Add thread safety annotated wrapper for std::mutex

Co-authored-by: Anthony Towns <aj@erisian.com.au>

src/logging.h

@@ -62,7 +62,7 @@ namespace BCLog {
     class Logger
     {
     private:
-        mutable std::mutex m_cs;                   // Can not use Mutex from sync.h because in debug mode it would cause a deadlock when a potential deadlock was detected
+        mutable StdMutex m_cs; // Can not use Mutex from sync.h because in debug mode it would cause a deadlock when a potential deadlock was detected
 
         FILE* m_fileout GUARDED_BY(m_cs) = nullptr;
         std::list<std::string> m_msgs_before_open GUARDED_BY(m_cs);

src/threadsafety.h

@@ -56,12 +56,18 @@
 #define ASSERT_EXCLUSIVE_LOCK(...)
 #endif // __GNUC__
 
+// StdMutex provides an annotated version of std::mutex for us,
+// and should only be used when sync.h Mutex/LOCK/etc are not usable.
+class LOCKABLE StdMutex : public std::mutex
+{
+};
+
 // LockGuard provides an annotated version of lock_guard for us
 // should only be used when sync.h Mutex/LOCK/etc aren't usable
-class SCOPED_LOCKABLE LockGuard : public std::lock_guard<std::mutex>
+class SCOPED_LOCKABLE LockGuard : public std::lock_guard<StdMutex>
 {
 public:
-    explicit LockGuard(std::mutex& cs) EXCLUSIVE_LOCK_FUNCTION(cs) : std::lock_guard<std::mutex>(cs) { }
+    explicit LockGuard(StdMutex& cs) EXCLUSIVE_LOCK_FUNCTION(cs) : std::lock_guard<StdMutex>(cs) {}
     ~LockGuard() UNLOCK_FUNCTION() {};
 };