Re: [PATCH pm-freezer 1/4] cgroup_freezer: fix freezer->state setting bug in freezer_change_state()

[Oleg Nesterov <oleg@redhat.com>]

On 08/29, Tejun Heo wrote:
>
> --- work.orig/kernel/cgroup_freezer.c
> +++ work/kernel/cgroup_freezer.c
> @@ -311,14 +311,14 @@ static int freezer_change_state(struct c
>  	if (goal_state == freezer->state)
>  		goto out;
>  
> -	freezer->state = goal_state;
> -
>  	switch (goal_state) {
>  	case CGROUP_THAWED:
> +		freezer->state = CGROUP_THAWED;
>  		atomic_dec(&system_freezing_cnt);
>  		unfreeze_cgroup(cgroup, freezer);
>  		break;
>  	case CGROUP_FROZEN:
> +		freezer->state = CGROUP_FREEZING;

At first glance, this is correct. I'll try to recheck.

But,

>  		atomic_inc(&system_freezing_cnt);

iiuc this becomes wrong... Suppose a user writes "FROZEN" twice,
before freezer->state becomes CGROUP_FROZEN.

I think we should actually fix the "goal_state == freezer->state"
check above.

Oleg.