diff --git a/src/lib/utils/thread.cpp b/src/lib/utils/thread.cpp
index 205a7d69..ed2fc961 100755
--- a/src/lib/utils/thread.cpp
+++ b/src/lib/utils/thread.cpp
@@ -84,25 +84,54 @@ WaitThread::~WaitThread() {
 void WaitThread::stop() {
   pthread_mutex_lock(&m_mutex);
   pthread_cond_signal(&m_cond);
-  pthread_mutex_unlock(&m_mutex);
   Thread::stop();
+  pthread_mutex_unlock(&m_mutex);
 }
 
 bool WaitThread::join() {
-  pthread_mutex_lock(&m_mutex);
-  pthread_cond_signal(&m_cond);
-  pthread_mutex_unlock(&m_mutex);
+  stop();
   return Thread::join();
 }
 
 bool WaitThread::Wait(int seconds) {
+  pthread_mutex_lock(&m_mutex);
   struct timespec t;
   clockGettime(&t);
   t.tv_sec += seconds;
-  pthread_mutex_lock(&m_mutex);
   pthread_cond_timedwait(&m_cond, &m_mutex, &t);
   pthread_mutex_unlock(&m_mutex);
   return isRunning();
 }
 
+
+NotifiableThread::NotifiableThread()
+    : WaitThread(), m_notified(false) {
+}
+
+void NotifiableThread::notify() {
+  pthread_mutex_lock(&m_mutex);
+  pthread_cond_signal(&m_cond);
+  m_notified = true;
+  pthread_mutex_unlock(&m_mutex);
+}
+
+bool NotifiableThread::waitNotified(int millis) {
+  pthread_mutex_lock(&m_mutex);
+  if (!m_notified) {
+    struct timespec t;
+    clockGettime(&t);
+    t.tv_sec += millis / 1000000000;
+    t.tv_nsec += (millis % 1000000000) * 1000000;
+    if (t.tv_nsec > 1000000000) {
+      t.tv_sec++;
+      t.tv_nsec -= 1000000000;
+    }
+    pthread_cond_timedwait(&m_cond, &m_mutex, &t);
+  }
+  bool notified = m_notified;
+  m_notified = false;
+  pthread_mutex_unlock(&m_mutex);
+  return notified;
+}
+
 }  // namespace ebusd
diff --git a/src/lib/utils/thread.h b/src/lib/utils/thread.h
index de2e5e0b..d5b57278 100755
--- a/src/lib/utils/thread.h
+++ b/src/lib/utils/thread.h
@@ -1,6 +1,6 @@
 /*
  * ebusd - daemon for communication with eBUS heating systems.
- * Copyright (C) 2014-2018 John Baier <ebusd@ebusd.eu>, Roland Jax 2012-2014 <ebusd@liwest.at>
+ * Copyright (C) 2014-2020 John Baier <ebusd@ebusd.eu>, Roland Jax 2012-2014 <ebusd@liwest.at>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -26,7 +26,7 @@ namespace ebusd {
 /** \file lib/utils/thread.h */
 
 /**
- * wrapper class for pthread.
+ * Wrapper class for pthread.
  */
 class Thread {
  public:
@@ -82,7 +82,7 @@ class Thread {
   /**
    * Thread entry method to be overridden by derived class.
    */
-  virtual void run() = 0;
+  virtual void run() = 0;  // abstract
 
 
  private:
@@ -134,7 +134,7 @@ class WaitThread : public Thread {
   bool Wait(int seconds);
 
 
- private:
+ protected:
   /** the mutex for waiting. */
   pthread_mutex_t m_mutex;
 
@@ -143,6 +143,35 @@ class WaitThread : public Thread {
 };
 
 
+/**
+ * A @a WaitThread that can be waited on.
+ */
+class NotifiableThread : public WaitThread {
+ public:
+  /**
+   * Constructor.
+   */
+  NotifiableThread();
+
+  /**
+   * Notify another thread currently in @a wait().
+   */
+  void notify();
+
+  /**
+   * Wait for getting notified up to the specified amount of time.
+   * @param millis the maximum number of milliseconds to wait.
+   * @return true if @a notify() was called while waiting.
+   */
+  bool waitNotified(int millis);
+
+
+ private:
+  /** whether @a notify() was called while waiting. */
+  bool m_notified;
+};
+
+
 /**
  * A simple mutex.
  */