user-level mutex implementation for use by other parts of libc

include/core/mutex.h

@@ -0,0 +1,15 @@
+
+#ifndef __CORE_MUTEX_H__
+#define __CORE_MUTEX_H__
+
+typedef struct Mutex {
+    uint64_t	lock;
+} Mutex;
+
+int CoreMutex_Init(Mutex *mtx);
+void CoreMutex_Lock(Mutex *mtx);
+bool CoreMutex_TryLock(Mutex *mtx);
+void CoreMutex_Unlock(Mutex *mtx);
+
+#endif /* __CORE_MUTEX_H__ */
+

lib/libc/core/mutex.c

@@ -0,0 +1,35 @@
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#include <core/mutex.h>
+
+int
+CoreMutex_Init(Mutex *mtx)
+{
+}
+
+
+void
+CoreMutex_Lock(Mutex *mtx)
+{
+    while (__sync_lock_test_and_set(&mtx->lock, 1) == 1) {
+    }
+}
+
+bool
+CoreMutex_TryLock(Mutex *mtx)
+{
+    if (__sync_lock_test_and_set(&mtx->lock, 1) == 1) {
+	return false;
+    } else {
+	return true;
+    }
+}
+
+void
+CoreMutex_Unlock(Mutex *mtx)
+{
+    __sync_lock_release(&mtx->lock);
+}
+