On Wed, Aug 31, 2011 at 12:21:07PM +0200, Tejun Heo wrote:
> d02f52811d0e "cgroup_freezer: prepare for removal of TIF_FREEZE" moved
> setting of freezer->state into freezer_change_state(); unfortunately,
> while doing so, when it's beginning to freeze tasks, it sets the state
> to CGROUP_FROZEN instead of CGROUP_FREEZING ending up skipping the
> whole freezing state. Fix it.
>
> -v2: Oleg pointed out that re-freezing FROZEN cgroup could increment
> system_freezing_cnt. Fixed.
>
> Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
> Reported-by: Oleg Nesterov <oleg@xxxxxxxxxx>
> Cc: Paul Menage <paul@xxxxxxxxxxxxxx>
> Cc: "Rafael J. Wysocki" <rjw@xxxxxxx>
> ---
> I'm in the process of moving and can only use a quite old laptop. I
> tested compile but couldn't really do much else, so please proceed
> with caution. Oleg, can you please ack the patches if you agree with
> the updated versions?
>
> Thanks.
>
> kernel/cgroup_freezer.c | 20 +++++++++++---------
> 1 file changed, 11 insertions(+), 9 deletions(-)
>
> Index: work/kernel/cgroup_freezer.c
> ===================================================================
> --- work.orig/kernel/cgroup_freezer.c
> +++ work/kernel/cgroup_freezer.c
> @@ -308,24 +308,26 @@ static int freezer_change_state(struct c
> 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);
> - unfreeze_cgroup(cgroup, freezer);
> + if (freezer->state != CGROUP_THAWED) {
> + freezer->state = CGROUP_THAWED;
> + atomic_dec(&system_freezing_cnt);
> + unfreeze_cgroup(cgroup, freezer);
> + }
> break;
> case CGROUP_FROZEN:
> - atomic_inc(&system_freezing_cnt);
> - retval = try_to_freeze_cgroup(cgroup, freezer);
> + if (freezer->state == CGROUP_THAWED) {
> + freezer->state = CGROUP_FREEZING;
> + atomic_inc(&system_freezing_cnt);
> + retval = try_to_freeze_cgroup(cgroup, freezer);
This still doesn't look quite right. If the cgroup is FREEZING it should
also call try_to_freeze_cgroup(). I think this is what's needed:
if (freezer->state == CGROUP_THAWED)
atomic_inc(&system_freezing_cnt);
freezer->state = CGROUP_FREEZING;
retval = try_to_freeze_cgroup(cgroup, freezer);
> + }
> break;
> default:
> BUG();
> }
Cheers,
-Matt Helsley
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