linux-kernel - Re: [patch 3/4] Locally disable the softlockup watchdog rather than touching it

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Date:	Wed, 28 Mar 2007 10:13:04 -0400
From:	Prarit Bhargava <prarit@...hat.com>
To:	Andi Kleen <ak@...e.de>
CC:	virtualization@...ts.linux-foundation.org,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	virtualization@...ts.osdl.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, John Hawkes <hawkes@....com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Eric Dumazet <dada1@...mosbay.com>
Subject: Re: [patch 3/4] Locally disable the softlockup watchdog rather than
 touching it



Andi Kleen wrote:
> On Wednesday 28 March 2007 16:00, Prarit Bhargava wrote:
>   
>>>> touch_nmi_watchdog is attempting to tickle _all_ CPUs softlockup watchdogs.
>>>>     
>>>>         
>>> It is supposed to only touch the current CPU, just like it only touches
>>> the NMI watchdog on the current CPU.
>>>
>>>   
>>>       
>> Andi,
>>
>> (sorry for the cut-and-paste). 
>>
>> touch_nmi_watchdogs sets EACH CPUs alert_counter to 0.
>>     
>
> You're right. Sorry for the confusion.  
>
> But just touching the current CPU would make much more sense. After all
> the caller doesn't know anything about the state of other CPUs. Perhaps it would be best
> to just change that and keep the softlockup semantics.
>   
Yeah -- you're probably right, and besides that we're not seeing a crazy 
# of softlockup messages after touch_nmi_watchdogs calls.

My original comments regarding the code still stand though -- we 
shouldn't have multiple methods of playing with the softlockup watchdog.

P.

> -Andi
>   
-
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