From: Aneesh Kumar K.V Date: Wed, 13 Aug 2014 07:02:02 +0000 (+0530) Subject: powerpc/thp: Use ACCESS_ONCE when loading pmdp X-Git-Tag: upstream/snapshot3+hdmi~1752 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=367136a453ce72a17aa3a32153ccc9cd290f004d;p=platform%2Fadaptation%2Frenesas_rcar%2Frenesas_kernel.git powerpc/thp: Use ACCESS_ONCE when loading pmdp commit 7e467245bf5226db34c4b12d3cbacfa2f7a15a8b upstream. We would get wrong results in compiler recomputed old_pmd. Avoid that by using ACCESS_ONCE Signed-off-by: Aneesh Kumar K.V Signed-off-by: Benjamin Herrenschmidt Signed-off-by: Greg Kroah-Hartman --- diff --git a/arch/powerpc/mm/hugepage-hash64.c b/arch/powerpc/mm/hugepage-hash64.c index 1fb609d..5f5e632 100644 --- a/arch/powerpc/mm/hugepage-hash64.c +++ b/arch/powerpc/mm/hugepage-hash64.c @@ -84,7 +84,9 @@ int __hash_page_thp(unsigned long ea, unsigned long access, unsigned long vsid, * atomically mark the linux large page PMD busy and dirty */ do { - old_pmd = pmd_val(*pmdp); + pmd_t pmd = ACCESS_ONCE(*pmdp); + + old_pmd = pmd_val(pmd); /* If PMD busy, retry the access */ if (unlikely(old_pmd & _PAGE_BUSY)) return 0;