On Wed 12-06-13 21:04:58, Tejun Heo wrote:
[...]
> +/**
> + * cgroup_destroy_locked - the first stage of cgroup destruction
> + * @cgrp: cgroup to be destroyed
> + *
> + * css's make use of percpu refcnts whose killing latency shouldn't be
> + * exposed to userland and are RCU protected. Also, cgroup core needs to
> + * guarantee that css_tryget() won't succeed by the time ->css_offline() is
> + * invoked. To satisfy all the requirements, destruction is implemented in
> + * the following two steps.
> + *
> + * s1. Verify @cgrp can be destroyed and mark it dying. Remove all
> + * userland visible parts and start killing the percpu refcnts of
> + * css's. Set up so that the next stage will be kicked off once all
> + * the percpu refcnts are confirmed to be killed.
> + *
> + * s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the
> + * rest of destruction. Once all cgroup references are gone, the
> + * cgroup is RCU-freed.
> + *
> + * This function implements s1. After this step, @cgrp is gone as far as
> + * the userland is concerned and a new cgroup with the same name may be
> + * created. As cgroup doesn't care about the names internally, this
> + * doesn't cause any problem.
Glauber is this asumption correct for kmem caches naming scheme?
I guess it should, but I would rather be sure this won't blow up later
specially when caches might live longer than css_offline.
> + */
> static int cgroup_destroy_locked(struct cgroup *cgrp)
> __releases(&cgroup_mutex) __acquires(&cgroup_mutex)
> {
--
Michal Hocko
SUSE Labs
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