1 files changed, 20 insertions, 3 deletions

diff --git a/lib/lockref.c b/lib/lockref.c
index 677d036cf3c7..6f9d434c1521 100644
--- a/lib/lockref.c
+++ b/lib/lockref.c
@@ -4,6 +4,22 @@
 #ifdef CONFIG_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
  * failure case.
  */
@@ -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 = cmpxchg64(&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)