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

stable inclusion
from stable-v5.10.164
commit 51dbedee2ff3b000c9905189e33e1972b6c9f649
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7T7G4

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=51dbedee2ff3b000c9905189e33e1972b6c9f649

--------------------------------

commit e3f360db 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: NAlexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: NHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Nsanglipeng <sanglipeng1@jd.com>

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);					\