mutex: replace CONFIG_HAVE_ARCH_MUTEX_CPU_RELAX with simple ifdef

Linus suggested to replace

 #ifndef CONFIG_HAVE_ARCH_MUTEX_CPU_RELAX
 #define arch_mutex_cpu_relax() cpu_relax()
 #endif

with just a simple

  #ifndef arch_mutex_cpu_relax
  # define arch_mutex_cpu_relax() cpu_relax()
  #endif

to get rid of CONFIG_HAVE_CPU_RELAX_SIMPLE. So architectures can
simply define arch_mutex_cpu_relax if they want an architecture
specific function instead of having to add a select statement in
their Kconfig in addition.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

arch/Kconfig

@@ -286,9 +286,6 @@ config HAVE_PERF_USER_STACK_DUMP
 config HAVE_ARCH_JUMP_LABEL
 	bool
 
-config HAVE_ARCH_MUTEX_CPU_RELAX
-	bool
-
 config HAVE_RCU_TABLE_FREE
 	bool
 

arch/s390/Kconfig

@@ -102,7 +102,6 @@ config S390
 	select GENERIC_TIME_VSYSCALL_OLD
 	select HAVE_ALIGNED_STRUCT_PAGE if SLUB
 	select HAVE_ARCH_JUMP_LABEL if !MARCH_G5
-	select HAVE_ARCH_MUTEX_CPU_RELAX
 	select HAVE_ARCH_SECCOMP_FILTER
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_ARCH_TRANSPARENT_HUGEPAGE if 64BIT

arch/s390/include/asm/mutex.h

@@ -7,5 +7,3 @@
  */
 
 #include <asm-generic/mutex-dec.h>
-
-#define arch_mutex_cpu_relax()	barrier()

arch/s390/include/asm/processor.h

@@ -198,6 +198,8 @@ static inline void cpu_relax(void)
 	barrier();
 }
 
+#define arch_mutex_cpu_relax()  barrier()
+
 static inline void psw_set_key(unsigned int key)
 {
 	asm volatile("spka 0(%0)" : : "d" (key));

include/linux/mutex.h

@@ -15,8 +15,8 @@
 #include <linux/spinlock_types.h>
 #include <linux/linkage.h>
 #include <linux/lockdep.h>
-
 #include <linux/atomic.h>
+#include <asm/processor.h>
 
 /*
  * Simple, straightforward mutexes with strict semantics:
@@ -175,8 +175,8 @@ extern void mutex_unlock(struct mutex *lock);
 
 extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
 
-#ifndef CONFIG_HAVE_ARCH_MUTEX_CPU_RELAX
-#define arch_mutex_cpu_relax()	cpu_relax()
+#ifndef arch_mutex_cpu_relax
+# define arch_mutex_cpu_relax() cpu_relax()
 #endif
 
 #endif