score/src/threadresettimeslice.c

0001 /* SPDX-License-Identifier: BSD-2-Clause */
0002
0003 /**
0004  * @file
0005  *
0006  * @ingroup RTEMSScoreThread
0007  *
0008  * @brief This source file contains the definition of
0009  *   ::_Thread_CPU_budget_reset_timeslice and the implementation of
0010  *   _Thread_CPU_budget_consume_and_yield() and
0011  *   _Thread_CPU_budget_set_to_ticks_per_timeslice().
0012  */
0013
0014 /*
0015  * Copyright (C) 2021 embedded brains GmbH & Co. KG
0016  * Copyright (C) 2010 Gedare Bloom  <gedare@rtems.org>
0017  *
0018  * Redistribution and use in source and binary forms, with or without
0019  * modification, are permitted provided that the following conditions
0020  * are met:
0021  * 1. Redistributions of source code must retain the above copyright
0022  *    notice, this list of conditions and the following disclaimer.
0023  * 2. Redistributions in binary form must reproduce the above copyright
0024  *    notice, this list of conditions and the following disclaimer in the
0025  *    documentation and/or other materials provided with the distribution.
0026  *
0027  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
0028  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
0029  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
0030  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
0031  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
0032  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
0033  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
0034  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
0035  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
0036  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
0037  * POSSIBILITY OF SUCH DAMAGE.
0038  */
0039
0040 #ifdef HAVE_CONFIG_H
0041 #include "config.h"
0042 #endif
0043
0044 #include <rtems/score/threadcpubudget.h>
0045 #include <rtems/score/threadimpl.h>
0046 #include <rtems/score/statesimpl.h>
0047 #include <rtems/score/watchdogticks.h>
0048
0049 void _Thread_CPU_budget_consume_and_yield( Thread_Control *the_thread )
0050 {
0051   uint32_t budget_available;
0052
0053   if ( !the_thread->is_preemptible ) {
0054     return;
0055   }
0056
0057   if ( !_States_Is_ready( the_thread->current_state ) ) {
0058     return;
0059   }
0060
0061   budget_available = the_thread->CPU_budget.available;
0062
0063   if ( budget_available == 1 ) {
0064     the_thread->CPU_budget.available = _Watchdog_Ticks_per_timeslice;
0065
0066     /*
0067      *  A yield performs the ready chain mechanics needed when
0068      *  resetting a timeslice.  If no other thread's are ready
0069      *  at the priority of the currently executing thread, then the
0070      *  executing thread's timeslice is reset.  Otherwise, the
0071      *  currently executing thread is placed at the rear of the
0072      *  FIFO for this priority and a new heir is selected.
0073      */
0074     _Thread_Yield( the_thread );
0075   } else {
0076     the_thread->CPU_budget.available = budget_available - 1;
0077   }
0078 }
0079
0080 void _Thread_CPU_budget_set_to_ticks_per_timeslice(
0081   Thread_Control *the_thread
0082 )
0083 {
0084   the_thread->CPU_budget.available = _Watchdog_Ticks_per_timeslice;
0085 }
0086
0087 const Thread_CPU_budget_operations _Thread_CPU_budget_reset_timeslice = {
0088   .at_tick = _Thread_CPU_budget_consume_and_yield,
0089   .at_context_switch = _Thread_CPU_budget_set_to_ticks_per_timeslice,
0090   .initialize = _Thread_CPU_budget_set_to_ticks_per_timeslice
0091 };