linux-kernel - Re: [patch for-3.7] mm, mempolicy: fix printing stack contents in numa

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Date:	Fri, 26 Oct 2012 10:48:43 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	David Rientjes <rientjes@...gle.com>,
	Sasha Levin <levinsasha928@...il.com>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Dave Jones <davej@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	bhutchings@...arflare.com,
	Konstantin Khlebnikov <khlebnikov@...nvz.org>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Hugh Dickins <hughd@...gle.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch for-3.7] mm, mempolicy: fix printing stack contents in
 numa_maps

On Thu, 2012-10-25 at 16:09 -0700, Linus Torvalds wrote:
> On Thu, Oct 25, 2012 at 7:39 AM, Peter Zijlstra <peterz@...radead.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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