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

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Message-ID: <CA+55aFwwnJPpVY++Vgr6p3s47YjdYWV3sgLZzvCtiJp6DEu78Q@mail.gmail.com>
Date:	Sun, 8 Jan 2012 16:18:41 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Ben Hutchings <ben@...adent.org.uk>
Cc:	Greg Kroah-Hartman <gregkh@...e.de>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Linux-Arch <linux-arch@...r.kernel.org>,
	Thorsten Glaser <tg@...bsd.de>,
	Debian kernel team <debian-kernel@...ts.debian.org>,
	linux-m68k@...r.kernel.org, debian-68k@...ts.debian.org
Subject: Re: [PATCH 1/2] topology: Check for missing CPU devices

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@...adent.org.uk> 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@...adent.org.uk>
> ---
>  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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