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Date: Sun, 2 Apr 2006 22:12:29 -0700 (PDT)
From: Christoph Lameter <clameter@SGI.com>
To: Sonny Rao <sonny@burdell.org>
Subject: Re: Fw: 2.6.16 crashes when running numastat on p575
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On Sun, 2 Apr 2006, Andrew Morton wrote:

> I have a vague feeling that you guys worked on numastat?

This is mostly Andi's code although I added the zone_pcp() stuff. This is 
failing because zone_pcp() only returns valid information for online 
processors.

Initially all zone_pcps() point to the boot_cpuset (see zone_pcp_init)
and therefore zone_pcp) is always valid and we do not see this bug. But 
if someone downs a processor or a processor dies then free_zone_pageset() 
is called which will set zone_pcp() = NULL.


Fix NULL pointer dereference in node_read_numastat()

zone_pcp() only returns valid values if the processor is online.

Change node_read_numastat() to only scan online processors.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.16/drivers/base/node.c
===================================================================
--- linux-2.6.16.orig/drivers/base/node.c	2006-03-19 21:53:29.000000000 -0800
+++ linux-2.6.16/drivers/base/node.c	2006-04-02 21:59:49.000000000 -0700
@@ -106,7 +106,7 @@ static ssize_t node_read_numastat(struct
 	other_node = 0;
 	for (i = 0; i < MAX_NR_ZONES; i++) {
 		struct zone *z = &pg->node_zones[i];
-		for (cpu = 0; cpu < NR_CPUS; cpu++) {
+		for_each_online_cpu(cpu) {
 			struct per_cpu_pageset *ps = zone_pcp(z,cpu);
 			numa_hit += ps->numa_hit;
 			numa_miss += ps->numa_miss;