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Message-ID: <41BC1BF9.70701@colorfullife.com>
Date: Sun, 12 Dec 2004 11:22:49 +0100
From: Manfred Spraul <manfred@colorfullife.com>
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To: Andrea Arcangeli <andrea@suse.de>
CC: Zwane Mwaikambo <zwane@arm.linux.org.uk>,
       George Anzinger <george@mvista.com>, Lee Revell <rlrevell@joe-job.com>,
       dipankar@in.ibm.com, ganzinger@mvista.com,
       lkml <linux-kernel@vger.kernel.org>
Subject: Re: RCU question
References: <41BA0ECF.1060203@mvista.com> <Pine.LNX.4.61.0412101558240.24986@montezuma.fsmlabs.com> <41BA59F6.5010309@mvista.com> <Pine.LNX.4.61.0412101943260.1101@montezuma.fsmlabs.com> <41BA698E.8000603@mvista.com> <Pine.LNX.4.61.0412110751020.5214@montezuma.fsmlabs.com> <41BB2108.70606@colorfullife.com> <41BB25B2.90303@mvista.com> <Pine.LNX.4.61.0412111947280.7847@montezuma.fsmlabs.com> <41BC0854.4010503@colorfullife.com> <20041212093714.GL16322@dualathlon.random>
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Andrea Arcangeli wrote:

>On Sun, Dec 12, 2004 at 09:59:00AM +0100, Manfred Spraul wrote:
>  
>
>>It means that our NMI irq return path should check if it points to a hlt 
>>instruction and if yes, then increase the saved EIP by one before doing 
>>the iretd, right?
>>    
>>
>
>I don't think we'll ever post any event through nmi, so it doesn't
>matter. We only care to be waken by real irqs, not nmi/smi. Idle loop is
>fine to ignore the actions of the nmi handlers and to hang into the
>"hlt".
>  
>
No, You misunderstood the problem:

sti
** NMI handler
** normal interrupt arrives, is queued by the cpu
** irqd from NMI handler
** cpu notices the normal interrupt, handles it.
** normal interrupt does a wakeup, schedules a tasklet, whatever
** irqd from normal interupt
hlt << cpu sleeps.

Thus: lost wakeup.

--
    Manfred
**