Clean up and document our hacks for building BSD source.

Change-Id: Ic591e22fa5b363bb68376b9f25814c0e5bd83fbf

libc/upstream-netbsd/android/include/reentrant.h

@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef _BIONIC_NETBSD_REENTRANT_H_included
+#define _BIONIC_NETBSD_REENTRANT_H_included
+
+#define _REENTRANT
+
+#include <pthread.h>
+#include <signal.h>
+
+//
+// Map NetBSD libc internal locking to pthread locking.
+//
+
+#define MUTEX_INITIALIZER PTHREAD_MUTEX_INITIALIZER
+#define mutex_t pthread_mutex_t
+#define mutex_lock(x) pthread_mutex_lock(x)
+#define mutex_unlock(x) pthread_mutex_unlock(x)
+
+#define RWLOCK_INITIALIZER PTHREAD_RWLOCK_INITIALIZER
+#define rwlock_t pthread_rwlock_t
+#define rwlock_rdlock pthread_rwlock_rdlock
+#define rwlock_unlock pthread_rwlock_unlock
+#define rwlock_wrlock pthread_rwlock_wrlock
+
+#endif