diff --git a/.github/workflows/macos.yml b/.github/workflows/macos.yml
new file mode 100644
index 0000000..1971111
--- /dev/null
+++ b/.github/workflows/macos.yml
@@ -0,0 +1,44 @@
+---
+name: MacOS
+
+on:
+  push:
+    branches:
+      - master
+      - develop
+  pull_request:
+    branches:
+      - master
+      - develop
+
+env:
+  CTEST_OUTPUT_ON_FAILURE: 1
+  CPM_SOURCE_CACHE: ${{ github.workspace }}/cpm_modules
+
+jobs:
+  build:
+    runs-on: macos-latest
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - uses: actions/cache@v2
+        with:
+          path: "**/cpm_modules"
+          key: ${{ github.workflow }}-cpm-modules-${{ hashFiles('**/CMakeLists.txt', '**/*.cmake') }}
+
+      - name: Install boost libs
+        shell: bash
+        run: |
+          brew install boost
+
+      - name: configure
+        run: cmake -S . -B build -DCMAKE_BUILD_TYPE=Debug
+
+      - name: build
+        run: cmake --build build -j4
+
+      - name: test
+        run: |
+          cd build
+          ctest --build-config Debug --timeout 60
diff --git a/.github/workflows/ubuntu.yml b/.github/workflows/ubuntu.yml
new file mode 100644
index 0000000..1bae776
--- /dev/null
+++ b/.github/workflows/ubuntu.yml
@@ -0,0 +1,44 @@
+---
+name: Ubuntu
+
+on:
+  push:
+    branches:
+      - master
+      - develop
+  pull_request:
+    branches:
+      - master
+      - develop
+
+env:
+  CTEST_OUTPUT_ON_FAILURE: 1
+  CPM_SOURCE_CACHE: ${{ github.workspace }}/cpm_modules
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - uses: actions/cache@v2
+        with:
+          path: "**/cpm_modules"
+          key: ${{ github.workflow }}-cpm-modules-${{ hashFiles('**/CMakeLists.txt', '**/*.cmake') }}
+
+      - name: Install boost libs
+        shell: bash
+        run: |
+          sudo apt-get install libboost1.71-all-dev
+
+      - name: configure
+        run: cmake -S . -B build -DCMAKE_BUILD_TYPE=Debug
+
+      - name: build
+        run: cmake --build build -j4
+
+      - name: test
+        run: |
+          cd build
+          ctest --build-config Debug --timeout 60
diff --git a/CMakeLists.txt b/CMakeLists.txt
index c55eb68..0bb7d08 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -179,6 +179,10 @@ if(USE_BOOST OR BUILD_TESTING)
   # ----------------------------------------------------------------------
   # additional tests from me (CK)
   # ----------------------------------------------------------------------
+  if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+    # add_compile_options(-fsanitize=memory -fsanitize-memory-use-after-dtor)
+  endif()
+
   add_executable(test_mutexattr test_mutexattr.c)
   set_target_properties(test_mutexattr PROPERTIES CXX_STANDARD 99)
   target_link_libraries(test_mutexattr Threads::Threads)
diff --git a/GNUmakefile b/GNUmakefile
index 912c29b..8f7c8bf 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -26,7 +26,7 @@ CHECKS?='-*,cppcoreguidelines-*,cppcoreguidelines-pro-*,-cppcoreguidelines-avoid
 CHECKS?='-*,portability-*,readability-*'
 CHECKS?='-*,misc-*,boost-*,cert-*,misc-unused-parameters'
 
-#FIXME! ThreadSanitizer?=0
+#TBD: ThreadSanitizer?=0
 ifeq ($(BUILD_TYPE),Coverage)
     ThreadSanitizer:=0
 else
@@ -44,6 +44,7 @@ ifeq (${ThreadSanitizer},1)
     export CMAKE_INSTALL_PREFIX
     CMAKE_STAGING_PREFIX?=/tmp/staging/$(PROJECT_NAME)$(CMAKE_INSTALL_PREFIX)
     CMAKE_PREFIX_PATH?="$(CMAKE_STAGING_PREFIX);$(CMAKE_INSTALL_PREFIX);/usr/local/opt/boost;/usr/local/opt/openssl;/usr"
+    export MSAN_OPTIONS=poison_in_dtor=1
 endif
 
 
diff --git a/posix/threadpool.cpp b/posix/threadpool.cpp
index 53a4ecd..b199b92 100644
--- a/posix/threadpool.cpp
+++ b/posix/threadpool.cpp
@@ -89,45 +89,45 @@ Synchronized::Synchronized()
 
 Synchronized::~Synchronized()
 {
-    int error  = 0;
     int errors = 0;
 
+    notify_all(); // NOTE: just in case an other thread is waiting for the
+                  // signal! CK
+    int error =
+        pthread_mutex_unlock(&monitor); // in case the thread own the lock! CK
+    if (error) {
+        ++errors;
+    }
+
 #ifdef NO_FAST_MUTEXES
-    do {
-        // first try to get the lock
+    error = pthread_mutex_destroy(&monitor);
+    if (error) {
+        // wait for other threads ...
         error = pthread_mutex_trylock(&monitor);
-        if (!error) {
-            (void)pthread_mutex_unlock(&monitor);
-            // if another thread waits for signal with mutex, let's wait.
+        if (EBUSY == error) {
+            ++errors;
+            // another thread owns the mutex,
 
 #    if defined(_POSIX_TIMEOUTS) && _POSIX_TIMEOUTS > 0
-            if (lock(10)) // NOTE: but not forever! CK
-#    else
-            error = pthread_mutex_trylock(&monitor);
-            if (!error)
+            if (lock(100)) { // NOTE: but not forever! CK
+                pthread_mutex_unlock(&monitor);
+            }
 #    endif
-            {
-                (void)pthread_mutex_unlock(&monitor);
-                error = pthread_mutex_destroy(&monitor);
-                if (error) {
+
+            int retries = 0;
+            do {
+                error = pthread_mutex_trylock(&monitor);
+                if (!error) {
+                    pthread_mutex_unlock(&monitor);
+                    error = pthread_mutex_destroy(&monitor);
+                } else {
                     ++errors;
-                    Thread::sleep(errors * 2);
+                    sleep(errors * 2); // NOTE: prevent busy loops! CK
                 }
-            }
-        } else {
-            // in case this thread hold the lock:
-            error = pthread_mutex_unlock(&monitor);
-            if (error != EPERM) {
-                break;
-            }
-            notify_all();
-            ++errors;
-            Thread::sleep(errors * 2);
+            } while (EBUSY == error
+                && (retries++ < AGENTPP_SYNCHRONIZED_UNLOCK_RETRIES));
         }
-        if (errors > AGENTPP_SYNCHRONIZED_UNLOCK_RETRIES) {
-            break;
-        }
-    } while (EBUSY == error);
+    }
 #else
     error              = pthread_mutex_destroy(&monitor);
 #endif
@@ -307,7 +307,7 @@ bool Synchronized::lock(unsigned long timeout)
 #    else
     struct timeval tv = {};
     gettimeofday(&tv, 0);
-    ts.tv_sec = tv.tv_sec + (time_t)timeout / 1000;
+    ts.tv_sec   = tv.tv_sec + (time_t)timeout / 1000;
     long millis = tv.tv_usec / 1000 + (timeout % 1000);
     if (millis >= 1000) {
         ts.tv_sec += 1;
diff --git a/threads.cpp b/threads.cpp
index 6f1e4b9..30a722c 100644
--- a/threads.cpp
+++ b/threads.cpp
@@ -163,8 +163,10 @@ Synchronized::Synchronized()
 
 Synchronized::~Synchronized()
 {
+    int errors = 0;
     int result = pthread_cond_destroy(&cond);
     if (result) {
+        ++errors;
         LOG_BEGIN(loggerModuleName, ERROR_LOG | 2);
         LOG("Synchronized cond_destroy failed with (result)(ptr)");
         LOG(result);
@@ -178,12 +180,12 @@ Synchronized::~Synchronized()
         // wait for other threads ...
         if (EBUSY == pthread_mutex_trylock(&monitor)) {
             // another thread owns the mutex,
-            if (lock(123)) // NOTE: let's wait, but not forever! CK
+            if (lock()) // FIXME: let's wait, but not forever! CK
             {
                 int retries = 0;
                 do {
                     pthread_mutex_unlock(&monitor);
-                    sleep(13);
+                    sleep(13); // NOTE: prevent busy loops! CK
                     result = pthread_mutex_destroy(&monitor);
                 } while (EBUSY == result
                     && (retries++ < AGENTPP_SYNCHRONIZED_UNLOCK_RETRIES));
@@ -192,13 +194,15 @@ Synchronized::~Synchronized()
     }
 #endif
 
-    isLocked = false;
     if (result) {
+        ++errors;
         LOG_BEGIN(loggerModuleName, ERROR_LOG | 2);
         LOG("Synchronized mutex_destroy failed with (result)(ptr)");
         LOG(result);
         LOG((unsigned long)this);
         LOG_END;
+    } else {
+        // NO: ThreadSanitizer: prevent data race! CK isLocked = false;
     }
 }
 
diff --git a/threads_test.cpp b/threads_test.cpp
index 7394dcd..dedc147 100644
--- a/threads_test.cpp
+++ b/threads_test.cpp
@@ -618,37 +618,49 @@ BOOST_AUTO_TEST_CASE(SyncDeadlock_test)
     BOOST_TEST(sync.unlock());
 }
 
-#ifndef _WIN32
-void handler(int signum)
+BOOST_AUTO_TEST_CASE(SyncDeleteLocked_test)
 {
-    switch (signum) {
-    case SIGALRM:
-        signal(signum, SIG_DFL);
-        break;
-    default: // ignored
-        break;
+    try {
+        Synchronized sync;
+        BOOST_TEST(sync.lock());
+    } catch (std::exception& e) {
+        BOOST_TEST_MESSAGE(BOOST_CURRENT_FUNCTION);
+        BOOST_TEST_MESSAGE(e.what());
     }
 }
-#endif
 
-BOOST_AUTO_TEST_CASE(SyncDeleteLocked_test)
+boost::atomic<bool> stop { false };
+void lock_task(Synchronized* m)
 {
-#ifndef _WIN32
-    signal(SIGALRM, &handler);
-    ualarm(1000, 0); // us
-#endif
+    Lock l(*m);
+    stop = false;
+
+    while (!stop) {
+        Thread::sleep(123); // NOTE: do somet work ...
+        m->wait();
+    }
+
+    Thread::sleep(
+        BOOST_THREAD_TEST_TIME_MS); // do some cleanup task ... with lock!
+}
 
+BOOST_AUTO_TEST_CASE(SyncDeleteWaiting_test)
+{
     Stopwatch sw;
     try {
-
         auto sync = boost::make_shared<Synchronized>();
-        BOOST_TEST(sync->lock());
 
-#ifndef __WIN32
-        sync->wait(1234); // for signal with timout
-#endif
+        boost::thread t(lock_task, sync.get());
+        t.detach();
 
+        Thread::sleep(BOOST_THREAD_TEST_TIME_MS);
         BOOST_TEST_MESSAGE(BOOST_CURRENT_FUNCTION << sw.elapsed());
+        {
+            BOOST_TEST(sync->lock());
+            stop = true; // NOTE: without notify! CK
+            BOOST_TEST(sync->unlock());
+        }
+        sync.reset(); // NOTE: this delete the Synchronized obj! CK
     } catch (std::exception& e) {
         BOOST_TEST_MESSAGE(BOOST_CURRENT_FUNCTION);
         BOOST_TEST_MESSAGE(e.what());
@@ -784,6 +796,19 @@ BOOST_AUTO_TEST_CASE(ThreadLivetime_test)
     BOOST_TEST_MESSAGE(BOOST_CURRENT_FUNCTION << sw.elapsed());
 }
 
+#ifndef _WIN32
+void handler(int signum)
+{
+    switch (signum) {
+    case SIGALRM:
+        signal(signum, SIG_DFL);
+        break;
+    default: // ignored
+        break;
+    }
+}
+#endif
+
 BOOST_AUTO_TEST_CASE(ThreadNanoSleep_test)
 {
 #ifndef _WIN32