diff --git a/dataflow_cpp/CMakeLists.txt b/dataflow_cpp/CMakeLists.txt
index 0ad76a0..133d066 100644
--- a/dataflow_cpp/CMakeLists.txt
+++ b/dataflow_cpp/CMakeLists.txt
@@ -26,7 +26,7 @@ target_link_libraries(embb_dataflow_cpp embb_mtapi_cpp embb_base_cpp embb_mtapi_
 if (BUILD_TESTS STREQUAL ON)
   include_directories(${CMAKE_CURRENT_BINARY_DIR}/../partest/include)
   add_executable (embb_dataflow_cpp_test ${EMBB_DATAFLOW_CPP_TEST_SOURCES})
-  target_link_libraries(embb_dataflow_cpp_test embb_mtapi_cpp embb_mtapi_c partest
+  target_link_libraries(embb_dataflow_cpp_test embb_dataflow_cpp embb_mtapi_cpp embb_mtapi_c partest
                         embb_base_cpp embb_base_c ${compiler_libs})
   CopyBin(BIN embb_dataflow_cpp_test DEST ${local_install_dir})
 endif()
diff --git a/dataflow_cpp/include/embb/dataflow/internal/inputs.h b/dataflow_cpp/include/embb/dataflow/internal/inputs.h
index afcb011..4f4430a 100644
--- a/dataflow_cpp/include/embb/dataflow/internal/inputs.h
+++ b/dataflow_cpp/include/embb/dataflow/internal/inputs.h
@@ -27,6 +27,7 @@
 #ifndef EMBB_DATAFLOW_INTERNAL_INPUTS_H_
 #define EMBB_DATAFLOW_INTERNAL_INPUTS_H_
 
+#include <embb/base/atomic.h>
 #include <embb/dataflow/internal/tuple.h>
 #include <embb/dataflow/internal/in.h>
 
diff --git a/dataflow_cpp/include/embb/dataflow/internal/node.h b/dataflow_cpp/include/embb/dataflow/internal/node.h
index daf80b3..122750e 100644
--- a/dataflow_cpp/include/embb/dataflow/internal/node.h
+++ b/dataflow_cpp/include/embb/dataflow/internal/node.h
@@ -28,7 +28,7 @@
 #define EMBB_DATAFLOW_INTERNAL_NODE_H_
 
 #include <cstddef>
-
+#include <embb/base/exceptions.h>
 #include <embb/dataflow/internal/scheduler.h>
 
 namespace embb {
@@ -50,6 +50,9 @@ class Node {
 
  protected:
   Scheduler * sched_;
+  static int next_process_id_;
+
+  static int GetNextProcessID() { return next_process_id_++; }
 };
 
 } // namespace internal
diff --git a/dataflow_cpp/include/embb/dataflow/internal/process.h b/dataflow_cpp/include/embb/dataflow/internal/process.h
index 1765db0..caa81db 100644
--- a/dataflow_cpp/include/embb/dataflow/internal/process.h
+++ b/dataflow_cpp/include/embb/dataflow/internal/process.h
@@ -56,6 +56,13 @@ class Process< Slices, Serial, Inputs<Slices, I1, I2, I3, I4, I5>,
   explicit Process(FunctionType function)
     : executor_(function) {
     next_clock_ = 0;
+    queued_clock_ = 0;
+    bool ordered = Serial;
+    if (ordered) {
+      queue_id_ = GetNextProcessID();
+    } else {
+      queue_id_ = 0;
+    }
     inputs_.SetListener(this);
   }
 
@@ -95,21 +102,39 @@ class Process< Slices, Serial, Inputs<Slices, I1, I2, I3, I4, I5>,
   }
 
   virtual void OnClock(int clock) {
-    if (!inputs_.AreAtClock(clock))
+    if (!inputs_.AreAtClock(clock)) {
       EMBB_THROW(embb::base::ErrorException,
         "Some inputs are not at expected clock.")
+    }
 
     bool ordered = Serial;
     if (ordered) {
-      lock_.Lock();
-      for (int ii = next_clock_; ii < next_clock_ + Slices; ii++) {
-        if (!inputs_.AreAtClock(ii)) {
-          break;
+      bool retry = true;
+      while (retry) {
+        int clk = next_clock_;
+        int clk_end = clk + Slices;
+        int clk_res = clk;
+        for (int ii = clk; ii < clk_end; ii++) {
+          if (!inputs_.AreAtClock(ii)) {
+            break;
+          }
+          clk_res++;
+        }
+        if (clk_res > clk) {
+          if (next_clock_.CompareAndSwap(clk, clk_res)) {
+            while (queued_clock_.Load() < clk);
+            for (int ii = clk; ii < clk_res; ii++) {
+              const int idx = ii % Slices;
+              action_[idx] = Action(this, ii);
+              sched_->Enqueue(queue_id_, action_[idx]);
+            }
+            queued_clock_.Store(clk_res);
+            retry = false;
+          }
+        } else {
+          retry = false;
         }
-        next_clock_ = ii + 1;
-        Run(ii);
       }
-      lock_.Unlock();
     } else {
       const int idx = clock % Slices;
       action_[idx] = Action(this, clock);
@@ -121,9 +146,10 @@ class Process< Slices, Serial, Inputs<Slices, I1, I2, I3, I4, I5>,
   InputsType inputs_;
   OutputsType outputs_;
   ExecutorType executor_;
-  int next_clock_;
   Action action_[Slices];
-  SpinLock lock_;
+  embb::base::Atomic<int> next_clock_;
+  embb::base::Atomic<int> queued_clock_;
+  int queue_id_;
 };
 
 } // namespace internal
diff --git a/dataflow_cpp/include/embb/dataflow/internal/scheduler.h b/dataflow_cpp/include/embb/dataflow/internal/scheduler.h
index 811c7dd..5770217 100644
--- a/dataflow_cpp/include/embb/dataflow/internal/scheduler.h
+++ b/dataflow_cpp/include/embb/dataflow/internal/scheduler.h
@@ -38,6 +38,7 @@ class Scheduler {
   Scheduler() {}
   virtual ~Scheduler() {}
   virtual void Spawn(Action & action) = 0;
+  virtual void Enqueue(int process_id, Action & action) = 0;
   virtual void WaitForSlice(int slice) = 0;
 };
 
diff --git a/dataflow_cpp/include/embb/dataflow/internal/scheduler_mtapi.h b/dataflow_cpp/include/embb/dataflow/internal/scheduler_mtapi.h
index 7e72812..692b4b8 100644
--- a/dataflow_cpp/include/embb/dataflow/internal/scheduler_mtapi.h
+++ b/dataflow_cpp/include/embb/dataflow/internal/scheduler_mtapi.h
@@ -45,6 +45,16 @@ class SchedulerMTAPI : public Scheduler {
       embb::mtapi::Group & group = node.CreateGroup();
       group_[ii] = &group;
     }
+
+    queue_count_ = static_cast<int>(node.GetWorkerThreadCount());
+    queue_ = reinterpret_cast<embb::mtapi::Queue**>(
+      embb::base::Allocation::Allocate(
+        sizeof(embb::mtapi::Queue*)*queue_count_));
+
+    for (int ii = 0; ii < queue_count_; ii++) {
+      embb::mtapi::Queue & queue = node.CreateQueue(0, true);
+      queue_[ii] = &queue;
+    }
   }
   virtual ~SchedulerMTAPI() {
     embb::mtapi::Node & node = embb::mtapi::Node::GetInstance();
@@ -52,17 +62,29 @@ class SchedulerMTAPI : public Scheduler {
       group_[ii]->WaitAll(MTAPI_INFINITE);
       node.DestroyGroup(*group_[ii]);
     }
+    for (int ii = 0; ii < queue_count_; ii++) {
+      node.DestroyQueue(*queue_[ii]);
+    }
+    embb::base::Allocation::Free(queue_);
   }
   virtual void Spawn(Action & action) {
     const int idx = action.GetClock() % Slices;
     group_[idx]->Spawn(embb::base::MakeFunction(action, &Action::RunMTAPI));
   }
+  virtual void Enqueue(int process_id, Action & action) {
+    const int idx = action.GetClock() % Slices;
+    const int queue_id = process_id % queue_count_;
+    queue_[queue_id]->Spawn(group_[idx],
+      embb::base::MakeFunction(action, &Action::RunMTAPI));
+  }
   virtual void WaitForSlice(int slice) {
     group_[slice]->WaitAll(MTAPI_INFINITE);
   }
 
  private:
   embb::mtapi::Group * group_[Slices];
+  embb::mtapi::Queue ** queue_;
+  int queue_count_;
 };
 
 } // namespace internal
diff --git a/dataflow_cpp/include/embb/dataflow/internal/scheduler_sequential.h b/dataflow_cpp/include/embb/dataflow/internal/scheduler_sequential.h
index a553548..919a3a3 100644
--- a/dataflow_cpp/include/embb/dataflow/internal/scheduler_sequential.h
+++ b/dataflow_cpp/include/embb/dataflow/internal/scheduler_sequential.h
@@ -41,6 +41,9 @@ class SchedulerSequential : public Scheduler {
   virtual void Spawn(Action & action) {
     action.RunSequential();
   }
+  virtual void Enqueue(int, Action & action) {
+    action.RunSequential();
+  }
   virtual void WaitForSlice(int /*slice*/) {}
 };
 
diff --git a/dataflow_cpp/include/embb/dataflow/internal/signal.h b/dataflow_cpp/include/embb/dataflow/internal/signal.h
index 951e75a..dde39cc 100644
--- a/dataflow_cpp/include/embb/dataflow/internal/signal.h
+++ b/dataflow_cpp/include/embb/dataflow/internal/signal.h
@@ -27,7 +27,7 @@
 #ifndef EMBB_DATAFLOW_INTERNAL_SIGNAL_H_
 #define EMBB_DATAFLOW_INTERNAL_SIGNAL_H_
 
-#include <embb/dataflow/internal/spinlock.h>
+#include <embb/base/c/atomic.h>
 
 namespace embb {
 namespace dataflow {
@@ -42,27 +42,23 @@ class Signal {
   Signal(Signal const & other)
     : blank_(other.blank_), value_(other.value_), clock_(other.clock_) {}
   void operator = (Signal const & rhs) {
-    lock_.Lock();
     blank_ = rhs.blank_;
     value_ = rhs.value_;
     clock_ = rhs.clock_;
-    lock_.Unlock();
+    embb_atomic_memory_barrier();
   }
   int GetClock() const { return clock_; }
   bool IsBlank() const { return blank_; }
   Type const & GetValue() const { return value_; }
   void Clear() {
-    lock_.Lock();
     blank_ = true;
     clock_ = -1;
-    lock_.Unlock();
   }
 
  private:
   bool blank_;
   Type value_;
   int clock_;
-  SpinLock lock_;
 };
 
 } // namespace internal
diff --git a/dataflow_cpp/include/embb/dataflow/internal/sink.h b/dataflow_cpp/include/embb/dataflow/internal/sink.h
index 7066995..0487834 100644
--- a/dataflow_cpp/include/embb/dataflow/internal/sink.h
+++ b/dataflow_cpp/include/embb/dataflow/internal/sink.h
@@ -52,6 +52,8 @@ class Sink< Slices, Inputs<Slices, I1, I2, I3, I4, I5> >
   explicit Sink(FunctionType function)
     : executor_(function) {
     next_clock_ = 0;
+    queued_clock_ = 0;
+    queue_id_ = GetNextProcessID();
     inputs_.SetListener(this);
   }
 
@@ -80,32 +82,47 @@ class Sink< Slices, Inputs<Slices, I1, I2, I3, I4, I5> >
   }
 
   virtual void OnClock(int clock) {
-    TrySpawn(clock);
+    if (!inputs_.AreAtClock(clock)) {
+      EMBB_THROW(embb::base::ErrorException,
+        "Some inputs are not at expected clock.")
+    }
+
+    bool retry = true;
+    while (retry) {
+      int clk = next_clock_;
+      int clk_end = clk + Slices;
+      int clk_res = clk;
+      for (int ii = clk; ii < clk_end; ii++) {
+        if (!inputs_.AreAtClock(ii)) {
+          break;
+        }
+        clk_res++;
+      }
+      if (clk_res > clk) {
+        if (next_clock_.CompareAndSwap(clk, clk_res)) {
+          while (queued_clock_.Load() < clk);
+          for (int ii = clk; ii < clk_res; ii++) {
+            const int idx = ii % Slices;
+            action_[idx] = Action(this, ii);
+            sched_->Enqueue(queue_id_, action_[idx]);
+          }
+          queued_clock_.Store(clk_res);
+          retry = false;
+        }
+      } else {
+        retry = false;
+      }
+    }
   }
 
  private:
   InputsType inputs_;
   ExecutorType executor_;
-  int next_clock_;
   Action action_[Slices];
   ClockListener * listener_;
-  SpinLock lock_;
-
-  void TrySpawn(int clock) {
-    if (!inputs_.AreAtClock(clock))
-      EMBB_THROW(embb::base::ErrorException,
-        "Some inputs are not at expected clock.")
-
-    lock_.Lock();
-    for (int ii = next_clock_; ii < next_clock_ + Slices; ii++) {
-      if (!inputs_.AreAtClock(ii)) {
-        break;
-      }
-      next_clock_ = ii + 1;
-      Run(ii);
-    }
-    lock_.Unlock();
-  }
+  embb::base::Atomic<int> next_clock_;
+  embb::base::Atomic<int> queued_clock_;
+  int queue_id_;
 };
 
 } // namespace internal
diff --git a/dataflow_cpp/include/embb/dataflow/internal/source.h b/dataflow_cpp/include/embb/dataflow/internal/source.h
index 48f5772..232a50e 100644
--- a/dataflow_cpp/include/embb/dataflow/internal/source.h
+++ b/dataflow_cpp/include/embb/dataflow/internal/source.h
@@ -27,13 +27,9 @@
 #ifndef EMBB_DATAFLOW_INTERNAL_SOURCE_H_
 #define EMBB_DATAFLOW_INTERNAL_SOURCE_H_
 
-#include <embb/base/atomic.h>
-#include <embb/base/thread.h>
-
 #include <embb/dataflow/internal/node.h>
 #include <embb/dataflow/internal/outputs.h>
 #include <embb/dataflow/internal/source_executor.h>
-#include <embb/dataflow/internal/action.h>
 
 namespace embb {
 namespace dataflow {
@@ -53,7 +49,6 @@ class Source< Slices, Outputs<Slices, O1, O2, O3, O4, O5> >
 
   explicit Source(FunctionType function)
     : executor_(function), not_done_(true) {
-    next_clock_ = 0;
   }
 
   virtual bool HasOutputs() const {
@@ -62,7 +57,6 @@ class Source< Slices, Outputs<Slices, O1, O2, O3, O4, O5> >
 
   virtual void Run(int clock) {
     not_done_ = executor_.Execute(clock, outputs_);
-    next_clock_++;
   }
 
   virtual bool Start(int clock) {
@@ -89,9 +83,7 @@ class Source< Slices, Outputs<Slices, O1, O2, O3, O4, O5> >
  private:
   OutputsType outputs_;
   ExecutorType executor_;
-  Action action_[Slices];
   volatile bool not_done_;
-  embb::base::Atomic<int> next_clock_;
 };
 
 } // namespace internal
diff --git a/dataflow_cpp/src/dummy.cc b/dataflow_cpp/src/node.cc
similarity index 96%
rename from dataflow_cpp/src/dummy.cc
rename to dataflow_cpp/src/node.cc
index e95756a..55b91c7 100644
--- a/dataflow_cpp/src/dummy.cc
+++ b/dataflow_cpp/src/node.cc
@@ -24,3 +24,6 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include <embb/dataflow/internal/node.h>
+
+int embb::dataflow::internal::Node::next_process_id_ = 0;
diff --git a/dataflow_cpp/test/dataflow_cpp_test_simple.cc b/dataflow_cpp/test/dataflow_cpp_test_simple.cc
index 3fe9272..52d1212 100644
--- a/dataflow_cpp/test/dataflow_cpp_test_simple.cc
+++ b/dataflow_cpp/test/dataflow_cpp_test_simple.cc
@@ -60,7 +60,7 @@ bool sourceFunc(int & out) {
   source_array[source_counter] = out;
   source_counter++;
 
-  return source_counter < 12;
+  return source_counter < TEST_COUNT;
 }
 
 embb::base::Atomic<int> pred_counter;