[PATCH 1/1] x86: Change _node_to_cpumask_ptr to return const ptr

[Mike Travis <travis@sgi.com>]

Ingo Molnar wrote:
> * Vegard Nossum <vegard.nossum@gmail.com> wrote:
> 
>> On Thu, Jul 3, 2008 at 10:44 AM, Ingo Molnar <mingo@elte.hu> wrote:
>>> * Mike Travis <travis@sgi.com> wrote:
>>>
>>>> Subject: [PATCH 1/1] x86: Add check for node passed to node_to_cpumask V3
>>>>
>>>>   * When CONFIG_DEBUG_PER_CPU_MAPS is set, the node passed to
>>>>     node_to_cpumask and node_to_cpumask_ptr should be validated.
>>>>     If invalid, then a dump_stack is performed and a zero cpumask
>>>>     is returned.
>>>>
>>>> Based on "Fri Jun 27 10:06:06 PDT 2008" tip/master...  ;-)
>>>>
>>>> Signed-off-by: Mike Travis <travis@sgi.com>
>>>> ---
>>>> V2: Slightly different version to remove a compiler warning.
>>>> V3: Redone to reflect moving setup.c -> setup_percpu.c
>>> applied to tip/x86/unify-setup - thanks Mike.
>>>
>>> Vegard, can i add your Acked-by too?
>> To be honest, I'd prefer that the function returns a const pointer. 
>> Mike and I have both reviewed all callers independently and concluded 
>> that there is no problem in doing this, and that, in fact, this is the 
>> correct way to deal with it.
>>
>> So if Mike submits a V4 with this const return type, or another patch 
>> on top of this one, I'll ack it :-)
> 
> ok, i'll wait for v4 :)
> 
> (v3 is applied already so Mike please send a delta to v3.)
> 
> 	Ingo

Subject: [PATCH 1/1] x86: Change _node_to_cpumask_ptr to return const ptr

  * Strengthen the return type for the _node_to_cpumask_ptr to be
    a const pointer.  This adds compiler checking to insure that
    node_to_cpumask_map[] is not changed inadvertently.

Applies to tip/master with the following patch applied:

	"[PATCH 1/1] x86: Add check for node passed to node_to_cpumask V3"

Signed-off-by: Mike Travis <travis@sgi.com>
---
Note: I did not change node_to_cpumask_ptr() in include/asm-generic/topology.h
      as node_to_cpumask_ptr_next() does change the cpumask value.
---
 arch/x86/kernel/setup_percpu.c |    8 ++++----
 include/asm-x86/topology.h     |   10 +++++-----
 2 files changed, 9 insertions(+), 9 deletions(-)

--- linux-2.6.tip.orig/arch/x86/kernel/setup_percpu.c
+++ linux-2.6.tip/arch/x86/kernel/setup_percpu.c
@@ -353,23 +353,23 @@ static const cpumask_t cpu_mask_none;
 /*
  * Returns a pointer to the bitmask of CPUs on Node 'node'.
  */
-cpumask_t *_node_to_cpumask_ptr(int node)
+const cpumask_t *_node_to_cpumask_ptr(int node)
 {
 	if (node_to_cpumask_map == NULL) {
 		printk(KERN_WARNING
 			"_node_to_cpumask_ptr(%d): no node_to_cpumask_map!\n",
 			node);
 		dump_stack();
-		return &cpu_online_map;
+		return (const cpumask_t *)&cpu_online_map;
 	}
 	if (node >= nr_node_ids) {
 		printk(KERN_WARNING
 			"_node_to_cpumask_ptr(%d): node > nr_node_ids(%d)\n",
 			node, nr_node_ids);
 		dump_stack();
-		return (cpumask_t *)&cpu_mask_none;
+		return &cpu_mask_none;
 	}
-	return (cpumask_t *)&node_to_cpumask_map[node];
+	return &node_to_cpumask_map[node];
 }
 EXPORT_SYMBOL(_node_to_cpumask_ptr);
 
--- linux-2.6.tip.orig/include/asm-x86/topology.h
+++ linux-2.6.tip/include/asm-x86/topology.h
@@ -82,7 +82,7 @@ DECLARE_EARLY_PER_CPU(int, x86_cpu_to_no
 #ifdef CONFIG_DEBUG_PER_CPU_MAPS
 extern int cpu_to_node(int cpu);
 extern int early_cpu_to_node(int cpu);
-extern cpumask_t *_node_to_cpumask_ptr(int node);
+extern const cpumask_t *_node_to_cpumask_ptr(int node);
 extern cpumask_t node_to_cpumask(int node);
 
 #else	/* !CONFIG_DEBUG_PER_CPU_MAPS */
@@ -103,7 +103,7 @@ static inline int early_cpu_to_node(int 
 }
 
 /* Returns a pointer to the cpumask of CPUs on Node 'node'. */
-static inline cpumask_t *_node_to_cpumask_ptr(int node)
+static inline const cpumask_t *_node_to_cpumask_ptr(int node)
 {
 	return &node_to_cpumask_map[node];
 }
@@ -118,7 +118,7 @@ static inline cpumask_t node_to_cpumask(
 
 /* Replace default node_to_cpumask_ptr with optimized version */
 #define node_to_cpumask_ptr(v, node)		\
-		cpumask_t *v = _node_to_cpumask_ptr(node)
+		const cpumask_t *v = _node_to_cpumask_ptr(node)
 
 #define node_to_cpumask_ptr_next(v, node)	\
 			   v = _node_to_cpumask_ptr(node)
@@ -186,7 +186,7 @@ extern int __node_distance(int, int);
 #define	cpu_to_node(cpu)	0
 #define	early_cpu_to_node(cpu)	0
 
-static inline cpumask_t *_node_to_cpumask_ptr(int node)
+static inline const cpumask_t *_node_to_cpumask_ptr(int node)
 {
 	return &cpu_online_map;
 }
@@ -201,7 +201,7 @@ static inline int node_to_first_cpu(int 
 
 /* Replace default node_to_cpumask_ptr with optimized version */
 #define node_to_cpumask_ptr(v, node)		\
-		cpumask_t *v = _node_to_cpumask_ptr(node)
+		const cpumask_t *v = _node_to_cpumask_ptr(node)
 
 #define node_to_cpumask_ptr_next(v, node)	\
 			   v = _node_to_cpumask_ptr(node)