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Commit 5300a9b3 authored by Tejun Heo's avatar Tejun Heo
Browse files

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: default avatarTejun Heo <tj@kernel.org>
Reviewed-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: default avatarMichal Hocko <mhocko@suse.cz>
parent a2252180

kernel/cgroup_freezer.c

+40 −2
Original line number Diff line number Diff line
@@ -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,