Fix perfctr oops on ppc32

This seems to be the reason why the Fedora rawhide 2.6.31-rc kernel
doesn't boot. With some CPUs, cur_cpu_spec->oprofile_cpu_type can be
NULL -- which makes strcmp() unhappy.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
---
At first glance, it looks like there are a bunch of other places which
use cur_cpu_spec->oprofile_cpu_type without first checking if it's
non-NULL, but maybe those are all 64-bit and all 64-bit cpu types have
it set?

On Sat, 2009-08-01 at 14:29 +0100, David Woodhouse wrote:
> This seems to be the reason why the Fedora rawhide 2.6.31-rc kernel
> doesn't boot. With some CPUs, cur_cpu_spec->oprofile_cpu_type can be
> NULL -- which makes strcmp() unhappy.
> 
> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

Thanks David !

Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---

Paulus, do you want to put that in your new perfctr-powerpc tree or I'll
just stick that in my merge brange next week along with other fixes ?

Cheers,
Ben.

> ---
> At first glance, it looks like there are a bunch of other places which
> use cur_cpu_spec->oprofile_cpu_type without first checking if it's
> non-NULL, but maybe those are all 64-bit and all 64-bit cpu types have
> it set?
> 
> diff --git a/arch/powerpc/kernel/mpc7450-pmu.c b/arch/powerpc/kernel/mpc7450-pmu.c
> index 75ff47f..ea383c1 100644
> --- a/arch/powerpc/kernel/mpc7450-pmu.c
> +++ b/arch/powerpc/kernel/mpc7450-pmu.c
> @@ -408,7 +408,8 @@ struct power_pmu mpc7450_pmu = {
>  
>  static int init_mpc7450_pmu(void)
>  {
> -	if (strcmp(cur_cpu_spec->oprofile_cpu_type, "ppc/7450"))
> +	if (cur_cpu_spec->oprofile_cpu_type &&
> +	    strcmp(cur_cpu_spec->oprofile_cpu_type, "ppc/7450"))
>  		return -ENODEV;
>  
>  	return register_power_pmu(&mpc7450_pmu);
> 
>

On Sat, 2009-08-01 at 14:29 +0100, David Woodhouse wrote:
> This seems to be the reason why the Fedora rawhide 2.6.31-rc kernel
> doesn't boot. With some CPUs, cur_cpu_spec->oprofile_cpu_type can be
> NULL -- which makes strcmp() unhappy.
> 
> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
> ---
> At first glance, it looks like there are a bunch of other places which
> use cur_cpu_spec->oprofile_cpu_type without first checking if it's
> non-NULL, but maybe those are all 64-bit and all 64-bit cpu types have
> it set?

Argh, ignore my Acked-by, I think the patch isn't right...

> diff --git a/arch/powerpc/kernel/mpc7450-pmu.c b/arch/powerpc/kernel/mpc7450-pmu.c
> index 75ff47f..ea383c1 100644
> --- a/arch/powerpc/kernel/mpc7450-pmu.c
> +++ b/arch/powerpc/kernel/mpc7450-pmu.c
> @@ -408,7 +408,8 @@ struct power_pmu mpc7450_pmu = {
>  
>  static int init_mpc7450_pmu(void)
>  {
> -	if (strcmp(cur_cpu_spec->oprofile_cpu_type, "ppc/7450"))
> +	if (cur_cpu_spec->oprofile_cpu_type &&
> +	    strcmp(cur_cpu_spec->oprofile_cpu_type, "ppc/7450"))
>  		return -ENODEV;

That means that if we have oprofile_cpu_type, we will enable the 7450
PMCs which doesn't sound right. Shouldn't it be instead:

	if (!cur_cpu_spec->oprofile_cpu_type ||
	    strcmp(cur_cpu_spec->oprofile_cpu_type, "ppc/7450"))
 		return -ENODEV;

Cheers,
Ben.


>  	return register_power_pmu(&mpc7450_pmu);
> 
>

On Thu, 2009-08-06 at 07:02 +1000, Benjamin Herrenschmidt wrote:
> 
> Argh, ignore my Acked-by, I think the patch isn't right...

Hm, good point. Doh.