worker: fix hangup from two sequential wait() when a task is emplac…

…ed before the `start()` signal

remove unnecessary start-flag and avoid additional `wait()` in startup of worker

redGrapes/dispatch/thread/worker.cpp

@@ -32,7 +32,6 @@ WorkerThread::~WorkerThread()
 void WorkerThread::start()
 {
     thread = std::thread([this]{ this->run(); });
-    this->Worker::start();
 }
 
 Worker::Worker( memory::ChunkedBumpAlloc<memory::HwlocAlloc> & alloc, HwlocContext & hwloc_ctx, hwloc_obj_t const & obj, WorkerId worker_id )
@@ -46,12 +45,6 @@ Worker::~Worker()
 {
 }
 
-void Worker::start()
-{
-    m_start.store(true, std::memory_order_release);
-    wake();
-}
-
 void Worker::stop()
 {
     SPDLOG_TRACE("Worker::stop()");
@@ -83,12 +76,6 @@ void WorkerThread::run()
     };
                 */
 
-    /* wait for start-flag to be triggerd in order
-     * to avoid premature access to `shared_from_this`
-     */
-    while( ! m_start.load(std::memory_order_consume) )
-        cv.wait();
-
     /* initialize thread-local variables
      */
     SingletonContext::get().current_worker = this->shared_from_this();

redGrapes/dispatch/thread/worker.hpp

@@ -44,13 +44,6 @@ struct Worker
     //private:
     WorkerId id;
 
-    /*!
-     * if true, the thread shall start
-     * executing the jobs in its queue
-     * and request rescheduling if empty
-     */
-    std::atomic_bool m_start{ false };
-
     /*! if true, the thread shall stop
      * instead of waiting when it is out of jobs
      */
@@ -78,7 +71,6 @@ struct Worker
     inline scheduler::WakerId get_waker_id() { return id + 1; }
     inline bool wake() { return cv.notify(); }
 
-    void start();
     virtual void stop();
 
     /* adds a new task to the emplacement queue
@@ -127,13 +119,11 @@ struct WorkerThread
     WorkerThread( memory::ChunkedBumpAlloc<memory::HwlocAlloc> & alloc, HwlocContext & hwloc_ctx, hwloc_obj_t const & obj, WorkerId worker_id );
     ~WorkerThread();
 
-    void start();
-    void stop();
-
     /* function the thread will execute
      */
     void run();
-
+    void stop();
+
     void cpubind();
     void membind();
 };

redGrapes/dispatch/thread/worker_pool.cpp

@@ -58,12 +58,6 @@ WorkerPool::~WorkerPool()
 {
 }
 
-void WorkerPool::start()
-{
-    for( auto & worker : workers )
-        worker->start();
-}
-
 void WorkerPool::stop()
 {
     for( auto & worker : workers )

redGrapes/dispatch/thread/worker_pool.hpp

@@ -42,10 +42,6 @@ struct WorkerPool
         return workers.size();
     }
 
-    /* signals all workers to start executing tasks
-     */
-    void start();
-
     /* signals all workers that no new tasks will be added
      */
     void stop();

redGrapes/redGrapes.cpp

@@ -125,12 +125,10 @@ void Context::init( size_t n_workers, std::shared_ptr<scheduler::IScheduler> sch
 
     this->n_workers = n_workers;
     worker_pool = std::make_shared<dispatch::thread::WorkerPool>( hwloc_ctx, n_workers );
-    worker_pool->emplace_workers( n_workers );
-
     root_space = std::make_shared<TaskSpace>();
     this->scheduler = scheduler;
 
-    worker_pool->start();
+    worker_pool->emplace_workers( n_workers );
 }
 
 void Context::init( size_t n_workers )