From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754860AbdL1Rof (ORCPT ); Thu, 28 Dec 2017 12:44:35 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:60203 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932523AbdL1RdY (ORCPT ); Thu, 28 Dec 2017 12:33:24 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Helge Deller" , "John David Anglin" , "Christoph Biedl" Date: Thu, 28 Dec 2017 17:05:44 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 127/204] parisc: Fix double-word compare and exchange in LWS code on 32-bit kernels In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.52-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: John David Anglin commit 374b3bf8e8b519f61eb9775888074c6e46b3bf0c upstream. As discussed on the debian-hppa list, double-wordcompare and exchange operations fail on 32-bit kernels. Looking at the code, I realized that the ",ma" completer does the wrong thing in the "ldw,ma 4(%r26), %r29" instruction. This increments %r26 and causes the following store to write to the wrong location. Note by Helge Deller: The patch applies cleanly to stable kernel series if this upstream commit is merged in advance: f4125cfdb300 ("parisc: Avoid trashing sr2 and sr3 in LWS code"). Signed-off-by: John David Anglin Tested-by: Christoph Biedl Fixes: 89206491201c ("parisc: Implement new LWS CAS supporting 64 bit operations.") Signed-off-by: Helge Deller [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- arch/parisc/kernel/syscall.S | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/arch/parisc/kernel/syscall.S +++ b/arch/parisc/kernel/syscall.S @@ -742,7 +742,7 @@ lws_compare_and_swap_2: 10: ldd 0(%sr3,%r25), %r25 11: ldd 0(%sr3,%r24), %r24 #else - /* Load new value into r22/r23 - high/low */ + /* Load old value into r22/r23 - high/low */ 10: ldw 0(%sr3,%r25), %r22 11: ldw 4(%sr3,%r25), %r23 /* Load new value into fr4 for atomic store later */ @@ -834,11 +834,11 @@ cas2_action: copy %r0, %r28 #else /* Compare first word */ -19: ldw,ma 0(%sr3,%r26), %r29 +19: ldw 0(%sr3,%r26), %r29 sub,= %r29, %r22, %r0 b,n cas2_end /* Compare second word */ -20: ldw,ma 4(%sr3,%r26), %r29 +20: ldw 4(%sr3,%r26), %r29 sub,= %r29, %r23, %r0 b,n cas2_end /* Perform the store */