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

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Date:	Wed, 28 Mar 2007 10:00:15 -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


>> 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.

void touch_nmi_watchdog (void)
{
        if (nmi_watchdog > 0) {
                unsigned cpu;

                /*
                 * Just reset the alert counters, (other CPUs might be
                 * spinning on locks we hold):
                 */
                for_each_present_cpu (cpu)
                        alert_counter[cpu] = 0;
        }

        /*
         * Tickle the softlockup detector too:
         */
        touch_softlockup_watchdog();
}

The call to touch_softlockup_watchdog here is incorrect -- it is only 
touching the current CPU's softlockup.

P.
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