linux-kernel - Re: [PATCH 06/11] memcg: kmem controller infrastructure

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Message-ID: <alpine.DEB.2.00.1206271239340.22162@chino.kir.corp.google.com>
Date:	Wed, 27 Jun 2012 12:46:08 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Glauber Costa <glommer@...allels.com>
cc:	cgroups@...r.kernel.org, linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	Pekka Enberg <penberg@...nel.org>,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	Christoph Lameter <cl@...ux.com>, devel@...nvz.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Tejun Heo <tj@...nel.org>,
	Pekka Enberg <penberg@...helsinki.fi>
Subject: Re: [PATCH 06/11] memcg: kmem controller infrastructure

On Wed, 27 Jun 2012, Glauber Costa wrote:

> > > Nothing, but I also don't see how to prevent that.
> > 
> > You can test for current->flags & PF_KTHREAD following the check for
> > in_interrupt() and return true, it's what you were trying to do with the
> > check for !current->mm.
> > 
> 
> am I right to believe that if not in interrupt context - already ruled out -
> and !(current->flags & PF_KTHREAD), I am guaranteed to have a mm context, and
> thus, don't need to test against it ?
> 

No, because an mm may have been detached in the exit path by running 
exit_mm().  We'd certainly hope that there are no slab allocations 
following that point, though, but you'd still need to test current->mm.
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