Message-ID: <1351241323.12171.43.camel@twins>
Subject: Re: [patch for-3.7] mm, mempolicy: fix printing stack contents in
 numa_maps
From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: David Rientjes <rientjes@google.com>,
        Sasha Levin <levinsasha928@gmail.com>, Mel Gorman <mgorman@suse.de>,
        Rik van Riel <riel@redhat.com>, Dave Jones <davej@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        KOSAKI Motohiro <kosaki.motohiro@gmail.com>, bhutchings@solarflare.com,
        Konstantin Khlebnikov <khlebnikov@openvz.org>,
        Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
        Hugh Dickins <hughd@google.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Date: Fri, 26 Oct 2012 10:48:43 +0200
In-Reply-To: <CA+55aFzoxMYLXdBvdMYTy_LhrVuU233qh1eDyAda5otUTHojPA@mail.gmail.com>
References: <20121008150949.GA15130@redhat.com>
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	 <alpine.DEB.2.00.1210161714110.17278@chino.kir.corp.google.com>
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On Thu, 2012-10-25 at 16:09 -0700, Linus Torvalds wrote:
> On Thu, Oct 25, 2012 at 7:39 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > So I think the below should work, we hold the spinlock over both rb-tree
> > modification as sp free, this makes mpol_shared_policy_lookup() which
> > returns the policy with an incremented refcount work with just the
> > spinlock.
> >
> > Comments?
> 
> Looks reasonable, if annoyingly complex for something that shouldn't
> be important enough for this. Oh well.

I agree with that.. Its just that when doing numa placement one needs to
respect the pre-existing placement constraints. I've not seen a way
around this.

> However, please check me on this: the need for this is only for
> linux-next right now, correct? All the current users in my tree are ok
> with just the mutex, no?

Yes, the need comes from the numa stuff and I'll stick this patch in
there.

I completely missed Mel's patch turning it into a mutex, but I guess
that's what -next is for :-).
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