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Date: Mon, 15 Sep 2014 12:24:44 -0700 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>, Benjamin Herrenschmidt <benh@...nel.crashing.org> Subject: [PATCH 3.16 045/158] powerpc/thp: Use ACCESS_ONCE when loading pmdp 3.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com> 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 <aneesh.kumar@...ux.vnet.ibm.com> Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- arch/powerpc/mm/hugepage-hash64.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- 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, un * 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; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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