linux-kernel - Re: [PATCH RFC] memcg: fix drain_all

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Date:	Tue, 9 Aug 2011 18:53:13 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	Johannes Weiner <jweiner@...hat.com>, linux-mm@...ck.org,
	Balbir Singh <bsingharora@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC] memcg: fix drain_all_stock crash

On Tue, 9 Aug 2011 11:45:03 +0200
Michal Hocko <mhocko@...e.cz> wrote:

> On Tue 09-08-11 18:32:16, KAMEZAWA Hiroyuki wrote:
> > On Tue, 9 Aug 2011 11:31:50 +0200
> > Michal Hocko <mhocko@...e.cz> wrote:
> > 
> > > What do you think about the half backed patch bellow? I didn't manage to
> > > test it yet but I guess it should help. I hate asymmetry of drain_lock
> > > locking (it is acquired somewhere else than it is released which is
> > > not). I will think about a nicer way how to do it.
> > > Maybe I should also split the rcu part in a separate patch.
> > > 
> > > What do you think?
> > 
> > 
> > I'd like to revert 8521fc50 first and consider total design change
> > rather than ad-hoc fix.
> 
> Agreed. Revert should go into 3.0 stable as well. Although the global
> mutex is buggy we have that behavior for a long time without any reports.
> We should address it but it can wait for 3.2.
> 

What "buggy" means here ? "problematic" or "cause OOps ?"

> > Personally, I don't like to have spin-lock in per-cpu area.
> 
> spinlock is not that different from what we already have with the bit
> lock.

maybe. The best is lockless style...but pointer in percpu cache is problem..

Thanks,
-Kame


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