move Rust sources to top level, C sources into c_src

[bcachefs-tools-debian] / c_src / include / linux / osq_lock.h

diff --git a/c_src/include/linux/osq_lock.h b/c_src/include/linux/osq_lock.h
new file mode 100644 (file)
index 0000000..bde9f0d
--- /dev/null
+++ b/c_src/include/linux/osq_lock.h
@@ -0,0 +1,44 @@
+#ifndef __LINUX_OSQ_LOCK_H
+#define __LINUX_OSQ_LOCK_H
+
+/*
+ * An MCS like lock especially tailored for optimistic spinning for sleeping
+ * lock implementations (mutex, rwsem, etc).
+ */
+struct optimistic_spin_node {
+       struct optimistic_spin_node *next, *prev;
+       int locked; /* 1 if lock acquired */
+       int cpu; /* encoded CPU # + 1 value */
+};
+
+struct optimistic_spin_queue {
+       /*
+        * Stores an encoded value of the CPU # of the tail node in the queue.
+        * If the queue is empty, then it's set to OSQ_UNLOCKED_VAL.
+        */
+       atomic_t tail;
+};
+
+#define OSQ_UNLOCKED_VAL (0)
+
+/* Init macro and function. */
+#define OSQ_LOCK_UNLOCKED { ATOMIC_INIT(OSQ_UNLOCKED_VAL) }
+
+static inline void osq_lock_init(struct optimistic_spin_queue *lock)
+{
+       atomic_set(&lock->tail, OSQ_UNLOCKED_VAL);
+}
+
+static inline bool osq_lock(struct optimistic_spin_queue *lock)
+{
+       return false;
+}
+
+static inline void osq_unlock(struct optimistic_spin_queue *lock) {}
+
+static inline bool osq_is_locked(struct optimistic_spin_queue *lock)
+{
+       return atomic_read(&lock->tail) != OSQ_UNLOCKED_VAL;
+}
+
+#endif