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/**
* @file
*
* @brief Priority Scheduler At Tick Handler
*
* @ingroup ScoreScheduler
*/
/*
* COPYRIGHT (c) 1989-2009.
* On-Line Applications Research Corporation (OAR).
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.com/license/LICENSE.
*/
#if HAVE_CONFIG_H
#include "config.h"
#endif
#include <rtems/system.h>
#include <rtems/score/schedulerpriority.h>
void _Scheduler_priority_Tick( void )
{
Thread_Control *executing;
executing = _Thread_Executing;
#ifdef __RTEMS_USE_TICKS_FOR_STATISTICS__
/*
* Increment the number of ticks this thread has been executing
*/
executing->cpu_time_used++;
#endif
/*
* If the thread is not preemptible or is not ready, then
* just return.
*/
if ( !executing->is_preemptible )
return;
if ( !_States_Is_ready( executing->current_state ) )
return;
/*
* The cpu budget algorithm determines what happens next.
*/
switch ( executing->budget_algorithm ) {
case THREAD_CPU_BUDGET_ALGORITHM_NONE:
break;
case THREAD_CPU_BUDGET_ALGORITHM_RESET_TIMESLICE:
#if defined(RTEMS_SCORE_THREAD_ENABLE_EXHAUST_TIMESLICE)
case THREAD_CPU_BUDGET_ALGORITHM_EXHAUST_TIMESLICE:
#endif
if ( (int)(--executing->cpu_time_budget) <= 0 ) {
/*
* A yield performs the ready chain mechanics needed when
* resetting a timeslice. If no other thread's are ready
* at the priority of the currently executing thread, then the
* executing thread's timeslice is reset. Otherwise, the
* currently executing thread is placed at the rear of the
* FIFO for this priority and a new heir is selected.
*/
_Scheduler_Yield();
executing->cpu_time_budget = _Thread_Ticks_per_timeslice;
}
break;
#if defined(RTEMS_SCORE_THREAD_ENABLE_SCHEDULER_CALLOUT)
case THREAD_CPU_BUDGET_ALGORITHM_CALLOUT:
if ( --executing->cpu_time_budget == 0 )
(*executing->budget_callout)( executing );
break;
#endif
}
}
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