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 int rebind_subsystems(struct cgroup_root
*dst_root
,
189 unsigned int ss_mask
);
190 static int cgroup_destroy_locked(struct cgroup
*cgrp
);
191 static int create_css(struct cgroup
*cgrp
, struct cgroup_subsys
*ss
,
193 static void css_release(struct percpu_ref
*ref
);
194 static void kill_css(struct cgroup_subsys_state
*css
);
195 static int cgroup_addrm_files(struct cgroup
*cgrp
, struct cftype cfts
[],
198 /* IDR wrappers which synchronize using cgroup_idr_lock */
199 static int cgroup_idr_alloc(struct idr
*idr
, void *ptr
, int start
, int end
,
204 idr_preload(gfp_mask
);
205 spin_lock_bh(&cgroup_idr_lock
);
206 ret
= idr_alloc(idr
, ptr
, start
, end
, gfp_mask
);
207 spin_unlock_bh(&cgroup_idr_lock
);
212 static void *cgroup_idr_replace(struct idr
*idr
, void *ptr
, int id
)
216 spin_lock_bh(&cgroup_idr_lock
);
217 ret
= idr_replace(idr
, ptr
, id
);
218 spin_unlock_bh(&cgroup_idr_lock
);
222 static void cgroup_idr_remove(struct idr
*idr
, int id
)
224 spin_lock_bh(&cgroup_idr_lock
);
226 spin_unlock_bh(&cgroup_idr_lock
);
229 static struct cgroup
*cgroup_parent(struct cgroup
*cgrp
)
231 struct cgroup_subsys_state
*parent_css
= cgrp
->self
.parent
;
234 return container_of(parent_css
, struct cgroup
, self
);
239 * cgroup_css - obtain a cgroup's css for the specified subsystem
240 * @cgrp: the cgroup of interest
241 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
243 * Return @cgrp's css (cgroup_subsys_state) associated with @ss. This
244 * function must be called either under cgroup_mutex or rcu_read_lock() and
245 * the caller is responsible for pinning the returned css if it wants to
246 * keep accessing it outside the said locks. This function may return
247 * %NULL if @cgrp doesn't have @subsys_id enabled.
249 static struct cgroup_subsys_state
*cgroup_css(struct cgroup
*cgrp
,
250 struct cgroup_subsys
*ss
)
253 return rcu_dereference_check(cgrp
->subsys
[ss
->id
],
254 lockdep_is_held(&cgroup_mutex
));
260 * cgroup_e_css - obtain a cgroup's effective css for the specified subsystem
261 * @cgrp: the cgroup of interest
262 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
264 * Similar to cgroup_css() but returns the effctive css, which is defined
265 * as the matching css of the nearest ancestor including self which has @ss
266 * enabled. If @ss is associated with the hierarchy @cgrp is on, this
267 * function is guaranteed to return non-NULL css.
269 static struct cgroup_subsys_state
*cgroup_e_css(struct cgroup
*cgrp
,
270 struct cgroup_subsys
*ss
)
272 lockdep_assert_held(&cgroup_mutex
);
277 if (!(cgrp
->root
->subsys_mask
& (1 << ss
->id
)))
280 while (cgroup_parent(cgrp
) &&
281 !(cgroup_parent(cgrp
)->child_subsys_mask
& (1 << ss
->id
)))
282 cgrp
= cgroup_parent(cgrp
);
284 return cgroup_css(cgrp
, ss
);
287 /* convenient tests for these bits */
288 static inline bool cgroup_is_dead(const struct cgroup
*cgrp
)
290 return !(cgrp
->self
.flags
& CSS_ONLINE
);
293 struct cgroup_subsys_state
*of_css(struct kernfs_open_file
*of
)
295 struct cgroup
*cgrp
= of
->kn
->parent
->priv
;
296 struct cftype
*cft
= of_cft(of
);
299 * This is open and unprotected implementation of cgroup_css().
300 * seq_css() is only called from a kernfs file operation which has
301 * an active reference on the file. Because all the subsystem
302 * files are drained before a css is disassociated with a cgroup,
303 * the matching css from the cgroup's subsys table is guaranteed to
304 * be and stay valid until the enclosing operation is complete.
307 return rcu_dereference_raw(cgrp
->subsys
[cft
->ss
->id
]);
311 EXPORT_SYMBOL_GPL(of_css
);
314 * cgroup_is_descendant - test ancestry
315 * @cgrp: the cgroup to be tested
316 * @ancestor: possible ancestor of @cgrp
318 * Test whether @cgrp is a descendant of @ancestor. It also returns %true
319 * if @cgrp == @ancestor. This function is safe to call as long as @cgrp
320 * and @ancestor are accessible.
322 bool cgroup_is_descendant(struct cgroup
*cgrp
, struct cgroup
*ancestor
)
325 if (cgrp
== ancestor
)
327 cgrp
= cgroup_parent(cgrp
);
332 static int notify_on_release(const struct cgroup
*cgrp
)
334 return test_bit(CGRP_NOTIFY_ON_RELEASE
, &cgrp
->flags
);
338 * for_each_css - iterate all css's of a cgroup
339 * @css: the iteration cursor
340 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
341 * @cgrp: the target cgroup to iterate css's of
343 * Should be called under cgroup_[tree_]mutex.
345 #define for_each_css(css, ssid, cgrp) \
346 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
347 if (!((css) = rcu_dereference_check( \
348 (cgrp)->subsys[(ssid)], \
349 lockdep_is_held(&cgroup_mutex)))) { } \
353 * for_each_e_css - iterate all effective css's of a cgroup
354 * @css: the iteration cursor
355 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
356 * @cgrp: the target cgroup to iterate css's of
358 * Should be called under cgroup_[tree_]mutex.
360 #define for_each_e_css(css, ssid, cgrp) \
361 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
362 if (!((css) = cgroup_e_css(cgrp, cgroup_subsys[(ssid)]))) \
367 * for_each_subsys - iterate all enabled cgroup subsystems
368 * @ss: the iteration cursor
369 * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
371 #define for_each_subsys(ss, ssid) \
372 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT && \
373 (((ss) = cgroup_subsys[ssid]) || true); (ssid)++)
375 /* iterate across the hierarchies */
376 #define for_each_root(root) \
377 list_for_each_entry((root), &cgroup_roots, root_list)
379 /* iterate over child cgrps, lock should be held throughout iteration */
380 #define cgroup_for_each_live_child(child, cgrp) \
381 list_for_each_entry((child), &(cgrp)->self.children, self.sibling) \
382 if (({ lockdep_assert_held(&cgroup_mutex); \
383 cgroup_is_dead(child); })) \
387 static void cgroup_release_agent(struct work_struct
*work
);
388 static void check_for_release(struct cgroup
*cgrp
);
391 * A cgroup can be associated with multiple css_sets as different tasks may
392 * belong to different cgroups on different hierarchies. In the other
393 * direction, a css_set is naturally associated with multiple cgroups.
394 * This M:N relationship is represented by the following link structure
395 * which exists for each association and allows traversing the associations
398 struct cgrp_cset_link
{
399 /* the cgroup and css_set this link associates */
401 struct css_set
*cset
;
403 /* list of cgrp_cset_links anchored at cgrp->cset_links */
404 struct list_head cset_link
;
406 /* list of cgrp_cset_links anchored at css_set->cgrp_links */
407 struct list_head cgrp_link
;
411 * The default css_set - used by init and its children prior to any
412 * hierarchies being mounted. It contains a pointer to the root state
413 * for each subsystem. Also used to anchor the list of css_sets. Not
414 * reference-counted, to improve performance when child cgroups
415 * haven't been created.
417 struct css_set init_css_set
= {
418 .refcount
= ATOMIC_INIT(1),
419 .cgrp_links
= LIST_HEAD_INIT(init_css_set
.cgrp_links
),
420 .tasks
= LIST_HEAD_INIT(init_css_set
.tasks
),
421 .mg_tasks
= LIST_HEAD_INIT(init_css_set
.mg_tasks
),
422 .mg_preload_node
= LIST_HEAD_INIT(init_css_set
.mg_preload_node
),
423 .mg_node
= LIST_HEAD_INIT(init_css_set
.mg_node
),
426 static int css_set_count
= 1; /* 1 for init_css_set */
429 * cgroup_update_populated - updated populated count of a cgroup
430 * @cgrp: the target cgroup
431 * @populated: inc or dec populated count
433 * @cgrp is either getting the first task (css_set) or losing the last.
434 * Update @cgrp->populated_cnt accordingly. The count is propagated
435 * towards root so that a given cgroup's populated_cnt is zero iff the
436 * cgroup and all its descendants are empty.
438 * @cgrp's interface file "cgroup.populated" is zero if
439 * @cgrp->populated_cnt is zero and 1 otherwise. When @cgrp->populated_cnt
440 * changes from or to zero, userland is notified that the content of the
441 * interface file has changed. This can be used to detect when @cgrp and
442 * its descendants become populated or empty.
444 static void cgroup_update_populated(struct cgroup
*cgrp
, bool populated
)
446 lockdep_assert_held(&css_set_rwsem
);
452 trigger
= !cgrp
->populated_cnt
++;
454 trigger
= !--cgrp
->populated_cnt
;
459 if (cgrp
->populated_kn
)
460 kernfs_notify(cgrp
->populated_kn
);
461 cgrp
= cgroup_parent(cgrp
);
466 * hash table for cgroup groups. This improves the performance to find
467 * an existing css_set. This hash doesn't (currently) take into
468 * account cgroups in empty hierarchies.
470 #define CSS_SET_HASH_BITS 7
471 static DEFINE_HASHTABLE(css_set_table
, CSS_SET_HASH_BITS
);
473 static unsigned long css_set_hash(struct cgroup_subsys_state
*css
[])
475 unsigned long key
= 0UL;
476 struct cgroup_subsys
*ss
;
479 for_each_subsys(ss
, i
)
480 key
+= (unsigned long)css
[i
];
481 key
= (key
>> 16) ^ key
;
486 static void put_css_set_locked(struct css_set
*cset
)
488 struct cgrp_cset_link
*link
, *tmp_link
;
489 struct cgroup_subsys
*ss
;
492 lockdep_assert_held(&css_set_rwsem
);
494 if (!atomic_dec_and_test(&cset
->refcount
))
497 /* This css_set is dead. unlink it and release cgroup refcounts */
498 for_each_subsys(ss
, ssid
)
499 list_del(&cset
->e_cset_node
[ssid
]);
500 hash_del(&cset
->hlist
);
503 list_for_each_entry_safe(link
, tmp_link
, &cset
->cgrp_links
, cgrp_link
) {
504 struct cgroup
*cgrp
= link
->cgrp
;
506 list_del(&link
->cset_link
);
507 list_del(&link
->cgrp_link
);
509 /* @cgrp can't go away while we're holding css_set_rwsem */
510 if (list_empty(&cgrp
->cset_links
)) {
511 cgroup_update_populated(cgrp
, false);
512 check_for_release(cgrp
);
518 kfree_rcu(cset
, rcu_head
);
521 static void put_css_set(struct css_set
*cset
)
524 * Ensure that the refcount doesn't hit zero while any readers
525 * can see it. Similar to atomic_dec_and_lock(), but for an
528 if (atomic_add_unless(&cset
->refcount
, -1, 1))
531 down_write(&css_set_rwsem
);
532 put_css_set_locked(cset
);
533 up_write(&css_set_rwsem
);
537 * refcounted get/put for css_set objects
539 static inline void get_css_set(struct css_set
*cset
)
541 atomic_inc(&cset
->refcount
);
545 * compare_css_sets - helper function for find_existing_css_set().
546 * @cset: candidate css_set being tested
547 * @old_cset: existing css_set for a task
548 * @new_cgrp: cgroup that's being entered by the task
549 * @template: desired set of css pointers in css_set (pre-calculated)
551 * Returns true if "cset" matches "old_cset" except for the hierarchy
552 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
554 static bool compare_css_sets(struct css_set
*cset
,
555 struct css_set
*old_cset
,
556 struct cgroup
*new_cgrp
,
557 struct cgroup_subsys_state
*template[])
559 struct list_head
*l1
, *l2
;
562 * On the default hierarchy, there can be csets which are
563 * associated with the same set of cgroups but different csses.
564 * Let's first ensure that csses match.
566 if (memcmp(template, cset
->subsys
, sizeof(cset
->subsys
)))
570 * Compare cgroup pointers in order to distinguish between
571 * different cgroups in hierarchies. As different cgroups may
572 * share the same effective css, this comparison is always
575 l1
= &cset
->cgrp_links
;
576 l2
= &old_cset
->cgrp_links
;
578 struct cgrp_cset_link
*link1
, *link2
;
579 struct cgroup
*cgrp1
, *cgrp2
;
583 /* See if we reached the end - both lists are equal length. */
584 if (l1
== &cset
->cgrp_links
) {
585 BUG_ON(l2
!= &old_cset
->cgrp_links
);
588 BUG_ON(l2
== &old_cset
->cgrp_links
);
590 /* Locate the cgroups associated with these links. */
591 link1
= list_entry(l1
, struct cgrp_cset_link
, cgrp_link
);
592 link2
= list_entry(l2
, struct cgrp_cset_link
, cgrp_link
);
595 /* Hierarchies should be linked in the same order. */
596 BUG_ON(cgrp1
->root
!= cgrp2
->root
);
599 * If this hierarchy is the hierarchy of the cgroup
600 * that's changing, then we need to check that this
601 * css_set points to the new cgroup; if it's any other
602 * hierarchy, then this css_set should point to the
603 * same cgroup as the old css_set.
605 if (cgrp1
->root
== new_cgrp
->root
) {
606 if (cgrp1
!= new_cgrp
)
617 * find_existing_css_set - init css array and find the matching css_set
618 * @old_cset: the css_set that we're using before the cgroup transition
619 * @cgrp: the cgroup that we're moving into
620 * @template: out param for the new set of csses, should be clear on entry
622 static struct css_set
*find_existing_css_set(struct css_set
*old_cset
,
624 struct cgroup_subsys_state
*template[])
626 struct cgroup_root
*root
= cgrp
->root
;
627 struct cgroup_subsys
*ss
;
628 struct css_set
*cset
;
633 * Build the set of subsystem state objects that we want to see in the
634 * new css_set. while subsystems can change globally, the entries here
635 * won't change, so no need for locking.
637 for_each_subsys(ss
, i
) {
638 if (root
->subsys_mask
& (1UL << i
)) {
640 * @ss is in this hierarchy, so we want the
641 * effective css from @cgrp.
643 template[i
] = cgroup_e_css(cgrp
, ss
);
646 * @ss is not in this hierarchy, so we don't want
649 template[i
] = old_cset
->subsys
[i
];
653 key
= css_set_hash(template);
654 hash_for_each_possible(css_set_table
, cset
, hlist
, key
) {
655 if (!compare_css_sets(cset
, old_cset
, cgrp
, template))
658 /* This css_set matches what we need */
662 /* No existing cgroup group matched */
666 static void free_cgrp_cset_links(struct list_head
*links_to_free
)
668 struct cgrp_cset_link
*link
, *tmp_link
;
670 list_for_each_entry_safe(link
, tmp_link
, links_to_free
, cset_link
) {
671 list_del(&link
->cset_link
);
677 * allocate_cgrp_cset_links - allocate cgrp_cset_links
678 * @count: the number of links to allocate
679 * @tmp_links: list_head the allocated links are put on
681 * Allocate @count cgrp_cset_link structures and chain them on @tmp_links
682 * through ->cset_link. Returns 0 on success or -errno.
684 static int allocate_cgrp_cset_links(int count
, struct list_head
*tmp_links
)
686 struct cgrp_cset_link
*link
;
689 INIT_LIST_HEAD(tmp_links
);
691 for (i
= 0; i
< count
; i
++) {
692 link
= kzalloc(sizeof(*link
), GFP_KERNEL
);
694 free_cgrp_cset_links(tmp_links
);
697 list_add(&link
->cset_link
, tmp_links
);
703 * link_css_set - a helper function to link a css_set to a cgroup
704 * @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()
705 * @cset: the css_set to be linked
706 * @cgrp: the destination cgroup
708 static void link_css_set(struct list_head
*tmp_links
, struct css_set
*cset
,
711 struct cgrp_cset_link
*link
;
713 BUG_ON(list_empty(tmp_links
));
715 if (cgroup_on_dfl(cgrp
))
716 cset
->dfl_cgrp
= cgrp
;
718 link
= list_first_entry(tmp_links
, struct cgrp_cset_link
, cset_link
);
722 if (list_empty(&cgrp
->cset_links
))
723 cgroup_update_populated(cgrp
, true);
724 list_move(&link
->cset_link
, &cgrp
->cset_links
);
727 * Always add links to the tail of the list so that the list
728 * is sorted by order of hierarchy creation
730 list_add_tail(&link
->cgrp_link
, &cset
->cgrp_links
);
734 * find_css_set - return a new css_set with one cgroup updated
735 * @old_cset: the baseline css_set
736 * @cgrp: the cgroup to be updated
738 * Return a new css_set that's equivalent to @old_cset, but with @cgrp
739 * substituted into the appropriate hierarchy.
741 static struct css_set
*find_css_set(struct css_set
*old_cset
,
744 struct cgroup_subsys_state
*template[CGROUP_SUBSYS_COUNT
] = { };
745 struct css_set
*cset
;
746 struct list_head tmp_links
;
747 struct cgrp_cset_link
*link
;
748 struct cgroup_subsys
*ss
;
752 lockdep_assert_held(&cgroup_mutex
);
754 /* First see if we already have a cgroup group that matches
756 down_read(&css_set_rwsem
);
757 cset
= find_existing_css_set(old_cset
, cgrp
, template);
760 up_read(&css_set_rwsem
);
765 cset
= kzalloc(sizeof(*cset
), GFP_KERNEL
);
769 /* Allocate all the cgrp_cset_link objects that we'll need */
770 if (allocate_cgrp_cset_links(cgroup_root_count
, &tmp_links
) < 0) {
775 atomic_set(&cset
->refcount
, 1);
776 INIT_LIST_HEAD(&cset
->cgrp_links
);
777 INIT_LIST_HEAD(&cset
->tasks
);
778 INIT_LIST_HEAD(&cset
->mg_tasks
);
779 INIT_LIST_HEAD(&cset
->mg_preload_node
);
780 INIT_LIST_HEAD(&cset
->mg_node
);
781 INIT_HLIST_NODE(&cset
->hlist
);
783 /* Copy the set of subsystem state objects generated in
784 * find_existing_css_set() */
785 memcpy(cset
->subsys
, template, sizeof(cset
->subsys
));
787 down_write(&css_set_rwsem
);
788 /* Add reference counts and links from the new css_set. */
789 list_for_each_entry(link
, &old_cset
->cgrp_links
, cgrp_link
) {
790 struct cgroup
*c
= link
->cgrp
;
792 if (c
->root
== cgrp
->root
)
794 link_css_set(&tmp_links
, cset
, c
);
797 BUG_ON(!list_empty(&tmp_links
));
801 /* Add @cset to the hash table */
802 key
= css_set_hash(cset
->subsys
);
803 hash_add(css_set_table
, &cset
->hlist
, key
);
805 for_each_subsys(ss
, ssid
)
806 list_add_tail(&cset
->e_cset_node
[ssid
],
807 &cset
->subsys
[ssid
]->cgroup
->e_csets
[ssid
]);
809 up_write(&css_set_rwsem
);
814 static struct cgroup_root
*cgroup_root_from_kf(struct kernfs_root
*kf_root
)
816 struct cgroup
*root_cgrp
= kf_root
->kn
->priv
;
818 return root_cgrp
->root
;
821 static int cgroup_init_root_id(struct cgroup_root
*root
)
825 lockdep_assert_held(&cgroup_mutex
);
827 id
= idr_alloc_cyclic(&cgroup_hierarchy_idr
, root
, 0, 0, GFP_KERNEL
);
831 root
->hierarchy_id
= id
;
835 static void cgroup_exit_root_id(struct cgroup_root
*root
)
837 lockdep_assert_held(&cgroup_mutex
);
839 if (root
->hierarchy_id
) {
840 idr_remove(&cgroup_hierarchy_idr
, root
->hierarchy_id
);
841 root
->hierarchy_id
= 0;
845 static void cgroup_free_root(struct cgroup_root
*root
)
848 /* hierarhcy ID shoulid already have been released */
849 WARN_ON_ONCE(root
->hierarchy_id
);
851 idr_destroy(&root
->cgroup_idr
);
856 static void cgroup_destroy_root(struct cgroup_root
*root
)
858 struct cgroup
*cgrp
= &root
->cgrp
;
859 struct cgrp_cset_link
*link
, *tmp_link
;
861 mutex_lock(&cgroup_mutex
);
863 BUG_ON(atomic_read(&root
->nr_cgrps
));
864 BUG_ON(!list_empty(&cgrp
->self
.children
));
866 /* Rebind all subsystems back to the default hierarchy */
867 rebind_subsystems(&cgrp_dfl_root
, root
->subsys_mask
);
870 * Release all the links from cset_links to this hierarchy's
873 down_write(&css_set_rwsem
);
875 list_for_each_entry_safe(link
, tmp_link
, &cgrp
->cset_links
, cset_link
) {
876 list_del(&link
->cset_link
);
877 list_del(&link
->cgrp_link
);
880 up_write(&css_set_rwsem
);
882 if (!list_empty(&root
->root_list
)) {
883 list_del(&root
->root_list
);
887 cgroup_exit_root_id(root
);
889 mutex_unlock(&cgroup_mutex
);
891 kernfs_destroy_root(root
->kf_root
);
892 cgroup_free_root(root
);
895 /* look up cgroup associated with given css_set on the specified hierarchy */
896 static struct cgroup
*cset_cgroup_from_root(struct css_set
*cset
,
897 struct cgroup_root
*root
)
899 struct cgroup
*res
= NULL
;
901 lockdep_assert_held(&cgroup_mutex
);
902 lockdep_assert_held(&css_set_rwsem
);
904 if (cset
== &init_css_set
) {
907 struct cgrp_cset_link
*link
;
909 list_for_each_entry(link
, &cset
->cgrp_links
, cgrp_link
) {
910 struct cgroup
*c
= link
->cgrp
;
912 if (c
->root
== root
) {
924 * Return the cgroup for "task" from the given hierarchy. Must be
925 * called with cgroup_mutex and css_set_rwsem held.
927 static struct cgroup
*task_cgroup_from_root(struct task_struct
*task
,
928 struct cgroup_root
*root
)
931 * No need to lock the task - since we hold cgroup_mutex the
932 * task can't change groups, so the only thing that can happen
933 * is that it exits and its css is set back to init_css_set.
935 return cset_cgroup_from_root(task_css_set(task
), root
);
939 * A task must hold cgroup_mutex to modify cgroups.
941 * Any task can increment and decrement the count field without lock.
942 * So in general, code holding cgroup_mutex can't rely on the count
943 * field not changing. However, if the count goes to zero, then only
944 * cgroup_attach_task() can increment it again. Because a count of zero
945 * means that no tasks are currently attached, therefore there is no
946 * way a task attached to that cgroup can fork (the other way to
947 * increment the count). So code holding cgroup_mutex can safely
948 * assume that if the count is zero, it will stay zero. Similarly, if
949 * a task holds cgroup_mutex on a cgroup with zero count, it
950 * knows that the cgroup won't be removed, as cgroup_rmdir()
953 * A cgroup can only be deleted if both its 'count' of using tasks
954 * is zero, and its list of 'children' cgroups is empty. Since all
955 * tasks in the system use _some_ cgroup, and since there is always at
956 * least one task in the system (init, pid == 1), therefore, root cgroup
957 * always has either children cgroups and/or using tasks. So we don't
958 * need a special hack to ensure that root cgroup cannot be deleted.
960 * P.S. One more locking exception. RCU is used to guard the
961 * update of a tasks cgroup pointer by cgroup_attach_task()
964 static int cgroup_populate_dir(struct cgroup
*cgrp
, unsigned int subsys_mask
);
965 static struct kernfs_syscall_ops cgroup_kf_syscall_ops
;
966 static const struct file_operations proc_cgroupstats_operations
;
968 static char *cgroup_file_name(struct cgroup
*cgrp
, const struct cftype
*cft
,
971 if (cft
->ss
&& !(cft
->flags
& CFTYPE_NO_PREFIX
) &&
972 !(cgrp
->root
->flags
& CGRP_ROOT_NOPREFIX
))
973 snprintf(buf
, CGROUP_FILE_NAME_MAX
, "%s.%s",
974 cft
->ss
->name
, cft
->name
);
976 strncpy(buf
, cft
->name
, CGROUP_FILE_NAME_MAX
);
981 * cgroup_file_mode - deduce file mode of a control file
982 * @cft: the control file in question
984 * returns cft->mode if ->mode is not 0
985 * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
986 * returns S_IRUGO if it has only a read handler
987 * returns S_IWUSR if it has only a write hander
989 static umode_t
cgroup_file_mode(const struct cftype
*cft
)
996 if (cft
->read_u64
|| cft
->read_s64
|| cft
->seq_show
)
999 if (cft
->write_u64
|| cft
->write_s64
|| cft
->write
)
1005 static void cgroup_get(struct cgroup
*cgrp
)
1007 WARN_ON_ONCE(cgroup_is_dead(cgrp
));
1008 css_get(&cgrp
->self
);
1011 static bool cgroup_tryget(struct cgroup
*cgrp
)
1013 return css_tryget(&cgrp
->self
);
1016 static void cgroup_put(struct cgroup
*cgrp
)
1018 css_put(&cgrp
->self
);
1022 * cgroup_calc_child_subsys_mask - calculate child_subsys_mask
1023 * @cgrp: the target cgroup
1024 * @subtree_control: the new subtree_control mask to consider
1026 * On the default hierarchy, a subsystem may request other subsystems to be
1027 * enabled together through its ->depends_on mask. In such cases, more
1028 * subsystems than specified in "cgroup.subtree_control" may be enabled.
1030 * This function calculates which subsystems need to be enabled if
1031 * @subtree_control is to be applied to @cgrp. The returned mask is always
1032 * a superset of @subtree_control and follows the usual hierarchy rules.
1034 static unsigned int cgroup_calc_child_subsys_mask(struct cgroup
*cgrp
,
1035 unsigned int subtree_control
)
1037 struct cgroup
*parent
= cgroup_parent(cgrp
);
1038 unsigned int cur_ss_mask
= subtree_control
;
1039 struct cgroup_subsys
*ss
;
1042 lockdep_assert_held(&cgroup_mutex
);
1044 if (!cgroup_on_dfl(cgrp
))
1048 unsigned int new_ss_mask
= cur_ss_mask
;
1050 for_each_subsys(ss
, ssid
)
1051 if (cur_ss_mask
& (1 << ssid
))
1052 new_ss_mask
|= ss
->depends_on
;
1055 * Mask out subsystems which aren't available. This can
1056 * happen only if some depended-upon subsystems were bound
1057 * to non-default hierarchies.
1060 new_ss_mask
&= parent
->child_subsys_mask
;
1062 new_ss_mask
&= cgrp
->root
->subsys_mask
;
1064 if (new_ss_mask
== cur_ss_mask
)
1066 cur_ss_mask
= new_ss_mask
;
1073 * cgroup_refresh_child_subsys_mask - update child_subsys_mask
1074 * @cgrp: the target cgroup
1076 * Update @cgrp->child_subsys_mask according to the current
1077 * @cgrp->subtree_control using cgroup_calc_child_subsys_mask().
1079 static void cgroup_refresh_child_subsys_mask(struct cgroup
*cgrp
)
1081 cgrp
->child_subsys_mask
=
1082 cgroup_calc_child_subsys_mask(cgrp
, cgrp
->subtree_control
);
1086 * cgroup_kn_unlock - unlocking helper for cgroup kernfs methods
1087 * @kn: the kernfs_node being serviced
1089 * This helper undoes cgroup_kn_lock_live() and should be invoked before
1090 * the method finishes if locking succeeded. Note that once this function
1091 * returns the cgroup returned by cgroup_kn_lock_live() may become
1092 * inaccessible any time. If the caller intends to continue to access the
1093 * cgroup, it should pin it before invoking this function.
1095 static void cgroup_kn_unlock(struct kernfs_node
*kn
)
1097 struct cgroup
*cgrp
;
1099 if (kernfs_type(kn
) == KERNFS_DIR
)
1102 cgrp
= kn
->parent
->priv
;
1104 mutex_unlock(&cgroup_mutex
);
1106 kernfs_unbreak_active_protection(kn
);
1111 * cgroup_kn_lock_live - locking helper for cgroup kernfs methods
1112 * @kn: the kernfs_node being serviced
1114 * This helper is to be used by a cgroup kernfs method currently servicing
1115 * @kn. It breaks the active protection, performs cgroup locking and
1116 * verifies that the associated cgroup is alive. Returns the cgroup if
1117 * alive; otherwise, %NULL. A successful return should be undone by a
1118 * matching cgroup_kn_unlock() invocation.
1120 * Any cgroup kernfs method implementation which requires locking the
1121 * associated cgroup should use this helper. It avoids nesting cgroup
1122 * locking under kernfs active protection and allows all kernfs operations
1123 * including self-removal.
1125 static struct cgroup
*cgroup_kn_lock_live(struct kernfs_node
*kn
)
1127 struct cgroup
*cgrp
;
1129 if (kernfs_type(kn
) == KERNFS_DIR
)
1132 cgrp
= kn
->parent
->priv
;
1135 * We're gonna grab cgroup_mutex which nests outside kernfs
1136 * active_ref. cgroup liveliness check alone provides enough
1137 * protection against removal. Ensure @cgrp stays accessible and
1138 * break the active_ref protection.
1140 if (!cgroup_tryget(cgrp
))
1142 kernfs_break_active_protection(kn
);
1144 mutex_lock(&cgroup_mutex
);
1146 if (!cgroup_is_dead(cgrp
))
1149 cgroup_kn_unlock(kn
);
1153 static void cgroup_rm_file(struct cgroup
*cgrp
, const struct cftype
*cft
)
1155 char name
[CGROUP_FILE_NAME_MAX
];
1157 lockdep_assert_held(&cgroup_mutex
);
1158 kernfs_remove_by_name(cgrp
->kn
, cgroup_file_name(cgrp
, cft
, name
));
1162 * cgroup_clear_dir - remove subsys files in a cgroup directory
1163 * @cgrp: target cgroup
1164 * @subsys_mask: mask of the subsystem ids whose files should be removed
1166 static void cgroup_clear_dir(struct cgroup
*cgrp
, unsigned int subsys_mask
)
1168 struct cgroup_subsys
*ss
;
1171 for_each_subsys(ss
, i
) {
1172 struct cftype
*cfts
;
1174 if (!(subsys_mask
& (1 << i
)))
1176 list_for_each_entry(cfts
, &ss
->cfts
, node
)
1177 cgroup_addrm_files(cgrp
, cfts
, false);
1181 static int rebind_subsystems(struct cgroup_root
*dst_root
, unsigned int ss_mask
)
1183 struct cgroup_subsys
*ss
;
1184 unsigned int tmp_ss_mask
;
1187 lockdep_assert_held(&cgroup_mutex
);
1189 for_each_subsys(ss
, ssid
) {
1190 if (!(ss_mask
& (1 << ssid
)))
1193 /* if @ss has non-root csses attached to it, can't move */
1194 if (css_next_child(NULL
, cgroup_css(&ss
->root
->cgrp
, ss
)))
1197 /* can't move between two non-dummy roots either */
1198 if (ss
->root
!= &cgrp_dfl_root
&& dst_root
!= &cgrp_dfl_root
)
1202 /* skip creating root files on dfl_root for inhibited subsystems */
1203 tmp_ss_mask
= ss_mask
;
1204 if (dst_root
== &cgrp_dfl_root
)
1205 tmp_ss_mask
&= ~cgrp_dfl_root_inhibit_ss_mask
;
1207 ret
= cgroup_populate_dir(&dst_root
->cgrp
, tmp_ss_mask
);
1209 if (dst_root
!= &cgrp_dfl_root
)
1213 * Rebinding back to the default root is not allowed to
1214 * fail. Using both default and non-default roots should
1215 * be rare. Moving subsystems back and forth even more so.
1216 * Just warn about it and continue.
1218 if (cgrp_dfl_root_visible
) {
1219 pr_warn("failed to create files (%d) while rebinding 0x%x to default root\n",
1221 pr_warn("you may retry by moving them to a different hierarchy and unbinding\n");
1226 * Nothing can fail from this point on. Remove files for the
1227 * removed subsystems and rebind each subsystem.
1229 for_each_subsys(ss
, ssid
)
1230 if (ss_mask
& (1 << ssid
))
1231 cgroup_clear_dir(&ss
->root
->cgrp
, 1 << ssid
);
1233 for_each_subsys(ss
, ssid
) {
1234 struct cgroup_root
*src_root
;
1235 struct cgroup_subsys_state
*css
;
1236 struct css_set
*cset
;
1238 if (!(ss_mask
& (1 << ssid
)))
1241 src_root
= ss
->root
;
1242 css
= cgroup_css(&src_root
->cgrp
, ss
);
1244 WARN_ON(!css
|| cgroup_css(&dst_root
->cgrp
, ss
));
1246 RCU_INIT_POINTER(src_root
->cgrp
.subsys
[ssid
], NULL
);
1247 rcu_assign_pointer(dst_root
->cgrp
.subsys
[ssid
], css
);
1248 ss
->root
= dst_root
;
1249 css
->cgroup
= &dst_root
->cgrp
;
1251 down_write(&css_set_rwsem
);
1252 hash_for_each(css_set_table
, i
, cset
, hlist
)
1253 list_move_tail(&cset
->e_cset_node
[ss
->id
],
1254 &dst_root
->cgrp
.e_csets
[ss
->id
]);
1255 up_write(&css_set_rwsem
);
1257 src_root
->subsys_mask
&= ~(1 << ssid
);
1258 src_root
->cgrp
.subtree_control
&= ~(1 << ssid
);
1259 cgroup_refresh_child_subsys_mask(&src_root
->cgrp
);
1261 /* default hierarchy doesn't enable controllers by default */
1262 dst_root
->subsys_mask
|= 1 << ssid
;
1263 if (dst_root
!= &cgrp_dfl_root
) {
1264 dst_root
->cgrp
.subtree_control
|= 1 << ssid
;
1265 cgroup_refresh_child_subsys_mask(&dst_root
->cgrp
);
1272 kernfs_activate(dst_root
->cgrp
.kn
);
1276 static int cgroup_show_options(struct seq_file
*seq
,
1277 struct kernfs_root
*kf_root
)
1279 struct cgroup_root
*root
= cgroup_root_from_kf(kf_root
);
1280 struct cgroup_subsys
*ss
;
1283 for_each_subsys(ss
, ssid
)
1284 if (root
->subsys_mask
& (1 << ssid
))
1285 seq_printf(seq
, ",%s", ss
->name
);
1286 if (root
->flags
& CGRP_ROOT_NOPREFIX
)
1287 seq_puts(seq
, ",noprefix");
1288 if (root
->flags
& CGRP_ROOT_XATTR
)
1289 seq_puts(seq
, ",xattr");
1291 spin_lock(&release_agent_path_lock
);
1292 if (strlen(root
->release_agent_path
))
1293 seq_printf(seq
, ",release_agent=%s", root
->release_agent_path
);
1294 spin_unlock(&release_agent_path_lock
);
1296 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN
, &root
->cgrp
.flags
))
1297 seq_puts(seq
, ",clone_children");
1298 if (strlen(root
->name
))
1299 seq_printf(seq
, ",name=%s", root
->name
);
1303 struct cgroup_sb_opts
{
1304 unsigned int subsys_mask
;
1306 char *release_agent
;
1307 bool cpuset_clone_children
;
1309 /* User explicitly requested empty subsystem */
1313 static int parse_cgroupfs_options(char *data
, struct cgroup_sb_opts
*opts
)
1315 char *token
, *o
= data
;
1316 bool all_ss
= false, one_ss
= false;
1317 unsigned int mask
= -1U;
1318 struct cgroup_subsys
*ss
;
1322 #ifdef CONFIG_CPUSETS
1323 mask
= ~(1U << cpuset_cgrp_id
);
1326 memset(opts
, 0, sizeof(*opts
));
1328 while ((token
= strsep(&o
, ",")) != NULL
) {
1333 if (!strcmp(token
, "none")) {
1334 /* Explicitly have no subsystems */
1338 if (!strcmp(token
, "all")) {
1339 /* Mutually exclusive option 'all' + subsystem name */
1345 if (!strcmp(token
, "__DEVEL__sane_behavior")) {
1346 opts
->flags
|= CGRP_ROOT_SANE_BEHAVIOR
;
1349 if (!strcmp(token
, "noprefix")) {
1350 opts
->flags
|= CGRP_ROOT_NOPREFIX
;
1353 if (!strcmp(token
, "clone_children")) {
1354 opts
->cpuset_clone_children
= true;
1357 if (!strcmp(token
, "xattr")) {
1358 opts
->flags
|= CGRP_ROOT_XATTR
;
1361 if (!strncmp(token
, "release_agent=", 14)) {
1362 /* Specifying two release agents is forbidden */
1363 if (opts
->release_agent
)
1365 opts
->release_agent
=
1366 kstrndup(token
+ 14, PATH_MAX
- 1, GFP_KERNEL
);
1367 if (!opts
->release_agent
)
1371 if (!strncmp(token
, "name=", 5)) {
1372 const char *name
= token
+ 5;
1373 /* Can't specify an empty name */
1376 /* Must match [\w.-]+ */
1377 for (i
= 0; i
< strlen(name
); i
++) {
1381 if ((c
== '.') || (c
== '-') || (c
== '_'))
1385 /* Specifying two names is forbidden */
1388 opts
->name
= kstrndup(name
,
1389 MAX_CGROUP_ROOT_NAMELEN
- 1,
1397 for_each_subsys(ss
, i
) {
1398 if (strcmp(token
, ss
->name
))
1403 /* Mutually exclusive option 'all' + subsystem name */
1406 opts
->subsys_mask
|= (1 << i
);
1411 if (i
== CGROUP_SUBSYS_COUNT
)
1415 if (opts
->flags
& CGRP_ROOT_SANE_BEHAVIOR
) {
1416 pr_warn("sane_behavior: this is still under development and its behaviors will change, proceed at your own risk\n");
1418 pr_err("sane_behavior: no other mount options allowed\n");
1425 * If the 'all' option was specified select all the subsystems,
1426 * otherwise if 'none', 'name=' and a subsystem name options were
1427 * not specified, let's default to 'all'
1429 if (all_ss
|| (!one_ss
&& !opts
->none
&& !opts
->name
))
1430 for_each_subsys(ss
, i
)
1432 opts
->subsys_mask
|= (1 << i
);
1435 * We either have to specify by name or by subsystems. (So all
1436 * empty hierarchies must have a name).
1438 if (!opts
->subsys_mask
&& !opts
->name
)
1442 * Option noprefix was introduced just for backward compatibility
1443 * with the old cpuset, so we allow noprefix only if mounting just
1444 * the cpuset subsystem.
1446 if ((opts
->flags
& CGRP_ROOT_NOPREFIX
) && (opts
->subsys_mask
& mask
))
1449 /* Can't specify "none" and some subsystems */
1450 if (opts
->subsys_mask
&& opts
->none
)
1456 static int cgroup_remount(struct kernfs_root
*kf_root
, int *flags
, char *data
)
1459 struct cgroup_root
*root
= cgroup_root_from_kf(kf_root
);
1460 struct cgroup_sb_opts opts
;
1461 unsigned int added_mask
, removed_mask
;
1463 if (root
== &cgrp_dfl_root
) {
1464 pr_err("remount is not allowed\n");
1468 mutex_lock(&cgroup_mutex
);
1470 /* See what subsystems are wanted */
1471 ret
= parse_cgroupfs_options(data
, &opts
);
1475 if (opts
.subsys_mask
!= root
->subsys_mask
|| opts
.release_agent
)
1476 pr_warn("option changes via remount are deprecated (pid=%d comm=%s)\n",
1477 task_tgid_nr(current
), current
->comm
);
1479 added_mask
= opts
.subsys_mask
& ~root
->subsys_mask
;
1480 removed_mask
= root
->subsys_mask
& ~opts
.subsys_mask
;
1482 /* Don't allow flags or name to change at remount */
1483 if ((opts
.flags
^ root
->flags
) ||
1484 (opts
.name
&& strcmp(opts
.name
, root
->name
))) {
1485 pr_err("option or name mismatch, new: 0x%x \"%s\", old: 0x%x \"%s\"\n",
1486 opts
.flags
, opts
.name
?: "", root
->flags
, root
->name
);
1491 /* remounting is not allowed for populated hierarchies */
1492 if (!list_empty(&root
->cgrp
.self
.children
)) {
1497 ret
= rebind_subsystems(root
, added_mask
);
1501 rebind_subsystems(&cgrp_dfl_root
, removed_mask
);
1503 if (opts
.release_agent
) {
1504 spin_lock(&release_agent_path_lock
);
1505 strcpy(root
->release_agent_path
, opts
.release_agent
);
1506 spin_unlock(&release_agent_path_lock
);
1509 kfree(opts
.release_agent
);
1511 mutex_unlock(&cgroup_mutex
);
1516 * To reduce the fork() overhead for systems that are not actually using
1517 * their cgroups capability, we don't maintain the lists running through
1518 * each css_set to its tasks until we see the list actually used - in other
1519 * words after the first mount.
1521 static bool use_task_css_set_links __read_mostly
;
1523 static void cgroup_enable_task_cg_lists(void)
1525 struct task_struct
*p
, *g
;
1527 down_write(&css_set_rwsem
);
1529 if (use_task_css_set_links
)
1532 use_task_css_set_links
= true;
1535 * We need tasklist_lock because RCU is not safe against
1536 * while_each_thread(). Besides, a forking task that has passed
1537 * cgroup_post_fork() without seeing use_task_css_set_links = 1
1538 * is not guaranteed to have its child immediately visible in the
1539 * tasklist if we walk through it with RCU.
1541 read_lock(&tasklist_lock
);
1542 do_each_thread(g
, p
) {
1543 WARN_ON_ONCE(!list_empty(&p
->cg_list
) ||
1544 task_css_set(p
) != &init_css_set
);
1547 * We should check if the process is exiting, otherwise
1548 * it will race with cgroup_exit() in that the list
1549 * entry won't be deleted though the process has exited.
1550 * Do it while holding siglock so that we don't end up
1551 * racing against cgroup_exit().
1553 spin_lock_irq(&p
->sighand
->siglock
);
1554 if (!(p
->flags
& PF_EXITING
)) {
1555 struct css_set
*cset
= task_css_set(p
);
1557 list_add(&p
->cg_list
, &cset
->tasks
);
1560 spin_unlock_irq(&p
->sighand
->siglock
);
1561 } while_each_thread(g
, p
);
1562 read_unlock(&tasklist_lock
);
1564 up_write(&css_set_rwsem
);
1567 static void init_cgroup_housekeeping(struct cgroup
*cgrp
)
1569 struct cgroup_subsys
*ss
;
1572 INIT_LIST_HEAD(&cgrp
->self
.sibling
);
1573 INIT_LIST_HEAD(&cgrp
->self
.children
);
1574 INIT_LIST_HEAD(&cgrp
->cset_links
);
1575 INIT_LIST_HEAD(&cgrp
->pidlists
);
1576 mutex_init(&cgrp
->pidlist_mutex
);
1577 cgrp
->self
.cgroup
= cgrp
;
1578 cgrp
->self
.flags
|= CSS_ONLINE
;
1580 for_each_subsys(ss
, ssid
)
1581 INIT_LIST_HEAD(&cgrp
->e_csets
[ssid
]);
1583 init_waitqueue_head(&cgrp
->offline_waitq
);
1584 INIT_WORK(&cgrp
->release_agent_work
, cgroup_release_agent
);
1587 static void init_cgroup_root(struct cgroup_root
*root
,
1588 struct cgroup_sb_opts
*opts
)
1590 struct cgroup
*cgrp
= &root
->cgrp
;
1592 INIT_LIST_HEAD(&root
->root_list
);
1593 atomic_set(&root
->nr_cgrps
, 1);
1595 init_cgroup_housekeeping(cgrp
);
1596 idr_init(&root
->cgroup_idr
);
1598 root
->flags
= opts
->flags
;
1599 if (opts
->release_agent
)
1600 strcpy(root
->release_agent_path
, opts
->release_agent
);
1602 strcpy(root
->name
, opts
->name
);
1603 if (opts
->cpuset_clone_children
)
1604 set_bit(CGRP_CPUSET_CLONE_CHILDREN
, &root
->cgrp
.flags
);
1607 static int cgroup_setup_root(struct cgroup_root
*root
, unsigned int ss_mask
)
1609 LIST_HEAD(tmp_links
);
1610 struct cgroup
*root_cgrp
= &root
->cgrp
;
1611 struct cftype
*base_files
;
1612 struct css_set
*cset
;
1615 lockdep_assert_held(&cgroup_mutex
);
1617 ret
= cgroup_idr_alloc(&root
->cgroup_idr
, root_cgrp
, 1, 2, GFP_NOWAIT
);
1620 root_cgrp
->id
= ret
;
1622 ret
= percpu_ref_init(&root_cgrp
->self
.refcnt
, css_release
, 0,
1628 * We're accessing css_set_count without locking css_set_rwsem here,
1629 * but that's OK - it can only be increased by someone holding
1630 * cgroup_lock, and that's us. The worst that can happen is that we
1631 * have some link structures left over
1633 ret
= allocate_cgrp_cset_links(css_set_count
, &tmp_links
);
1637 ret
= cgroup_init_root_id(root
);
1641 root
->kf_root
= kernfs_create_root(&cgroup_kf_syscall_ops
,
1642 KERNFS_ROOT_CREATE_DEACTIVATED
,
1644 if (IS_ERR(root
->kf_root
)) {
1645 ret
= PTR_ERR(root
->kf_root
);
1648 root_cgrp
->kn
= root
->kf_root
->kn
;
1650 if (root
== &cgrp_dfl_root
)
1651 base_files
= cgroup_dfl_base_files
;
1653 base_files
= cgroup_legacy_base_files
;
1655 ret
= cgroup_addrm_files(root_cgrp
, base_files
, true);
1659 ret
= rebind_subsystems(root
, ss_mask
);
1664 * There must be no failure case after here, since rebinding takes
1665 * care of subsystems' refcounts, which are explicitly dropped in
1666 * the failure exit path.
1668 list_add(&root
->root_list
, &cgroup_roots
);
1669 cgroup_root_count
++;
1672 * Link the root cgroup in this hierarchy into all the css_set
1675 down_write(&css_set_rwsem
);
1676 hash_for_each(css_set_table
, i
, cset
, hlist
)
1677 link_css_set(&tmp_links
, cset
, root_cgrp
);
1678 up_write(&css_set_rwsem
);
1680 BUG_ON(!list_empty(&root_cgrp
->self
.children
));
1681 BUG_ON(atomic_read(&root
->nr_cgrps
) != 1);
1683 kernfs_activate(root_cgrp
->kn
);
1688 kernfs_destroy_root(root
->kf_root
);
1689 root
->kf_root
= NULL
;
1691 cgroup_exit_root_id(root
);
1693 percpu_ref_exit(&root_cgrp
->self
.refcnt
);
1695 free_cgrp_cset_links(&tmp_links
);
1699 static struct dentry
*cgroup_mount(struct file_system_type
*fs_type
,
1700 int flags
, const char *unused_dev_name
,
1703 struct super_block
*pinned_sb
= NULL
;
1704 struct cgroup_subsys
*ss
;
1705 struct cgroup_root
*root
;
1706 struct cgroup_sb_opts opts
;
1707 struct dentry
*dentry
;
1713 * The first time anyone tries to mount a cgroup, enable the list
1714 * linking each css_set to its tasks and fix up all existing tasks.
1716 if (!use_task_css_set_links
)
1717 cgroup_enable_task_cg_lists();
1719 mutex_lock(&cgroup_mutex
);
1721 /* First find the desired set of subsystems */
1722 ret
= parse_cgroupfs_options(data
, &opts
);
1726 /* look for a matching existing root */
1727 if (opts
.flags
& CGRP_ROOT_SANE_BEHAVIOR
) {
1728 cgrp_dfl_root_visible
= true;
1729 root
= &cgrp_dfl_root
;
1730 cgroup_get(&root
->cgrp
);
1736 * Destruction of cgroup root is asynchronous, so subsystems may
1737 * still be dying after the previous unmount. Let's drain the
1738 * dying subsystems. We just need to ensure that the ones
1739 * unmounted previously finish dying and don't care about new ones
1740 * starting. Testing ref liveliness is good enough.
1742 for_each_subsys(ss
, i
) {
1743 if (!(opts
.subsys_mask
& (1 << i
)) ||
1744 ss
->root
== &cgrp_dfl_root
)
1747 if (!percpu_ref_tryget_live(&ss
->root
->cgrp
.self
.refcnt
)) {
1748 mutex_unlock(&cgroup_mutex
);
1750 ret
= restart_syscall();
1753 cgroup_put(&ss
->root
->cgrp
);
1756 for_each_root(root
) {
1757 bool name_match
= false;
1759 if (root
== &cgrp_dfl_root
)
1763 * If we asked for a name then it must match. Also, if
1764 * name matches but sybsys_mask doesn't, we should fail.
1765 * Remember whether name matched.
1768 if (strcmp(opts
.name
, root
->name
))
1774 * If we asked for subsystems (or explicitly for no
1775 * subsystems) then they must match.
1777 if ((opts
.subsys_mask
|| opts
.none
) &&
1778 (opts
.subsys_mask
!= root
->subsys_mask
)) {
1785 if (root
->flags
^ opts
.flags
)
1786 pr_warn("new mount options do not match the existing superblock, will be ignored\n");
1789 * We want to reuse @root whose lifetime is governed by its
1790 * ->cgrp. Let's check whether @root is alive and keep it
1791 * that way. As cgroup_kill_sb() can happen anytime, we
1792 * want to block it by pinning the sb so that @root doesn't
1793 * get killed before mount is complete.
1795 * With the sb pinned, tryget_live can reliably indicate
1796 * whether @root can be reused. If it's being killed,
1797 * drain it. We can use wait_queue for the wait but this
1798 * path is super cold. Let's just sleep a bit and retry.
1800 pinned_sb
= kernfs_pin_sb(root
->kf_root
, NULL
);
1801 if (IS_ERR(pinned_sb
) ||
1802 !percpu_ref_tryget_live(&root
->cgrp
.self
.refcnt
)) {
1803 mutex_unlock(&cgroup_mutex
);
1804 if (!IS_ERR_OR_NULL(pinned_sb
))
1805 deactivate_super(pinned_sb
);
1807 ret
= restart_syscall();
1816 * No such thing, create a new one. name= matching without subsys
1817 * specification is allowed for already existing hierarchies but we
1818 * can't create new one without subsys specification.
1820 if (!opts
.subsys_mask
&& !opts
.none
) {
1825 root
= kzalloc(sizeof(*root
), GFP_KERNEL
);
1831 init_cgroup_root(root
, &opts
);
1833 ret
= cgroup_setup_root(root
, opts
.subsys_mask
);
1835 cgroup_free_root(root
);
1838 mutex_unlock(&cgroup_mutex
);
1840 kfree(opts
.release_agent
);
1844 return ERR_PTR(ret
);
1846 dentry
= kernfs_mount(fs_type
, flags
, root
->kf_root
,
1847 CGROUP_SUPER_MAGIC
, &new_sb
);
1848 if (IS_ERR(dentry
) || !new_sb
)
1849 cgroup_put(&root
->cgrp
);
1852 * If @pinned_sb, we're reusing an existing root and holding an
1853 * extra ref on its sb. Mount is complete. Put the extra ref.
1857 deactivate_super(pinned_sb
);
1863 static void cgroup_kill_sb(struct super_block
*sb
)
1865 struct kernfs_root
*kf_root
= kernfs_root_from_sb(sb
);
1866 struct cgroup_root
*root
= cgroup_root_from_kf(kf_root
);
1869 * If @root doesn't have any mounts or children, start killing it.
1870 * This prevents new mounts by disabling percpu_ref_tryget_live().
1871 * cgroup_mount() may wait for @root's release.
1873 * And don't kill the default root.
1875 if (css_has_online_children(&root
->cgrp
.self
) ||
1876 root
== &cgrp_dfl_root
)
1877 cgroup_put(&root
->cgrp
);
1879 percpu_ref_kill(&root
->cgrp
.self
.refcnt
);
1884 static struct file_system_type cgroup_fs_type
= {
1886 .mount
= cgroup_mount
,
1887 .kill_sb
= cgroup_kill_sb
,
1890 static struct kobject
*cgroup_kobj
;
1893 * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
1894 * @task: target task
1895 * @buf: the buffer to write the path into
1896 * @buflen: the length of the buffer
1898 * Determine @task's cgroup on the first (the one with the lowest non-zero
1899 * hierarchy_id) cgroup hierarchy and copy its path into @buf. This
1900 * function grabs cgroup_mutex and shouldn't be used inside locks used by
1901 * cgroup controller callbacks.
1903 * Return value is the same as kernfs_path().
1905 char *task_cgroup_path(struct task_struct
*task
, char *buf
, size_t buflen
)
1907 struct cgroup_root
*root
;
1908 struct cgroup
*cgrp
;
1909 int hierarchy_id
= 1;
1912 mutex_lock(&cgroup_mutex
);
1913 down_read(&css_set_rwsem
);
1915 root
= idr_get_next(&cgroup_hierarchy_idr
, &hierarchy_id
);
1918 cgrp
= task_cgroup_from_root(task
, root
);
1919 path
= cgroup_path(cgrp
, buf
, buflen
);
1921 /* if no hierarchy exists, everyone is in "/" */
1922 if (strlcpy(buf
, "/", buflen
) < buflen
)
1926 up_read(&css_set_rwsem
);
1927 mutex_unlock(&cgroup_mutex
);
1930 EXPORT_SYMBOL_GPL(task_cgroup_path
);
1932 /* used to track tasks and other necessary states during migration */
1933 struct cgroup_taskset
{
1934 /* the src and dst cset list running through cset->mg_node */
1935 struct list_head src_csets
;
1936 struct list_head dst_csets
;
1939 * Fields for cgroup_taskset_*() iteration.
1941 * Before migration is committed, the target migration tasks are on
1942 * ->mg_tasks of the csets on ->src_csets. After, on ->mg_tasks of
1943 * the csets on ->dst_csets. ->csets point to either ->src_csets
1944 * or ->dst_csets depending on whether migration is committed.
1946 * ->cur_csets and ->cur_task point to the current task position
1949 struct list_head
*csets
;
1950 struct css_set
*cur_cset
;
1951 struct task_struct
*cur_task
;
1955 * cgroup_taskset_first - reset taskset and return the first task
1956 * @tset: taskset of interest
1958 * @tset iteration is initialized and the first task is returned.
1960 struct task_struct
*cgroup_taskset_first(struct cgroup_taskset
*tset
)
1962 tset
->cur_cset
= list_first_entry(tset
->csets
, struct css_set
, mg_node
);
1963 tset
->cur_task
= NULL
;
1965 return cgroup_taskset_next(tset
);
1969 * cgroup_taskset_next - iterate to the next task in taskset
1970 * @tset: taskset of interest
1972 * Return the next task in @tset. Iteration must have been initialized
1973 * with cgroup_taskset_first().
1975 struct task_struct
*cgroup_taskset_next(struct cgroup_taskset
*tset
)
1977 struct css_set
*cset
= tset
->cur_cset
;
1978 struct task_struct
*task
= tset
->cur_task
;
1980 while (&cset
->mg_node
!= tset
->csets
) {
1982 task
= list_first_entry(&cset
->mg_tasks
,
1983 struct task_struct
, cg_list
);
1985 task
= list_next_entry(task
, cg_list
);
1987 if (&task
->cg_list
!= &cset
->mg_tasks
) {
1988 tset
->cur_cset
= cset
;
1989 tset
->cur_task
= task
;
1993 cset
= list_next_entry(cset
, mg_node
);
2001 * cgroup_task_migrate - move a task from one cgroup to another.
2002 * @old_cgrp: the cgroup @tsk is being migrated from
2003 * @tsk: the task being migrated
2004 * @new_cset: the new css_set @tsk is being attached to
2006 * Must be called with cgroup_mutex, threadgroup and css_set_rwsem locked.
2008 static void cgroup_task_migrate(struct cgroup
*old_cgrp
,
2009 struct task_struct
*tsk
,
2010 struct css_set
*new_cset
)
2012 struct css_set
*old_cset
;
2014 lockdep_assert_held(&cgroup_mutex
);
2015 lockdep_assert_held(&css_set_rwsem
);
2018 * We are synchronized through threadgroup_lock() against PF_EXITING
2019 * setting such that we can't race against cgroup_exit() changing the
2020 * css_set to init_css_set and dropping the old one.
2022 WARN_ON_ONCE(tsk
->flags
& PF_EXITING
);
2023 old_cset
= task_css_set(tsk
);
2025 get_css_set(new_cset
);
2026 rcu_assign_pointer(tsk
->cgroups
, new_cset
);
2029 * Use move_tail so that cgroup_taskset_first() still returns the
2030 * leader after migration. This works because cgroup_migrate()
2031 * ensures that the dst_cset of the leader is the first on the
2032 * tset's dst_csets list.
2034 list_move_tail(&tsk
->cg_list
, &new_cset
->mg_tasks
);
2037 * We just gained a reference on old_cset by taking it from the
2038 * task. As trading it for new_cset is protected by cgroup_mutex,
2039 * we're safe to drop it here; it will be freed under RCU.
2041 put_css_set_locked(old_cset
);
2045 * cgroup_migrate_finish - cleanup after attach
2046 * @preloaded_csets: list of preloaded css_sets
2048 * Undo cgroup_migrate_add_src() and cgroup_migrate_prepare_dst(). See
2049 * those functions for details.
2051 static void cgroup_migrate_finish(struct list_head
*preloaded_csets
)
2053 struct css_set
*cset
, *tmp_cset
;
2055 lockdep_assert_held(&cgroup_mutex
);
2057 down_write(&css_set_rwsem
);
2058 list_for_each_entry_safe(cset
, tmp_cset
, preloaded_csets
, mg_preload_node
) {
2059 cset
->mg_src_cgrp
= NULL
;
2060 cset
->mg_dst_cset
= NULL
;
2061 list_del_init(&cset
->mg_preload_node
);
2062 put_css_set_locked(cset
);
2064 up_write(&css_set_rwsem
);
2068 * cgroup_migrate_add_src - add a migration source css_set
2069 * @src_cset: the source css_set to add
2070 * @dst_cgrp: the destination cgroup
2071 * @preloaded_csets: list of preloaded css_sets
2073 * Tasks belonging to @src_cset are about to be migrated to @dst_cgrp. Pin
2074 * @src_cset and add it to @preloaded_csets, which should later be cleaned
2075 * up by cgroup_migrate_finish().
2077 * This function may be called without holding threadgroup_lock even if the
2078 * target is a process. Threads may be created and destroyed but as long
2079 * as cgroup_mutex is not dropped, no new css_set can be put into play and
2080 * the preloaded css_sets are guaranteed to cover all migrations.
2082 static void cgroup_migrate_add_src(struct css_set
*src_cset
,
2083 struct cgroup
*dst_cgrp
,
2084 struct list_head
*preloaded_csets
)
2086 struct cgroup
*src_cgrp
;
2088 lockdep_assert_held(&cgroup_mutex
);
2089 lockdep_assert_held(&css_set_rwsem
);
2091 src_cgrp
= cset_cgroup_from_root(src_cset
, dst_cgrp
->root
);
2093 if (!list_empty(&src_cset
->mg_preload_node
))
2096 WARN_ON(src_cset
->mg_src_cgrp
);
2097 WARN_ON(!list_empty(&src_cset
->mg_tasks
));
2098 WARN_ON(!list_empty(&src_cset
->mg_node
));
2100 src_cset
->mg_src_cgrp
= src_cgrp
;
2101 get_css_set(src_cset
);
2102 list_add(&src_cset
->mg_preload_node
, preloaded_csets
);
2106 * cgroup_migrate_prepare_dst - prepare destination css_sets for migration
2107 * @dst_cgrp: the destination cgroup (may be %NULL)
2108 * @preloaded_csets: list of preloaded source css_sets
2110 * Tasks are about to be moved to @dst_cgrp and all the source css_sets
2111 * have been preloaded to @preloaded_csets. This function looks up and
2112 * pins all destination css_sets, links each to its source, and append them
2113 * to @preloaded_csets. If @dst_cgrp is %NULL, the destination of each
2114 * source css_set is assumed to be its cgroup on the default hierarchy.
2116 * This function must be called after cgroup_migrate_add_src() has been
2117 * called on each migration source css_set. After migration is performed
2118 * using cgroup_migrate(), cgroup_migrate_finish() must be called on
2121 static int cgroup_migrate_prepare_dst(struct cgroup
*dst_cgrp
,
2122 struct list_head
*preloaded_csets
)
2125 struct css_set
*src_cset
, *tmp_cset
;
2127 lockdep_assert_held(&cgroup_mutex
);
2130 * Except for the root, child_subsys_mask must be zero for a cgroup
2131 * with tasks so that child cgroups don't compete against tasks.
2133 if (dst_cgrp
&& cgroup_on_dfl(dst_cgrp
) && cgroup_parent(dst_cgrp
) &&
2134 dst_cgrp
->child_subsys_mask
)
2137 /* look up the dst cset for each src cset and link it to src */
2138 list_for_each_entry_safe(src_cset
, tmp_cset
, preloaded_csets
, mg_preload_node
) {
2139 struct css_set
*dst_cset
;
2141 dst_cset
= find_css_set(src_cset
,
2142 dst_cgrp
?: src_cset
->dfl_cgrp
);
2146 WARN_ON_ONCE(src_cset
->mg_dst_cset
|| dst_cset
->mg_dst_cset
);
2149 * If src cset equals dst, it's noop. Drop the src.
2150 * cgroup_migrate() will skip the cset too. Note that we
2151 * can't handle src == dst as some nodes are used by both.
2153 if (src_cset
== dst_cset
) {
2154 src_cset
->mg_src_cgrp
= NULL
;
2155 list_del_init(&src_cset
->mg_preload_node
);
2156 put_css_set(src_cset
);
2157 put_css_set(dst_cset
);
2161 src_cset
->mg_dst_cset
= dst_cset
;
2163 if (list_empty(&dst_cset
->mg_preload_node
))
2164 list_add(&dst_cset
->mg_preload_node
, &csets
);
2166 put_css_set(dst_cset
);
2169 list_splice_tail(&csets
, preloaded_csets
);
2172 cgroup_migrate_finish(&csets
);
2177 * cgroup_migrate - migrate a process or task to a cgroup
2178 * @cgrp: the destination cgroup
2179 * @leader: the leader of the process or the task to migrate
2180 * @threadgroup: whether @leader points to the whole process or a single task
2182 * Migrate a process or task denoted by @leader to @cgrp. If migrating a
2183 * process, the caller must be holding threadgroup_lock of @leader. The
2184 * caller is also responsible for invoking cgroup_migrate_add_src() and
2185 * cgroup_migrate_prepare_dst() on the targets before invoking this
2186 * function and following up with cgroup_migrate_finish().
2188 * As long as a controller's ->can_attach() doesn't fail, this function is
2189 * guaranteed to succeed. This means that, excluding ->can_attach()
2190 * failure, when migrating multiple targets, the success or failure can be
2191 * decided for all targets by invoking group_migrate_prepare_dst() before
2192 * actually starting migrating.
2194 static int cgroup_migrate(struct cgroup
*cgrp
, struct task_struct
*leader
,
2197 struct cgroup_taskset tset
= {
2198 .src_csets
= LIST_HEAD_INIT(tset
.src_csets
),
2199 .dst_csets
= LIST_HEAD_INIT(tset
.dst_csets
),
2200 .csets
= &tset
.src_csets
,
2202 struct cgroup_subsys_state
*css
, *failed_css
= NULL
;
2203 struct css_set
*cset
, *tmp_cset
;
2204 struct task_struct
*task
, *tmp_task
;
2208 * Prevent freeing of tasks while we take a snapshot. Tasks that are
2209 * already PF_EXITING could be freed from underneath us unless we
2210 * take an rcu_read_lock.
2212 down_write(&css_set_rwsem
);
2216 /* @task either already exited or can't exit until the end */
2217 if (task
->flags
& PF_EXITING
)
2220 /* leave @task alone if post_fork() hasn't linked it yet */
2221 if (list_empty(&task
->cg_list
))
2224 cset
= task_css_set(task
);
2225 if (!cset
->mg_src_cgrp
)
2229 * cgroup_taskset_first() must always return the leader.
2230 * Take care to avoid disturbing the ordering.
2232 list_move_tail(&task
->cg_list
, &cset
->mg_tasks
);
2233 if (list_empty(&cset
->mg_node
))
2234 list_add_tail(&cset
->mg_node
, &tset
.src_csets
);
2235 if (list_empty(&cset
->mg_dst_cset
->mg_node
))
2236 list_move_tail(&cset
->mg_dst_cset
->mg_node
,
2241 } while_each_thread(leader
, task
);
2243 up_write(&css_set_rwsem
);
2245 /* methods shouldn't be called if no task is actually migrating */
2246 if (list_empty(&tset
.src_csets
))
2249 /* check that we can legitimately attach to the cgroup */
2250 for_each_e_css(css
, i
, cgrp
) {
2251 if (css
->ss
->can_attach
) {
2252 ret
= css
->ss
->can_attach(css
, &tset
);
2255 goto out_cancel_attach
;
2261 * Now that we're guaranteed success, proceed to move all tasks to
2262 * the new cgroup. There are no failure cases after here, so this
2263 * is the commit point.
2265 down_write(&css_set_rwsem
);
2266 list_for_each_entry(cset
, &tset
.src_csets
, mg_node
) {
2267 list_for_each_entry_safe(task
, tmp_task
, &cset
->mg_tasks
, cg_list
)
2268 cgroup_task_migrate(cset
->mg_src_cgrp
, task
,
2271 up_write(&css_set_rwsem
);
2274 * Migration is committed, all target tasks are now on dst_csets.
2275 * Nothing is sensitive to fork() after this point. Notify
2276 * controllers that migration is complete.
2278 tset
.csets
= &tset
.dst_csets
;
2280 for_each_e_css(css
, i
, cgrp
)
2281 if (css
->ss
->attach
)
2282 css
->ss
->attach(css
, &tset
);
2285 goto out_release_tset
;
2288 for_each_e_css(css
, i
, cgrp
) {
2289 if (css
== failed_css
)
2291 if (css
->ss
->cancel_attach
)
2292 css
->ss
->cancel_attach(css
, &tset
);
2295 down_write(&css_set_rwsem
);
2296 list_splice_init(&tset
.dst_csets
, &tset
.src_csets
);
2297 list_for_each_entry_safe(cset
, tmp_cset
, &tset
.src_csets
, mg_node
) {
2298 list_splice_tail_init(&cset
->mg_tasks
, &cset
->tasks
);
2299 list_del_init(&cset
->mg_node
);
2301 up_write(&css_set_rwsem
);
2306 * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
2307 * @dst_cgrp: the cgroup to attach to
2308 * @leader: the task or the leader of the threadgroup to be attached
2309 * @threadgroup: attach the whole threadgroup?
2311 * Call holding cgroup_mutex and threadgroup_lock of @leader.
2313 static int cgroup_attach_task(struct cgroup
*dst_cgrp
,
2314 struct task_struct
*leader
, bool threadgroup
)
2316 LIST_HEAD(preloaded_csets
);
2317 struct task_struct
*task
;
2320 /* look up all src csets */
2321 down_read(&css_set_rwsem
);
2325 cgroup_migrate_add_src(task_css_set(task
), dst_cgrp
,
2329 } while_each_thread(leader
, task
);
2331 up_read(&css_set_rwsem
);
2333 /* prepare dst csets and commit */
2334 ret
= cgroup_migrate_prepare_dst(dst_cgrp
, &preloaded_csets
);
2336 ret
= cgroup_migrate(dst_cgrp
, leader
, threadgroup
);
2338 cgroup_migrate_finish(&preloaded_csets
);
2343 * Find the task_struct of the task to attach by vpid and pass it along to the
2344 * function to attach either it or all tasks in its threadgroup. Will lock
2345 * cgroup_mutex and threadgroup.
2347 static ssize_t
__cgroup_procs_write(struct kernfs_open_file
*of
, char *buf
,
2348 size_t nbytes
, loff_t off
, bool threadgroup
)
2350 struct task_struct
*tsk
;
2351 const struct cred
*cred
= current_cred(), *tcred
;
2352 struct cgroup
*cgrp
;
2356 if (kstrtoint(strstrip(buf
), 0, &pid
) || pid
< 0)
2359 cgrp
= cgroup_kn_lock_live(of
->kn
);
2366 tsk
= find_task_by_vpid(pid
);
2370 goto out_unlock_cgroup
;
2373 * even if we're attaching all tasks in the thread group, we
2374 * only need to check permissions on one of them.
2376 tcred
= __task_cred(tsk
);
2377 if (!uid_eq(cred
->euid
, GLOBAL_ROOT_UID
) &&
2378 !uid_eq(cred
->euid
, tcred
->uid
) &&
2379 !uid_eq(cred
->euid
, tcred
->suid
)) {
2382 goto out_unlock_cgroup
;
2388 tsk
= tsk
->group_leader
;
2391 * Workqueue threads may acquire PF_NO_SETAFFINITY and become
2392 * trapped in a cpuset, or RT worker may be born in a cgroup
2393 * with no rt_runtime allocated. Just say no.
2395 if (tsk
== kthreadd_task
|| (tsk
->flags
& PF_NO_SETAFFINITY
)) {
2398 goto out_unlock_cgroup
;
2401 get_task_struct(tsk
);
2404 threadgroup_lock(tsk
);
2406 if (!thread_group_leader(tsk
)) {
2408 * a race with de_thread from another thread's exec()
2409 * may strip us of our leadership, if this happens,
2410 * there is no choice but to throw this task away and
2411 * try again; this is
2412 * "double-double-toil-and-trouble-check locking".
2414 threadgroup_unlock(tsk
);
2415 put_task_struct(tsk
);
2416 goto retry_find_task
;
2420 ret
= cgroup_attach_task(cgrp
, tsk
, threadgroup
);
2422 threadgroup_unlock(tsk
);
2424 put_task_struct(tsk
);
2426 cgroup_kn_unlock(of
->kn
);
2427 return ret
?: nbytes
;
2431 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
2432 * @from: attach to all cgroups of a given task
2433 * @tsk: the task to be attached
2435 int cgroup_attach_task_all(struct task_struct
*from
, struct task_struct
*tsk
)
2437 struct cgroup_root
*root
;
2440 mutex_lock(&cgroup_mutex
);
2441 for_each_root(root
) {
2442 struct cgroup
*from_cgrp
;
2444 if (root
== &cgrp_dfl_root
)
2447 down_read(&css_set_rwsem
);
2448 from_cgrp
= task_cgroup_from_root(from
, root
);
2449 up_read(&css_set_rwsem
);
2451 retval
= cgroup_attach_task(from_cgrp
, tsk
, false);
2455 mutex_unlock(&cgroup_mutex
);
2459 EXPORT_SYMBOL_GPL(cgroup_attach_task_all
);
2461 static ssize_t
cgroup_tasks_write(struct kernfs_open_file
*of
,
2462 char *buf
, size_t nbytes
, loff_t off
)
2464 return __cgroup_procs_write(of
, buf
, nbytes
, off
, false);
2467 static ssize_t
cgroup_procs_write(struct kernfs_open_file
*of
,
2468 char *buf
, size_t nbytes
, loff_t off
)
2470 return __cgroup_procs_write(of
, buf
, nbytes
, off
, true);
2473 static ssize_t
cgroup_release_agent_write(struct kernfs_open_file
*of
,
2474 char *buf
, size_t nbytes
, loff_t off
)
2476 struct cgroup
*cgrp
;
2478 BUILD_BUG_ON(sizeof(cgrp
->root
->release_agent_path
) < PATH_MAX
);
2480 cgrp
= cgroup_kn_lock_live(of
->kn
);
2483 spin_lock(&release_agent_path_lock
);
2484 strlcpy(cgrp
->root
->release_agent_path
, strstrip(buf
),
2485 sizeof(cgrp
->root
->release_agent_path
));
2486 spin_unlock(&release_agent_path_lock
);
2487 cgroup_kn_unlock(of
->kn
);
2491 static int cgroup_release_agent_show(struct seq_file
*seq
, void *v
)
2493 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2495 spin_lock(&release_agent_path_lock
);
2496 seq_puts(seq
, cgrp
->root
->release_agent_path
);
2497 spin_unlock(&release_agent_path_lock
);
2498 seq_putc(seq
, '\n');
2502 static int cgroup_sane_behavior_show(struct seq_file
*seq
, void *v
)
2504 seq_puts(seq
, "0\n");
2508 static void cgroup_print_ss_mask(struct seq_file
*seq
, unsigned int ss_mask
)
2510 struct cgroup_subsys
*ss
;
2511 bool printed
= false;
2514 for_each_subsys(ss
, ssid
) {
2515 if (ss_mask
& (1 << ssid
)) {
2518 seq_printf(seq
, "%s", ss
->name
);
2523 seq_putc(seq
, '\n');
2526 /* show controllers which are currently attached to the default hierarchy */
2527 static int cgroup_root_controllers_show(struct seq_file
*seq
, void *v
)
2529 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2531 cgroup_print_ss_mask(seq
, cgrp
->root
->subsys_mask
&
2532 ~cgrp_dfl_root_inhibit_ss_mask
);
2536 /* show controllers which are enabled from the parent */
2537 static int cgroup_controllers_show(struct seq_file
*seq
, void *v
)
2539 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2541 cgroup_print_ss_mask(seq
, cgroup_parent(cgrp
)->subtree_control
);
2545 /* show controllers which are enabled for a given cgroup's children */
2546 static int cgroup_subtree_control_show(struct seq_file
*seq
, void *v
)
2548 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2550 cgroup_print_ss_mask(seq
, cgrp
->subtree_control
);
2555 * cgroup_update_dfl_csses - update css assoc of a subtree in default hierarchy
2556 * @cgrp: root of the subtree to update csses for
2558 * @cgrp's child_subsys_mask has changed and its subtree's (self excluded)
2559 * css associations need to be updated accordingly. This function looks up
2560 * all css_sets which are attached to the subtree, creates the matching
2561 * updated css_sets and migrates the tasks to the new ones.
2563 static int cgroup_update_dfl_csses(struct cgroup
*cgrp
)
2565 LIST_HEAD(preloaded_csets
);
2566 struct cgroup_subsys_state
*css
;
2567 struct css_set
*src_cset
;
2570 lockdep_assert_held(&cgroup_mutex
);
2572 /* look up all csses currently attached to @cgrp's subtree */
2573 down_read(&css_set_rwsem
);
2574 css_for_each_descendant_pre(css
, cgroup_css(cgrp
, NULL
)) {
2575 struct cgrp_cset_link
*link
;
2577 /* self is not affected by child_subsys_mask change */
2578 if (css
->cgroup
== cgrp
)
2581 list_for_each_entry(link
, &css
->cgroup
->cset_links
, cset_link
)
2582 cgroup_migrate_add_src(link
->cset
, cgrp
,
2585 up_read(&css_set_rwsem
);
2587 /* NULL dst indicates self on default hierarchy */
2588 ret
= cgroup_migrate_prepare_dst(NULL
, &preloaded_csets
);
2592 list_for_each_entry(src_cset
, &preloaded_csets
, mg_preload_node
) {
2593 struct task_struct
*last_task
= NULL
, *task
;
2595 /* src_csets precede dst_csets, break on the first dst_cset */
2596 if (!src_cset
->mg_src_cgrp
)
2600 * All tasks in src_cset need to be migrated to the
2601 * matching dst_cset. Empty it process by process. We
2602 * walk tasks but migrate processes. The leader might even
2603 * belong to a different cset but such src_cset would also
2604 * be among the target src_csets because the default
2605 * hierarchy enforces per-process membership.
2608 down_read(&css_set_rwsem
);
2609 task
= list_first_entry_or_null(&src_cset
->tasks
,
2610 struct task_struct
, cg_list
);
2612 task
= task
->group_leader
;
2613 WARN_ON_ONCE(!task_css_set(task
)->mg_src_cgrp
);
2614 get_task_struct(task
);
2616 up_read(&css_set_rwsem
);
2621 /* guard against possible infinite loop */
2622 if (WARN(last_task
== task
,
2623 "cgroup: update_dfl_csses failed to make progress, aborting in inconsistent state\n"))
2627 threadgroup_lock(task
);
2628 /* raced against de_thread() from another thread? */
2629 if (!thread_group_leader(task
)) {
2630 threadgroup_unlock(task
);
2631 put_task_struct(task
);
2635 ret
= cgroup_migrate(src_cset
->dfl_cgrp
, task
, true);
2637 threadgroup_unlock(task
);
2638 put_task_struct(task
);
2640 if (WARN(ret
, "cgroup: failed to update controllers for the default hierarchy (%d), further operations may crash or hang\n", ret
))
2646 cgroup_migrate_finish(&preloaded_csets
);
2650 /* change the enabled child controllers for a cgroup in the default hierarchy */
2651 static ssize_t
cgroup_subtree_control_write(struct kernfs_open_file
*of
,
2652 char *buf
, size_t nbytes
,
2655 unsigned int enable
= 0, disable
= 0;
2656 unsigned int css_enable
, css_disable
, old_sc
, new_sc
, old_ss
, new_ss
;
2657 struct cgroup
*cgrp
, *child
;
2658 struct cgroup_subsys
*ss
;
2663 * Parse input - space separated list of subsystem names prefixed
2664 * with either + or -.
2666 buf
= strstrip(buf
);
2667 while ((tok
= strsep(&buf
, " "))) {
2670 for_each_subsys(ss
, ssid
) {
2671 if (ss
->disabled
|| strcmp(tok
+ 1, ss
->name
) ||
2672 ((1 << ss
->id
) & cgrp_dfl_root_inhibit_ss_mask
))
2676 enable
|= 1 << ssid
;
2677 disable
&= ~(1 << ssid
);
2678 } else if (*tok
== '-') {
2679 disable
|= 1 << ssid
;
2680 enable
&= ~(1 << ssid
);
2686 if (ssid
== CGROUP_SUBSYS_COUNT
)
2690 cgrp
= cgroup_kn_lock_live(of
->kn
);
2694 for_each_subsys(ss
, ssid
) {
2695 if (enable
& (1 << ssid
)) {
2696 if (cgrp
->subtree_control
& (1 << ssid
)) {
2697 enable
&= ~(1 << ssid
);
2701 /* unavailable or not enabled on the parent? */
2702 if (!(cgrp_dfl_root
.subsys_mask
& (1 << ssid
)) ||
2703 (cgroup_parent(cgrp
) &&
2704 !(cgroup_parent(cgrp
)->subtree_control
& (1 << ssid
)))) {
2708 } else if (disable
& (1 << ssid
)) {
2709 if (!(cgrp
->subtree_control
& (1 << ssid
))) {
2710 disable
&= ~(1 << ssid
);
2714 /* a child has it enabled? */
2715 cgroup_for_each_live_child(child
, cgrp
) {
2716 if (child
->subtree_control
& (1 << ssid
)) {
2724 if (!enable
&& !disable
) {
2730 * Except for the root, subtree_control must be zero for a cgroup
2731 * with tasks so that child cgroups don't compete against tasks.
2733 if (enable
&& cgroup_parent(cgrp
) && !list_empty(&cgrp
->cset_links
)) {
2739 * Update subsys masks and calculate what needs to be done. More
2740 * subsystems than specified may need to be enabled or disabled
2741 * depending on subsystem dependencies.
2743 old_sc
= cgrp
->subtree_control
;
2744 old_ss
= cgrp
->child_subsys_mask
;
2745 new_sc
= (old_sc
| enable
) & ~disable
;
2746 new_ss
= cgroup_calc_child_subsys_mask(cgrp
, new_sc
);
2748 css_enable
= ~old_ss
& new_ss
;
2749 css_disable
= old_ss
& ~new_ss
;
2750 enable
|= css_enable
;
2751 disable
|= css_disable
;
2754 * Because css offlining is asynchronous, userland might try to
2755 * re-enable the same controller while the previous instance is
2756 * still around. In such cases, wait till it's gone using
2759 for_each_subsys(ss
, ssid
) {
2760 if (!(css_enable
& (1 << ssid
)))
2763 cgroup_for_each_live_child(child
, cgrp
) {
2766 if (!cgroup_css(child
, ss
))
2770 prepare_to_wait(&child
->offline_waitq
, &wait
,
2771 TASK_UNINTERRUPTIBLE
);
2772 cgroup_kn_unlock(of
->kn
);
2774 finish_wait(&child
->offline_waitq
, &wait
);
2777 return restart_syscall();
2781 cgrp
->subtree_control
= new_sc
;
2782 cgrp
->child_subsys_mask
= new_ss
;
2785 * Create new csses or make the existing ones visible. A css is
2786 * created invisible if it's being implicitly enabled through
2787 * dependency. An invisible css is made visible when the userland
2788 * explicitly enables it.
2790 for_each_subsys(ss
, ssid
) {
2791 if (!(enable
& (1 << ssid
)))
2794 cgroup_for_each_live_child(child
, cgrp
) {
2795 if (css_enable
& (1 << ssid
))
2796 ret
= create_css(child
, ss
,
2797 cgrp
->subtree_control
& (1 << ssid
));
2799 ret
= cgroup_populate_dir(child
, 1 << ssid
);
2806 * At this point, cgroup_e_css() results reflect the new csses
2807 * making the following cgroup_update_dfl_csses() properly update
2808 * css associations of all tasks in the subtree.
2810 ret
= cgroup_update_dfl_csses(cgrp
);
2815 * All tasks are migrated out of disabled csses. Kill or hide
2816 * them. A css is hidden when the userland requests it to be
2817 * disabled while other subsystems are still depending on it. The
2818 * css must not actively control resources and be in the vanilla
2819 * state if it's made visible again later. Controllers which may
2820 * be depended upon should provide ->css_reset() for this purpose.
2822 for_each_subsys(ss
, ssid
) {
2823 if (!(disable
& (1 << ssid
)))
2826 cgroup_for_each_live_child(child
, cgrp
) {
2827 struct cgroup_subsys_state
*css
= cgroup_css(child
, ss
);
2829 if (css_disable
& (1 << ssid
)) {
2832 cgroup_clear_dir(child
, 1 << ssid
);
2839 kernfs_activate(cgrp
->kn
);
2842 cgroup_kn_unlock(of
->kn
);
2843 return ret
?: nbytes
;
2846 cgrp
->subtree_control
= old_sc
;
2847 cgrp
->child_subsys_mask
= old_ss
;
2849 for_each_subsys(ss
, ssid
) {
2850 if (!(enable
& (1 << ssid
)))
2853 cgroup_for_each_live_child(child
, cgrp
) {
2854 struct cgroup_subsys_state
*css
= cgroup_css(child
, ss
);
2859 if (css_enable
& (1 << ssid
))
2862 cgroup_clear_dir(child
, 1 << ssid
);
2868 static int cgroup_populated_show(struct seq_file
*seq
, void *v
)
2870 seq_printf(seq
, "%d\n", (bool)seq_css(seq
)->cgroup
->populated_cnt
);
2874 static ssize_t
cgroup_file_write(struct kernfs_open_file
*of
, char *buf
,
2875 size_t nbytes
, loff_t off
)
2877 struct cgroup
*cgrp
= of
->kn
->parent
->priv
;
2878 struct cftype
*cft
= of
->kn
->priv
;
2879 struct cgroup_subsys_state
*css
;
2883 return cft
->write(of
, buf
, nbytes
, off
);
2886 * kernfs guarantees that a file isn't deleted with operations in
2887 * flight, which means that the matching css is and stays alive and
2888 * doesn't need to be pinned. The RCU locking is not necessary
2889 * either. It's just for the convenience of using cgroup_css().
2892 css
= cgroup_css(cgrp
, cft
->ss
);
2895 if (cft
->write_u64
) {
2896 unsigned long long v
;
2897 ret
= kstrtoull(buf
, 0, &v
);
2899 ret
= cft
->write_u64(css
, cft
, v
);
2900 } else if (cft
->write_s64
) {
2902 ret
= kstrtoll(buf
, 0, &v
);
2904 ret
= cft
->write_s64(css
, cft
, v
);
2909 return ret
?: nbytes
;
2912 static void *cgroup_seqfile_start(struct seq_file
*seq
, loff_t
*ppos
)
2914 return seq_cft(seq
)->seq_start(seq
, ppos
);
2917 static void *cgroup_seqfile_next(struct seq_file
*seq
, void *v
, loff_t
*ppos
)
2919 return seq_cft(seq
)->seq_next(seq
, v
, ppos
);
2922 static void cgroup_seqfile_stop(struct seq_file
*seq
, void *v
)
2924 seq_cft(seq
)->seq_stop(seq
, v
);
2927 static int cgroup_seqfile_show(struct seq_file
*m
, void *arg
)
2929 struct cftype
*cft
= seq_cft(m
);
2930 struct cgroup_subsys_state
*css
= seq_css(m
);
2933 return cft
->seq_show(m
, arg
);
2936 seq_printf(m
, "%llu\n", cft
->read_u64(css
, cft
));
2937 else if (cft
->read_s64
)
2938 seq_printf(m
, "%lld\n", cft
->read_s64(css
, cft
));
2944 static struct kernfs_ops cgroup_kf_single_ops
= {
2945 .atomic_write_len
= PAGE_SIZE
,
2946 .write
= cgroup_file_write
,
2947 .seq_show
= cgroup_seqfile_show
,
2950 static struct kernfs_ops cgroup_kf_ops
= {
2951 .atomic_write_len
= PAGE_SIZE
,
2952 .write
= cgroup_file_write
,
2953 .seq_start
= cgroup_seqfile_start
,
2954 .seq_next
= cgroup_seqfile_next
,
2955 .seq_stop
= cgroup_seqfile_stop
,
2956 .seq_show
= cgroup_seqfile_show
,
2960 * cgroup_rename - Only allow simple rename of directories in place.
2962 static int cgroup_rename(struct kernfs_node
*kn
, struct kernfs_node
*new_parent
,
2963 const char *new_name_str
)
2965 struct cgroup
*cgrp
= kn
->priv
;
2968 if (kernfs_type(kn
) != KERNFS_DIR
)
2970 if (kn
->parent
!= new_parent
)
2974 * This isn't a proper migration and its usefulness is very
2975 * limited. Disallow on the default hierarchy.
2977 if (cgroup_on_dfl(cgrp
))
2981 * We're gonna grab cgroup_mutex which nests outside kernfs
2982 * active_ref. kernfs_rename() doesn't require active_ref
2983 * protection. Break them before grabbing cgroup_mutex.
2985 kernfs_break_active_protection(new_parent
);
2986 kernfs_break_active_protection(kn
);
2988 mutex_lock(&cgroup_mutex
);
2990 ret
= kernfs_rename(kn
, new_parent
, new_name_str
);
2992 mutex_unlock(&cgroup_mutex
);
2994 kernfs_unbreak_active_protection(kn
);
2995 kernfs_unbreak_active_protection(new_parent
);
2999 /* set uid and gid of cgroup dirs and files to that of the creator */
3000 static int cgroup_kn_set_ugid(struct kernfs_node
*kn
)
3002 struct iattr iattr
= { .ia_valid
= ATTR_UID
| ATTR_GID
,
3003 .ia_uid
= current_fsuid(),
3004 .ia_gid
= current_fsgid(), };
3006 if (uid_eq(iattr
.ia_uid
, GLOBAL_ROOT_UID
) &&
3007 gid_eq(iattr
.ia_gid
, GLOBAL_ROOT_GID
))
3010 return kernfs_setattr(kn
, &iattr
);
3013 static int cgroup_add_file(struct cgroup
*cgrp
, struct cftype
*cft
)
3015 char name
[CGROUP_FILE_NAME_MAX
];
3016 struct kernfs_node
*kn
;
3017 struct lock_class_key
*key
= NULL
;
3020 #ifdef CONFIG_DEBUG_LOCK_ALLOC
3021 key
= &cft
->lockdep_key
;
3023 kn
= __kernfs_create_file(cgrp
->kn
, cgroup_file_name(cgrp
, cft
, name
),
3024 cgroup_file_mode(cft
), 0, cft
->kf_ops
, cft
,
3029 ret
= cgroup_kn_set_ugid(kn
);
3035 if (cft
->seq_show
== cgroup_populated_show
)
3036 cgrp
->populated_kn
= kn
;
3041 * cgroup_addrm_files - add or remove files to a cgroup directory
3042 * @cgrp: the target cgroup
3043 * @cfts: array of cftypes to be added
3044 * @is_add: whether to add or remove
3046 * Depending on @is_add, add or remove files defined by @cfts on @cgrp.
3047 * For removals, this function never fails. If addition fails, this
3048 * function doesn't remove files already added. The caller is responsible
3051 static int cgroup_addrm_files(struct cgroup
*cgrp
, struct cftype cfts
[],
3057 lockdep_assert_held(&cgroup_mutex
);
3059 for (cft
= cfts
; cft
->name
[0] != '\0'; cft
++) {
3060 /* does cft->flags tell us to skip this file on @cgrp? */
3061 if ((cft
->flags
& __CFTYPE_ONLY_ON_DFL
) && !cgroup_on_dfl(cgrp
))
3063 if ((cft
->flags
& __CFTYPE_NOT_ON_DFL
) && cgroup_on_dfl(cgrp
))
3065 if ((cft
->flags
& CFTYPE_NOT_ON_ROOT
) && !cgroup_parent(cgrp
))
3067 if ((cft
->flags
& CFTYPE_ONLY_ON_ROOT
) && cgroup_parent(cgrp
))
3071 ret
= cgroup_add_file(cgrp
, cft
);
3073 pr_warn("%s: failed to add %s, err=%d\n",
3074 __func__
, cft
->name
, ret
);
3078 cgroup_rm_file(cgrp
, cft
);
3084 static int cgroup_apply_cftypes(struct cftype
*cfts
, bool is_add
)
3087 struct cgroup_subsys
*ss
= cfts
[0].ss
;
3088 struct cgroup
*root
= &ss
->root
->cgrp
;
3089 struct cgroup_subsys_state
*css
;
3092 lockdep_assert_held(&cgroup_mutex
);
3094 /* add/rm files for all cgroups created before */
3095 css_for_each_descendant_pre(css
, cgroup_css(root
, ss
)) {
3096 struct cgroup
*cgrp
= css
->cgroup
;
3098 if (cgroup_is_dead(cgrp
))
3101 ret
= cgroup_addrm_files(cgrp
, cfts
, is_add
);
3107 kernfs_activate(root
->kn
);
3111 static void cgroup_exit_cftypes(struct cftype
*cfts
)
3115 for (cft
= cfts
; cft
->name
[0] != '\0'; cft
++) {
3116 /* free copy for custom atomic_write_len, see init_cftypes() */
3117 if (cft
->max_write_len
&& cft
->max_write_len
!= PAGE_SIZE
)
3122 /* revert flags set by cgroup core while adding @cfts */
3123 cft
->flags
&= ~(__CFTYPE_ONLY_ON_DFL
| __CFTYPE_NOT_ON_DFL
);
3127 static int cgroup_init_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3131 for (cft
= cfts
; cft
->name
[0] != '\0'; cft
++) {
3132 struct kernfs_ops
*kf_ops
;
3134 WARN_ON(cft
->ss
|| cft
->kf_ops
);
3137 kf_ops
= &cgroup_kf_ops
;
3139 kf_ops
= &cgroup_kf_single_ops
;
3142 * Ugh... if @cft wants a custom max_write_len, we need to
3143 * make a copy of kf_ops to set its atomic_write_len.
3145 if (cft
->max_write_len
&& cft
->max_write_len
!= PAGE_SIZE
) {
3146 kf_ops
= kmemdup(kf_ops
, sizeof(*kf_ops
), GFP_KERNEL
);
3148 cgroup_exit_cftypes(cfts
);
3151 kf_ops
->atomic_write_len
= cft
->max_write_len
;
3154 cft
->kf_ops
= kf_ops
;
3161 static int cgroup_rm_cftypes_locked(struct cftype
*cfts
)
3163 lockdep_assert_held(&cgroup_mutex
);
3165 if (!cfts
|| !cfts
[0].ss
)
3168 list_del(&cfts
->node
);
3169 cgroup_apply_cftypes(cfts
, false);
3170 cgroup_exit_cftypes(cfts
);
3175 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
3176 * @cfts: zero-length name terminated array of cftypes
3178 * Unregister @cfts. Files described by @cfts are removed from all
3179 * existing cgroups and all future cgroups won't have them either. This
3180 * function can be called anytime whether @cfts' subsys is attached or not.
3182 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
3185 int cgroup_rm_cftypes(struct cftype
*cfts
)
3189 mutex_lock(&cgroup_mutex
);
3190 ret
= cgroup_rm_cftypes_locked(cfts
);
3191 mutex_unlock(&cgroup_mutex
);
3196 * cgroup_add_cftypes - add an array of cftypes to a subsystem
3197 * @ss: target cgroup subsystem
3198 * @cfts: zero-length name terminated array of cftypes
3200 * Register @cfts to @ss. Files described by @cfts are created for all
3201 * existing cgroups to which @ss is attached and all future cgroups will
3202 * have them too. This function can be called anytime whether @ss is
3205 * Returns 0 on successful registration, -errno on failure. Note that this
3206 * function currently returns 0 as long as @cfts registration is successful
3207 * even if some file creation attempts on existing cgroups fail.
3209 static int cgroup_add_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3216 if (!cfts
|| cfts
[0].name
[0] == '\0')
3219 ret
= cgroup_init_cftypes(ss
, cfts
);
3223 mutex_lock(&cgroup_mutex
);
3225 list_add_tail(&cfts
->node
, &ss
->cfts
);
3226 ret
= cgroup_apply_cftypes(cfts
, true);
3228 cgroup_rm_cftypes_locked(cfts
);
3230 mutex_unlock(&cgroup_mutex
);
3235 * cgroup_add_dfl_cftypes - add an array of cftypes for default hierarchy
3236 * @ss: target cgroup subsystem
3237 * @cfts: zero-length name terminated array of cftypes
3239 * Similar to cgroup_add_cftypes() but the added files are only used for
3240 * the default hierarchy.
3242 int cgroup_add_dfl_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3246 for (cft
= cfts
; cft
&& cft
->name
[0] != '\0'; cft
++)
3247 cft
->flags
|= __CFTYPE_ONLY_ON_DFL
;
3248 return cgroup_add_cftypes(ss
, cfts
);
3252 * cgroup_add_legacy_cftypes - add an array of cftypes for legacy hierarchies
3253 * @ss: target cgroup subsystem
3254 * @cfts: zero-length name terminated array of cftypes
3256 * Similar to cgroup_add_cftypes() but the added files are only used for
3257 * the legacy hierarchies.
3259 int cgroup_add_legacy_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3264 * If legacy_flies_on_dfl, we want to show the legacy files on the
3265 * dfl hierarchy but iff the target subsystem hasn't been updated
3266 * for the dfl hierarchy yet.
3268 if (!cgroup_legacy_files_on_dfl
||
3269 ss
->dfl_cftypes
!= ss
->legacy_cftypes
) {
3270 for (cft
= cfts
; cft
&& cft
->name
[0] != '\0'; cft
++)
3271 cft
->flags
|= __CFTYPE_NOT_ON_DFL
;
3274 return cgroup_add_cftypes(ss
, cfts
);
3278 * cgroup_task_count - count the number of tasks in a cgroup.
3279 * @cgrp: the cgroup in question
3281 * Return the number of tasks in the cgroup.
3283 static int cgroup_task_count(const struct cgroup
*cgrp
)
3286 struct cgrp_cset_link
*link
;
3288 down_read(&css_set_rwsem
);
3289 list_for_each_entry(link
, &cgrp
->cset_links
, cset_link
)
3290 count
+= atomic_read(&link
->cset
->refcount
);
3291 up_read(&css_set_rwsem
);
3296 * css_next_child - find the next child of a given css
3297 * @pos: the current position (%NULL to initiate traversal)
3298 * @parent: css whose children to walk
3300 * This function returns the next child of @parent and should be called
3301 * under either cgroup_mutex or RCU read lock. The only requirement is
3302 * that @parent and @pos are accessible. The next sibling is guaranteed to
3303 * be returned regardless of their states.
3305 * If a subsystem synchronizes ->css_online() and the start of iteration, a
3306 * css which finished ->css_online() is guaranteed to be visible in the
3307 * future iterations and will stay visible until the last reference is put.
3308 * A css which hasn't finished ->css_online() or already finished
3309 * ->css_offline() may show up during traversal. It's each subsystem's
3310 * responsibility to synchronize against on/offlining.
3312 struct cgroup_subsys_state
*css_next_child(struct cgroup_subsys_state
*pos
,
3313 struct cgroup_subsys_state
*parent
)
3315 struct cgroup_subsys_state
*next
;
3317 cgroup_assert_mutex_or_rcu_locked();
3320 * @pos could already have been unlinked from the sibling list.
3321 * Once a cgroup is removed, its ->sibling.next is no longer
3322 * updated when its next sibling changes. CSS_RELEASED is set when
3323 * @pos is taken off list, at which time its next pointer is valid,
3324 * and, as releases are serialized, the one pointed to by the next
3325 * pointer is guaranteed to not have started release yet. This
3326 * implies that if we observe !CSS_RELEASED on @pos in this RCU
3327 * critical section, the one pointed to by its next pointer is
3328 * guaranteed to not have finished its RCU grace period even if we
3329 * have dropped rcu_read_lock() inbetween iterations.
3331 * If @pos has CSS_RELEASED set, its next pointer can't be
3332 * dereferenced; however, as each css is given a monotonically
3333 * increasing unique serial number and always appended to the
3334 * sibling list, the next one can be found by walking the parent's
3335 * children until the first css with higher serial number than
3336 * @pos's. While this path can be slower, it happens iff iteration
3337 * races against release and the race window is very small.
3340 next
= list_entry_rcu(parent
->children
.next
, struct cgroup_subsys_state
, sibling
);
3341 } else if (likely(!(pos
->flags
& CSS_RELEASED
))) {
3342 next
= list_entry_rcu(pos
->sibling
.next
, struct cgroup_subsys_state
, sibling
);
3344 list_for_each_entry_rcu(next
, &parent
->children
, sibling
)
3345 if (next
->serial_nr
> pos
->serial_nr
)
3350 * @next, if not pointing to the head, can be dereferenced and is
3353 if (&next
->sibling
!= &parent
->children
)
3359 * css_next_descendant_pre - find the next descendant for pre-order walk
3360 * @pos: the current position (%NULL to initiate traversal)
3361 * @root: css whose descendants to walk
3363 * To be used by css_for_each_descendant_pre(). Find the next descendant
3364 * to visit for pre-order traversal of @root's descendants. @root is
3365 * included in the iteration and the first node to be visited.
3367 * While this function requires cgroup_mutex or RCU read locking, it
3368 * doesn't require the whole traversal to be contained in a single critical
3369 * section. This function will return the correct next descendant as long
3370 * as both @pos and @root are accessible and @pos is a descendant of @root.
3372 * If a subsystem synchronizes ->css_online() and the start of iteration, a
3373 * css which finished ->css_online() is guaranteed to be visible in the
3374 * future iterations and will stay visible until the last reference is put.
3375 * A css which hasn't finished ->css_online() or already finished
3376 * ->css_offline() may show up during traversal. It's each subsystem's
3377 * responsibility to synchronize against on/offlining.
3379 struct cgroup_subsys_state
*
3380 css_next_descendant_pre(struct cgroup_subsys_state
*pos
,
3381 struct cgroup_subsys_state
*root
)
3383 struct cgroup_subsys_state
*next
;
3385 cgroup_assert_mutex_or_rcu_locked();
3387 /* if first iteration, visit @root */
3391 /* visit the first child if exists */
3392 next
= css_next_child(NULL
, pos
);
3396 /* no child, visit my or the closest ancestor's next sibling */
3397 while (pos
!= root
) {
3398 next
= css_next_child(pos
, pos
->parent
);
3408 * css_rightmost_descendant - return the rightmost descendant of a css
3409 * @pos: css of interest
3411 * Return the rightmost descendant of @pos. If there's no descendant, @pos
3412 * is returned. This can be used during pre-order traversal to skip
3415 * While this function requires cgroup_mutex or RCU read locking, it
3416 * doesn't require the whole traversal to be contained in a single critical
3417 * section. This function will return the correct rightmost descendant as
3418 * long as @pos is accessible.
3420 struct cgroup_subsys_state
*
3421 css_rightmost_descendant(struct cgroup_subsys_state
*pos
)
3423 struct cgroup_subsys_state
*last
, *tmp
;
3425 cgroup_assert_mutex_or_rcu_locked();
3429 /* ->prev isn't RCU safe, walk ->next till the end */
3431 css_for_each_child(tmp
, last
)
3438 static struct cgroup_subsys_state
*
3439 css_leftmost_descendant(struct cgroup_subsys_state
*pos
)
3441 struct cgroup_subsys_state
*last
;
3445 pos
= css_next_child(NULL
, pos
);
3452 * css_next_descendant_post - find the next descendant for post-order walk
3453 * @pos: the current position (%NULL to initiate traversal)
3454 * @root: css whose descendants to walk
3456 * To be used by css_for_each_descendant_post(). Find the next descendant
3457 * to visit for post-order traversal of @root's descendants. @root is
3458 * included in the iteration and the last node to be visited.
3460 * While this function requires cgroup_mutex or RCU read locking, it
3461 * doesn't require the whole traversal to be contained in a single critical
3462 * section. This function will return the correct next descendant as long
3463 * as both @pos and @cgroup are accessible and @pos is a descendant of
3466 * If a subsystem synchronizes ->css_online() and the start of iteration, a
3467 * css which finished ->css_online() is guaranteed to be visible in the
3468 * future iterations and will stay visible until the last reference is put.
3469 * A css which hasn't finished ->css_online() or already finished
3470 * ->css_offline() may show up during traversal. It's each subsystem's
3471 * responsibility to synchronize against on/offlining.
3473 struct cgroup_subsys_state
*
3474 css_next_descendant_post(struct cgroup_subsys_state
*pos
,
3475 struct cgroup_subsys_state
*root
)
3477 struct cgroup_subsys_state
*next
;
3479 cgroup_assert_mutex_or_rcu_locked();
3481 /* if first iteration, visit leftmost descendant which may be @root */
3483 return css_leftmost_descendant(root
);
3485 /* if we visited @root, we're done */
3489 /* if there's an unvisited sibling, visit its leftmost descendant */
3490 next
= css_next_child(pos
, pos
->parent
);
3492 return css_leftmost_descendant(next
);
3494 /* no sibling left, visit parent */
3499 * css_has_online_children - does a css have online children
3500 * @css: the target css
3502 * Returns %true if @css has any online children; otherwise, %false. This
3503 * function can be called from any context but the caller is responsible
3504 * for synchronizing against on/offlining as necessary.
3506 bool css_has_online_children(struct cgroup_subsys_state
*css
)
3508 struct cgroup_subsys_state
*child
;
3512 css_for_each_child(child
, css
) {
3513 if (child
->flags
& CSS_ONLINE
) {
3523 * css_advance_task_iter - advance a task itererator to the next css_set
3524 * @it: the iterator to advance
3526 * Advance @it to the next css_set to walk.
3528 static void css_advance_task_iter(struct css_task_iter
*it
)
3530 struct list_head
*l
= it
->cset_pos
;
3531 struct cgrp_cset_link
*link
;
3532 struct css_set
*cset
;
3534 /* Advance to the next non-empty css_set */
3537 if (l
== it
->cset_head
) {
3538 it
->cset_pos
= NULL
;
3543 cset
= container_of(l
, struct css_set
,
3544 e_cset_node
[it
->ss
->id
]);
3546 link
= list_entry(l
, struct cgrp_cset_link
, cset_link
);
3549 } while (list_empty(&cset
->tasks
) && list_empty(&cset
->mg_tasks
));
3553 if (!list_empty(&cset
->tasks
))
3554 it
->task_pos
= cset
->tasks
.next
;
3556 it
->task_pos
= cset
->mg_tasks
.next
;
3558 it
->tasks_head
= &cset
->tasks
;
3559 it
->mg_tasks_head
= &cset
->mg_tasks
;
3563 * css_task_iter_start - initiate task iteration
3564 * @css: the css to walk tasks of
3565 * @it: the task iterator to use
3567 * Initiate iteration through the tasks of @css. The caller can call
3568 * css_task_iter_next() to walk through the tasks until the function
3569 * returns NULL. On completion of iteration, css_task_iter_end() must be
3572 * Note that this function acquires a lock which is released when the
3573 * iteration finishes. The caller can't sleep while iteration is in
3576 void css_task_iter_start(struct cgroup_subsys_state
*css
,
3577 struct css_task_iter
*it
)
3578 __acquires(css_set_rwsem
)
3580 /* no one should try to iterate before mounting cgroups */
3581 WARN_ON_ONCE(!use_task_css_set_links
);
3583 down_read(&css_set_rwsem
);
3588 it
->cset_pos
= &css
->cgroup
->e_csets
[css
->ss
->id
];
3590 it
->cset_pos
= &css
->cgroup
->cset_links
;
3592 it
->cset_head
= it
->cset_pos
;
3594 css_advance_task_iter(it
);
3598 * css_task_iter_next - return the next task for the iterator
3599 * @it: the task iterator being iterated
3601 * The "next" function for task iteration. @it should have been
3602 * initialized via css_task_iter_start(). Returns NULL when the iteration
3605 struct task_struct
*css_task_iter_next(struct css_task_iter
*it
)
3607 struct task_struct
*res
;
3608 struct list_head
*l
= it
->task_pos
;
3610 /* If the iterator cg is NULL, we have no tasks */
3613 res
= list_entry(l
, struct task_struct
, cg_list
);
3616 * Advance iterator to find next entry. cset->tasks is consumed
3617 * first and then ->mg_tasks. After ->mg_tasks, we move onto the
3622 if (l
== it
->tasks_head
)
3623 l
= it
->mg_tasks_head
->next
;
3625 if (l
== it
->mg_tasks_head
)
3626 css_advance_task_iter(it
);
3634 * css_task_iter_end - finish task iteration
3635 * @it: the task iterator to finish
3637 * Finish task iteration started by css_task_iter_start().
3639 void css_task_iter_end(struct css_task_iter
*it
)
3640 __releases(css_set_rwsem
)
3642 up_read(&css_set_rwsem
);
3646 * cgroup_trasnsfer_tasks - move tasks from one cgroup to another
3647 * @to: cgroup to which the tasks will be moved
3648 * @from: cgroup in which the tasks currently reside
3650 * Locking rules between cgroup_post_fork() and the migration path
3651 * guarantee that, if a task is forking while being migrated, the new child
3652 * is guaranteed to be either visible in the source cgroup after the
3653 * parent's migration is complete or put into the target cgroup. No task
3654 * can slip out of migration through forking.
3656 int cgroup_transfer_tasks(struct cgroup
*to
, struct cgroup
*from
)
3658 LIST_HEAD(preloaded_csets
);
3659 struct cgrp_cset_link
*link
;
3660 struct css_task_iter it
;
3661 struct task_struct
*task
;
3664 mutex_lock(&cgroup_mutex
);
3666 /* all tasks in @from are being moved, all csets are source */
3667 down_read(&css_set_rwsem
);
3668 list_for_each_entry(link
, &from
->cset_links
, cset_link
)
3669 cgroup_migrate_add_src(link
->cset
, to
, &preloaded_csets
);
3670 up_read(&css_set_rwsem
);
3672 ret
= cgroup_migrate_prepare_dst(to
, &preloaded_csets
);
3677 * Migrate tasks one-by-one until @form is empty. This fails iff
3678 * ->can_attach() fails.
3681 css_task_iter_start(&from
->self
, &it
);
3682 task
= css_task_iter_next(&it
);
3684 get_task_struct(task
);
3685 css_task_iter_end(&it
);
3688 ret
= cgroup_migrate(to
, task
, false);
3689 put_task_struct(task
);
3691 } while (task
&& !ret
);
3693 cgroup_migrate_finish(&preloaded_csets
);
3694 mutex_unlock(&cgroup_mutex
);
3699 * Stuff for reading the 'tasks'/'procs' files.
3701 * Reading this file can return large amounts of data if a cgroup has
3702 * *lots* of attached tasks. So it may need several calls to read(),
3703 * but we cannot guarantee that the information we produce is correct
3704 * unless we produce it entirely atomically.
3708 /* which pidlist file are we talking about? */
3709 enum cgroup_filetype
{
3715 * A pidlist is a list of pids that virtually represents the contents of one
3716 * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
3717 * a pair (one each for procs, tasks) for each pid namespace that's relevant
3720 struct cgroup_pidlist
{
3722 * used to find which pidlist is wanted. doesn't change as long as
3723 * this particular list stays in the list.
3725 struct { enum cgroup_filetype type
; struct pid_namespace
*ns
; } key
;
3728 /* how many elements the above list has */
3730 /* each of these stored in a list by its cgroup */
3731 struct list_head links
;
3732 /* pointer to the cgroup we belong to, for list removal purposes */
3733 struct cgroup
*owner
;
3734 /* for delayed destruction */
3735 struct delayed_work destroy_dwork
;
3739 * The following two functions "fix" the issue where there are more pids
3740 * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
3741 * TODO: replace with a kernel-wide solution to this problem
3743 #define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
3744 static void *pidlist_allocate(int count
)
3746 if (PIDLIST_TOO_LARGE(count
))
3747 return vmalloc(count
* sizeof(pid_t
));
3749 return kmalloc(count
* sizeof(pid_t
), GFP_KERNEL
);
3752 static void pidlist_free(void *p
)
3754 if (is_vmalloc_addr(p
))
3761 * Used to destroy all pidlists lingering waiting for destroy timer. None
3762 * should be left afterwards.
3764 static void cgroup_pidlist_destroy_all(struct cgroup
*cgrp
)
3766 struct cgroup_pidlist
*l
, *tmp_l
;
3768 mutex_lock(&cgrp
->pidlist_mutex
);
3769 list_for_each_entry_safe(l
, tmp_l
, &cgrp
->pidlists
, links
)
3770 mod_delayed_work(cgroup_pidlist_destroy_wq
, &l
->destroy_dwork
, 0);
3771 mutex_unlock(&cgrp
->pidlist_mutex
);
3773 flush_workqueue(cgroup_pidlist_destroy_wq
);
3774 BUG_ON(!list_empty(&cgrp
->pidlists
));
3777 static void cgroup_pidlist_destroy_work_fn(struct work_struct
*work
)
3779 struct delayed_work
*dwork
= to_delayed_work(work
);
3780 struct cgroup_pidlist
*l
= container_of(dwork
, struct cgroup_pidlist
,
3782 struct cgroup_pidlist
*tofree
= NULL
;
3784 mutex_lock(&l
->owner
->pidlist_mutex
);
3787 * Destroy iff we didn't get queued again. The state won't change
3788 * as destroy_dwork can only be queued while locked.
3790 if (!delayed_work_pending(dwork
)) {
3791 list_del(&l
->links
);
3792 pidlist_free(l
->list
);
3793 put_pid_ns(l
->key
.ns
);
3797 mutex_unlock(&l
->owner
->pidlist_mutex
);
3802 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
3803 * Returns the number of unique elements.
3805 static int pidlist_uniq(pid_t
*list
, int length
)
3810 * we presume the 0th element is unique, so i starts at 1. trivial
3811 * edge cases first; no work needs to be done for either
3813 if (length
== 0 || length
== 1)
3815 /* src and dest walk down the list; dest counts unique elements */
3816 for (src
= 1; src
< length
; src
++) {
3817 /* find next unique element */
3818 while (list
[src
] == list
[src
-1]) {
3823 /* dest always points to where the next unique element goes */
3824 list
[dest
] = list
[src
];
3832 * The two pid files - task and cgroup.procs - guaranteed that the result
3833 * is sorted, which forced this whole pidlist fiasco. As pid order is
3834 * different per namespace, each namespace needs differently sorted list,
3835 * making it impossible to use, for example, single rbtree of member tasks
3836 * sorted by task pointer. As pidlists can be fairly large, allocating one
3837 * per open file is dangerous, so cgroup had to implement shared pool of
3838 * pidlists keyed by cgroup and namespace.
3840 * All this extra complexity was caused by the original implementation
3841 * committing to an entirely unnecessary property. In the long term, we
3842 * want to do away with it. Explicitly scramble sort order if on the
3843 * default hierarchy so that no such expectation exists in the new
3846 * Scrambling is done by swapping every two consecutive bits, which is
3847 * non-identity one-to-one mapping which disturbs sort order sufficiently.
3849 static pid_t
pid_fry(pid_t pid
)
3851 unsigned a
= pid
& 0x55555555;
3852 unsigned b
= pid
& 0xAAAAAAAA;
3854 return (a
<< 1) | (b
>> 1);
3857 static pid_t
cgroup_pid_fry(struct cgroup
*cgrp
, pid_t pid
)
3859 if (cgroup_on_dfl(cgrp
))
3860 return pid_fry(pid
);
3865 static int cmppid(const void *a
, const void *b
)
3867 return *(pid_t
*)a
- *(pid_t
*)b
;
3870 static int fried_cmppid(const void *a
, const void *b
)
3872 return pid_fry(*(pid_t
*)a
) - pid_fry(*(pid_t
*)b
);
3875 static struct cgroup_pidlist
*cgroup_pidlist_find(struct cgroup
*cgrp
,
3876 enum cgroup_filetype type
)
3878 struct cgroup_pidlist
*l
;
3879 /* don't need task_nsproxy() if we're looking at ourself */
3880 struct pid_namespace
*ns
= task_active_pid_ns(current
);
3882 lockdep_assert_held(&cgrp
->pidlist_mutex
);
3884 list_for_each_entry(l
, &cgrp
->pidlists
, links
)
3885 if (l
->key
.type
== type
&& l
->key
.ns
== ns
)
3891 * find the appropriate pidlist for our purpose (given procs vs tasks)
3892 * returns with the lock on that pidlist already held, and takes care
3893 * of the use count, or returns NULL with no locks held if we're out of
3896 static struct cgroup_pidlist
*cgroup_pidlist_find_create(struct cgroup
*cgrp
,
3897 enum cgroup_filetype type
)
3899 struct cgroup_pidlist
*l
;
3901 lockdep_assert_held(&cgrp
->pidlist_mutex
);
3903 l
= cgroup_pidlist_find(cgrp
, type
);
3907 /* entry not found; create a new one */
3908 l
= kzalloc(sizeof(struct cgroup_pidlist
), GFP_KERNEL
);
3912 INIT_DELAYED_WORK(&l
->destroy_dwork
, cgroup_pidlist_destroy_work_fn
);
3914 /* don't need task_nsproxy() if we're looking at ourself */
3915 l
->key
.ns
= get_pid_ns(task_active_pid_ns(current
));
3917 list_add(&l
->links
, &cgrp
->pidlists
);
3922 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
3924 static int pidlist_array_load(struct cgroup
*cgrp
, enum cgroup_filetype type
,
3925 struct cgroup_pidlist
**lp
)
3929 int pid
, n
= 0; /* used for populating the array */
3930 struct css_task_iter it
;
3931 struct task_struct
*tsk
;
3932 struct cgroup_pidlist
*l
;
3934 lockdep_assert_held(&cgrp
->pidlist_mutex
);
3937 * If cgroup gets more users after we read count, we won't have
3938 * enough space - tough. This race is indistinguishable to the
3939 * caller from the case that the additional cgroup users didn't
3940 * show up until sometime later on.
3942 length
= cgroup_task_count(cgrp
);
3943 array
= pidlist_allocate(length
);
3946 /* now, populate the array */
3947 css_task_iter_start(&cgrp
->self
, &it
);
3948 while ((tsk
= css_task_iter_next(&it
))) {
3949 if (unlikely(n
== length
))
3951 /* get tgid or pid for procs or tasks file respectively */
3952 if (type
== CGROUP_FILE_PROCS
)
3953 pid
= task_tgid_vnr(tsk
);
3955 pid
= task_pid_vnr(tsk
);
3956 if (pid
> 0) /* make sure to only use valid results */
3959 css_task_iter_end(&it
);
3961 /* now sort & (if procs) strip out duplicates */
3962 if (cgroup_on_dfl(cgrp
))
3963 sort(array
, length
, sizeof(pid_t
), fried_cmppid
, NULL
);
3965 sort(array
, length
, sizeof(pid_t
), cmppid
, NULL
);
3966 if (type
== CGROUP_FILE_PROCS
)
3967 length
= pidlist_uniq(array
, length
);
3969 l
= cgroup_pidlist_find_create(cgrp
, type
);
3971 pidlist_free(array
);
3975 /* store array, freeing old if necessary */
3976 pidlist_free(l
->list
);
3984 * cgroupstats_build - build and fill cgroupstats
3985 * @stats: cgroupstats to fill information into
3986 * @dentry: A dentry entry belonging to the cgroup for which stats have
3989 * Build and fill cgroupstats so that taskstats can export it to user
3992 int cgroupstats_build(struct cgroupstats
*stats
, struct dentry
*dentry
)
3994 struct kernfs_node
*kn
= kernfs_node_from_dentry(dentry
);
3995 struct cgroup
*cgrp
;
3996 struct css_task_iter it
;
3997 struct task_struct
*tsk
;
3999 /* it should be kernfs_node belonging to cgroupfs and is a directory */
4000 if (dentry
->d_sb
->s_type
!= &cgroup_fs_type
|| !kn
||
4001 kernfs_type(kn
) != KERNFS_DIR
)
4004 mutex_lock(&cgroup_mutex
);
4007 * We aren't being called from kernfs and there's no guarantee on
4008 * @kn->priv's validity. For this and css_tryget_online_from_dir(),
4009 * @kn->priv is RCU safe. Let's do the RCU dancing.
4012 cgrp
= rcu_dereference(kn
->priv
);
4013 if (!cgrp
|| cgroup_is_dead(cgrp
)) {
4015 mutex_unlock(&cgroup_mutex
);
4020 css_task_iter_start(&cgrp
->self
, &it
);
4021 while ((tsk
= css_task_iter_next(&it
))) {
4022 switch (tsk
->state
) {
4024 stats
->nr_running
++;
4026 case TASK_INTERRUPTIBLE
:
4027 stats
->nr_sleeping
++;
4029 case TASK_UNINTERRUPTIBLE
:
4030 stats
->nr_uninterruptible
++;
4033 stats
->nr_stopped
++;
4036 if (delayacct_is_task_waiting_on_io(tsk
))
4037 stats
->nr_io_wait
++;
4041 css_task_iter_end(&it
);
4043 mutex_unlock(&cgroup_mutex
);
4049 * seq_file methods for the tasks/procs files. The seq_file position is the
4050 * next pid to display; the seq_file iterator is a pointer to the pid
4051 * in the cgroup->l->list array.
4054 static void *cgroup_pidlist_start(struct seq_file
*s
, loff_t
*pos
)
4057 * Initially we receive a position value that corresponds to
4058 * one more than the last pid shown (or 0 on the first call or
4059 * after a seek to the start). Use a binary-search to find the
4060 * next pid to display, if any
4062 struct kernfs_open_file
*of
= s
->private;
4063 struct cgroup
*cgrp
= seq_css(s
)->cgroup
;
4064 struct cgroup_pidlist
*l
;
4065 enum cgroup_filetype type
= seq_cft(s
)->private;
4066 int index
= 0, pid
= *pos
;
4069 mutex_lock(&cgrp
->pidlist_mutex
);
4072 * !NULL @of->priv indicates that this isn't the first start()
4073 * after open. If the matching pidlist is around, we can use that.
4074 * Look for it. Note that @of->priv can't be used directly. It
4075 * could already have been destroyed.
4078 of
->priv
= cgroup_pidlist_find(cgrp
, type
);
4081 * Either this is the first start() after open or the matching
4082 * pidlist has been destroyed inbetween. Create a new one.
4085 ret
= pidlist_array_load(cgrp
, type
,
4086 (struct cgroup_pidlist
**)&of
->priv
);
4088 return ERR_PTR(ret
);
4093 int end
= l
->length
;
4095 while (index
< end
) {
4096 int mid
= (index
+ end
) / 2;
4097 if (cgroup_pid_fry(cgrp
, l
->list
[mid
]) == pid
) {
4100 } else if (cgroup_pid_fry(cgrp
, l
->list
[mid
]) <= pid
)
4106 /* If we're off the end of the array, we're done */
4107 if (index
>= l
->length
)
4109 /* Update the abstract position to be the actual pid that we found */
4110 iter
= l
->list
+ index
;
4111 *pos
= cgroup_pid_fry(cgrp
, *iter
);
4115 static void cgroup_pidlist_stop(struct seq_file
*s
, void *v
)
4117 struct kernfs_open_file
*of
= s
->private;
4118 struct cgroup_pidlist
*l
= of
->priv
;
4121 mod_delayed_work(cgroup_pidlist_destroy_wq
, &l
->destroy_dwork
,
4122 CGROUP_PIDLIST_DESTROY_DELAY
);
4123 mutex_unlock(&seq_css(s
)->cgroup
->pidlist_mutex
);
4126 static void *cgroup_pidlist_next(struct seq_file
*s
, void *v
, loff_t
*pos
)
4128 struct kernfs_open_file
*of
= s
->private;
4129 struct cgroup_pidlist
*l
= of
->priv
;
4131 pid_t
*end
= l
->list
+ l
->length
;
4133 * Advance to the next pid in the array. If this goes off the
4140 *pos
= cgroup_pid_fry(seq_css(s
)->cgroup
, *p
);
4145 static int cgroup_pidlist_show(struct seq_file
*s
, void *v
)
4147 return seq_printf(s
, "%d\n", *(int *)v
);
4150 static u64
cgroup_read_notify_on_release(struct cgroup_subsys_state
*css
,
4153 return notify_on_release(css
->cgroup
);
4156 static int cgroup_write_notify_on_release(struct cgroup_subsys_state
*css
,
4157 struct cftype
*cft
, u64 val
)
4160 set_bit(CGRP_NOTIFY_ON_RELEASE
, &css
->cgroup
->flags
);
4162 clear_bit(CGRP_NOTIFY_ON_RELEASE
, &css
->cgroup
->flags
);
4166 static u64
cgroup_clone_children_read(struct cgroup_subsys_state
*css
,
4169 return test_bit(CGRP_CPUSET_CLONE_CHILDREN
, &css
->cgroup
->flags
);
4172 static int cgroup_clone_children_write(struct cgroup_subsys_state
*css
,
4173 struct cftype
*cft
, u64 val
)
4176 set_bit(CGRP_CPUSET_CLONE_CHILDREN
, &css
->cgroup
->flags
);
4178 clear_bit(CGRP_CPUSET_CLONE_CHILDREN
, &css
->cgroup
->flags
);
4182 /* cgroup core interface files for the default hierarchy */
4183 static struct cftype cgroup_dfl_base_files
[] = {
4185 .name
= "cgroup.procs",
4186 .seq_start
= cgroup_pidlist_start
,
4187 .seq_next
= cgroup_pidlist_next
,
4188 .seq_stop
= cgroup_pidlist_stop
,
4189 .seq_show
= cgroup_pidlist_show
,
4190 .private = CGROUP_FILE_PROCS
,
4191 .write
= cgroup_procs_write
,
4192 .mode
= S_IRUGO
| S_IWUSR
,
4195 .name
= "cgroup.controllers",
4196 .flags
= CFTYPE_ONLY_ON_ROOT
,
4197 .seq_show
= cgroup_root_controllers_show
,
4200 .name
= "cgroup.controllers",
4201 .flags
= CFTYPE_NOT_ON_ROOT
,
4202 .seq_show
= cgroup_controllers_show
,
4205 .name
= "cgroup.subtree_control",
4206 .seq_show
= cgroup_subtree_control_show
,
4207 .write
= cgroup_subtree_control_write
,
4210 .name
= "cgroup.populated",
4211 .flags
= CFTYPE_NOT_ON_ROOT
,
4212 .seq_show
= cgroup_populated_show
,
4217 /* cgroup core interface files for the legacy hierarchies */
4218 static struct cftype cgroup_legacy_base_files
[] = {
4220 .name
= "cgroup.procs",
4221 .seq_start
= cgroup_pidlist_start
,
4222 .seq_next
= cgroup_pidlist_next
,
4223 .seq_stop
= cgroup_pidlist_stop
,
4224 .seq_show
= cgroup_pidlist_show
,
4225 .private = CGROUP_FILE_PROCS
,
4226 .write
= cgroup_procs_write
,
4227 .mode
= S_IRUGO
| S_IWUSR
,
4230 .name
= "cgroup.clone_children",
4231 .read_u64
= cgroup_clone_children_read
,
4232 .write_u64
= cgroup_clone_children_write
,
4235 .name
= "cgroup.sane_behavior",
4236 .flags
= CFTYPE_ONLY_ON_ROOT
,
4237 .seq_show
= cgroup_sane_behavior_show
,
4241 .seq_start
= cgroup_pidlist_start
,
4242 .seq_next
= cgroup_pidlist_next
,
4243 .seq_stop
= cgroup_pidlist_stop
,
4244 .seq_show
= cgroup_pidlist_show
,
4245 .private = CGROUP_FILE_TASKS
,
4246 .write
= cgroup_tasks_write
,
4247 .mode
= S_IRUGO
| S_IWUSR
,
4250 .name
= "notify_on_release",
4251 .read_u64
= cgroup_read_notify_on_release
,
4252 .write_u64
= cgroup_write_notify_on_release
,
4255 .name
= "release_agent",
4256 .flags
= CFTYPE_ONLY_ON_ROOT
,
4257 .seq_show
= cgroup_release_agent_show
,
4258 .write
= cgroup_release_agent_write
,
4259 .max_write_len
= PATH_MAX
- 1,
4265 * cgroup_populate_dir - create subsys files in a cgroup directory
4266 * @cgrp: target cgroup
4267 * @subsys_mask: mask of the subsystem ids whose files should be added
4269 * On failure, no file is added.
4271 static int cgroup_populate_dir(struct cgroup
*cgrp
, unsigned int subsys_mask
)
4273 struct cgroup_subsys
*ss
;
4276 /* process cftsets of each subsystem */
4277 for_each_subsys(ss
, i
) {
4278 struct cftype
*cfts
;
4280 if (!(subsys_mask
& (1 << i
)))
4283 list_for_each_entry(cfts
, &ss
->cfts
, node
) {
4284 ret
= cgroup_addrm_files(cgrp
, cfts
, true);
4291 cgroup_clear_dir(cgrp
, subsys_mask
);
4296 * css destruction is four-stage process.
4298 * 1. Destruction starts. Killing of the percpu_ref is initiated.
4299 * Implemented in kill_css().
4301 * 2. When the percpu_ref is confirmed to be visible as killed on all CPUs
4302 * and thus css_tryget_online() is guaranteed to fail, the css can be
4303 * offlined by invoking offline_css(). After offlining, the base ref is
4304 * put. Implemented in css_killed_work_fn().
4306 * 3. When the percpu_ref reaches zero, the only possible remaining
4307 * accessors are inside RCU read sections. css_release() schedules the
4310 * 4. After the grace period, the css can be freed. Implemented in
4311 * css_free_work_fn().
4313 * It is actually hairier because both step 2 and 4 require process context
4314 * and thus involve punting to css->destroy_work adding two additional
4315 * steps to the already complex sequence.
4317 static void css_free_work_fn(struct work_struct
*work
)
4319 struct cgroup_subsys_state
*css
=
4320 container_of(work
, struct cgroup_subsys_state
, destroy_work
);
4321 struct cgroup
*cgrp
= css
->cgroup
;
4323 percpu_ref_exit(&css
->refcnt
);
4328 css_put(css
->parent
);
4330 css
->ss
->css_free(css
);
4333 /* cgroup free path */
4334 atomic_dec(&cgrp
->root
->nr_cgrps
);
4335 cgroup_pidlist_destroy_all(cgrp
);
4336 cancel_work_sync(&cgrp
->release_agent_work
);
4338 if (cgroup_parent(cgrp
)) {
4340 * We get a ref to the parent, and put the ref when
4341 * this cgroup is being freed, so it's guaranteed
4342 * that the parent won't be destroyed before its
4345 cgroup_put(cgroup_parent(cgrp
));
4346 kernfs_put(cgrp
->kn
);
4350 * This is root cgroup's refcnt reaching zero,
4351 * which indicates that the root should be
4354 cgroup_destroy_root(cgrp
->root
);
4359 static void css_free_rcu_fn(struct rcu_head
*rcu_head
)
4361 struct cgroup_subsys_state
*css
=
4362 container_of(rcu_head
, struct cgroup_subsys_state
, rcu_head
);
4364 INIT_WORK(&css
->destroy_work
, css_free_work_fn
);
4365 queue_work(cgroup_destroy_wq
, &css
->destroy_work
);
4368 static void css_release_work_fn(struct work_struct
*work
)
4370 struct cgroup_subsys_state
*css
=
4371 container_of(work
, struct cgroup_subsys_state
, destroy_work
);
4372 struct cgroup_subsys
*ss
= css
->ss
;
4373 struct cgroup
*cgrp
= css
->cgroup
;
4375 mutex_lock(&cgroup_mutex
);
4377 css
->flags
|= CSS_RELEASED
;
4378 list_del_rcu(&css
->sibling
);
4381 /* css release path */
4382 cgroup_idr_remove(&ss
->css_idr
, css
->id
);
4383 if (ss
->css_released
)
4384 ss
->css_released(css
);
4386 /* cgroup release path */
4387 cgroup_idr_remove(&cgrp
->root
->cgroup_idr
, cgrp
->id
);
4391 * There are two control paths which try to determine
4392 * cgroup from dentry without going through kernfs -
4393 * cgroupstats_build() and css_tryget_online_from_dir().
4394 * Those are supported by RCU protecting clearing of
4395 * cgrp->kn->priv backpointer.
4397 RCU_INIT_POINTER(*(void __rcu __force
**)&cgrp
->kn
->priv
, NULL
);
4400 mutex_unlock(&cgroup_mutex
);
4402 call_rcu(&css
->rcu_head
, css_free_rcu_fn
);
4405 static void css_release(struct percpu_ref
*ref
)
4407 struct cgroup_subsys_state
*css
=
4408 container_of(ref
, struct cgroup_subsys_state
, refcnt
);
4410 INIT_WORK(&css
->destroy_work
, css_release_work_fn
);
4411 queue_work(cgroup_destroy_wq
, &css
->destroy_work
);
4414 static void init_and_link_css(struct cgroup_subsys_state
*css
,
4415 struct cgroup_subsys
*ss
, struct cgroup
*cgrp
)
4417 lockdep_assert_held(&cgroup_mutex
);
4421 memset(css
, 0, sizeof(*css
));
4424 INIT_LIST_HEAD(&css
->sibling
);
4425 INIT_LIST_HEAD(&css
->children
);
4426 css
->serial_nr
= css_serial_nr_next
++;
4428 if (cgroup_parent(cgrp
)) {
4429 css
->parent
= cgroup_css(cgroup_parent(cgrp
), ss
);
4430 css_get(css
->parent
);
4433 BUG_ON(cgroup_css(cgrp
, ss
));
4436 /* invoke ->css_online() on a new CSS and mark it online if successful */
4437 static int online_css(struct cgroup_subsys_state
*css
)
4439 struct cgroup_subsys
*ss
= css
->ss
;
4442 lockdep_assert_held(&cgroup_mutex
);
4445 ret
= ss
->css_online(css
);
4447 css
->flags
|= CSS_ONLINE
;
4448 rcu_assign_pointer(css
->cgroup
->subsys
[ss
->id
], css
);
4453 /* if the CSS is online, invoke ->css_offline() on it and mark it offline */
4454 static void offline_css(struct cgroup_subsys_state
*css
)
4456 struct cgroup_subsys
*ss
= css
->ss
;
4458 lockdep_assert_held(&cgroup_mutex
);
4460 if (!(css
->flags
& CSS_ONLINE
))
4463 if (ss
->css_offline
)
4464 ss
->css_offline(css
);
4466 css
->flags
&= ~CSS_ONLINE
;
4467 RCU_INIT_POINTER(css
->cgroup
->subsys
[ss
->id
], NULL
);
4469 wake_up_all(&css
->cgroup
->offline_waitq
);
4473 * create_css - create a cgroup_subsys_state
4474 * @cgrp: the cgroup new css will be associated with
4475 * @ss: the subsys of new css
4476 * @visible: whether to create control knobs for the new css or not
4478 * Create a new css associated with @cgrp - @ss pair. On success, the new
4479 * css is online and installed in @cgrp with all interface files created if
4480 * @visible. Returns 0 on success, -errno on failure.
4482 static int create_css(struct cgroup
*cgrp
, struct cgroup_subsys
*ss
,
4485 struct cgroup
*parent
= cgroup_parent(cgrp
);
4486 struct cgroup_subsys_state
*parent_css
= cgroup_css(parent
, ss
);
4487 struct cgroup_subsys_state
*css
;
4490 lockdep_assert_held(&cgroup_mutex
);
4492 css
= ss
->css_alloc(parent_css
);
4494 return PTR_ERR(css
);
4496 init_and_link_css(css
, ss
, cgrp
);
4498 err
= percpu_ref_init(&css
->refcnt
, css_release
, 0, GFP_KERNEL
);
4502 err
= cgroup_idr_alloc(&ss
->css_idr
, NULL
, 2, 0, GFP_NOWAIT
);
4504 goto err_free_percpu_ref
;
4508 err
= cgroup_populate_dir(cgrp
, 1 << ss
->id
);
4513 /* @css is ready to be brought online now, make it visible */
4514 list_add_tail_rcu(&css
->sibling
, &parent_css
->children
);
4515 cgroup_idr_replace(&ss
->css_idr
, css
, css
->id
);
4517 err
= online_css(css
);
4521 if (ss
->broken_hierarchy
&& !ss
->warned_broken_hierarchy
&&
4522 cgroup_parent(parent
)) {
4523 pr_warn("%s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n",
4524 current
->comm
, current
->pid
, ss
->name
);
4525 if (!strcmp(ss
->name
, "memory"))
4526 pr_warn("\"memory\" requires setting use_hierarchy to 1 on the root\n");
4527 ss
->warned_broken_hierarchy
= true;
4533 list_del_rcu(&css
->sibling
);
4534 cgroup_clear_dir(css
->cgroup
, 1 << css
->ss
->id
);
4536 cgroup_idr_remove(&ss
->css_idr
, css
->id
);
4537 err_free_percpu_ref
:
4538 percpu_ref_exit(&css
->refcnt
);
4540 call_rcu(&css
->rcu_head
, css_free_rcu_fn
);
4544 static int cgroup_mkdir(struct kernfs_node
*parent_kn
, const char *name
,
4547 struct cgroup
*parent
, *cgrp
;
4548 struct cgroup_root
*root
;
4549 struct cgroup_subsys
*ss
;
4550 struct kernfs_node
*kn
;
4551 struct cftype
*base_files
;
4554 /* Do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable.
4556 if (strchr(name
, '\n'))
4559 parent
= cgroup_kn_lock_live(parent_kn
);
4562 root
= parent
->root
;
4564 /* allocate the cgroup and its ID, 0 is reserved for the root */
4565 cgrp
= kzalloc(sizeof(*cgrp
), GFP_KERNEL
);
4571 ret
= percpu_ref_init(&cgrp
->self
.refcnt
, css_release
, 0, GFP_KERNEL
);
4576 * Temporarily set the pointer to NULL, so idr_find() won't return
4577 * a half-baked cgroup.
4579 cgrp
->id
= cgroup_idr_alloc(&root
->cgroup_idr
, NULL
, 2, 0, GFP_NOWAIT
);
4582 goto out_cancel_ref
;
4585 init_cgroup_housekeeping(cgrp
);
4587 cgrp
->self
.parent
= &parent
->self
;
4590 if (notify_on_release(parent
))
4591 set_bit(CGRP_NOTIFY_ON_RELEASE
, &cgrp
->flags
);
4593 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN
, &parent
->flags
))
4594 set_bit(CGRP_CPUSET_CLONE_CHILDREN
, &cgrp
->flags
);
4596 /* create the directory */
4597 kn
= kernfs_create_dir(parent
->kn
, name
, mode
, cgrp
);
4605 * This extra ref will be put in cgroup_free_fn() and guarantees
4606 * that @cgrp->kn is always accessible.
4610 cgrp
->self
.serial_nr
= css_serial_nr_next
++;
4612 /* allocation complete, commit to creation */
4613 list_add_tail_rcu(&cgrp
->self
.sibling
, &cgroup_parent(cgrp
)->self
.children
);
4614 atomic_inc(&root
->nr_cgrps
);
4618 * @cgrp is now fully operational. If something fails after this
4619 * point, it'll be released via the normal destruction path.
4621 cgroup_idr_replace(&root
->cgroup_idr
, cgrp
, cgrp
->id
);
4623 ret
= cgroup_kn_set_ugid(kn
);
4627 if (cgroup_on_dfl(cgrp
))
4628 base_files
= cgroup_dfl_base_files
;
4630 base_files
= cgroup_legacy_base_files
;
4632 ret
= cgroup_addrm_files(cgrp
, base_files
, true);
4636 /* let's create and online css's */
4637 for_each_subsys(ss
, ssid
) {
4638 if (parent
->child_subsys_mask
& (1 << ssid
)) {
4639 ret
= create_css(cgrp
, ss
,
4640 parent
->subtree_control
& (1 << ssid
));
4647 * On the default hierarchy, a child doesn't automatically inherit
4648 * subtree_control from the parent. Each is configured manually.
4650 if (!cgroup_on_dfl(cgrp
)) {
4651 cgrp
->subtree_control
= parent
->subtree_control
;
4652 cgroup_refresh_child_subsys_mask(cgrp
);
4655 kernfs_activate(kn
);
4661 cgroup_idr_remove(&root
->cgroup_idr
, cgrp
->id
);
4663 percpu_ref_exit(&cgrp
->self
.refcnt
);
4667 cgroup_kn_unlock(parent_kn
);
4671 cgroup_destroy_locked(cgrp
);
4676 * This is called when the refcnt of a css is confirmed to be killed.
4677 * css_tryget_online() is now guaranteed to fail. Tell the subsystem to
4678 * initate destruction and put the css ref from kill_css().
4680 static void css_killed_work_fn(struct work_struct
*work
)
4682 struct cgroup_subsys_state
*css
=
4683 container_of(work
, struct cgroup_subsys_state
, destroy_work
);
4685 mutex_lock(&cgroup_mutex
);
4687 mutex_unlock(&cgroup_mutex
);
4692 /* css kill confirmation processing requires process context, bounce */
4693 static void css_killed_ref_fn(struct percpu_ref
*ref
)
4695 struct cgroup_subsys_state
*css
=
4696 container_of(ref
, struct cgroup_subsys_state
, refcnt
);
4698 INIT_WORK(&css
->destroy_work
, css_killed_work_fn
);
4699 queue_work(cgroup_destroy_wq
, &css
->destroy_work
);
4703 * kill_css - destroy a css
4704 * @css: css to destroy
4706 * This function initiates destruction of @css by removing cgroup interface
4707 * files and putting its base reference. ->css_offline() will be invoked
4708 * asynchronously once css_tryget_online() is guaranteed to fail and when
4709 * the reference count reaches zero, @css will be released.
4711 static void kill_css(struct cgroup_subsys_state
*css
)
4713 lockdep_assert_held(&cgroup_mutex
);
4716 * This must happen before css is disassociated with its cgroup.
4717 * See seq_css() for details.
4719 cgroup_clear_dir(css
->cgroup
, 1 << css
->ss
->id
);
4722 * Killing would put the base ref, but we need to keep it alive
4723 * until after ->css_offline().
4728 * cgroup core guarantees that, by the time ->css_offline() is
4729 * invoked, no new css reference will be given out via
4730 * css_tryget_online(). We can't simply call percpu_ref_kill() and
4731 * proceed to offlining css's because percpu_ref_kill() doesn't
4732 * guarantee that the ref is seen as killed on all CPUs on return.
4734 * Use percpu_ref_kill_and_confirm() to get notifications as each
4735 * css is confirmed to be seen as killed on all CPUs.
4737 percpu_ref_kill_and_confirm(&css
->refcnt
, css_killed_ref_fn
);
4741 * cgroup_destroy_locked - the first stage of cgroup destruction
4742 * @cgrp: cgroup to be destroyed
4744 * css's make use of percpu refcnts whose killing latency shouldn't be
4745 * exposed to userland and are RCU protected. Also, cgroup core needs to
4746 * guarantee that css_tryget_online() won't succeed by the time
4747 * ->css_offline() is invoked. To satisfy all the requirements,
4748 * destruction is implemented in the following two steps.
4750 * s1. Verify @cgrp can be destroyed and mark it dying. Remove all
4751 * userland visible parts and start killing the percpu refcnts of
4752 * css's. Set up so that the next stage will be kicked off once all
4753 * the percpu refcnts are confirmed to be killed.
4755 * s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the
4756 * rest of destruction. Once all cgroup references are gone, the
4757 * cgroup is RCU-freed.
4759 * This function implements s1. After this step, @cgrp is gone as far as
4760 * the userland is concerned and a new cgroup with the same name may be
4761 * created. As cgroup doesn't care about the names internally, this
4762 * doesn't cause any problem.
4764 static int cgroup_destroy_locked(struct cgroup
*cgrp
)
4765 __releases(&cgroup_mutex
) __acquires(&cgroup_mutex
)
4767 struct cgroup_subsys_state
*css
;
4771 lockdep_assert_held(&cgroup_mutex
);
4774 * css_set_rwsem synchronizes access to ->cset_links and prevents
4775 * @cgrp from being removed while put_css_set() is in progress.
4777 down_read(&css_set_rwsem
);
4778 empty
= list_empty(&cgrp
->cset_links
);
4779 up_read(&css_set_rwsem
);
4784 * Make sure there's no live children. We can't test emptiness of
4785 * ->self.children as dead children linger on it while being
4786 * drained; otherwise, "rmdir parent/child parent" may fail.
4788 if (css_has_online_children(&cgrp
->self
))
4792 * Mark @cgrp dead. This prevents further task migration and child
4793 * creation by disabling cgroup_lock_live_group().
4795 cgrp
->self
.flags
&= ~CSS_ONLINE
;
4797 /* initiate massacre of all css's */
4798 for_each_css(css
, ssid
, cgrp
)
4802 * Remove @cgrp directory along with the base files. @cgrp has an
4803 * extra ref on its kn.
4805 kernfs_remove(cgrp
->kn
);
4807 check_for_release(cgroup_parent(cgrp
));
4809 /* put the base reference */
4810 percpu_ref_kill(&cgrp
->self
.refcnt
);
4815 static int cgroup_rmdir(struct kernfs_node
*kn
)
4817 struct cgroup
*cgrp
;
4820 cgrp
= cgroup_kn_lock_live(kn
);
4824 ret
= cgroup_destroy_locked(cgrp
);
4826 cgroup_kn_unlock(kn
);
4830 static struct kernfs_syscall_ops cgroup_kf_syscall_ops
= {
4831 .remount_fs
= cgroup_remount
,
4832 .show_options
= cgroup_show_options
,
4833 .mkdir
= cgroup_mkdir
,
4834 .rmdir
= cgroup_rmdir
,
4835 .rename
= cgroup_rename
,
4838 static void __init
cgroup_init_subsys(struct cgroup_subsys
*ss
, bool early
)
4840 struct cgroup_subsys_state
*css
;
4842 printk(KERN_INFO
"Initializing cgroup subsys %s\n", ss
->name
);
4844 mutex_lock(&cgroup_mutex
);
4846 idr_init(&ss
->css_idr
);
4847 INIT_LIST_HEAD(&ss
->cfts
);
4849 /* Create the root cgroup state for this subsystem */
4850 ss
->root
= &cgrp_dfl_root
;
4851 css
= ss
->css_alloc(cgroup_css(&cgrp_dfl_root
.cgrp
, ss
));
4852 /* We don't handle early failures gracefully */
4853 BUG_ON(IS_ERR(css
));
4854 init_and_link_css(css
, ss
, &cgrp_dfl_root
.cgrp
);
4857 * Root csses are never destroyed and we can't initialize
4858 * percpu_ref during early init. Disable refcnting.
4860 css
->flags
|= CSS_NO_REF
;
4863 /* allocation can't be done safely during early init */
4866 css
->id
= cgroup_idr_alloc(&ss
->css_idr
, css
, 1, 2, GFP_KERNEL
);
4867 BUG_ON(css
->id
< 0);
4870 /* Update the init_css_set to contain a subsys
4871 * pointer to this state - since the subsystem is
4872 * newly registered, all tasks and hence the
4873 * init_css_set is in the subsystem's root cgroup. */
4874 init_css_set
.subsys
[ss
->id
] = css
;
4876 need_forkexit_callback
|= ss
->fork
|| ss
->exit
;
4878 /* At system boot, before all subsystems have been
4879 * registered, no tasks have been forked, so we don't
4880 * need to invoke fork callbacks here. */
4881 BUG_ON(!list_empty(&init_task
.tasks
));
4883 BUG_ON(online_css(css
));
4885 mutex_unlock(&cgroup_mutex
);
4889 * cgroup_init_early - cgroup initialization at system boot
4891 * Initialize cgroups at system boot, and initialize any
4892 * subsystems that request early init.
4894 int __init
cgroup_init_early(void)
4896 static struct cgroup_sb_opts __initdata opts
;
4897 struct cgroup_subsys
*ss
;
4900 init_cgroup_root(&cgrp_dfl_root
, &opts
);
4901 cgrp_dfl_root
.cgrp
.self
.flags
|= CSS_NO_REF
;
4903 RCU_INIT_POINTER(init_task
.cgroups
, &init_css_set
);
4905 for_each_subsys(ss
, i
) {
4906 WARN(!ss
->css_alloc
|| !ss
->css_free
|| ss
->name
|| ss
->id
,
4907 "invalid cgroup_subsys %d:%s css_alloc=%p css_free=%p name:id=%d:%s\n",
4908 i
, cgroup_subsys_name
[i
], ss
->css_alloc
, ss
->css_free
,
4910 WARN(strlen(cgroup_subsys_name
[i
]) > MAX_CGROUP_TYPE_NAMELEN
,
4911 "cgroup_subsys_name %s too long\n", cgroup_subsys_name
[i
]);
4914 ss
->name
= cgroup_subsys_name
[i
];
4917 cgroup_init_subsys(ss
, true);
4923 * cgroup_init - cgroup initialization
4925 * Register cgroup filesystem and /proc file, and initialize
4926 * any subsystems that didn't request early init.
4928 int __init
cgroup_init(void)
4930 struct cgroup_subsys
*ss
;
4934 BUG_ON(cgroup_init_cftypes(NULL
, cgroup_dfl_base_files
));
4935 BUG_ON(cgroup_init_cftypes(NULL
, cgroup_legacy_base_files
));
4937 mutex_lock(&cgroup_mutex
);
4939 /* Add init_css_set to the hash table */
4940 key
= css_set_hash(init_css_set
.subsys
);
4941 hash_add(css_set_table
, &init_css_set
.hlist
, key
);
4943 BUG_ON(cgroup_setup_root(&cgrp_dfl_root
, 0));
4945 mutex_unlock(&cgroup_mutex
);
4947 for_each_subsys(ss
, ssid
) {
4948 if (ss
->early_init
) {
4949 struct cgroup_subsys_state
*css
=
4950 init_css_set
.subsys
[ss
->id
];
4952 css
->id
= cgroup_idr_alloc(&ss
->css_idr
, css
, 1, 2,
4954 BUG_ON(css
->id
< 0);
4956 cgroup_init_subsys(ss
, false);
4959 list_add_tail(&init_css_set
.e_cset_node
[ssid
],
4960 &cgrp_dfl_root
.cgrp
.e_csets
[ssid
]);
4963 * Setting dfl_root subsys_mask needs to consider the
4964 * disabled flag and cftype registration needs kmalloc,
4965 * both of which aren't available during early_init.
4970 cgrp_dfl_root
.subsys_mask
|= 1 << ss
->id
;
4972 if (cgroup_legacy_files_on_dfl
&& !ss
->dfl_cftypes
)
4973 ss
->dfl_cftypes
= ss
->legacy_cftypes
;
4975 if (!ss
->dfl_cftypes
)
4976 cgrp_dfl_root_inhibit_ss_mask
|= 1 << ss
->id
;
4978 if (ss
->dfl_cftypes
== ss
->legacy_cftypes
) {
4979 WARN_ON(cgroup_add_cftypes(ss
, ss
->dfl_cftypes
));
4981 WARN_ON(cgroup_add_dfl_cftypes(ss
, ss
->dfl_cftypes
));
4982 WARN_ON(cgroup_add_legacy_cftypes(ss
, ss
->legacy_cftypes
));
4986 cgroup_kobj
= kobject_create_and_add("cgroup", fs_kobj
);
4990 err
= register_filesystem(&cgroup_fs_type
);
4992 kobject_put(cgroup_kobj
);
4996 proc_create("cgroups", 0, NULL
, &proc_cgroupstats_operations
);
5000 static int __init
cgroup_wq_init(void)
5003 * There isn't much point in executing destruction path in
5004 * parallel. Good chunk is serialized with cgroup_mutex anyway.
5005 * Use 1 for @max_active.
5007 * We would prefer to do this in cgroup_init() above, but that
5008 * is called before init_workqueues(): so leave this until after.
5010 cgroup_destroy_wq
= alloc_workqueue("cgroup_destroy", 0, 1);
5011 BUG_ON(!cgroup_destroy_wq
);
5014 * Used to destroy pidlists and separate to serve as flush domain.
5015 * Cap @max_active to 1 too.
5017 cgroup_pidlist_destroy_wq
= alloc_workqueue("cgroup_pidlist_destroy",
5019 BUG_ON(!cgroup_pidlist_destroy_wq
);
5023 core_initcall(cgroup_wq_init
);
5026 * proc_cgroup_show()
5027 * - Print task's cgroup paths into seq_file, one line for each hierarchy
5028 * - Used for /proc/<pid>/cgroup.
5030 int proc_cgroup_show(struct seq_file
*m
, struct pid_namespace
*ns
,
5031 struct pid
*pid
, struct task_struct
*tsk
)
5035 struct cgroup_root
*root
;
5038 buf
= kmalloc(PATH_MAX
, GFP_KERNEL
);
5042 mutex_lock(&cgroup_mutex
);
5043 down_read(&css_set_rwsem
);
5045 for_each_root(root
) {
5046 struct cgroup_subsys
*ss
;
5047 struct cgroup
*cgrp
;
5048 int ssid
, count
= 0;
5050 if (root
== &cgrp_dfl_root
&& !cgrp_dfl_root_visible
)
5053 seq_printf(m
, "%d:", root
->hierarchy_id
);
5054 for_each_subsys(ss
, ssid
)
5055 if (root
->subsys_mask
& (1 << ssid
))
5056 seq_printf(m
, "%s%s", count
++ ? "," : "", ss
->name
);
5057 if (strlen(root
->name
))
5058 seq_printf(m
, "%sname=%s", count
? "," : "",
5061 cgrp
= task_cgroup_from_root(tsk
, root
);
5062 path
= cgroup_path(cgrp
, buf
, PATH_MAX
);
5064 retval
= -ENAMETOOLONG
;
5073 up_read(&css_set_rwsem
);
5074 mutex_unlock(&cgroup_mutex
);
5080 /* Display information about each subsystem and each hierarchy */
5081 static int proc_cgroupstats_show(struct seq_file
*m
, void *v
)
5083 struct cgroup_subsys
*ss
;
5086 seq_puts(m
, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
5088 * ideally we don't want subsystems moving around while we do this.
5089 * cgroup_mutex is also necessary to guarantee an atomic snapshot of
5090 * subsys/hierarchy state.
5092 mutex_lock(&cgroup_mutex
);
5094 for_each_subsys(ss
, i
)
5095 seq_printf(m
, "%s\t%d\t%d\t%d\n",
5096 ss
->name
, ss
->root
->hierarchy_id
,
5097 atomic_read(&ss
->root
->nr_cgrps
), !ss
->disabled
);
5099 mutex_unlock(&cgroup_mutex
);
5103 static int cgroupstats_open(struct inode
*inode
, struct file
*file
)
5105 return single_open(file
, proc_cgroupstats_show
, NULL
);
5108 static const struct file_operations proc_cgroupstats_operations
= {
5109 .open
= cgroupstats_open
,
5111 .llseek
= seq_lseek
,
5112 .release
= single_release
,
5116 * cgroup_fork - initialize cgroup related fields during copy_process()
5117 * @child: pointer to task_struct of forking parent process.
5119 * A task is associated with the init_css_set until cgroup_post_fork()
5120 * attaches it to the parent's css_set. Empty cg_list indicates that
5121 * @child isn't holding reference to its css_set.
5123 void cgroup_fork(struct task_struct
*child
)
5125 RCU_INIT_POINTER(child
->cgroups
, &init_css_set
);
5126 INIT_LIST_HEAD(&child
->cg_list
);
5130 * cgroup_post_fork - called on a new task after adding it to the task list
5131 * @child: the task in question
5133 * Adds the task to the list running through its css_set if necessary and
5134 * call the subsystem fork() callbacks. Has to be after the task is
5135 * visible on the task list in case we race with the first call to
5136 * cgroup_task_iter_start() - to guarantee that the new task ends up on its
5139 void cgroup_post_fork(struct task_struct
*child
)
5141 struct cgroup_subsys
*ss
;
5145 * This may race against cgroup_enable_task_cg_lists(). As that
5146 * function sets use_task_css_set_links before grabbing
5147 * tasklist_lock and we just went through tasklist_lock to add
5148 * @child, it's guaranteed that either we see the set
5149 * use_task_css_set_links or cgroup_enable_task_cg_lists() sees
5150 * @child during its iteration.
5152 * If we won the race, @child is associated with %current's
5153 * css_set. Grabbing css_set_rwsem guarantees both that the
5154 * association is stable, and, on completion of the parent's
5155 * migration, @child is visible in the source of migration or
5156 * already in the destination cgroup. This guarantee is necessary
5157 * when implementing operations which need to migrate all tasks of
5158 * a cgroup to another.
5160 * Note that if we lose to cgroup_enable_task_cg_lists(), @child
5161 * will remain in init_css_set. This is safe because all tasks are
5162 * in the init_css_set before cg_links is enabled and there's no
5163 * operation which transfers all tasks out of init_css_set.
5165 if (use_task_css_set_links
) {
5166 struct css_set
*cset
;
5168 down_write(&css_set_rwsem
);
5169 cset
= task_css_set(current
);
5170 if (list_empty(&child
->cg_list
)) {
5171 rcu_assign_pointer(child
->cgroups
, cset
);
5172 list_add(&child
->cg_list
, &cset
->tasks
);
5175 up_write(&css_set_rwsem
);
5179 * Call ss->fork(). This must happen after @child is linked on
5180 * css_set; otherwise, @child might change state between ->fork()
5181 * and addition to css_set.
5183 if (need_forkexit_callback
) {
5184 for_each_subsys(ss
, i
)
5191 * cgroup_exit - detach cgroup from exiting task
5192 * @tsk: pointer to task_struct of exiting process
5194 * Description: Detach cgroup from @tsk and release it.
5196 * Note that cgroups marked notify_on_release force every task in
5197 * them to take the global cgroup_mutex mutex when exiting.
5198 * This could impact scaling on very large systems. Be reluctant to
5199 * use notify_on_release cgroups where very high task exit scaling
5200 * is required on large systems.
5202 * We set the exiting tasks cgroup to the root cgroup (top_cgroup). We
5203 * call cgroup_exit() while the task is still competent to handle
5204 * notify_on_release(), then leave the task attached to the root cgroup in
5205 * each hierarchy for the remainder of its exit. No need to bother with
5206 * init_css_set refcnting. init_css_set never goes away and we can't race
5207 * with migration path - PF_EXITING is visible to migration path.
5209 void cgroup_exit(struct task_struct
*tsk
)
5211 struct cgroup_subsys
*ss
;
5212 struct css_set
*cset
;
5213 bool put_cset
= false;
5217 * Unlink from @tsk from its css_set. As migration path can't race
5218 * with us, we can check cg_list without grabbing css_set_rwsem.
5220 if (!list_empty(&tsk
->cg_list
)) {
5221 down_write(&css_set_rwsem
);
5222 list_del_init(&tsk
->cg_list
);
5223 up_write(&css_set_rwsem
);
5227 /* Reassign the task to the init_css_set. */
5228 cset
= task_css_set(tsk
);
5229 RCU_INIT_POINTER(tsk
->cgroups
, &init_css_set
);
5231 if (need_forkexit_callback
) {
5232 /* see cgroup_post_fork() for details */
5233 for_each_subsys(ss
, i
) {
5235 struct cgroup_subsys_state
*old_css
= cset
->subsys
[i
];
5236 struct cgroup_subsys_state
*css
= task_css(tsk
, i
);
5238 ss
->exit(css
, old_css
, tsk
);
5247 static void check_for_release(struct cgroup
*cgrp
)
5249 if (notify_on_release(cgrp
) && !cgroup_has_tasks(cgrp
) &&
5250 !css_has_online_children(&cgrp
->self
) && !cgroup_is_dead(cgrp
))
5251 schedule_work(&cgrp
->release_agent_work
);
5255 * Notify userspace when a cgroup is released, by running the
5256 * configured release agent with the name of the cgroup (path
5257 * relative to the root of cgroup file system) as the argument.
5259 * Most likely, this user command will try to rmdir this cgroup.
5261 * This races with the possibility that some other task will be
5262 * attached to this cgroup before it is removed, or that some other
5263 * user task will 'mkdir' a child cgroup of this cgroup. That's ok.
5264 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
5265 * unused, and this cgroup will be reprieved from its death sentence,
5266 * to continue to serve a useful existence. Next time it's released,
5267 * we will get notified again, if it still has 'notify_on_release' set.
5269 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
5270 * means only wait until the task is successfully execve()'d. The
5271 * separate release agent task is forked by call_usermodehelper(),
5272 * then control in this thread returns here, without waiting for the
5273 * release agent task. We don't bother to wait because the caller of
5274 * this routine has no use for the exit status of the release agent
5275 * task, so no sense holding our caller up for that.
5277 static void cgroup_release_agent(struct work_struct
*work
)
5279 struct cgroup
*cgrp
=
5280 container_of(work
, struct cgroup
, release_agent_work
);
5281 char *pathbuf
= NULL
, *agentbuf
= NULL
, *path
;
5282 char *argv
[3], *envp
[3];
5284 mutex_lock(&cgroup_mutex
);
5286 pathbuf
= kmalloc(PATH_MAX
, GFP_KERNEL
);
5287 agentbuf
= kstrdup(cgrp
->root
->release_agent_path
, GFP_KERNEL
);
5288 if (!pathbuf
|| !agentbuf
)
5291 path
= cgroup_path(cgrp
, pathbuf
, PATH_MAX
);
5299 /* minimal command environment */
5301 envp
[1] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
5304 mutex_unlock(&cgroup_mutex
);
5305 call_usermodehelper(argv
[0], argv
, envp
, UMH_WAIT_EXEC
);
5308 mutex_unlock(&cgroup_mutex
);
5314 static int __init
cgroup_disable(char *str
)
5316 struct cgroup_subsys
*ss
;
5320 while ((token
= strsep(&str
, ",")) != NULL
) {
5324 for_each_subsys(ss
, i
) {
5325 if (!strcmp(token
, ss
->name
)) {
5327 printk(KERN_INFO
"Disabling %s control group"
5328 " subsystem\n", ss
->name
);
5335 __setup("cgroup_disable=", cgroup_disable
);
5337 static int __init
cgroup_set_legacy_files_on_dfl(char *str
)
5339 printk("cgroup: using legacy files on the default hierarchy\n");
5340 cgroup_legacy_files_on_dfl
= true;
5343 __setup("cgroup__DEVEL__legacy_files_on_dfl", cgroup_set_legacy_files_on_dfl
);
5346 * css_tryget_online_from_dir - get corresponding css from a cgroup dentry
5347 * @dentry: directory dentry of interest
5348 * @ss: subsystem of interest
5350 * If @dentry is a directory for a cgroup which has @ss enabled on it, try
5351 * to get the corresponding css and return it. If such css doesn't exist
5352 * or can't be pinned, an ERR_PTR value is returned.
5354 struct cgroup_subsys_state
*css_tryget_online_from_dir(struct dentry
*dentry
,
5355 struct cgroup_subsys
*ss
)
5357 struct kernfs_node
*kn
= kernfs_node_from_dentry(dentry
);
5358 struct cgroup_subsys_state
*css
= NULL
;
5359 struct cgroup
*cgrp
;
5361 /* is @dentry a cgroup dir? */
5362 if (dentry
->d_sb
->s_type
!= &cgroup_fs_type
|| !kn
||
5363 kernfs_type(kn
) != KERNFS_DIR
)
5364 return ERR_PTR(-EBADF
);
5369 * This path doesn't originate from kernfs and @kn could already
5370 * have been or be removed at any point. @kn->priv is RCU
5371 * protected for this access. See css_release_work_fn() for details.
5373 cgrp
= rcu_dereference(kn
->priv
);
5375 css
= cgroup_css(cgrp
, ss
);
5377 if (!css
|| !css_tryget_online(css
))
5378 css
= ERR_PTR(-ENOENT
);
5385 * css_from_id - lookup css by id
5386 * @id: the cgroup id
5387 * @ss: cgroup subsys to be looked into
5389 * Returns the css if there's valid one with @id, otherwise returns NULL.
5390 * Should be called under rcu_read_lock().
5392 struct cgroup_subsys_state
*css_from_id(int id
, struct cgroup_subsys
*ss
)
5394 WARN_ON_ONCE(!rcu_read_lock_held());
5395 return idr_find(&ss
->css_idr
, id
);
5398 #ifdef CONFIG_CGROUP_DEBUG
5399 static struct cgroup_subsys_state
*
5400 debug_css_alloc(struct cgroup_subsys_state
*parent_css
)
5402 struct cgroup_subsys_state
*css
= kzalloc(sizeof(*css
), GFP_KERNEL
);
5405 return ERR_PTR(-ENOMEM
);
5410 static void debug_css_free(struct cgroup_subsys_state
*css
)
5415 static u64
debug_taskcount_read(struct cgroup_subsys_state
*css
,
5418 return cgroup_task_count(css
->cgroup
);
5421 static u64
current_css_set_read(struct cgroup_subsys_state
*css
,
5424 return (u64
)(unsigned long)current
->cgroups
;
5427 static u64
current_css_set_refcount_read(struct cgroup_subsys_state
*css
,
5433 count
= atomic_read(&task_css_set(current
)->refcount
);
5438 static int current_css_set_cg_links_read(struct seq_file
*seq
, void *v
)
5440 struct cgrp_cset_link
*link
;
5441 struct css_set
*cset
;
5444 name_buf
= kmalloc(NAME_MAX
+ 1, GFP_KERNEL
);
5448 down_read(&css_set_rwsem
);
5450 cset
= rcu_dereference(current
->cgroups
);
5451 list_for_each_entry(link
, &cset
->cgrp_links
, cgrp_link
) {
5452 struct cgroup
*c
= link
->cgrp
;
5454 cgroup_name(c
, name_buf
, NAME_MAX
+ 1);
5455 seq_printf(seq
, "Root %d group %s\n",
5456 c
->root
->hierarchy_id
, name_buf
);
5459 up_read(&css_set_rwsem
);
5464 #define MAX_TASKS_SHOWN_PER_CSS 25
5465 static int cgroup_css_links_read(struct seq_file
*seq
, void *v
)
5467 struct cgroup_subsys_state
*css
= seq_css(seq
);
5468 struct cgrp_cset_link
*link
;
5470 down_read(&css_set_rwsem
);
5471 list_for_each_entry(link
, &css
->cgroup
->cset_links
, cset_link
) {
5472 struct css_set
*cset
= link
->cset
;
5473 struct task_struct
*task
;
5476 seq_printf(seq
, "css_set %p\n", cset
);
5478 list_for_each_entry(task
, &cset
->tasks
, cg_list
) {
5479 if (count
++ > MAX_TASKS_SHOWN_PER_CSS
)
5481 seq_printf(seq
, " task %d\n", task_pid_vnr(task
));
5484 list_for_each_entry(task
, &cset
->mg_tasks
, cg_list
) {
5485 if (count
++ > MAX_TASKS_SHOWN_PER_CSS
)
5487 seq_printf(seq
, " task %d\n", task_pid_vnr(task
));
5491 seq_puts(seq
, " ...\n");
5493 up_read(&css_set_rwsem
);
5497 static u64
releasable_read(struct cgroup_subsys_state
*css
, struct cftype
*cft
)
5499 return (!cgroup_has_tasks(css
->cgroup
) &&
5500 !css_has_online_children(&css
->cgroup
->self
));
5503 static struct cftype debug_files
[] = {
5505 .name
= "taskcount",
5506 .read_u64
= debug_taskcount_read
,
5510 .name
= "current_css_set",
5511 .read_u64
= current_css_set_read
,
5515 .name
= "current_css_set_refcount",
5516 .read_u64
= current_css_set_refcount_read
,
5520 .name
= "current_css_set_cg_links",
5521 .seq_show
= current_css_set_cg_links_read
,
5525 .name
= "cgroup_css_links",
5526 .seq_show
= cgroup_css_links_read
,
5530 .name
= "releasable",
5531 .read_u64
= releasable_read
,
5537 struct cgroup_subsys debug_cgrp_subsys
= {
5538 .css_alloc
= debug_css_alloc
,
5539 .css_free
= debug_css_free
,
5540 .legacy_cftypes
= debug_files
,
5542 #endif /* CONFIG_CGROUP_DEBUG */