linux-kernel - Re: [crash] BUG: unable to handle kernel NULL pointer dereference at (null), last sysfs file: /sys/devices/pci0000:00/0000:00:01.0/local

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Date:	Thu, 24 Sep 2009 17:48:44 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	"Greg Kroah-Hartman" <gregkh@...e.de>,
	Yinghai Lu <yinghai@...nel.org>, Tejun Heo <tj@...nel.org>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [crash] BUG: unable to handle kernel NULL pointer dereference at (null), last sysfs file: /sys/devices/pci0000:00/0000:00:01.0/local_cpus

On Sat, 19 Sep 2009 01:08:02 am Linus Torvalds wrote:
> [ Side note: looking closer, I think our headers are buggy, and I _know_ 
>   they are confusing. The above inline declaration of cpumask_of_node() 
>   seems to be then later overridden in <asm-generic/topology.h> by a 
>   #define! 
> 
>   And if I read that right, that will also override the debugging 
>   versions that we declared if CONFIG_DEBUG_PER_CPU_MAPS is on. Ingo? 
>   Rusty? Am I missing something?

What a tangle.

The CONFIG_DEBUG_PER_CPU_MAPS only overrides cpumask_of_node in the NUMA case
(otherwise, it leaves it alone).

And asm-generic/topology.h only defines cpumask_of_node in the !NUMA case.

But there's still redundancy.  Ingo...

Subject: x86: remove redundant non-NUMA topology functions

arch/x86/include/asm/topology.h declares inline fns cpu_to_node
and cpumask_of_node for !NUMA, even though they are then declared as macros
by asm-generic/topology.h, which is #included just below.

The macros (which are the same) end up being used; these functions are
just confusing.

Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
---
 arch/x86/include/asm/topology.h |   10 ----------
 1 file changed, 10 deletions(-)

diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
--- a/arch/x86/include/asm/topology.h
+++ b/arch/x86/include/asm/topology.h
@@ -165,21 +165,11 @@ static inline int numa_node_id(void)
 	return 0;
 }
 
-static inline int cpu_to_node(int cpu)
-{
-	return 0;
-}
-
 static inline int early_cpu_to_node(int cpu)
 {
 	return 0;
 }
 
-static inline const struct cpumask *cpumask_of_node(int node)
-{
-	return cpu_online_mask;
-}
-
 static inline void setup_node_to_cpumask_map(void) { }
 
 #endif
--
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