diff --git a/examples/fork.php b/examples/fork.php
index 9d6bc2c..d8da4fe 100644
--- a/examples/fork.php
+++ b/examples/fork.php
@@ -1,41 +1,71 @@
 <?php
 require dirname(__DIR__).'/vendor/autoload.php';
 
-use Icicle\Loop;
 use Icicle\Concurrent\Forking\ForkContext;
+use Icicle\Coroutine\Coroutine;
+use Icicle\Loop;
 
 class Test extends ForkContext
 {
+    /**
+     * @synchronized
+     */
+    public $data;
+
     public function run()
     {
         print "Child sleeping for 5 seconds...\n";
-        sleep(3);
+        yield $this->sem->acquire();
+        sleep(4);
+        yield $this->sem->release();
 
         $this->synchronized(function () {
             $this->data = 'progress';
         });
 
+        //throw new Exception('Testing exception bubbling.');
+
         sleep(2);
     }
 }
 
-$context = new Test();
-$context->data = 'blank';
-$context->start();
+$generator = function () {
+    $before = memory_get_usage();
+    $context = new Test();
+    $after = memory_get_usage();
+    $context->data = 'blank';
+    printf("Object memory: %d bytes\n", $after - $before);
+    $context->start();
 
-$timer = Loop\periodic(1, function () use ($context) {
-    static $i;
-    $i = $i + 1 ?: 1;
-    print "Demonstrating how alive the parent is for the {$i}th time.\n";
-
-    $context->synchronized(function ($context) {
-        printf("Context data: '%s'\n", $context->data);
+    Loop\timer(1, function () use ($context) {
+        $context->sem->acquire()->then(function () use ($context) {
+            print "Finally got semaphore from child!\n";
+            return $context->sem->release();
+        });
     });
-});
 
-$context->join()->then(function () use ($timer) {
-    print "Context done!\n";
-    $timer->stop();
-});
+    $timer = Loop\periodic(1, function () use ($context) {
+        static $i;
+        $i = $i + 1 ?: 1;
+        print "Demonstrating how alive the parent is for the {$i}th time.\n";
 
+        if ($context->isRunning()) {
+            $context->synchronized(function ($context) {
+                printf("Context data: '%s'\n", $context->data);
+            });
+        }
+    });
+
+    try {
+        yield $context->join();
+        print "Context done!\n";
+    } catch (Exception $e) {
+        print "Error from child!\n";
+        print $e."\n";
+    } finally {
+        $timer->stop();
+    }
+};
+
+new Coroutine($generator());
 Loop\run();
diff --git a/src/AsyncSemaphore.php b/src/AsyncSemaphore.php
index 3912bd5..16cbde8 100644
--- a/src/AsyncSemaphore.php
+++ b/src/AsyncSemaphore.php
@@ -3,6 +3,7 @@ namespace Icicle\Concurrent;
 
 use Icicle\Concurrent\Exception\InvalidArgumentError;
 use Icicle\Concurrent\Forking\Synchronized;
+use Icicle\Loop;
 use Icicle\Promise;
 
 /**
@@ -59,6 +60,10 @@ class AsyncSemaphore extends Synchronized
         $this->queueSize = 0;
         $this->locks = $maxLocks;
         $this->processQueue = new \SplQueue();
+
+        Loop\signal(SIGUSR1, function () {
+            $this->handlePendingLocks();
+        });
     }
 
     /**
@@ -77,7 +82,6 @@ class AsyncSemaphore extends Synchronized
         // Alright, we gotta get in and out as fast as possible. Deep breath...
         return $this->synchronized(function () {
             if ($this->locks > 0) {
-                printf("Async lock count: %d--\n", $this->locks);
                 // Oh goody, a free lock! Acquire a lock and get outta here!
                 --$this->locks;
                 return Promise\resolve();
@@ -102,10 +106,9 @@ class AsyncSemaphore extends Synchronized
     {
         $this->synchronized(function () {
             if ($this->locks === $this->maxLocks) {
-                throw new \Exception();
+                throw new SemaphoreException('No locks acquired to release.');
             }
 
-            printf("Async lock count: %d++\n", $this->locks);
             ++$this->locks;
         });
 
@@ -122,13 +125,16 @@ class AsyncSemaphore extends Synchronized
         return Promise\resolve();
     }
 
-    public function update()
+    /**
+     * Handles pending lock requests and resolves a pending acquire() call if
+     * new locks are available.
+     */
+    private function handlePendingLocks()
     {
         $dequeue = false;
 
         $this->synchronized(function () use (&$dequeue) {
             if ($this->locks > 0 && !$this->waitQueue->isEmpty()) {
-                printf("Async lock count: %d--\n", $this->locks);
                 --$this->locks;
                 $dequeue = true;
             }
diff --git a/src/Forking/ForkContext.php b/src/Forking/ForkContext.php
index ae0a047..8c9b3f9 100644
--- a/src/Forking/ForkContext.php
+++ b/src/Forking/ForkContext.php
@@ -1,8 +1,10 @@
 <?php
 namespace Icicle\Concurrent\Forking;
 
+use Icicle\Concurrent\AsyncSemaphore;
 use Icicle\Concurrent\ContextInterface;
 use Icicle\Concurrent\Exception\ContextAbortException;
+use Icicle\Coroutine\Coroutine;
 use Icicle\Loop;
 use Icicle\Promise\Deferred;
 use Icicle\Socket\Stream\DuplexStream;
@@ -33,7 +35,7 @@ abstract class ForkContext extends Synchronized implements ContextInterface
             $this->stop();
         });
 
-        $this->sem = new AsyncIpcSemaphore();
+        $this->sem = new AsyncSemaphore();
     }
 
     /**
@@ -80,10 +82,6 @@ abstract class ForkContext extends Synchronized implements ContextInterface
             $this->pid = $pid;
             fclose($this->childSocket);
 
-            Loop\signal(SIGUSR1, function () {
-                $this->sem->update();
-            });
-
             // Wait for the child process to send us a byte over the socket pair
             // to discover immediately when the process has completed.
             $this->parentSocket->read(1)->then(function ($data) {
@@ -120,18 +118,17 @@ abstract class ForkContext extends Synchronized implements ContextInterface
         // child context by default is synchronous and uses the parent event
         // loop, so we need to stop the clone before doing any work in case it
         // is already running.
+        Loop\stop();
         Loop\reInit();
         Loop\clear();
-        Loop\stop();
-
-        pcntl_signal(SIGUSR1, function () {
-            $this->sem->update();
-        });
 
         // Execute the context runnable and send the parent context the result.
         try {
-            $this->run();
-            pcntl_signal_dispatch();
+            $generator = $this->run();
+            if ($generator instanceof \Generator) {
+                $coroutine = new Coroutine($generator);
+            }
+            Loop\run();
             fwrite($this->childSocket, chr(self::MSG_DONE));
         } catch (\Exception $exception) {
             fwrite($this->childSocket, chr(self::MSG_ERROR));