/* -----------------------------------------------------------------------------
 *
 * (c) The GHC Team, 1995-2005
 *
 * Interval timer service for profiling and pre-emptive scheduling.
 *
 * ---------------------------------------------------------------------------*/

/*
 * The interval timer is used for profiling and for context switching in the
 * threaded build. 
 *
 * This file defines the platform-independent view of interval timing, relying
 * on platform-specific services to install and run the timers.
 *
 */
#include "Rts.h"
#include "RtsFlags.h"
#include "Proftimer.h"
#include "Schedule.h"
#include "Timer.h"
#include "Ticker.h"
#include "Capability.h"
#include "RtsSignals.h"

/* ticks left before next pre-emptive context switch */
static int ticks_to_ctxt_switch = 0;

#if defined(THREADED_RTS)
/* idle ticks left before we perform a GC */
static int ticks_to_gc = 0;
#endif

/*
 * Function: handle_tick()
 *
 * At each occurrence of a tick, the OS timer will invoke
 * handle_tick().
 */
static
void
handle_tick(int unused STG_UNUSED)
{
#ifdef PROFILING
  handleProfTick();
#endif
  if (RtsFlags.ConcFlags.ctxtSwitchTicks > 0) {
      ticks_to_ctxt_switch--;
      if (ticks_to_ctxt_switch <= 0) {
	  ticks_to_ctxt_switch = RtsFlags.ConcFlags.ctxtSwitchTicks;
	  context_switch = 1;	/* schedule a context switch */
      }
  }

#if defined(THREADED_RTS)
  /* 
   * If we've been inactive for idleGCDelayTime (set by +RTS
   * -I), tell the scheduler to wake up and do a GC, to check
   * for threads that are deadlocked.
   */
  switch (recent_activity) {
  case ACTIVITY_YES:
      recent_activity = ACTIVITY_MAYBE_NO;
      ticks_to_gc = RtsFlags.GcFlags.idleGCDelayTime /
                    RtsFlags.MiscFlags.tickInterval;
      break;
  case ACTIVITY_MAYBE_NO:
      if (ticks_to_gc == 0) break; /* 0 ==> no idle GC */
      ticks_to_gc--;
      if (ticks_to_gc == 0) {
	  ticks_to_gc = RtsFlags.GcFlags.idleGCDelayTime /
                        RtsFlags.MiscFlags.tickInterval;
	  recent_activity = ACTIVITY_INACTIVE;
	  blackholes_need_checking = rtsTrue;
	  /* hack: re-use the blackholes_need_checking flag */
	  wakeUpRts();
      }
      break;
  default:
      break;
  }
#endif
}

int
startTimer(void)
{
#ifdef PROFILING
  initProfTimer();
#endif

  return startTicker(RtsFlags.MiscFlags.tickInterval, handle_tick);
}

int
stopTimer(void)
{
  return stopTicker();
}
