This is a note to let you know that I've just added the patch titled
parisc: Fix double-word compare and exchange in LWS code on 32-bit kernels
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
parisc-fix-double-word-compare-and-exchange-in-lws-code-on-32-bit-kernels.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 374b3bf8e8b519f61eb9775888074c6e46b3bf0c Mon Sep 17 00:00:00 2001
From: John David Anglin <dave.anglin@xxxxxxxx>
Date: Sat, 30 Sep 2017 17:24:23 -0400
Subject: parisc: Fix double-word compare and exchange in LWS code on 32-bit kernels
From: John David Anglin <dave.anglin@xxxxxxxx>
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 <dave.anglin@xxxxxxxx>
Tested-by: Christoph Biedl <debian.axhn@xxxxxxxxxxxxxxxxxx>
Fixes: 89206491201c ("parisc: Implement new LWS CAS supporting 64 bit operations.")
Signed-off-by: Helge Deller <deller@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
@@ -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 */
Patches currently in stable-queue which might be from dave.anglin@xxxxxxxx are
queue-4.4/parisc-fix-double-word-compare-and-exchange-in-lws-code-on-32-bit-kernels.patch
queue-4.4/parisc-avoid-trashing-sr2-and-sr3-in-lws-code.patch