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From: Arnd Bergmann <arnd@arndb.de>
To: cbe-oss-dev@ozlabs.org
Subject: Re: [Cbe-oss-dev] [RFC] Cell: shutdown method for spu_sysdev_class
Date: Tue, 29 May 2007 20:23:49 +0200
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Cc: Geoff Levand <geoffrey.levand@am.sony.com>, linux-kernel@vger.kernel.org,
       gregkh@suse.de
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On Sunday 06 May 2007, Geoff Levand wrote:
> --- ps3-linux-dev.orig/arch/powerpc/platforms/cell/spu_base.c
> +++ ps3-linux-dev/arch/powerpc/platforms/cell/spu_base.c
> @@ -463,8 +463,21 @@ void spu_free(struct spu *spu)
>  }
>  EXPORT_SYMBOL_GPL(spu_free);
>
> +static int spu_shutdown(struct sys_device *sysdev)
> +{
> +       struct spu *spu = container_of(sysdev, struct spu, sysdev);
> +
> +       // what else here???
> +
> +       spu_free_irqs(spu);
> +       spu_destroy_spu(spu);
> +       kfree(spu);
> +       return 0;
> +}
> +
>  struct sysdev_class spu_sysdev_class = {
> -       set_kset_name("spu")
> +       set_kset_name("spu"),
> +       .shutdown = spu_shutdown,
>  };
>
>  int spu_add_sysdev_attr(struct sysdev_attribute *attr)

After some debugging, I found that this patch creates an oops when slab
debugging is enabled, the reason for that being that sysdev_shutdown()
iterates over all system devices using list_for_each_entry(), not
list_for_each_entry_safe().

There are two ways of fixing this:

- use list_for_each_entry_safe() to go over all devices so they
  can be freed in their ->shutdown method.
- not free the device, because we know the system is going down
  anyway.

Is it documented or implied somewhere that ->shutdown must not free
the device? If not, the first option is probably the safer choice.

	Arnd <><