Messages in this thread | | | Date | Thu, 11 Dec 2008 12:03:07 +0530 | From | Balbir Singh <> | Subject | Re: [RFC][PATCH 2/3] CGroups: Use hierarchy_mutex in memory controller |
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* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2008-12-11 10:05:01]:
> 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)
But then the hierarchy_locks acquired will be different right?
> 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.
Could you please explain the race better?
-- Balbir
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