linux-kernel - Re: [PATCH] x86: call machine_shutdown and stop all CPUs in native_machine

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Message-ID: <20081110224934.GA2069@ucw.cz>
Date:	Mon, 10 Nov 2008 23:49:34 +0100
From:	Pavel Machek <pavel@...e.cz>
To:	Ivan Vecera <ivecera@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	nhorman@...hat.com, jmarchan@...hat.com
Subject: Re: [PATCH] x86: call machine_shutdown and stop all CPUs in
	native_machine_halt

On Thu 2008-11-06 17:10:01, Ivan Vecera wrote:
> Any comments?
> 
> Ivan
> 
> ---
> Ivan Vecera wrote:
> > Ingo Molnar wrote:
> >> the code in arch/x86/kernel/smp.c::stop_this_cpu() is very similar to 
> >> this and could be shared. You could move the stop_this_cpu() function to 
> >> arch/x86/kernel/process.c (out of smp.c), so that it can be used by 
> >> reboot.c.
> >>
> > Yes, this make sense. Here is the patch.
> > 
> > Ivan
> > 
> > ---
> >  arch/x86/kernel/process.c |   16 ++++++++++++++++
> >  arch/x86/kernel/reboot.c  |    5 +++++
> >  arch/x86/kernel/smp.c     |   13 -------------
> >  include/asm-x86/system.h  |    2 ++
> >  4 files changed, 23 insertions(+), 13 deletions(-)
> > 
> > diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
> > index c622772..af6904e 100644
> > --- a/arch/x86/kernel/process.c
> > +++ b/arch/x86/kernel/process.c
> > @@ -8,6 +8,7 @@
> >  #include <linux/pm.h>
> >  #include <linux/clockchips.h>
> >  #include <asm/system.h>
> > +#include <asm/apic.h>
> >  
> >  unsigned long idle_halt;
> >  EXPORT_SYMBOL(idle_halt);
> > @@ -122,6 +123,21 @@ void default_idle(void)
> >  EXPORT_SYMBOL(default_idle);
> >  #endif
> >  
> > +void stop_this_cpu(void *dummy)
> > +{
> > +	local_irq_disable();
> > +	/*
> > +	 * Remove this CPU:
> > +	 */
> > +	cpu_clear(smp_processor_id(), cpu_online_map);
> > +#ifdef CONFIG_X86_LOCAL_APIC
> > +	disable_local_APIC();
> > +#endif
> > +	if (hlt_works(smp_processor_id()))
> > +		for (;;) halt();
> > +	for (;;);
> > +}

Why the new ifdef? And while we are at it, why is it neccessary to
disable APIC for stopping CPU? (comment in code would be nice)

> > -static void stop_this_cpu(void *dummy)
> > -{
> > -	local_irq_disable();
> > -	/*
> > -	 * Remove this CPU:
> > -	 */
> > -	cpu_clear(smp_processor_id(), cpu_online_map);
> > -	disable_local_APIC();
> > -	if (hlt_works(smp_processor_id()))
> > -		for (;;) halt();
> > -	for (;;);
> > -}
> > -
> >  /*
> >   * this function calls the 'stop' function on all other CPUs in the system.
> >   */

-- 
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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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