Commit 7e467245 authored Aug 13, 2014 by Aneesh Kumar K.V Committed by Benjamin Herrenschmidt Aug 13, 2014

powerpc/thp: Use ACCESS_ONCE when loading pmdp



We would get wrong results in compiler recomputed old_pmd. Avoid
that by using ACCESS_ONCE

CC: <stable@vger.kernel.org>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

parent 969b7b20

arch/powerpc/mm/hugepage-hash64.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -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;