thread/Mutex: don't use std::mutex

Use a custom pthread_mutex_t wrapper because std::mutex adds overhead.

Makefile.am

@@ -167,6 +167,7 @@ src_mpd_SOURCES = \
 	$(OUTPUT_API_SRC) \
 	$(MIXER_API_SRC) \
 	src/thread/Mutex.hxx \
+	src/thread/PosixMutex.hxx \
 	src/thread/CriticalSection.hxx \
 	src/glib_socket.h \
 	src/clock.c src/clock.h \

src/thread/Mutex.hxx

@@ -27,6 +27,14 @@
 #include "CriticalSection.hxx"
 typedef CriticalSection Mutex;
 
+#else
+
+#include "PosixMutex.hxx"
+
+typedef PosixMutex Mutex;
+
+#endif
+
 class ScopeLock {
 	Mutex &mutex;
 
@@ -43,12 +51,4 @@ public:
 	ScopeLock &operator=(const ScopeLock &other) = delete;
 };
 
-#else
-
-#include <mutex>
-typedef std::mutex Mutex;
-typedef std::lock_guard<std::mutex> ScopeLock;
-
-#endif
-
 #endif

src/thread/PosixMutex.hxx

@@ -0,0 +1,60 @@
+/*
+ * Copyright (C) 2009-2013 Max Kellermann <max@duempel.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef MPD_THREAD_POSIX_MUTEX_HXX
+#define MPD_THREAD_POSIX_MUTEX_HXX
+
+#include <pthread.h>
+
+/**
+ * Low-level wrapper for a pthread_mutex_t.
+ */
+class PosixMutex {
+  pthread_mutex_t mutex;
+
+public:
+  constexpr PosixMutex():mutex(PTHREAD_MUTEX_INITIALIZER) {}
+
+  PosixMutex(const PosixMutex &other) = delete;
+  PosixMutex &operator=(const PosixMutex &other) = delete;
+
+  void lock() {
+    pthread_mutex_lock(&mutex);
+  }
+
+  bool try_lock() {
+    return pthread_mutex_trylock(&mutex) == 0;
+  }
+
+  void unlock() {
+    pthread_mutex_unlock(&mutex);
+  }
+};
+
+#endif