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Date: Tue, 22 May 2007 07:04:10 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@osdl.org>, LKML <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@osdl.org>, David Miller <davem@davemloft.net>,
       Stable Team <stable@kernel.org>, Anant Nitya <kernel@prachanda.info>
Subject: Re: [PATCH] Prevent going idle with softirq pending
Message-ID: <20070522050410.GA9295@elte.hu>
References: <1179783264.12708.70.camel@chaos>
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* Thomas Gleixner <tglx@linutronix.de> wrote:

> The NOHZ patch contains a check for softirqs pending when a CPU goes 
> idle. The BUG is unrelated to NOHZ, it just was made visible by the 
> NOHZ patch. The BUG showed up mainly on P4 / hyperthreading enabled 
> machines which lead the investigations into the wrong direction in the 
> first place. The real cause is in cond_resched_softirq():
> 
> cond_resched_softirq() is enabling softirqs without invoking the 
> softirq daemon when softirqs are pending. This leads to the warning 
> message in the NOHZ idle code:

good find!

>  		raw_local_irq_disable();
> -		_local_bh_enable();
> +		local_bh_enable();
>  		raw_local_irq_enable();

hm, i think this should be done without having irqs disabled?

	Ingo