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: <[email protected]> Signed-off-by: Aneesh Kumar K.V <[email protected]> Signed-off-by: Benjamin Herrenschmidt <[email protected]>
rtvt123 · Aug 13, 2014 · 7e46724 · 7e46724
1 parent 969b7b2
commit 7e46724
Showing 1 changed file with 3 additions and 1 deletion.
diff --git 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;