Subject: Re: [PATCH 1/1] powerpc: Ignore IPIs to offline CPUs

From: Michael Neuling <[email-masked]>
Date: Wed, 21 Apr 2010 12:04:38 +1000

In message <[email-masked]> you wrote:
> 
> Since there is nothing to stop an IPI from occurring to an
> offline CPU, rather than printing a warning to the logs,
> just ignore the IPI. This was seen while stress testing
> SMT enable/disable.

This seems like a recipe for disaster.  Do we at least need a
WARN_ON_ONCE?

> Signed-off-by: Brian King <[email-masked]>
> ---
> 
>  arch/powerpc/platforms/pseries/xics.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff -puN arch/powerpc/platforms/pseries/xics.c~powerpc_xics_ipi_offline arch
/powerpc/platforms/pseries/xics.c
> --- linux-2.6/arch/powerpc/platforms/pseries/xics.c~powerpc_xics_ipi_offline
	2010-04-20 20:46:06.000000000 -0500
> +++ linux-2.6-bjking1/arch/powerpc/platforms/pseries/xics.c	2010-04-20 20:4
7:53.000000000 -0500
> @@ -545,7 +545,8 @@ static irqreturn_t xics_ipi_dispatch(int
>  {
>  	unsigned long *tgt = &per_cpu(xics_ipi_message, cpu);
>  
> -	WARN_ON(cpu_is_offline(cpu));
> +	if (cpu_is_offline(cpu))
> +		return IRQ_HANDLED;
>  
>  	mb();	/* order mmio clearing qirr */
>  	while (*tgt) {
> _

FYI random white space change here.

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Mikey