Merge commit v3.13-rc1 into kbuild/misc

1 files changed, 22 insertions, 4 deletions

diff --git a/lib/lockref.c b/lib/lockref.c
index e2cd2c0a8821..d2b123f8456b 100644
--- a/lib/lockref.c
+++ b/lib/lockref.c
@@ -1,7 +1,23 @@
 #include <linux/export.h>
 #include <linux/lockref.h>
 
-#ifdef CONFIG_CMPXCHG_LOCKREF
+#if USE_CMPXCHG_LOCKREF
+
+/*
+ * Allow weakly-ordered memory architectures to provide barrier-less
+ * cmpxchg semantics for lockref updates.
+ */
+#ifndef cmpxchg64_relaxed
+# define cmpxchg64_relaxed cmpxchg64
+#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
@@ -14,12 +30,13 @@
         while (likely(arch_spin_value_unlocked(old.lock.rlock.raw_lock))) {     \
                 struct lockref new = old, prev = old;                           \
                 CODE                                                            \
-                old.lock_count = cmpxchg(&lockref->lock_count,                  \
-                                         old.lock_count, new.lock_count);       \
+                old.lock_count = cmpxchg64_relaxed(&lockref->lock_count,        \
+                                                   old.lock_count,              \
+                                                   new.lock_count);             \
                 if (likely(old.lock_count == prev.lock_count)) {                \
                         SUCCESS;                                                \
                 }                                                               \
-                cpu_relax();                                                    \
+                arch_mutex_cpu_relax();                                         \
         }                                                                       \
 } while (0)
 
@@ -136,6 +153,7 @@ void lockref_mark_dead(struct lockref *lockref)
         assert_spin_locked(&lockref->lock);
         lockref->count = -128;
 }
+EXPORT_SYMBOL(lockref_mark_dead);
 
 /**
  * lockref_get_not_dead - Increments count unless the ref is dead