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SubjectRe: [PATCH 5/9] cgroup_freezer: prepare freezer_change_state() for full hierarchy support
On Sat 03-11-12 01:38:31, Tejun Heo wrote:
> * Make freezer_change_state() take bool @freeze instead of enum
> freezer_state.
>
> * Separate out freezer_apply_state() out of freezer_change_state().
> This makes freezer_change_state() a rather silly thin wrapper. It
> will be filled with hierarchy handling later on.
>
> This patch doesn't introduce any behavior change.
>
> Signed-off-by: Tejun Heo <tj@kernel.org>

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

> ---
> kernel/cgroup_freezer.c | 48 ++++++++++++++++++++++++++++++------------------
> 1 file changed, 30 insertions(+), 18 deletions(-)
>
> diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
> index 975b3d8..2690830 100644
> --- a/kernel/cgroup_freezer.c
> +++ b/kernel/cgroup_freezer.c
> @@ -247,45 +247,57 @@ static void unfreeze_cgroup(struct freezer *freezer)
> cgroup_iter_end(cgroup, &it);
> }
>
> -static void freezer_change_state(struct freezer *freezer,
> - enum freezer_state goal_state)
> +/**
> + * freezer_apply_state - apply state change to a single cgroup_freezer
> + * @freezer: freezer to apply state change to
> + * @freeze: whether to freeze or unfreeze
> + */
> +static void freezer_apply_state(struct freezer *freezer, bool freeze)
> {
> /* also synchronizes against task migration, see freezer_attach() */
> - spin_lock_irq(&freezer->lock);
> + lockdep_assert_held(&freezer->lock);
>
> - switch (goal_state) {
> - case CGROUP_THAWED:
> - if (freezer->state != CGROUP_THAWED)
> - atomic_dec(&system_freezing_cnt);
> - freezer->state = CGROUP_THAWED;
> - unfreeze_cgroup(freezer);
> - break;
> - case CGROUP_FROZEN:
> + if (freeze) {
> if (freezer->state == CGROUP_THAWED)
> atomic_inc(&system_freezing_cnt);
> freezer->state = CGROUP_FREEZING;
> freeze_cgroup(freezer);
> - break;
> - default:
> - BUG();
> + } else {
> + if (freezer->state != CGROUP_THAWED)
> + atomic_dec(&system_freezing_cnt);
> + freezer->state = CGROUP_THAWED;
> + unfreeze_cgroup(freezer);
> }
> +}
>
> +/**
> + * freezer_change_state - change the freezing state of a cgroup_freezer
> + * @freezer: freezer of interest
> + * @freeze: whether to freeze or thaw
> + *
> + * Freeze or thaw @cgroup according to @freeze.
> + */
> +static void freezer_change_state(struct freezer *freezer, bool freeze)
> +{
> + /* update @freezer */
> + spin_lock_irq(&freezer->lock);
> + freezer_apply_state(freezer, freeze);
> spin_unlock_irq(&freezer->lock);
> }
>
> static int freezer_write(struct cgroup *cgroup, struct cftype *cft,
> const char *buffer)
> {
> - enum freezer_state goal_state;
> + bool freeze;
>
> if (strcmp(buffer, freezer_state_strs[CGROUP_THAWED]) == 0)
> - goal_state = CGROUP_THAWED;
> + freeze = false;
> else if (strcmp(buffer, freezer_state_strs[CGROUP_FROZEN]) == 0)
> - goal_state = CGROUP_FROZEN;
> + freeze = true;
> else
> return -EINVAL;
>
> - freezer_change_state(cgroup_freezer(cgroup), goal_state);
> + freezer_change_state(cgroup_freezer(cgroup), freeze);
> return 0;
> }
>
> --
> 1.7.11.7
>

--
Michal Hocko
SUSE Labs


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