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

Paul E. McKenney
2011-06-08T19:58:21Z

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