1 files changed, 36 insertions, 0 deletions

diff --git a/include/linux/lockref.h b/include/linux/lockref.h
new file mode 100644
index 000000000000..ca07b5028b01
--- /dev/null
+++ b/include/linux/lockref.h
@@ -0,0 +1,36 @@
+#ifndef __LINUX_LOCKREF_H
+#define __LINUX_LOCKREF_H
+
+/*
+ * Locked reference counts.
+ *
+ * These are different from just plain atomic refcounts in that they
+ * are atomic with respect to the spinlock that goes with them.  In
+ * particular, there can be implementations that don't actually get
+ * the spinlock for the common decrement/increment operations, but they
+ * still have to check that the operation is done semantically as if
+ * the spinlock had been taken (using a cmpxchg operation that covers
+ * both the lock and the count word, or using memory transactions, for
+ * example).
+ */
+
+#include <linux/spinlock.h>
+
+struct lockref {
+        union {
+#ifdef CONFIG_CMPXCHG_LOCKREF
+                aligned_u64 lock_count;
+#endif
+                struct {
+                        spinlock_t lock;
+                        unsigned int count;
+                };
+        };
+};
+
+extern void lockref_get(struct lockref *);
+extern int lockref_get_not_zero(struct lockref *);
+extern int lockref_get_or_lock(struct lockref *);
+extern int lockref_put_or_lock(struct lockref *);
+
+#endif /* __LINUX_LOCKREF_H */