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Re: [PATCH] fix of unnecessary clocksource change after exiting from KDB

To: Konstantin Baydarov <kbaidarov@xxxxxxxxxxxxx>
Subject: Re: [PATCH] fix of unnecessary clocksource change after exiting from KDB console
From: Konstantin Baydarov <kbaidarov@xxxxxxxxxxxxx>
Date: Thu, 9 Aug 2007 21:23:29 +0400
Cc: Keith Owens <kaos@xxxxxxx>, kdb@xxxxxxxxxxx
In-reply-to: <20070803212514.46016060@xxxxxxxxxxxxxxxxxxxxxx>
References: <20070709193916.32bcfdcd@xxxxxxxxxxxxxxxxxxxxxx> <4092.1186128305@xxxxxxxxxxxxxxxxxxxxxx> <20070803212514.46016060@xxxxxxxxxxxxxxxxxxxxxx>
Sender: kdb-bounce@xxxxxxxxxxx
On Fri, 3 Aug 2007 21:25:14 +0400
Konstantin Baydarov <kbaidarov@xxxxxxxxxxxxx> wrote:

> I'm afraid that previous patch won't work with SMP kernel with high
> resolution timer enabled, because of hres_timers_resume(): /*
>  * During resume we might have to reprogram the high resolution timer
>  * interrupt (on the local CPU):
>  */
> void hres_timers_resume(void)
> {
>       WARN_ON_ONCE(num_online_cpus() > 1);
> 
>       /* Retrigger the CPU local events: */
>       retrigger_next_event(NULL);
> }
> When we call hres_timers_resume() from timekeeping_resume() other
> CPUs should be in offline. AFAIK, KDB doesn't put CPUs to offline.
> 
> Here Is new version on fix. Patch against 2.6.23-rc1. I've tested it
> on UP pentium4.
> Soft Lockup fix was taken from KGDB mailing list.
> To prevent unnecessary clocksource change I call
> clocksource_resume_watchdog() instead of suspending whole timekeeping 
> system.

KGDB has the same problem with unnecessary clocksource change. I've suggest 
patch that fixes the problem the same way.
Patch was accepted with small changes:
http://kgdb.cvs.sourceforge.net/kgdb/kgdb-2/clocksource_watchdog.patch?view=log&pathrev=linux2_6_23_uprev

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