diff --git a/scheduler.py b/scheduler.py
index ffb23da..6659ae8 100644
--- a/scheduler.py
+++ b/scheduler.py
@@ -16,10 +16,11 @@ def transition(what, fromList, toList, key="unknow"):
   try:
     print("DEBUG:%s: transition %s" % (key, what))
     fromList.remove(what)
+    toList.append(what)
   except ValueError as e:
     print (what + " not in source list")
-    raise e
-  toList.append(what)
+    return False
+  return True
 
 class Scheduler(object):
   # A simple job scheduler.
@@ -147,12 +148,18 @@ def __doRescheduleParallel(self):
     parallelJobs = [j for j in self.pendingJobs if self.jobs[j]["scheduler"] == "parallel"]
     # First of all clean up the pending parallel jobs from all those
     # which have broken dependencies.
-    for taskId in parallelJobs:
-      brokenDeps = [dep for dep in self.jobs[taskId]["deps"] if dep in self.brokenJobs]
-      if not brokenDeps:
-        continue
-      transition(taskId, self.pendingJobs, self.brokenJobs, "parallel:pending->broken")
-      self.errors[taskId] = "The following dependencies could not complete:\n%s" % "\n".join(brokenDeps)
+    while True:
+      has_broken = False
+      for taskId in parallelJobs[:]:
+        brokenDeps = [dep for dep in self.jobs[taskId]["deps"] if dep in self.brokenJobs]
+        if not brokenDeps:
+          continue
+        has_broken = True
+        parallelJobs.remove(taskId)
+        transition(taskId, self.pendingJobs, self.brokenJobs, "parallel:pending->broken")
+        self.errors[taskId] = "The following dependencies could not complete:\n%s" % "\n".join(brokenDeps)
+      if not has_broken:
+        break
 
     # If no tasks left, quit. Notice we need to check also for serial jobs
     # since they might queue more parallel payloads.
@@ -175,7 +182,8 @@ def __doRescheduleParallel(self):
         if dumpMsg:
           self.log("Pending tasks: %s: %s" % (taskId, pendingDeps),30)
         continue
-      allJobs.append({"id": taskId, "priorty": self.jobs[taskId]["priorty"]})
+      if taskId in self.pendingJobs:
+        allJobs.append({"id": taskId, "priorty": self.jobs[taskId]["priorty"]})
     buildJobs =[]
     downloadJobs = []
     forceJobs = []
@@ -199,10 +207,12 @@ def __doRescheduleParallel(self):
       else:
         buildJobs = buildJobs[:bldCount]
     for taskId in forceJobs + downloadJobs + buildJobs:
-      taskType = taskId.split("-")[0]
-      self.runningJobsCount[taskType] += 1
-      transition(taskId, self.pendingJobs, self.runningJobs, "parallel:pending->running")
-      self.__scheduleParallel(taskId, self.jobs[taskId]["spec"], priorty=self.jobs[taskId]["priorty"])
+      if transition(taskId, self.pendingJobs, self.runningJobs, "parallel:pending->running"):
+        taskType = taskId.split("-")[0]
+        self.runningJobsCount[taskType] += 1
+        self.__scheduleParallel(taskId, self.jobs[taskId]["spec"], priorty=self.jobs[taskId]["priorty"])
+      elif self.resourceManager:
+        self.resourceManager.releaseResourcesForExternal(taskId)
 
   # Update the job with the result of running.
   def __updateJobStatus(self, taskId, error):