Messages in this thread | | | Date | Thu, 25 Jun 2009 14:28:09 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 0/2] memcg: cgroup fix rmdir hang |
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On Tue, 23 Jun 2009 16:07:20 +0900 KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> previous discussion was this => http://marc.info/?t=124478543600001&r=1&w=2 > > This patch tries to fix problem as > - rmdir can sleep very very long if swap entry is shared between multiple > cgroups > > Now, cgroup's rmdir path does following > > == > again: > check there are no tasks and children group. > call pre_destroy() > check css's refcnt > if (refcnt > 0) { > sleep until css's refcnt goes down to 0. > goto again > } > == > > Unfortunately, memory cgroup does following at charge. > > css_get(&memcg->css) > .... > charge(memcg) (increase USAGE) > ... > And this "memcg" is not necessary to include the caller, task. > > pre_destroy() tries to reduce memory usage until USAGE goes down to 0. > Then, there is a race that > - css's refcnt > 0 (and memcg's usage > 0) > - rmdir() caller sleeps until css->refcnt goes down 0. > - But to make css->refcnt be 0, pre_destroy() should be called again. > > This patch tries to fix this in asyhcnrounos way (i.e. without big lock.) > Any comments are welcome. >
Do you believe that these fixes should be backported into 2.6.30.x?
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