>> I just encountered the following oops and general protection fault
>> trying to suspend/resume my laptop. I've got a Dell D820 laptop with a 2
>> GHz Core 2 Duo CPU. It usually suspends/resumes fine but not always. The
>> relevant errors are below but the full dmesg log is at
>> http://people.xiph.org/~jm/suspend_resume_oops.txt and my config is in
>> http://people.xiph.org/~jm/config-2.6.20-rc5.txt
>>
>> This happens when I'm running 2.6.20-rc5. The previous kernel version I
>> was using is 2.6.19-rc6 and was much more broken (second attempt
>> *always* failed), so it's probably not a regression.
>
> This is a shot against the odds, but could you please check if the attached
> patch has any effect?
Thanks, I'll try that. It may take a while because the problem only
happened once in dozens of suspend/resume cycles.
Jean-Marc
> Rafael
>
>
>
>
> ------------------------------------------------------------------------
>
> Both process_zones()and drain_node_pages() check for populated zones before
> touching pagesets. However, __drain_pages does not do so,
>
> This may result in a NULL pointer dereference for pagesets in unpopulated
> zones if a NUMA setup is combined with cpu hotplug.
>
> Initially the unpopulated zone has the pcp pointers pointing to the boot
> pagesets. Since the zone is not populated the boot pageset pointers will
> not be changed during page allocator and slab bootstrap.
>
> If a cpu is later brought down (first call to __drain_pages()) then the pcp
> pointers for cpus in unpopulated zones are set to NULL since __drain_pages
> does not first check for an unpopulated zone.
>
> If the cpu is then brought up again then we call process_zones() which will ignore
> the unpopulated zone. So the pageset pointers will still be NULL.
>
> If the cpu is then again brought down then __drain_pages will attempt to drain
> pages by following the NULL pageset pointer for unpopulated zones.
>
> Signed-off-by: Christoph Lameter <[email protected]>
>
> ---
> mm/page_alloc.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> Index: linux-2.6.20-rc4/mm/page_alloc.c
> ===================================================================
> --- linux-2.6.20-rc4.orig/mm/page_alloc.c
> +++ linux-2.6.20-rc4/mm/page_alloc.c
> @@ -714,6 +714,9 @@ static void __drain_pages(unsigned int c
> if (!populated_zone(zone))
> continue;
>
> + if (!populated_zone(zone))
> + continue;
> +
> pset = zone_pcp(zone, cpu);
> for (i = 0; i < ARRAY_SIZE(pset->pcp); i++) {
> struct per_cpu_pages *pcp;
-
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