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Subject: Re: [PATCH 2/4] sched: Isolate preempt counting in its own config
 option
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Ingo Molnar <mingo@elte.hu>
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Date: Wed, 08 Jun 2011 21:47:14 +0200
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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.