launch_daemon: Maintain pending jobs for requirements.

* If a requirement cannot be launched, a job is now added to the
  requirement as pending job.
* If the requirement enters the launch queue at a later time, the
  pending job will be put there, too.

src/servers/launch/Job.cpp

@@ -207,6 +207,27 @@ Job::AddRequirement(const char* requirement)
 }
 
 
+const BStringList&
+Job::Pending() const
+{
+	return fPendingJobs;
+}
+
+
+BStringList&
+Job::Pending()
+{
+	return fPendingJobs;
+}
+
+
+void
+Job::AddPending(const char* pending)
+{
+	fPendingJobs.Add(pending);
+}
+
+
 bool
 Job::CheckCondition(ConditionContext& context) const
 {

src/servers/launch/Job.h

@@ -70,6 +70,10 @@ public:
 			BStringList&		Requirements();
 			void				AddRequirement(const char* requirement);
 
+			const BStringList&	Pending() const;
+			BStringList&		Pending();
+			void				AddPending(const char* pending);
+
 	virtual	bool				CheckCondition(ConditionContext& context) const;
 
 			status_t			Init(const Finder& jobs,
@@ -137,6 +141,7 @@ private:
 			mutex				fLaunchStatusLock;
 			::Target*			fTarget;
 			::Condition*		fCondition;
+			BStringList			fPendingJobs;
 			BObjectList<BMessage>
 								fPendingLaunchDataReplies;
 			::TeamRegistrator*	fTeamRegistrator;

src/servers/launch/LaunchDaemon.cpp

@@ -1463,6 +1463,7 @@ LaunchDaemon::_CanLaunchJobRequirements(Job* job, uint32 options)
 			&& !requirement->IsRunning() && !requirement->IsLaunching()
 			&& (!_CanLaunchJob(requirement, options, true)
 				|| _CanLaunchJobRequirements(requirement, options))) {
+			requirement->AddPending(job->Name());
 			return false;
 		}
 	}
@@ -1521,6 +1522,18 @@ LaunchDaemon::_LaunchJob(Job* job, uint32 options)
 		return false;
 	}
 
+	// Try to launch pending jobs as well
+	count = job->Pending().CountStrings();
+	for (int32 index = 0; index < count; index++) {
+		Job* pending = FindJob(job->Pending().StringAt(index));
+		if (pending != NULL && _LaunchJob(pending, 0)) {
+			// Remove the job from the pending list once its in the launch
+			// queue, so that is not being launched again next time.
+			index--;
+			count--;
+		}
+	}
+
 	return true;
 }