linux-kernel - Re: [PATCH] increase PREEMPT_BITS to 12 to avoid overflow when starting KVM

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Date:	Tue, 30 Mar 2010 20:34:49 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Rik van Riel <riel@...hat.com>
Cc:	linux-kernel@...r.kernel.org, avi@...hat.com, aarcange@...hat.com,
	akpm@...ux-foundation.org,
	Kent Overstreet <kent.overstreet@...il.com>,
	Ingo Molnar <mingo@...e.hu>, tglx <tglx@...utronix.de>
Subject: Re: [PATCH] increase PREEMPT_BITS to 12 to avoid overflow when
 starting KVM

On Tue, 2010-03-30 at 14:05 -0400, Rik van Riel wrote:
> > Also, you'll need to convince mingo and tglx too.. taking that many
> > spinlocks is utter suckage..
> 
> No argument there.  I can't think of an alternative to mm_take_all_locks
> though.  Andrea? 

Well there's altneratives enough, back when this got introduces quite a
few got mentioned too, but they all make the !mm_take_all_locks() lock
side slower so Andrea didn't like them.

I think one of them got mentioned in yesterday's thread as well.

Another alternative is making all those spinlocks mutexes, that will get
rid of that massive !preempt section too.

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