task: get rid of the separate Barrier and BarrierLock

Make one class Barrier which is copiable, so we don't have to
have users making shared Barrier all the time.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>

include/crucible/task.h

@@ -99,36 +99,26 @@ namespace crucible {
 		static void cancel();
 	};
 
-	// Barrier executes waiting Tasks once the last BarrierLock
-	// is released.  Multiple unique Tasks may be scheduled while
-	// BarrierLocks exist and all will be run() at once upon
-	// release.  If no BarrierLocks exist, Tasks are executed
-	// immediately upon insertion.
-
 	class BarrierState;
 
-	class BarrierLock {
-		shared_ptr<BarrierState> m_barrier_state;
-		BarrierLock(shared_ptr<BarrierState> pbs);
-	friend class Barrier;
-	public:
-		// Release this Lock immediately and permanently
-		void release();
-	};
-
+	/// Barrier delays the execution of one or more Tasks.
+	/// The Tasks are executed when the last shared reference to the
+	/// BarrierState is released.  Copies of Barrier objects refer
+	/// to the same Barrier state.
 	class Barrier {
 		shared_ptr<BarrierState> m_barrier_state;
 
-		Barrier(shared_ptr<BarrierState> pbs);
 	public:
 		Barrier();
 
-		// Prevent execution of tasks behind barrier until
-		// BarrierLock destructor or release() method is called.
-		BarrierLock lock();
-
-		// Schedule a task for execution when no Locks exist
+		/// Schedule a task for execution when last Barrier is released.
 		void insert_task(Task t);
+
+		/// Release this reference to the barrier state.
+		/// Last released reference executes the task.
+		/// Barrier can only be released once, after which the
+		/// object can no longer be used.
+		void release();
 	};
 
 	// Exclusion provides exclusive access to a ExclusionLock.

lib/task.cc

@@ -788,16 +788,6 @@ namespace crucible {
 		void insert_task(Task t);
 	};
 
-	Barrier::Barrier(shared_ptr<BarrierState> pbs) :
-		m_barrier_state(pbs)
-	{
-	}
-
-	Barrier::Barrier() :
-		m_barrier_state(make_shared<BarrierState>())
-	{
-	}
-
 	void
 	BarrierState::release()
 	{
@@ -813,17 +803,6 @@ namespace crucible {
 		release();
 	}
 
-	BarrierLock::BarrierLock(shared_ptr<BarrierState> pbs) :
-		m_barrier_state(pbs)
-	{
-	}
-
-	void
-	BarrierLock::release()
-	{
-		m_barrier_state.reset();
-	}
-
 	void
 	BarrierState::insert_task(Task t)
 	{
@@ -831,16 +810,21 @@ namespace crucible {
 		m_tasks.insert(t);
 	}
 
+	Barrier::Barrier() :
+		m_barrier_state(make_shared<BarrierState>())
+	{
+	}
+
 	void
 	Barrier::insert_task(Task t)
 	{
 		m_barrier_state->insert_task(t);
 	}
 
-	BarrierLock
-	Barrier::lock()
+	void
+	Barrier::release()
 	{
-		return BarrierLock(m_barrier_state);
+		m_barrier_state.reset();
 	}
 
 	class ExclusionState {

test/task.cc

@@ -90,35 +90,33 @@ test_barrier(size_t count)
 
 	mutex mtx;
 	condition_variable cv;
+	bool done_flag = false;
 
 	unique_lock<mutex> lock(mtx);
 
-	auto b = make_shared<Barrier>();
+	Barrier b;
 
 	// Run several tasks in parallel
 	for (size_t c = 0; c < count; ++c) {
-		auto bl = b->lock();
 		ostringstream oss;
 		oss << "task #" << c;
+		auto b_hold = b;
 		Task t(
 			oss.str(),
-			[c, &task_done, &mtx, bl]() mutable {
-				// cerr << "Task #" << c << endl;
+			[c, &task_done, &mtx, b_hold]() mutable {
+				// ostringstream oss;
+				// oss << "Task #" << c << endl;
 				unique_lock<mutex> lock(mtx);
+				// cerr << oss.str();
 				task_done.at(c) = true;
-				bl.release();
+				b_hold.release();
 			}
 		);
 		t.run();
 	}
 
-	// Get current status
-	ostringstream oss;
-	TaskMaster::print_queue(oss);
-	TaskMaster::print_workers(oss);
-
-	bool done_flag = false;
-
+	// Need completed to go out of local scope so it will release b
+	{
 		Task completed(
 			"Waiting for Barrier",
 			[&mtx, &cv, &done_flag]() {
@@ -128,9 +126,15 @@ test_barrier(size_t count)
 				cv.notify_all();
 			}
 		);
-	b->insert_task(completed);
+		b.insert_task(completed);
+	}
 
-	b.reset();
+	// Get current status
+	// TaskMaster::print_queue(cerr);
+	// TaskMaster::print_workers(cerr);
+
+	// Release our b
+	b.release();
 
 	while (true) {
 		size_t tasks_done = 0;
@@ -139,7 +143,7 @@ test_barrier(size_t count)
 				++tasks_done;
 			}
 		}
-		// cerr << "Tasks done: " << tasks_done << " done_flag " << done_flag << endl;
+		cerr << "Tasks done: " << tasks_done << " done_flag " << done_flag << endl;
 		if (tasks_done == count && done_flag) {
 			break;
 		}