts
->name
);
1612 if (opts
->cpuset_clone_children
)
1613 set_bit(CGRP_CPUSET_CLONE_CHILDREN
, &root
->cgrp
.flags
);
1616 static int cgroup_setup_root(struct cgroup_root
*root
, unsigned int ss_mask
)
1618 LIST_HEAD(tmp_links
);
1619 struct cgroup
*root_cgrp
= &root
->cgrp
;
1620 struct cftype
*base_files
;
1621 struct css_set
*cset
;
1624 lockdep_assert_held(&cgroup_mutex
);
1626 ret
= cgroup_idr_alloc(&root
->cgroup_idr
, root_cgrp
, 1, 2, GFP_NOWAIT
);
1629 root_cgrp
->id
= ret
;
1631 ret
= percpu_ref_init(&root_cgrp
->self
.refcnt
, css_release
);
1636 * We're accessing css_set_count without locking css_set_rwsem here,
1637 * but that's OK - it can only be increased by someone holding
1638 * cgroup_lock, and that's us. The worst that can happen is that we
1639 * have some link structures left over
1641 ret
= allocate_cgrp_cset_links(css_set_count
, &tmp_links
);
1645 ret
= cgroup_init_root_id(root
);
1649 root
->kf_root
= kernfs_create_root(&cgroup_kf_syscall_ops
,
1650 KERNFS_ROOT_CREATE_DEACTIVATED
,
1652 if (IS_ERR(root
->kf_root
)) {
1653 ret
= PTR_ERR(root
->kf_root
);
1656 root_cgrp
->kn
= root
->kf_root
->kn
;
1658 if (root
== &cgrp_dfl_root
)
1659 base_files
= cgroup_dfl_base_files
;
1661 base_files
= cgroup_legacy_base_files
;
1663 ret
= cgroup_addrm_files(root_cgrp
, base_files
, true);
1667 ret
= rebind_subsystems(root
, ss_mask
);
1672 * There must be no failure case after here, since rebinding takes
1673 * care of subsystems' refcounts, which are explicitly dropped in
1674 * the failure exit path.
1676 list_add(&root
->root_list
, &cgroup_roots
);
1677 cgroup_root_count
++;
1680 * Link the root cgroup in this hierarchy into all the css_set
1683 down_write(&css_set_rwsem
);
1684 hash_for_each(css_set_table
, i
, cset
, hlist
)
1685 link_css_set(&tmp_links
, cset
, root_cgrp
);
1686 up_write(&css_set_rwsem
);
1688 BUG_ON(!list_empty(&root_cgrp
->self
.children
));
1689 BUG_ON(atomic_read(&root
->nr_cgrps
) != 1);
1691 kernfs_activate(root_cgrp
->kn
);
1696 kernfs_destroy_root(root
->kf_root
);
1697 root
->kf_root
= NULL
;
1699 cgroup_exit_root_id(root
);
1701 percpu_ref_exit(&root_cgrp
->self
.refcnt
);
1703 free_cgrp_cset_links(&tmp_links
);
1707 static struct dentry
*cgroup_mount(struct file_system_type
*fs_type
,
1708 int flags
, const char *unused_dev_name
,
1711 struct super_block
*pinned_sb
= NULL
;
1712 struct cgroup_subsys
*ss
;
1713 struct cgroup_root
*root
;
1714 struct cgroup_sb_opts opts
;
1715 struct dentry
*dentry
;
1721 * The first time anyone tries to mount a cgroup, enable the list
1722 * linking each css_set to its tasks and fix up all existing tasks.
1724 if (!use_task_css_set_links
)
1725 cgroup_enable_task_cg_lists();
1727 mutex_lock(&cgroup_mutex
);
1729 /* First find the desired set of subsystems */
1730 ret
= parse_cgroupfs_options(data
, &opts
);
1734 /* look for a matching existing root */
1735 if (opts
.flags
& CGRP_ROOT_SANE_BEHAVIOR
) {
1736 cgrp_dfl_root_visible
= true;
1737 root
= &cgrp_dfl_root
;
1738 cgroup_get(&root
->cgrp
);
1744 * Destruction of cgroup root is asynchronous, so subsystems may
1745 * still be dying after the previous unmount. Let's drain the
1746 * dying subsystems. We just need to ensure that the ones
1747 * unmounted previously finish dying and don't care about new ones
1748 * starting. Testing ref liveliness is good enough.
1750 for_each_subsys(ss
, i
) {
1751 if (!(opts
.subsys_mask
& (1 << i
)) ||
1752 ss
->root
== &cgrp_dfl_root
)
1755 if (!percpu_ref_tryget_live(&ss
->root
->cgrp
.self
.refcnt
)) {
1756 mutex_unlock(&cgroup_mutex
);
1758 ret
= restart_syscall();
1761 cgroup_put(&ss
->root
->cgrp
);
1764 for_each_root(root
) {
1765 bool name_match
= false;
1767 if (root
== &cgrp_dfl_root
)
1771 * If we asked for a name then it must match. Also, if
1772 * name matches but sybsys_mask doesn't, we should fail.
1773 * Remember whether name matched.
1776 if (strcmp(opts
.name
, root
->name
))
1782 * If we asked for subsystems (or explicitly for no
1783 * subsystems) then they must match.
1785 if ((opts
.subsys_mask
|| opts
.none
) &&
1786 (opts
.subsys_mask
!= root
->subsys_mask
)) {
1793 if (root
->flags
^ opts
.flags
)
1794 pr_warn("new mount options do not match the existing superblock, will be ignored\n");
1797 * We want to reuse @root whose lifetime is governed by its
1798 * ->cgrp. Let's check whether @root is alive and keep it
1799 * that way. As cgroup_kill_sb() can happen anytime, we
1800 * want to block it by pinning the sb so that @root doesn't
1801 * get killed before mount is complete.
1803 * With the sb pinned, tryget_live can reliably indicate
1804 * whether @root can be reused. If it's being killed,
1805 * drain it. We can use wait_queue for the wait but this
1806 * path is super cold. Let's just sleep a bit and retry.
1808 pinned_sb
= kernfs_pin_sb(root
->kf_root
, NULL
);
1809 if (IS_ERR(pinned_sb
) ||
1810 !percpu_ref_tryget_live(&root
->cgrp
.self
.refcnt
)) {
1811 mutex_unlock(&cgroup_mutex
);
1812 if (!IS_ERR_OR_NULL(pinned_sb
))
1813 deactivate_super(pinned_sb
);
1815 ret
= restart_syscall();
1824 * No such thing, create a new one. name= matching without subsys
1825 * specification is allowed for already existing hierarchies but we
1826 * can't create new one without subsys specification.
1828 if (!opts
.subsys_mask
&& !opts
.none
) {
1833 root
= kzalloc(sizeof(*root
), GFP_KERNEL
);
1839 init_cgroup_root(root
, &opts
);
1841 ret
= cgroup_setup_root(root
, opts
.subsys_mask
);
1843 cgroup_free_root(root
);
1846 mutex_unlock(&cgroup_mutex
);
1848 kfree(opts
.release_agent
);
1852 return ERR_PTR(ret
);
1854 dentry
= kernfs_mount(fs_type
, flags
, root
->kf_root
,
1855 CGROUP_SUPER_MAGIC
, &new_sb
);
1856 if (IS_ERR(dentry
) || !new_sb
)
1857 cgroup_put(&root
->cgrp
);
1860 * If @pinned_sb, we're reusing an existing root and holding an
1861 * extra ref on its sb. Mount is complete. Put the extra ref.
1865 deactivate_super(pinned_sb
);
1871 static void cgroup_kill_sb(struct super_block
*sb
)
1873 struct kernfs_root
*kf_root
= kernfs_root_from_sb(sb
);
1874 struct cgroup_root
*root
= cgroup_root_from_kf(kf_root
);
1877 * If @root doesn't have any mounts or children, start killing it.
1878 * This prevents new mounts by disabling percpu_ref_tryget_live().
1879 * cgroup_mount() may wait for @root's release.
1881 * And don't kill the default root.
1883 if (css_has_online_children(&root
->cgrp
.self
) ||
1884 root
== &cgrp_dfl_root
)
1885 cgroup_put(&root
->cgrp
);
1887 percpu_ref_kill(&root
->cgrp
.self
.refcnt
);
1892 static struct file_system_type cgroup_fs_type
= {
1894 .mount
= cgroup_mount
,
1895 .kill_sb
= cgroup_kill_sb
,
1898 static struct kobject
*cgroup_kobj
;
1901 * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
1902 * @task: target task
1903 * @buf: the buffer to write the path into
1904 * @buflen: the length of the buffer
1906 * Determine @task's cgroup on the first (the one with the lowest non-zero
1907 * hierarchy_id) cgroup hierarchy and copy its path into @buf. This
1908 * function grabs cgroup_mutex and shouldn't be used inside locks used by
1909 * cgroup controller callbacks.
1911 * Return value is the same as kernfs_path().
1913 char *task_cgroup_path(struct task_struct
*task
, char *buf
, size_t buflen
)
1915 struct cgroup_root
*root
;
1916 struct cgroup
*cgrp
;
1917 int hierarchy_id
= 1;
1920 mutex_lock(&cgroup_mutex
);
1921 down_read(&css_set_rwsem
);
1923 root
= idr_get_next(&cgroup_hierarchy_idr
, &hierarchy_id
);
1926 cgrp
= task_cgroup_from_root(task
, root
);
1927 path
= cgroup_path(cgrp
, buf
, buflen
);
1929 /* if no hierarchy exists, everyone is in "/" */
1930 if (strlcpy(buf
, "/", buflen
) < buflen
)
1934 up_read(&css_set_rwsem
);
1935 mutex_unlock(&cgroup_mutex
);
1938 EXPORT_SYMBOL_GPL(task_cgroup_path
);
1940 /* used to track tasks and other necessary states during migration */
1941 struct cgroup_taskset
{
1942 /* the src and dst cset list running through cset->mg_node */
1943 struct list_head src_csets
;
1944 struct list_head dst_csets
;
1947 * Fields for cgroup_taskset_*() iteration.
1949 * Before migration is committed, the target migration tasks are on
1950 * ->mg_tasks of the csets on ->src_csets. After, on ->mg_tasks of
1951 * the csets on ->dst_csets. ->csets point to either ->src_csets
1952 * or ->dst_csets depending on whether migration is committed.
1954 * ->cur_csets and ->cur_task point to the current task position
1957 struct list_head
*csets
;
1958 struct css_set
*cur_cset
;
1959 struct task_struct
*cur_task
;
1963 * cgroup_taskset_first - reset taskset and return the first task
1964 * @tset: taskset of interest
1966 * @tset iteration is initialized and the first task is returned.
1968 struct task_struct
*cgroup_taskset_first(struct cgroup_taskset
*tset
)
1970 tset
->cur_cset
= list_first_entry(tset
->csets
, struct css_set
, mg_node
);
1971 tset
->cur_task
= NULL
;
1973 return cgroup_taskset_next(tset
);
1977 * cgroup_taskset_next - iterate to the next task in taskset
1978 * @tset: taskset of interest
1980 * Return the next task in @tset. Iteration must have been initialized
1981 * with cgroup_taskset_first().
1983 struct task_struct
*cgroup_taskset_next(struct cgroup_taskset
*tset
)
1985 struct css_set
*cset
= tset
->cur_cset
;
1986 struct task_struct
*task
= tset
->cur_task
;
1988 while (&cset
->mg_node
!= tset
->csets
) {
1990 task
= list_first_entry(&cset
->mg_tasks
,
1991 struct task_struct
, cg_list
);
1993 task
= list_next_entry(task
, cg_list
);
1995 if (&task
->cg_list
!= &cset
->mg_tasks
) {
1996 tset
->cur_cset
= cset
;
1997 tset
->cur_task
= task
;
2001 cset
= list_next_entry(cset
, mg_node
);
2009 * cgroup_task_migrate - move a task from one cgroup to another.
2010 * @old_cgrp: the cgroup @tsk is being migrated from
2011 * @tsk: the task being migrated
2012 * @new_cset: the new css_set @tsk is being attached to
2014 * Must be called with cgroup_mutex, threadgroup and css_set_rwsem locked.
2016 static void cgroup_task_migrate(struct cgroup
*old_cgrp
,
2017 struct task_struct
*tsk
,
2018 struct css_set
*new_cset
)
2020 struct css_set
*old_cset
;
2022 lockdep_assert_held(&cgroup_mutex
);
2023 lockdep_assert_held(&css_set_rwsem
);
2026 * We are synchronized through threadgroup_lock() against PF_EXITING
2027 * setting such that we can't race against cgroup_exit() changing the
2028 * css_set to init_css_set and dropping the old one.
2030 WARN_ON_ONCE(tsk
->flags
& PF_EXITING
);
2031 old_cset
= task_css_set(tsk
);
2033 get_css_set(new_cset
);
2034 rcu_assign_pointer(tsk
->cgroups
, new_cset
);
2037 * Use move_tail so that cgroup_taskset_first() still returns the
2038 * leader after migration. This works because cgroup_migrate()
2039 * ensures that the dst_cset of the leader is the first on the
2040 * tset's dst_csets list.
2042 list_move_tail(&tsk
->cg_list
, &new_cset
->mg_tasks
);
2045 * We just gained a reference on old_cset by taking it from the
2046 * task. As trading it for new_cset is protected by cgroup_mutex,
2047 * we're safe to drop it here; it will be freed under RCU.
2049 set_bit(CGRP_RELEASABLE
, &old_cgrp
->flags
);
2050 put_css_set_locked(old_cset
, false);
2054 * cgroup_migrate_finish - cleanup after attach
2055 * @preloaded_csets: list of preloaded css_sets
2057 * Undo cgroup_migrate_add_src() and cgroup_migrate_prepare_dst(). See
2058 * those functions for details.
2060 static void cgroup_migrate_finish(struct list_head
*preloaded_csets
)
2062 struct css_set
*cset
, *tmp_cset
;
2064 lockdep_assert_held(&cgroup_mutex
);
2066 down_write(&css_set_rwsem
);
2067 list_for_each_entry_safe(cset
, tmp_cset
, preloaded_csets
, mg_preload_node
) {
2068 cset
->mg_src_cgrp
= NULL
;
2069 cset
->mg_dst_cset
= NULL
;
2070 list_del_init(&cset
->mg_preload_node
);
2071 put_css_set_locked(cset
, false);
2073 up_write(&css_set_rwsem
);
2077 * cgroup_migrate_add_src - add a migration source css_set
2078 * @src_cset: the source css_set to add
2079 * @dst_cgrp: the destination cgroup
2080 * @preloaded_csets: list of preloaded css_sets
2082 * Tasks belonging to @src_cset are about to be migrated to @dst_cgrp. Pin
2083 * @src_cset and add it to @preloaded_csets, which should later be cleaned
2084 * up by cgroup_migrate_finish().
2086 * This function may be called without holding threadgroup_lock even if the
2087 * target is a process. Threads may be created and destroyed but as long
2088 * as cgroup_mutex is not dropped, no new css_set can be put into play and
2089 * the preloaded css_sets are guaranteed to cover all migrations.
2091 static void cgroup_migrate_add_src(struct css_set
*src_cset
,
2092 struct cgroup
*dst_cgrp
,
2093 struct list_head
*preloaded_csets
)
2095 struct cgroup
*src_cgrp
;
2097 lockdep_assert_held(&cgroup_mutex
);
2098 lockdep_assert_held(&css_set_rwsem
);
2100 src_cgrp
= cset_cgroup_from_root(src_cset
, dst_cgrp
->root
);
2102 if (!list_empty(&src_cset
->mg_preload_node
))
2105 WARN_ON(src_cset
->mg_src_cgrp
);
2106 WARN_ON(!list_empty(&src_cset
->mg_tasks
));
2107 WARN_ON(!list_empty(&src_cset
->mg_node
));
2109 src_cset
->mg_src_cgrp
= src_cgrp
;
2110 get_css_set(src_cset
);
2111 list_add(&src_cset
->mg_preload_node
, preloaded_csets
);
2115 * cgroup_migrate_prepare_dst - prepare destination css_sets for migration
2116 * @dst_cgrp: the destination cgroup (may be %NULL)
2117 * @preloaded_csets: list of preloaded source css_sets
2119 * Tasks are about to be moved to @dst_cgrp and all the source css_sets
2120 * have been preloaded to @preloaded_csets. This function looks up and
2121 * pins all destination css_sets, links each to its source, and append them
2122 * to @preloaded_csets. If @dst_cgrp is %NULL, the destination of each
2123 * source css_set is assumed to be its cgroup on the default hierarchy.
2125 * This function must be called after cgroup_migrate_add_src() has been
2126 * called on each migration source css_set. After migration is performed
2127 * using cgroup_migrate(), cgroup_migrate_finish() must be called on
2130 static int cgroup_migrate_prepare_dst(struct cgroup
*dst_cgrp
,
2131 struct list_head
*preloaded_csets
)
2134 struct css_set
*src_cset
, *tmp_cset
;
2136 lockdep_assert_held(&cgroup_mutex
);
2139 * Except for the root, child_subsys_mask must be zero for a cgroup
2140 * with tasks so that child cgroups don't compete against tasks.
2142 if (dst_cgrp
&& cgroup_on_dfl(dst_cgrp
) && cgroup_parent(dst_cgrp
) &&
2143 dst_cgrp
->child_subsys_mask
)
2146 /* look up the dst cset for each src cset and link it to src */
2147 list_for_each_entry_safe(src_cset
, tmp_cset
, preloaded_csets
, mg_preload_node
) {
2148 struct css_set
*dst_cset
;
2150 dst_cset
= find_css_set(src_cset
,
2151 dst_cgrp
?: src_cset
->dfl_cgrp
);
2155 WARN_ON_ONCE(src_cset
->mg_dst_cset
|| dst_cset
->mg_dst_cset
);
2158 * If src cset equals dst, it's noop. Drop the src.
2159 * cgroup_migrate() will skip the cset too. Note that we
2160 * can't handle src == dst as some nodes are used by both.
2162 if (src_cset
== dst_cset
) {
2163 src_cset
->mg_src_cgrp
= NULL
;
2164 list_del_init(&src_cset
->mg_preload_node
);
2165 put_css_set(src_cset
, false);
2166 put_css_set(dst_cset
, false);
2170 src_cset
->mg_dst_cset
= dst_cset
;
2172 if (list_empty(&dst_cset
->mg_preload_node
))
2173 list_add(&dst_cset
->mg_preload_node
, &csets
);
2175 put_css_set(dst_cset
, false);
2178 list_splice_tail(&csets
, preloaded_csets
);
2181 cgroup_migrate_finish(&csets
);
2186 * cgroup_migrate - migrate a process or task to a cgroup
2187 * @cgrp: the destination cgroup
2188 * @leader: the leader of the process or the task to migrate
2189 * @threadgroup: whether @leader points to the whole process or a single task
2191 * Migrate a process or task denoted by @leader to @cgrp. If migrating a
2192 * process, the caller must be holding threadgroup_lock of @leader. The
2193 * caller is also responsible for invoking cgroup_migrate_add_src() and
2194 * cgroup_migrate_prepare_dst() on the targets before invoking this
2195 * function and following up with cgroup_migrate_finish().
2197 * As long as a controller's ->can_attach() doesn't fail, this function is
2198 * guaranteed to succeed. This means that, excluding ->can_attach()
2199 * failure, when migrating multiple targets, the success or failure can be
2200 * decided for all targets by invoking group_migrate_prepare_dst() before
2201 * actually starting migrating.
2203 static int cgroup_migrate(struct cgroup
*cgrp
, struct task_struct
*leader
,
2206 struct cgroup_taskset tset
= {
2207 .src_csets
= LIST_HEAD_INIT(tset
.src_csets
),
2208 .dst_csets
= LIST_HEAD_INIT(tset
.dst_csets
),
2209 .csets
= &tset
.src_csets
,
2211 struct cgroup_subsys_state
*css
, *failed_css
= NULL
;
2212 struct css_set
*cset
, *tmp_cset
;
2213 struct task_struct
*task
, *tmp_task
;
2217 * Prevent freeing of tasks while we take a snapshot. Tasks that are
2218 * already PF_EXITING could be freed from underneath us unless we
2219 * take an rcu_read_lock.
2221 down_write(&css_set_rwsem
);
2225 /* @task either already exited or can't exit until the end */
2226 if (task
->flags
& PF_EXITING
)
2229 /* leave @task alone if post_fork() hasn't linked it yet */
2230 if (list_empty(&task
->cg_list
))
2233 cset
= task_css_set(task
);
2234 if (!cset
->mg_src_cgrp
)
2238 * cgroup_taskset_first() must always return the leader.
2239 * Take care to avoid disturbing the ordering.
2241 list_move_tail(&task
->cg_list
, &cset
->mg_tasks
);
2242 if (list_empty(&cset
->mg_node
))
2243 list_add_tail(&cset
->mg_node
, &tset
.src_csets
);
2244 if (list_empty(&cset
->mg_dst_cset
->mg_node
))
2245 list_move_tail(&cset
->mg_dst_cset
->mg_node
,
2250 } while_each_thread(leader
, task
);
2252 up_write(&css_set_rwsem
);
2254 /* methods shouldn't be called if no task is actually migrating */
2255 if (list_empty(&tset
.src_csets
))
2258 /* check that we can legitimately attach to the cgroup */
2259 for_each_e_css(css
, i
, cgrp
) {
2260 if (css
->ss
->can_attach
) {
2261 ret
= css
->ss
->can_attach(css
, &tset
);
2264 goto out_cancel_attach
;
2270 * Now that we're guaranteed success, proceed to move all tasks to
2271 * the new cgroup. There are no failure cases after here, so this
2272 * is the commit point.
2274 down_write(&css_set_rwsem
);
2275 list_for_each_entry(cset
, &tset
.src_csets
, mg_node
) {
2276 list_for_each_entry_safe(task
, tmp_task
, &cset
->mg_tasks
, cg_list
)
2277 cgroup_task_migrate(cset
->mg_src_cgrp
, task
,
2280 up_write(&css_set_rwsem
);
2283 * Migration is committed, all target tasks are now on dst_csets.
2284 * Nothing is sensitive to fork() after this point. Notify
2285 * controllers that migration is complete.
2287 tset
.csets
= &tset
.dst_csets
;
2289 for_each_e_css(css
, i
, cgrp
)
2290 if (css
->ss
->attach
)
2291 css
->ss
->attach(css
, &tset
);
2294 goto out_release_tset
;
2297 for_each_e_css(css
, i
, cgrp
) {
2298 if (css
== failed_css
)
2300 if (css
->ss
->cancel_attach
)
2301 css
->ss
->cancel_attach(css
, &tset
);
2304 down_write(&css_set_rwsem
);
2305 list_splice_init(&tset
.dst_csets
, &tset
.src_csets
);
2306 list_for_each_entry_safe(cset
, tmp_cset
, &tset
.src_csets
, mg_node
) {
2307 list_splice_tail_init(&cset
->mg_tasks
, &cset
->tasks
);
2308 list_del_init(&cset
->mg_node
);
2310 up_write(&css_set_rwsem
);
2315 * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
2316 * @dst_cgrp: the cgroup to attach to
2317 * @leader: the task or the leader of the threadgroup to be attached
2318 * @threadgroup: attach the whole threadgroup?
2320 * Call holding cgroup_mutex and threadgroup_lock of @leader.
2322 static int cgroup_attach_task(struct cgroup
*dst_cgrp
,
2323 struct task_struct
*leader
, bool threadgroup
)
2325 LIST_HEAD(preloaded_csets
);
2326 struct task_struct
*task
;
2329 /* look up all src csets */
2330 down_read(&css_set_rwsem
);
2334 cgroup_migrate_add_src(task_css_set(task
), dst_cgrp
,
2338 } while_each_thread(leader
, task
);
2340 up_read(&css_set_rwsem
);
2342 /* prepare dst csets and commit */
2343 ret
= cgroup_migrate_prepare_dst(dst_cgrp
, &preloaded_csets
);
2345 ret
= cgroup_migrate(dst_cgrp
, leader
, threadgroup
);
2347 cgroup_migrate_finish(&preloaded_csets
);
2352 * Find the task_struct of the task to attach by vpid and pass it along to the
2353 * function to attach either it or all tasks in its threadgroup. Will lock
2354 * cgroup_mutex and threadgroup.
2356 static ssize_t
__cgroup_procs_write(struct kernfs_open_file
*of
, char *buf
,
2357 size_t nbytes
, loff_t off
, bool threadgroup
)
2359 struct task_struct
*tsk
;
2360 const struct cred
*cred
= current_cred(), *tcred
;
2361 struct cgroup
*cgrp
;
2365 if (kstrtoint(strstrip(buf
), 0, &pid
) || pid
< 0)
2368 cgrp
= cgroup_kn_lock_live(of
->kn
);
2375 tsk
= find_task_by_vpid(pid
);
2379 goto out_unlock_cgroup
;
2382 * even if we're attaching all tasks in the thread group, we
2383 * only need to check permissions on one of them.
2385 tcred
= __task_cred(tsk
);
2386 if (!uid_eq(cred
->euid
, GLOBAL_ROOT_UID
) &&
2387 !uid_eq(cred
->euid
, tcred
->uid
) &&
2388 !uid_eq(cred
->euid
, tcred
->suid
)) {
2391 goto out_unlock_cgroup
;
2397 tsk
= tsk
->group_leader
;
2400 * Workqueue threads may acquire PF_NO_SETAFFINITY and become
2401 * trapped in a cpuset, or RT worker may be born in a cgroup
2402 * with no rt_runtime allocated. Just say no.
2404 if (tsk
== kthreadd_task
|| (tsk
->flags
& PF_NO_SETAFFINITY
)) {
2407 goto out_unlock_cgroup
;
2410 get_task_struct(tsk
);
2413 threadgroup_lock(tsk
);
2415 if (!thread_group_leader(tsk
)) {
2417 * a race with de_thread from another thread's exec()
2418 * may strip us of our leadership, if this happens,
2419 * there is no choice but to throw this task away and
2420 * try again; this is
2421 * "double-double-toil-and-trouble-check locking".
2423 threadgroup_unlock(tsk
);
2424 put_task_struct(tsk
);
2425 goto retry_find_task
;
2429 ret
= cgroup_attach_task(cgrp
, tsk
, threadgroup
);
2431 threadgroup_unlock(tsk
);
2433 put_task_struct(tsk
);
2435 cgroup_kn_unlock(of
->kn
);
2436 return ret
?: nbytes
;
2440 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
2441 * @from: attach to all cgroups of a given task
2442 * @tsk: the task to be attached
2444 int cgroup_attach_task_all(struct task_struct
*from
, struct task_struct
*tsk
)
2446 struct cgroup_root
*root
;
2449 mutex_lock(&cgroup_mutex
);
2450 for_each_root(root
) {
2451 struct cgroup
*from_cgrp
;
2453 if (root
== &cgrp_dfl_root
)
2456 down_read(&css_set_rwsem
);
2457 from_cgrp
= task_cgroup_from_root(from
, root
);
2458 up_read(&css_set_rwsem
);
2460 retval
= cgroup_attach_task(from_cgrp
, tsk
, false);
2464 mutex_unlock(&cgroup_mutex
);
2468 EXPORT_SYMBOL_GPL(cgroup_attach_task_all
);
2470 static ssize_t
cgroup_tasks_write(struct kernfs_open_file
*of
,
2471 char *buf
, size_t nbytes
, loff_t off
)
2473 return __cgroup_procs_write(of
, buf
, nbytes
, off
, false);
2476 static ssize_t
cgroup_procs_write(struct kernfs_open_file
*of
,
2477 char *buf
, size_t nbytes
, loff_t off
)
2479 return __cgroup_procs_write(of
, buf
, nbytes
, off
, true);
2482 static ssize_t
cgroup_release_agent_write(struct kernfs_open_file
*of
,
2483 char *buf
, size_t nbytes
, loff_t off
)
2485 struct cgroup
*cgrp
;
2487 BUILD_BUG_ON(sizeof(cgrp
->root
->release_agent_path
) < PATH_MAX
);
2489 cgrp
= cgroup_kn_lock_live(of
->kn
);
2492 spin_lock(&release_agent_path_lock
);
2493 strlcpy(cgrp
->root
->release_agent_path
, strstrip(buf
),
2494 sizeof(cgrp
->root
->release_agent_path
));
2495 spin_unlock(&release_agent_path_lock
);
2496 cgroup_kn_unlock(of
->kn
);
2500 static int cgroup_release_agent_show(struct seq_file
*seq
, void *v
)
2502 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2504 spin_lock(&release_agent_path_lock
);
2505 seq_puts(seq
, cgrp
->root
->release_agent_path
);
2506 spin_unlock(&release_agent_path_lock
);
2507 seq_putc(seq
, '\n');
2511 static int cgroup_sane_behavior_show(struct seq_file
*seq
, void *v
)
2513 seq_puts(seq
, "0\n");
2517 static void cgroup_print_ss_mask(struct seq_file
*seq
, unsigned int ss_mask
)
2519 struct cgroup_subsys
*ss
;
2520 bool printed
= false;
2523 for_each_subsys(ss
, ssid
) {
2524 if (ss_mask
& (1 << ssid
)) {
2527 seq_printf(seq
, "%s", ss
->name
);
2532 seq_putc(seq
, '\n');
2535 /* show controllers which are currently attached to the default hierarchy */
2536 static int cgroup_root_controllers_show(struct seq_file
*seq
, void *v
)
2538 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2540 cgroup_print_ss_mask(seq
, cgrp
->root
->subsys_mask
&
2541 ~cgrp_dfl_root_inhibit_ss_mask
);
2545 /* show controllers which are enabled from the parent */
2546 static int cgroup_controllers_show(struct seq_file
*seq
, void *v
)
2548 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2550 cgroup_print_ss_mask(seq
, cgroup_parent(cgrp
)->subtree_control
);
2554 /* show controllers which are enabled for a given cgroup's children */
2555 static int cgroup_subtree_control_show(struct seq_file
*seq
, void *v
)
2557 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2559 cgroup_print_ss_mask(seq
, cgrp
->subtree_control
);
2564 * cgroup_update_dfl_csses - update css assoc of a subtree in default hierarchy
2565 * @cgrp: root of the subtree to update csses for
2567 * @cgrp's child_subsys_mask has changed and its subtree's (self excluded)
2568 * css associations need to be updated accordingly. This function looks up
2569 * all css_sets which are attached to the subtree, creates the matching
2570 * updated css_sets and migrates the tasks to the new ones.
2572 static int cgroup_update_dfl_csses(struct cgroup
*cgrp
)
2574 LIST_HEAD(preloaded_csets
);
2575 struct cgroup_subsys_state
*css
;
2576 struct css_set
*src_cset
;
2579 lockdep_assert_held(&cgroup_mutex
);
2581 /* look up all csses currently attached to @cgrp's subtree */
2582 down_read(&css_set_rwsem
);
2583 css_for_each_descendant_pre(css
, cgroup_css(cgrp
, NULL
)) {
2584 struct cgrp_cset_link
*link
;
2586 /* self is not affected by child_subsys_mask change */
2587 if (css
->cgroup
== cgrp
)
2590 list_for_each_entry(link
, &css
->cgroup
->cset_links
, cset_link
)
2591 cgroup_migrate_add_src(link
->cset
, cgrp
,
2594 up_read(&css_set_rwsem
);
2596 /* NULL dst indicates self on default hierarchy */
2597 ret
= cgroup_migrate_prepare_dst(NULL
, &preloaded_csets
);
2601 list_for_each_entry(src_cset
, &preloaded_csets
, mg_preload_node
) {
2602 struct task_struct
*last_task
= NULL
, *task
;
2604 /* src_csets precede dst_csets, break on the first dst_cset */
2605 if (!src_cset
->mg_src_cgrp
)
2609 * All tasks in src_cset need to be migrated to the
2610 * matching dst_cset. Empty it process by process. We
2611 * walk tasks but migrate processes. The leader might even
2612 * belong to a different cset but such src_cset would also
2613 * be among the target src_csets because the default
2614 * hierarchy enforces per-process membership.
2617 down_read(&css_set_rwsem
);
2618 task
= list_first_entry_or_null(&src_cset
->tasks
,
2619 struct task_struct
, cg_list
);
2621 task
= task
->group_leader
;
2622 WARN_ON_ONCE(!task_css_set(task
)->mg_src_cgrp
);
2623 get_task_struct(task
);
2625 up_read(&css_set_rwsem
);
2630 /* guard against possible infinite loop */
2631 if (WARN(last_task
== task
,
2632 "cgroup: update_dfl_csses failed to make progress, aborting in inconsistent state\n"))
2636 threadgroup_lock(task
);
2637 /* raced against de_thread() from another thread? */
2638 if (!thread_group_leader(task
)) {
2639 threadgroup_unlock(task
);
2640 put_task_struct(task
);
2644 ret
= cgroup_migrate(src_cset
->dfl_cgrp
, task
, true);
2646 threadgroup_unlock(task
);
2647 put_task_struct(task
);
2649 if (WARN(ret
, "cgroup: failed to update controllers for the default hierarchy (%d), further operations may crash or hang\n", ret
))
2655 cgroup_migrate_finish(&preloaded_csets
);
2659 /* change the enabled child controllers for a cgroup in the default hierarchy */
2660 static ssize_t
cgroup_subtree_control_write(struct kernfs_open_file
*of
,
2661 char *buf
, size_t nbytes
,
2664 unsigned int enable
= 0, disable
= 0;
2665 unsigned int css_enable
, css_disable
, old_ctrl
, new_ctrl
;
2666 struct cgroup
*cgrp
, *child
;
2667 struct cgroup_subsys
*ss
;
2672 * Parse input - space separated list of subsystem names prefixed
2673 * with either + or -.
2675 buf
= strstrip(buf
);
2676 while ((tok
= strsep(&buf
, " "))) {
2679 for_each_subsys(ss
, ssid
) {
2680 if (ss
->disabled
|| strcmp(tok
+ 1, ss
->name
) ||
2681 ((1 << ss
->id
) & cgrp_dfl_root_inhibit_ss_mask
))
2685 enable
|= 1 << ssid
;
2686 disable
&= ~(1 << ssid
);
2687 } else if (*tok
== '-') {
2688 disable
|= 1 << ssid
;
2689 enable
&= ~(1 << ssid
);
2695 if (ssid
== CGROUP_SUBSYS_COUNT
)
2699 cgrp
= cgroup_kn_lock_live(of
->kn
);
2703 for_each_subsys(ss
, ssid
) {
2704 if (enable
& (1 << ssid
)) {
2705 if (cgrp
->subtree_control
& (1 << ssid
)) {
2706 enable
&= ~(1 << ssid
);
2710 /* unavailable or not enabled on the parent? */
2711 if (!(cgrp_dfl_root
.subsys_mask
& (1 << ssid
)) ||
2712 (cgroup_parent(cgrp
) &&
2713 !(cgroup_parent(cgrp
)->subtree_control
& (1 << ssid
)))) {
2719 * @ss is already enabled through dependency and
2720 * we'll just make it visible. Skip draining.
2722 if (cgrp
->child_subsys_mask
& (1 << ssid
))
2726 * Because css offlining is asynchronous, userland
2727 * might try to re-enable the same controller while
2728 * the previous instance is still around. In such
2729 * cases, wait till it's gone using offline_waitq.
2731 cgroup_for_each_live_child(child
, cgrp
) {
2734 if (!cgroup_css(child
, ss
))
2738 prepare_to_wait(&child
->offline_waitq
, &wait
,
2739 TASK_UNINTERRUPTIBLE
);
2740 cgroup_kn_unlock(of
->kn
);
2742 finish_wait(&child
->offline_waitq
, &wait
);
2745 return restart_syscall();
2747 } else if (disable
& (1 << ssid
)) {
2748 if (!(cgrp
->subtree_control
& (1 << ssid
))) {
2749 disable
&= ~(1 << ssid
);
2753 /* a child has it enabled? */
2754 cgroup_for_each_live_child(child
, cgrp
) {
2755 if (child
->subtree_control
& (1 << ssid
)) {
2763 if (!enable
&& !disable
) {
2769 * Except for the root, subtree_control must be zero for a cgroup
2770 * with tasks so that child cgroups don't compete against tasks.
2772 if (enable
&& cgroup_parent(cgrp
) && !list_empty(&cgrp
->cset_links
)) {
2778 * Update subsys masks and calculate what needs to be done. More
2779 * subsystems than specified may need to be enabled or disabled
2780 * depending on subsystem dependencies.
2782 cgrp
->subtree_control
|= enable
;
2783 cgrp
->subtree_control
&= ~disable
;
2785 old_ctrl
= cgrp
->child_subsys_mask
;
2786 cgroup_refresh_child_subsys_mask(cgrp
);
2787 new_ctrl
= cgrp
->child_subsys_mask
;
2789 css_enable
= ~old_ctrl
& new_ctrl
;
2790 css_disable
= old_ctrl
& ~new_ctrl
;
2791 enable
|= css_enable
;
2792 disable
|= css_disable
;
2795 * Create new csses or make the existing ones visible. A css is
2796 * created invisible if it's being implicitly enabled through
2797 * dependency. An invisible css is made visible when the userland
2798 * explicitly enables it.
2800 for_each_subsys(ss
, ssid
) {
2801 if (!(enable
& (1 << ssid
)))
2804 cgroup_for_each_live_child(child
, cgrp
) {
2805 if (css_enable
& (1 << ssid
))
2806 ret
= create_css(child
, ss
,
2807 cgrp
->subtree_control
& (1 << ssid
));
2809 ret
= cgroup_populate_dir(child
, 1 << ssid
);
2816 * At this point, cgroup_e_css() results reflect the new csses
2817 * making the following cgroup_update_dfl_csses() properly update
2818 * css associations of all tasks in the subtree.
2820 ret
= cgroup_update_dfl_csses(cgrp
);
2825 * All tasks are migrated out of disabled csses. Kill or hide
2826 * them. A css is hidden when the userland requests it to be
2827 * disabled while other subsystems are still depending on it. The
2828 * css must not actively control resources and be in the vanilla
2829 * state if it's made visible again later. Controllers which may
2830 * be depended upon should provide ->css_reset() for this purpose.
2832 for_each_subsys(ss
, ssid
) {
2833 if (!(disable
& (1 << ssid
)))
2836 cgroup_for_each_live_child(child
, cgrp
) {
2837 struct cgroup_subsys_state
*css
= cgroup_css(child
, ss
);
2839 if (css_disable
& (1 << ssid
)) {
2842 cgroup_clear_dir(child
, 1 << ssid
);
2849 kernfs_activate(cgrp
->kn
);
2852 cgroup_kn_unlock(of
->kn
);
2853 return ret
?: nbytes
;
2856 cgrp
->subtree_control
&= ~enable
;
2857 cgrp
->subtree_control
|= disable
;
2858 cgroup_refresh_child_subsys_mask(cgrp
);
2860 for_each_subsys(ss
, ssid
) {
2861 if (!(enable
& (1 << ssid
)))
2864 cgroup_for_each_live_child(child
, cgrp
) {
2865 struct cgroup_subsys_state
*css
= cgroup_css(child
, ss
);
2870 if (css_enable
& (1 << ssid
))
2873 cgroup_clear_dir(child
, 1 << ssid
);
2879 static int cgroup_populated_show(struct seq_file
*seq
, void *v
)
2881 seq_printf(seq
, "%d\n", (bool)seq_css(seq
)->cgroup
->populated_cnt
);
2885 static ssize_t
cgroup_file_write(struct kernfs_open_file
*of
, char *buf
,
2886 size_t nbytes
, loff_t off
)
2888 struct cgroup
*cgrp
= of
->kn
->parent
->priv
;
2889 struct cftype
*cft
= of
->kn
->priv
;
2890 struct cgroup_subsys_state
*css
;
2894 return cft
->write(of
, buf
, nbytes
, off
);
2897 * kernfs guarantees that a file isn't deleted with operations in
2898 * flight, which means that the matching css is and stays alive and
2899 * doesn't need to be pinned. The RCU locking is not necessary
2900 * either. It's just for the convenience of using cgroup_css().
2903 css
= cgroup_css(cgrp
, cft
->ss
);
2906 if (cft
->write_u64
) {
2907 unsigned long long v
;
2908 ret
= kstrtoull(buf
, 0, &v
);
2910 ret
= cft
->write_u64(css
, cft
, v
);
2911 } else if (cft
->write_s64
) {
2913 ret
= kstrtoll(buf
, 0, &v
);
2915 ret
= cft
->write_s64(css
, cft
, v
);
2920 return ret
?: nbytes
;
2923 static void *cgroup_seqfile_start(struct seq_file
*seq
, loff_t
*ppos
)
2925 return seq_cft(seq
)->seq_start(seq
, ppos
);
2928 static void *cgroup_seqfile_next(struct seq_file
*seq
, void *v
, loff_t
*ppos
)
2930 return seq_cft(seq
)->seq_next(seq
, v
, ppos
);
2933 static void cgroup_seqfile_stop(struct seq_file
*seq
, void *v
)
2935 seq_cft(seq
)->seq_stop(seq
, v
);
2938 static int cgroup_seqfile_show(struct seq_file
*m
, void *arg
)
2940 struct cftype
*cft
= seq_cft(m
);
2941 struct cgroup_subsys_state
*css
= seq_css(m
);
2944 return cft
->seq_show(m
, arg
);
2947 seq_printf(m
, "%llu\n", cft
->read_u64(css
, cft
));
2948 else if (cft
->read_s64
)
2949 seq_printf(m
, "%lld\n", cft
->read_s64(css
, cft
));
2955 static struct kernfs_ops cgroup_kf_single_ops
= {
2956 .atomic_write_len
= PAGE_SIZE
,
2957 .write
= cgroup_file_write
,
2958 .seq_show
= cgroup_seqfile_show
,
2961 static struct kernfs_ops cgroup_kf_ops
= {
2962 .atomic_write_len
= PAGE_SIZE
,
2963 .write
= cgroup_file_write
,
2964 .seq_start
= cgroup_seqfile_start
,
2965 .seq_next
= cgroup_seqfile_next
,
2966 .seq_stop
= cgroup_seqfile_stop
,
2967 .seq_show
= cgroup_seqfile_show
,
2971 * cgroup_rename - Only allow simple rename of directories in place.
2973 static int cgroup_rename(struct kernfs_node
*kn
, struct kernfs_node
*new_parent
,
2974 const char *new_name_str
)
2976 struct cgroup
*cgrp
= kn
->priv
;
2979 if (kernfs_type(kn
) != KERNFS_DIR
)
2981 if (kn
->parent
!= new_parent
)
2985 * This isn't a proper migration and its usefulness is very
2986 * limited. Disallow on the default hierarchy.
2988 if (cgroup_on_dfl(cgrp
))
2992 * We're gonna grab cgroup_mutex which nests outside kernfs
2993 * active_ref. kernfs_rename() doesn't require active_ref
2994 * protection. Break them before grabbing cgroup_mutex.
2996 kernfs_break_active_protection(new_parent
);
2997 kernfs_break_active_protection(kn
);
2999 mutex_lock(&cgroup_mutex
);
3001 ret
= kernfs_rename(kn
, new_parent
, new_name_str
);
3003 mutex_unlock(&cgroup_mutex
);
3005 kernfs_unbreak_active_protection(kn
);
3006 kernfs_unbreak_active_protection(new_parent
);
3010 /* set uid and gid of cgroup dirs and files to that of the creator */
3011 static int cgroup_kn_set_ugid(struct kernfs_node
*kn
)
3013 struct iattr iattr
= { .ia_valid
= ATTR_UID
| ATTR_GID
,
3014 .ia_uid
= current_fsuid(),
3015 .ia_gid
= current_fsgid(), };
3017 if (uid_eq(iattr
.ia_uid
, GLOBAL_ROOT_UID
) &&
3018 gid_eq(iattr
.ia_gid
, GLOBAL_ROOT_GID
))
3021 return kernfs_setattr(kn
, &iattr
);
3024 static int cgroup_add_file(struct cgroup
*cgrp
, struct cftype
*cft
)
3026 char name
[CGROUP_FILE_NAME_MAX
];
3027 struct kernfs_node
*kn
;
3028 struct lock_class_key
*key
= NULL
;
3031 #ifdef CONFIG_DEBUG_LOCK_ALLOC
3032 key
= &cft
->lockdep_key
;
3034 kn
= __kernfs_create_file(cgrp
->kn
, cgroup_file_name(cgrp
, cft
, name
),
3035 cgroup_file_mode(cft
), 0, cft
->kf_ops
, cft
,
3040 ret
= cgroup_kn_set_ugid(kn
);
3046 if (cft
->seq_show
== cgroup_populated_show
)
3047 cgrp
->populated_kn
= kn
;
3052 * cgroup_addrm_files - add or remove files to a cgroup directory
3053 * @cgrp: the target cgroup
3054 * @cfts: array of cftypes to be added
3055 * @is_add: whether to add or remove
3057 * Depending on @is_add, add or remove files defined by @cfts on @cgrp.
3058 * For removals, this function never fails. If addition fails, this
3059 * function doesn't remove files already added. The caller is responsible
3062 static int cgroup_addrm_files(struct cgroup
*cgrp
, struct cftype cfts
[],
3068 lockdep_assert_held(&cgroup_mutex
);
3070 for (cft
= cfts
; cft
->name
[0] != '\0'; cft
++) {
3071 /* does cft->flags tell us to skip this file on @cgrp? */
3072 if ((cft
->flags
& __CFTYPE_ONLY_ON_DFL
) && !cgroup_on_dfl(cgrp
))
3074 if ((cft
->flags
& __CFTYPE_NOT_ON_DFL
) && cgroup_on_dfl(cgrp
))
3076 if ((cft
->flags
& CFTYPE_NOT_ON_ROOT
) && !cgroup_parent(cgrp
))
3078 if ((cft
->flags
& CFTYPE_ONLY_ON_ROOT
) && cgroup_parent(cgrp
))
3082 ret
= cgroup_add_file(cgrp
, cft
);
3084 pr_warn("%s: failed to add %s, err=%d\n",
3085 __func__
, cft
->name
, ret
);
3089 cgroup_rm_file(cgrp
, cft
);
3095 static int cgroup_apply_cftypes(struct cftype
*cfts
, bool is_add
)
3098 struct cgroup_subsys
*ss
= cfts
[0].ss
;
3099 struct cgroup
*root
= &ss
->root
->cgrp
;
3100 struct cgroup_subsys_state
*css
;
3103 lockdep_assert_held(&cgroup_mutex
);
3105 /* add/rm files for all cgroups created before */
3106 css_for_each_descendant_pre(css
, cgroup_css(root
, ss
)) {
3107 struct cgroup
*cgrp
= css
->cgroup
;
3109 if (cgroup_is_dead(cgrp
))
3112 ret
= cgroup_addrm_files(cgrp
, cfts
, is_add
);
3118 kernfs_activate(root
->kn
);
3122 static void cgroup_exit_cftypes(struct cftype
*cfts
)
3126 for (cft
= cfts
; cft
->name
[0] != '\0'; cft
++) {
3127 /* free copy for custom atomic_write_len, see init_cftypes() */
3128 if (cft
->max_write_len
&& cft
->max_write_len
!= PAGE_SIZE
)
3133 /* revert flags set by cgroup core while adding @cfts */
3134 cft
->flags
&= ~(__CFTYPE_ONLY_ON_DFL
| __CFTYPE_NOT_ON_DFL
);
3138 static int cgroup_init_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3142 for (cft
= cfts
; cft
->name
[0] != '\0'; cft
++) {
3143 struct kernfs_ops
*kf_ops
;
3145 WARN_ON(cft
->ss
|| cft
->kf_ops
);
3148 kf_ops
= &cgroup_kf_ops
;
3150 kf_ops
= &cgroup_kf_single_ops
;
3153 * Ugh... if @cft wants a custom max_write_len, we need to
3154 * make a copy of kf_ops to set its atomic_write_len.
3156 if (cft
->max_write_len
&& cft
->max_write_len
!= PAGE_SIZE
) {
3157 kf_ops
= kmemdup(kf_ops
, sizeof(*kf_ops
), GFP_KERNEL
);
3159 cgroup_exit_cftypes(cfts
);
3162 kf_ops
->atomic_write_len
= cft
->max_write_len
;
3165 cft
->kf_ops
= kf_ops
;
3172 static int cgroup_rm_cftypes_locked(struct cftype
*cfts
)
3174 lockdep_assert_held(&cgroup_mutex
);
3176 if (!cfts
|| !cfts
[0].ss
)
3179 list_del(&cfts
->node
);
3180 cgroup_apply_cftypes(cfts
, false);
3181 cgroup_exit_cftypes(cfts
);
3186 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
3187 * @cfts: zero-length name terminated array of cftypes
3189 * Unregister @cfts. Files described by @cfts are removed from all
3190 * existing cgroups and all future cgroups won't have them either. This
3191 * function can be called anytime whether @cfts' subsys is attached or not.
3193 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
3196 int cgroup_rm_cftypes(struct cftype
*cfts
)
3200 mutex_lock(&cgroup_mutex
);
3201 ret
= cgroup_rm_cftypes_locked(cfts
);
3202 mutex_unlock(&cgroup_mutex
);
3207 * cgroup_add_cftypes - add an array of cftypes to a subsystem
3208 * @ss: target cgroup subsystem
3209 * @cfts: zero-length name terminated array of cftypes
3211 * Register @cfts to @ss. Files described by @cfts are created for all
3212 * existing cgroups to which @ss is attached and all future cgroups will
3213 * have them too. This function can be called anytime whether @ss is
3216 * Returns 0 on successful registration, -errno on failure. Note that this
3217 * function currently returns 0 as long as @cfts registration is successful
3218 * even if some file creation attempts on existing cgroups fail.
3220 static int cgroup_add_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3227 if (!cfts
|| cfts
[0].name
[0] == '\0')
3230 ret
= cgroup_init_cftypes(ss
, cfts
);
3234 mutex_lock(&cgroup_mutex
);
3236 list_add_tail(&cfts
->node
, &ss
->cfts
);
3237 ret
= cgroup_apply_cftypes(cfts
, true);
3239 cgroup_rm_cftypes_locked(cfts
);
3241 mutex_unlock(&cgroup_mutex
);
3246 * cgroup_add_dfl_cftypes - add an array of cftypes for default hierarchy
3247 * @ss: target cgroup subsystem
3248 * @cfts: zero-length name terminated array of cftypes
3250 * Similar to cgroup_add_cftypes() but the added files are only used for
3251 * the default hierarchy.
3253 int cgroup_add_dfl_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3257 for (cft
= cfts
; cft
&& cft
->name
[0] != '\0'; cft
++)
3258 cft
->flags
|= __CFTYPE_ONLY_ON_DFL
;
3259 return cgroup_add_cftypes(ss
, cfts
);
3263 * cgroup_add_legacy_cftypes - add an array of cftypes for legacy hierarchies
3264 * @ss: target cgroup subsystem
3265 * @cfts: zero-length name terminated array of cftypes
3267 * Similar to cgroup_add_cftypes() but the added files are only used for
3268 * the legacy hierarchies.
3270 int cgroup_add_legacy_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3274 for (cft
= cfts
; cft
&& cft
->name
[0] != '\0'; cft
++)
3275 cft
->flags
|= __CFTYPE_NOT_ON_DFL
;
3276 return cgroup_add_cftypes(ss
, cfts
);
3280 * cgroup_task_count - count the number of tasks in a cgroup.
3281 * @cgrp: the cgroup in question
3283 * Return the number of tasks in the cgroup.
3285 static int cgroup_task_count(const struct cgroup
*cgrp
)
3288 struct cgrp_cset_link
*link
;
3290 down_read(&css_set_rwsem
);
3291 list_for_each_entry(link
, &cgrp
->cset_links
, cset_link
)
3292 count
+= atomic_read(&link
->cset
->refcount
);
3293 up_read(&css_set_rwsem
);
3298 * css_next_child - find the next child of a given css
3299 * @pos: the current position (%NULL to initiate traversal)
3300 * @parent: css whose children to walk
3302 * This function returns the next child of @parent and should be called
3303 * under either cgroup_mutex or RCU read lock. The only requirement is
3304 * that @parent and @pos are accessible. The next sibling is guaranteed to
3305 * be returned regardless of their states.
3307 * If a subsystem synchronizes ->css_online() and the start of iteration, a
3308 * css which finished ->css_online() is guaranteed to be visible in the
3309 * future iterations and will stay visible until the last reference is put.
3310 * A css which hasn't finished ->css_online() or already finished
3311 * ->css_offline() may show up during traversal. It's each subsystem's
3312 * responsibility to synchronize against on/offlining.
3314 struct cgroup_subsys_state
*css_next_child(struct cgroup_subsys_state
*pos
,
3315 struct cgroup_subsys_state
*parent
)
3317 struct cgroup_subsys_state
*next
;
3319 cgroup_assert_mutex_or_rcu_locked();
3322 * @pos could already have been unlinked from the sibling list.
3323 * Once a cgroup is removed, its ->sibling.next is no longer
3324 * updated when its next sibling changes. CSS_RELEASED is set when
3325 * @pos is taken off list, at which time its next pointer is valid,
3326 * and, as releases are serialized, the one pointed to by the next
3327 * pointer is guaranteed to not have started release yet. This
3328 * implies that if we observe !CSS_RELEASED on @pos in this RCU
3329 * critical section, the one pointed to by its next pointer is
3330 * guaranteed to not have finished its RCU grace period even if we
3331 * have dropped rcu_read_lock() inbetween iterations.
3333 * If @pos has CSS_RELEASED set, its next pointer can't be
3334 * dereferenced; however, as each css is given a monotonically
3335 * increasing unique serial number and always appended to the
3336 * sibling list, the next one can be found by walking the parent's
3337 * children until the first css with higher serial number than
3338 * @pos's. While this path can be slower, it happens iff iteration
3339 * races against release and the race window is very small.
3342 next
= list_entry_rcu(parent
->children
.next
, struct cgroup_subsys_state
, sibling
);
3343 } else if (likely(!(pos
->flags
& CSS_RELEASED
))) {
3344 next
= list_entry_rcu(pos
->sibling
.next
, struct cgroup_subsys_state
, sibling
);
3346 list_for_each_entry_rcu(next
, &parent
->children
, sibling
)
3347 if (next
->serial_nr
> pos
->serial_nr
)
3352 * @next, if not pointing to the head, can be dereferenced and is
3355 if (&next
->sibling
!= &parent
->children
)
3361 * css_next_descendant_pre - find the next descendant for pre-order walk
3362 * @pos: the current position (%NULL to initiate traversal)
3363 * @root: css whose descendants to walk
3365 * To be used by css_for_each_descendant_pre(). Find the next descendant
3366 * to visit for pre-order traversal of @root's descendants. @root is
3367 * included in the iteration and the first node to be visited.
3369 * While this function requires cgroup_mutex or RCU read locking, it
3370 * doesn't require the whole traversal to be contained in a single critical
3371 * section. This function will return the correct next descendant as long
3372 * as both @pos and @root are accessible and @pos is a descendant of @root.
3374 * If a subsystem synchronizes ->css_online() and the start of iteration, a
3375 * css which finished ->css_online() is guaranteed to be visible in the
3376 * future iterations and will stay visible until the last reference is put.
3377 * A css which hasn't finished ->css_online() or already finished
3378 * ->css_offline() may show up during traversal. It's each subsystem's
3379 * responsibility to synchronize against on/offlining.
3381 struct cgroup_subsys_state
*
3382 css_next_descendant_pre(struct cgroup_subsys_state
*pos
,
3383 struct cgroup_subsys_state
*root
)
3385 struct cgroup_subsys_state
*next
;
3387 cgroup_assert_mutex_or_rcu_locked();
3389 /* if first iteration, visit @root */
3393 /* visit the first child if exists */
3394 next
= css_next_child(NULL
, pos
);
3398 /* no child, visit my or the closest ancestor's next sibling */
3399 while (pos
!= root
) {
3400 next
= css_next_child(pos
, pos
->parent
);
3410 * css_rightmost_descendant - return the rightmost descendant of a css
3411 * @pos: css of interest
3413 * Return the rightmost descendant of @pos. If there's no descendant, @pos
3414 * is returned. This can be used during pre-order traversal to skip
3417 * While this function requires cgroup_mutex or RCU read locking, it
3418 * doesn't require the whole traversal to be contained in a single critical
3419 * section. This function will return the correct rightmost descendant as
3420 * long as @pos is accessible.
3422 struct cgroup_subsys_state
*
3423 css_rightmost_descendant(struct cgroup_subsys_state
*pos
)
3425 struct cgroup_subsys_state
*last
, *tmp
;
3427 cgroup_assert_mutex_or_rcu_locked();
3431 /* ->prev isn't RCU safe, walk ->next till the end */
3433 css_for_each_child(tmp
, last
)
3440 static struct cgroup_subsys_state
*
3441 css_leftmost_descendant(struct cgroup_subsys_state
*pos
)
3443 struct cgroup_subsys_state
*last
;
3447 pos
= css_next_child(NULL
, pos
);
3454 * css_next_descendant_post - find the next descendant for post-order walk
3455 * @pos: the current position (%NULL to initiate traversal)
3456 * @root: css whose descendants to walk
3458 * To be used by css_for_each_descendant_post(). Find the next descendant
3459 * to visit for post-order traversal of @root's descendants. @root is
3460 * included in the iteration and the last node to be visited.
3462 * While this function requires cgroup_mutex or RCU read locking, it
3463 * doesn't require the whole traversal to be contained in a single critical
3464 * section. This function will return the correct next descendant as long
3465 * as both @pos and @cgroup are accessible and @pos is a descendant of
3468 * If a subsystem synchronizes ->css_online() and the start of iteration, a
3469 * css which finished ->css_online() is guaranteed to be visible in the
3470 * future iterations and will stay visible until the last reference is put.
3471 * A css which hasn't finished ->css_online() or already finished
3472 * ->css_offline() may show up during traversal. It's each subsystem's
3473 * responsibility to synchronize against on/offlining.
3475 struct cgroup_subsys_state
*
3476 css_next_descendant_post(struct cgroup_subsys_state
*pos
,
3477 struct cgroup_subsys_state
*root
)
3479 struct cgroup_subsys_state
*next
;
3481 cgroup_assert_mutex_or_rcu_locked();
3483 /* if first iteration, visit leftmost descendant which may be @root */
3485 return css_leftmost_descendant(root
);
3487 /* if we visited @root, we're done */
3491 /* if there's an unvisited sibling, visit its leftmost descendant */
3492 next
= css_next_child(pos
, pos
->parent
);
3494 return css_leftmost_descendant(next
);
3496 /* no sibling left, visit parent */
3501 * css_has_online_children - does a css have online children
3502 * @css: the target css
3504 * Returns %true if @css has any online children; otherwise, %false. This
3505 * function can be called from any context but the caller is responsible
3506 * for synchronizing against on/offlining as necessary.
3508 bool css_has_online_children(struct cgroup_subsys_state
*css
)
3510 struct cgroup_subsys_state
*child
;
3514 css_for_each_child(child
, css
) {
3515 if (child
->flags
& CSS_ONLINE
) {
3525 * css_advance_task_iter - advance a task itererator to the next css_set
3526 * @it: the iterator to advance
3528 * Advance @it to the next css_set to walk.
3530 static void css_advance_task_iter(struct css_task_iter
*it
)
3532 struct list_head
*l
= it
->cset_pos
;
3533 struct cgrp_cset_link
*link
;
3534 struct css_set
*cset
;
3536 /* Advance to the next non-empty css_set */
3539 if (l
== it
->cset_head
) {
3540 it
->cset_pos
= NULL
;
3545 cset
= container_of(l
, struct css_set
,
3546 e_cset_node
[it
->ss
->id
]);
3548 link
= list_entry(l
, struct cgrp_cset_link
, cset_link
);
3551 } while (list_empty(&cset
->tasks
) && list_empty(&cset
->mg_tasks
));
3555 if (!list_empty(&cset
->tasks
))
3556 it
->task_pos
= cset
->tasks
.next
;
3558 it
->task_pos
= cset
->mg_tasks
.next
;
3560 it
->tasks_head
= &cset
->tasks
;
3561 it
->mg_tasks_head
= &cset
->mg_tasks
;
3565 * css_task_iter_start - initiate task iteration
3566 * @css: the css to walk tasks of
3567 * @it: the task iterator to use
3569 * Initiate iteration through the tasks of @css. The caller can call
3570 * css_task_iter_next() to walk through the tasks until the function
3571 * returns NULL. On completion of iteration, css_task_iter_end() must be
3574 * Note that this function acquires a lock which is released when the
3575 * iteration finishes. The caller can't sleep while iteration is in
3578 void css_task_iter_start(struct cgroup_subsys_state
*css
,
3579 struct css_task_iter
*it
)
3580 __acquires(css_set_rwsem
)
3582 /* no one should try to iterate before mounting cgroups */
3583 WARN_ON_ONCE(!use_task_css_set_links
);
3585 down_read(&css_set_rwsem
);
3590 it
->cset_pos
= &css
->cgroup
->e_csets
[css
->ss
->id
];
3592 it
->cset_pos
= &css
->cgroup
->cset_links
;
3594 it
->cset_head
= it
->cset_pos
;
3596 css_advance_task_iter(it
);
3600 * css_task_iter_next - return the next task for the iterator
3601 * @it: the task iterator being iterated
3603 * The "next" function for task iteration. @it should have been
3604 * initialized via css_task_iter_start(). Returns NULL when the iteration
3607 struct task_struct
*css_task_iter_next(struct css_task_iter
*it
)
3609 struct task_struct
*res
;
3610 struct list_head
*l
= it
->task_pos
;
3612 /* If the iterator cg is NULL, we have no tasks */
3615 res
= list_entry(l
, struct task_struct
, cg_list
);
3618 * Advance iterator to find next entry. cset->tasks is consumed
3619 * first and then ->mg_tasks. After ->mg_tasks, we move onto the
3624 if (l
== it
->tasks_head
)
3625 l
= it
->mg_tasks_head
->next
;
3627 if (l
== it
->mg_tasks_head
)
3628 css_advance_task_iter(it
);
3636 * css_task_iter_end - finish task iteration
3637 * @it: the task iterator to finish
3639 * Finish task iteration started by css_task_iter_start().
3641 void css_task_iter_end(struct css_task_iter
*it
)
3642 __releases(css_set_rwsem
)
3644 up_read(&css_set_rwsem
);
3648 * cgroup_trasnsfer_tasks - move tasks from one cgroup to another
3649 * @to: cgroup to which the tasks will be moved
3650 * @from: cgroup in which the tasks currently reside
3652 * Locking rules between cgroup_post_fork() and the migration path
3653 * guarantee that, if a task is forking while being migrated, the new child
3654 * is guaranteed to be either visible in the source cgroup after the
3655 * parent's migration is complete or put into the target cgroup. No task
3656 * can slip out of migration through forking.
3658 int cgroup_transfer_tasks(struct cgroup
*to
, struct cgroup
*from
)
3660 LIST_HEAD(preloaded_csets
);
3661 struct cgrp_cset_link
*link
;
3662 struct css_task_iter it
;
3663 struct task_struct
*task
;
3666 mutex_lock(&cgroup_mutex
);
3668 /* all tasks in @from are being moved, all csets are source */
3669 down_read(&css_set_rwsem
);
3670 list_for_each_entry(link
, &from
->cset_links
, cset_link
)
3671 cgroup_migrate_add_src(link
->cset
, to
, &preloaded_csets
);
3672 up_read(&css_set_rwsem
);
3674 ret
= cgroup_migrate_prepare_dst(to
, &preloaded_csets
);
3679 * Migrate tasks one-by-one until @form is empty. This fails iff
3680 * ->can_attach() fails.
3683 css_task_iter_start(&from
->self
, &it
);
3684 task
= css_task_iter_next(&it
);
3686 get_task_struct(task
);
3687 css_task_iter_end(&it
);
3690 ret
= cgroup_migrate(to
, task
, false);
3691 put_task_struct(task
);
3693 } while (task
&& !ret
);
3695 cgroup_migrate_finish(&preloaded_csets
);
3696 mutex_unlock(&cgroup_mutex
);
3701 * Stuff for reading the 'tasks'/'procs' files.
3703 * Reading this file can return large amounts of data if a cgroup has
3704 * *lots* of attached tasks. So it may need several calls to read(),
3705 * but we cannot guarantee that the information we produce is correct
3706 * unless we produce it entirely atomically.
3710 /* which pidlist file are we talking about? */
3711 enum cgroup_filetype
{
3717 * A pidlist is a list of pids that virtually represents the contents of one
3718 * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
3719 * a pair (one each for procs, tasks) for each pid namespace that's relevant
3722 struct cgroup_pidlist
{
3724 * used to find which pidlist is wanted. doesn't change as long as
3725 * this particular list stays in the list.
3727 struct { enum cgroup_filetype type
; struct pid_namespace
*ns
; } key
;
3730 /* how many elements the above list has */
3732 /* each of these stored in a list by its cgroup */
3733 struct list_head links
;
3734 /* pointer to the cgroup we belong to, for list removal purposes */
3735 struct cgroup
*owner
;
3736 /* for delayed destruction */
3737 struct delayed_work destroy_dwork
;
3741 * The following two functions "fix" the issue where there are more pids
3742 * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
3743 * TODO: replace with a kernel-wide solution to this problem
3745 #define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
3746 static void *pidlist_allocate(int count
)
3748 if (PIDLIST_TOO_LARGE(count
))
3749 return vmalloc(count
* sizeof(pid_t
));
3751 return kmalloc(count
* sizeof(pid_t
), GFP_KERNEL
);
3754 static void pidlist_free(void *p
)
3756 if (is_vmalloc_addr(p
))
3763 * Used to destroy all pidlists lingering waiting for destroy timer. None
3764 * should be left afterwards.
3766 static void cgroup_pidlist_destroy_all(struct cgroup
*cgrp
)
3768 struct cgroup_pidlist
*l
, *tmp_l
;
3770 mutex_lock(&cgrp
->pidlist_mutex
);
3771 list_for_each_entry_safe(l
, tmp_l
, &cgrp
->pidlists
, links
)
3772 mod_delayed_work(cgroup_pidlist_destroy_wq
, &l
->destroy_dwork
, 0);
3773 mutex_unlock(&cgrp
->pidlist_mutex
);
3775 flush_workqueue(cgroup_pidlist_destroy_wq
);
3776 BUG_ON(!list_empty(&cgrp
->pidlists
));
3779 static void cgroup_pidlist_destroy_work_fn(struct work_struct
*work
)
3781 struct delayed_work
*dwork
= to_delayed_work(work
);
3782 struct cgroup_pidlist
*l
= container_of(dwork
, struct cgroup_pidlist
,
3784 struct cgroup_pidlist
*tofree
= NULL
;
3786 mutex_lock(&l
->owner
->pidlist_mutex
);
3789 * Destroy iff we didn't get queued again. The state won't change
3790 * as destroy_dwork can only be queued while locked.
3792 if (!delayed_work_pending(dwork
)) {
3793 list_del(&l
->links
);
3794 pidlist_free(l
->list
);
3795 put_pid_ns(l
->key
.ns
);
3799 mutex_unlock(&l
->owner
->pidlist_mutex
);
3804 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
3805 * Returns the number of unique elements.
3807 static int pidlist_uniq(pid_t
*list
, int length
)
3812 * we presume the 0th element is unique, so i starts at 1. trivial
3813 * edge cases first; no work needs to be done for either
3815 if (length
== 0 || length
== 1)
3817 /* src and dest walk down the list; dest counts unique elements */
3818 for (src
= 1; src
< length
; src
++) {
3819 /* find next unique element */
3820 while (list
[src
] == list
[src
-1]) {
3825 /* dest always points to where the next unique element goes */
3826 list
[dest
] = list
[src
];
3834 * The two pid files - task and cgroup.procs - guaranteed that the result
3835 * is sorted, which forced this whole pidlist fiasco. As pid order is
3836 * different per namespace, each namespace needs differently sorted list,
3837 * making it impossible to use, for example, single rbtree of member tasks
3838 * sorted by task pointer. As pidlists can be fairly large, allocating one
3839 * per open file is dangerous, so cgroup had to implement shared pool of
3840 * pidlists keyed by cgroup and namespace.
3842 * All this extra complexity was caused by the original implementation
3843 * committing to an entirely unnecessary property. In the long term, we
3844 * want to do away with it. Explicitly scramble sort order if on the
3845 * default hierarchy so that no such expectation exists in the new
3848 * Scrambling is done by swapping every two consecutive bits, which is
3849 * non-identity one-to-one mapping which disturbs sort order sufficiently.
3851 static pid_t
pid_fry(pid_t pid
)
3853 unsigned a
= pid
& 0x55555555;
3854 unsigned b
= pid
& 0xAAAAAAAA;
3856 return (a
<< 1) | (b
>> 1);
3859 static pid_t
cgroup_pid_fry(struct cgroup
*cgrp
, pid_t pid
)
3861 if (cgroup_on_dfl(cgrp
))
3862 return pid_fry(pid
);
3867 static int cmppid(const void *a
, const void *b
)
3869 return *(pid_t
*)a
- *(pid_t
*)b
;
3872 static int fried_cmppid(const void *a
, const void *b
)
3874 return pid_fry(*(pid_t
*)a
) - pid_fry(*(pid_t
*)b
);
3877 static struct cgroup_pidlist
*cgroup_pidlist_find(struct cgroup
*cgrp
,
3878 enum cgroup_filetype type
)
3880 struct cgroup_pidlist
*l
;
3881 /* don't need task_nsproxy() if we're looking at ourself */
3882 struct pid_namespace
*ns
= task_active_pid_ns(current
);
3884 lockdep_assert_held(&cgrp
->pidlist_mutex
);
3886 list_for_each_entry(l
, &cgrp
->pidlists
, links
)
3887 if (l
->key
.type
== type
&& l
->key
.ns
== ns
)
3893 * find the appropriate pidlist for our purpose (given procs vs tasks)
3894 * returns with the lock on that pidlist already held, and takes care
3895 * of the use count, or returns NULL with no locks held if we're out of
3898 static struct cgroup_pidlist
*cgroup_pidlist_find_create(struct cgroup
*cgrp
,
3899 enum cgroup_filetype type
)
3901 struct cgroup_pidlist
*l
;
3903 lockdep_assert_held(&cgrp
->pidlist_mutex
);
3905 l
= cgroup_pidlist_find(cgrp
, type
);
3909 /* entry not found; create a new one */
3910 l
= kzalloc(sizeof(struct cgroup_pidlist
), GFP_KERNEL
);
3914 INIT_DELAYED_WORK(&l
->destroy_dwork
, cgroup_pidlist_destroy_work_fn
);
3916 /* don't need task_nsproxy() if we're looking at ourself */
3917 l
->key
.ns
= get_pid_ns(task_active_pid_ns(current
));
3919 list_add(&l
->links
, &cgrp
->pidlists
);
3924 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
3926 static int pidlist_array_load(struct cgroup
*cgrp
, enum cgroup_filetype type
,
3927 struct cgroup_pidlist
**lp
)
3931 int pid
, n
= 0; /* used for populating the array */
3932 struct css_task_iter it
;
3933 struct task_struct
*tsk
;
3934 struct cgroup_pidlist
*l
;
3936 lockdep_assert_held(&cgrp
->pidlist_mutex
);
3939 * If cgroup gets more users after we read count, we won't have
3940 * enough space - tough. This race is indistinguishable to the
3941 * caller from the case that the additional cgroup users didn't
3942 * show up until sometime later on.
3944 length
= cgroup_task_count(cgrp
);
3945 array
= pidlist_allocate(length
);
3948 /* now, populate the array */
3949 css_task_iter_start(&cgrp
->self
, &it
);
3950 while ((tsk
= css_task_iter_next(&it
))) {
3951 if (unlikely(n
== length
))
3953 /* get tgid or pid for procs or tasks file respectively */
3954 if (type
== CGROUP_FILE_PROCS
)
3955 pid
= task_tgid_vnr(tsk
);
3957 pid
= task_pid_vnr(tsk
);
3958 if (pid
> 0) /* make sure to only use valid results */
3961 css_task_iter_end(&it
);
3963 /* now sort & (if procs) strip out duplicates */
3964 if (cgroup_on_dfl(cgrp
))
3965 sort(array
, length
, sizeof(pid_t
), fried_cmppid
, NULL
);
3967 sort(array
, length
, sizeof(pid_t
), cmppid
, NULL
);
3968 if (type
== CGROUP_FILE_PROCS
)
3969 length
= pidlist_uniq(array
, length
);
3971 l
= cgroup_pidlist_find_create(cgrp
, type
);
3973 mutex_unlock(&cgrp
->pidlist_mutex
);
3974 pidlist_free(array
);
3978 /* store array, freeing old if necessary */
3979 pidlist_free(l
->list
);
3987 * cgroupstats_build - build and fill cgroupstats
3988 * @stats: cgroupstats to fill information into
3989 * @dentry: A dentry entry belonging to the cgroup for which stats have
3992 * Build and fill cgroupstats so that taskstats can export it to user
3995 int cgroupstats_build(struct cgroupstats
*stats
, struct dentry
*dentry
)
3997 struct kernfs_node
*kn
= kernfs_node_from_dentry(dentry
);
3998 struct cgroup
*cgrp
;
3999 struct css_task_iter it
;
4000 struct task_struct
*tsk
;
4002 /* it should be kernfs_node belonging to cgroupfs and is a directory */
4003 if (dentry
->d_sb
->s_type
!= &cgroup_fs_type
|| !kn
||
4004 kernfs_type(kn
) != KERNFS_DIR
)
4007 mutex_lock(&cgroup_mutex
);
4010 * We aren't being called from kernfs and there's no guarantee on
4011 * @kn->priv's validity. For this and css_tryget_online_from_dir(),
4012 * @kn->priv is RCU safe. Let's do the RCU dancing.
4015 cgrp
= rcu_dereference(kn
->priv
);
4016 if (!cgrp
|| cgroup_is_dead(cgrp
)) {
4018 mutex_unlock(&cgroup_mutex
);
4023 css_task_iter_start(&cgrp
->self
, &it
);
4024 while ((tsk
= css_task_iter_next(&it
))) {
4025 switch (tsk
->state
) {
4027 stats
->nr_running
++;
4029 case TASK_INTERRUPTIBLE
:
4030 stats
->nr_sleeping
++;
4032 case TASK_UNINTERRUPTIBLE
:
4033 stats
->nr_uninterruptible
++;
4036 stats
->nr_stopped
++;
4039 if (delayacct_is_task_waiting_on_io(tsk
))
4040 stats
->nr_io_wait
++;
4044 css_task_iter_end(&it
);
4046 mutex_unlock(&cgroup_mutex
);
4052 * seq_file methods for the tasks/procs files. The seq_file position is the
4053 * next pid to display; the seq_file iterator is a pointer to the pid
4054 * in the cgroup->l->list array.
4057 static void *cgroup_pidlist_start(struct seq_file
*s
, loff_t
*pos
)
4060 * Initially we receive a position value that corresponds to
4061 * one more than the last pid shown (or 0 on the first call or
4062 * after a seek to the start). Use a binary-search to find the
4063 * next pid to display, if any
4065 struct kernfs_open_file
*of
= s
->private;
4066 struct cgroup
*cgrp
= seq_css(s
)->cgroup
;
4067 struct cgroup_pidlist
*l
;
4068 enum cgroup_filetype type
= seq_cft(s
)->private;
4069 int index
= 0, pid
= *pos
;
4072 mutex_lock(&cgrp
->pidlist_mutex
);
4075 * !NULL @of->priv indicates that this isn't the first start()
4076 * after open. If the matching pidlist is around, we can use that.
4077 * Look for it. Note that @of->priv can't be used directly. It
4078 * could already have been destroyed.
4081 of
->priv
= cgroup_pidlist_find(cgrp
, type
);
4084 * Either this is the first start() after open or the matching
4085 * pidlist has been destroyed inbetween. Create a new one.
4088 ret
= pidlist_array_load(cgrp
, type
,
4089 (struct cgroup_pidlist
**)&of
->priv
);
4091 return ERR_PTR(ret
);
4096 int end
= l
->length
;
4098 while (index
< end
) {
4099 int mid
= (index
+ end
) / 2;
4100 if (cgroup_pid_fry(cgrp
, l
->list
[mid
]) == pid
) {
4103 } else if (cgroup_pid_fry(cgrp
, l
->list
[mid
]) <= pid
)
4109 /* If we're off the end of the array, we're done */
4110 if (index
>= l
->length
)
4112 /* Update the abstract position to be the actual pid that we found */
4113 iter
= l
->list
+ index
;
4114 *pos
= cgroup_pid_fry(cgrp
, *iter
);
4118 static void cgroup_pidlist_stop(struct seq_file
*s
, void *v
)
4120 struct kernfs_open_file
*of
= s
->private;
4121 struct cgroup_pidlist
*l
= of
->priv
;
4124 mod_delayed_work(cgroup_pidlist_destroy_wq
, &l
->destroy_dwork
,
4125 CGROUP_PIDLIST_DESTROY_DELAY
);
4126 mutex_unlock(&seq_css(s
)->cgroup
->pidlist_mutex
);
4129 static void *cgroup_pidlist_next(struct seq_file
*s
, void *v
, loff_t
*pos
)
4131 struct kernfs_open_file
*of
= s
->private;
4132 struct cgroup_pidlist
*l
= of
->priv
;
4134 pid_t
*end
= l
->list
+ l
->length
;
4136 * Advance to the next pid in the array. If this goes off the
4143 *pos
= cgroup_pid_fry(seq_css(s
)->cgroup
, *p
);
4148 static int cgroup_pidlist_show(struct seq_file
*s
, void *v
)
4150 return seq_printf(s
, "%d\n", *(int *)v
);
4153 static u64
cgroup_read_notify_on_release(struct cgroup_subsys_state
*css
,
4156 return notify_on_release(css
->cgroup
);
4159 static int cgroup_write_notify_on_release(struct cgroup_subsys_state
*css
,
4160 struct cftype
*cft
, u64 val
)
4162 clear_bit(CGRP_RELEASABLE
, &css
->cgroup
->flags
);
4164 set_bit(CGRP_NOTIFY_ON_RELEASE
, &css
->cgroup
->flags
);
4166 clear_bit(CGRP_NOTIFY_ON_RELEASE
, &css
->cgroup
->flags
);
4170 static u64
cgroup_clone_children_read(struct cgroup_subsys_state
*css
,
4173 return test_bit(CGRP_CPUSET_CLONE_CHILDREN
, &css
->cgroup
->flags
);
4176 static int cgroup_clone_children_write(struct cgroup_subsys_state
*css
,
4177 struct cftype
*cft
, u64 val
)
4180 set_bit(CGRP_CPUSET_CLONE_CHILDREN
, &css
->cgroup
->flags
);
4182 clear_bit(CGRP_CPUSET_CLONE_CHILDREN
, &css
->cgroup
->flags
);
4186 /* cgroup core interface files for the default hierarchy */
4187 static struct cftype cgroup_dfl_base_files
[] = {
4189 .name
= "cgroup.procs",
4190 .seq_start
= cgroup_pidlist_start
,
4191 .seq_next
= cgroup_pidlist_next
,
4192 .seq_stop
= cgroup_pidlist_stop
,
4193 .seq_show
= cgroup_pidlist_show
,
4194 .private = CGROUP_FILE_PROCS
,
4195 .write
= cgroup_procs_write
,
4196 .mode
= S_IRUGO
| S_IWUSR
,
4199 .name
= "cgroup.controllers",
4200 .flags
= CFTYPE_ONLY_ON_ROOT
,
4201 .seq_show
= cgroup_root_controllers_show
,
4204 .name
= "cgroup.controllers",
4205 .flags
= CFTYPE_NOT_ON_ROOT
,
4206 .seq_show
= cgroup_controllers_show
,
4209 .name
= "cgroup.subtree_control",
4210 .seq_show
= cgroup_subtree_control_show
,
4211 .write
= cgroup_subtree_control_write
,
4214 .name
= "cgroup.populated",
4215 .flags
= CFTYPE_NOT_ON_ROOT
,
4216 .seq_show
= cgroup_populated_show
,
4221 /* cgroup core interface files for the legacy hierarchies */
4222 static struct cftype cgroup_legacy_base_files
[] = {
4224 .name
= "cgroup.procs",
4225 .seq_start
= cgroup_pidlist_start
,
4226 .seq_next
= cgroup_pidlist_next
,
4227 .seq_stop
= cgroup_pidlist_stop
,
4228 .seq_show
= cgroup_pidlist_show
,
4229 .private = CGROUP_FILE_PROCS
,
4230 .write
= cgroup_procs_write
,
4231 .mode
= S_IRUGO
| S_IWUSR
,
4234 .name
= "cgroup.clone_children",
4235 .read_u64
= cgroup_clone_children_read
,
4236 .write_u64
= cgroup_clone_children_write
,
4239 .name
= "cgroup.sane_behavior",
4240 .flags
= CFTYPE_ONLY_ON_ROOT
,
4241 .seq_show
= cgroup_sane_behavior_show
,
4245 .seq_start
= cgroup_pidlist_start
,
4246 .seq_next
= cgroup_pidlist_next
,
4247 .seq_stop
= cgroup_pidlist_stop
,
4248 .seq_show
= cgroup_pidlist_show
,
4249 .private = CGROUP_FILE_TASKS
,
4250 .write
= cgroup_tasks_write
,
4251 .mode
= S_IRUGO
| S_IWUSR
,
4254 .name
= "notify_on_release",
4255 .read_u64
= cgroup_read_notify_on_release
,
4256 .write_u64
= cgroup_write_notify_on_release
,
4259 .name
= "release_agent",
4260 .flags
= CFTYPE_ONLY_ON_ROOT
,
4261 .seq_show
= cgroup_release_agent_show
,
4262 .write
= cgroup_release_agent_write
,
4263 .max_write_len
= PATH_MAX
- 1,
4269 * cgroup_populate_dir - create subsys files in a cgroup directory
4270 * @cgrp: target cgroup
4271 * @subsys_mask: mask of the subsystem ids whose files should be added
4273 * On failure, no file is added.
4275 static int cgroup_populate_dir(struct cgroup
*cgrp
, unsigned int subsys_mask
)
4277 struct cgroup_subsys
*ss
;
4280 /* process cftsets of each subsystem */
4281 for_each_subsys(ss
, i
) {
4282 struct cftype
*cfts
;
4284 if (!(subsys_mask
& (1 << i
)))
4287 list_for_each_entry(cfts
, &ss
->cfts
, node
) {
4288 ret
= cgroup_addrm_files(cgrp
, cfts
, true);
4295 cgroup_clear_dir(cgrp
, subsys_mask
);
4300 * css destruction is four-stage process.
4302 * 1. Destruction starts. Killing of the percpu_ref is initiated.
4303 * Implemented in kill_css().
4305 * 2. When the percpu_ref is confirmed to be visible as killed on all CPUs
4306 * and thus css_tryget_online() is guaranteed to fail, the css can be
4307 * offlined by invoking offline_css(). After offlining, the base ref is
4308 * put. Implemented in css_killed_work_fn().
4310 * 3. When the percpu_ref reaches zero, the only possible remaining
4311 * accessors are inside RCU read sections. css_release() schedules the
4314 * 4. After the grace period, the css can be freed. Implemented in
4315 * css_free_work_fn().
4317 * It is actually hairier because both step 2 and 4 require process context
4318 * and thus involve punting to css->destroy_work adding two additional
4319 * steps to the already complex sequence.
4321 static void css_free_work_fn(struct work_struct
*work
)
4323 struct cgroup_subsys_state
*css
=
4324 container_of(work
, struct cgroup_subsys_state
, destroy_work
);
4325 struct cgroup
*cgrp
= css
->cgroup
;
4327 percpu_ref_exit(&css
->refcnt
);
4332 css_put(css
->parent
);
4334 css
->ss
->css_free(css
);
4337 /* cgroup free path */
4338 atomic_dec(&cgrp
->root
->nr_cgrps
);
4339 cgroup_pidlist_destroy_all(cgrp
);
4341 if (cgroup_parent(cgrp
)) {
4343 * We get a ref to the parent, and put the ref when
4344 * this cgroup is being freed, so it's guaranteed
4345 * that the parent won't be destroyed before its
4348 cgroup_put(cgroup_parent(cgrp
));
4349 kernfs_put(cgrp
->kn
);
4353 * This is root cgroup's refcnt reaching zero,
4354 * which indicates that the root should be
4357 cgroup_destroy_root(cgrp
->root
);
4362 static void css_free_rcu_fn(struct rcu_head
*rcu_head
)
4364 struct cgroup_subsys_state
*css
=
4365 container_of(rcu_head
, struct cgroup_subsys_state
, rcu_head
);
4367 INIT_WORK(&css
->destroy_work
, css_free_work_fn
);
4368 queue_work(cgroup_destroy_wq
, &css
->destroy_work
);
4371 static void css_release_work_fn(struct work_struct
*work
)
4373 struct cgroup_subsys_state
*css
=
4374 container_of(work
, struct cgroup_subsys_state
, destroy_work
);
4375 struct cgroup_subsys
*ss
= css
->ss
;
4376 struct cgroup
*cgrp
= css
->cgroup
;
4378 mutex_lock(&cgroup_mutex
);
4380 css
->flags
|= CSS_RELEASED
;
4381 list_del_rcu(&css
->sibling
);
4384 /* css release path */
4385 cgroup_idr_remove(&ss
->css_idr
, css
->id
);
4387 /* cgroup release path */
4388 cgroup_idr_remove(&cgrp
->root
->cgroup_idr
, cgrp
->id
);
4392 mutex_unlock(&cgroup_mutex
);
4394 call_rcu(&css
->rcu_head
, css_free_rcu_fn
);
4397 static void css_release(struct percpu_ref
*ref
)
4399 struct cgroup_subsys_state
*css
=
4400 container_of(ref
, struct cgroup_subsys_state
, refcnt
);
4402 INIT_WORK(&css
->destroy_work
, css_release_work_fn
);
4403 queue_work(cgroup_destroy_wq
, &css
->destroy_work
);
4406 static void init_and_link_css(struct cgroup_subsys_state
*css
,
4407 struct cgroup_subsys
*ss
, struct cgroup
*cgrp
)
4409 lockdep_assert_held(&cgroup_mutex
);
4413 memset(css
, 0, sizeof(*css
));
4416 INIT_LIST_HEAD(&css
->sibling
);
4417 INIT_LIST_HEAD(&css
->children
);
4418 css
->serial_nr
= css_serial_nr_next
++;
4420 if (cgroup_parent(cgrp
)) {
4421 css
->parent
= cgroup_css(cgroup_parent(cgrp
), ss
);
4422 css_get(css
->parent
);
4425 BUG_ON(cgroup_css(cgrp
, ss
));
4428 /* invoke ->css_online() on a new CSS and mark it online if successful */
4429 static int online_css(struct cgroup_subsys_state
*css
)
4431 struct cgroup_subsys
*ss
= css
->ss
;
4434 lockdep_assert_held(&cgroup_mutex
);
4437 ret
= ss
->css_online(css
);
4439 css
->flags
|= CSS_ONLINE
;
4440 rcu_assign_pointer(css
->cgroup
->subsys
[ss
->id
], css
);
4445 /* if the CSS is online, invoke ->css_offline() on it and mark it offline */
4446 static void offline_css(struct cgroup_subsys_state
*css
)
4448 struct cgroup_subsys
*ss
= css
->ss
;
4450 lockdep_assert_held(&cgroup_mutex
);
4452 if (!(css
->flags
& CSS_ONLINE
))
4455 if (ss
->css_offline
)
4456 ss
->css_offline(css
);
4458 css
->flags
&= ~CSS_ONLINE
;
4459 RCU_INIT_POINTER(css
->cgroup
->subsys
[ss
->id
], NULL
);
4461 wake_up_all(&css
->cgroup
->offline_waitq
);
4465 * create_css - create a cgroup_subsys_state
4466 * @cgrp: the cgroup new css will be associated with
4467 * @ss: the subsys of new css
4468 * @visible: whether to create control knobs for the new css or not
4470 * Create a new css associated with @cgrp - @ss pair. On success, the new
4471 * css is online and installed in @cgrp with all interface files created if
4472 * @visible. Returns 0 on success, -errno on failure.
4474 static int create_css(struct cgroup
*cgrp
, struct cgroup_subsys
*ss
,
4477 struct cgroup
*parent
= cgroup_parent(cgrp
);
4478 struct cgroup_subsys_state
*parent_css
= cgroup_css(parent
, ss
);
4479 struct cgroup_subsys_state
*css
;
4482 lockdep_assert_held(&cgroup_mutex
);
4484 css
= ss
->css_alloc(parent_css
);
4486 return PTR_ERR(css
);
4488 init_and_link_css(css
, ss
, cgrp
);
4490 err
= percpu_ref_init(&css
->refcnt
, css_release
);
4494 err
= cgroup_idr_alloc(&ss
->css_idr
, NULL
, 2, 0, GFP_NOWAIT
);
4496 goto err_free_percpu_ref
;
4500 err
= cgroup_populate_dir(cgrp
, 1 << ss
->id
);
4505 /* @css is ready to be brought online now, make it visible */
4506 list_add_tail_rcu(&css
->sibling
, &parent_css
->children
);
4507 cgroup_idr_replace(&ss
->css_idr
, css
, css
->id
);
4509 err
= online_css(css
);
4513 if (ss
->broken_hierarchy
&& !ss
->warned_broken_hierarchy
&&
4514 cgroup_parent(parent
)) {
4515 pr_warn("%s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n",
4516 current
->comm
, current
->pid
, ss
->name
);
4517 if (!strcmp(ss
->name
, "memory"))
4518 pr_warn("\"memory\" requires setting use_hierarchy to 1 on the root\n");
4519 ss
->warned_broken_hierarchy
= true;
4525 list_del_rcu(&css
->sibling
);
4526 cgroup_clear_dir(css
->cgroup
, 1 << css
->ss
->id
);
4528 cgroup_idr_remove(&ss
->css_idr
, css
->id
);
4529 err_free_percpu_ref
:
4530 percpu_ref_exit(&css
->refcnt
);
4532 call_rcu(&css
->rcu_head
, css_free_rcu_fn
);
4536 static int cgroup_mkdir(struct kernfs_node
*parent_kn
, const char *name
,
4539 struct cgroup
*parent
, *cgrp
;
4540 struct cgroup_root
*root
;
4541 struct cgroup_subsys
*ss
;
4542 struct kernfs_node
*kn
;
4543 struct cftype
*base_files
;
4546 parent
= cgroup_kn_lock_live(parent_kn
);
4549 root
= parent
->root
;
4551 /* allocate the cgroup and its ID, 0 is reserved for the root */
4552 cgrp
= kzalloc(sizeof(*cgrp
), GFP_KERNEL
);
4558 ret
= percpu_ref_init(&cgrp
->self
.refcnt
, css_release
);
4563 * Temporarily set the pointer to NULL, so idr_find() won't return
4564 * a half-baked cgroup.
4566 cgrp
->id
= cgroup_idr_alloc(&root
->cgroup_idr
, NULL
, 2, 0, GFP_NOWAIT
);
4569 goto out_cancel_ref
;
4572 init_cgroup_housekeeping(cgrp
);
4574 cgrp
->self
.parent
= &parent
->self
;
4577 if (notify_on_release(parent
))
4578 set_bit(CGRP_NOTIFY_ON_RELEASE
, &cgrp
->flags
);
4580 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN
, &parent
->flags
))
4581 set_bit(CGRP_CPUSET_CLONE_CHILDREN
, &cgrp
->flags
);
4583 /* create the directory */
4584 kn
= kernfs_create_dir(parent
->kn
, name
, mode
, cgrp
);
4592 * This extra ref will be put in cgroup_free_fn() and guarantees
4593 * that @cgrp->kn is always accessible.
4597 cgrp
->self
.serial_nr
= css_serial_nr_next
++;
4599 /* allocation complete, commit to creation */
4600 list_add_tail_rcu(&cgrp
->self
.sibling
, &cgroup_parent(cgrp
)->self
.children
);
4601 atomic_inc(&root
->nr_cgrps
);
4605 * @cgrp is now fully operational. If something fails after this
4606 * point, it'll be released via the normal destruction path.
4608 cgroup_idr_replace(&root
->cgroup_idr
, cgrp
, cgrp
->id
);
4610 ret
= cgroup_kn_set_ugid(kn
);
4614 if (cgroup_on_dfl(cgrp
))
4615 base_files
= cgroup_dfl_base_files
;
4617 base_files
= cgroup_legacy_base_files
;
4619 ret
= cgroup_addrm_files(cgrp
, base_files
, true);
4623 /* let's create and online css's */
4624 for_each_subsys(ss
, ssid
) {
4625 if (parent
->child_subsys_mask
& (1 << ssid
)) {
4626 ret
= create_css(cgrp
, ss
,
4627 parent
->subtree_control
& (1 << ssid
));
4634 * On the default hierarchy, a child doesn't automatically inherit
4635 * subtree_control from the parent. Each is configured manually.
4637 if (!cgroup_on_dfl(cgrp
)) {
4638 cgrp
->subtree_control
= parent
->subtree_control
;
4639 cgroup_refresh_child_subsys_mask(cgrp
);
4642 kernfs_activate(kn
);
4648 cgroup_idr_remove(&root
->cgroup_idr
, cgrp
->id
);
4650 percpu_ref_exit(&cgrp
->self
.refcnt
);
4654 cgroup_kn_unlock(parent_kn
);
4658 cgroup_destroy_locked(cgrp
);
4663 * This is called when the refcnt of a css is confirmed to be killed.
4664 * css_tryget_online() is now guaranteed to fail. Tell the subsystem to
4665 * initate destruction and put the css ref from kill_css().
4667 static void css_killed_work_fn(struct work_struct
*work
)
4669 struct cgroup_subsys_state
*css
=
4670 container_of(work
, struct cgroup_subsys_state
, destroy_work
);
4672 mutex_lock(&cgroup_mutex
);
4674 mutex_unlock(&cgroup_mutex
);
4679 /* css kill confirmation processing requires process context, bounce */
4680 static void css_killed_ref_fn(struct percpu_ref
*ref
)
4682 struct cgroup_subsys_state
*css
=
4683 container_of(ref
, struct cgroup_subsys_state
, refcnt
);
4685 INIT_WORK(&css
->destroy_work
, css_killed_work_fn
);
4686 queue_work(cgroup_destroy_wq
, &css
->destroy_work
);
4690 * kill_css - destroy a css
4691 * @css: css to destroy
4693 * This function initiates destruction of @css by removing cgroup interface
4694 * files and putting its base reference. ->css_offline() will be invoked
4695 * asynchronously once css_tryget_online() is guaranteed to fail and when
4696 * the reference count reaches zero, @css will be released.
4698 static void kill_css(struct cgroup_subsys_state
*css
)
4700 lockdep_assert_held(&cgroup_mutex
);
4703 * This must happen before css is disassociated with its cgroup.
4704 * See seq_css() for details.
4706 cgroup_clear_dir(css
->cgroup
, 1 << css
->ss
->id
);
4709 * Killing would put the base ref, but we need to keep it alive
4710 * until after ->css_offline().
4715 * cgroup core guarantees that, by the time ->css_offline() is
4716 * invoked, no new css reference will be given out via
4717 * css_tryget_online(). We can't simply call percpu_ref_kill() and
4718 * proceed to offlining css's because percpu_ref_kill() doesn't
4719 * guarantee that the ref is seen as killed on all CPUs on return.
4721 * Use percpu_ref_kill_and_confirm() to get notifications as each
4722 * css is confirmed to be seen as killed on all CPUs.
4724 percpu_ref_kill_and_confirm(&css
->refcnt
, css_killed_ref_fn
);
4728 * cgroup_destroy_locked - the first stage of cgroup destruction
4729 * @cgrp: cgroup to be destroyed
4731 * css's make use of percpu refcnts whose killing latency shouldn't be
4732 * exposed to userland and are RCU protected. Also, cgroup core needs to
4733 * guarantee that css_tryget_online() won't succeed by the time
4734 * ->css_offline() is invoked. To satisfy all the requirements,
4735 * destruction is implemented in the following two steps.
4737 * s1. Verify @cgrp can be destroyed and mark it dying. Remove all
4738 * userland visible parts and start killing the percpu refcnts of
4739 * css's. Set up so that the next stage will be kicked off once all
4740 * the percpu refcnts are confirmed to be killed.
4742 * s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the
4743 * rest of destruction. Once all cgroup references are gone, the
4744 * cgroup is RCU-freed.
4746 * This function implements s1. After this step, @cgrp is gone as far as
4747 * the userland is concerned and a new cgroup with the same name may be
4748 * created. As cgroup doesn't care about the names internally, this
4749 * doesn't cause any problem.
4751 static int cgroup_destroy_locked(struct cgroup
*cgrp
)
4752 __releases(&cgroup_mutex
) __acquires(&cgroup_mutex
)
4754 struct cgroup_subsys_state
*css
;
4758 lockdep_assert_held(&cgroup_mutex
);
4761 * css_set_rwsem synchronizes access to ->cset_links and prevents
4762 * @cgrp from being removed while put_css_set() is in progress.
4764 down_read(&css_set_rwsem
);
4765 empty
= list_empty(&cgrp
->cset_links
);
4766 up_read(&css_set_rwsem
);
4771 * Make sure there's no live children. We can't test emptiness of
4772 * ->self.children as dead children linger on it while being
4773 * drained; otherwise, "rmdir parent/child parent" may fail.
4775 if (css_has_online_children(&cgrp
->self
))
4779 * Mark @cgrp dead. This prevents further task migration and child
4780 * creation by disabling cgroup_lock_live_group().
4782 cgrp
->self
.flags
&= ~CSS_ONLINE
;
4784 /* initiate massacre of all css's */
4785 for_each_css(css
, ssid
, cgrp
)
4788 /* CSS_ONLINE is clear, remove from ->release_list for the last time */
4789 raw_spin_lock(&release_list_lock
);
4790 if (!list_empty(&cgrp
->release_list
))
4791 list_del_init(&cgrp
->release_list
);
4792 raw_spin_unlock(&release_list_lock
);
4795 * Remove @cgrp directory along with the base files. @cgrp has an
4796 * extra ref on its kn.
4798 kernfs_remove(cgrp
->kn
);
4800 set_bit(CGRP_RELEASABLE
, &cgroup_parent(cgrp
)->flags
);
4801 check_for_release(cgroup_parent(cgrp
));
4803 /* put the base reference */
4804 percpu_ref_kill(&cgrp
->self
.refcnt
);
4809 static int cgroup_rmdir(struct kernfs_node
*kn
)
4811 struct cgroup
*cgrp
;
4814 cgrp
= cgroup_kn_lock_live(kn
);
4817 cgroup_get(cgrp
); /* for @kn->priv clearing */
4819 ret
= cgroup_destroy_locked(cgrp
);
4821 cgroup_kn_unlock(kn
);
4824 * There are two control paths which try to determine cgroup from
4825 * dentry without going through kernfs - cgroupstats_build() and
4826 * css_tryget_online_from_dir(). Those are supported by RCU
4827 * protecting clearing of cgrp->kn->priv backpointer, which should
4828 * happen after all files under it have been removed.
4831 RCU_INIT_POINTER(*(void __rcu __force
**)&kn
->priv
, NULL
);
4837 static struct kernfs_syscall_ops cgroup_kf_syscall_ops
= {
4838 .remount_fs
= cgroup_remount
,
4839 .show_options
= cgroup_show_options
,
4840 .mkdir
= cgroup_mkdir
,
4841 .rmdir
= cgroup_rmdir
,
4842 .rename
= cgroup_rename
,
4845 static void __init
cgroup_init_subsys(struct cgroup_subsys
*ss
, bool early
)
4847 struct cgroup_subsys_state
*css
;
4849 printk(KERN_INFO
"Initializing cgroup subsys %s\n", ss
->name
);
4851 mutex_lock(&cgroup_mutex
);
4853 idr_init(&ss
->css_idr
);
4854 INIT_LIST_HEAD(&ss
->cfts
);
4856 /* Create the root cgroup state for this subsystem */
4857 ss
->root
= &cgrp_dfl_root
;
4858 css
= ss
->css_alloc(cgroup_css(&cgrp_dfl_root
.cgrp
, ss
));
4859 /* We don't handle early failures gracefully */
4860 BUG_ON(IS_ERR(css
));
4861 init_and_link_css(css
, ss
, &cgrp_dfl_root
.cgrp
);
4864 * Root csses are never destroyed and we can't initialize
4865 * percpu_ref during early init. Disable refcnting.
4867 css
->flags
|= CSS_NO_REF
;
4870 /* allocation can't be done safely during early init */
4873 css
->id
= cgroup_idr_alloc(&ss
->css_idr
, css
, 1, 2, GFP_KERNEL
);
4874 BUG_ON(css
->id
< 0);
4877 /* Update the init_css_set to contain a subsys
4878 * pointer to this state - since the subsystem is
4879 * newly registered, all tasks and hence the
4880 * init_css_set is in the subsystem's root cgroup. */
4881 init_css_set
.subsys
[ss
->id
] = css
;
4883 need_forkexit_callback
|= ss
->fork
|| ss
->exit
;
4885 /* At system boot, before all subsystems have been
4886 * registered, no tasks have been forked, so we don't
4887 * need to invoke fork callbacks here. */
4888 BUG_ON(!list_empty(&init_task
.tasks
));
4890 BUG_ON(online_css(css
));
4892 mutex_unlock(&cgroup_mutex
);
4896 * cgroup_init_early - cgroup initialization at system boot
4898 * Initialize cgroups at system boot, and initialize any
4899 * subsystems that request early init.
4901 int __init
cgroup_init_early(void)
4903 static struct cgroup_sb_opts __initdata opts
;
4904 struct cgroup_subsys
*ss
;
4907 init_cgroup_root(&cgrp_dfl_root
, &opts
);
4908 cgrp_dfl_root
.cgrp
.self
.flags
|= CSS_NO_REF
;
4910 RCU_INIT_POINTER(init_task
.cgroups
, &init_css_set
);
4912 for_each_subsys(ss
, i
) {
4913 WARN(!ss
->css_alloc
|| !ss
->css_free
|| ss
->name
|| ss
->id
,
4914 "invalid cgroup_subsys %d:%s css_alloc=%p css_free=%p name:id=%d:%s\n",
4915 i
, cgroup_subsys_name
[i
], ss
->css_alloc
, ss
->css_free
,
4917 WARN(strlen(cgroup_subsys_name
[i
]) > MAX_CGROUP_TYPE_NAMELEN
,
4918 "cgroup_subsys_name %s too long\n", cgroup_subsys_name
[i
]);
4921 ss
->name
= cgroup_subsys_name
[i
];
4924 cgroup_init_subsys(ss
, true);
4930 * cgroup_init - cgroup initialization
4932 * Register cgroup filesystem and /proc file, and initialize
4933 * any subsystems that didn't request early init.
4935 int __init
cgroup_init(void)
4937 struct cgroup_subsys
*ss
;
4941 BUG_ON(cgroup_init_cftypes(NULL
, cgroup_dfl_base_files
));
4942 BUG_ON(cgroup_init_cftypes(NULL
, cgroup_legacy_base_files
));
4944 mutex_lock(&cgroup_mutex
);
4946 /* Add init_css_set to the hash table */
4947 key
= css_set_hash(init_css_set
.subsys
);
4948 hash_add(css_set_table
, &init_css_set
.hlist
, key
);
4950 BUG_ON(cgroup_setup_root(&cgrp_dfl_root
, 0));
4952 mutex_unlock(&cgroup_mutex
);
4954 for_each_subsys(ss
, ssid
) {
4955 if (ss
->early_init
) {
4956 struct cgroup_subsys_state
*css
=
4957 init_css_set
.subsys
[ss
->id
];
4959 css
->id
= cgroup_idr_alloc(&ss
->css_idr
, css
, 1, 2,
4961 BUG_ON(css
->id
< 0);
4963 cgroup_init_subsys(ss
, false);
4966 list_add_tail(&init_css_set
.e_cset_node
[ssid
],
4967 &cgrp_dfl_root
.cgrp
.e_csets
[ssid
]);
4970 * Setting dfl_root subsys_mask needs to consider the
4971 * disabled flag and cftype registration needs kmalloc,
4972 * both of which aren't available during early_init.
4977 cgrp_dfl_root
.subsys_mask
|= 1 << ss
->id
;
4979 if (cgroup_legacy_files_on_dfl
&& !ss
->dfl_cftypes
)
4980 ss
->dfl_cftypes
= ss
->legacy_cftypes
;
4982 if (!ss
->dfl_cftypes
)
4983 cgrp_dfl_root_inhibit_ss_mask
|= 1 << ss
->id
;
4985 if (ss
->dfl_cftypes
== ss
->legacy_cftypes
) {
4986 WARN_ON(cgroup_add_cftypes(ss
, ss
->dfl_cftypes
));
4988 WARN_ON(cgroup_add_dfl_cftypes(ss
, ss
->dfl_cftypes
));
4989 WARN_ON(cgroup_add_legacy_cftypes(ss
, ss
->legacy_cftypes
));
4993 cgroup_kobj
= kobject_create_and_add("cgroup", fs_kobj
);
4997 err
= register_filesystem(&cgroup_fs_type
);
4999 kobject_put(cgroup_kobj
);
5003 proc_create("cgroups", 0, NULL
, &proc_cgroupstats_operations
);
5007 static int __init
cgroup_wq_init(void)
5010 * There isn't much point in executing destruction path in
5011 * parallel. Good chunk is serialized with cgroup_mutex anyway.
5012 * Use 1 for @max_active.
5014 * We would prefer to do this in cgroup_init() above, but that
5015 * is called before init_workqueues(): so leave this until after.
5017 cgroup_destroy_wq
= alloc_workqueue("cgroup_destroy", 0, 1);
5018 BUG_ON(!cgroup_destroy_wq
);
5021 * Used to destroy pidlists and separate to serve as flush domain.
5022 * Cap @max_active to 1 too.
5024 cgroup_pidlist_destroy_wq
= alloc_workqueue("cgroup_pidlist_destroy",
5026 BUG_ON(!cgroup_pidlist_destroy_wq
);
5030 core_initcall(cgroup_wq_init
);
5033 * proc_cgroup_show()
5034 * - Print task's cgroup paths into seq_file, one line for each hierarchy
5035 * - Used for /proc/<pid>/cgroup.
5038 /* TODO: Use a proper seq_file iterator */
5039 int proc_cgroup_show(struct seq_file
*m
, void *v
)
5042 struct task_struct
*tsk
;
5045 struct cgroup_root
*root
;
5048 buf
= kmalloc(PATH_MAX
, GFP_KERNEL
);
5054 tsk
= get_pid_task(pid
, PIDTYPE_PID
);
5060 mutex_lock(&cgroup_mutex
);
5061 down_read(&css_set_rwsem
);
5063 for_each_root(root
) {
5064 struct cgroup_subsys
*ss
;
5065 struct cgroup
*cgrp
;
5066 int ssid
, count
= 0;
5068 if (root
== &cgrp_dfl_root
&& !cgrp_dfl_root_visible
)
5071 seq_printf(m
, "%d:", root
->hierarchy_id
);
5072 for_each_subsys(ss
, ssid
)
5073 if (root
->subsys_mask
& (1 << ssid
))
5074 seq_printf(m
, "%s%s", count
++ ? "," : "", ss
->name
);
5075 if (strlen(root
->name
))
5076 seq_printf(m
, "%sname=%s", count
? "," : "",
5079 cgrp
= task_cgroup_from_root(tsk
, root
);
5080 path
= cgroup_path(cgrp
, buf
, PATH_MAX
);
5082 retval
= -ENAMETOOLONG
;
5090 up_read(&css_set_rwsem
);
5091 mutex_unlock(&cgroup_mutex
);
5092 put_task_struct(tsk
);
5099 /* Display information about each subsystem and each hierarchy */
5100 static int proc_cgroupstats_show(struct seq_file
*m
, void *v
)
5102 struct cgroup_subsys
*ss
;
5105 seq_puts(m
, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
5107 * ideally we don't want subsystems moving around while we do this.
5108 * cgroup_mutex is also necessary to guarantee an atomic snapshot of
5109 * subsys/hierarchy state.
5111 mutex_lock(&cgroup_mutex
);
5113 for_each_subsys(ss
, i
)
5114 seq_printf(m
, "%s\t%d\t%d\t%d\n",
5115 ss
->name
, ss
->root
->hierarchy_id
,
5116 atomic_read(&ss
->root
->nr_cgrps
), !ss
->disabled
);
5118 mutex_unlock(&cgroup_mutex
);
5122 static int cgroupstats_open(struct inode
*inode
, struct file
*file
)
5124 return single_open(file
, proc_cgroupstats_show
, NULL
);
5127 static const struct file_operations proc_cgroupstats_operations
= {
5128 .open
= cgroupstats_open
,
5130 .llseek
= seq_lseek
,
5131 .release
= single_release
,
5135 * cgroup_fork - initialize cgroup related fields during copy_process()
5136 * @child: pointer to task_struct of forking parent process.
5138 * A task is associated with the init_css_set until cgroup_post_fork()
5139 * attaches it to the parent's css_set. Empty cg_list indicates that
5140 * @child isn't holding reference to its css_set.
5142 void cgroup_fork(struct task_struct
*child
)
5144 RCU_INIT_POINTER(child
->cgroups
, &init_css_set
);
5145 INIT_LIST_HEAD(&child
->cg_list
);
5149 * cgroup_post_fork - called on a new task after adding it to the task list
5150 * @child: the task in question
5152 * Adds the task to the list running through its css_set if necessary and
5153 * call the subsystem fork() callbacks. Has to be after the task is
5154 * visible on the task list in case we race with the first call to
5155 * cgroup_task_iter_start() - to guarantee that the new task ends up on its
5158 void cgroup_post_fork(struct task_struct
*child
)
5160 struct cgroup_subsys
*ss
;
5164 * This may race against cgroup_enable_task_cg_links(). As that
5165 * function sets use_task_css_set_links before grabbing
5166 * tasklist_lock and we just went through tasklist_lock to add
5167 * @child, it's guaranteed that either we see the set
5168 * use_task_css_set_links or cgroup_enable_task_cg_lists() sees
5169 * @child during its iteration.
5171 * If we won the race, @child is associated with %current's
5172 * css_set. Grabbing css_set_rwsem guarantees both that the
5173 * association is stable, and, on completion of the parent's
5174 * migration, @child is visible in the source of migration or
5175 * already in the destination cgroup. This guarantee is necessary
5176 * when implementing operations which need to migrate all tasks of
5177 * a cgroup to another.
5179 * Note that if we lose to cgroup_enable_task_cg_links(), @child
5180 * will remain in init_css_set. This is safe because all tasks are
5181 * in the init_css_set before cg_links is enabled and there's no
5182 * operation which transfers all tasks out of init_css_set.
5184 if (use_task_css_set_links
) {
5185 struct css_set
*cset
;
5187 down_write(&css_set_rwsem
);
5188 cset
= task_css_set(current
);
5189 if (list_empty(&child
->cg_list
)) {
5190 rcu_assign_pointer(child
->cgroups
, cset
);
5191 list_add(&child
->cg_list
, &cset
->tasks
);
5194 up_write(&css_set_rwsem
);
5198 * Call ss->fork(). This must happen after @child is linked on
5199 * css_set; otherwise, @child might change state between ->fork()
5200 * and addition to css_set.
5202 if (need_forkexit_callback
) {
5203 for_each_subsys(ss
, i
)
5210 * cgroup_exit - detach cgroup from exiting task
5211 * @tsk: pointer to task_struct of exiting process
5213 * Description: Detach cgroup from @tsk and release it.
5215 * Note that cgroups marked notify_on_release force every task in
5216 * them to take the global cgroup_mutex mutex when exiting.
5217 * This could impact scaling on very large systems. Be reluctant to
5218 * use notify_on_release cgroups where very high task exit scaling
5219 * is required on large systems.
5221 * We set the exiting tasks cgroup to the root cgroup (top_cgroup). We
5222 * call cgroup_exit() while the task is still competent to handle
5223 * notify_on_release(), then leave the task attached to the root cgroup in
5224 * each hierarchy for the remainder of its exit. No need to bother with
5225 * init_css_set refcnting. init_css_set never goes away and we can't race
5226 * with migration path - PF_EXITING is visible to migration path.
5228 void cgroup_exit(struct task_struct
*tsk
)
5230 struct cgroup_subsys
*ss
;
5231 struct css_set
*cset
;
5232 bool put_cset
= false;
5236 * Unlink from @tsk from its css_set. As migration path can't race
5237 * with us, we can check cg_list without grabbing css_set_rwsem.
5239 if (!list_empty(&tsk
->cg_list
)) {
5240 down_write(&css_set_rwsem
);
5241 list_del_init(&tsk
->cg_list
);
5242 up_write(&css_set_rwsem
);
5246 /* Reassign the task to the init_css_set. */
5247 cset
= task_css_set(tsk
);
5248 RCU_INIT_POINTER(tsk
->cgroups
, &init_css_set
);
5250 if (need_forkexit_callback
) {
5251 /* see cgroup_post_fork() for details */
5252 for_each_subsys(ss
, i
) {
5254 struct cgroup_subsys_state
*old_css
= cset
->subsys
[i
];
5255 struct cgroup_subsys_state
*css
= task_css(tsk
, i
);
5257 ss
->exit(css
, old_css
, tsk
);
5263 put_css_set(cset
, true);
5266 static void check_for_release(struct cgroup
*cgrp
)
5268 if (cgroup_is_releasable(cgrp
) && list_empty(&cgrp
->cset_links
) &&
5269 !css_has_online_children(&cgrp
->self
)) {
5271 * Control Group is currently removeable. If it's not
5272 * already queued for a userspace notification, queue
5275 int need_schedule_work
= 0;
5277 raw_spin_lock(&release_list_lock
);
5278 if (!cgroup_is_dead(cgrp
) &&
5279 list_empty(&cgrp
->release_list
)) {
5280 list_add(&cgrp
->release_list
, &release_list
);
5281 need_schedule_work
= 1;
5283 raw_spin_unlock(&release_list_lock
);
5284 if (need_schedule_work
)
5285 schedule_work(&release_agent_work
);
5290 * Notify userspace when a cgroup is released, by running the
5291 * configured release agent with the name of the cgroup (path
5292 * relative to the root of cgroup file system) as the argument.
5294 * Most likely, this user command will try to rmdir this cgroup.
5296 * This races with the possibility that some other task will be
5297 * attached to this cgroup before it is removed, or that some other
5298 * user task will 'mkdir' a child cgroup of this cgroup. That's ok.
5299 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
5300 * unused, and this cgroup will be reprieved from its death sentence,
5301 * to continue to serve a useful existence. Next time it's released,
5302 * we will get notified again, if it still has 'notify_on_release' set.
5304 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
5305 * means only wait until the task is successfully execve()'d. The
5306 * separate release agent task is forked by call_usermodehelper(),
5307 * then control in this thread returns here, without waiting for the
5308 * release agent task. We don't bother to wait because the caller of
5309 * this routine has no use for the exit status of the release agent
5310 * task, so no sense holding our caller up for that.
5312 static void cgroup_release_agent(struct work_struct
*work
)
5314 BUG_ON(work
!= &release_agent_work
);
5315 mutex_lock(&cgroup_mutex
);
5316 raw_spin_lock(&release_list_lock
);
5317 while (!list_empty(&release_list
)) {
5318 char *argv
[3], *envp
[3];
5320 char *pathbuf
= NULL
, *agentbuf
= NULL
, *path
;
5321 struct cgroup
*cgrp
= list_entry(release_list
.next
,
5324 list_del_init(&cgrp
->release_list
);
5325 raw_spin_unlock(&release_list_lock
);
5326 pathbuf
= kmalloc(PATH_MAX
, GFP_KERNEL
);
5329 path
= cgroup_path(cgrp
, pathbuf
, PATH_MAX
);
5332 agentbuf
= kstrdup(cgrp
->root
->release_agent_path
, GFP_KERNEL
);
5337 argv
[i
++] = agentbuf
;
5342 /* minimal command environment */
5343 envp
[i
++] = "HOME=/";
5344 envp
[i
++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
5347 /* Drop the lock while we invoke the usermode helper,
5348 * since the exec could involve hitting disk and hence
5349 * be a slow process */
5350 mutex_unlock(&cgroup_mutex
);
5351 call_usermodehelper(argv
[0], argv
, envp
, UMH_WAIT_EXEC
);
5352 mutex_lock(&cgroup_mutex
);
5356 raw_spin_lock(&release_list_lock
);
5358 raw_spin_unlock(&release_list_lock
);
5359 mutex_unlock(&cgroup_mutex
);
5362 static int __init
cgroup_disable(char *str
)
5364 struct cgroup_subsys
*ss
;
5368 while ((token
= strsep(&str
, ",")) != NULL
) {
5372 for_each_subsys(ss
, i
) {
5373 if (!strcmp(token
, ss
->name
)) {
5375 printk(KERN_INFO
"Disabling %s control group"
5376 " subsystem\n", ss
->name
);
5383 __setup("cgroup_disable=", cgroup_disable
);
5385 static int __init
cgroup_set_legacy_files_on_dfl(char *str
)
5387 printk("cgroup: using legacy files on the default hierarchy\n");
5388 cgroup_legacy_files_on_dfl
= true;
5391 __setup("cgroup__DEVEL__legacy_files_on_dfl", cgroup_set_legacy_files_on_dfl
);
5394 * css_tryget_online_from_dir - get corresponding css from a cgroup dentry
5395 * @dentry: directory dentry of interest
5396 * @ss: subsystem of interest
5398 * If @dentry is a directory for a cgroup which has @ss enabled on it, try
5399 * to get the corresponding css and return it. If such css doesn't exist
5400 * or can't be pinned, an ERR_PTR value is returned.
5402 struct cgroup_subsys_state
*css_tryget_online_from_dir(struct dentry
*dentry
,
5403 struct cgroup_subsys
*ss
)
5405 struct kernfs_node
*kn
= kernfs_node_from_dentry(dentry
);
5406 struct cgroup_subsys_state
*css
= NULL
;
5407 struct cgroup
*cgrp
;
5409 /* is @dentry a cgroup dir? */
5410 if (dentry
->d_sb
->s_type
!= &cgroup_fs_type
|| !kn
||
5411 kernfs_type(kn
) != KERNFS_DIR
)
5412 return ERR_PTR(-EBADF
);
5417 * This path doesn't originate from kernfs and @kn could already
5418 * have been or be removed at any point. @kn->priv is RCU
5419 * protected for this access. See cgroup_rmdir() for details.
5421 cgrp
= rcu_dereference(kn
->priv
);
5423 css
= cgroup_css(cgrp
, ss
);
5425 if (!css
|| !css_tryget_online(css
))
5426 css
= ERR_PTR(-ENOENT
);
5433 * css_from_id - lookup css by id
5434 * @id: the cgroup id
5435 * @ss: cgroup subsys to be looked into
5437 * Returns the css if there's valid one with @id, otherwise returns NULL.
5438 * Should be called under rcu_read_lock().
5440 struct cgroup_subsys_state
*css_from_id(int id
, struct cgroup_subsys
*ss
)
5442 WARN_ON_ONCE(!rcu_read_lock_held());
5443 return idr_find(&ss
->css_idr
, id
);
5446 #ifdef CONFIG_CGROUP_DEBUG
5447 static struct cgroup_subsys_state
*
5448 debug_css_alloc(struct cgroup_subsys_state
*parent_css
)
5450 struct cgroup_subsys_state
*css
= kzalloc(sizeof(*css
), GFP_KERNEL
);
5453 return ERR_PTR(-ENOMEM
);
5458 static void debug_css_free(struct cgroup_subsys_state
*css
)
5463 static u64
debug_taskcount_read(struct cgroup_subsys_state
*css
,
5466 return cgroup_task_count(css
->cgroup
);
5469 static u64
current_css_set_read(struct cgroup_subsys_state
*css
,
5472 return (u64
)(unsigned long)current
->cgroups
;
5475 static u64
current_css_set_refcount_read(struct cgroup_subsys_state
*css
,
5481 count
= atomic_read(&task_css_set(current
)->refcount
);
5486 static int current_css_set_cg_links_read(struct seq_file
*seq
, void *v
)
5488 struct cgrp_cset_link
*link
;
5489 struct css_set
*cset
;
5492 name_buf
= kmalloc(NAME_MAX
+ 1, GFP_KERNEL
);
5496 down_read(&css_set_rwsem
);
5498 cset
= rcu_dereference(current
->cgroups
);
5499 list_for_each_entry(link
, &cset
->cgrp_links
, cgrp_link
) {
5500 struct cgroup
*c
= link
->cgrp
;
5502 cgroup_name(c
, name_buf
, NAME_MAX
+ 1);
5503 seq_printf(seq
, "Root %d group %s\n",
5504 c
->root
->hierarchy_id
, name_buf
);
5507 up_read(&css_set_rwsem
);
5512 #define MAX_TASKS_SHOWN_PER_CSS 25
5513 static int cgroup_css_links_read(struct seq_file
*seq
, void *v
)
5515 struct cgroup_subsys_state
*css
= seq_css(seq
);
5516 struct cgrp_cset_link
*link
;
5518 down_read(&css_set_rwsem
);
5519 list_for_each_entry(link
, &css
->cgroup
->cset_links
, cset_link
) {
5520 struct css_set
*cset
= link
->cset
;
5521 struct task_struct
*task
;
5524 seq_printf(seq
, "css_set %p\n", cset
);
5526 list_for_each_entry(task
, &cset
->tasks
, cg_list
) {
5527 if (count
++ > MAX_TASKS_SHOWN_PER_CSS
)
5529 seq_printf(seq
, " task %d\n", task_pid_vnr(task
));
5532 list_for_each_entry(task
, &cset
->mg_tasks
, cg_list
) {
5533 if (count
++ > MAX_TASKS_SHOWN_PER_CSS
)
5535 seq_printf(seq
, " task %d\n", task_pid_vnr(task
));
5539 seq_puts(seq
, " ...\n");
5541 up_read(&css_set_rwsem
);
5545 static u64
releasable_read(struct cgroup_subsys_state
*css
, struct cftype
*cft
)
5547 return test_bit(CGRP_RELEASABLE
, &css
->cgroup
->flags
);
5550 static struct cftype debug_files
[] = {
5552 .name
= "taskcount",
5553 .read_u64
= debug_taskcount_read
,
5557 .name
= "current_css_set",
5558 .read_u64
= current_css_set_read
,
5562 .name
= "current_css_set_refcount",
5563 .read_u64
= current_css_set_refcount_read
,
5567 .name
= "current_css_set_cg_links",
5568 .seq_show
= current_css_set_cg_links_read
,
5572 .name
= "cgroup_css_links",
5573 .seq_show
= cgroup_css_links_read
,
5577 .name
= "releasable",
5578 .read_u64
= releasable_read
,
5584 struct cgroup_subsys debug_cgrp_subsys
= {
5585 .css_alloc
= debug_css_alloc
,
5586 .css_free
= debug_css_free
,
5587 .legacy_cftypes
= debug_files
,
5589 #endif /* CONFIG_CGROUP_DEBUG */