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_WARN(!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
;
145 EXPORT_SYMBOL_GPL(cgrp_dfl_root
);
148 * The default hierarchy always exists but is hidden until mounted for the
149 * first time. This is for backward compatibility.
151 static bool cgrp_dfl_root_visible
;
154 * Set by the boot param of the same name and makes subsystems with NULL
155 * ->dfl_files to use ->legacy_files on the default hierarchy.
157 static bool cgroup_legacy_files_on_dfl
;
159 /* some controllers are not supported in the default hierarchy */
160 static unsigned long cgrp_dfl_root_inhibit_ss_mask
;
162 /* The list of hierarchy roots */
164 static LIST_HEAD(cgroup_roots
);
165 static int cgroup_root_count
;
167 /* hierarchy ID allocation and mapping, protected by cgroup_mutex */
168 static DEFINE_IDR(cgroup_hierarchy_idr
);
171 * Assign a monotonically increasing serial number to csses. It guarantees
172 * cgroups with bigger numbers are newer than those with smaller numbers.
173 * Also, as csses are always appended to the parent's ->children list, it
174 * guarantees that sibling csses are always sorted in the ascending serial
175 * number order on the list. Protected by cgroup_mutex.
177 static u64 css_serial_nr_next
= 1;
180 * These bitmask flags indicate whether tasks in the fork and exit paths have
181 * fork/exit handlers to call. This avoids us having to do extra work in the
182 * fork/exit path to check which subsystems have fork/exit callbacks.
184 static unsigned long have_fork_callback __read_mostly
;
185 static unsigned long have_exit_callback __read_mostly
;
187 /* Ditto for the can_fork callback. */
188 static unsigned long have_canfork_callback __read_mostly
;
190 static struct cftype cgroup_dfl_base_files
[];
191 static struct cftype cgroup_legacy_base_files
[];
193 static int rebind_subsystems(struct cgroup_root
*dst_root
,
194 unsigned long ss_mask
);
195 static int cgroup_destroy_locked(struct cgroup
*cgrp
);
196 static int create_css(struct cgroup
*cgrp
, struct cgroup_subsys
*ss
,
198 static void css_release(struct percpu_ref
*ref
);
199 static void kill_css(struct cgroup_subsys_state
*css
);
200 static int cgroup_addrm_files(struct cgroup
*cgrp
, struct cftype cfts
[],
203 /* IDR wrappers which synchronize using cgroup_idr_lock */
204 static int cgroup_idr_alloc(struct idr
*idr
, void *ptr
, int start
, int end
,
209 idr_preload(gfp_mask
);
210 spin_lock_bh(&cgroup_idr_lock
);
211 ret
= idr_alloc(idr
, ptr
, start
, end
, gfp_mask
& ~__GFP_WAIT
);
212 spin_unlock_bh(&cgroup_idr_lock
);
217 static void *cgroup_idr_replace(struct idr
*idr
, void *ptr
, int id
)
221 spin_lock_bh(&cgroup_idr_lock
);
222 ret
= idr_replace(idr
, ptr
, id
);
223 spin_unlock_bh(&cgroup_idr_lock
);
227 static void cgroup_idr_remove(struct idr
*idr
, int id
)
229 spin_lock_bh(&cgroup_idr_lock
);
231 spin_unlock_bh(&cgroup_idr_lock
);
234 static struct cgroup
*cgroup_parent(struct cgroup
*cgrp
)
236 struct cgroup_subsys_state
*parent_css
= cgrp
->self
.parent
;
239 return container_of(parent_css
, struct cgroup
, self
);
244 * cgroup_css - obtain a cgroup's css for the specified subsystem
245 * @cgrp: the cgroup of interest
246 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
248 * Return @cgrp's css (cgroup_subsys_state) associated with @ss. This
249 * function must be called either under cgroup_mutex or rcu_read_lock() and
250 * the caller is responsible for pinning the returned css if it wants to
251 * keep accessing it outside the said locks. This function may return
252 * %NULL if @cgrp doesn't have @subsys_id enabled.
254 static struct cgroup_subsys_state
*cgroup_css(struct cgroup
*cgrp
,
255 struct cgroup_subsys
*ss
)
258 return rcu_dereference_check(cgrp
->subsys
[ss
->id
],
259 lockdep_is_held(&cgroup_mutex
));
265 * cgroup_e_css - obtain a cgroup's effective css for the specified subsystem
266 * @cgrp: the cgroup of interest
267 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
269 * Similar to cgroup_css() but returns the effective css, which is defined
270 * as the matching css of the nearest ancestor including self which has @ss
271 * enabled. If @ss is associated with the hierarchy @cgrp is on, this
272 * function is guaranteed to return non-NULL css.
274 static struct cgroup_subsys_state
*cgroup_e_css(struct cgroup
*cgrp
,
275 struct cgroup_subsys
*ss
)
277 lockdep_assert_held(&cgroup_mutex
);
282 if (!(cgrp
->root
->subsys_mask
& (1 << ss
->id
)))
286 * This function is used while updating css associations and thus
287 * can't test the csses directly. Use ->child_subsys_mask.
289 while (cgroup_parent(cgrp
) &&
290 !(cgroup_parent(cgrp
)->child_subsys_mask
& (1 << ss
->id
)))
291 cgrp
= cgroup_parent(cgrp
);
293 return cgroup_css(cgrp
, ss
);
297 * cgroup_get_e_css - get a cgroup's effective css for the specified subsystem
298 * @cgrp: the cgroup of interest
299 * @ss: the subsystem of interest
301 * Find and get the effective css of @cgrp for @ss. The effective css is
302 * defined as the matching css of the nearest ancestor including self which
303 * has @ss enabled. If @ss is not mounted on the hierarchy @cgrp is on,
304 * the root css is returned, so this function always returns a valid css.
305 * The returned css must be put using css_put().
307 struct cgroup_subsys_state
*cgroup_get_e_css(struct cgroup
*cgrp
,
308 struct cgroup_subsys
*ss
)
310 struct cgroup_subsys_state
*css
;
315 css
= cgroup_css(cgrp
, ss
);
317 if (css
&& css_tryget_online(css
))
319 cgrp
= cgroup_parent(cgrp
);
322 css
= init_css_set
.subsys
[ss
->id
];
329 /* convenient tests for these bits */
330 static inline bool cgroup_is_dead(const struct cgroup
*cgrp
)
332 return !(cgrp
->self
.flags
& CSS_ONLINE
);
335 struct cgroup_subsys_state
*of_css(struct kernfs_open_file
*of
)
337 struct cgroup
*cgrp
= of
->kn
->parent
->priv
;
338 struct cftype
*cft
= of_cft(of
);
341 * This is open and unprotected implementation of cgroup_css().
342 * seq_css() is only called from a kernfs file operation which has
343 * an active reference on the file. Because all the subsystem
344 * files are drained before a css is disassociated with a cgroup,
345 * the matching css from the cgroup's subsys table is guaranteed to
346 * be and stay valid until the enclosing operation is complete.
349 return rcu_dereference_raw(cgrp
->subsys
[cft
->ss
->id
]);
353 EXPORT_SYMBOL_GPL(of_css
);
356 * cgroup_is_descendant - test ancestry
357 * @cgrp: the cgroup to be tested
358 * @ancestor: possible ancestor of @cgrp
360 * Test whether @cgrp is a descendant of @ancestor. It also returns %true
361 * if @cgrp == @ancestor. This function is safe to call as long as @cgrp
362 * and @ancestor are accessible.
364 bool cgroup_is_descendant(struct cgroup
*cgrp
, struct cgroup
*ancestor
)
367 if (cgrp
== ancestor
)
369 cgrp
= cgroup_parent(cgrp
);
374 static int notify_on_release(const struct cgroup
*cgrp
)
376 return test_bit(CGRP_NOTIFY_ON_RELEASE
, &cgrp
->flags
);
380 * for_each_css - iterate all css's of a cgroup
381 * @css: the iteration cursor
382 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
383 * @cgrp: the target cgroup to iterate css's of
385 * Should be called under cgroup_[tree_]mutex.
387 #define for_each_css(css, ssid, cgrp) \
388 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
389 if (!((css) = rcu_dereference_check( \
390 (cgrp)->subsys[(ssid)], \
391 lockdep_is_held(&cgroup_mutex)))) { } \
395 * for_each_e_css - iterate all effective css's of a cgroup
396 * @css: the iteration cursor
397 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
398 * @cgrp: the target cgroup to iterate css's of
400 * Should be called under cgroup_[tree_]mutex.
402 #define for_each_e_css(css, ssid, cgrp) \
403 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
404 if (!((css) = cgroup_e_css(cgrp, cgroup_subsys[(ssid)]))) \
409 * for_each_subsys - iterate all enabled cgroup subsystems
410 * @ss: the iteration cursor
411 * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
413 #define for_each_subsys(ss, ssid) \
414 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT && \
415 (((ss) = cgroup_subsys[ssid]) || true); (ssid)++)
418 * for_each_subsys_which - filter for_each_subsys with a bitmask
419 * @ss: the iteration cursor
420 * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
421 * @ss_maskp: a pointer to the bitmask
423 * The block will only run for cases where the ssid-th bit (1 << ssid) of
426 #define for_each_subsys_which(ss, ssid, ss_maskp) \
427 if (!CGROUP_SUBSYS_COUNT) /* to avoid spurious gcc warning */ \
430 for_each_set_bit(ssid, ss_maskp, CGROUP_SUBSYS_COUNT) \
431 if (((ss) = cgroup_subsys[ssid]) && false) \
435 /* iterate across the hierarchies */
436 #define for_each_root(root) \
437 list_for_each_entry((root), &cgroup_roots, root_list)
439 /* iterate over child cgrps, lock should be held throughout iteration */
440 #define cgroup_for_each_live_child(child, cgrp) \
441 list_for_each_entry((child), &(cgrp)->self.children, self.sibling) \
442 if (({ lockdep_assert_held(&cgroup_mutex); \
443 cgroup_is_dead(child); })) \
447 static void cgroup_release_agent(struct work_struct
*work
);
448 static void check_for_release(struct cgroup
*cgrp
);
451 * A cgroup can be associated with multiple css_sets as different tasks may
452 * belong to different cgroups on different hierarchies. In the other
453 * direction, a css_set is naturally associated with multiple cgroups.
454 * This M:N relationship is represented by the following link structure
455 * which exists for each association and allows traversing the associations
458 struct cgrp_cset_link
{
459 /* the cgroup and css_set this link associates */
461 struct css_set
*cset
;
463 /* list of cgrp_cset_links anchored at cgrp->cset_links */
464 struct list_head cset_link
;
466 /* list of cgrp_cset_links anchored at css_set->cgrp_links */
467 struct list_head cgrp_link
;
471 * The default css_set - used by init and its children prior to any
472 * hierarchies being mounted. It contains a pointer to the root state
473 * for each subsystem. Also used to anchor the list of css_sets. Not
474 * reference-counted, to improve performance when child cgroups
475 * haven't been created.
477 struct css_set init_css_set
= {
478 .refcount
= ATOMIC_INIT(1),
479 .cgrp_links
= LIST_HEAD_INIT(init_css_set
.cgrp_links
),
480 .tasks
= LIST_HEAD_INIT(init_css_set
.tasks
),
481 .mg_tasks
= LIST_HEAD_INIT(init_css_set
.mg_tasks
),
482 .mg_preload_node
= LIST_HEAD_INIT(init_css_set
.mg_preload_node
),
483 .mg_node
= LIST_HEAD_INIT(init_css_set
.mg_node
),
486 static int css_set_count
= 1; /* 1 for init_css_set */
489 * cgroup_update_populated - updated populated count of a cgroup
490 * @cgrp: the target cgroup
491 * @populated: inc or dec populated count
493 * @cgrp is either getting the first task (css_set) or losing the last.
494 * Update @cgrp->populated_cnt accordingly. The count is propagated
495 * towards root so that a given cgroup's populated_cnt is zero iff the
496 * cgroup and all its descendants are empty.
498 * @cgrp's interface file "cgroup.populated" is zero if
499 * @cgrp->populated_cnt is zero and 1 otherwise. When @cgrp->populated_cnt
500 * changes from or to zero, userland is notified that the content of the
501 * interface file has changed. This can be used to detect when @cgrp and
502 * its descendants become populated or empty.
504 static void cgroup_update_populated(struct cgroup
*cgrp
, bool populated
)
506 lockdep_assert_held(&css_set_rwsem
);
512 trigger
= !cgrp
->populated_cnt
++;
514 trigger
= !--cgrp
->populated_cnt
;
519 if (cgrp
->populated_kn
)
520 kernfs_notify(cgrp
->populated_kn
);
521 cgrp
= cgroup_parent(cgrp
);
526 * hash table for cgroup groups. This improves the performance to find
527 * an existing css_set. This hash doesn't (currently) take into
528 * account cgroups in empty hierarchies.
530 #define CSS_SET_HASH_BITS 7
531 static DEFINE_HASHTABLE(css_set_table
, CSS_SET_HASH_BITS
);
533 static unsigned long css_set_hash(struct cgroup_subsys_state
*css
[])
535 unsigned long key
= 0UL;
536 struct cgroup_subsys
*ss
;
539 for_each_subsys(ss
, i
)
540 key
+= (unsigned long)css
[i
];
541 key
= (key
>> 16) ^ key
;
546 static void put_css_set_locked(struct css_set
*cset
)
548 struct cgrp_cset_link
*link
, *tmp_link
;
549 struct cgroup_subsys
*ss
;
552 lockdep_assert_held(&css_set_rwsem
);
554 if (!atomic_dec_and_test(&cset
->refcount
))
557 /* This css_set is dead. unlink it and release cgroup refcounts */
558 for_each_subsys(ss
, ssid
)
559 list_del(&cset
->e_cset_node
[ssid
]);
560 hash_del(&cset
->hlist
);
563 list_for_each_entry_safe(link
, tmp_link
, &cset
->cgrp_links
, cgrp_link
) {
564 struct cgroup
*cgrp
= link
->cgrp
;
566 list_del(&link
->cset_link
);
567 list_del(&link
->cgrp_link
);
569 /* @cgrp can't go away while we're holding css_set_rwsem */
570 if (list_empty(&cgrp
->cset_links
)) {
571 cgroup_update_populated(cgrp
, false);
572 check_for_release(cgrp
);
578 kfree_rcu(cset
, rcu_head
);
581 static void put_css_set(struct css_set
*cset
)
584 * Ensure that the refcount doesn't hit zero while any readers
585 * can see it. Similar to atomic_dec_and_lock(), but for an
588 if (atomic_add_unless(&cset
->refcount
, -1, 1))
591 down_write(&css_set_rwsem
);
592 put_css_set_locked(cset
);
593 up_write(&css_set_rwsem
);
597 * refcounted get/put for css_set objects
599 static inline void get_css_set(struct css_set
*cset
)
601 atomic_inc(&cset
->refcount
);
605 * compare_css_sets - helper function for find_existing_css_set().
606 * @cset: candidate css_set being tested
607 * @old_cset: existing css_set for a task
608 * @new_cgrp: cgroup that's being entered by the task
609 * @template: desired set of css pointers in css_set (pre-calculated)
611 * Returns true if "cset" matches "old_cset" except for the hierarchy
612 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
614 static bool compare_css_sets(struct css_set
*cset
,
615 struct css_set
*old_cset
,
616 struct cgroup
*new_cgrp
,
617 struct cgroup_subsys_state
*template[])
619 struct list_head
*l1
, *l2
;
622 * On the default hierarchy, there can be csets which are
623 * associated with the same set of cgroups but different csses.
624 * Let's first ensure that csses match.
626 if (memcmp(template, cset
->subsys
, sizeof(cset
->subsys
)))
630 * Compare cgroup pointers in order to distinguish between
631 * different cgroups in hierarchies. As different cgroups may
632 * share the same effective css, this comparison is always
635 l1
= &cset
->cgrp_links
;
636 l2
= &old_cset
->cgrp_links
;
638 struct cgrp_cset_link
*link1
, *link2
;
639 struct cgroup
*cgrp1
, *cgrp2
;
643 /* See if we reached the end - both lists are equal length. */
644 if (l1
== &cset
->cgrp_links
) {
645 BUG_ON(l2
!= &old_cset
->cgrp_links
);
648 BUG_ON(l2
== &old_cset
->cgrp_links
);
650 /* Locate the cgroups associated with these links. */
651 link1
= list_entry(l1
, struct cgrp_cset_link
, cgrp_link
);
652 link2
= list_entry(l2
, struct cgrp_cset_link
, cgrp_link
);
655 /* Hierarchies should be linked in the same order. */
656 BUG_ON(cgrp1
->root
!= cgrp2
->root
);
659 * If this hierarchy is the hierarchy of the cgroup
660 * that's changing, then we need to check that this
661 * css_set points to the new cgroup; if it's any other
662 * hierarchy, then this css_set should point to the
663 * same cgroup as the old css_set.
665 if (cgrp1
->root
== new_cgrp
->root
) {
666 if (cgrp1
!= new_cgrp
)
677 * find_existing_css_set - init css array and find the matching css_set
678 * @old_cset: the css_set that we're using before the cgroup transition
679 * @cgrp: the cgroup that we're moving into
680 * @template: out param for the new set of csses, should be clear on entry
682 static struct css_set
*find_existing_css_set(struct css_set
*old_cset
,
684 struct cgroup_subsys_state
*template[])
686 struct cgroup_root
*root
= cgrp
->root
;
687 struct cgroup_subsys
*ss
;
688 struct css_set
*cset
;
693 * Build the set of subsystem state objects that we want to see in the
694 * new css_set. while subsystems can change globally, the entries here
695 * won't change, so no need for locking.
697 for_each_subsys(ss
, i
) {
698 if (root
->subsys_mask
& (1UL << i
)) {
700 * @ss is in this hierarchy, so we want the
701 * effective css from @cgrp.
703 template[i
] = cgroup_e_css(cgrp
, ss
);
706 * @ss is not in this hierarchy, so we don't want
709 template[i
] = old_cset
->subsys
[i
];
713 key
= css_set_hash(template);
714 hash_for_each_possible(css_set_table
, cset
, hlist
, key
) {
715 if (!compare_css_sets(cset
, old_cset
, cgrp
, template))
718 /* This css_set matches what we need */
722 /* No existing cgroup group matched */
726 static void free_cgrp_cset_links(struct list_head
*links_to_free
)
728 struct cgrp_cset_link
*link
, *tmp_link
;
730 list_for_each_entry_safe(link
, tmp_link
, links_to_free
, cset_link
) {
731 list_del(&link
->cset_link
);
737 * allocate_cgrp_cset_links - allocate cgrp_cset_links
738 * @count: the number of links to allocate
739 * @tmp_links: list_head the allocated links are put on
741 * Allocate @count cgrp_cset_link structures and chain them on @tmp_links
742 * through ->cset_link. Returns 0 on success or -errno.
744 static int allocate_cgrp_cset_links(int count
, struct list_head
*tmp_links
)
746 struct cgrp_cset_link
*link
;
749 INIT_LIST_HEAD(tmp_links
);
751 for (i
= 0; i
< count
; i
++) {
752 link
= kzalloc(sizeof(*link
), GFP_KERNEL
);
754 free_cgrp_cset_links(tmp_links
);
757 list_add(&link
->cset_link
, tmp_links
);
763 * link_css_set - a helper function to link a css_set to a cgroup
764 * @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()
765 * @cset: the css_set to be linked
766 * @cgrp: the destination cgroup
768 static void link_css_set(struct list_head
*tmp_links
, struct css_set
*cset
,
771 struct cgrp_cset_link
*link
;
773 BUG_ON(list_empty(tmp_links
));
775 if (cgroup_on_dfl(cgrp
))
776 cset
->dfl_cgrp
= cgrp
;
778 link
= list_first_entry(tmp_links
, struct cgrp_cset_link
, cset_link
);
782 if (list_empty(&cgrp
->cset_links
))
783 cgroup_update_populated(cgrp
, true);
784 list_move(&link
->cset_link
, &cgrp
->cset_links
);
787 * Always add links to the tail of the list so that the list
788 * is sorted by order of hierarchy creation
790 list_add_tail(&link
->cgrp_link
, &cset
->cgrp_links
);
794 * find_css_set - return a new css_set with one cgroup updated
795 * @old_cset: the baseline css_set
796 * @cgrp: the cgroup to be updated
798 * Return a new css_set that's equivalent to @old_cset, but with @cgrp
799 * substituted into the appropriate hierarchy.
801 static struct css_set
*find_css_set(struct css_set
*old_cset
,
804 struct cgroup_subsys_state
*template[CGROUP_SUBSYS_COUNT
] = { };
805 struct css_set
*cset
;
806 struct list_head tmp_links
;
807 struct cgrp_cset_link
*link
;
808 struct cgroup_subsys
*ss
;
812 lockdep_assert_held(&cgroup_mutex
);
814 /* First see if we already have a cgroup group that matches
816 down_read(&css_set_rwsem
);
817 cset
= find_existing_css_set(old_cset
, cgrp
, template);
820 up_read(&css_set_rwsem
);
825 cset
= kzalloc(sizeof(*cset
), GFP_KERNEL
);
829 /* Allocate all the cgrp_cset_link objects that we'll need */
830 if (allocate_cgrp_cset_links(cgroup_root_count
, &tmp_links
) < 0) {
835 atomic_set(&cset
->refcount
, 1);
836 INIT_LIST_HEAD(&cset
->cgrp_links
);
837 INIT_LIST_HEAD(&cset
->tasks
);
838 INIT_LIST_HEAD(&cset
->mg_tasks
);
839 INIT_LIST_HEAD(&cset
->mg_preload_node
);
840 INIT_LIST_HEAD(&cset
->mg_node
);
841 INIT_HLIST_NODE(&cset
->hlist
);
843 /* Copy the set of subsystem state objects generated in
844 * find_existing_css_set() */
845 memcpy(cset
->subsys
, template, sizeof(cset
->subsys
));
847 down_write(&css_set_rwsem
);
848 /* Add reference counts and links from the new css_set. */
849 list_for_each_entry(link
, &old_cset
->cgrp_links
, cgrp_link
) {
850 struct cgroup
*c
= link
->cgrp
;
852 if (c
->root
== cgrp
->root
)
854 link_css_set(&tmp_links
, cset
, c
);
857 BUG_ON(!list_empty(&tmp_links
));
861 /* Add @cset to the hash table */
862 key
= css_set_hash(cset
->subsys
);
863 hash_add(css_set_table
, &cset
->hlist
, key
);
865 for_each_subsys(ss
, ssid
)
866 list_add_tail(&cset
->e_cset_node
[ssid
],
867 &cset
->subsys
[ssid
]->cgroup
->e_csets
[ssid
]);
869 up_write(&css_set_rwsem
);
874 void cgroup_threadgroup_change_begin(struct task_struct
*tsk
)
876 down_read(&tsk
->signal
->group_rwsem
);
879 void cgroup_threadgroup_change_end(struct task_struct
*tsk
)
881 up_read(&tsk
->signal
->group_rwsem
);
885 * threadgroup_lock - lock threadgroup
886 * @tsk: member task of the threadgroup to lock
888 * Lock the threadgroup @tsk belongs to. No new task is allowed to enter
889 * and member tasks aren't allowed to exit (as indicated by PF_EXITING) or
890 * change ->group_leader/pid. This is useful for cases where the threadgroup
891 * needs to stay stable across blockable operations.
893 * fork and exit explicitly call threadgroup_change_{begin|end}() for
894 * synchronization. While held, no new task will be added to threadgroup
895 * and no existing live task will have its PF_EXITING set.
897 * de_thread() does threadgroup_change_{begin|end}() when a non-leader
898 * sub-thread becomes a new leader.
900 static void threadgroup_lock(struct task_struct
*tsk
)
902 down_write(&tsk
->signal
->group_rwsem
);
906 * threadgroup_unlock - unlock threadgroup
907 * @tsk: member task of the threadgroup to unlock
909 * Reverse threadgroup_lock().
911 static inline void threadgroup_unlock(struct task_struct
*tsk
)
913 up_write(&tsk
->signal
->group_rwsem
);
916 static struct cgroup_root
*cgroup_root_from_kf(struct kernfs_root
*kf_root
)
918 struct cgroup
*root_cgrp
= kf_root
->kn
->priv
;
920 return root_cgrp
->root
;
923 static int cgroup_init_root_id(struct cgroup_root
*root
)
927 lockdep_assert_held(&cgroup_mutex
);
929 id
= idr_alloc_cyclic(&cgroup_hierarchy_idr
, root
, 0, 0, GFP_KERNEL
);
933 root
->hierarchy_id
= id
;
937 static void cgroup_exit_root_id(struct cgroup_root
*root
)
939 lockdep_assert_held(&cgroup_mutex
);
941 if (root
->hierarchy_id
) {
942 idr_remove(&cgroup_hierarchy_idr
, root
->hierarchy_id
);
943 root
->hierarchy_id
= 0;
947 static void cgroup_free_root(struct cgroup_root
*root
)
950 /* hierarchy ID should already have been released */
951 WARN_ON_ONCE(root
->hierarchy_id
);
953 idr_destroy(&root
->cgroup_idr
);
958 static void cgroup_destroy_root(struct cgroup_root
*root
)
960 struct cgroup
*cgrp
= &root
->cgrp
;
961 struct cgrp_cset_link
*link
, *tmp_link
;
963 mutex_lock(&cgroup_mutex
);
965 BUG_ON(atomic_read(&root
->nr_cgrps
));
966 BUG_ON(!list_empty(&cgrp
->self
.children
));
968 /* Rebind all subsystems back to the default hierarchy */
969 rebind_subsystems(&cgrp_dfl_root
, root
->subsys_mask
);
972 * Release all the links from cset_links to this hierarchy's
975 down_write(&css_set_rwsem
);
977 list_for_each_entry_safe(link
, tmp_link
, &cgrp
->cset_links
, cset_link
) {
978 list_del(&link
->cset_link
);
979 list_del(&link
->cgrp_link
);
982 up_write(&css_set_rwsem
);
984 if (!list_empty(&root
->root_list
)) {
985 list_del(&root
->root_list
);
989 cgroup_exit_root_id(root
);
991 mutex_unlock(&cgroup_mutex
);
993 kernfs_destroy_root(root
->kf_root
);
994 cgroup_free_root(root
);
997 /* look up cgroup associated with given css_set on the specified hierarchy */
998 static struct cgroup
*cset_cgroup_from_root(struct css_set
*cset
,
999 struct cgroup_root
*root
)
1001 struct cgroup
*res
= NULL
;
1003 lockdep_assert_held(&cgroup_mutex
);
1004 lockdep_assert_held(&css_set_rwsem
);
1006 if (cset
== &init_css_set
) {
1009 struct cgrp_cset_link
*link
;
1011 list_for_each_entry(link
, &cset
->cgrp_links
, cgrp_link
) {
1012 struct cgroup
*c
= link
->cgrp
;
1014 if (c
->root
== root
) {
1026 * Return the cgroup for "task" from the given hierarchy. Must be
1027 * called with cgroup_mutex and css_set_rwsem held.
1029 static struct cgroup
*task_cgroup_from_root(struct task_struct
*task
,
1030 struct cgroup_root
*root
)
1033 * No need to lock the task - since we hold cgroup_mutex the
1034 * task can't change groups, so the only thing that can happen
1035 * is that it exits and its css is set back to init_css_set.
1037 return cset_cgroup_from_root(task_css_set(task
), root
);
1041 * A task must hold cgroup_mutex to modify cgroups.
1043 * Any task can increment and decrement the count field without lock.
1044 * So in general, code holding cgroup_mutex can't rely on the count
1045 * field not changing. However, if the count goes to zero, then only
1046 * cgroup_attach_task() can increment it again. Because a count of zero
1047 * means that no tasks are currently attached, therefore there is no
1048 * way a task attached to that cgroup can fork (the other way to
1049 * increment the count). So code holding cgroup_mutex can safely
1050 * assume that if the count is zero, it will stay zero. Similarly, if
1051 * a task holds cgroup_mutex on a cgroup with zero count, it
1052 * knows that the cgroup won't be removed, as cgroup_rmdir()
1055 * A cgroup can only be deleted if both its 'count' of using tasks
1056 * is zero, and its list of 'children' cgroups is empty. Since all
1057 * tasks in the system use _some_ cgroup, and since there is always at
1058 * least one task in the system (init, pid == 1), therefore, root cgroup
1059 * always has either children cgroups and/or using tasks. So we don't
1060 * need a special hack to ensure that root cgroup cannot be deleted.
1062 * P.S. One more locking exception. RCU is used to guard the
1063 * update of a tasks cgroup pointer by cgroup_attach_task()
1066 static int cgroup_populate_dir(struct cgroup
*cgrp
, unsigned long subsys_mask
);
1067 static struct kernfs_syscall_ops cgroup_kf_syscall_ops
;
1068 static const struct file_operations proc_cgroupstats_operations
;
1070 static char *cgroup_file_name(struct cgroup
*cgrp
, const struct cftype
*cft
,
1073 struct cgroup_subsys
*ss
= cft
->ss
;
1075 if (cft
->ss
&& !(cft
->flags
& CFTYPE_NO_PREFIX
) &&
1076 !(cgrp
->root
->flags
& CGRP_ROOT_NOPREFIX
))
1077 snprintf(buf
, CGROUP_FILE_NAME_MAX
, "%s.%s",
1078 cgroup_on_dfl(cgrp
) ? ss
->name
: ss
->legacy_name
,
1081 strncpy(buf
, cft
->name
, CGROUP_FILE_NAME_MAX
);
1086 * cgroup_file_mode - deduce file mode of a control file
1087 * @cft: the control file in question
1089 * returns cft->mode if ->mode is not 0
1090 * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
1091 * returns S_IRUGO if it has only a read handler
1092 * returns S_IWUSR if it has only a write hander
1094 static umode_t
cgroup_file_mode(const struct cftype
*cft
)
1101 if (cft
->read_u64
|| cft
->read_s64
|| cft
->seq_show
)
1104 if (cft
->write_u64
|| cft
->write_s64
|| cft
->write
)
1110 static void cgroup_get(struct cgroup
*cgrp
)
1112 WARN_ON_ONCE(cgroup_is_dead(cgrp
));
1113 css_get(&cgrp
->self
);
1116 static bool cgroup_tryget(struct cgroup
*cgrp
)
1118 return css_tryget(&cgrp
->self
);
1121 static void cgroup_put(struct cgroup
*cgrp
)
1123 css_put(&cgrp
->self
);
1127 * cgroup_calc_child_subsys_mask - calculate child_subsys_mask
1128 * @cgrp: the target cgroup
1129 * @subtree_control: the new subtree_control mask to consider
1131 * On the default hierarchy, a subsystem may request other subsystems to be
1132 * enabled together through its ->depends_on mask. In such cases, more
1133 * subsystems than specified in "cgroup.subtree_control" may be enabled.
1135 * This function calculates which subsystems need to be enabled if
1136 * @subtree_control is to be applied to @cgrp. The returned mask is always
1137 * a superset of @subtree_control and follows the usual hierarchy rules.
1139 static unsigned long cgroup_calc_child_subsys_mask(struct cgroup
*cgrp
,
1140 unsigned long subtree_control
)
1142 struct cgroup
*parent
= cgroup_parent(cgrp
);
1143 unsigned long cur_ss_mask
= subtree_control
;
1144 struct cgroup_subsys
*ss
;
1147 lockdep_assert_held(&cgroup_mutex
);
1149 if (!cgroup_on_dfl(cgrp
))
1153 unsigned long new_ss_mask
= cur_ss_mask
;
1155 for_each_subsys_which(ss
, ssid
, &cur_ss_mask
)
1156 new_ss_mask
|= ss
->depends_on
;
1159 * Mask out subsystems which aren't available. This can
1160 * happen only if some depended-upon subsystems were bound
1161 * to non-default hierarchies.
1164 new_ss_mask
&= parent
->child_subsys_mask
;
1166 new_ss_mask
&= cgrp
->root
->subsys_mask
;
1168 if (new_ss_mask
== cur_ss_mask
)
1170 cur_ss_mask
= new_ss_mask
;
1177 * cgroup_refresh_child_subsys_mask - update child_subsys_mask
1178 * @cgrp: the target cgroup
1180 * Update @cgrp->child_subsys_mask according to the current
1181 * @cgrp->subtree_control using cgroup_calc_child_subsys_mask().
1183 static void cgroup_refresh_child_subsys_mask(struct cgroup
*cgrp
)
1185 cgrp
->child_subsys_mask
=
1186 cgroup_calc_child_subsys_mask(cgrp
, cgrp
->subtree_control
);
1190 * cgroup_kn_unlock - unlocking helper for cgroup kernfs methods
1191 * @kn: the kernfs_node being serviced
1193 * This helper undoes cgroup_kn_lock_live() and should be invoked before
1194 * the method finishes if locking succeeded. Note that once this function
1195 * returns the cgroup returned by cgroup_kn_lock_live() may become
1196 * inaccessible any time. If the caller intends to continue to access the
1197 * cgroup, it should pin it before invoking this function.
1199 static void cgroup_kn_unlock(struct kernfs_node
*kn
)
1201 struct cgroup
*cgrp
;
1203 if (kernfs_type(kn
) == KERNFS_DIR
)
1206 cgrp
= kn
->parent
->priv
;
1208 mutex_unlock(&cgroup_mutex
);
1210 kernfs_unbreak_active_protection(kn
);
1215 * cgroup_kn_lock_live - locking helper for cgroup kernfs methods
1216 * @kn: the kernfs_node being serviced
1218 * This helper is to be used by a cgroup kernfs method currently servicing
1219 * @kn. It breaks the active protection, performs cgroup locking and
1220 * verifies that the associated cgroup is alive. Returns the cgroup if
1221 * alive; otherwise, %NULL. A successful return should be undone by a
1222 * matching cgroup_kn_unlock() invocation.
1224 * Any cgroup kernfs method implementation which requires locking the
1225 * associated cgroup should use this helper. It avoids nesting cgroup
1226 * locking under kernfs active protection and allows all kernfs operations
1227 * including self-removal.
1229 static struct cgroup
*cgroup_kn_lock_live(struct kernfs_node
*kn
)
1231 struct cgroup
*cgrp
;
1233 if (kernfs_type(kn
) == KERNFS_DIR
)
1236 cgrp
= kn
->parent
->priv
;
1239 * We're gonna grab cgroup_mutex which nests outside kernfs
1240 * active_ref. cgroup liveliness check alone provides enough
1241 * protection against removal. Ensure @cgrp stays accessible and
1242 * break the active_ref protection.
1244 if (!cgroup_tryget(cgrp
))
1246 kernfs_break_active_protection(kn
);
1248 mutex_lock(&cgroup_mutex
);
1250 if (!cgroup_is_dead(cgrp
))
1253 cgroup_kn_unlock(kn
);
1257 static void cgroup_rm_file(struct cgroup
*cgrp
, const struct cftype
*cft
)
1259 char name
[CGROUP_FILE_NAME_MAX
];
1261 lockdep_assert_held(&cgroup_mutex
);
1262 kernfs_remove_by_name(cgrp
->kn
, cgroup_file_name(cgrp
, cft
, name
));
1266 * cgroup_clear_dir - remove subsys files in a cgroup directory
1267 * @cgrp: target cgroup
1268 * @subsys_mask: mask of the subsystem ids whose files should be removed
1270 static void cgroup_clear_dir(struct cgroup
*cgrp
, unsigned long subsys_mask
)
1272 struct cgroup_subsys
*ss
;
1275 for_each_subsys(ss
, i
) {
1276 struct cftype
*cfts
;
1278 if (!(subsys_mask
& (1 << i
)))
1280 list_for_each_entry(cfts
, &ss
->cfts
, node
)
1281 cgroup_addrm_files(cgrp
, cfts
, false);
1285 static int rebind_subsystems(struct cgroup_root
*dst_root
,
1286 unsigned long ss_mask
)
1288 struct cgroup_subsys
*ss
;
1289 unsigned long tmp_ss_mask
;
1292 lockdep_assert_held(&cgroup_mutex
);
1294 for_each_subsys_which(ss
, ssid
, &ss_mask
) {
1295 /* if @ss has non-root csses attached to it, can't move */
1296 if (css_next_child(NULL
, cgroup_css(&ss
->root
->cgrp
, ss
)))
1299 /* can't move between two non-dummy roots either */
1300 if (ss
->root
!= &cgrp_dfl_root
&& dst_root
!= &cgrp_dfl_root
)
1304 /* skip creating root files on dfl_root for inhibited subsystems */
1305 tmp_ss_mask
= ss_mask
;
1306 if (dst_root
== &cgrp_dfl_root
)
1307 tmp_ss_mask
&= ~cgrp_dfl_root_inhibit_ss_mask
;
1309 ret
= cgroup_populate_dir(&dst_root
->cgrp
, tmp_ss_mask
);
1311 if (dst_root
!= &cgrp_dfl_root
)
1315 * Rebinding back to the default root is not allowed to
1316 * fail. Using both default and non-default roots should
1317 * be rare. Moving subsystems back and forth even more so.
1318 * Just warn about it and continue.
1320 if (cgrp_dfl_root_visible
) {
1321 pr_warn("failed to create files (%d) while rebinding 0x%lx to default root\n",
1323 pr_warn("you may retry by moving them to a different hierarchy and unbinding\n");
1328 * Nothing can fail from this point on. Remove files for the
1329 * removed subsystems and rebind each subsystem.
1331 for_each_subsys_which(ss
, ssid
, &ss_mask
)
1332 cgroup_clear_dir(&ss
->root
->cgrp
, 1 << ssid
);
1334 for_each_subsys_which(ss
, ssid
, &ss_mask
) {
1335 struct cgroup_root
*src_root
;
1336 struct cgroup_subsys_state
*css
;
1337 struct css_set
*cset
;
1339 src_root
= ss
->root
;
1340 css
= cgroup_css(&src_root
->cgrp
, ss
);
1342 WARN_ON(!css
|| cgroup_css(&dst_root
->cgrp
, ss
));
1344 RCU_INIT_POINTER(src_root
->cgrp
.subsys
[ssid
], NULL
);
1345 rcu_assign_pointer(dst_root
->cgrp
.subsys
[ssid
], css
);
1346 ss
->root
= dst_root
;
1347 css
->cgroup
= &dst_root
->cgrp
;
1349 down_write(&css_set_rwsem
);
1350 hash_for_each(css_set_table
, i
, cset
, hlist
)
1351 list_move_tail(&cset
->e_cset_node
[ss
->id
],
1352 &dst_root
->cgrp
.e_csets
[ss
->id
]);
1353 up_write(&css_set_rwsem
);
1355 src_root
->subsys_mask
&= ~(1 << ssid
);
1356 src_root
->cgrp
.subtree_control
&= ~(1 << ssid
);
1357 cgroup_refresh_child_subsys_mask(&src_root
->cgrp
);
1359 /* default hierarchy doesn't enable controllers by default */
1360 dst_root
->subsys_mask
|= 1 << ssid
;
1361 if (dst_root
!= &cgrp_dfl_root
) {
1362 dst_root
->cgrp
.subtree_control
|= 1 << ssid
;
1363 cgroup_refresh_child_subsys_mask(&dst_root
->cgrp
);
1370 kernfs_activate(dst_root
->cgrp
.kn
);
1374 static int cgroup_show_options(struct seq_file
*seq
,
1375 struct kernfs_root
*kf_root
)
1377 struct cgroup_root
*root
= cgroup_root_from_kf(kf_root
);
1378 struct cgroup_subsys
*ss
;
1381 if (root
!= &cgrp_dfl_root
)
1382 for_each_subsys(ss
, ssid
)
1383 if (root
->subsys_mask
& (1 << ssid
))
1384 seq_show_option(seq
, ss
->legacy_name
, NULL
);
1385 if (root
->flags
& CGRP_ROOT_NOPREFIX
)
1386 seq_puts(seq
, ",noprefix");
1387 if (root
->flags
& CGRP_ROOT_XATTR
)
1388 seq_puts(seq
, ",xattr");
1390 spin_lock(&release_agent_path_lock
);
1391 if (strlen(root
->release_agent_path
))
1392 seq_show_option(seq
, "release_agent",
1393 root
->release_agent_path
);
1394 spin_unlock(&release_agent_path_lock
);
1396 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN
, &root
->cgrp
.flags
))
1397 seq_puts(seq
, ",clone_children");
1398 if (strlen(root
->name
))
1399 seq_show_option(seq
, "name", root
->name
);
1403 struct cgroup_sb_opts
{
1404 unsigned long subsys_mask
;
1406 char *release_agent
;
1407 bool cpuset_clone_children
;
1409 /* User explicitly requested empty subsystem */
1413 static int parse_cgroupfs_options(char *data
, struct cgroup_sb_opts
*opts
)
1415 char *token
, *o
= data
;
1416 bool all_ss
= false, one_ss
= false;
1417 unsigned long mask
= -1UL;
1418 struct cgroup_subsys
*ss
;
1422 #ifdef CONFIG_CPUSETS
1423 mask
= ~(1U << cpuset_cgrp_id
);
1426 memset(opts
, 0, sizeof(*opts
));
1428 while ((token
= strsep(&o
, ",")) != NULL
) {
1433 if (!strcmp(token
, "none")) {
1434 /* Explicitly have no subsystems */
1438 if (!strcmp(token
, "all")) {
1439 /* Mutually exclusive option 'all' + subsystem name */
1445 if (!strcmp(token
, "__DEVEL__sane_behavior")) {
1446 opts
->flags
|= CGRP_ROOT_SANE_BEHAVIOR
;
1449 if (!strcmp(token
, "noprefix")) {
1450 opts
->flags
|= CGRP_ROOT_NOPREFIX
;
1453 if (!strcmp(token
, "clone_children")) {
1454 opts
->cpuset_clone_children
= true;
1457 if (!strcmp(token
, "xattr")) {
1458 opts
->flags
|= CGRP_ROOT_XATTR
;
1461 if (!strncmp(token
, "release_agent=", 14)) {
1462 /* Specifying two release agents is forbidden */
1463 if (opts
->release_agent
)
1465 opts
->release_agent
=
1466 kstrndup(token
+ 14, PATH_MAX
- 1, GFP_KERNEL
);
1467 if (!opts
->release_agent
)
1471 if (!strncmp(token
, "name=", 5)) {
1472 const char *name
= token
+ 5;
1473 /* Can't specify an empty name */
1476 /* Must match [\w.-]+ */
1477 for (i
= 0; i
< strlen(name
); i
++) {
1481 if ((c
== '.') || (c
== '-') || (c
== '_'))
1485 /* Specifying two names is forbidden */
1488 opts
->name
= kstrndup(name
,
1489 MAX_CGROUP_ROOT_NAMELEN
- 1,
1497 for_each_subsys(ss
, i
) {
1498 if (strcmp(token
, ss
->legacy_name
))
1503 /* Mutually exclusive option 'all' + subsystem name */
1506 opts
->subsys_mask
|= (1 << i
);
1511 if (i
== CGROUP_SUBSYS_COUNT
)
1515 if (opts
->flags
& CGRP_ROOT_SANE_BEHAVIOR
) {
1516 pr_warn("sane_behavior: this is still under development and its behaviors will change, proceed at your own risk\n");
1518 pr_err("sane_behavior: no other mount options allowed\n");
1525 * If the 'all' option was specified select all the subsystems,
1526 * otherwise if 'none', 'name=' and a subsystem name options were
1527 * not specified, let's default to 'all'
1529 if (all_ss
|| (!one_ss
&& !opts
->none
&& !opts
->name
))
1530 for_each_subsys(ss
, i
)
1532 opts
->subsys_mask
|= (1 << i
);
1535 * We either have to specify by name or by subsystems. (So all
1536 * empty hierarchies must have a name).
1538 if (!opts
->subsys_mask
&& !opts
->name
)
1542 * Option noprefix was introduced just for backward compatibility
1543 * with the old cpuset, so we allow noprefix only if mounting just
1544 * the cpuset subsystem.
1546 if ((opts
->flags
& CGRP_ROOT_NOPREFIX
) && (opts
->subsys_mask
& mask
))
1549 /* Can't specify "none" and some subsystems */
1550 if (opts
->subsys_mask
&& opts
->none
)
1556 static int cgroup_remount(struct kernfs_root
*kf_root
, int *flags
, char *data
)
1559 struct cgroup_root
*root
= cgroup_root_from_kf(kf_root
);
1560 struct cgroup_sb_opts opts
;
1561 unsigned long added_mask
, removed_mask
;
1563 if (root
== &cgrp_dfl_root
) {
1564 pr_err("remount is not allowed\n");
1568 mutex_lock(&cgroup_mutex
);
1570 /* See what subsystems are wanted */
1571 ret
= parse_cgroupfs_options(data
, &opts
);
1575 if (opts
.subsys_mask
!= root
->subsys_mask
|| opts
.release_agent
)
1576 pr_warn("option changes via remount are deprecated (pid=%d comm=%s)\n",
1577 task_tgid_nr(current
), current
->comm
);
1579 added_mask
= opts
.subsys_mask
& ~root
->subsys_mask
;
1580 removed_mask
= root
->subsys_mask
& ~opts
.subsys_mask
;
1582 /* Don't allow flags or name to change at remount */
1583 if ((opts
.flags
^ root
->flags
) ||
1584 (opts
.name
&& strcmp(opts
.name
, root
->name
))) {
1585 pr_err("option or name mismatch, new: 0x%x \"%s\", old: 0x%x \"%s\"\n",
1586 opts
.flags
, opts
.name
?: "", root
->flags
, root
->name
);
1591 /* remounting is not allowed for populated hierarchies */
1592 if (!list_empty(&root
->cgrp
.self
.children
)) {
1597 ret
= rebind_subsystems(root
, added_mask
);
1601 rebind_subsystems(&cgrp_dfl_root
, removed_mask
);
1603 if (opts
.release_agent
) {
1604 spin_lock(&release_agent_path_lock
);
1605 strcpy(root
->release_agent_path
, opts
.release_agent
);
1606 spin_unlock(&release_agent_path_lock
);
1609 kfree(opts
.release_agent
);
1611 mutex_unlock(&cgroup_mutex
);
1616 * To reduce the fork() overhead for systems that are not actually using
1617 * their cgroups capability, we don't maintain the lists running through
1618 * each css_set to its tasks until we see the list actually used - in other
1619 * words after the first mount.
1621 static bool use_task_css_set_links __read_mostly
;
1623 static void cgroup_enable_task_cg_lists(void)
1625 struct task_struct
*p
, *g
;
1627 down_write(&css_set_rwsem
);
1629 if (use_task_css_set_links
)
1632 use_task_css_set_links
= true;
1635 * We need tasklist_lock because RCU is not safe against
1636 * while_each_thread(). Besides, a forking task that has passed
1637 * cgroup_post_fork() without seeing use_task_css_set_links = 1
1638 * is not guaranteed to have its child immediately visible in the
1639 * tasklist if we walk through it with RCU.
1641 read_lock(&tasklist_lock
);
1642 do_each_thread(g
, p
) {
1643 WARN_ON_ONCE(!list_empty(&p
->cg_list
) ||
1644 task_css_set(p
) != &init_css_set
);
1647 * We should check if the process is exiting, otherwise
1648 * it will race with cgroup_exit() in that the list
1649 * entry won't be deleted though the process has exited.
1650 * Do it while holding siglock so that we don't end up
1651 * racing against cgroup_exit().
1653 spin_lock_irq(&p
->sighand
->siglock
);
1654 if (!(p
->flags
& PF_EXITING
)) {
1655 struct css_set
*cset
= task_css_set(p
);
1657 list_add(&p
->cg_list
, &cset
->tasks
);
1660 spin_unlock_irq(&p
->sighand
->siglock
);
1661 } while_each_thread(g
, p
);
1662 read_unlock(&tasklist_lock
);
1664 up_write(&css_set_rwsem
);
1667 static void init_cgroup_housekeeping(struct cgroup
*cgrp
)
1669 struct cgroup_subsys
*ss
;
1672 INIT_LIST_HEAD(&cgrp
->self
.sibling
);
1673 INIT_LIST_HEAD(&cgrp
->self
.children
);
1674 INIT_LIST_HEAD(&cgrp
->cset_links
);
1675 INIT_LIST_HEAD(&cgrp
->pidlists
);
1676 mutex_init(&cgrp
->pidlist_mutex
);
1677 cgrp
->self
.cgroup
= cgrp
;
1678 cgrp
->self
.flags
|= CSS_ONLINE
;
1680 for_each_subsys(ss
, ssid
)
1681 INIT_LIST_HEAD(&cgrp
->e_csets
[ssid
]);
1683 init_waitqueue_head(&cgrp
->offline_waitq
);
1684 INIT_WORK(&cgrp
->release_agent_work
, cgroup_release_agent
);
1687 static void init_cgroup_root(struct cgroup_root
*root
,
1688 struct cgroup_sb_opts
*opts
)
1690 struct cgroup
*cgrp
= &root
->cgrp
;
1692 INIT_LIST_HEAD(&root
->root_list
);
1693 atomic_set(&root
->nr_cgrps
, 1);
1695 init_cgroup_housekeeping(cgrp
);
1696 idr_init(&root
->cgroup_idr
);
1698 root
->flags
= opts
->flags
;
1699 if (opts
->release_agent
)
1700 strcpy(root
->release_agent_path
, opts
->release_agent
);
1702 strcpy(root
->name
, opts
->name
);
1703 if (opts
->cpuset_clone_children
)
1704 set_bit(CGRP_CPUSET_CLONE_CHILDREN
, &root
->cgrp
.flags
);
1707 static int cgroup_setup_root(struct cgroup_root
*root
, unsigned long ss_mask
)
1709 LIST_HEAD(tmp_links
);
1710 struct cgroup
*root_cgrp
= &root
->cgrp
;
1711 struct cftype
*base_files
;
1712 struct css_set
*cset
;
1715 lockdep_assert_held(&cgroup_mutex
);
1717 ret
= cgroup_idr_alloc(&root
->cgroup_idr
, root_cgrp
, 1, 2, GFP_KERNEL
);
1720 root_cgrp
->id
= ret
;
1722 ret
= percpu_ref_init(&root_cgrp
->self
.refcnt
, css_release
, 0,
1728 * We're accessing css_set_count without locking css_set_rwsem here,
1729 * but that's OK - it can only be increased by someone holding
1730 * cgroup_lock, and that's us. The worst that can happen is that we
1731 * have some link structures left over
1733 ret
= allocate_cgrp_cset_links(css_set_count
, &tmp_links
);
1737 ret
= cgroup_init_root_id(root
);
1741 root
->kf_root
= kernfs_create_root(&cgroup_kf_syscall_ops
,
1742 KERNFS_ROOT_CREATE_DEACTIVATED
,
1744 if (IS_ERR(root
->kf_root
)) {
1745 ret
= PTR_ERR(root
->kf_root
);
1748 root_cgrp
->kn
= root
->kf_root
->kn
;
1750 if (root
== &cgrp_dfl_root
)
1751 base_files
= cgroup_dfl_base_files
;
1753 base_files
= cgroup_legacy_base_files
;
1755 ret
= cgroup_addrm_files(root_cgrp
, base_files
, true);
1759 ret
= rebind_subsystems(root
, ss_mask
);
1764 * There must be no failure case after here, since rebinding takes
1765 * care of subsystems' refcounts, which are explicitly dropped in
1766 * the failure exit path.
1768 list_add(&root
->root_list
, &cgroup_roots
);
1769 cgroup_root_count
++;
1772 * Link the root cgroup in this hierarchy into all the css_set
1775 down_write(&css_set_rwsem
);
1776 hash_for_each(css_set_table
, i
, cset
, hlist
)
1777 link_css_set(&tmp_links
, cset
, root_cgrp
);
1778 up_write(&css_set_rwsem
);
1780 BUG_ON(!list_empty(&root_cgrp
->self
.children
));
1781 BUG_ON(atomic_read(&root
->nr_cgrps
) != 1);
1783 kernfs_activate(root_cgrp
->kn
);
1788 kernfs_destroy_root(root
->kf_root
);
1789 root
->kf_root
= NULL
;
1791 cgroup_exit_root_id(root
);
1793 percpu_ref_exit(&root_cgrp
->self
.refcnt
);
1795 free_cgrp_cset_links(&tmp_links
);
1799 static struct dentry
*cgroup_mount(struct file_system_type
*fs_type
,
1800 int flags
, const char *unused_dev_name
,
1803 struct super_block
*pinned_sb
= NULL
;
1804 struct cgroup_subsys
*ss
;
1805 struct cgroup_root
*root
;
1806 struct cgroup_sb_opts opts
;
1807 struct dentry
*dentry
;
1813 * The first time anyone tries to mount a cgroup, enable the list
1814 * linking each css_set to its tasks and fix up all existing tasks.
1816 if (!use_task_css_set_links
)
1817 cgroup_enable_task_cg_lists();
1819 mutex_lock(&cgroup_mutex
);
1821 /* First find the desired set of subsystems */
1822 ret
= parse_cgroupfs_options(data
, &opts
);
1826 /* look for a matching existing root */
1827 if (opts
.flags
& CGRP_ROOT_SANE_BEHAVIOR
) {
1828 cgrp_dfl_root_visible
= true;
1829 root
= &cgrp_dfl_root
;
1830 cgroup_get(&root
->cgrp
);
1836 * Destruction of cgroup root is asynchronous, so subsystems may
1837 * still be dying after the previous unmount. Let's drain the
1838 * dying subsystems. We just need to ensure that the ones
1839 * unmounted previously finish dying and don't care about new ones
1840 * starting. Testing ref liveliness is good enough.
1842 for_each_subsys(ss
, i
) {
1843 if (!(opts
.subsys_mask
& (1 << i
)) ||
1844 ss
->root
== &cgrp_dfl_root
)
1847 if (!percpu_ref_tryget_live(&ss
->root
->cgrp
.self
.refcnt
)) {
1848 mutex_unlock(&cgroup_mutex
);
1850 ret
= restart_syscall();
1853 cgroup_put(&ss
->root
->cgrp
);
1856 for_each_root(root
) {
1857 bool name_match
= false;
1859 if (root
== &cgrp_dfl_root
)
1863 * If we asked for a name then it must match. Also, if
1864 * name matches but sybsys_mask doesn't, we should fail.
1865 * Remember whether name matched.
1868 if (strcmp(opts
.name
, root
->name
))
1874 * If we asked for subsystems (or explicitly for no
1875 * subsystems) then they must match.
1877 if ((opts
.subsys_mask
|| opts
.none
) &&
1878 (opts
.subsys_mask
!= root
->subsys_mask
)) {
1885 if (root
->flags
^ opts
.flags
)
1886 pr_warn("new mount options do not match the existing superblock, will be ignored\n");
1889 * We want to reuse @root whose lifetime is governed by its
1890 * ->cgrp. Let's check whether @root is alive and keep it
1891 * that way. As cgroup_kill_sb() can happen anytime, we
1892 * want to block it by pinning the sb so that @root doesn't
1893 * get killed before mount is complete.
1895 * With the sb pinned, tryget_live can reliably indicate
1896 * whether @root can be reused. If it's being killed,
1897 * drain it. We can use wait_queue for the wait but this
1898 * path is super cold. Let's just sleep a bit and retry.
1900 pinned_sb
= kernfs_pin_sb(root
->kf_root
, NULL
);
1901 if (IS_ERR(pinned_sb
) ||
1902 !percpu_ref_tryget_live(&root
->cgrp
.self
.refcnt
)) {
1903 mutex_unlock(&cgroup_mutex
);
1904 if (!IS_ERR_OR_NULL(pinned_sb
))
1905 deactivate_super(pinned_sb
);
1907 ret
= restart_syscall();
1916 * No such thing, create a new one. name= matching without subsys
1917 * specification is allowed for already existing hierarchies but we
1918 * can't create new one without subsys specification.
1920 if (!opts
.subsys_mask
&& !opts
.none
) {
1925 root
= kzalloc(sizeof(*root
), GFP_KERNEL
);
1931 init_cgroup_root(root
, &opts
);
1933 ret
= cgroup_setup_root(root
, opts
.subsys_mask
);
1935 cgroup_free_root(root
);
1938 mutex_unlock(&cgroup_mutex
);
1940 kfree(opts
.release_agent
);
1944 return ERR_PTR(ret
);
1946 dentry
= kernfs_mount(fs_type
, flags
, root
->kf_root
,
1947 CGROUP_SUPER_MAGIC
, &new_sb
);
1948 if (IS_ERR(dentry
) || !new_sb
)
1949 cgroup_put(&root
->cgrp
);
1952 * If @pinned_sb, we're reusing an existing root and holding an
1953 * extra ref on its sb. Mount is complete. Put the extra ref.
1957 deactivate_super(pinned_sb
);
1963 static void cgroup_kill_sb(struct super_block
*sb
)
1965 struct kernfs_root
*kf_root
= kernfs_root_from_sb(sb
);
1966 struct cgroup_root
*root
= cgroup_root_from_kf(kf_root
);
1969 * If @root doesn't have any mounts or children, start killing it.
1970 * This prevents new mounts by disabling percpu_ref_tryget_live().
1971 * cgroup_mount() may wait for @root's release.
1973 * And don't kill the default root.
1975 if (!list_empty(&root
->cgrp
.self
.children
) ||
1976 root
== &cgrp_dfl_root
)
1977 cgroup_put(&root
->cgrp
);
1979 percpu_ref_kill(&root
->cgrp
.self
.refcnt
);
1984 static struct file_system_type cgroup_fs_type
= {
1986 .mount
= cgroup_mount
,
1987 .kill_sb
= cgroup_kill_sb
,
1991 * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
1992 * @task: target task
1993 * @buf: the buffer to write the path into
1994 * @buflen: the length of the buffer
1996 * Determine @task's cgroup on the first (the one with the lowest non-zero
1997 * hierarchy_id) cgroup hierarchy and copy its path into @buf. This
1998 * function grabs cgroup_mutex and shouldn't be used inside locks used by
1999 * cgroup controller callbacks.
2001 * Return value is the same as kernfs_path().
2003 char *task_cgroup_path(struct task_struct
*task
, char *buf
, size_t buflen
)
2005 struct cgroup_root
*root
;
2006 struct cgroup
*cgrp
;
2007 int hierarchy_id
= 1;
2010 mutex_lock(&cgroup_mutex
);
2011 down_read(&css_set_rwsem
);
2013 root
= idr_get_next(&cgroup_hierarchy_idr
, &hierarchy_id
);
2016 cgrp
= task_cgroup_from_root(task
, root
);
2017 path
= cgroup_path(cgrp
, buf
, buflen
);
2019 /* if no hierarchy exists, everyone is in "/" */
2020 if (strlcpy(buf
, "/", buflen
) < buflen
)
2024 up_read(&css_set_rwsem
);
2025 mutex_unlock(&cgroup_mutex
);
2028 EXPORT_SYMBOL_GPL(task_cgroup_path
);
2030 /* used to track tasks and other necessary states during migration */
2031 struct cgroup_taskset
{
2032 /* the src and dst cset list running through cset->mg_node */
2033 struct list_head src_csets
;
2034 struct list_head dst_csets
;
2037 * Fields for cgroup_taskset_*() iteration.
2039 * Before migration is committed, the target migration tasks are on
2040 * ->mg_tasks of the csets on ->src_csets. After, on ->mg_tasks of
2041 * the csets on ->dst_csets. ->csets point to either ->src_csets
2042 * or ->dst_csets depending on whether migration is committed.
2044 * ->cur_csets and ->cur_task point to the current task position
2047 struct list_head
*csets
;
2048 struct css_set
*cur_cset
;
2049 struct task_struct
*cur_task
;
2053 * cgroup_taskset_first - reset taskset and return the first task
2054 * @tset: taskset of interest
2056 * @tset iteration is initialized and the first task is returned.
2058 struct task_struct
*cgroup_taskset_first(struct cgroup_taskset
*tset
)
2060 tset
->cur_cset
= list_first_entry(tset
->csets
, struct css_set
, mg_node
);
2061 tset
->cur_task
= NULL
;
2063 return cgroup_taskset_next(tset
);
2067 * cgroup_taskset_next - iterate to the next task in taskset
2068 * @tset: taskset of interest
2070 * Return the next task in @tset. Iteration must have been initialized
2071 * with cgroup_taskset_first().
2073 struct task_struct
*cgroup_taskset_next(struct cgroup_taskset
*tset
)
2075 struct css_set
*cset
= tset
->cur_cset
;
2076 struct task_struct
*task
= tset
->cur_task
;
2078 while (&cset
->mg_node
!= tset
->csets
) {
2080 task
= list_first_entry(&cset
->mg_tasks
,
2081 struct task_struct
, cg_list
);
2083 task
= list_next_entry(task
, cg_list
);
2085 if (&task
->cg_list
!= &cset
->mg_tasks
) {
2086 tset
->cur_cset
= cset
;
2087 tset
->cur_task
= task
;
2091 cset
= list_next_entry(cset
, mg_node
);
2099 * cgroup_task_migrate - move a task from one cgroup to another.
2100 * @old_cgrp: the cgroup @tsk is being migrated from
2101 * @tsk: the task being migrated
2102 * @new_cset: the new css_set @tsk is being attached to
2104 * Must be called with cgroup_mutex, threadgroup and css_set_rwsem locked.
2106 static void cgroup_task_migrate(struct cgroup
*old_cgrp
,
2107 struct task_struct
*tsk
,
2108 struct css_set
*new_cset
)
2110 struct css_set
*old_cset
;
2112 lockdep_assert_held(&cgroup_mutex
);
2113 lockdep_assert_held(&css_set_rwsem
);
2116 * We are synchronized through threadgroup_lock() against PF_EXITING
2117 * setting such that we can't race against cgroup_exit() changing the
2118 * css_set to init_css_set and dropping the old one.
2120 WARN_ON_ONCE(tsk
->flags
& PF_EXITING
);
2121 old_cset
= task_css_set(tsk
);
2123 get_css_set(new_cset
);
2124 rcu_assign_pointer(tsk
->cgroups
, new_cset
);
2127 * Use move_tail so that cgroup_taskset_first() still returns the
2128 * leader after migration. This works because cgroup_migrate()
2129 * ensures that the dst_cset of the leader is the first on the
2130 * tset's dst_csets list.
2132 list_move_tail(&tsk
->cg_list
, &new_cset
->mg_tasks
);
2135 * We just gained a reference on old_cset by taking it from the
2136 * task. As trading it for new_cset is protected by cgroup_mutex,
2137 * we're safe to drop it here; it will be freed under RCU.
2139 put_css_set_locked(old_cset
);
2143 * cgroup_migrate_finish - cleanup after attach
2144 * @preloaded_csets: list of preloaded css_sets
2146 * Undo cgroup_migrate_add_src() and cgroup_migrate_prepare_dst(). See
2147 * those functions for details.
2149 static void cgroup_migrate_finish(struct list_head
*preloaded_csets
)
2151 struct css_set
*cset
, *tmp_cset
;
2153 lockdep_assert_held(&cgroup_mutex
);
2155 down_write(&css_set_rwsem
);
2156 list_for_each_entry_safe(cset
, tmp_cset
, preloaded_csets
, mg_preload_node
) {
2157 cset
->mg_src_cgrp
= NULL
;
2158 cset
->mg_dst_cset
= NULL
;
2159 list_del_init(&cset
->mg_preload_node
);
2160 put_css_set_locked(cset
);
2162 up_write(&css_set_rwsem
);
2166 * cgroup_migrate_add_src - add a migration source css_set
2167 * @src_cset: the source css_set to add
2168 * @dst_cgrp: the destination cgroup
2169 * @preloaded_csets: list of preloaded css_sets
2171 * Tasks belonging to @src_cset are about to be migrated to @dst_cgrp. Pin
2172 * @src_cset and add it to @preloaded_csets, which should later be cleaned
2173 * up by cgroup_migrate_finish().
2175 * This function may be called without holding threadgroup_lock even if the
2176 * target is a process. Threads may be created and destroyed but as long
2177 * as cgroup_mutex is not dropped, no new css_set can be put into play and
2178 * the preloaded css_sets are guaranteed to cover all migrations.
2180 static void cgroup_migrate_add_src(struct css_set
*src_cset
,
2181 struct cgroup
*dst_cgrp
,
2182 struct list_head
*preloaded_csets
)
2184 struct cgroup
*src_cgrp
;
2186 lockdep_assert_held(&cgroup_mutex
);
2187 lockdep_assert_held(&css_set_rwsem
);
2189 src_cgrp
= cset_cgroup_from_root(src_cset
, dst_cgrp
->root
);
2191 if (!list_empty(&src_cset
->mg_preload_node
))
2194 WARN_ON(src_cset
->mg_src_cgrp
);
2195 WARN_ON(!list_empty(&src_cset
->mg_tasks
));
2196 WARN_ON(!list_empty(&src_cset
->mg_node
));
2198 src_cset
->mg_src_cgrp
= src_cgrp
;
2199 get_css_set(src_cset
);
2200 list_add(&src_cset
->mg_preload_node
, preloaded_csets
);
2204 * cgroup_migrate_prepare_dst - prepare destination css_sets for migration
2205 * @dst_cgrp: the destination cgroup (may be %NULL)
2206 * @preloaded_csets: list of preloaded source css_sets
2208 * Tasks are about to be moved to @dst_cgrp and all the source css_sets
2209 * have been preloaded to @preloaded_csets. This function looks up and
2210 * pins all destination css_sets, links each to its source, and append them
2211 * to @preloaded_csets. If @dst_cgrp is %NULL, the destination of each
2212 * source css_set is assumed to be its cgroup on the default hierarchy.
2214 * This function must be called after cgroup_migrate_add_src() has been
2215 * called on each migration source css_set. After migration is performed
2216 * using cgroup_migrate(), cgroup_migrate_finish() must be called on
2219 static int cgroup_migrate_prepare_dst(struct cgroup
*dst_cgrp
,
2220 struct list_head
*preloaded_csets
)
2223 struct css_set
*src_cset
, *tmp_cset
;
2225 lockdep_assert_held(&cgroup_mutex
);
2228 * Except for the root, child_subsys_mask must be zero for a cgroup
2229 * with tasks so that child cgroups don't compete against tasks.
2231 if (dst_cgrp
&& cgroup_on_dfl(dst_cgrp
) && cgroup_parent(dst_cgrp
) &&
2232 dst_cgrp
->child_subsys_mask
)
2235 /* look up the dst cset for each src cset and link it to src */
2236 list_for_each_entry_safe(src_cset
, tmp_cset
, preloaded_csets
, mg_preload_node
) {
2237 struct css_set
*dst_cset
;
2239 dst_cset
= find_css_set(src_cset
,
2240 dst_cgrp
?: src_cset
->dfl_cgrp
);
2244 WARN_ON_ONCE(src_cset
->mg_dst_cset
|| dst_cset
->mg_dst_cset
);
2247 * If src cset equals dst, it's noop. Drop the src.
2248 * cgroup_migrate() will skip the cset too. Note that we
2249 * can't handle src == dst as some nodes are used by both.
2251 if (src_cset
== dst_cset
) {
2252 src_cset
->mg_src_cgrp
= NULL
;
2253 list_del_init(&src_cset
->mg_preload_node
);
2254 put_css_set(src_cset
);
2255 put_css_set(dst_cset
);
2259 src_cset
->mg_dst_cset
= dst_cset
;
2261 if (list_empty(&dst_cset
->mg_preload_node
))
2262 list_add(&dst_cset
->mg_preload_node
, &csets
);
2264 put_css_set(dst_cset
);
2267 list_splice_tail(&csets
, preloaded_csets
);
2270 cgroup_migrate_finish(&csets
);
2275 * cgroup_migrate - migrate a process or task to a cgroup
2276 * @cgrp: the destination cgroup
2277 * @leader: the leader of the process or the task to migrate
2278 * @threadgroup: whether @leader points to the whole process or a single task
2280 * Migrate a process or task denoted by @leader to @cgrp. If migrating a
2281 * process, the caller must be holding threadgroup_lock of @leader. The
2282 * caller is also responsible for invoking cgroup_migrate_add_src() and
2283 * cgroup_migrate_prepare_dst() on the targets before invoking this
2284 * function and following up with cgroup_migrate_finish().
2286 * As long as a controller's ->can_attach() doesn't fail, this function is
2287 * guaranteed to succeed. This means that, excluding ->can_attach()
2288 * failure, when migrating multiple targets, the success or failure can be
2289 * decided for all targets by invoking group_migrate_prepare_dst() before
2290 * actually starting migrating.
2292 static int cgroup_migrate(struct cgroup
*cgrp
, struct task_struct
*leader
,
2295 struct cgroup_taskset tset
= {
2296 .src_csets
= LIST_HEAD_INIT(tset
.src_csets
),
2297 .dst_csets
= LIST_HEAD_INIT(tset
.dst_csets
),
2298 .csets
= &tset
.src_csets
,
2300 struct cgroup_subsys_state
*css
, *failed_css
= NULL
;
2301 struct css_set
*cset
, *tmp_cset
;
2302 struct task_struct
*task
, *tmp_task
;
2306 * Prevent freeing of tasks while we take a snapshot. Tasks that are
2307 * already PF_EXITING could be freed from underneath us unless we
2308 * take an rcu_read_lock.
2310 down_write(&css_set_rwsem
);
2314 /* @task either already exited or can't exit until the end */
2315 if (task
->flags
& PF_EXITING
)
2318 /* leave @task alone if post_fork() hasn't linked it yet */
2319 if (list_empty(&task
->cg_list
))
2322 cset
= task_css_set(task
);
2323 if (!cset
->mg_src_cgrp
)
2327 * cgroup_taskset_first() must always return the leader.
2328 * Take care to avoid disturbing the ordering.
2330 list_move_tail(&task
->cg_list
, &cset
->mg_tasks
);
2331 if (list_empty(&cset
->mg_node
))
2332 list_add_tail(&cset
->mg_node
, &tset
.src_csets
);
2333 if (list_empty(&cset
->mg_dst_cset
->mg_node
))
2334 list_move_tail(&cset
->mg_dst_cset
->mg_node
,
2339 } while_each_thread(leader
, task
);
2341 up_write(&css_set_rwsem
);
2343 /* methods shouldn't be called if no task is actually migrating */
2344 if (list_empty(&tset
.src_csets
))
2347 /* check that we can legitimately attach to the cgroup */
2348 for_each_e_css(css
, i
, cgrp
) {
2349 if (css
->ss
->can_attach
) {
2350 ret
= css
->ss
->can_attach(css
, &tset
);
2353 goto out_cancel_attach
;
2359 * Now that we're guaranteed success, proceed to move all tasks to
2360 * the new cgroup. There are no failure cases after here, so this
2361 * is the commit point.
2363 down_write(&css_set_rwsem
);
2364 list_for_each_entry(cset
, &tset
.src_csets
, mg_node
) {
2365 list_for_each_entry_safe(task
, tmp_task
, &cset
->mg_tasks
, cg_list
)
2366 cgroup_task_migrate(cset
->mg_src_cgrp
, task
,
2369 up_write(&css_set_rwsem
);
2372 * Migration is committed, all target tasks are now on dst_csets.
2373 * Nothing is sensitive to fork() after this point. Notify
2374 * controllers that migration is complete.
2376 tset
.csets
= &tset
.dst_csets
;
2378 for_each_e_css(css
, i
, cgrp
)
2379 if (css
->ss
->attach
)
2380 css
->ss
->attach(css
, &tset
);
2383 goto out_release_tset
;
2386 for_each_e_css(css
, i
, cgrp
) {
2387 if (css
== failed_css
)
2389 if (css
->ss
->cancel_attach
)
2390 css
->ss
->cancel_attach(css
, &tset
);
2393 down_write(&css_set_rwsem
);
2394 list_splice_init(&tset
.dst_csets
, &tset
.src_csets
);
2395 list_for_each_entry_safe(cset
, tmp_cset
, &tset
.src_csets
, mg_node
) {
2396 list_splice_tail_init(&cset
->mg_tasks
, &cset
->tasks
);
2397 list_del_init(&cset
->mg_node
);
2399 up_write(&css_set_rwsem
);
2404 * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
2405 * @dst_cgrp: the cgroup to attach to
2406 * @leader: the task or the leader of the threadgroup to be attached
2407 * @threadgroup: attach the whole threadgroup?
2409 * Call holding cgroup_mutex and threadgroup_lock of @leader.
2411 static int cgroup_attach_task(struct cgroup
*dst_cgrp
,
2412 struct task_struct
*leader
, bool threadgroup
)
2414 LIST_HEAD(preloaded_csets
);
2415 struct task_struct
*task
;
2418 /* look up all src csets */
2419 down_read(&css_set_rwsem
);
2423 cgroup_migrate_add_src(task_css_set(task
), dst_cgrp
,
2427 } while_each_thread(leader
, task
);
2429 up_read(&css_set_rwsem
);
2431 /* prepare dst csets and commit */
2432 ret
= cgroup_migrate_prepare_dst(dst_cgrp
, &preloaded_csets
);
2434 ret
= cgroup_migrate(dst_cgrp
, leader
, threadgroup
);
2436 cgroup_migrate_finish(&preloaded_csets
);
2440 static int cgroup_procs_write_permission(struct task_struct
*task
,
2441 struct cgroup
*dst_cgrp
,
2442 struct kernfs_open_file
*of
)
2444 const struct cred
*cred
= current_cred();
2445 const struct cred
*tcred
= get_task_cred(task
);
2449 * even if we're attaching all tasks in the thread group, we only
2450 * need to check permissions on one of them.
2452 if (!uid_eq(cred
->euid
, GLOBAL_ROOT_UID
) &&
2453 !uid_eq(cred
->euid
, tcred
->uid
) &&
2454 !uid_eq(cred
->euid
, tcred
->suid
))
2457 if (!ret
&& cgroup_on_dfl(dst_cgrp
)) {
2458 struct super_block
*sb
= of
->file
->f_path
.dentry
->d_sb
;
2459 struct cgroup
*cgrp
;
2460 struct inode
*inode
;
2462 down_read(&css_set_rwsem
);
2463 cgrp
= task_cgroup_from_root(task
, &cgrp_dfl_root
);
2464 up_read(&css_set_rwsem
);
2466 while (!cgroup_is_descendant(dst_cgrp
, cgrp
))
2467 cgrp
= cgroup_parent(cgrp
);
2470 inode
= kernfs_get_inode(sb
, cgrp
->procs_kn
);
2472 ret
= inode_permission(inode
, MAY_WRITE
);
2482 * Find the task_struct of the task to attach by vpid and pass it along to the
2483 * function to attach either it or all tasks in its threadgroup. Will lock
2484 * cgroup_mutex and threadgroup.
2486 static ssize_t
__cgroup_procs_write(struct kernfs_open_file
*of
, char *buf
,
2487 size_t nbytes
, loff_t off
, bool threadgroup
)
2489 struct task_struct
*tsk
;
2490 struct cgroup
*cgrp
;
2494 if (kstrtoint(strstrip(buf
), 0, &pid
) || pid
< 0)
2497 cgrp
= cgroup_kn_lock_live(of
->kn
);
2504 tsk
= find_task_by_vpid(pid
);
2508 goto out_unlock_cgroup
;
2515 tsk
= tsk
->group_leader
;
2518 * Workqueue threads may acquire PF_NO_SETAFFINITY and become
2519 * trapped in a cpuset, or RT worker may be born in a cgroup
2520 * with no rt_runtime allocated. Just say no.
2522 if (tsk
== kthreadd_task
|| (tsk
->flags
& PF_NO_SETAFFINITY
)) {
2525 goto out_unlock_cgroup
;
2528 get_task_struct(tsk
);
2531 threadgroup_lock(tsk
);
2533 if (!thread_group_leader(tsk
)) {
2535 * a race with de_thread from another thread's exec()
2536 * may strip us of our leadership, if this happens,
2537 * there is no choice but to throw this task away and
2538 * try again; this is
2539 * "double-double-toil-and-trouble-check locking".
2541 threadgroup_unlock(tsk
);
2542 put_task_struct(tsk
);
2543 goto retry_find_task
;
2547 ret
= cgroup_procs_write_permission(tsk
, cgrp
, of
);
2549 ret
= cgroup_attach_task(cgrp
, tsk
, threadgroup
);
2551 threadgroup_unlock(tsk
);
2553 put_task_struct(tsk
);
2555 cgroup_kn_unlock(of
->kn
);
2556 return ret
?: nbytes
;
2560 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
2561 * @from: attach to all cgroups of a given task
2562 * @tsk: the task to be attached
2564 int cgroup_attach_task_all(struct task_struct
*from
, struct task_struct
*tsk
)
2566 struct cgroup_root
*root
;
2569 mutex_lock(&cgroup_mutex
);
2570 for_each_root(root
) {
2571 struct cgroup
*from_cgrp
;
2573 if (root
== &cgrp_dfl_root
)
2576 down_read(&css_set_rwsem
);
2577 from_cgrp
= task_cgroup_from_root(from
, root
);
2578 up_read(&css_set_rwsem
);
2580 retval
= cgroup_attach_task(from_cgrp
, tsk
, false);
2584 mutex_unlock(&cgroup_mutex
);
2588 EXPORT_SYMBOL_GPL(cgroup_attach_task_all
);
2590 static ssize_t
cgroup_tasks_write(struct kernfs_open_file
*of
,
2591 char *buf
, size_t nbytes
, loff_t off
)
2593 return __cgroup_procs_write(of
, buf
, nbytes
, off
, false);
2596 static ssize_t
cgroup_procs_write(struct kernfs_open_file
*of
,
2597 char *buf
, size_t nbytes
, loff_t off
)
2599 return __cgroup_procs_write(of
, buf
, nbytes
, off
, true);
2602 static ssize_t
cgroup_release_agent_write(struct kernfs_open_file
*of
,
2603 char *buf
, size_t nbytes
, loff_t off
)
2605 struct cgroup
*cgrp
;
2607 BUILD_BUG_ON(sizeof(cgrp
->root
->release_agent_path
) < PATH_MAX
);
2609 cgrp
= cgroup_kn_lock_live(of
->kn
);
2612 spin_lock(&release_agent_path_lock
);
2613 strlcpy(cgrp
->root
->release_agent_path
, strstrip(buf
),
2614 sizeof(cgrp
->root
->release_agent_path
));
2615 spin_unlock(&release_agent_path_lock
);
2616 cgroup_kn_unlock(of
->kn
);
2620 static int cgroup_release_agent_show(struct seq_file
*seq
, void *v
)
2622 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2624 spin_lock(&release_agent_path_lock
);
2625 seq_puts(seq
, cgrp
->root
->release_agent_path
);
2626 spin_unlock(&release_agent_path_lock
);
2627 seq_putc(seq
, '\n');
2631 static int cgroup_sane_behavior_show(struct seq_file
*seq
, void *v
)
2633 seq_puts(seq
, "0\n");
2637 static void cgroup_print_ss_mask(struct seq_file
*seq
, unsigned long ss_mask
)
2639 struct cgroup_subsys
*ss
;
2640 bool printed
= false;
2643 for_each_subsys_which(ss
, ssid
, &ss_mask
) {
2646 seq_printf(seq
, "%s", ss
->name
);
2650 seq_putc(seq
, '\n');
2653 /* show controllers which are currently attached to the default hierarchy */
2654 static int cgroup_root_controllers_show(struct seq_file
*seq
, void *v
)
2656 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2658 cgroup_print_ss_mask(seq
, cgrp
->root
->subsys_mask
&
2659 ~cgrp_dfl_root_inhibit_ss_mask
);
2663 /* show controllers which are enabled from the parent */
2664 static int cgroup_controllers_show(struct seq_file
*seq
, void *v
)
2666 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2668 cgroup_print_ss_mask(seq
, cgroup_parent(cgrp
)->subtree_control
);
2672 /* show controllers which are enabled for a given cgroup's children */
2673 static int cgroup_subtree_control_show(struct seq_file
*seq
, void *v
)
2675 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2677 cgroup_print_ss_mask(seq
, cgrp
->subtree_control
);
2682 * cgroup_update_dfl_csses - update css assoc of a subtree in default hierarchy
2683 * @cgrp: root of the subtree to update csses for
2685 * @cgrp's child_subsys_mask has changed and its subtree's (self excluded)
2686 * css associations need to be updated accordingly. This function looks up
2687 * all css_sets which are attached to the subtree, creates the matching
2688 * updated css_sets and migrates the tasks to the new ones.
2690 static int cgroup_update_dfl_csses(struct cgroup
*cgrp
)
2692 LIST_HEAD(preloaded_csets
);
2693 struct cgroup_subsys_state
*css
;
2694 struct css_set
*src_cset
;
2697 lockdep_assert_held(&cgroup_mutex
);
2699 /* look up all csses currently attached to @cgrp's subtree */
2700 down_read(&css_set_rwsem
);
2701 css_for_each_descendant_pre(css
, cgroup_css(cgrp
, NULL
)) {
2702 struct cgrp_cset_link
*link
;
2704 /* self is not affected by child_subsys_mask change */
2705 if (css
->cgroup
== cgrp
)
2708 list_for_each_entry(link
, &css
->cgroup
->cset_links
, cset_link
)
2709 cgroup_migrate_add_src(link
->cset
, cgrp
,
2712 up_read(&css_set_rwsem
);
2714 /* NULL dst indicates self on default hierarchy */
2715 ret
= cgroup_migrate_prepare_dst(NULL
, &preloaded_csets
);
2719 list_for_each_entry(src_cset
, &preloaded_csets
, mg_preload_node
) {
2720 struct task_struct
*last_task
= NULL
, *task
;
2722 /* src_csets precede dst_csets, break on the first dst_cset */
2723 if (!src_cset
->mg_src_cgrp
)
2727 * All tasks in src_cset need to be migrated to the
2728 * matching dst_cset. Empty it process by process. We
2729 * walk tasks but migrate processes. The leader might even
2730 * belong to a different cset but such src_cset would also
2731 * be among the target src_csets because the default
2732 * hierarchy enforces per-process membership.
2735 down_read(&css_set_rwsem
);
2736 task
= list_first_entry_or_null(&src_cset
->tasks
,
2737 struct task_struct
, cg_list
);
2739 task
= task
->group_leader
;
2740 WARN_ON_ONCE(!task_css_set(task
)->mg_src_cgrp
);
2741 get_task_struct(task
);
2743 up_read(&css_set_rwsem
);
2748 /* guard against possible infinite loop */
2749 if (WARN(last_task
== task
,
2750 "cgroup: update_dfl_csses failed to make progress, aborting in inconsistent state\n"))
2754 threadgroup_lock(task
);
2755 /* raced against de_thread() from another thread? */
2756 if (!thread_group_leader(task
)) {
2757 threadgroup_unlock(task
);
2758 put_task_struct(task
);
2762 ret
= cgroup_migrate(src_cset
->dfl_cgrp
, task
, true);
2764 threadgroup_unlock(task
);
2765 put_task_struct(task
);
2767 if (WARN(ret
, "cgroup: failed to update controllers for the default hierarchy (%d), further operations may crash or hang\n", ret
))
2773 cgroup_migrate_finish(&preloaded_csets
);
2777 /* change the enabled child controllers for a cgroup in the default hierarchy */
2778 static ssize_t
cgroup_subtree_control_write(struct kernfs_open_file
*of
,
2779 char *buf
, size_t nbytes
,
2782 unsigned long enable
= 0, disable
= 0;
2783 unsigned long css_enable
, css_disable
, old_sc
, new_sc
, old_ss
, new_ss
;
2784 struct cgroup
*cgrp
, *child
;
2785 struct cgroup_subsys
*ss
;
2790 * Parse input - space separated list of subsystem names prefixed
2791 * with either + or -.
2793 buf
= strstrip(buf
);
2794 while ((tok
= strsep(&buf
, " "))) {
2795 unsigned long tmp_ss_mask
= ~cgrp_dfl_root_inhibit_ss_mask
;
2799 for_each_subsys_which(ss
, ssid
, &tmp_ss_mask
) {
2800 if (ss
->disabled
|| strcmp(tok
+ 1, ss
->name
))
2804 enable
|= 1 << ssid
;
2805 disable
&= ~(1 << ssid
);
2806 } else if (*tok
== '-') {
2807 disable
|= 1 << ssid
;
2808 enable
&= ~(1 << ssid
);
2814 if (ssid
== CGROUP_SUBSYS_COUNT
)
2818 cgrp
= cgroup_kn_lock_live(of
->kn
);
2822 for_each_subsys(ss
, ssid
) {
2823 if (enable
& (1 << ssid
)) {
2824 if (cgrp
->subtree_control
& (1 << ssid
)) {
2825 enable
&= ~(1 << ssid
);
2829 /* unavailable or not enabled on the parent? */
2830 if (!(cgrp_dfl_root
.subsys_mask
& (1 << ssid
)) ||
2831 (cgroup_parent(cgrp
) &&
2832 !(cgroup_parent(cgrp
)->subtree_control
& (1 << ssid
)))) {
2836 } else if (disable
& (1 << ssid
)) {
2837 if (!(cgrp
->subtree_control
& (1 << ssid
))) {
2838 disable
&= ~(1 << ssid
);
2842 /* a child has it enabled? */
2843 cgroup_for_each_live_child(child
, cgrp
) {
2844 if (child
->subtree_control
& (1 << ssid
)) {
2852 if (!enable
&& !disable
) {
2858 * Except for the root, subtree_control must be zero for a cgroup
2859 * with tasks so that child cgroups don't compete against tasks.
2861 if (enable
&& cgroup_parent(cgrp
) && !list_empty(&cgrp
->cset_links
)) {
2867 * Update subsys masks and calculate what needs to be done. More
2868 * subsystems than specified may need to be enabled or disabled
2869 * depending on subsystem dependencies.
2871 old_sc
= cgrp
->subtree_control
;
2872 old_ss
= cgrp
->child_subsys_mask
;
2873 new_sc
= (old_sc
| enable
) & ~disable
;
2874 new_ss
= cgroup_calc_child_subsys_mask(cgrp
, new_sc
);
2876 css_enable
= ~old_ss
& new_ss
;
2877 css_disable
= old_ss
& ~new_ss
;
2878 enable
|= css_enable
;
2879 disable
|= css_disable
;
2882 * Because css offlining is asynchronous, userland might try to
2883 * re-enable the same controller while the previous instance is
2884 * still around. In such cases, wait till it's gone using
2887 for_each_subsys_which(ss
, ssid
, &css_enable
) {
2888 cgroup_for_each_live_child(child
, cgrp
) {
2891 if (!cgroup_css(child
, ss
))
2895 prepare_to_wait(&child
->offline_waitq
, &wait
,
2896 TASK_UNINTERRUPTIBLE
);
2897 cgroup_kn_unlock(of
->kn
);
2899 finish_wait(&child
->offline_waitq
, &wait
);
2902 return restart_syscall();
2906 cgrp
->subtree_control
= new_sc
;
2907 cgrp
->child_subsys_mask
= new_ss
;
2910 * Create new csses or make the existing ones visible. A css is
2911 * created invisible if it's being implicitly enabled through
2912 * dependency. An invisible css is made visible when the userland
2913 * explicitly enables it.
2915 for_each_subsys(ss
, ssid
) {
2916 if (!(enable
& (1 << ssid
)))
2919 cgroup_for_each_live_child(child
, cgrp
) {
2920 if (css_enable
& (1 << ssid
))
2921 ret
= create_css(child
, ss
,
2922 cgrp
->subtree_control
& (1 << ssid
));
2924 ret
= cgroup_populate_dir(child
, 1 << ssid
);
2931 * At this point, cgroup_e_css() results reflect the new csses
2932 * making the following cgroup_update_dfl_csses() properly update
2933 * css associations of all tasks in the subtree.
2935 ret
= cgroup_update_dfl_csses(cgrp
);
2940 * All tasks are migrated out of disabled csses. Kill or hide
2941 * them. A css is hidden when the userland requests it to be
2942 * disabled while other subsystems are still depending on it. The
2943 * css must not actively control resources and be in the vanilla
2944 * state if it's made visible again later. Controllers which may
2945 * be depended upon should provide ->css_reset() for this purpose.
2947 for_each_subsys(ss
, ssid
) {
2948 if (!(disable
& (1 << ssid
)))
2951 cgroup_for_each_live_child(child
, cgrp
) {
2952 struct cgroup_subsys_state
*css
= cgroup_css(child
, ss
);
2954 if (css_disable
& (1 << ssid
)) {
2957 cgroup_clear_dir(child
, 1 << ssid
);
2965 * The effective csses of all the descendants (excluding @cgrp) may
2966 * have changed. Subsystems can optionally subscribe to this event
2967 * by implementing ->css_e_css_changed() which is invoked if any of
2968 * the effective csses seen from the css's cgroup may have changed.
2970 for_each_subsys(ss
, ssid
) {
2971 struct cgroup_subsys_state
*this_css
= cgroup_css(cgrp
, ss
);
2972 struct cgroup_subsys_state
*css
;
2974 if (!ss
->css_e_css_changed
|| !this_css
)
2977 css_for_each_descendant_pre(css
, this_css
)
2978 if (css
!= this_css
)
2979 ss
->css_e_css_changed(css
);
2982 kernfs_activate(cgrp
->kn
);
2985 cgroup_kn_unlock(of
->kn
);
2986 return ret
?: nbytes
;
2989 cgrp
->subtree_control
= old_sc
;
2990 cgrp
->child_subsys_mask
= old_ss
;
2992 for_each_subsys(ss
, ssid
) {
2993 if (!(enable
& (1 << ssid
)))
2996 cgroup_for_each_live_child(child
, cgrp
) {
2997 struct cgroup_subsys_state
*css
= cgroup_css(child
, ss
);
3002 if (css_enable
& (1 << ssid
))
3005 cgroup_clear_dir(child
, 1 << ssid
);
3011 static int cgroup_populated_show(struct seq_file
*seq
, void *v
)
3013 seq_printf(seq
, "%d\n", (bool)seq_css(seq
)->cgroup
->populated_cnt
);
3017 static ssize_t
cgroup_file_write(struct kernfs_open_file
*of
, char *buf
,
3018 size_t nbytes
, loff_t off
)
3020 struct cgroup
*cgrp
= of
->kn
->parent
->priv
;
3021 struct cftype
*cft
= of
->kn
->priv
;
3022 struct cgroup_subsys_state
*css
;
3026 return cft
->write(of
, buf
, nbytes
, off
);
3029 * kernfs guarantees that a file isn't deleted with operations in
3030 * flight, which means that the matching css is and stays alive and
3031 * doesn't need to be pinned. The RCU locking is not necessary
3032 * either. It's just for the convenience of using cgroup_css().
3035 css
= cgroup_css(cgrp
, cft
->ss
);
3038 if (cft
->write_u64
) {
3039 unsigned long long v
;
3040 ret
= kstrtoull(buf
, 0, &v
);
3042 ret
= cft
->write_u64(css
, cft
, v
);
3043 } else if (cft
->write_s64
) {
3045 ret
= kstrtoll(buf
, 0, &v
);
3047 ret
= cft
->write_s64(css
, cft
, v
);
3052 return ret
?: nbytes
;
3055 static void *cgroup_seqfile_start(struct seq_file
*seq
, loff_t
*ppos
)
3057 return seq_cft(seq
)->seq_start(seq
, ppos
);
3060 static void *cgroup_seqfile_next(struct seq_file
*seq
, void *v
, loff_t
*ppos
)
3062 return seq_cft(seq
)->seq_next(seq
, v
, ppos
);
3065 static void cgroup_seqfile_stop(struct seq_file
*seq
, void *v
)
3067 seq_cft(seq
)->seq_stop(seq
, v
);
3070 static int cgroup_seqfile_show(struct seq_file
*m
, void *arg
)
3072 struct cftype
*cft
= seq_cft(m
);
3073 struct cgroup_subsys_state
*css
= seq_css(m
);
3076 return cft
->seq_show(m
, arg
);
3079 seq_printf(m
, "%llu\n", cft
->read_u64(css
, cft
));
3080 else if (cft
->read_s64
)
3081 seq_printf(m
, "%lld\n", cft
->read_s64(css
, cft
));
3087 static struct kernfs_ops cgroup_kf_single_ops
= {
3088 .atomic_write_len
= PAGE_SIZE
,
3089 .write
= cgroup_file_write
,
3090 .seq_show
= cgroup_seqfile_show
,
3093 static struct kernfs_ops cgroup_kf_ops
= {
3094 .atomic_write_len
= PAGE_SIZE
,
3095 .write
= cgroup_file_write
,
3096 .seq_start
= cgroup_seqfile_start
,
3097 .seq_next
= cgroup_seqfile_next
,
3098 .seq_stop
= cgroup_seqfile_stop
,
3099 .seq_show
= cgroup_seqfile_show
,
3103 * cgroup_rename - Only allow simple rename of directories in place.
3105 static int cgroup_rename(struct kernfs_node
*kn
, struct kernfs_node
*new_parent
,
3106 const char *new_name_str
)
3108 struct cgroup
*cgrp
= kn
->priv
;
3111 if (kernfs_type(kn
) != KERNFS_DIR
)
3113 if (kn
->parent
!= new_parent
)
3117 * This isn't a proper migration and its usefulness is very
3118 * limited. Disallow on the default hierarchy.
3120 if (cgroup_on_dfl(cgrp
))
3124 * We're gonna grab cgroup_mutex which nests outside kernfs
3125 * active_ref. kernfs_rename() doesn't require active_ref
3126 * protection. Break them before grabbing cgroup_mutex.
3128 kernfs_break_active_protection(new_parent
);
3129 kernfs_break_active_protection(kn
);
3131 mutex_lock(&cgroup_mutex
);
3133 ret
= kernfs_rename(kn
, new_parent
, new_name_str
);
3135 mutex_unlock(&cgroup_mutex
);
3137 kernfs_unbreak_active_protection(kn
);
3138 kernfs_unbreak_active_protection(new_parent
);
3142 /* set uid and gid of cgroup dirs and files to that of the creator */
3143 static int cgroup_kn_set_ugid(struct kernfs_node
*kn
)
3145 struct iattr iattr
= { .ia_valid
= ATTR_UID
| ATTR_GID
,
3146 .ia_uid
= current_fsuid(),
3147 .ia_gid
= current_fsgid(), };
3149 if (uid_eq(iattr
.ia_uid
, GLOBAL_ROOT_UID
) &&
3150 gid_eq(iattr
.ia_gid
, GLOBAL_ROOT_GID
))
3153 return kernfs_setattr(kn
, &iattr
);
3156 static int cgroup_add_file(struct cgroup
*cgrp
, struct cftype
*cft
)
3158 char name
[CGROUP_FILE_NAME_MAX
];
3159 struct kernfs_node
*kn
;
3160 struct lock_class_key
*key
= NULL
;
3163 #ifdef CONFIG_DEBUG_LOCK_ALLOC
3164 key
= &cft
->lockdep_key
;
3166 kn
= __kernfs_create_file(cgrp
->kn
, cgroup_file_name(cgrp
, cft
, name
),
3167 cgroup_file_mode(cft
), 0, cft
->kf_ops
, cft
,
3172 ret
= cgroup_kn_set_ugid(kn
);
3178 if (cft
->write
== cgroup_procs_write
)
3179 cgrp
->procs_kn
= kn
;
3180 else if (cft
->seq_show
== cgroup_populated_show
)
3181 cgrp
->populated_kn
= kn
;
3186 * cgroup_addrm_files - add or remove files to a cgroup directory
3187 * @cgrp: the target cgroup
3188 * @cfts: array of cftypes to be added
3189 * @is_add: whether to add or remove
3191 * Depending on @is_add, add or remove files defined by @cfts on @cgrp.
3192 * For removals, this function never fails. If addition fails, this
3193 * function doesn't remove files already added. The caller is responsible
3196 static int cgroup_addrm_files(struct cgroup
*cgrp
, struct cftype cfts
[],
3202 lockdep_assert_held(&cgroup_mutex
);
3204 for (cft
= cfts
; cft
->name
[0] != '\0'; cft
++) {
3205 /* does cft->flags tell us to skip this file on @cgrp? */
3206 if ((cft
->flags
& __CFTYPE_ONLY_ON_DFL
) && !cgroup_on_dfl(cgrp
))
3208 if ((cft
->flags
& __CFTYPE_NOT_ON_DFL
) && cgroup_on_dfl(cgrp
))
3210 if ((cft
->flags
& CFTYPE_NOT_ON_ROOT
) && !cgroup_parent(cgrp
))
3212 if ((cft
->flags
& CFTYPE_ONLY_ON_ROOT
) && cgroup_parent(cgrp
))
3216 ret
= cgroup_add_file(cgrp
, cft
);
3218 pr_warn("%s: failed to add %s, err=%d\n",
3219 __func__
, cft
->name
, ret
);
3223 cgroup_rm_file(cgrp
, cft
);
3229 static int cgroup_apply_cftypes(struct cftype
*cfts
, bool is_add
)
3232 struct cgroup_subsys
*ss
= cfts
[0].ss
;
3233 struct cgroup
*root
= &ss
->root
->cgrp
;
3234 struct cgroup_subsys_state
*css
;
3237 lockdep_assert_held(&cgroup_mutex
);
3239 /* add/rm files for all cgroups created before */
3240 css_for_each_descendant_pre(css
, cgroup_css(root
, ss
)) {
3241 struct cgroup
*cgrp
= css
->cgroup
;
3243 if (cgroup_is_dead(cgrp
))
3246 ret
= cgroup_addrm_files(cgrp
, cfts
, is_add
);
3252 kernfs_activate(root
->kn
);
3256 static void cgroup_exit_cftypes(struct cftype
*cfts
)
3260 for (cft
= cfts
; cft
->name
[0] != '\0'; cft
++) {
3261 /* free copy for custom atomic_write_len, see init_cftypes() */
3262 if (cft
->max_write_len
&& cft
->max_write_len
!= PAGE_SIZE
)
3267 /* revert flags set by cgroup core while adding @cfts */
3268 cft
->flags
&= ~(__CFTYPE_ONLY_ON_DFL
| __CFTYPE_NOT_ON_DFL
);
3272 static int cgroup_init_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3276 for (cft
= cfts
; cft
->name
[0] != '\0'; cft
++) {
3277 struct kernfs_ops
*kf_ops
;
3279 WARN_ON(cft
->ss
|| cft
->kf_ops
);
3282 kf_ops
= &cgroup_kf_ops
;
3284 kf_ops
= &cgroup_kf_single_ops
;
3287 * Ugh... if @cft wants a custom max_write_len, we need to
3288 * make a copy of kf_ops to set its atomic_write_len.
3290 if (cft
->max_write_len
&& cft
->max_write_len
!= PAGE_SIZE
) {
3291 kf_ops
= kmemdup(kf_ops
, sizeof(*kf_ops
), GFP_KERNEL
);
3293 cgroup_exit_cftypes(cfts
);
3296 kf_ops
->atomic_write_len
= cft
->max_write_len
;
3299 cft
->kf_ops
= kf_ops
;
3306 static int cgroup_rm_cftypes_locked(struct cftype
*cfts
)
3308 lockdep_assert_held(&cgroup_mutex
);
3310 if (!cfts
|| !cfts
[0].ss
)
3313 list_del(&cfts
->node
);
3314 cgroup_apply_cftypes(cfts
, false);
3315 cgroup_exit_cftypes(cfts
);
3320 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
3321 * @cfts: zero-length name terminated array of cftypes
3323 * Unregister @cfts. Files described by @cfts are removed from all
3324 * existing cgroups and all future cgroups won't have them either. This
3325 * function can be called anytime whether @cfts' subsys is attached or not.
3327 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
3330 int cgroup_rm_cftypes(struct cftype
*cfts
)
3334 mutex_lock(&cgroup_mutex
);
3335 ret
= cgroup_rm_cftypes_locked(cfts
);
3336 mutex_unlock(&cgroup_mutex
);
3341 * cgroup_add_cftypes - add an array of cftypes to a subsystem
3342 * @ss: target cgroup subsystem
3343 * @cfts: zero-length name terminated array of cftypes
3345 * Register @cfts to @ss. Files described by @cfts are created for all
3346 * existing cgroups to which @ss is attached and all future cgroups will
3347 * have them too. This function can be called anytime whether @ss is
3350 * Returns 0 on successful registration, -errno on failure. Note that this
3351 * function currently returns 0 as long as @cfts registration is successful
3352 * even if some file creation attempts on existing cgroups fail.
3354 static int cgroup_add_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3361 if (!cfts
|| cfts
[0].name
[0] == '\0')
3364 ret
= cgroup_init_cftypes(ss
, cfts
);
3368 mutex_lock(&cgroup_mutex
);
3370 list_add_tail(&cfts
->node
, &ss
->cfts
);
3371 ret
= cgroup_apply_cftypes(cfts
, true);
3373 cgroup_rm_cftypes_locked(cfts
);
3375 mutex_unlock(&cgroup_mutex
);
3380 * cgroup_add_dfl_cftypes - add an array of cftypes for default hierarchy
3381 * @ss: target cgroup subsystem
3382 * @cfts: zero-length name terminated array of cftypes
3384 * Similar to cgroup_add_cftypes() but the added files are only used for
3385 * the default hierarchy.
3387 int cgroup_add_dfl_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3391 for (cft
= cfts
; cft
&& cft
->name
[0] != '\0'; cft
++)
3392 cft
->flags
|= __CFTYPE_ONLY_ON_DFL
;
3393 return cgroup_add_cftypes(ss
, cfts
);
3397 * cgroup_add_legacy_cftypes - add an array of cftypes for legacy hierarchies
3398 * @ss: target cgroup subsystem
3399 * @cfts: zero-length name terminated array of cftypes
3401 * Similar to cgroup_add_cftypes() but the added files are only used for
3402 * the legacy hierarchies.
3404 int cgroup_add_legacy_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3409 * If legacy_flies_on_dfl, we want to show the legacy files on the
3410 * dfl hierarchy but iff the target subsystem hasn't been updated
3411 * for the dfl hierarchy yet.
3413 if (!cgroup_legacy_files_on_dfl
||
3414 ss
->dfl_cftypes
!= ss
->legacy_cftypes
) {
3415 for (cft
= cfts
; cft
&& cft
->name
[0] != '\0'; cft
++)
3416 cft
->flags
|= __CFTYPE_NOT_ON_DFL
;
3419 return cgroup_add_cftypes(ss
, cfts
);
3423 * cgroup_task_count - count the number of tasks in a cgroup.
3424 * @cgrp: the cgroup in question
3426 * Return the number of tasks in the cgroup.
3428 static int cgroup_task_count(const struct cgroup
*cgrp
)
3431 struct cgrp_cset_link
*link
;
3433 down_read(&css_set_rwsem
);
3434 list_for_each_entry(link
, &cgrp
->cset_links
, cset_link
)
3435 count
+= atomic_read(&link
->cset
->refcount
);
3436 up_read(&css_set_rwsem
);
3441 * css_next_child - find the next child of a given css
3442 * @pos: the current position (%NULL to initiate traversal)
3443 * @parent: css whose children to walk
3445 * This function returns the next child of @parent and should be called
3446 * under either cgroup_mutex or RCU read lock. The only requirement is
3447 * that @parent and @pos are accessible. The next sibling is guaranteed to
3448 * be returned regardless of their states.
3450 * If a subsystem synchronizes ->css_online() and the start of iteration, a
3451 * css which finished ->css_online() is guaranteed to be visible in the
3452 * future iterations and will stay visible until the last reference is put.
3453 * A css which hasn't finished ->css_online() or already finished
3454 * ->css_offline() may show up during traversal. It's each subsystem's
3455 * responsibility to synchronize against on/offlining.
3457 struct cgroup_subsys_state
*css_next_child(struct cgroup_subsys_state
*pos
,
3458 struct cgroup_subsys_state
*parent
)
3460 struct cgroup_subsys_state
*next
;
3462 cgroup_assert_mutex_or_rcu_locked();
3465 * @pos could already have been unlinked from the sibling list.
3466 * Once a cgroup is removed, its ->sibling.next is no longer
3467 * updated when its next sibling changes. CSS_RELEASED is set when
3468 * @pos is taken off list, at which time its next pointer is valid,
3469 * and, as releases are serialized, the one pointed to by the next
3470 * pointer is guaranteed to not have started release yet. This
3471 * implies that if we observe !CSS_RELEASED on @pos in this RCU
3472 * critical section, the one pointed to by its next pointer is
3473 * guaranteed to not have finished its RCU grace period even if we
3474 * have dropped rcu_read_lock() inbetween iterations.
3476 * If @pos has CSS_RELEASED set, its next pointer can't be
3477 * dereferenced; however, as each css is given a monotonically
3478 * increasing unique serial number and always appended to the
3479 * sibling list, the next one can be found by walking the parent's
3480 * children until the first css with higher serial number than
3481 * @pos's. While this path can be slower, it happens iff iteration
3482 * races against release and the race window is very small.
3485 next
= list_entry_rcu(parent
->children
.next
, struct cgroup_subsys_state
, sibling
);
3486 } else if (likely(!(pos
->flags
& CSS_RELEASED
))) {
3487 next
= list_entry_rcu(pos
->sibling
.next
, struct cgroup_subsys_state
, sibling
);
3489 list_for_each_entry_rcu(next
, &parent
->children
, sibling
)
3490 if (next
->serial_nr
> pos
->serial_nr
)
3495 * @next, if not pointing to the head, can be dereferenced and is
3498 if (&next
->sibling
!= &parent
->children
)
3504 * css_next_descendant_pre - find the next descendant for pre-order walk
3505 * @pos: the current position (%NULL to initiate traversal)
3506 * @root: css whose descendants to walk
3508 * To be used by css_for_each_descendant_pre(). Find the next descendant
3509 * to visit for pre-order traversal of @root's descendants. @root is
3510 * included in the iteration and the first node to be visited.
3512 * While this function requires cgroup_mutex or RCU read locking, it
3513 * doesn't require the whole traversal to be contained in a single critical
3514 * section. This function will return the correct next descendant as long
3515 * as both @pos and @root are accessible and @pos is a descendant of @root.
3517 * If a subsystem synchronizes ->css_online() and the start of iteration, a
3518 * css which finished ->css_online() is guaranteed to be visible in the
3519 * future iterations and will stay visible until the last reference is put.
3520 * A css which hasn't finished ->css_online() or already finished
3521 * ->css_offline() may show up during traversal. It's each subsystem's
3522 * responsibility to synchronize against on/offlining.
3524 struct cgroup_subsys_state
*
3525 css_next_descendant_pre(struct cgroup_subsys_state
*pos
,
3526 struct cgroup_subsys_state
*root
)
3528 struct cgroup_subsys_state
*next
;
3530 cgroup_assert_mutex_or_rcu_locked();
3532 /* if first iteration, visit @root */
3536 /* visit the first child if exists */
3537 next
= css_next_child(NULL
, pos
);
3541 /* no child, visit my or the closest ancestor's next sibling */
3542 while (pos
!= root
) {
3543 next
= css_next_child(pos
, pos
->parent
);
3553 * css_rightmost_descendant - return the rightmost descendant of a css
3554 * @pos: css of interest
3556 * Return the rightmost descendant of @pos. If there's no descendant, @pos
3557 * is returned. This can be used during pre-order traversal to skip
3560 * While this function requires cgroup_mutex or RCU read locking, it
3561 * doesn't require the whole traversal to be contained in a single critical
3562 * section. This function will return the correct rightmost descendant as
3563 * long as @pos is accessible.
3565 struct cgroup_subsys_state
*
3566 css_rightmost_descendant(struct cgroup_subsys_state
*pos
)
3568 struct cgroup_subsys_state
*last
, *tmp
;
3570 cgroup_assert_mutex_or_rcu_locked();
3574 /* ->prev isn't RCU safe, walk ->next till the end */
3576 css_for_each_child(tmp
, last
)
3583 static struct cgroup_subsys_state
*
3584 css_leftmost_descendant(struct cgroup_subsys_state
*pos
)
3586 struct cgroup_subsys_state
*last
;
3590 pos
= css_next_child(NULL
, pos
);
3597 * css_next_descendant_post - find the next descendant for post-order walk
3598 * @pos: the current position (%NULL to initiate traversal)
3599 * @root: css whose descendants to walk
3601 * To be used by css_for_each_descendant_post(). Find the next descendant
3602 * to visit for post-order traversal of @root's descendants. @root is
3603 * included in the iteration and the last node to be visited.
3605 * While this function requires cgroup_mutex or RCU read locking, it
3606 * doesn't require the whole traversal to be contained in a single critical
3607 * section. This function will return the correct next descendant as long
3608 * as both @pos and @cgroup are accessible and @pos is a descendant of
3611 * If a subsystem synchronizes ->css_online() and the start of iteration, a
3612 * css which finished ->css_online() is guaranteed to be visible in the
3613 * future iterations and will stay visible until the last reference is put.
3614 * A css which hasn't finished ->css_online() or already finished
3615 * ->css_offline() may show up during traversal. It's each subsystem's
3616 * responsibility to synchronize against on/offlining.
3618 struct cgroup_subsys_state
*
3619 css_next_descendant_post(struct cgroup_subsys_state
*pos
,
3620 struct cgroup_subsys_state
*root
)
3622 struct cgroup_subsys_state
*next
;
3624 cgroup_assert_mutex_or_rcu_locked();
3626 /* if first iteration, visit leftmost descendant which may be @root */
3628 return css_leftmost_descendant(root
);
3630 /* if we visited @root, we're done */
3634 /* if there's an unvisited sibling, visit its leftmost descendant */
3635 next
= css_next_child(pos
, pos
->parent
);
3637 return css_leftmost_descendant(next
);
3639 /* no sibling left, visit parent */
3644 * css_has_online_children - does a css have online children
3645 * @css: the target css
3647 * Returns %true if @css has any online children; otherwise, %false. This
3648 * function can be called from any context but the caller is responsible
3649 * for synchronizing against on/offlining as necessary.
3651 bool css_has_online_children(struct cgroup_subsys_state
*css
)
3653 struct cgroup_subsys_state
*child
;
3657 css_for_each_child(child
, css
) {
3658 if (child
->flags
& CSS_ONLINE
) {
3668 * css_advance_task_iter - advance a task itererator to the next css_set
3669 * @it: the iterator to advance
3671 * Advance @it to the next css_set to walk.
3673 static void css_advance_task_iter(struct css_task_iter
*it
)
3675 struct list_head
*l
= it
->cset_pos
;
3676 struct cgrp_cset_link
*link
;
3677 struct css_set
*cset
;
3679 /* Advance to the next non-empty css_set */
3682 if (l
== it
->cset_head
) {
3683 it
->cset_pos
= NULL
;
3688 cset
= container_of(l
, struct css_set
,
3689 e_cset_node
[it
->ss
->id
]);
3691 link
= list_entry(l
, struct cgrp_cset_link
, cset_link
);
3694 } while (list_empty(&cset
->tasks
) && list_empty(&cset
->mg_tasks
));
3698 if (!list_empty(&cset
->tasks
))
3699 it
->task_pos
= cset
->tasks
.next
;
3701 it
->task_pos
= cset
->mg_tasks
.next
;
3703 it
->tasks_head
= &cset
->tasks
;
3704 it
->mg_tasks_head
= &cset
->mg_tasks
;
3708 * css_task_iter_start - initiate task iteration
3709 * @css: the css to walk tasks of
3710 * @it: the task iterator to use
3712 * Initiate iteration through the tasks of @css. The caller can call
3713 * css_task_iter_next() to walk through the tasks until the function
3714 * returns NULL. On completion of iteration, css_task_iter_end() must be
3717 * Note that this function acquires a lock which is released when the
3718 * iteration finishes. The caller can't sleep while iteration is in
3721 void css_task_iter_start(struct cgroup_subsys_state
*css
,
3722 struct css_task_iter
*it
)
3723 __acquires(css_set_rwsem
)
3725 /* no one should try to iterate before mounting cgroups */
3726 WARN_ON_ONCE(!use_task_css_set_links
);
3728 down_read(&css_set_rwsem
);
3733 it
->cset_pos
= &css
->cgroup
->e_csets
[css
->ss
->id
];
3735 it
->cset_pos
= &css
->cgroup
->cset_links
;
3737 it
->cset_head
= it
->cset_pos
;
3739 css_advance_task_iter(it
);
3743 * css_task_iter_next - return the next task for the iterator
3744 * @it: the task iterator being iterated
3746 * The "next" function for task iteration. @it should have been
3747 * initialized via css_task_iter_start(). Returns NULL when the iteration
3750 struct task_struct
*css_task_iter_next(struct css_task_iter
*it
)
3752 struct task_struct
*res
;
3753 struct list_head
*l
= it
->task_pos
;
3755 /* If the iterator cg is NULL, we have no tasks */
3758 res
= list_entry(l
, struct task_struct
, cg_list
);
3761 * Advance iterator to find next entry. cset->tasks is consumed
3762 * first and then ->mg_tasks. After ->mg_tasks, we move onto the
3767 if (l
== it
->tasks_head
)
3768 l
= it
->mg_tasks_head
->next
;
3770 if (l
== it
->mg_tasks_head
)
3771 css_advance_task_iter(it
);
3779 * css_task_iter_end - finish task iteration
3780 * @it: the task iterator to finish
3782 * Finish task iteration started by css_task_iter_start().
3784 void css_task_iter_end(struct css_task_iter
*it
)
3785 __releases(css_set_rwsem
)
3787 up_read(&css_set_rwsem
);
3791 * cgroup_trasnsfer_tasks - move tasks from one cgroup to another
3792 * @to: cgroup to which the tasks will be moved
3793 * @from: cgroup in which the tasks currently reside
3795 * Locking rules between cgroup_post_fork() and the migration path
3796 * guarantee that, if a task is forking while being migrated, the new child
3797 * is guaranteed to be either visible in the source cgroup after the
3798 * parent's migration is complete or put into the target cgroup. No task
3799 * can slip out of migration through forking.
3801 int cgroup_transfer_tasks(struct cgroup
*to
, struct cgroup
*from
)
3803 LIST_HEAD(preloaded_csets
);
3804 struct cgrp_cset_link
*link
;
3805 struct css_task_iter it
;
3806 struct task_struct
*task
;
3809 mutex_lock(&cgroup_mutex
);
3811 /* all tasks in @from are being moved, all csets are source */
3812 down_read(&css_set_rwsem
);
3813 list_for_each_entry(link
, &from
->cset_links
, cset_link
)
3814 cgroup_migrate_add_src(link
->cset
, to
, &preloaded_csets
);
3815 up_read(&css_set_rwsem
);
3817 ret
= cgroup_migrate_prepare_dst(to
, &preloaded_csets
);
3822 * Migrate tasks one-by-one until @form is empty. This fails iff
3823 * ->can_attach() fails.
3826 css_task_iter_start(&from
->self
, &it
);
3827 task
= css_task_iter_next(&it
);
3829 get_task_struct(task
);
3830 css_task_iter_end(&it
);
3833 ret
= cgroup_migrate(to
, task
, false);
3834 put_task_struct(task
);
3836 } while (task
&& !ret
);
3838 cgroup_migrate_finish(&preloaded_csets
);
3839 mutex_unlock(&cgroup_mutex
);
3844 * Stuff for reading the 'tasks'/'procs' files.
3846 * Reading this file can return large amounts of data if a cgroup has
3847 * *lots* of attached tasks. So it may need several calls to read(),
3848 * but we cannot guarantee that the information we produce is correct
3849 * unless we produce it entirely atomically.
3853 /* which pidlist file are we talking about? */
3854 enum cgroup_filetype
{
3860 * A pidlist is a list of pids that virtually represents the contents of one
3861 * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
3862 * a pair (one each for procs, tasks) for each pid namespace that's relevant
3865 struct cgroup_pidlist
{
3867 * used to find which pidlist is wanted. doesn't change as long as
3868 * this particular list stays in the list.
3870 struct { enum cgroup_filetype type
; struct pid_namespace
*ns
; } key
;
3873 /* how many elements the above list has */
3875 /* each of these stored in a list by its cgroup */
3876 struct list_head links
;
3877 /* pointer to the cgroup we belong to, for list removal purposes */
3878 struct cgroup
*owner
;
3879 /* for delayed destruction */
3880 struct delayed_work destroy_dwork
;
3884 * The following two functions "fix" the issue where there are more pids
3885 * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
3886 * TODO: replace with a kernel-wide solution to this problem
3888 #define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
3889 static void *pidlist_allocate(int count
)
3891 if (PIDLIST_TOO_LARGE(count
))
3892 return vmalloc(count
* sizeof(pid_t
));
3894 return kmalloc(count
* sizeof(pid_t
), GFP_KERNEL
);
3897 static void pidlist_free(void *p
)
3903 * Used to destroy all pidlists lingering waiting for destroy timer. None
3904 * should be left afterwards.
3906 static void cgroup_pidlist_destroy_all(struct cgroup
*cgrp
)
3908 struct cgroup_pidlist
*l
, *tmp_l
;
3910 mutex_lock(&cgrp
->pidlist_mutex
);
3911 list_for_each_entry_safe(l
, tmp_l
, &cgrp
->pidlists
, links
)
3912 mod_delayed_work(cgroup_pidlist_destroy_wq
, &l
->destroy_dwork
, 0);
3913 mutex_unlock(&cgrp
->pidlist_mutex
);
3915 flush_workqueue(cgroup_pidlist_destroy_wq
);
3916 BUG_ON(!list_empty(&cgrp
->pidlists
));
3919 static void cgroup_pidlist_destroy_work_fn(struct work_struct
*work
)
3921 struct delayed_work
*dwork
= to_delayed_work(work
);
3922 struct cgroup_pidlist
*l
= container_of(dwork
, struct cgroup_pidlist
,
3924 struct cgroup_pidlist
*tofree
= NULL
;
3926 mutex_lock(&l
->owner
->pidlist_mutex
);
3929 * Destroy iff we didn't get queued again. The state won't change
3930 * as destroy_dwork can only be queued while locked.
3932 if (!delayed_work_pending(dwork
)) {
3933 list_del(&l
->links
);
3934 pidlist_free(l
->list
);
3935 put_pid_ns(l
->key
.ns
);
3939 mutex_unlock(&l
->owner
->pidlist_mutex
);
3944 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
3945 * Returns the number of unique elements.
3947 static int pidlist_uniq(pid_t
*list
, int length
)
3952 * we presume the 0th element is unique, so i starts at 1. trivial
3953 * edge cases first; no work needs to be done for either
3955 if (length
== 0 || length
== 1)
3957 /* src and dest walk down the list; dest counts unique elements */
3958 for (src
= 1; src
< length
; src
++) {
3959 /* find next unique element */
3960 while (list
[src
] == list
[src
-1]) {
3965 /* dest always points to where the next unique element goes */
3966 list
[dest
] = list
[src
];
3974 * The two pid files - task and cgroup.procs - guaranteed that the result
3975 * is sorted, which forced this whole pidlist fiasco. As pid order is
3976 * different per namespace, each namespace needs differently sorted list,
3977 * making it impossible to use, for example, single rbtree of member tasks
3978 * sorted by task pointer. As pidlists can be fairly large, allocating one
3979 * per open file is dangerous, so cgroup had to implement shared pool of
3980 * pidlists keyed by cgroup and namespace.
3982 * All this extra complexity was caused by the original implementation
3983 * committing to an entirely unnecessary property. In the long term, we
3984 * want to do away with it. Explicitly scramble sort order if on the
3985 * default hierarchy so that no such expectation exists in the new
3988 * Scrambling is done by swapping every two consecutive bits, which is
3989 * non-identity one-to-one mapping which disturbs sort order sufficiently.
3991 static pid_t
pid_fry(pid_t pid
)
3993 unsigned a
= pid
& 0x55555555;
3994 unsigned b
= pid
& 0xAAAAAAAA;
3996 return (a
<< 1) | (b
>> 1);
3999 static pid_t
cgroup_pid_fry(struct cgroup
*cgrp
, pid_t pid
)
4001 if (cgroup_on_dfl(cgrp
))
4002 return pid_fry(pid
);
4007 static int cmppid(const void *a
, const void *b
)
4009 return *(pid_t
*)a
- *(pid_t
*)b
;
4012 static int fried_cmppid(const void *a
, const void *b
)
4014 return pid_fry(*(pid_t
*)a
) - pid_fry(*(pid_t
*)b
);
4017 static struct cgroup_pidlist
*cgroup_pidlist_find(struct cgroup
*cgrp
,
4018 enum cgroup_filetype type
)
4020 struct cgroup_pidlist
*l
;
4021 /* don't need task_nsproxy() if we're looking at ourself */
4022 struct pid_namespace
*ns
= task_active_pid_ns(current
);
4024 lockdep_assert_held(&cgrp
->pidlist_mutex
);
4026 list_for_each_entry(l
, &cgrp
->pidlists
, links
)
4027 if (l
->key
.type
== type
&& l
->key
.ns
== ns
)
4033 * find the appropriate pidlist for our purpose (given procs vs tasks)
4034 * returns with the lock on that pidlist already held, and takes care
4035 * of the use count, or returns NULL with no locks held if we're out of
4038 static struct cgroup_pidlist
*cgroup_pidlist_find_create(struct cgroup
*cgrp
,
4039 enum cgroup_filetype type
)
4041 struct cgroup_pidlist
*l
;
4043 lockdep_assert_held(&cgrp
->pidlist_mutex
);
4045 l
= cgroup_pidlist_find(cgrp
, type
);
4049 /* entry not found; create a new one */
4050 l
= kzalloc(sizeof(struct cgroup_pidlist
), GFP_KERNEL
);
4054 INIT_DELAYED_WORK(&l
->destroy_dwork
, cgroup_pidlist_destroy_work_fn
);
4056 /* don't need task_nsproxy() if we're looking at ourself */
4057 l
->key
.ns
= get_pid_ns(task_active_pid_ns(current
));
4059 list_add(&l
->links
, &cgrp
->pidlists
);
4064 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
4066 static int pidlist_array_load(struct cgroup
*cgrp
, enum cgroup_filetype type
,
4067 struct cgroup_pidlist
**lp
)
4071 int pid
, n
= 0; /* used for populating the array */
4072 struct css_task_iter it
;
4073 struct task_struct
*tsk
;
4074 struct cgroup_pidlist
*l
;
4076 lockdep_assert_held(&cgrp
->pidlist_mutex
);
4079 * If cgroup gets more users after we read count, we won't have
4080 * enough space - tough. This race is indistinguishable to the
4081 * caller from the case that the additional cgroup users didn't
4082 * show up until sometime later on.
4084 length
= cgroup_task_count(cgrp
);
4085 array
= pidlist_allocate(length
);
4088 /* now, populate the array */
4089 css_task_iter_start(&cgrp
->self
, &it
);
4090 while ((tsk
= css_task_iter_next(&it
))) {
4091 if (unlikely(n
== length
))
4093 /* get tgid or pid for procs or tasks file respectively */
4094 if (type
== CGROUP_FILE_PROCS
)
4095 pid
= task_tgid_vnr(tsk
);
4097 pid
= task_pid_vnr(tsk
);
4098 if (pid
> 0) /* make sure to only use valid results */
4101 css_task_iter_end(&it
);
4103 /* now sort & (if procs) strip out duplicates */
4104 if (cgroup_on_dfl(cgrp
))
4105 sort(array
, length
, sizeof(pid_t
), fried_cmppid
, NULL
);
4107 sort(array
, length
, sizeof(pid_t
), cmppid
, NULL
);
4108 if (type
== CGROUP_FILE_PROCS
)
4109 length
= pidlist_uniq(array
, length
);
4111 l
= cgroup_pidlist_find_create(cgrp
, type
);
4113 pidlist_free(array
);
4117 /* store array, freeing old if necessary */
4118 pidlist_free(l
->list
);
4126 * cgroupstats_build - build and fill cgroupstats
4127 * @stats: cgroupstats to fill information into
4128 * @dentry: A dentry entry belonging to the cgroup for which stats have
4131 * Build and fill cgroupstats so that taskstats can export it to user
4134 int cgroupstats_build(struct cgroupstats
*stats
, struct dentry
*dentry
)
4136 struct kernfs_node
*kn
= kernfs_node_from_dentry(dentry
);
4137 struct cgroup
*cgrp
;
4138 struct css_task_iter it
;
4139 struct task_struct
*tsk
;
4141 /* it should be kernfs_node belonging to cgroupfs and is a directory */
4142 if (dentry
->d_sb
->s_type
!= &cgroup_fs_type
|| !kn
||
4143 kernfs_type(kn
) != KERNFS_DIR
)
4146 mutex_lock(&cgroup_mutex
);
4149 * We aren't being called from kernfs and there's no guarantee on
4150 * @kn->priv's validity. For this and css_tryget_online_from_dir(),
4151 * @kn->priv is RCU safe. Let's do the RCU dancing.
4154 cgrp
= rcu_dereference(kn
->priv
);
4155 if (!cgrp
|| cgroup_is_dead(cgrp
)) {
4157 mutex_unlock(&cgroup_mutex
);
4162 css_task_iter_start(&cgrp
->self
, &it
);
4163 while ((tsk
= css_task_iter_next(&it
))) {
4164 switch (tsk
->state
) {
4166 stats
->nr_running
++;
4168 case TASK_INTERRUPTIBLE
:
4169 stats
->nr_sleeping
++;
4171 case TASK_UNINTERRUPTIBLE
:
4172 stats
->nr_uninterruptible
++;
4175 stats
->nr_stopped
++;
4178 if (delayacct_is_task_waiting_on_io(tsk
))
4179 stats
->nr_io_wait
++;
4183 css_task_iter_end(&it
);
4185 mutex_unlock(&cgroup_mutex
);
4191 * seq_file methods for the tasks/procs files. The seq_file position is the
4192 * next pid to display; the seq_file iterator is a pointer to the pid
4193 * in the cgroup->l->list array.
4196 static void *cgroup_pidlist_start(struct seq_file
*s
, loff_t
*pos
)
4199 * Initially we receive a position value that corresponds to
4200 * one more than the last pid shown (or 0 on the first call or
4201 * after a seek to the start). Use a binary-search to find the
4202 * next pid to display, if any
4204 struct kernfs_open_file
*of
= s
->private;
4205 struct cgroup
*cgrp
= seq_css(s
)->cgroup
;
4206 struct cgroup_pidlist
*l
;
4207 enum cgroup_filetype type
= seq_cft(s
)->private;
4208 int index
= 0, pid
= *pos
;
4211 mutex_lock(&cgrp
->pidlist_mutex
);
4214 * !NULL @of->priv indicates that this isn't the first start()
4215 * after open. If the matching pidlist is around, we can use that.
4216 * Look for it. Note that @of->priv can't be used directly. It
4217 * could already have been destroyed.
4220 of
->priv
= cgroup_pidlist_find(cgrp
, type
);
4223 * Either this is the first start() after open or the matching
4224 * pidlist has been destroyed inbetween. Create a new one.
4227 ret
= pidlist_array_load(cgrp
, type
,
4228 (struct cgroup_pidlist
**)&of
->priv
);
4230 return ERR_PTR(ret
);
4235 int end
= l
->length
;
4237 while (index
< end
) {
4238 int mid
= (index
+ end
) / 2;
4239 if (cgroup_pid_fry(cgrp
, l
->list
[mid
]) == pid
) {
4242 } else if (cgroup_pid_fry(cgrp
, l
->list
[mid
]) <= pid
)
4248 /* If we're off the end of the array, we're done */
4249 if (index
>= l
->length
)
4251 /* Update the abstract position to be the actual pid that we found */
4252 iter
= l
->list
+ index
;
4253 *pos
= cgroup_pid_fry(cgrp
, *iter
);
4257 static void cgroup_pidlist_stop(struct seq_file
*s
, void *v
)
4259 struct kernfs_open_file
*of
= s
->private;
4260 struct cgroup_pidlist
*l
= of
->priv
;
4263 mod_delayed_work(cgroup_pidlist_destroy_wq
, &l
->destroy_dwork
,
4264 CGROUP_PIDLIST_DESTROY_DELAY
);
4265 mutex_unlock(&seq_css(s
)->cgroup
->pidlist_mutex
);
4268 static void *cgroup_pidlist_next(struct seq_file
*s
, void *v
, loff_t
*pos
)
4270 struct kernfs_open_file
*of
= s
->private;
4271 struct cgroup_pidlist
*l
= of
->priv
;
4273 pid_t
*end
= l
->list
+ l
->length
;
4275 * Advance to the next pid in the array. If this goes off the
4282 *pos
= cgroup_pid_fry(seq_css(s
)->cgroup
, *p
);
4287 static int cgroup_pidlist_show(struct seq_file
*s
, void *v
)
4289 seq_printf(s
, "%d\n", *(int *)v
);
4294 static u64
cgroup_read_notify_on_release(struct cgroup_subsys_state
*css
,
4297 return notify_on_release(css
->cgroup
);
4300 static int cgroup_write_notify_on_release(struct cgroup_subsys_state
*css
,
4301 struct cftype
*cft
, u64 val
)
4304 set_bit(CGRP_NOTIFY_ON_RELEASE
, &css
->cgroup
->flags
);
4306 clear_bit(CGRP_NOTIFY_ON_RELEASE
, &css
->cgroup
->flags
);
4310 static u64
cgroup_clone_children_read(struct cgroup_subsys_state
*css
,
4313 return test_bit(CGRP_CPUSET_CLONE_CHILDREN
, &css
->cgroup
->flags
);
4316 static int cgroup_clone_children_write(struct cgroup_subsys_state
*css
,
4317 struct cftype
*cft
, u64 val
)
4320 set_bit(CGRP_CPUSET_CLONE_CHILDREN
, &css
->cgroup
->flags
);
4322 clear_bit(CGRP_CPUSET_CLONE_CHILDREN
, &css
->cgroup
->flags
);
4326 /* cgroup core interface files for the default hierarchy */
4327 static struct cftype cgroup_dfl_base_files
[] = {
4329 .name
= "cgroup.procs",
4330 .seq_start
= cgroup_pidlist_start
,
4331 .seq_next
= cgroup_pidlist_next
,
4332 .seq_stop
= cgroup_pidlist_stop
,
4333 .seq_show
= cgroup_pidlist_show
,
4334 .private = CGROUP_FILE_PROCS
,
4335 .write
= cgroup_procs_write
,
4336 .mode
= S_IRUGO
| S_IWUSR
,
4339 .name
= "cgroup.controllers",
4340 .flags
= CFTYPE_ONLY_ON_ROOT
,
4341 .seq_show
= cgroup_root_controllers_show
,
4344 .name
= "cgroup.controllers",
4345 .flags
= CFTYPE_NOT_ON_ROOT
,
4346 .seq_show
= cgroup_controllers_show
,
4349 .name
= "cgroup.subtree_control",
4350 .seq_show
= cgroup_subtree_control_show
,
4351 .write
= cgroup_subtree_control_write
,
4354 .name
= "cgroup.populated",
4355 .flags
= CFTYPE_NOT_ON_ROOT
,
4356 .seq_show
= cgroup_populated_show
,
4361 /* cgroup core interface files for the legacy hierarchies */
4362 static struct cftype cgroup_legacy_base_files
[] = {
4364 .name
= "cgroup.procs",
4365 .seq_start
= cgroup_pidlist_start
,
4366 .seq_next
= cgroup_pidlist_next
,
4367 .seq_stop
= cgroup_pidlist_stop
,
4368 .seq_show
= cgroup_pidlist_show
,
4369 .private = CGROUP_FILE_PROCS
,
4370 .write
= cgroup_procs_write
,
4371 .mode
= S_IRUGO
| S_IWUSR
,
4374 .name
= "cgroup.clone_children",
4375 .read_u64
= cgroup_clone_children_read
,
4376 .write_u64
= cgroup_clone_children_write
,
4379 .name
= "cgroup.sane_behavior",
4380 .flags
= CFTYPE_ONLY_ON_ROOT
,
4381 .seq_show
= cgroup_sane_behavior_show
,
4385 .seq_start
= cgroup_pidlist_start
,
4386 .seq_next
= cgroup_pidlist_next
,
4387 .seq_stop
= cgroup_pidlist_stop
,
4388 .seq_show
= cgroup_pidlist_show
,
4389 .private = CGROUP_FILE_TASKS
,
4390 .write
= cgroup_tasks_write
,
4391 .mode
= S_IRUGO
| S_IWUSR
,
4394 .name
= "notify_on_release",
4395 .read_u64
= cgroup_read_notify_on_release
,
4396 .write_u64
= cgroup_write_notify_on_release
,
4399 .name
= "release_agent",
4400 .flags
= CFTYPE_ONLY_ON_ROOT
,
4401 .seq_show
= cgroup_release_agent_show
,
4402 .write
= cgroup_release_agent_write
,
4403 .max_write_len
= PATH_MAX
- 1,
4409 * cgroup_populate_dir - create subsys files in a cgroup directory
4410 * @cgrp: target cgroup
4411 * @subsys_mask: mask of the subsystem ids whose files should be added
4413 * On failure, no file is added.
4415 static int cgroup_populate_dir(struct cgroup
*cgrp
, unsigned long subsys_mask
)
4417 struct cgroup_subsys
*ss
;
4420 /* process cftsets of each subsystem */
4421 for_each_subsys(ss
, i
) {
4422 struct cftype
*cfts
;
4424 if (!(subsys_mask
& (1 << i
)))
4427 list_for_each_entry(cfts
, &ss
->cfts
, node
) {
4428 ret
= cgroup_addrm_files(cgrp
, cfts
, true);
4435 cgroup_clear_dir(cgrp
, subsys_mask
);
4440 * css destruction is four-stage process.
4442 * 1. Destruction starts. Killing of the percpu_ref is initiated.
4443 * Implemented in kill_css().
4445 * 2. When the percpu_ref is confirmed to be visible as killed on all CPUs
4446 * and thus css_tryget_online() is guaranteed to fail, the css can be
4447 * offlined by invoking offline_css(). After offlining, the base ref is
4448 * put. Implemented in css_killed_work_fn().
4450 * 3. When the percpu_ref reaches zero, the only possible remaining
4451 * accessors are inside RCU read sections. css_release() schedules the
4454 * 4. After the grace period, the css can be freed. Implemented in
4455 * css_free_work_fn().
4457 * It is actually hairier because both step 2 and 4 require process context
4458 * and thus involve punting to css->destroy_work adding two additional
4459 * steps to the already complex sequence.
4461 static void css_free_work_fn(struct work_struct
*work
)
4463 struct cgroup_subsys_state
*css
=
4464 container_of(work
, struct cgroup_subsys_state
, destroy_work
);
4465 struct cgroup_subsys
*ss
= css
->ss
;
4466 struct cgroup
*cgrp
= css
->cgroup
;
4468 percpu_ref_exit(&css
->refcnt
);
4475 css_put(css
->parent
);
4478 cgroup_idr_remove(&ss
->css_idr
, id
);
4481 /* cgroup free path */
4482 atomic_dec(&cgrp
->root
->nr_cgrps
);
4483 cgroup_pidlist_destroy_all(cgrp
);
4484 cancel_work_sync(&cgrp
->release_agent_work
);
4486 if (cgroup_parent(cgrp
)) {
4488 * We get a ref to the parent, and put the ref when
4489 * this cgroup is being freed, so it's guaranteed
4490 * that the parent won't be destroyed before its
4493 cgroup_put(cgroup_parent(cgrp
));
4494 kernfs_put(cgrp
->kn
);
4498 * This is root cgroup's refcnt reaching zero,
4499 * which indicates that the root should be
4502 cgroup_destroy_root(cgrp
->root
);
4507 static void css_free_rcu_fn(struct rcu_head
*rcu_head
)
4509 struct cgroup_subsys_state
*css
=
4510 container_of(rcu_head
, struct cgroup_subsys_state
, rcu_head
);
4512 INIT_WORK(&css
->destroy_work
, css_free_work_fn
);
4513 queue_work(cgroup_destroy_wq
, &css
->destroy_work
);
4516 static void css_release_work_fn(struct work_struct
*work
)
4518 struct cgroup_subsys_state
*css
=
4519 container_of(work
, struct cgroup_subsys_state
, destroy_work
);
4520 struct cgroup_subsys
*ss
= css
->ss
;
4521 struct cgroup
*cgrp
= css
->cgroup
;
4523 mutex_lock(&cgroup_mutex
);
4525 css
->flags
|= CSS_RELEASED
;
4526 list_del_rcu(&css
->sibling
);
4529 /* css release path */
4530 cgroup_idr_replace(&ss
->css_idr
, NULL
, css
->id
);
4531 if (ss
->css_released
)
4532 ss
->css_released(css
);
4534 /* cgroup release path */
4535 cgroup_idr_remove(&cgrp
->root
->cgroup_idr
, cgrp
->id
);
4539 * There are two control paths which try to determine
4540 * cgroup from dentry without going through kernfs -
4541 * cgroupstats_build() and css_tryget_online_from_dir().
4542 * Those are supported by RCU protecting clearing of
4543 * cgrp->kn->priv backpointer.
4545 RCU_INIT_POINTER(*(void __rcu __force
**)&cgrp
->kn
->priv
, NULL
);
4548 mutex_unlock(&cgroup_mutex
);
4550 call_rcu(&css
->rcu_head
, css_free_rcu_fn
);
4553 static void css_release(struct percpu_ref
*ref
)
4555 struct cgroup_subsys_state
*css
=
4556 container_of(ref
, struct cgroup_subsys_state
, refcnt
);
4558 INIT_WORK(&css
->destroy_work
, css_release_work_fn
);
4559 queue_work(cgroup_destroy_wq
, &css
->destroy_work
);
4562 static void init_and_link_css(struct cgroup_subsys_state
*css
,
4563 struct cgroup_subsys
*ss
, struct cgroup
*cgrp
)
4565 lockdep_assert_held(&cgroup_mutex
);
4569 memset(css
, 0, sizeof(*css
));
4572 INIT_LIST_HEAD(&css
->sibling
);
4573 INIT_LIST_HEAD(&css
->children
);
4574 css
->serial_nr
= css_serial_nr_next
++;
4576 if (cgroup_parent(cgrp
)) {
4577 css
->parent
= cgroup_css(cgroup_parent(cgrp
), ss
);
4578 css_get(css
->parent
);
4581 BUG_ON(cgroup_css(cgrp
, ss
));
4584 /* invoke ->css_online() on a new CSS and mark it online if successful */
4585 static int online_css(struct cgroup_subsys_state
*css
)
4587 struct cgroup_subsys
*ss
= css
->ss
;
4590 lockdep_assert_held(&cgroup_mutex
);
4593 ret
= ss
->css_online(css
);
4595 css
->flags
|= CSS_ONLINE
;
4596 rcu_assign_pointer(css
->cgroup
->subsys
[ss
->id
], css
);
4601 /* if the CSS is online, invoke ->css_offline() on it and mark it offline */
4602 static void offline_css(struct cgroup_subsys_state
*css
)
4604 struct cgroup_subsys
*ss
= css
->ss
;
4606 lockdep_assert_held(&cgroup_mutex
);
4608 if (!(css
->flags
& CSS_ONLINE
))
4611 if (ss
->css_offline
)
4612 ss
->css_offline(css
);
4614 css
->flags
&= ~CSS_ONLINE
;
4615 RCU_INIT_POINTER(css
->cgroup
->subsys
[ss
->id
], NULL
);
4617 wake_up_all(&css
->cgroup
->offline_waitq
);
4621 * create_css - create a cgroup_subsys_state
4622 * @cgrp: the cgroup new css will be associated with
4623 * @ss: the subsys of new css
4624 * @visible: whether to create control knobs for the new css or not
4626 * Create a new css associated with @cgrp - @ss pair. On success, the new
4627 * css is online and installed in @cgrp with all interface files created if
4628 * @visible. Returns 0 on success, -errno on failure.
4630 static int create_css(struct cgroup
*cgrp
, struct cgroup_subsys
*ss
,
4633 struct cgroup
*parent
= cgroup_parent(cgrp
);
4634 struct cgroup_subsys_state
*parent_css
= cgroup_css(parent
, ss
);
4635 struct cgroup_subsys_state
*css
;
4638 lockdep_assert_held(&cgroup_mutex
);
4640 css
= ss
->css_alloc(parent_css
);
4642 return PTR_ERR(css
);
4644 init_and_link_css(css
, ss
, cgrp
);
4646 err
= percpu_ref_init(&css
->refcnt
, css_release
, 0, GFP_KERNEL
);
4650 err
= cgroup_idr_alloc(&ss
->css_idr
, NULL
, 2, 0, GFP_KERNEL
);
4652 goto err_free_percpu_ref
;
4656 err
= cgroup_populate_dir(cgrp
, 1 << ss
->id
);
4661 /* @css is ready to be brought online now, make it visible */
4662 list_add_tail_rcu(&css
->sibling
, &parent_css
->children
);
4663 cgroup_idr_replace(&ss
->css_idr
, css
, css
->id
);
4665 err
= online_css(css
);
4669 if (ss
->broken_hierarchy
&& !ss
->warned_broken_hierarchy
&&
4670 cgroup_parent(parent
)) {
4671 pr_warn("%s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n",
4672 current
->comm
, current
->pid
, ss
->name
);
4673 if (!strcmp(ss
->name
, "memory"))
4674 pr_warn("\"memory\" requires setting use_hierarchy to 1 on the root\n");
4675 ss
->warned_broken_hierarchy
= true;
4681 list_del_rcu(&css
->sibling
);
4682 cgroup_clear_dir(css
->cgroup
, 1 << css
->ss
->id
);
4684 cgroup_idr_remove(&ss
->css_idr
, css
->id
);
4685 err_free_percpu_ref
:
4686 percpu_ref_exit(&css
->refcnt
);
4688 call_rcu(&css
->rcu_head
, css_free_rcu_fn
);
4692 static int cgroup_mkdir(struct kernfs_node
*parent_kn
, const char *name
,
4695 struct cgroup
*parent
, *cgrp
;
4696 struct cgroup_root
*root
;
4697 struct cgroup_subsys
*ss
;
4698 struct kernfs_node
*kn
;
4699 struct cftype
*base_files
;
4702 /* Do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable.
4704 if (strchr(name
, '\n'))
4707 parent
= cgroup_kn_lock_live(parent_kn
);
4710 root
= parent
->root
;
4712 /* allocate the cgroup and its ID, 0 is reserved for the root */
4713 cgrp
= kzalloc(sizeof(*cgrp
), GFP_KERNEL
);
4719 ret
= percpu_ref_init(&cgrp
->self
.refcnt
, css_release
, 0, GFP_KERNEL
);
4724 * Temporarily set the pointer to NULL, so idr_find() won't return
4725 * a half-baked cgroup.
4727 cgrp
->id
= cgroup_idr_alloc(&root
->cgroup_idr
, NULL
, 2, 0, GFP_KERNEL
);
4730 goto out_cancel_ref
;
4733 init_cgroup_housekeeping(cgrp
);
4735 cgrp
->self
.parent
= &parent
->self
;
4738 if (notify_on_release(parent
))
4739 set_bit(CGRP_NOTIFY_ON_RELEASE
, &cgrp
->flags
);
4741 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN
, &parent
->flags
))
4742 set_bit(CGRP_CPUSET_CLONE_CHILDREN
, &cgrp
->flags
);
4744 /* create the directory */
4745 kn
= kernfs_create_dir(parent
->kn
, name
, mode
, cgrp
);
4753 * This extra ref will be put in cgroup_free_fn() and guarantees
4754 * that @cgrp->kn is always accessible.
4758 cgrp
->self
.serial_nr
= css_serial_nr_next
++;
4760 /* allocation complete, commit to creation */
4761 list_add_tail_rcu(&cgrp
->self
.sibling
, &cgroup_parent(cgrp
)->self
.children
);
4762 atomic_inc(&root
->nr_cgrps
);
4766 * @cgrp is now fully operational. If something fails after this
4767 * point, it'll be released via the normal destruction path.
4769 cgroup_idr_replace(&root
->cgroup_idr
, cgrp
, cgrp
->id
);
4771 ret
= cgroup_kn_set_ugid(kn
);
4775 if (cgroup_on_dfl(cgrp
))
4776 base_files
= cgroup_dfl_base_files
;
4778 base_files
= cgroup_legacy_base_files
;
4780 ret
= cgroup_addrm_files(cgrp
, base_files
, true);
4784 /* let's create and online css's */
4785 for_each_subsys(ss
, ssid
) {
4786 if (parent
->child_subsys_mask
& (1 << ssid
)) {
4787 ret
= create_css(cgrp
, ss
,
4788 parent
->subtree_control
& (1 << ssid
));
4795 * On the default hierarchy, a child doesn't automatically inherit
4796 * subtree_control from the parent. Each is configured manually.
4798 if (!cgroup_on_dfl(cgrp
)) {
4799 cgrp
->subtree_control
= parent
->subtree_control
;
4800 cgroup_refresh_child_subsys_mask(cgrp
);
4803 kernfs_activate(kn
);
4809 cgroup_idr_remove(&root
->cgroup_idr
, cgrp
->id
);
4811 percpu_ref_exit(&cgrp
->self
.refcnt
);
4815 cgroup_kn_unlock(parent_kn
);
4819 cgroup_destroy_locked(cgrp
);
4824 * This is called when the refcnt of a css is confirmed to be killed.
4825 * css_tryget_online() is now guaranteed to fail. Tell the subsystem to
4826 * initate destruction and put the css ref from kill_css().
4828 static void css_killed_work_fn(struct work_struct
*work
)
4830 struct cgroup_subsys_state
*css
=
4831 container_of(work
, struct cgroup_subsys_state
, destroy_work
);
4833 mutex_lock(&cgroup_mutex
);
4835 mutex_unlock(&cgroup_mutex
);
4840 /* css kill confirmation processing requires process context, bounce */
4841 static void css_killed_ref_fn(struct percpu_ref
*ref
)
4843 struct cgroup_subsys_state
*css
=
4844 container_of(ref
, struct cgroup_subsys_state
, refcnt
);
4846 INIT_WORK(&css
->destroy_work
, css_killed_work_fn
);
4847 queue_work(cgroup_destroy_wq
, &css
->destroy_work
);
4851 * kill_css - destroy a css
4852 * @css: css to destroy
4854 * This function initiates destruction of @css by removing cgroup interface
4855 * files and putting its base reference. ->css_offline() will be invoked
4856 * asynchronously once css_tryget_online() is guaranteed to fail and when
4857 * the reference count reaches zero, @css will be released.
4859 static void kill_css(struct cgroup_subsys_state
*css
)
4861 lockdep_assert_held(&cgroup_mutex
);
4864 * This must happen before css is disassociated with its cgroup.
4865 * See seq_css() for details.
4867 cgroup_clear_dir(css
->cgroup
, 1 << css
->ss
->id
);
4870 * Killing would put the base ref, but we need to keep it alive
4871 * until after ->css_offline().
4876 * cgroup core guarantees that, by the time ->css_offline() is
4877 * invoked, no new css reference will be given out via
4878 * css_tryget_online(). We can't simply call percpu_ref_kill() and
4879 * proceed to offlining css's because percpu_ref_kill() doesn't
4880 * guarantee that the ref is seen as killed on all CPUs on return.
4882 * Use percpu_ref_kill_and_confirm() to get notifications as each
4883 * css is confirmed to be seen as killed on all CPUs.
4885 percpu_ref_kill_and_confirm(&css
->refcnt
, css_killed_ref_fn
);
4889 * cgroup_destroy_locked - the first stage of cgroup destruction
4890 * @cgrp: cgroup to be destroyed
4892 * css's make use of percpu refcnts whose killing latency shouldn't be
4893 * exposed to userland and are RCU protected. Also, cgroup core needs to
4894 * guarantee that css_tryget_online() won't succeed by the time
4895 * ->css_offline() is invoked. To satisfy all the requirements,
4896 * destruction is implemented in the following two steps.
4898 * s1. Verify @cgrp can be destroyed and mark it dying. Remove all
4899 * userland visible parts and start killing the percpu refcnts of
4900 * css's. Set up so that the next stage will be kicked off once all
4901 * the percpu refcnts are confirmed to be killed.
4903 * s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the
4904 * rest of destruction. Once all cgroup references are gone, the
4905 * cgroup is RCU-freed.
4907 * This function implements s1. After this step, @cgrp is gone as far as
4908 * the userland is concerned and a new cgroup with the same name may be
4909 * created. As cgroup doesn't care about the names internally, this
4910 * doesn't cause any problem.
4912 static int cgroup_destroy_locked(struct cgroup
*cgrp
)
4913 __releases(&cgroup_mutex
) __acquires(&cgroup_mutex
)
4915 struct cgroup_subsys_state
*css
;
4919 lockdep_assert_held(&cgroup_mutex
);
4922 * css_set_rwsem synchronizes access to ->cset_links and prevents
4923 * @cgrp from being removed while put_css_set() is in progress.
4925 down_read(&css_set_rwsem
);
4926 empty
= list_empty(&cgrp
->cset_links
);
4927 up_read(&css_set_rwsem
);
4932 * Make sure there's no live children. We can't test emptiness of
4933 * ->self.children as dead children linger on it while being
4934 * drained; otherwise, "rmdir parent/child parent" may fail.
4936 if (css_has_online_children(&cgrp
->self
))
4940 * Mark @cgrp dead. This prevents further task migration and child
4941 * creation by disabling cgroup_lock_live_group().
4943 cgrp
->self
.flags
&= ~CSS_ONLINE
;
4945 /* initiate massacre of all css's */
4946 for_each_css(css
, ssid
, cgrp
)
4950 * Remove @cgrp directory along with the base files. @cgrp has an
4951 * extra ref on its kn.
4953 kernfs_remove(cgrp
->kn
);
4955 check_for_release(cgroup_parent(cgrp
));
4957 /* put the base reference */
4958 percpu_ref_kill(&cgrp
->self
.refcnt
);
4963 static int cgroup_rmdir(struct kernfs_node
*kn
)
4965 struct cgroup
*cgrp
;
4968 cgrp
= cgroup_kn_lock_live(kn
);
4972 ret
= cgroup_destroy_locked(cgrp
);
4974 cgroup_kn_unlock(kn
);
4978 static struct kernfs_syscall_ops cgroup_kf_syscall_ops
= {
4979 .remount_fs
= cgroup_remount
,
4980 .show_options
= cgroup_show_options
,
4981 .mkdir
= cgroup_mkdir
,
4982 .rmdir
= cgroup_rmdir
,
4983 .rename
= cgroup_rename
,
4986 static void __init
cgroup_init_subsys(struct cgroup_subsys
*ss
, bool early
)
4988 struct cgroup_subsys_state
*css
;
4990 printk(KERN_INFO
"Initializing cgroup subsys %s\n", ss
->name
);
4992 mutex_lock(&cgroup_mutex
);
4994 idr_init(&ss
->css_idr
);
4995 INIT_LIST_HEAD(&ss
->cfts
);
4997 /* Create the root cgroup state for this subsystem */
4998 ss
->root
= &cgrp_dfl_root
;
4999 css
= ss
->css_alloc(cgroup_css(&cgrp_dfl_root
.cgrp
, ss
));
5000 /* We don't handle early failures gracefully */
5001 BUG_ON(IS_ERR(css
));
5002 init_and_link_css(css
, ss
, &cgrp_dfl_root
.cgrp
);
5005 * Root csses are never destroyed and we can't initialize
5006 * percpu_ref during early init. Disable refcnting.
5008 css
->flags
|= CSS_NO_REF
;
5011 /* allocation can't be done safely during early init */
5014 css
->id
= cgroup_idr_alloc(&ss
->css_idr
, css
, 1, 2, GFP_KERNEL
);
5015 BUG_ON(css
->id
< 0);
5018 /* Update the init_css_set to contain a subsys
5019 * pointer to this state - since the subsystem is
5020 * newly registered, all tasks and hence the
5021 * init_css_set is in the subsystem's root cgroup. */
5022 init_css_set
.subsys
[ss
->id
] = css
;
5024 have_fork_callback
|= (bool)ss
->fork
<< ss
->id
;
5025 have_exit_callback
|= (bool)ss
->exit
<< ss
->id
;
5026 have_canfork_callback
|= (bool)ss
->can_fork
<< ss
->id
;
5028 /* At system boot, before all subsystems have been
5029 * registered, no tasks have been forked, so we don't
5030 * need to invoke fork callbacks here. */
5031 BUG_ON(!list_empty(&init_task
.tasks
));
5033 BUG_ON(online_css(css
));
5035 mutex_unlock(&cgroup_mutex
);
5039 * cgroup_init_early - cgroup initialization at system boot
5041 * Initialize cgroups at system boot, and initialize any
5042 * subsystems that request early init.
5044 int __init
cgroup_init_early(void)
5046 static struct cgroup_sb_opts __initdata opts
;
5047 struct cgroup_subsys
*ss
;
5050 init_cgroup_root(&cgrp_dfl_root
, &opts
);
5051 cgrp_dfl_root
.cgrp
.self
.flags
|= CSS_NO_REF
;
5053 RCU_INIT_POINTER(init_task
.cgroups
, &init_css_set
);
5055 for_each_subsys(ss
, i
) {
5056 WARN(!ss
->css_alloc
|| !ss
->css_free
|| ss
->name
|| ss
->id
,
5057 "invalid cgroup_subsys %d:%s css_alloc=%p css_free=%p name:id=%d:%s\n",
5058 i
, cgroup_subsys_name
[i
], ss
->css_alloc
, ss
->css_free
,
5060 WARN(strlen(cgroup_subsys_name
[i
]) > MAX_CGROUP_TYPE_NAMELEN
,
5061 "cgroup_subsys_name %s too long\n", cgroup_subsys_name
[i
]);
5064 ss
->name
= cgroup_subsys_name
[i
];
5065 if (!ss
->legacy_name
)
5066 ss
->legacy_name
= cgroup_subsys_name
[i
];
5069 cgroup_init_subsys(ss
, true);
5075 * cgroup_init - cgroup initialization
5077 * Register cgroup filesystem and /proc file, and initialize
5078 * any subsystems that didn't request early init.
5080 int __init
cgroup_init(void)
5082 struct cgroup_subsys
*ss
;
5086 BUG_ON(cgroup_init_cftypes(NULL
, cgroup_dfl_base_files
));
5087 BUG_ON(cgroup_init_cftypes(NULL
, cgroup_legacy_base_files
));
5089 mutex_lock(&cgroup_mutex
);
5091 /* Add init_css_set to the hash table */
5092 key
= css_set_hash(init_css_set
.subsys
);
5093 hash_add(css_set_table
, &init_css_set
.hlist
, key
);
5095 BUG_ON(cgroup_setup_root(&cgrp_dfl_root
, 0));
5097 mutex_unlock(&cgroup_mutex
);
5099 for_each_subsys(ss
, ssid
) {
5100 if (ss
->early_init
) {
5101 struct cgroup_subsys_state
*css
=
5102 init_css_set
.subsys
[ss
->id
];
5104 css
->id
= cgroup_idr_alloc(&ss
->css_idr
, css
, 1, 2,
5106 BUG_ON(css
->id
< 0);
5108 cgroup_init_subsys(ss
, false);
5111 list_add_tail(&init_css_set
.e_cset_node
[ssid
],
5112 &cgrp_dfl_root
.cgrp
.e_csets
[ssid
]);
5115 * Setting dfl_root subsys_mask needs to consider the
5116 * disabled flag and cftype registration needs kmalloc,
5117 * both of which aren't available during early_init.
5122 cgrp_dfl_root
.subsys_mask
|= 1 << ss
->id
;
5124 if (cgroup_legacy_files_on_dfl
&& !ss
->dfl_cftypes
)
5125 ss
->dfl_cftypes
= ss
->legacy_cftypes
;
5127 if (!ss
->dfl_cftypes
)
5128 cgrp_dfl_root_inhibit_ss_mask
|= 1 << ss
->id
;
5130 if (ss
->dfl_cftypes
== ss
->legacy_cftypes
) {
5131 WARN_ON(cgroup_add_cftypes(ss
, ss
->dfl_cftypes
));
5133 WARN_ON(cgroup_add_dfl_cftypes(ss
, ss
->dfl_cftypes
));
5134 WARN_ON(cgroup_add_legacy_cftypes(ss
, ss
->legacy_cftypes
));
5138 ss
->bind(init_css_set
.subsys
[ssid
]);
5141 err
= sysfs_create_mount_point(fs_kobj
, "cgroup");
5145 err
= register_filesystem(&cgroup_fs_type
);
5147 sysfs_remove_mount_point(fs_kobj
, "cgroup");
5151 proc_create("cgroups", 0, NULL
, &proc_cgroupstats_operations
);
5155 static int __init
cgroup_wq_init(void)
5158 * There isn't much point in executing destruction path in
5159 * parallel. Good chunk is serialized with cgroup_mutex anyway.
5160 * Use 1 for @max_active.
5162 * We would prefer to do this in cgroup_init() above, but that
5163 * is called before init_workqueues(): so leave this until after.
5165 cgroup_destroy_wq
= alloc_workqueue("cgroup_destroy", 0, 1);
5166 BUG_ON(!cgroup_destroy_wq
);
5169 * Used to destroy pidlists and separate to serve as flush domain.
5170 * Cap @max_active to 1 too.
5172 cgroup_pidlist_destroy_wq
= alloc_workqueue("cgroup_pidlist_destroy",
5174 BUG_ON(!cgroup_pidlist_destroy_wq
);
5178 core_initcall(cgroup_wq_init
);
5181 * proc_cgroup_show()
5182 * - Print task's cgroup paths into seq_file, one line for each hierarchy
5183 * - Used for /proc/<pid>/cgroup.
5185 int proc_cgroup_show(struct seq_file
*m
, struct pid_namespace
*ns
,
5186 struct pid
*pid
, struct task_struct
*tsk
)
5190 struct cgroup_root
*root
;
5193 buf
= kmalloc(PATH_MAX
, GFP_KERNEL
);
5197 mutex_lock(&cgroup_mutex
);
5198 down_read(&css_set_rwsem
);
5200 for_each_root(root
) {
5201 struct cgroup_subsys
*ss
;
5202 struct cgroup
*cgrp
;
5203 int ssid
, count
= 0;
5205 if (root
== &cgrp_dfl_root
&& !cgrp_dfl_root_visible
)
5208 seq_printf(m
, "%d:", root
->hierarchy_id
);
5209 if (root
!= &cgrp_dfl_root
)
5210 for_each_subsys(ss
, ssid
)
5211 if (root
->subsys_mask
& (1 << ssid
))
5212 seq_printf(m
, "%s%s", count
++ ? "," : "",
5214 if (strlen(root
->name
))
5215 seq_printf(m
, "%sname=%s", count
? "," : "",
5218 cgrp
= task_cgroup_from_root(tsk
, root
);
5219 path
= cgroup_path(cgrp
, buf
, PATH_MAX
);
5221 retval
= -ENAMETOOLONG
;
5230 up_read(&css_set_rwsem
);
5231 mutex_unlock(&cgroup_mutex
);
5237 /* Display information about each subsystem and each hierarchy */
5238 static int proc_cgroupstats_show(struct seq_file
*m
, void *v
)
5240 struct cgroup_subsys
*ss
;
5243 seq_puts(m
, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
5245 * ideally we don't want subsystems moving around while we do this.
5246 * cgroup_mutex is also necessary to guarantee an atomic snapshot of
5247 * subsys/hierarchy state.
5249 mutex_lock(&cgroup_mutex
);
5251 for_each_subsys(ss
, i
)
5252 seq_printf(m
, "%s\t%d\t%d\t%d\n",
5253 ss
->legacy_name
, ss
->root
->hierarchy_id
,
5254 atomic_read(&ss
->root
->nr_cgrps
), !ss
->disabled
);
5256 mutex_unlock(&cgroup_mutex
);
5260 static int cgroupstats_open(struct inode
*inode
, struct file
*file
)
5262 return single_open(file
, proc_cgroupstats_show
, NULL
);
5265 static const struct file_operations proc_cgroupstats_operations
= {
5266 .open
= cgroupstats_open
,
5268 .llseek
= seq_lseek
,
5269 .release
= single_release
,
5272 static void **subsys_canfork_priv_p(void *ss_priv
[CGROUP_CANFORK_COUNT
], int i
)
5274 if (CGROUP_CANFORK_START
<= i
&& i
< CGROUP_CANFORK_END
)
5275 return &ss_priv
[i
- CGROUP_CANFORK_START
];
5279 static void *subsys_canfork_priv(void *ss_priv
[CGROUP_CANFORK_COUNT
], int i
)
5281 void **private = subsys_canfork_priv_p(ss_priv
, i
);
5282 return private ? *private : NULL
;
5286 * cgroup_fork - initialize cgroup related fields during copy_process()
5287 * @child: pointer to task_struct of forking parent process.
5289 * A task is associated with the init_css_set until cgroup_post_fork()
5290 * attaches it to the parent's css_set. Empty cg_list indicates that
5291 * @child isn't holding reference to its css_set.
5293 void cgroup_fork(struct task_struct
*child
)
5295 RCU_INIT_POINTER(child
->cgroups
, &init_css_set
);
5296 INIT_LIST_HEAD(&child
->cg_list
);
5300 * cgroup_can_fork - called on a new task before the process is exposed
5301 * @child: the task in question.
5303 * This calls the subsystem can_fork() callbacks. If the can_fork() callback
5304 * returns an error, the fork aborts with that error code. This allows for
5305 * a cgroup subsystem to conditionally allow or deny new forks.
5307 int cgroup_can_fork(struct task_struct
*child
,
5308 void *ss_priv
[CGROUP_CANFORK_COUNT
])
5310 struct cgroup_subsys
*ss
;
5313 for_each_subsys_which(ss
, i
, &have_canfork_callback
) {
5314 ret
= ss
->can_fork(child
, subsys_canfork_priv_p(ss_priv
, i
));
5322 for_each_subsys(ss
, j
) {
5325 if (ss
->cancel_fork
)
5326 ss
->cancel_fork(child
, subsys_canfork_priv(ss_priv
, j
));
5333 * cgroup_cancel_fork - called if a fork failed after cgroup_can_fork()
5334 * @child: the task in question
5336 * This calls the cancel_fork() callbacks if a fork failed *after*
5337 * cgroup_can_fork() succeded.
5339 void cgroup_cancel_fork(struct task_struct
*child
,
5340 void *ss_priv
[CGROUP_CANFORK_COUNT
])
5342 struct cgroup_subsys
*ss
;
5345 for_each_subsys(ss
, i
)
5346 if (ss
->cancel_fork
)
5347 ss
->cancel_fork(child
, subsys_canfork_priv(ss_priv
, i
));
5351 * cgroup_post_fork - called on a new task after adding it to the task list
5352 * @child: the task in question
5354 * Adds the task to the list running through its css_set if necessary and
5355 * call the subsystem fork() callbacks. Has to be after the task is
5356 * visible on the task list in case we race with the first call to
5357 * cgroup_task_iter_start() - to guarantee that the new task ends up on its
5360 void cgroup_post_fork(struct task_struct
*child
,
5361 void *old_ss_priv
[CGROUP_CANFORK_COUNT
])
5363 struct cgroup_subsys
*ss
;
5367 * This may race against cgroup_enable_task_cg_lists(). As that
5368 * function sets use_task_css_set_links before grabbing
5369 * tasklist_lock and we just went through tasklist_lock to add
5370 * @child, it's guaranteed that either we see the set
5371 * use_task_css_set_links or cgroup_enable_task_cg_lists() sees
5372 * @child during its iteration.
5374 * If we won the race, @child is associated with %current's
5375 * css_set. Grabbing css_set_rwsem guarantees both that the
5376 * association is stable, and, on completion of the parent's
5377 * migration, @child is visible in the source of migration or
5378 * already in the destination cgroup. This guarantee is necessary
5379 * when implementing operations which need to migrate all tasks of
5380 * a cgroup to another.
5382 * Note that if we lose to cgroup_enable_task_cg_lists(), @child
5383 * will remain in init_css_set. This is safe because all tasks are
5384 * in the init_css_set before cg_links is enabled and there's no
5385 * operation which transfers all tasks out of init_css_set.
5387 if (use_task_css_set_links
) {
5388 struct css_set
*cset
;
5390 down_write(&css_set_rwsem
);
5391 cset
= task_css_set(current
);
5392 if (list_empty(&child
->cg_list
)) {
5393 rcu_assign_pointer(child
->cgroups
, cset
);
5394 list_add(&child
->cg_list
, &cset
->tasks
);
5397 up_write(&css_set_rwsem
);
5401 * Call ss->fork(). This must happen after @child is linked on
5402 * css_set; otherwise, @child might change state between ->fork()
5403 * and addition to css_set.
5405 for_each_subsys_which(ss
, i
, &have_fork_callback
)
5406 ss
->fork(child
, subsys_canfork_priv(old_ss_priv
, i
));
5410 * cgroup_exit - detach cgroup from exiting task
5411 * @tsk: pointer to task_struct of exiting process
5413 * Description: Detach cgroup from @tsk and release it.
5415 * Note that cgroups marked notify_on_release force every task in
5416 * them to take the global cgroup_mutex mutex when exiting.
5417 * This could impact scaling on very large systems. Be reluctant to
5418 * use notify_on_release cgroups where very high task exit scaling
5419 * is required on large systems.
5421 * We set the exiting tasks cgroup to the root cgroup (top_cgroup). We
5422 * call cgroup_exit() while the task is still competent to handle
5423 * notify_on_release(), then leave the task attached to the root cgroup in
5424 * each hierarchy for the remainder of its exit. No need to bother with
5425 * init_css_set refcnting. init_css_set never goes away and we can't race
5426 * with migration path - PF_EXITING is visible to migration path.
5428 void cgroup_exit(struct task_struct
*tsk
)
5430 struct cgroup_subsys
*ss
;
5431 struct css_set
*cset
;
5432 bool put_cset
= false;
5436 * Unlink from @tsk from its css_set. As migration path can't race
5437 * with us, we can check cg_list without grabbing css_set_rwsem.
5439 if (!list_empty(&tsk
->cg_list
)) {
5440 down_write(&css_set_rwsem
);
5441 list_del_init(&tsk
->cg_list
);
5442 up_write(&css_set_rwsem
);
5446 /* Reassign the task to the init_css_set. */
5447 cset
= task_css_set(tsk
);
5448 RCU_INIT_POINTER(tsk
->cgroups
, &init_css_set
);
5450 /* see cgroup_post_fork() for details */
5451 for_each_subsys_which(ss
, i
, &have_exit_callback
) {
5452 struct cgroup_subsys_state
*old_css
= cset
->subsys
[i
];
5453 struct cgroup_subsys_state
*css
= task_css(tsk
, i
);
5455 ss
->exit(css
, old_css
, tsk
);
5462 static void check_for_release(struct cgroup
*cgrp
)
5464 if (notify_on_release(cgrp
) && !cgroup_has_tasks(cgrp
) &&
5465 !css_has_online_children(&cgrp
->self
) && !cgroup_is_dead(cgrp
))
5466 schedule_work(&cgrp
->release_agent_work
);
5470 * Notify userspace when a cgroup is released, by running the
5471 * configured release agent with the name of the cgroup (path
5472 * relative to the root of cgroup file system) as the argument.
5474 * Most likely, this user command will try to rmdir this cgroup.
5476 * This races with the possibility that some other task will be
5477 * attached to this cgroup before it is removed, or that some other
5478 * user task will 'mkdir' a child cgroup of this cgroup. That's ok.
5479 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
5480 * unused, and this cgroup will be reprieved from its death sentence,
5481 * to continue to serve a useful existence. Next time it's released,
5482 * we will get notified again, if it still has 'notify_on_release' set.
5484 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
5485 * means only wait until the task is successfully execve()'d. The
5486 * separate release agent task is forked by call_usermodehelper(),
5487 * then control in this thread returns here, without waiting for the
5488 * release agent task. We don't bother to wait because the caller of
5489 * this routine has no use for the exit status of the release agent
5490 * task, so no sense holding our caller up for that.
5492 static void cgroup_release_agent(struct work_struct
*work
)
5494 struct cgroup
*cgrp
=
5495 container_of(work
, struct cgroup
, release_agent_work
);
5496 char *pathbuf
= NULL
, *agentbuf
= NULL
, *path
;
5497 char *argv
[3], *envp
[3];
5499 mutex_lock(&cgroup_mutex
);
5501 pathbuf
= kmalloc(PATH_MAX
, GFP_KERNEL
);
5502 agentbuf
= kstrdup(cgrp
->root
->release_agent_path
, GFP_KERNEL
);
5503 if (!pathbuf
|| !agentbuf
)
5506 path
= cgroup_path(cgrp
, pathbuf
, PATH_MAX
);
5514 /* minimal command environment */
5516 envp
[1] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
5519 mutex_unlock(&cgroup_mutex
);
5520 call_usermodehelper(argv
[0], argv
, envp
, UMH_WAIT_EXEC
);
5523 mutex_unlock(&cgroup_mutex
);
5529 static int __init
cgroup_disable(char *str
)
5531 struct cgroup_subsys
*ss
;
5535 while ((token
= strsep(&str
, ",")) != NULL
) {
5539 for_each_subsys(ss
, i
) {
5540 if (strcmp(token
, ss
->name
) &&
5541 strcmp(token
, ss
->legacy_name
))
5545 printk(KERN_INFO
"Disabling %s control group subsystem\n",
5552 __setup("cgroup_disable=", cgroup_disable
);
5554 static int __init
cgroup_set_legacy_files_on_dfl(char *str
)
5556 printk("cgroup: using legacy files on the default hierarchy\n");
5557 cgroup_legacy_files_on_dfl
= true;
5560 __setup("cgroup__DEVEL__legacy_files_on_dfl", cgroup_set_legacy_files_on_dfl
);
5563 * css_tryget_online_from_dir - get corresponding css from a cgroup dentry
5564 * @dentry: directory dentry of interest
5565 * @ss: subsystem of interest
5567 * If @dentry is a directory for a cgroup which has @ss enabled on it, try
5568 * to get the corresponding css and return it. If such css doesn't exist
5569 * or can't be pinned, an ERR_PTR value is returned.
5571 struct cgroup_subsys_state
*css_tryget_online_from_dir(struct dentry
*dentry
,
5572 struct cgroup_subsys
*ss
)
5574 struct kernfs_node
*kn
= kernfs_node_from_dentry(dentry
);
5575 struct cgroup_subsys_state
*css
= NULL
;
5576 struct cgroup
*cgrp
;
5578 /* is @dentry a cgroup dir? */
5579 if (dentry
->d_sb
->s_type
!= &cgroup_fs_type
|| !kn
||
5580 kernfs_type(kn
) != KERNFS_DIR
)
5581 return ERR_PTR(-EBADF
);
5586 * This path doesn't originate from kernfs and @kn could already
5587 * have been or be removed at any point. @kn->priv is RCU
5588 * protected for this access. See css_release_work_fn() for details.
5590 cgrp
= rcu_dereference(kn
->priv
);
5592 css
= cgroup_css(cgrp
, ss
);
5594 if (!css
|| !css_tryget_online(css
))
5595 css
= ERR_PTR(-ENOENT
);
5602 * css_from_id - lookup css by id
5603 * @id: the cgroup id
5604 * @ss: cgroup subsys to be looked into
5606 * Returns the css if there's valid one with @id, otherwise returns NULL.
5607 * Should be called under rcu_read_lock().
5609 struct cgroup_subsys_state
*css_from_id(int id
, struct cgroup_subsys
*ss
)
5611 WARN_ON_ONCE(!rcu_read_lock_held());
5612 return id
> 0 ? idr_find(&ss
->css_idr
, id
) : NULL
;
5615 #ifdef CONFIG_CGROUP_DEBUG
5616 static struct cgroup_subsys_state
*
5617 debug_css_alloc(struct cgroup_subsys_state
*parent_css
)
5619 struct cgroup_subsys_state
*css
= kzalloc(sizeof(*css
), GFP_KERNEL
);
5622 return ERR_PTR(-ENOMEM
);
5627 static void debug_css_free(struct cgroup_subsys_state
*css
)
5632 static u64
debug_taskcount_read(struct cgroup_subsys_state
*css
,
5635 return cgroup_task_count(css
->cgroup
);
5638 static u64
current_css_set_read(struct cgroup_subsys_state
*css
,
5641 return (u64
)(unsigned long)current
->cgroups
;
5644 static u64
current_css_set_refcount_read(struct cgroup_subsys_state
*css
,
5650 count
= atomic_read(&task_css_set(current
)->refcount
);
5655 static int current_css_set_cg_links_read(struct seq_file
*seq
, void *v
)
5657 struct cgrp_cset_link
*link
;
5658 struct css_set
*cset
;
5661 name_buf
= kmalloc(NAME_MAX
+ 1, GFP_KERNEL
);
5665 down_read(&css_set_rwsem
);
5667 cset
= rcu_dereference(current
->cgroups
);
5668 list_for_each_entry(link
, &cset
->cgrp_links
, cgrp_link
) {
5669 struct cgroup
*c
= link
->cgrp
;
5671 cgroup_name(c
, name_buf
, NAME_MAX
+ 1);
5672 seq_printf(seq
, "Root %d group %s\n",
5673 c
->root
->hierarchy_id
, name_buf
);
5676 up_read(&css_set_rwsem
);
5681 #define MAX_TASKS_SHOWN_PER_CSS 25
5682 static int cgroup_css_links_read(struct seq_file
*seq
, void *v
)
5684 struct cgroup_subsys_state
*css
= seq_css(seq
);
5685 struct cgrp_cset_link
*link
;
5687 down_read(&css_set_rwsem
);
5688 list_for_each_entry(link
, &css
->cgroup
->cset_links
, cset_link
) {
5689 struct css_set
*cset
= link
->cset
;
5690 struct task_struct
*task
;
5693 seq_printf(seq
, "css_set %p\n", cset
);
5695 list_for_each_entry(task
, &cset
->tasks
, cg_list
) {
5696 if (count
++ > MAX_TASKS_SHOWN_PER_CSS
)
5698 seq_printf(seq
, " task %d\n", task_pid_vnr(task
));
5701 list_for_each_entry(task
, &cset
->mg_tasks
, cg_list
) {
5702 if (count
++ > MAX_TASKS_SHOWN_PER_CSS
)
5704 seq_printf(seq
, " task %d\n", task_pid_vnr(task
));
5708 seq_puts(seq
, " ...\n");
5710 up_read(&css_set_rwsem
);
5714 static u64
releasable_read(struct cgroup_subsys_state
*css
, struct cftype
*cft
)
5716 return (!cgroup_has_tasks(css
->cgroup
) &&
5717 !css_has_online_children(&css
->cgroup
->self
));
5720 static struct cftype debug_files
[] = {
5722 .name
= "taskcount",
5723 .read_u64
= debug_taskcount_read
,
5727 .name
= "current_css_set",
5728 .read_u64
= current_css_set_read
,
5732 .name
= "current_css_set_refcount",
5733 .read_u64
= current_css_set_refcount_read
,
5737 .name
= "current_css_set_cg_links",
5738 .seq_show
= current_css_set_cg_links_read
,
5742 .name
= "cgroup_css_links",
5743 .seq_show
= cgroup_css_links_read
,
5747 .name
= "releasable",
5748 .read_u64
= releasable_read
,
5754 struct cgroup_subsys debug_cgrp_subsys
= {
5755 .css_alloc
= debug_css_alloc
,
5756 .css_free
= debug_css_free
,
5757 .legacy_cftypes
= debug_files
,
5759 #endif /* CONFIG_CGROUP_DEBUG */