s390/percpu: implement this_cpu_xchg()
The generic variant has a local_irq_save/restore pair which is quite
expensive. It is sufficient to disable preemption, which is a no-op
with !CONFIG_PREEMPT and then use the regular xchg macro.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/percpu.h b/arch/s390/include/asm/percpu.h
index 6537e72..7adebfc 100644
--- a/arch/s390/include/asm/percpu.h
+++ b/arch/s390/include/asm/percpu.h
@@ -84,6 +84,24 @@
#define this_cpu_cmpxchg_4(pcp, oval, nval) arch_this_cpu_cmpxchg(pcp, oval, nval)
#define this_cpu_cmpxchg_8(pcp, oval, nval) arch_this_cpu_cmpxchg(pcp, oval, nval)
+#define arch_this_cpu_xchg(pcp, nval) \
+({ \
+ typeof(pcp) *ptr__; \
+ typeof(pcp) ret__; \
+ preempt_disable(); \
+ ptr__ = __this_cpu_ptr(&(pcp)); \
+ ret__ = xchg(ptr__, nval); \
+ preempt_enable(); \
+ ret__; \
+})
+
+#define this_cpu_xchg_1(pcp, nval) arch_this_cpu_xchg(pcp, nval)
+#define this_cpu_xchg_2(pcp, nval) arch_this_cpu_xchg(pcp, nval)
+#define this_cpu_xchg_4(pcp, nval) arch_this_cpu_xchg(pcp, nval)
+#ifdef CONFIG_64BIT
+#define this_cpu_xchg_8(pcp, nval) arch_this_cpu_xchg(pcp, nval)
+#endif
+
#include <asm-generic/percpu.h>
#endif /* __ARCH_S390_PERCPU__ */