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

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Date:	Mon, 09 Jan 2012 02:56:56 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
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

On Mon, 2012-01-09 at 02:47 +0000, Ben Hutchings wrote:
> On Sun, 2012-01-08 at 16:18 -0800, Linus Torvalds wrote:
> > 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.
> 
> Indeed.
> 
> > 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?
> [...]
> 
> driver_init() doesn't check that cpu_dev_init() - or any of the other
> functions it calls - is successful.  So in theory at least we could boot
> and still have no CPU devices after the first patch.

I mean to say that we could have no CPU devices after the *second*
patch.  So the first patch is an extra defence against that.  (Though we
could just as well panic if register_cpu() fails at boot time.)

Ben.

-- 
Ben Hutchings
Life is what happens to you while you're busy making other plans.
                                                               - John Lennon

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