7 files changed, 20 insertions, 10 deletions

diff --git a/arch/Kconfig b/arch/Kconfig
index 1feb169274fe..af2cc6eabcc7 100644
--- a/arch/Kconfig
+++ b/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
 
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index dcc6ac2d8026..7143793859fa 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -93,6 +93,7 @@ config S390
         select ARCH_INLINE_WRITE_UNLOCK_IRQ
         select ARCH_INLINE_WRITE_UNLOCK_IRQRESTORE
         select ARCH_SAVE_PAGE_KEYS if HIBERNATION
+        select ARCH_USE_CMPXCHG_LOCKREF
         select ARCH_WANT_IPC_PARSE_VERSION
         select BUILDTIME_EXTABLE_SORT
         select CLONE_BACKWARDS2
@@ -102,7 +103,6 @@ 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
diff --git a/arch/s390/include/asm/mutex.h b/arch/s390/include/asm/mutex.h
index 688271f5f2e4..458c1f7fbc18 100644
--- a/arch/s390/include/asm/mutex.h
+++ b/arch/s390/include/asm/mutex.h
@@ -7,5 +7,3 @@
  */
 
 #include <asm-generic/mutex-dec.h>
-
-#define arch_mutex_cpu_relax()  barrier()
diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h
index 0eb37505cab1..ca7821f07260 100644
--- a/arch/s390/include/asm/processor.h
+++ b/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));
diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/spinlock.h
index 701fe8c59e1f..83e5d216105e 100644
--- a/arch/s390/include/asm/spinlock.h
+++ b/arch/s390/include/asm/spinlock.h
@@ -44,6 +44,11 @@ extern void arch_spin_lock_wait_flags(arch_spinlock_t *, unsigned long flags);
 extern int arch_spin_trylock_retry(arch_spinlock_t *);
 extern void arch_spin_relax(arch_spinlock_t *lock);
 
+static inline int arch_spin_value_unlocked(arch_spinlock_t lock)
+{
+        return lock.owner_cpu == 0;
+}
+
 static inline void arch_spin_lock(arch_spinlock_t *lp)
 {
         int old;
diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index ccd4260834c5..bab49da8a0f0 100644
--- a/include/linux/mutex.h
+++ b/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
diff --git a/lib/lockref.c b/lib/lockref.c
index e294ae445c9a..6f9d434c1521 100644
--- a/lib/lockref.c
+++ b/lib/lockref.c
@@ -12,6 +12,14 @@
 #endif
 
 /*
+ * Allow architectures to override the default cpu_relax() within CMPXCHG_LOOP.
+ * This is useful for architectures with an expensive cpu_relax().
+ */
+#ifndef arch_mutex_cpu_relax
+# define arch_mutex_cpu_relax() cpu_relax()
+#endif
+
+/*
  * Note that the "cmpxchg()" reloads the "old" value for the
  * failure case.
  */
@@ -28,7 +36,7 @@
                 if (likely(old.lock_count == prev.lock_count)) {                \
                         SUCCESS;                                                \
                 }                                                               \
-                cpu_relax();                                                    \
+                arch_mutex_cpu_relax();                                         \
         }                                                                       \
 } while (0)