contiki/core/sys/mt.c
Benoît Thébaudeau 81805129f8 mt: Fix preemption
Preemption was supposed to be supported, but it had no means of safely
updating the state of a thread, so mt_exec() could fail to resume a
preempted thread.

mt_exec() is allowed to be called only from the main Contiki thread, so
the mt threads passed to it may be only ready or exited, not running.
Consequently, there is no need for a distinction between the ready and
running states, so merge them as a started state, which avoids having to
update the state of a thread upon preemption.

Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau.dev@gmail.com>
2016-11-24 22:30:26 +01:00

110 lines
3.6 KiB
C

/*
* Copyright (c) 2006, Swedish Institute of Computer Science.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* This file is part of the Contiki operating system.
*
* Author: Adam Dunkels <adam@sics.se>
*
*/
/**
* \file
* Implementation of the archtecture agnostic parts of the preemptive
* multithreading library for Contiki.
*
* \author
* Adam Dunkels <adam@sics.se>
*
*/
#include "contiki.h"
#include "sys/mt.h"
#include "sys/cc.h"
static struct mt_thread *current;
/*--------------------------------------------------------------------------*/
void
mt_init(void)
{
mtarch_init();
}
/*--------------------------------------------------------------------------*/
void
mt_remove(void)
{
mtarch_remove();
}
/*--------------------------------------------------------------------------*/
void
mt_start(struct mt_thread *thread, void (* function)(void *), void *data)
{
/* Call the architecture dependant function to set up the processor
stack with the correct parameters. */
mtarch_start(&thread->thread, function, data);
thread->state = MT_STATE_STARTED;
}
/*--------------------------------------------------------------------------*/
void
mt_exec(struct mt_thread *thread)
{
if(thread->state == MT_STATE_STARTED) {
current = thread;
/* Switch context to the thread. The function call will not return
until the the thread has yielded, or is preempted. */
mtarch_exec(&thread->thread);
}
}
/*--------------------------------------------------------------------------*/
void
mt_yield(void)
{
mtarch_pstop();
/* This function is called from the running thread, and we call the
switch function in order to switch the thread to the main Contiki
program instead. For us, the switch function will not return
until the next time we are scheduled to run. */
mtarch_yield();
}
/*--------------------------------------------------------------------------*/
void
mt_exit(void)
{
mtarch_pstop();
current->state = MT_STATE_EXITED;
mtarch_yield();
}
/*--------------------------------------------------------------------------*/
void
mt_stop(struct mt_thread *thread)
{
mtarch_stop(&thread->thread);
}
/*--------------------------------------------------------------------------*/