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SubjectRe: Fw: 2.6.16 crashes when running numastat on p575
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

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 <>

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;
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