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

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Date:	Sun, 17 Oct 2010 17:05:45 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	Venkatesh Pallipadi <venki@...gle.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, 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 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().

> +	}
> +
> +	__irq_enter();
>  }
>  
>  #ifdef __ARCH_IRQ_EXIT_IRQS_DISABLED
> -- 
> 1.7.1
> 
> --
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