kernel: add futex definitions

include/kernel/futex.h

@@ -0,0 +1,26 @@
+#ifndef KERNEL_FUTEX_H_
+#define KERNEL_FUTEX_H_
+
+#include <kernel/btree.h>
+#include <kernel/wait.h>
+#include <mango/types.h>
+
+struct address_space;
+
+typedef phys_addr_t futex_key_t;
+
+struct futex {
+	struct btree_node f_node;
+	futex_key_t f_key;
+	struct waitqueue f_waiters;
+};
+
+extern kern_status_t futex_init(void);
+extern kern_status_t futex_get(
+	struct address_space *space,
+	kern_futex_t *futex,
+	futex_key_t *out);
+extern kern_status_t futex_wait(futex_key_t futex, kern_futex_t new_val);
+extern kern_status_t futex_wake(futex_key_t futex, size_t nwaiters);
+
+#endif