On Fri, Feb 28, 2014 at 02:32:02PM +0530, Aneesh Kumar K.V wrote:
> From: Liu Ping Fan <pingfank@xxxxxxxxxxxxxxxxxx>
>
> When doing some numa tests on powerpc, I triggered an oops bug. I find
> it is caused by using page->_last_cpupid. It should be initialized as
> "-1 & LAST_CPUPID_MASK", but not "-1". Otherwise, in task_numa_fault(),
> we will miss the checking (last_cpupid == (-1 & LAST_CPUPID_MASK)).
> And finally cause an oops bug in task_numa_group(), since the online cpu is
> less than possible cpu. This happen with CONFIG_SPARSE_VMEMMAP disabled
>
> Signed-off-by: Liu Ping Fan <pingfank@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> ---
>
> include/linux/mm.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index f28f46eade6a..86245839c9fa 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -757,7 +757,7 @@ static inline bool __cpupid_match_pid(pid_t task_pid, int cpupid)
> #ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS
> static inline int page_cpupid_xchg_last(struct page *page, int cpupid)
> {
> - return xchg(&page->_last_cpupid, cpupid);
> + return xchg(&page->_last_cpupid, cpupid & LAST_CPUPID_MASK);
> }
>
> static inline int page_cpupid_last(struct page *page)
> @@ -766,7 +766,7 @@ static inline int page_cpupid_last(struct page *page)
> }
> static inline void page_cpupid_reset_last(struct page *page)
> {
> - page->_last_cpupid = -1;
> + page->_last_cpupid = -1 & LAST_CPUPID_MASK;
> }
> #else
> static inline int page_cpupid_last(struct page *page)
> --
> 1.8.3.2
>
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