linux-kernel - Re: [PATCH 2/4] sched: Isolate preempt counting in its own config option

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Message-ID: <20110608195816.GJ2324@linux.vnet.ibm.com>
Date:	Wed, 8 Jun 2011 12:58:16 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH 2/4] sched: Isolate preempt counting in its own config
 option

On Wed, Jun 08, 2011 at 09:47:14PM +0200, Peter Zijlstra wrote:
> On Wed, 2011-06-08 at 19:48 +0200, Frederic Weisbecker wrote:
> > 
> > Create a new CONFIG_PREEMPT_COUNT that handles the inc/dec
> > of preempt count offset independently. So that the offset
> > can be updated by preempt_disable() and preempt_enable()
> > even without the need for CONFIG_PREEMPT beeing set.
> > 
> > This prepares to make CONFIG_DEBUG_SPINLOCK_SLEEP working
> > with !CONFIG_PREEMPT where it currently doesn't detect
> > code that sleeps inside explicit preemption disabled
> > sections. 
> 
> The last time this got proposed it got shot down due to the extra
> inc/dec stuff all over the place increasing overhead significantly.

Even given that the extra inc/dec stuff only happens in kernels built
with DEBUG_SPINLOCK_SLEEP=y (DEBUG_ATOMIC_SLEEP=y after patch 4/4)?

							Thanx, Paul
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