From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
To: benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au
Cc: linuxppc-dev@lists.ozlabs.org,
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Subject: [PATCH 6/8] powerpc: thp: use ACCESS_ONCE when loading pmdp
Date: Tue, 29 Jul 2014 15:07:47 +0530 [thread overview]
Message-ID: <1406626669-31154-7-git-send-email-aneesh.kumar@linux.vnet.ibm.com> (raw)
In-Reply-To: <1406626669-31154-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com>
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>
---
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 1fb609dcc49b..5f5e6328c21c 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;
--
1.9.1
next prev parent reply other threads:[~2014-07-29 9:38 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-29 9:37 [PATCH 0/8] THP fixes for ppc64 Aneesh Kumar K.V
2014-07-29 9:37 ` [PATCH 1/8] powerpc: thp: Add write barrier after updating the valid bit Aneesh Kumar K.V
2014-07-29 9:37 ` [PATCH 2/8] powerpc: thp: don't recompute vsid and ssize in loop on invalidate Aneesh Kumar K.V
2014-07-29 9:37 ` [PATCH 3/8] powerpc: thp: invalidate old 64K based hash page mapping before insert of 4k pte Aneesh Kumar K.V
2014-07-29 9:37 ` [PATCH 4/8] powerpc: thp: Handle combo pages in invalidate Aneesh Kumar K.V
2014-07-29 9:37 ` [PATCH 5/8] powerpc: thp: inalidate with vpn in loop Aneesh Kumar K.V
2014-07-29 9:37 ` Aneesh Kumar K.V [this message]
2014-07-29 9:37 ` [PATCH 7/8] powerpc: mm: Use read barrier when creating real_pte Aneesh Kumar K.V
2014-07-29 9:37 ` [PATCH 8/8] powerpc: thp: Add tracepoints to track hugepage invalidate Aneesh Kumar K.V
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