diff --git a/README.txt b/README.txt
index f574095..061eee0 100644
--- a/README.txt
+++ b/README.txt
@@ -265,3 +265,22 @@ Use 2 threads to load up 4 different nodes.
     echo httprl_pr($nodes);
     ?>
 
+
+Run a function in the background. Notice that there is no return or printed key
+in the callback options.
+
+    <?php
+    // Setup callback options array; call watchdog in the background.
+    $callback_options = array(
+      array(
+        'function' => 'watchdog',
+      ),
+      'httprl-test', 'background watchdog call done', array(), WATCHDOG_DEBUG,
+    );
+    // Queue up the request.
+    httprl_queue_background_callback($callback_options);
+
+    // Execute request.
+    httprl_send_request();
+    ?>
+
diff --git a/httprl.async.inc b/httprl.async.inc
index 1a1a991..bcf3493 100644
--- a/httprl.async.inc
+++ b/httprl.async.inc
@@ -14,16 +14,25 @@ function httprl_async_page() {
   //  The temp_key is not set.
   //  The temp_key does not start with httprl_.
   //  The master_key does not match the md5 of drupal_get_private_key().
-  //  The temp_key does not match a lock that has been taken.
   if (   empty($_POST['master_key'])
       || empty($_POST['temp_key'])
       || strpos($_POST['temp_key'], 'httprl_') !== 0
       || $_POST['master_key'] != hash('sha512', drupal_get_private_key())
-      || lock_may_be_available($_POST['temp_key'])
         ) {
     httprl_fast403();
   }
 
+  // Exit if the temp_key does not match a lock that has been taken.
+  // Wait up to 5 seconds for the lock to propagate out.
+  $tries = 0;
+  while (lock_may_be_available($_POST['temp_key'])) {
+    $tries++;
+    if ($tries > 5) {
+      httprl_fast403();
+    }
+    sleep(1);
+  }
+
   // If request was a non blocking one, cut the connection right here.
   if (empty($_POST['mode'])) {
     httprl_background_processing('httprl async function callback running', FALSE);
diff --git a/httprl.module b/httprl.module
index 29c4649..b962eff 100644
--- a/httprl.module
+++ b/httprl.module
@@ -1183,8 +1183,18 @@ function httprl_queue_background_callback(&$args, &$result = NULL) {
   }
 
   // Acquire lock for this run.
-  $id = 'httprl_' . hash('sha512', mt_rand() . time());
-  lock_acquire($id);
+  $locked = FALSE;
+  $counter = 0;
+  while (!$locked && $counter < 20) {
+    $id = 'httprl_' . hash('sha512', mt_rand() . time());
+    $locked = lock_acquire($id);
+  }
+
+  // Make sure lock exists after this process is dead.
+  if (empty($mode)) {
+    global $locks;
+    unset($locks[$id]);
+  }
 
   // Get URL to call function in background.
   if (empty($callback_options['url'])) {
@@ -1200,7 +1210,6 @@ function httprl_queue_background_callback(&$args, &$result = NULL) {
       'temp_key' => $id,
       'mode' => $mode,
       'function' => $callback_options['function'],
-      'parent' => FALSE,
       'args' => serialize($args),
     ),
     'internal_states' => array(