Re: [PATCH 1/6] cgroup_freezer: fix freezer->state setting bug infreezer_change_state()

[Oleg Nesterov]

On 09/03, Tejun Heo wrote:
>
> @@ -308,24 +308,24 @@ static int freezer_change_state(struct cgroup *cgroup,
>  	spin_lock_irq(&freezer->lock);
>  
>  	update_if_frozen(cgroup, freezer);
> -	if (goal_state == freezer->state)
> -		goto out;
> -
> -	freezer->state = goal_state;
>  
>  	switch (goal_state) {
>  	case CGROUP_THAWED:
> -		atomic_dec(&system_freezing_cnt);
> +		if (freezer->state != CGROUP_THAWED)
> +			atomic_dec(&system_freezing_cnt);
> +		freezer->state = CGROUP_THAWED;
>  		unfreeze_cgroup(cgroup, freezer);
>  		break;
>  	case CGROUP_FROZEN:
> -		atomic_inc(&system_freezing_cnt);
> +		if (freezer->state == CGROUP_THAWED)
> +			atomic_inc(&system_freezing_cnt);
> +		freezer->state = CGROUP_FREEZING;
>  		retval = try_to_freeze_cgroup(cgroup, freezer);

Cough. Now it doesn't look right to me ;)

If the user write "FROZEN" into the control file, we should not
turn the CGROUP_FROZEN state into CGROUP_FREEZING. Probably this
is harmless, but this looks wrong and this doesn't match the
current behaviour, user-visible change.

Oleg.

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