logd: use RAII locks and thread annotations
Test: unit tests
Change-Id: I38623130a96f17a47ed79753e24b25efa9e38279
diff --git a/logd/rwlock.h b/logd/rwlock.h
new file mode 100644
index 0000000..2b27ff1
--- /dev/null
+++ b/logd/rwlock.h
@@ -0,0 +1,56 @@
+/*
+ * Copyright (C) 2020 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/LICENSE2.0
+ *
+ * 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.
+ */
+
+#pragma once
+
+#include <pthread.h>
+
+#include <android-base/macros.h>
+#include <android-base/thread_annotations.h>
+
+// As of the end of May 2020, std::shared_mutex is *not* simply a pthread_rwlock, but rather a
+// combination of std::mutex and std::condition variable, which is obviously less efficient. This
+// immitates what std::shared_mutex should be doing and is compatible with RAII thread wrappers.
+
+class SHARED_CAPABILITY("mutex") RwLock {
+ public:
+ RwLock() {}
+ ~RwLock() {}
+
+ void lock() ACQUIRE() { pthread_rwlock_wrlock(&rwlock_); }
+ void lock_shared() ACQUIRE_SHARED() { pthread_rwlock_rdlock(&rwlock_); }
+
+ void unlock() RELEASE() { pthread_rwlock_unlock(&rwlock_); }
+
+ private:
+ pthread_rwlock_t rwlock_ = PTHREAD_RWLOCK_INITIALIZER;
+};
+
+// std::shared_lock does not have thread annotations, so we need our own.
+
+class SCOPED_CAPABILITY SharedLock {
+ public:
+ SharedLock(RwLock& lock) ACQUIRE_SHARED(lock) : lock_(lock) { lock_.lock_shared(); }
+ ~SharedLock() RELEASE() { lock_.unlock(); }
+
+ void lock_shared() ACQUIRE_SHARED() { lock_.lock_shared(); }
+ void unlock() RELEASE() { lock_.unlock(); }
+
+ DISALLOW_IMPLICIT_CONSTRUCTORS(SharedLock);
+
+ private:
+ RwLock& lock_;
+};