Re: Re: Race condition between putback_lru_page and mem_cgroup_move_list

[kamezawa.hiroyu@jp.fujitsu.com]

>KOSAKI Motohiro wrote:
>> Hi
>> 
>>>> I think this is a race condition if mem_cgroup_move_lists's comment isn't
 right.
>>>> I am not sure that it was already known problem.
>>>>
>>>> mem_cgroup_move_lists assume the appropriate zone's lru lock is already h
eld.
>>>> but putback_lru_page calls mem_cgroup_move_lists without holding lru_lock
.
>>> Hmmm, the comment on mem_cgroup_move_lists() does say this.  Although,
>>> reading thru' the code, I can't see why it requires this.  But then it's
>>> Monday, here...
>> 
>> I also think zone's lru lock is unnecessary.
>> So, I guess below "it" indicate lock_page_cgroup, not zone lru lock.
>> 
>
>We need zone LRU lock, since the reclaim paths hold them. Not sure if I
>understand why you call zone's LRU lock unnecessary, could you elaborate plea
se?
>

I guess the comment should be against mem_cgroup_isolate_pages()...

Thanks,
-Kame

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