current/SOURCES/s390-percpu-add-read_once-to-arch_this_cpu_to_op_simple.patch

From e3f360db08d55a14112bd27454e616a24296a8b0 Mon Sep 17 00:00:00 2001
From: Heiko Carstens <hca@linux.ibm.com>
Date: Mon, 9 Jan 2023 11:51:20 +0100
Subject: s390/percpu: add READ_ONCE() to arch_this_cpu_to_op_simple()

From: Heiko Carstens <hca@linux.ibm.com>

commit e3f360db08d55a14112bd27454e616a24296a8b0 upstream.

Make sure that *ptr__ within arch_this_cpu_to_op_simple() is only
dereferenced once by using READ_ONCE(). Otherwise the compiler could
generate incorrect code.

Cc: <stable@vger.kernel.org>
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/s390/include/asm/percpu.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/s390/include/asm/percpu.h
+++ b/arch/s390/include/asm/percpu.h
@@ -31,7 +31,7 @@
        pcp_op_T__ *ptr__;                                              \
        preempt_disable_notrace();                                      \
        ptr__ = raw_cpu_ptr(&(pcp));                                    \
-       prev__ = *ptr__;                                                \
+       prev__ = READ_ONCE(*ptr__);                                     \
        do {                                                            \
                old__ = prev__;                                         \
                new__ = old__ op (val);                                 \
1	From e3f360db08d55a14112bd27454e616a24296a8b0 Mon Sep 17 00:00:00 2001
2	From: Heiko Carstens <hca@linux.ibm.com>
3	Date: Mon, 9 Jan 2023 11:51:20 +0100
4	Subject: s390/percpu: add READ_ONCE() to arch_this_cpu_to_op_simple()
5
6	From: Heiko Carstens <hca@linux.ibm.com>
7
8	commit e3f360db08d55a14112bd27454e616a24296a8b0 upstream.
9
10	Make sure that *ptr__ within arch_this_cpu_to_op_simple() is only
11	dereferenced once by using READ_ONCE(). Otherwise the compiler could
12	generate incorrect code.
13
14	Cc: <stable@vger.kernel.org>
15	Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
16	Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
17	Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
18	---
19	arch/s390/include/asm/percpu.h \| 2 +-
20	1 file changed, 1 insertion(+), 1 deletion(-)
21
22	--- a/arch/s390/include/asm/percpu.h
23	+++ b/arch/s390/include/asm/percpu.h
24	@@ -31,7 +31,7 @@
25	pcp_op_T__ *ptr__; \
26	preempt_disable_notrace(); \
27	ptr__ = raw_cpu_ptr(&(pcp)); \
28	- prev__ = *ptr__; \
29	+ prev__ = READ_ONCE(*ptr__); \
30	do { \
31	old__ = prev__; \
32	new__ = old__ op (val); \