Messages in this thread | | | Date | Sat, 6 Dec 2008 12:35:03 +0900 | From | Daisuke Nishimura <> | Subject | Re: [RFC][PATCH -mmotm 3/4] memcg: avoid dead lock caused by racebetween oom and cpuset_attach |
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On Fri, 5 Dec 2008 22:27:10 +0900 (JST) "KAMEZAWA Hiroyuki" <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> Daisuke Nishimura said: > > mpol_rebind_mm(), which can be called from cpuset_attach(), does > > down_write(mm->mmap_sem). > > This means down_write(mm->mmap_sem) can be called under cgroup_mutex. > > > > OTOH, page fault path does down_read(mm->mmap_sem) and calls > > mem_cgroup_try_charge_xxx(), > > which may eventually calls mem_cgroup_out_of_memory(). And > > mem_cgroup_out_of_memory() > > calls cgroup_lock(). > > This means cgroup_lock() can be called under down_read(mm->mmap_sem). > > > good catch. > Thanks.
> > If those two paths race, dead lock can happen. > > > > This patch avoid this dead lock by: > > - remove cgroup_lock() from mem_cgroup_out_of_memory(). > agree to this. > > > - define new mutex (memcg_tasklist) and serialize mem_cgroup_move_task() > > (->attach handler of memory cgroup) and mem_cgroup_out_of_memory. > > > Hmm...seems temporal fix (and adding new global lock...) > But ok, we need fix. revist this later. > I agree.
> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu,com> > Thank you.
Daisuke Nishimura.
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