From 9a8835679e67ae4b031405ab32a690c5d98e94a6 Mon Sep 17 00:00:00 2001 From: John David Anglin Date: Sat, 30 Sep 2017 17:24:23 -0400 Subject: [PATCH] parisc: Fix double-word compare and exchange in LWS code on 32-bit kernels 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 Signed-off-by: Greg Kroah-Hartman --- arch/parisc/kernel/syscall.S | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S index a6d7de8cc47d4..95f090fe385a0 100644 --- a/arch/parisc/kernel/syscall.S +++ b/arch/parisc/kernel/syscall.S @@ -740,7 +740,7 @@ lws_compare_and_swap_2: 10: ldd 0(%r25), %r25 11: ldd 0(%r24), %r24 #else - /* Load new value into r22/r23 - high/low */ + /* Load old value into r22/r23 - high/low */ 10: ldw 0(%r25), %r22 11: ldw 4(%r25), %r23 /* Load new value into fr4 for atomic store later */ @@ -832,11 +832,11 @@ cas2_action: copy %r0, %r28 #else /* Compare first word */ -19: ldw,ma 0(%r26), %r29 +19: ldw 0(%r26), %r29 sub,= %r29, %r22, %r0 b,n cas2_end /* Compare second word */ -20: ldw,ma 4(%r26), %r29 +20: ldw 4(%r26), %r29 sub,= %r29, %r23, %r0 b,n cas2_end /* Perform the store */