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cgroup_freezer: add ->post_create() and ->pre_destroy() and track online state 

A cgroup is online and visible to iteration between ->post_create()
and ->pre_destroy().  This patch introduces CGROUP_FREEZER_ONLINE and
toggles it from the newly added freezer_post_create() and
freezer_pre_destroy() while holding freezer->lock such that a
cgroup_freezer can be reilably distinguished to be online.  This will
be used by full hierarchy support.

ONLINE test is added to freezer_apply_state() but it currently doesn't
make any difference as freezer_write() can only be called for an
online cgroup.

Adjusting system_freezing_cnt on destruction is moved from
freezer_destroy() to the new freezer_pre_destroy() for consistency.

This patch doesn't introduce any noticeable behavior change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
This commit is contained in:
Tejun Heo 2012-11-09 09:12:30 -08:00
parent a225218060
commit 5300a9b348
1 changed files with 40 additions and 2 deletions
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42
kernel/cgroup_freezer.c
View File

@ -23,6 +23,7 @@
#include <linux/seq_file.h>
enum freezer_state_flags {
CGROUP_FREEZER_ONLINE = (1 << 0), /* freezer is fully online */
CGROUP_FREEZING_SELF = (1 << 1), /* this freezer is freezing */
CGROUP_FREEZING_PARENT = (1 << 2), /* the parent freezer is freezing */
CGROUP_FROZEN = (1 << 3), /* this and its descendants frozen */
@ -98,13 +99,45 @@ static struct cgroup_subsys_state *freezer_create(struct cgroup *cgroup)
return &freezer->css;
}
static void freezer_destroy(struct cgroup *cgroup)
/**
* freezer_post_create - commit creation of a freezer cgroup
* @cgroup: cgroup being created
*
* We're committing to creation of @cgroup. Mark it online.
*/
static void freezer_post_create(struct cgroup *cgroup)
{
struct freezer *freezer = cgroup_freezer(cgroup);
spin_lock_irq(&freezer->lock);
freezer->state |= CGROUP_FREEZER_ONLINE;
spin_unlock_irq(&freezer->lock);
}
/**
* freezer_pre_destroy - initiate destruction of @cgroup
* @cgroup: cgroup being destroyed
*
* @cgroup is going away. Mark it dead and decrement system_freezing_count
* if it was holding one.
*/
static void freezer_pre_destroy(struct cgroup *cgroup)
{
struct freezer *freezer = cgroup_freezer(cgroup);
spin_lock_irq(&freezer->lock);
if (freezer->state & CGROUP_FREEZING)
atomic_dec(&system_freezing_cnt);
kfree(freezer);
freezer->state = 0;
spin_unlock_irq(&freezer->lock);
}
static void freezer_destroy(struct cgroup *cgroup)
{
kfree(cgroup_freezer(cgroup));
}
/*
@ -260,6 +293,9 @@ static void freezer_apply_state(struct freezer *freezer, bool freeze,
/* also synchronizes against task migration, see freezer_attach() */
lockdep_assert_held(&freezer->lock);
if (!(freezer->state & CGROUP_FREEZER_ONLINE))
return;
if (freeze) {
if (!(freezer->state & CGROUP_FREEZING))
atomic_inc(&system_freezing_cnt);
@ -347,6 +383,8 @@ static struct cftype files[] = {
struct cgroup_subsys freezer_subsys = {
.name = "freezer",
.create = freezer_create,
.post_create = freezer_post_create,
.pre_destroy = freezer_pre_destroy,
.destroy = freezer_destroy,
.subsys_id = freezer_subsys_id,
.attach = freezer_attach,