linux-kernel - Re: [PATCH 8/8] Call tick_check_idle before __irq

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Date:	Mon, 18 Oct 2010 11:15:27 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Yong Zhang <yong.zhang0@...il.com>
Cc:	Venkatesh Pallipadi <venki@...gle.com>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	linux-kernel@...r.kernel.org, Paul Turner <pjt@...gle.com>,
	Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH 8/8] Call tick_check_idle before __irq_enter

On Sun, 2010-10-17 at 17:05 +0800, Yong Zhang wrote:
> On Mon, Oct 04, 2010 at 05:03:23PM -0700, Venkatesh Pallipadi wrote:
> > diff --git a/kernel/softirq.c b/kernel/softirq.c
> > index 267f7b7..6bb7e19 100644
> > --- a/kernel/softirq.c
> > +++ b/kernel/softirq.c
> > @@ -296,10 +296,16 @@ void irq_enter(void)
> >  
> >  	rcu_irq_enter();
> >  	if (idle_cpu(cpu) && !in_interrupt()) {
> > -		__irq_enter();
> > +		/*
> > +		 * Prevent raise_softirq from needlessly waking up ksoftirqd
> > +		 * here, as softirq will be serviced on return from interrupt.
> > +		 */
> > +		local_bh_disable();
> >  		tick_check_idle(cpu);
> > -	} else
> > -		__irq_enter();
> > +		local_bh_enable();
> 
> 		_local_bh_enable()
> 
> local_bh_enable() could invoke do_softirq().

This seems to indeed cure that explosion.. Thanks!


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