From: Heiko Carstens <hca@linux.ibm.com>
Date: Mon, 9 Jan 2023 10:51:20 +0000 (+0100)
Subject: s390/percpu: add READ_ONCE() to arch_this_cpu_to_op_simple()
X-Git-Tag: v6.6.7~3638^2~6
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=e3f360db08d55a14112bd27454e616a24296a8b0;p=platform%2Fkernel%2Flinux-starfive.git

s390/percpu: add READ_ONCE() to arch_this_cpu_to_op_simple()

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>
---

diff --git a/arch/s390/include/asm/percpu.h b/arch/s390/include/asm/percpu.h
index cb5fc06..081837b 100644
--- 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);					\