linux-kernel - Re: [05/23] powerpc/pseries: Only call start-cpu when a CPU is stopped

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Message-ID: <23995.1278028968@neuling.org>
Date:	Fri, 02 Jul 2010 10:02:48 +1000
From:	Michael Neuling <mikey@...ling.org>
To:	Greg KH <gregkh@...e.de>
cc:	linux-kernel@...r.kernel.org, stable@...nel.org,
	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [05/23] powerpc/pseries: Only call start-cpu when a CPU is stopped

This is not going to work without:
f8b67691828321f5c85bb853283aa101ae673130

It'll get a build failure.

Mikey

In message <20100701172856.882121276@...rk.site> you wrote:
> 2.6.27-stable review patch.  If anyone has any objections, please let us know
.
> 
> ------------------
> 
> From: Michael Neuling <mikey@...ling.org>
> 
> commit aef40e87d866355ffd279ab21021de733242d0d5 upstream.
> 
> Currently we always call start-cpu irrespective of if the CPU is
> stopped or not. Unfortunatley on POWER7, firmware seems to not like
> start-cpu being called when a cpu already been started.  This was not
> the case on POWER6 and earlier.
> 
> This patch checks to see if the CPU is stopped or not via an
> query-cpu-stopped-state call, and only calls start-cpu on CPUs which
> are stopped.
> 
> This fixes a bug with kexec on POWER7 on PHYP where only the primary
> thread would make it to the second kernel.
> 
> Reported-by: Ankita Garg <ankita@...ux.vnet.ibm.com>
> Signed-off-by: Michael Neuling <mikey@...ling.org>
> Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
> 
> ---
>  arch/powerpc/platforms/pseries/smp.c |    6 ++++++
>  1 file changed, 6 insertions(+)
> 
> --- a/arch/powerpc/platforms/pseries/smp.c
> +++ b/arch/powerpc/platforms/pseries/smp.c
> @@ -84,6 +84,12 @@ static inline int __devinit smp_startup_
>  
>  	pcpu = get_hard_smp_processor_id(lcpu);
>  
> +	/* Check to see if the CPU out of FW already for kexec */
> +	if (smp_query_cpu_stopped(pcpu) == QCSS_NOT_STOPPED){
> +		cpu_set(lcpu, of_spin_map);
> +		return 1;
> +	}
> +
>  	/* Fixup atomic count: it exited inside IRQ handler. */
>  	task_thread_info(paca[lcpu].__current)->preempt_count	= 0;
>  
> 
> 
--
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