initial ideas for improving the scheduler API (far from finished)

2 files changed, 563 insertions, 11 deletions

diff --git a/src/include/gnunet_scheduler_lib.h b/src/include/gnunet_scheduler_lib.h
index 2be1858ce..a7385e31c 100644
--- a/src/include/gnunet_scheduler_lib.h
+++ b/src/include/gnunet_scheduler_lib.h
@@ -97,6 +97,84 @@ enum GNUNET_SCHEDULER_Reason
 
 
 /**
+ * Possible events on FDs, used as a bitmask.
+ * Modelled after GPollFD.
+ */
+enum GNUNET_SCHEDULER_EventType
+{
+
+  /**
+   * No event (useful for timeout).
+   */
+  GNUNET_SCHEDULER_ET_NONE = 0,
+
+  /**
+   * Data available for reading.
+   */
+  GNUNET_SCHEDULER_ET_IN = 1,
+
+  /**
+   * Buffer available for writing.
+   */
+  GNUNET_SCHEDULER_ET_OUT = 2,
+
+  /**
+   *
+   */
+  GNUNET_SCHEDULER_ET_HUP = 4,
+
+  /**
+   *
+   */
+  GNUNET_SCHEDULER_ET_ERR = 8,
+
+  /**
+   *
+   */
+  GNUNET_SCHEDULER_ET_PRI = 16,
+
+  /**
+   *
+   */
+  GNUNET_SCHEDULER_ET_NVAL = 32
+
+};
+
+
+/**
+ * Information about an event relating to a file descriptor/socket.
+ */
+struct GNUNET_SCHEDULER_FdInfo
+{
+
+  /**
+   * GNUnet network socket the event is about, matches @a sock,
+   * NULL if this is about a file handle or if no network
+   * handle was given to the scheduler originally.
+   */
+  struct GNUNET_NETWORK_Handle *fd;
+
+  /**
+   * GNUnet file handle the event is about, matches @a sock,
+   * NULL if this is about a network socket or if no network
+   * handle was given to the scheduler originally.
+   */ 
+  struct GNUNET_DISK_FileHandle *fh;
+
+  /**
+   * Type of the event that was generated related to @e sock.
+   */
+  enum GNUNET_SCHEDULER_EventType et;
+
+  /**
+   * Underlying OS handle the event was about.
+   */
+  int sock;
+
+};
+
+
+/**
  * Context information passed to each scheduler task.
  */
 struct GNUNET_SCHEDULER_TaskContext
@@ -107,16 +185,29 @@ struct GNUNET_SCHEDULER_TaskContext
   enum GNUNET_SCHEDULER_Reason reason;
 
   /**
-   * Set of file descriptors ready for reading;
-   * note that additional bits may be set
-   * that were not in the original request
+   * Length of the following array.
+   */ 
+  unsigned int fds_len;
+
+  /**
+   * Array of length @e fds_len with information about ready FDs.
+   * Note that we use the same format regardless of the internal
+   * event loop that was used.  The given array should only contain
+   * information about file descriptors relevant to the current task.
+   */
+  const struct GNUNET_SCHEDULER_FdInfo *fds;  
+
+  /**
+   * Set of file descriptors ready for reading; note that additional
+   * bits may be set that were not in the original request.
+   * @deprecated
    */
   const struct GNUNET_NETWORK_FDSet *read_ready;
 
   /**
-   * Set of file descriptors ready for writing;
-   * note that additional bits may be set
-   * that were not in the original request.
+   * Set of file descriptors ready for writing; note that additional
+   * bits may be set that were not in the original request.
+   * @deprecated
    */
   const struct GNUNET_NETWORK_FDSet *write_ready;
 
@@ -124,16 +215,155 @@ struct GNUNET_SCHEDULER_TaskContext
 
 
 /**
+ * Function used by event-loop implementations to signal the scheduler
+ * that a particular @a task is ready due to an event of type @a et.
+ *
+ * This function will then queue the task to notify the application
+ * that the task is ready (with the respective priority).
+ *
+ * @param task the task that is ready
+ * @param et information about why the task is ready
+ */
+void
+GNUNET_SCHEDULER_task_ready (struct GNUNET_SCHEDULER_Task *task,
+                             enum GNUNET_SCHEDULER_EventType et);
+
+
+/**
+ * Handle to the scheduler's state to be used by the driver.
+ */
+struct GNUNET_SCHEDULER_Handle;
+
+
+/**
+ * Function called by the driver to tell the scheduler to run some of
+ * the tasks that are ready.  This function may return even though
+ * there are tasks left to run just to give other tasks a chance as
+ * well.  If we return #GNUNET_YES, the driver should call this
+ * function again as soon as possible, while if we return #GNUNET_NO
+ * it must block until the operating system has more work as the
+ * scheduler has no more work to do right now.
+ *
+ * @param sh scheduler handle that was given to the `loop`
+ * @return #GNUNET_OK if there are more tasks that are ready,
+ *          and thus we would like to run more (yield to avoid 
+ *          blocking other activities for too long)
+ *         #GNUNET_NO if we are done running tasks (yield to block)
+ *         #GNUNET_SYSERR on error
+ */
+int
+GNUNET_SCHEDULER_run_from_driver (struct GNUNET_SCHEDULER_Handle *sh);
+
+
+/**
+ * API a driver has to implement for
+ * #GNUNET_SCHEDULER_run_with_driver().
+ */
+struct GNUNET_SCHEDULER_Driver
+{
+
+  /**
+   * Closure to pass to the functions in this struct.
+   */
+  void *cls;
+
+  /**
+   * Add a @a task to be run if the conditions given
+   * in @a fdi are satisfied.
+   *
+   * @param cls closure
+   * @param task task to add
+   * @param fdi conditions to watch for
+   * @return #GNUNET_OK on success, #GNUNET_SYSERR on failure
+   *   (i.e. @a fdi too high or invalid)
+   */
+  int
+  (*add)(void *cls,
+         struct GNUNET_SCHEDULER_Task *task,
+         struct GNUNET_SCHEDULER_FdInfo *fdi);
+
+  /**
+   * Delete a @a task from the set of tasks to be run.
+   *
+   * @param cls closure
+   * @param task task to delete
+   * @param fdi conditions to watch for (must match @e add call)
+   * @return #GNUNET_OK on success, #GNUNET_SYSERR on failure
+   *   (i.e. @a task or @a fdi do not match prior @e add call)
+   */
+  int
+  (*del)(void *cls,
+         struct GNUNET_SCHEDULER_Task *task,
+         const struct GNUNET_SCHEDULER_FdInfo *fdi);
+
+  /**
+   * Set time at which we definitively want to get a wakeup call.
+   *
+   * @param cls closure
+   * @param dt time when we want to wake up next
+   */
+  void
+  (*set_wakeup)(void *cls,
+                struct GNUNET_TIME_Absolute dt);
+
+  /**
+   * Event loop's "main" function, to be called from
+   * #GNUNET_SCHEDULER_run_with_driver() to actually
+   * launch the loop.
+   *
+   * @param cls closure
+   * @param sh scheduler handle to pass to
+   *     #GNUNET_SCHEDULER_run_from_driver()
+   * @return #GNUNET_OK on success, #GNUNET_SYSERR on failure
+   */
+  int
+  (*loop)(void *cls,
+          struct GNUNET_SCHEDULER_Handle *sh);
+  
+};
+
+
+/**
  * Signature of the main function of a task.
  *
  * @param cls closure
- * @param tc context information (why was this task triggered now)
  */
 typedef void
 (*GNUNET_SCHEDULER_TaskCallback) (void *cls);
 
 
 /**
+ * Initialize and run scheduler.  This function will return when all
+ * tasks have completed.  On systems with signals, receiving a SIGTERM
+ * (and other similar signals) will cause #GNUNET_SCHEDULER_shutdown
+ * to be run after the active task is complete.  As a result, SIGTERM
+ * causes all shutdown tasks to be scheduled with reason
+ * #GNUNET_SCHEDULER_REASON_SHUTDOWN.  (However, tasks added
+ * afterwards will execute normally!).  Note that any particular
+ * signal will only shut down one scheduler; applications should
+ * always only create a single scheduler.
+ *
+ * @param driver drive to use for the event loop
+ * @param task task to run first (and immediately)
+ * @param task_cls closure of @a task
+ * @return #GNUNET_OK on success, #GNUNET_SYSERR on failure
+ */
+int
+GNUNET_SCHEDULER_run_with_driver (const struct GNUNET_SCHEDULER_Driver *driver,
+                                  GNUNET_SCHEDULER_TaskCallback task,
+                                  void *task_cls);
+
+
+/**
+ * Obtain the driver for using select() as the event loop.
+ *
+ * @return NULL on error
+ */
+const struct GNUNET_SCHEDULER_Driver *
+GNUNET_SCHEDULER_driver_select (void);
+
+
+/**
  * Signature of the select function used by the scheduler.
  * #GNUNET_NETWORK_socket_select matches it.
  *
@@ -571,7 +801,7 @@ GNUNET_SCHEDULER_add_select (enum GNUNET_SCHEDULER_Priority prio,
  * Sets the select function to use in the scheduler (scheduler_select).
  *
  * @param new_select new select function to use (NULL to reset to default)
- * @param new_select_cls closure for 'new_select'
+ * @param new_select_cls closure for @a new_select
  */
 void
 GNUNET_SCHEDULER_set_select (GNUNET_SCHEDULER_select new_select,
diff --git a/src/util/scheduler.c b/src/util/scheduler.c
index 409a0942f..a7b1d8e2a 100644
--- a/src/util/scheduler.c
+++ b/src/util/scheduler.c
@@ -1,6 +1,6 @@
 /*
       This file is part of GNUnet
-      Copyright (C) 2009-2016 GNUnet e.V.
+      Copyright (C) 2009-2017 GNUnet e.V.
 
       GNUnet is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published
@@ -17,7 +17,6 @@
       Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
       Boston, MA 02110-1301, USA.
  */
-
 /**
  * @file util/scheduler.c
  * @brief schedule computations using continuation passing style
@@ -71,6 +70,35 @@
 
 
 /**
+ * Argument to be passed from the driver to
+ * #GNUNET_SCHEDULER_run_from_driver().  Contains the
+ * scheduler's internal state.
+ */ 
+struct GNUNET_SCHEDULER_Handle
+{
+  /**
+   * Passed here to avoid constantly allocating/deallocating
+   * this element, but generally we want to get rid of this.
+   * @deprecated
+   */
+  struct GNUNET_NETWORK_FDSet *rs;
+
+  /**
+   * Passed here to avoid constantly allocating/deallocating
+   * this element, but generally we want to get rid of this.
+   * @deprecated
+   */
+  struct GNUNET_NETWORK_FDSet *ws;
+
+  /**
+   * Driver we used for the event loop.
+   */
+  const struct GNUNET_SCHEDULER_Driver *driver;
+  
+};
+
+
+/**
  * Entry in list of pending tasks.
  */
 struct GNUNET_SCHEDULER_Task
@@ -96,6 +124,11 @@ struct GNUNET_SCHEDULER_Task
   void *callback_cls;
 
   /**
+   * Handle to the scheduler's state.
+   */
+  const struct GNUNET_SCHEDULER_Handle *sh;
+  
+  /**
    * Set of file descriptors this task is waiting
    * for for reading.  Once ready, this is updated
    * to reflect the set of file descriptors ready
@@ -111,6 +144,18 @@ struct GNUNET_SCHEDULER_Task
   struct GNUNET_NETWORK_FDSet *write_set;
 
   /**
+   * Information about which FDs are ready for this task (and why).
+   */
+  const struct GNUNET_SCHEDULER_FdInfo *fds;
+
+  /**
+   * Storage location used for @e fds if we want to avoid
+   * a separate malloc() call in the common case that this
+   * task is only about a single FD.
+   */
+  struct GNUNET_SCHEDULER_FdInfo fdx;
+
+  /**
    * Absolute timeout value for the task, or
    * #GNUNET_TIME_UNIT_FOREVER_ABS for "no timeout".
    */
@@ -124,6 +169,11 @@ struct GNUNET_SCHEDULER_Task
 #endif
 
   /**
+   * Size of the @e fds array.
+   */
+  unsigned int fds_len;
+  
+  /**
    * Why is the task ready?  Set after task is added to ready queue.
    * Initially set to zero.  All reasons that have already been
    * satisfied (i.e.  read or write ready) will be set over time.
@@ -1742,7 +1792,8 @@ GNUNET_SCHEDULER_add_select (enum GNUNET_SCHEDULER_Priority prio,
   GNUNET_CONTAINER_DLL_insert (pending_head,
                                pending_tail,
                                t);
-  max_priority_added = GNUNET_MAX (max_priority_added, t->priority);
+  max_priority_added = GNUNET_MAX (max_priority_added,
+                                   t->priority);
   LOG (GNUNET_ERROR_TYPE_DEBUG,
        "Adding task %p\n",
        t);
@@ -1750,4 +1801,275 @@ GNUNET_SCHEDULER_add_select (enum GNUNET_SCHEDULER_Priority prio,
   return t;
 }
 
+
+/**
+ * Function used by event-loop implementations to signal the scheduler
+ * that a particular @a task is ready due to an event of type @a et.
+ *
+ * This function will then queue the task to notify the application
+ * that the task is ready (with the respective priority).
+ *
+ * @param task the task that is ready, NULL for wake up calls
+ * @param et information about why the task is ready
+ */
+void
+GNUNET_SCHEDULER_task_ready (struct GNUNET_SCHEDULER_Task *task,
+                             enum GNUNET_SCHEDULER_EventType et)
+{
+  enum GNUNET_SCHEDULER_Reason reason;
+  struct GNUNET_TIME_Absolute now;
+
+  now = GNUNET_TIME_absolute_get ();
+  reason = task->reason;
+  if (now.abs_value_us >= task->timeout.abs_value_us)
+    reason |= GNUNET_SCHEDULER_REASON_TIMEOUT;
+  if ( (0 == (reason & GNUNET_SCHEDULER_REASON_READ_READY)) &&
+       (0 != (GNUNET_SCHEDULER_ET_IN & et)) )
+    reason |= GNUNET_SCHEDULER_REASON_READ_READY;
+  if ( (0 == (reason & GNUNET_SCHEDULER_REASON_WRITE_READY)) &&
+       (0 != (GNUNET_SCHEDULER_ET_OUT & et)) )
+    reason |= GNUNET_SCHEDULER_REASON_WRITE_READY;
+  reason |= GNUNET_SCHEDULER_REASON_PREREQ_DONE;
+  task->reason = reason;
+  task->fds = &task->fdx;
+  task->fdx.et = et;
+  task->fds_len = 1;
+  queue_ready_task (task);
+}
+
+
+/**
+ * Function called by the driver to tell the scheduler to run some of
+ * the tasks that are ready.  This function may return even though
+ * there are tasks left to run just to give other tasks a chance as
+ * well.  If we return #GNUNET_YES, the driver should call this
+ * function again as soon as possible, while if we return #GNUNET_NO
+ * it must block until the operating system has more work as the
+ * scheduler has no more work to do right now.
+ *
+ * @param sh scheduler handle that was given to the `loop`
+ * @return #GNUNET_OK if there are more tasks that are ready,
+ *          and thus we would like to run more (yield to avoid 
+ *          blocking other activities for too long)
+ *         #GNUNET_NO if we are done running tasks (yield to block)
+ *         #GNUNET_SYSERR on error
+ */
+int
+GNUNET_SCHEDULER_run_from_driver (struct GNUNET_SCHEDULER_Handle *sh)
+{
+  enum GNUNET_SCHEDULER_Priority p;
+  struct GNUNET_SCHEDULER_Task *pos;
+  struct GNUNET_TIME_Absolute now;
+
+  /* check for tasks that reached the timeout! */
+  now = GNUNET_TIME_absolute_get ();
+  while (NULL != (pos = pending_timeout_head))
+  {
+    if (now.abs_value_us >= pos->timeout.abs_value_us)
+      pos->reason |= GNUNET_SCHEDULER_REASON_TIMEOUT;
+    if (0 == pos->reason)
+      break;
+    GNUNET_CONTAINER_DLL_remove (pending_timeout_head,
+                                 pending_timeout_tail,
+                                 pos);
+    if (pending_timeout_last == pos)
+      pending_timeout_last = NULL;
+    queue_ready_task (pos);
+  }
+  
+  if (0 == ready_count)
+    return GNUNET_NO;
+
+  /* find out which task priority level we are going to 
+     process this time */
+  max_priority_added = GNUNET_SCHEDULER_PRIORITY_KEEP;
+  GNUNET_assert (NULL == ready_head[GNUNET_SCHEDULER_PRIORITY_KEEP]);
+  /* yes, p>0 is correct, 0 is "KEEP" which should
+   * always be an empty queue (see assertion)! */
+  for (p = GNUNET_SCHEDULER_PRIORITY_COUNT - 1; p > 0; p--)
+  {
+    pos = ready_head[p];
+    if (NULL != pos)
+      break;
+  }
+  GNUNET_assert (NULL != pos);        /* ready_count wrong? */
+
+  /* process all tasks at this priority level, then yield */
+  while (NULL != (pos = ready_head[p]))
+  {
+    GNUNET_CONTAINER_DLL_remove (ready_head[p],
+                                 ready_tail[p],
+                                 pos);
+    ready_count--;
+    current_priority = pos->priority;
+    current_lifeness = pos->lifeness;
+    active_task = pos;
+#if PROFILE_DELAYS
+    if (GNUNET_TIME_absolute_get_duration (pos->start_time).rel_value_us >
+        DELAY_THRESHOLD.rel_value_us)
+    {
+      LOG (GNUNET_ERROR_TYPE_DEBUG,
+           "Task %p took %s to be scheduled\n",
+           pos,
+           GNUNET_STRINGS_relative_time_to_string (GNUNET_TIME_absolute_get_duration (pos->start_time),
+                                                   GNUNET_YES));
+    }
+#endif
+    tc.reason = pos->reason;
+    GNUNET_NETWORK_fdset_zero (sh->rs);
+    GNUNET_NETWORK_fdset_zero (sh->ws);
+    tc.fds_len = pos->fds_len;
+    tc.fds = pos->fds;
+    tc.read_ready = (NULL == pos->read_set) ? sh->rs : pos->read_set;
+    if ( (-1 != pos->read_fd) &&
+         (0 != (pos->reason & GNUNET_SCHEDULER_REASON_READ_READY)) )
+      GNUNET_NETWORK_fdset_set_native (sh->rs,
+                                       pos->read_fd);
+    tc.write_ready = (NULL == pos->write_set) ? sh->ws : pos->write_set;
+    if ((-1 != pos->write_fd) &&
+        (0 != (pos->reason & GNUNET_SCHEDULER_REASON_WRITE_READY)))
+      GNUNET_NETWORK_fdset_set_native (sh->ws,
+                                       pos->write_fd);
+    LOG (GNUNET_ERROR_TYPE_DEBUG,
+         "Running task: %p\n",
+         pos);
+    pos->callback (pos->callback_cls);
+    active_task = NULL;
+    dump_backtrace (pos);
+    destroy_task (pos);
+    tasks_run++;
+  }
+  if (0 == ready_count)
+    return GNUNET_NO;
+  return GNUNET_OK;
+}
+
+
+/**
+ * Initialize and run scheduler.  This function will return when all
+ * tasks have completed.  On systems with signals, receiving a SIGTERM
+ * (and other similar signals) will cause #GNUNET_SCHEDULER_shutdown
+ * to be run after the active task is complete.  As a result, SIGTERM
+ * causes all shutdown tasks to be scheduled with reason
+ * #GNUNET_SCHEDULER_REASON_SHUTDOWN.  (However, tasks added
+ * afterwards will execute normally!).  Note that any particular
+ * signal will only shut down one scheduler; applications should
+ * always only create a single scheduler.
+ *
+ * @param driver drive to use for the event loop
+ * @param task task to run first (and immediately)
+ * @param task_cls closure of @a task
+ * @return #GNUNET_OK on success, #GNUNET_SYSERR on failure
+ */
+int
+GNUNET_SCHEDULER_run_with_driver (const struct GNUNET_SCHEDULER_Driver *driver,
+                                  GNUNET_SCHEDULER_TaskCallback task,
+                                  void *task_cls)
+{
+  int ret;
+  struct GNUNET_SIGNAL_Context *shc_int;
+  struct GNUNET_SIGNAL_Context *shc_term;
+#if (SIGTERM != GNUNET_TERM_SIG)
+  struct GNUNET_SIGNAL_Context *shc_gterm;
+#endif
+#ifndef MINGW
+  struct GNUNET_SIGNAL_Context *shc_quit;
+  struct GNUNET_SIGNAL_Context *shc_hup;
+  struct GNUNET_SIGNAL_Context *shc_pipe;
+#endif
+  struct GNUNET_SCHEDULER_Task tsk;
+  const struct GNUNET_DISK_FileHandle *pr;
+  struct GNUNET_SCHEDULER_Handle sh;
+
+  /* general set-up */
+  GNUNET_assert (NULL == active_task);
+  GNUNET_assert (NULL == shutdown_pipe_handle);
+  shutdown_pipe_handle = GNUNET_DISK_pipe (GNUNET_NO,
+                                           GNUNET_NO,
+                                           GNUNET_NO,
+                                           GNUNET_NO);
+  GNUNET_assert (NULL != shutdown_pipe_handle);
+  pr = GNUNET_DISK_pipe_handle (shutdown_pipe_handle,
+                                GNUNET_DISK_PIPE_END_READ);
+  GNUNET_assert (NULL != pr);
+  my_pid = getpid ();
+
+  /* install signal handlers */
+  LOG (GNUNET_ERROR_TYPE_DEBUG,
+       "Registering signal handlers\n");
+  shc_int = GNUNET_SIGNAL_handler_install (SIGINT,
+                                           &sighandler_shutdown);
+  shc_term = GNUNET_SIGNAL_handler_install (SIGTERM,
+                                            &sighandler_shutdown);
+#if (SIGTERM != GNUNET_TERM_SIG)
+  shc_gterm = GNUNET_SIGNAL_handler_install (GNUNET_TERM_SIG,
+                                             &sighandler_shutdown);
+#endif
+#ifndef MINGW
+  shc_pipe = GNUNET_SIGNAL_handler_install (SIGPIPE,
+                                            &sighandler_pipe);
+  shc_quit = GNUNET_SIGNAL_handler_install (SIGQUIT,
+                                            &sighandler_shutdown);
+  shc_hup = GNUNET_SIGNAL_handler_install (SIGHUP,
+                                           &sighandler_shutdown);
+#endif
+
+  /* Setup initial tasks */
+  current_priority = GNUNET_SCHEDULER_PRIORITY_DEFAULT;
+  current_lifeness = GNUNET_YES;
+  memset (&tsk,
+          0,
+          sizeof (tsk));
+  active_task = &tsk;
+  tsk.sh = &sh;
+  GNUNET_SCHEDULER_add_with_reason_and_priority (task,
+                                                 task_cls,
+                                                 GNUNET_SCHEDULER_REASON_STARTUP,
+                                                 GNUNET_SCHEDULER_PRIORITY_DEFAULT);
+  GNUNET_SCHEDULER_add_now_with_lifeness (GNUNET_NO,
+                                          &GNUNET_OS_install_parent_control_handler,
+                                          NULL);
+  active_task = NULL;
+  driver->set_wakeup (driver->cls,
+                      GNUNET_TIME_absolute_get ());
+
+  /* begin main event loop */
+  sh.rs = GNUNET_NETWORK_fdset_create ();
+  sh.ws = GNUNET_NETWORK_fdset_create ();
+  sh.driver = driver;
+  ret = driver->loop (driver->cls,
+                      &sh);
+  GNUNET_NETWORK_fdset_destroy (sh.rs);
+  GNUNET_NETWORK_fdset_destroy (sh.ws);
+
+  /* uninstall signal handlers */
+  GNUNET_SIGNAL_handler_uninstall (shc_int);
+  GNUNET_SIGNAL_handler_uninstall (shc_term);
+#if (SIGTERM != GNUNET_TERM_SIG)
+  GNUNET_SIGNAL_handler_uninstall (shc_gterm);
+#endif
+#ifndef MINGW
+  GNUNET_SIGNAL_handler_uninstall (shc_pipe);
+  GNUNET_SIGNAL_handler_uninstall (shc_quit);
+  GNUNET_SIGNAL_handler_uninstall (shc_hup);
+#endif
+  GNUNET_DISK_pipe_close (shutdown_pipe_handle);
+  shutdown_pipe_handle = NULL;
+  return ret;
+}
+
+
+/**
+ * Obtain the driver for using select() as the event loop.
+ *
+ * @return NULL on error
+ */
+const struct GNUNET_SCHEDULER_Driver *
+GNUNET_SCHEDULER_driver_select ()
+{
+  GNUNET_break (0); // not implemented
+  return NULL;
+}
+
+
 /* end of scheduler.c */