linux-kernel - Re: nmi_watchdog fix for x86

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Message-Id: <47060B680200006C00019B7B@sinclair.provo.novell.com>
Date:	Fri, 05 Oct 2007 10:01:12 -0600
From:	"David Bahi" <dbahi@...ell.com>
To:	<ak@...e.de>
Cc:	<mingo@...e.hu>, <arjan@...radead.org>, <tglx@...utronix.de>,
	<akpm@...ux-foundation.org>,
	"Gregory Haskins" <GHaskins@...ell.com>,
	<linux-kernel@...r.kernel.org>, <linux-rt-users@...r.kernel.org>
Subject: Re: nmi_watchdog fix for x86_64 to be more like i386

On Mon, 2007-10-01 at 23:41 +0200, Andi Kleen wrote:
> > IRQ_NOBALANCING is not preventing cpu unplug. It moves the affinity to the
> > next CPU, but the check in NMI watchdog for CPU == 0 would not longer
> > work.
> 
> That cannot happen right now because cpu_disable() on both i386/x86-64
> reject CPU #0. So just setting IRQ_NOBALANCING is sufficient and both
> do that already. I was wrong earlier in being concerned about this.
> 
> >  int tick_do_broadcast(cpumask_t mask)
> > @@ -137,6 +147,7 @@ int tick_do_broadcast(cpumask_t mask)
> >  		cpu_clear(cpu, mask);
> >  		td = &per_cpu(tick_cpu_device, cpu);
> >  		td->evtdev->event_handler(td->evtdev);
> > +		tick_broadcast_account(cpu);
> 
> That would not handle the case with a single CPU running only
> irq  0 but not broadcasting I think.
> 
> I believe ftp://ftp.firstfloor.org/pub/ak/x86_64/quilt/patches/fix-watchdog
> is the correct fix
> 
> -Andi

Andi, 

If it's agreed that this is the fix - can you submit a proper [PATCH] so
all users of watchdog_use_timer_and_hpet_on_x86_64.patch can be removed,
and replaced with yours.

Thank you very much



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