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![Ben Blum](/assets/img/avatar_default.png)
Add cgroup subsystem callbacks for per-thread attachment in atomic contexts Add can_attach_task(), pre_attach(), and attach_task() as new callbacks for cgroups's subsystem interface. Unlike can_attach and attach, these are for per-thread operations, to be called potentially many times when attaching an entire threadgroup. Also, the old "bool threadgroup" interface is removed, as replaced by this. All subsystems are modified for the new interface - of note is cpuset, which requires from/to nodemasks for attach to be globally scoped (though per-cpuset would work too) to persist from its pre_attach to attach_task and attach. This is a pre-patch for cgroup-procs-writable.patch. Signed-off-by: Ben Blum <bblum@andrew.cmu.edu> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Matt Helsley <matthltc@us.ibm.com> Reviewed-by: Paul Menage <menage@google.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: Miao Xie <miaox@cn.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
390 lines
9.4 KiB
C
390 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/module.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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static inline int __cgroup_freezing_or_frozen(struct task_struct *task)
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{
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enum freezer_state state = task_freezer(task)->state;
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return (state == CGROUP_FREEZING) || (state == CGROUP_FROZEN);
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}
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int cgroup_freezing_or_frozen(struct task_struct *task)
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{
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int result;
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task_lock(task);
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result = __cgroup_freezing_or_frozen(task);
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task_unlock(task);
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return result;
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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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* cgroup_freezing_or_frozen():
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* task->alloc_lock (to get task's cgroup)
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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_process(), 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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kfree(cgroup_freezer(cgroup));
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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 task_struct *task)
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{
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struct freezer *freezer;
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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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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 int freezer_can_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
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{
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rcu_read_lock();
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if (__cgroup_freezing_or_frozen(tsk)) {
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rcu_read_unlock();
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return -EBUSY;
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}
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rcu_read_unlock();
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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, true);
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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 (frozen(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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freezer->state = CGROUP_FREEZING;
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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, true))
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continue;
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if (frozen(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_process(task);
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}
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cgroup_iter_end(cgroup, &it);
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freezer->state = CGROUP_THAWED;
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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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if (goal_state == freezer->state)
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goto out;
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switch (goal_state) {
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case 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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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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out:
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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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.can_attach_task = freezer_can_attach_task,
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.pre_attach = NULL,
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.attach_task = NULL,
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.attach = NULL,
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.fork = freezer_fork,
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.exit = NULL,
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};
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