Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 3.16 045/158] powerpc/thp: Use ACCESS_ONCE when loading pmdp | Date | Mon, 15 Sep 2014 12:24:44 -0700 |
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3.16-stable review patch. If anyone has any objections, please let me know.
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From: "Aneesh Kumar K.V" <aneesh.kumar@linux.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@linux.vnet.ibm.com> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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;
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