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![Linus Torvalds](/assets/img/avatar_default.png)
* 'for-3.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (21 commits)
cgroup: fix to allow mounting a hierarchy by name
cgroup: move assignement out of condition in cgroup_attach_proc()
cgroup: Remove task_lock() from cgroup_post_fork()
cgroup: add sparse annotation to cgroup_iter_start() and cgroup_iter_end()
cgroup: mark cgroup_rmdir_waitq and cgroup_attach_proc() as static
cgroup: only need to check oldcgrp==newgrp once
cgroup: remove redundant get/put of task struct
cgroup: remove redundant get/put of old css_set from migrate
cgroup: Remove unnecessary task_lock before fetching css_set on migration
cgroup: Drop task_lock(parent) on cgroup_fork()
cgroups: remove redundant get/put of css_set from css_set_check_fetched()
resource cgroups: remove bogus cast
cgroup: kill subsys->can_attach_task(), pre_attach() and attach_task()
cgroup, cpuset: don't use ss->pre_attach()
cgroup: don't use subsys->can_attach_task() or ->attach_task()
cgroup: introduce cgroup_taskset and use it in subsys->can_attach(), cancel_attach() and attach()
cgroup: improve old cgroup handling in cgroup_attach_proc()
cgroup: always lock threadgroup during migration
threadgroup: extend threadgroup_lock() to cover exit and exec
threadgroup: rename signal->threadgroup_fork_lock to ->group_rwsem
...
Fix up conflict in kernel/cgroup.c due to commit e0197aae59
: "cgroups:
fix a css_set not found bug in cgroup_attach_proc" that already
mentioned that the bug is fixed (differently) in Tejun's cgroup
patchset. This one, in other words.
384 lines
9.4 KiB
C
384 lines
9.4 KiB
C
/*
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* cgroup_freezer.c - control group freezer subsystem
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*
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* Copyright IBM Corporation, 2007
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*
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* Author : Cedric Le Goater <clg@fr.ibm.com>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of version 2.1 of the GNU Lesser General Public License
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* as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it would be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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*/
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#include <linux/export.h>
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#include <linux/slab.h>
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#include <linux/cgroup.h>
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#include <linux/fs.h>
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#include <linux/uaccess.h>
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#include <linux/freezer.h>
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#include <linux/seq_file.h>
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enum freezer_state {
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CGROUP_THAWED = 0,
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CGROUP_FREEZING,
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CGROUP_FROZEN,
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};
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struct freezer {
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struct cgroup_subsys_state css;
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enum freezer_state state;
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spinlock_t lock; /* protects _writes_ to state */
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};
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static inline struct freezer *cgroup_freezer(
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struct cgroup *cgroup)
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{
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return container_of(
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cgroup_subsys_state(cgroup, freezer_subsys_id),
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struct freezer, css);
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}
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static inline struct freezer *task_freezer(struct task_struct *task)
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{
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return container_of(task_subsys_state(task, freezer_subsys_id),
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struct freezer, css);
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}
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bool cgroup_freezing(struct task_struct *task)
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{
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enum freezer_state state;
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bool ret;
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rcu_read_lock();
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state = task_freezer(task)->state;
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ret = state == CGROUP_FREEZING || state == CGROUP_FROZEN;
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rcu_read_unlock();
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return ret;
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}
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/*
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* cgroups_write_string() limits the size of freezer state strings to
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* CGROUP_LOCAL_BUFFER_SIZE
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*/
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static const char *freezer_state_strs[] = {
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"THAWED",
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"FREEZING",
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"FROZEN",
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};
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/*
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* State diagram
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* Transitions are caused by userspace writes to the freezer.state file.
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* The values in parenthesis are state labels. The rest are edge labels.
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*
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* (THAWED) --FROZEN--> (FREEZING) --FROZEN--> (FROZEN)
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* ^ ^ | |
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* | \_______THAWED_______/ |
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* \__________________________THAWED____________/
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*/
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struct cgroup_subsys freezer_subsys;
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/* Locks taken and their ordering
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* ------------------------------
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* cgroup_mutex (AKA cgroup_lock)
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* freezer->lock
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* css_set_lock
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* task->alloc_lock (AKA task_lock)
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* task->sighand->siglock
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*
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* cgroup code forces css_set_lock to be taken before task->alloc_lock
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*
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* freezer_create(), freezer_destroy():
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* cgroup_mutex [ by cgroup core ]
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*
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* freezer_can_attach():
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* cgroup_mutex (held by caller of can_attach)
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*
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* freezer_fork() (preserving fork() performance means can't take cgroup_mutex):
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* freezer->lock
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* sighand->siglock (if the cgroup is freezing)
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*
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* freezer_read():
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* cgroup_mutex
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* freezer->lock
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* write_lock css_set_lock (cgroup iterator start)
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* task->alloc_lock
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* read_lock css_set_lock (cgroup iterator start)
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*
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* freezer_write() (freeze):
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* cgroup_mutex
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* freezer->lock
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* write_lock css_set_lock (cgroup iterator start)
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* task->alloc_lock
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* read_lock css_set_lock (cgroup iterator start)
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* sighand->siglock (fake signal delivery inside freeze_task())
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*
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* freezer_write() (unfreeze):
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* cgroup_mutex
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* freezer->lock
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* write_lock css_set_lock (cgroup iterator start)
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* task->alloc_lock
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* read_lock css_set_lock (cgroup iterator start)
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* task->alloc_lock (inside __thaw_task(), prevents race with refrigerator())
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* sighand->siglock
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*/
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static struct cgroup_subsys_state *freezer_create(struct cgroup_subsys *ss,
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struct cgroup *cgroup)
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{
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struct freezer *freezer;
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freezer = kzalloc(sizeof(struct freezer), GFP_KERNEL);
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if (!freezer)
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return ERR_PTR(-ENOMEM);
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spin_lock_init(&freezer->lock);
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freezer->state = CGROUP_THAWED;
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return &freezer->css;
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}
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static void freezer_destroy(struct cgroup_subsys *ss,
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struct cgroup *cgroup)
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{
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struct freezer *freezer = cgroup_freezer(cgroup);
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if (freezer->state != CGROUP_THAWED)
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atomic_dec(&system_freezing_cnt);
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kfree(freezer);
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}
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/* task is frozen or will freeze immediately when next it gets woken */
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static bool is_task_frozen_enough(struct task_struct *task)
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{
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return frozen(task) ||
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(task_is_stopped_or_traced(task) && freezing(task));
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}
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/*
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* The call to cgroup_lock() in the freezer.state write method prevents
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* a write to that file racing against an attach, and hence the
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* can_attach() result will remain valid until the attach completes.
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*/
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static int freezer_can_attach(struct cgroup_subsys *ss,
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struct cgroup *new_cgroup,
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struct cgroup_taskset *tset)
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{
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struct freezer *freezer;
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struct task_struct *task;
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/*
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* Anything frozen can't move or be moved to/from.
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*/
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cgroup_taskset_for_each(task, new_cgroup, tset)
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if (cgroup_freezing(task))
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return -EBUSY;
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freezer = cgroup_freezer(new_cgroup);
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if (freezer->state != CGROUP_THAWED)
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return -EBUSY;
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return 0;
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}
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static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task)
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{
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struct freezer *freezer;
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/*
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* No lock is needed, since the task isn't on tasklist yet,
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* so it can't be moved to another cgroup, which means the
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* freezer won't be removed and will be valid during this
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* function call. Nevertheless, apply RCU read-side critical
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* section to suppress RCU lockdep false positives.
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*/
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rcu_read_lock();
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freezer = task_freezer(task);
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rcu_read_unlock();
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/*
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* The root cgroup is non-freezable, so we can skip the
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* following check.
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*/
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if (!freezer->css.cgroup->parent)
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return;
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spin_lock_irq(&freezer->lock);
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BUG_ON(freezer->state == CGROUP_FROZEN);
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/* Locking avoids race with FREEZING -> THAWED transitions. */
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if (freezer->state == CGROUP_FREEZING)
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freeze_task(task);
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spin_unlock_irq(&freezer->lock);
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}
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/*
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* caller must hold freezer->lock
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*/
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static void update_if_frozen(struct cgroup *cgroup,
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struct freezer *freezer)
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{
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struct cgroup_iter it;
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struct task_struct *task;
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unsigned int nfrozen = 0, ntotal = 0;
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enum freezer_state old_state = freezer->state;
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cgroup_iter_start(cgroup, &it);
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while ((task = cgroup_iter_next(cgroup, &it))) {
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ntotal++;
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if (freezing(task) && is_task_frozen_enough(task))
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nfrozen++;
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}
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if (old_state == CGROUP_THAWED) {
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BUG_ON(nfrozen > 0);
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} else if (old_state == CGROUP_FREEZING) {
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if (nfrozen == ntotal)
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freezer->state = CGROUP_FROZEN;
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} else { /* old_state == CGROUP_FROZEN */
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BUG_ON(nfrozen != ntotal);
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}
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cgroup_iter_end(cgroup, &it);
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}
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static int freezer_read(struct cgroup *cgroup, struct cftype *cft,
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struct seq_file *m)
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{
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struct freezer *freezer;
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enum freezer_state state;
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if (!cgroup_lock_live_group(cgroup))
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return -ENODEV;
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freezer = cgroup_freezer(cgroup);
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spin_lock_irq(&freezer->lock);
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state = freezer->state;
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if (state == CGROUP_FREEZING) {
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/* We change from FREEZING to FROZEN lazily if the cgroup was
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* only partially frozen when we exitted write. */
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update_if_frozen(cgroup, freezer);
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state = freezer->state;
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}
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spin_unlock_irq(&freezer->lock);
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cgroup_unlock();
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seq_puts(m, freezer_state_strs[state]);
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seq_putc(m, '\n');
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return 0;
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}
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static int try_to_freeze_cgroup(struct cgroup *cgroup, struct freezer *freezer)
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{
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struct cgroup_iter it;
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struct task_struct *task;
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unsigned int num_cant_freeze_now = 0;
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cgroup_iter_start(cgroup, &it);
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while ((task = cgroup_iter_next(cgroup, &it))) {
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if (!freeze_task(task))
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continue;
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if (is_task_frozen_enough(task))
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continue;
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if (!freezing(task) && !freezer_should_skip(task))
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num_cant_freeze_now++;
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}
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cgroup_iter_end(cgroup, &it);
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return num_cant_freeze_now ? -EBUSY : 0;
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}
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static void unfreeze_cgroup(struct cgroup *cgroup, struct freezer *freezer)
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{
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struct cgroup_iter it;
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struct task_struct *task;
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cgroup_iter_start(cgroup, &it);
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while ((task = cgroup_iter_next(cgroup, &it)))
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__thaw_task(task);
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cgroup_iter_end(cgroup, &it);
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}
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static int freezer_change_state(struct cgroup *cgroup,
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enum freezer_state goal_state)
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{
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struct freezer *freezer;
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int retval = 0;
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freezer = cgroup_freezer(cgroup);
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spin_lock_irq(&freezer->lock);
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update_if_frozen(cgroup, freezer);
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switch (goal_state) {
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case CGROUP_THAWED:
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if (freezer->state != CGROUP_THAWED)
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atomic_dec(&system_freezing_cnt);
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freezer->state = CGROUP_THAWED;
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unfreeze_cgroup(cgroup, freezer);
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break;
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case CGROUP_FROZEN:
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if (freezer->state == CGROUP_THAWED)
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atomic_inc(&system_freezing_cnt);
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freezer->state = CGROUP_FREEZING;
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retval = try_to_freeze_cgroup(cgroup, freezer);
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break;
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default:
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BUG();
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}
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spin_unlock_irq(&freezer->lock);
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return retval;
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}
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static int freezer_write(struct cgroup *cgroup,
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struct cftype *cft,
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const char *buffer)
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{
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int retval;
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enum freezer_state goal_state;
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if (strcmp(buffer, freezer_state_strs[CGROUP_THAWED]) == 0)
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goal_state = CGROUP_THAWED;
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else if (strcmp(buffer, freezer_state_strs[CGROUP_FROZEN]) == 0)
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goal_state = CGROUP_FROZEN;
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else
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return -EINVAL;
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if (!cgroup_lock_live_group(cgroup))
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return -ENODEV;
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retval = freezer_change_state(cgroup, goal_state);
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cgroup_unlock();
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return retval;
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}
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static struct cftype files[] = {
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{
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.name = "state",
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.read_seq_string = freezer_read,
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.write_string = freezer_write,
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},
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};
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static int freezer_populate(struct cgroup_subsys *ss, struct cgroup *cgroup)
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{
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if (!cgroup->parent)
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return 0;
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return cgroup_add_files(cgroup, ss, files, ARRAY_SIZE(files));
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}
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struct cgroup_subsys freezer_subsys = {
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.name = "freezer",
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.create = freezer_create,
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.destroy = freezer_destroy,
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.populate = freezer_populate,
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.subsys_id = freezer_subsys_id,
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.can_attach = freezer_can_attach,
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.fork = freezer_fork,
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};
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