Re: [PATCH 1/2] topology: Check for missing CPU devices

[Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>]

Ok, both of the patches look sane to me, but it would really be nice
to hear from somebody with the actual affected architectures, and get
a tested-by.

Testing it on hacked-up x86 sounds fine, but doesn't quite have the
same kind of "yes, this fixes the actual problem" feel to it.

Also, can you clarify: does the second patch make the first patch just
an "irrelevant safety net", or are there possible callers of
topology_add_dev() that could cause problems? I'm just wondering
whether maybe the safety net ends up then possibly hiding some future
bug where we (once more) don't register a cpu and then never really
notice?

Or am I just being difficult?

                     Linus

On Sun, Jan 8, 2012 at 12:48 PM, Ben Hutchings <ben@xxxxxxxxxxxxxxx> wrote:
> Commit ccbc60d3e19a1b6ae66ca0d89b3da02dde62088b ('topology: Provide
> CPU topology in sysfs in !SMP configurations') causes a crash at boot
> on a several architectures.  The topology sysfs code assumes that
> there is a CPU device for each online CPU whereas some architectures
> that do not support SMP or cpufreq do not register any CPU devices.
> Check for this before trying to use a device.
>
> Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
> ---
>  drivers/base/topology.c |    5 ++++-
>  1 files changed, 4 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/base/topology.c b/drivers/base/topology.c
> index ae989c5..4467c85 100644
> --- a/drivers/base/topology.c
> +++ b/drivers/base/topology.c
> @@ -147,6 +147,8 @@ static int __cpuinit topology_add_dev(unsigned int cpu)
>  {
>        struct device *dev = get_cpu_device(cpu);
>
> +       if (!dev)
> +               return -ENODEV;
>        return sysfs_create_group(&dev->kobj, &topology_attr_group);
>  }
>
> @@ -154,7 +156,8 @@ static void __cpuinit topology_remove_dev(unsigned int cpu)
>  {
>        struct device *dev = get_cpu_device(cpu);
>
> -       sysfs_remove_group(&dev->kobj, &topology_attr_group);
> +       if (dev)
> +               sysfs_remove_group(&dev->kobj, &topology_attr_group);
>  }
>
>  static int __cpuinit topology_cpu_callback(struct notifier_block *nfb,
> --
> 1.7.8.2
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