Re: [RFC PATCH 5/6] implement per-cpu&per-domain state machinecall_srcu()

[Peter Zijlstra]

On Tue, 2012-03-06 at 22:44 +0800, Lai Jiangshan wrote:
> >> +                       if ((++idle_loop & 0xF) == 0) {
> >> +                               spin_unlock_irq(&sp->gp_lock);
> >> +                               udelay(1);
> >> +                               spin_lock_irq(&sp->gp_lock);
> >> +                       }
> >
> > The purpose of this bit isn't quite clear to me, is this simply a lock
> > break?
> 
> Yes, the main purpose is:
> make the time of sp->gp_lock short, can be determined. 

either introduce cond_resched_lock_irq() or write something like:

	if (need_resched() || spin_needbreak(&sp->gp_lock)) {
		spin_unlock_irq(&sp->gp_lock);
		cond_resched();
		spin_lock_irq(&sp->gp_lock);
	}

udelay(1) is complete nonsense.. 
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