Re: [PATCH 0/4] replace cgroup_lock with local lock in memcg

[Glauber Costa <glommer@parallels.com>]

On 11/30/2012 07:52 PM, Tejun Heo wrote:
> Hey, Glauber.
> 
> I don't know enough about memcg to be acking this but overall it looks
> pretty good to me.
> 
> On Fri, Nov 30, 2012 at 05:31:22PM +0400, Glauber Costa wrote:
>> For the problem of attaching tasks, I am using something similar to cpusets:
>> when task attaching starts, we will flip a flag "attach_in_progress", that will
>> be flipped down when it finishes. This way, all readers can know that a task is
>> joining the group and take action accordingly. With this, we can guarantee that
>> the behavior of move_charge_at_immigrate continues safe
> 
> Yeap, attach_in_progress is useful if there are some conditions which
> shouldn't change between ->can_attach() and ->attach().  With the
> immigrate thing gone, this no longer is necessary, right?
> 

Yes and no. While it can help with immigrate, we still have kmem that
needs to be protected against tasks joining.

However, kmem is easier. If attach_in_progress is ever positive, it
means that a task is joining, and it is already unacceptable for kmem -
so we can fail right away.

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