Subject: Re: [PATCH] powerpc/pseries: Disable VPNH feature

From: Benjamin Herrenschmidt <[email-masked]>
Date: Thu, 10 Mar 2011 10:07:25 +1100

On Thu, 2011-03-10 at 10:00 +1100, Benjamin Herrenschmidt wrote:
> This feature triggers nasty races in the scheduler between the
> rebuilding of the topology and the load balancing code, causing
> the machine to hang.
> 
> Disable it for now until the races are fixed.
> 
> Signed-off-by: Benjamin Herrenschmidt <[email-masked]>
> ---
> 
> Jesse: I'm sending that to Linus now. We'll sort things out for the
> next release.
> 
> diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
> index fd48123..74f1baa 100644
> --- a/arch/powerpc/mm/numa.c
> +++ b/arch/powerpc/mm/numa.c
> @@ -1516,6 +1516,7 @@ int start_topology_update(void)
>  {
>  	int rc = 0;
>  
> +#if 0 /* Disabled until races with load balancing are fixed */
>  	if (firmware_has_feature(FW_FEATURE_VPHN) &&
>  	    get_lppaca()->shared_proc) {
>  		vphn_enabled = 1;
> @@ -1524,6 +1525,7 @@ int start_topology_update(void)
>  		set_topology_timer();
>  		rc = 1;
>  	}
> +#endif

Turning that into if (0 && instead to avoid compiler warnings
and thus build failures

Cheers,
Ben.