On Tue, 27 Nov 2007 23:16:28 +0100
Andi Kleen <[EMAIL PROTECTED]> wrote:
> On Tue, Nov 27, 2007 at 01:50:53PM -0800, [EMAIL PROTECTED] wrote:
> > Change loops controlled by 'for (i = 0; i < NR_CPUS; i++)' to use
> > 'for_each_possible_cpu(i)' when there's a _remote possibility_ of
> > dereferencing a non-allocated per_cpu variable involved.
> >
> > All files except mm/vmstat.c are x86 arch.
> >
> > Based on 2.6.24-rc3-mm1 .
> >
> > Thanks to [EMAIL PROTECTED] for pointing this out.
>
> Looks good to me. 2.6.24 candidate.
hm. Has anyone any evidence that we're actually touching
not-possible-cpu's memory here?
Also, the sum_vm_events() change looks buggy - it assumes that
cpu_possible_map has no gaps in it. But that change is unneeded because
sum_vm_events() is only ever passed cpu_online_map and I'm hoping that we
don't usually online not-possible CPUs.
--- a/mm/vmstat.c~mm-prevent-dereferencing-non-allocated-per_cpu-variables-fix
+++ a/mm/vmstat.c
@@ -27,12 +27,12 @@ static void sum_vm_events(unsigned long
memset(ret, 0, NR_VM_EVENT_ITEMS * sizeof(unsigned long));
cpu = first_cpu(*cpumask);
- while (cpu < NR_CPUS && cpu_possible(cpu)) {
+ while (cpu < NR_CPUS) {
struct vm_event_state *this = &per_cpu(vm_event_states, cpu);
cpu = next_cpu(cpu, *cpumask);
- if (cpu < NR_CPUS && cpu_possible(cpu))
+ if (cpu < NR_CPUS)
prefetch(&per_cpu(vm_event_states, cpu));
_
-
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