From 367136a453ce72a17aa3a32153ccc9cd290f004d Mon Sep 17 00:00:00 2001 From: "Aneesh Kumar K.V" Date: Wed, 13 Aug 2014 12:32:02 +0530 Subject: [PATCH] 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 --- arch/powerpc/mm/hugepage-hash64.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) 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; -- 2.7.4