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SubjectRe: [PATCH 7/9] cgroup_freezer: introduce CGROUP_FREEZING_[SELF|PARENT]
On Sat 03-11-12 01:38:33, Tejun Heo wrote:
> Introduce FREEZING_SELF and FREEZING_PARENT and make FREEZING OR of
> the two flags. This is to prepare for full hierarchy support.
>
> freezer_apply_date() is updated such that it can handle setting and
> clearing of both flags. The two flags are also exposed to userland
> via read-only files self_freezing and parent_freezing.
>
> Other than the added cgroupfs files, this patch doesn't introduce any
> behavior change.

OK, I can imagine that this might be useful to find the first parent
group that needs to be thawed to unfreeze the group I am interested
in. Could you also update Documentation/cgroups/freezer-subsystem.txt to
clarify the intended usage?

Minor nit. Same as mentioned in the previous patch freezer_apply_state
should get enum freezer_state_flags state parameter.

> Signed-off-by: Tejun Heo <tj@kernel.org>

Reviewed-by: Michal Hocko <mhocko@suse.cz>

> ---
> kernel/cgroup_freezer.c | 55 ++++++++++++++++++++++++++++++++++++++++++-------
> 1 file changed, 47 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
> index e76aa9f..b8ad93c 100644
> --- a/kernel/cgroup_freezer.c
> +++ b/kernel/cgroup_freezer.c
> @@ -23,8 +23,12 @@
> #include <linux/seq_file.h>
>
> enum freezer_state_flags {
> - CGROUP_FREEZING = (1 << 1), /* this freezer is freezing */
> + 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 */
> +
> + /* mask for all FREEZING flags */
> + CGROUP_FREEZING = CGROUP_FREEZING_SELF | CGROUP_FREEZING_PARENT,
> };
>
> struct freezer {
> @@ -245,8 +249,13 @@ static void unfreeze_cgroup(struct freezer *freezer)
> * freezer_apply_state - apply state change to a single cgroup_freezer
> * @freezer: freezer to apply state change to
> * @freeze: whether to freeze or unfreeze
> + * @state: CGROUP_FREEZING_* flag to set or clear
> + *
> + * Set or clear @state on @cgroup according to @freeze, and perform
> + * freezing or thawing as necessary.
> */
> -static void freezer_apply_state(struct freezer *freezer, bool freeze)
> +static void freezer_apply_state(struct freezer *freezer, bool freeze,
> + unsigned int state)
> {
> /* also synchronizes against task migration, see freezer_attach() */
> lockdep_assert_held(&freezer->lock);
> @@ -254,13 +263,19 @@ static void freezer_apply_state(struct freezer *freezer, bool freeze)
> if (freeze) {
> if (!(freezer->state & CGROUP_FREEZING))
> atomic_inc(&system_freezing_cnt);
> - freezer->state |= CGROUP_FREEZING;
> + freezer->state |= state;
> freeze_cgroup(freezer);
> } else {
> - if (freezer->state & CGROUP_FREEZING)
> - atomic_dec(&system_freezing_cnt);
> - freezer->state &= ~(CGROUP_FREEZING | CGROUP_FROZEN);
> - unfreeze_cgroup(freezer);
> + bool was_freezing = freezer->state & CGROUP_FREEZING;
> +
> + freezer->state &= ~state;
> +
> + if (!(freezer->state & CGROUP_FREEZING)) {
> + if (was_freezing)
> + atomic_dec(&system_freezing_cnt);
> + freezer->state &= ~CGROUP_FROZEN;
> + unfreeze_cgroup(freezer);
> + }
> }
> }
>
> @@ -275,7 +290,7 @@ static void freezer_change_state(struct freezer *freezer, bool freeze)
> {
> /* update @freezer */
> spin_lock_irq(&freezer->lock);
> - freezer_apply_state(freezer, freeze);
> + freezer_apply_state(freezer, freeze, CGROUP_FREEZING_SELF);
> spin_unlock_irq(&freezer->lock);
> }
>
> @@ -295,6 +310,20 @@ static int freezer_write(struct cgroup *cgroup, struct cftype *cft,
> return 0;
> }
>
> +static u64 freezer_self_freezing_read(struct cgroup *cgroup, struct cftype *cft)
> +{
> + struct freezer *freezer = cgroup_freezer(cgroup);
> +
> + return (bool)(freezer->state & CGROUP_FREEZING_SELF);
> +}
> +
> +static u64 freezer_parent_freezing_read(struct cgroup *cgroup, struct cftype *cft)
> +{
> + struct freezer *freezer = cgroup_freezer(cgroup);
> +
> + return (bool)(freezer->state & CGROUP_FREEZING_PARENT);
> +}
> +
> static struct cftype files[] = {
> {
> .name = "state",
> @@ -302,6 +331,16 @@ static struct cftype files[] = {
> .read_seq_string = freezer_read,
> .write_string = freezer_write,
> },
> + {
> + .name = "self_freezing",
> + .flags = CFTYPE_NOT_ON_ROOT,
> + .read_u64 = freezer_self_freezing_read,
> + },
> + {
> + .name = "parent_freezing",
> + .flags = CFTYPE_NOT_ON_ROOT,
> + .read_u64 = freezer_parent_freezing_read,
> + },
> { } /* terminate */
> };
>
> --
> 1.7.11.7
>

--
Michal Hocko
SUSE Labs


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