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DateThu, 11 Dec 2008 10:05:01 +0900
FromKAMEZAWA Hiroyuki <>
SubjectRe: [RFC][PATCH 2/3] CGroups: Use hierarchy_mutex in memory controller
On Wed, 10 Dec 2008 16:52:57 -0800
Paul Menage <menage@google.com> wrote:

> On Wed, Dec 10, 2008 at 4:49 PM, KAMEZAWA Hiroyuki
> <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> >
> > an operation like rmdir() in somewhere.
> > hierarchy_lock for A (acquired)
> > hierarchy_lock for B (waiting)
> >
> > in subsys A.
> > mmap_sem (acquired)
> > hierarchy_lock for A (waiting)
> > in subsys B.
> > hierarchy_lock for B (aquired)
> > mmap_sem (waiting)
> >
>
> That's a valid deadlock - you'd need to require the mmap_sem nests
> either inside all hierarchy_mutexes or else outside all of them.
>
This was a found dead lock between memcg and cpuset.

another one was

an operation like rmdir() in somewhere.
hierarchy_lock for memcg (acquired)
hierarchy_lock for B (waiting)

in subsys B.
hierarchy_lock for B (aquired)
have to do some memory reclaim -> hierarchy_lock for memcg (waiting)

I have no objections to hierarchy_lock itself but calling context to memcg is very
complicated and simple replace of these locks will be just a small help.

-Kame



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