simschedulerbasicp.nc

tinyos-2.x.rar

/*
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 * IN NO EVENT SHALL STANFORD UNIVERSITY BE LIABLE TO ANY PARTY FOR
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 * DAMAGE.
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 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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 * HAS NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES,
 * ENHANCEMENTS, OR MODIFICATIONS."
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/**
 *
 * SimSchedulerBasic implements the default TinyOS scheduler sequence
 * (documented in TEP 106) for the TOSSIM platform. Its major departure
 * from the standard TinyOS scheduler is that tasks are executed
 * within TOSSIM events. This introduces task latency.
 *
 * @author Philip Levis
 * @author Cory Sharp
 * @date   August 19 2005
 */


#include <sim_event_queue.h>

module SimSchedulerBasicP {
  provides interface Scheduler;
  provides interface TaskBasic[uint8_t id];
}
implementation
{
  enum
  {
    NUM_TASKS = uniqueCount("TinySchedulerC.TaskBasic"),
    NO_TASK = 255,
  };

  uint8_t m_head;
  uint8_t m_tail;
  uint8_t m_next[NUM_TASKS];

  /* This simulation state is kept on a per-node basis.
     Better to take advantage of nesC's automatic state replication
     than try to do it ourselves. */
  bool sim_scheduler_event_pending = FALSE;
  sim_event_t sim_scheduler_event;

  int sim_config_task_latency() {return 100;}
  

  /* Only enqueue the event for execution if it is
     not already enqueued. If there are more tasks in the
     queue, the event will re-enqueue itself (see the handle
     function). */
  
  void sim_scheduler_submit_event() {
    if (sim_scheduler_event_pending == FALSE) {
      sim_scheduler_event.time = sim_time() + sim_config_task_latency();
      sim_queue_insert(&sim_scheduler_event);
      sim_scheduler_event_pending = TRUE;
    }
  }

  void sim_scheduler_event_handle(sim_event_t* e) {
    sim_scheduler_event_pending = FALSE;

    // If we successfully executed a task, re-enqueue the event. This
    // will always succeed, as sim_scheduler_event_pending was just
    // set to be false.  Note that this means there will be an extra
    // execution (on an empty task queue). We could optimize this
    // away, but this code is cleaner, and more accurately reflects
    // the real TinyOS main loop.
    
    if (call Scheduler.runNextTask()) {
      sim_scheduler_submit_event();
    }
  }

  
  /* Initialize a scheduler event. This should only be done
   * once, when the scheduler is initialized. */
  void sim_scheduler_event_init(sim_event_t* e) {
    e->mote = sim_node();
    e->force = 0;
    e->data = NULL;
    e->handle = sim_scheduler_event_handle;
    e->cleanup = sim_queue_cleanup_none;
  }



  // Helper functions (internal functions) intentionally do not have atomic
  // sections.  It is left as the duty of the exported interface functions to
  // manage atomicity to minimize chances for binary code bloat.

  // move the head forward
  // if the head is at the end, mark the tail at the end, too
  // mark the task as not in the queue
  uint8_t popTask()
  {
    if( m_head != NO_TASK )
    {
      uint8_t id = m_head;
      m_head = m_next[m_head];
      if( m_head == NO_TASK )
      {
	m_tail = NO_TASK;
      }
      m_next[id] = NO_TASK;
      return id;
    }
    else
    {
      return NO_TASK;
    }
  }
  
  bool isWaiting( uint8_t id )
  {
    return (m_next[id] != NO_TASK) || (m_tail == id);
  }

  bool pushTask( uint8_t id )
  {
    if( !isWaiting(id) )
    {
      if( m_head == NO_TASK )
      {
	m_head = id;
	m_tail = id;
      }
      else
      {
	m_next[m_tail] = id;
	m_tail = id;
      }
      return TRUE;
    }
    else
    {
      return FALSE;
    }
  }
  
  command void Scheduler.init()
  {
    dbg("Scheduler", "Initializing scheduler.\n");
    atomic
    {
      memset( m_next, NO_TASK, sizeof(m_next) );
      m_head = NO_TASK;
      m_tail = NO_TASK;

      sim_scheduler_event_pending = FALSE;
      sim_scheduler_event_init(&sim_scheduler_event);
    }
  }
  
  command bool Scheduler.runNextTask()
  {
    uint8_t nextTask;
    atomic
    {
      nextTask = popTask();
      if( nextTask == NO_TASK )
      {
	dbg("Scheduler", "Told to run next task, but no task to run.\n");
	return FALSE;
      }
    }
    dbg("Scheduler", "Running task %hhu.\n", nextTask);
    signal TaskBasic.runTask[nextTask]();
    return TRUE;
  }

  command void Scheduler.taskLoop() {
    // This should never run.
  }
  
  /**
   * Return SUCCESS if the post succeeded, EBUSY if it was already posted.
   */
  
  async command error_t TaskBasic.postTask[uint8_t id]()
  {
    error_t result;
    atomic {
      result =  pushTask(id) ? SUCCESS : EBUSY;
    }
    if (result == SUCCESS) {
      dbg("Scheduler", "Posting task %hhu.\n", id);
      sim_scheduler_submit_event();
    }
    else {
      dbg("Scheduler", "Posting task %hhu, but already posted.\n", id);
    }
    return result;
  }

  default event void TaskBasic.runTask[uint8_t id]()
  {
  }



}