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SubjectRe: [PATCH 1/1] mm: Prevent dereferencing non-allocated per_cpu variables
On Tue, 27 Nov 2007, Andrew Morton wrote:

> I don't recall anyone ever demonstrating that prefetch is useful in-kernel.

vmstat: remove prefetch

Remove the prefetch logic in order to avoid touching impossible per cpu
areas.

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

---
mm/vmstat.c | 11 ++---------
1 file changed, 2 insertions(+), 9 deletions(-)

Index: linux-2.6/mm/vmstat.c
===================================================================
--- linux-2.6.orig/mm/vmstat.c 2007-11-27 16:04:15.345713812 -0800
+++ linux-2.6/mm/vmstat.c 2007-11-27 16:07:00.552713192 -0800
@@ -21,21 +21,14 @@ EXPORT_PER_CPU_SYMBOL(vm_event_states);

static void sum_vm_events(unsigned long *ret, cpumask_t *cpumask)
{
- int cpu = 0;
+ int cpu;
int i;

memset(ret, 0, NR_VM_EVENT_ITEMS * sizeof(unsigned long));

- cpu = first_cpu(*cpumask);
- while (cpu < NR_CPUS) {
+ for_each_cpu_mask(cpu, *cpumask) {
struct vm_event_state *this = &per_cpu(vm_event_states, cpu);

- cpu = next_cpu(cpu, *cpumask);
-
- if (cpu < NR_CPUS)
- prefetch(&per_cpu(vm_event_states, cpu));
-
-
for (i = 0; i < NR_VM_EVENT_ITEMS; i++)
ret[i] += this->event[i];
}
-
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