优先级反转

互斥量反正线程优先级反转功能 更多...

互斥量反正线程优先级反转功能

源码

/*
 * Copyright (c) 2006-2018, RT-Thread Development Team
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Change Logs:
 * Date Author Notes
 * 2018-08-24 yangjie the first version
 */

/*
 * 程序清单：互斥量使用例程
 *
 * 这个例子将创建 3 个动态线程以检查持有互斥量时，持有的线程优先级是否
 * 被调整到等待线程优先级中的最高优先级。
 *
 * 线程 1，2，3 的优先级从高到低分别被创建，
 * 线程 3 先持有互斥量，而后线程 2 试图持有互斥量，此时线程 3 的优先级应该
 * 被提升为和线程 2 的优先级相同。线程 1 用于检查线程 3 的优先级是否被提升
 * 为与线程 2的优先级相同。
 */
#include <rtthread.h>

/* 指向线程控制块的指针 */
static rt_thread_t tid1 = RT_NULL;
static rt_thread_t tid2 = RT_NULL;
static rt_thread_t tid3 = RT_NULL;
static rt_mutex_t mutex = RT_NULL;

#define THREAD_PRIORITY 10
#define THREAD_STACK_SIZE 512
#define THREAD_TIMESLICE 5

/* 线程 1 入口 */
static void thread1_entry(void *parameter)
{
 /* 先让低优先级线程运行 */
 rt_thread_mdelay(100);

 /* 此时 thread3 持有 mutex，并且 thread2 等待持有 mutex */

 /* 检查 thread2 与 thread3 的优先级情况 */
 if (tid2->current_priority != tid3->current_priority)
 {
 /* 优先级不相同，测试失败 */
 rt_kprintf("the priority of thread2 is: %d\n", tid2->current_priority);
 rt_kprintf("the priority of thread3 is: %d\n", tid3->current_priority);
 rt_kprintf("test failed.\n");
 return;
 }
 else
 {
 rt_kprintf("the priority of thread2 is: %d\n", tid2->current_priority);
 rt_kprintf("the priority of thread3 is: %d\n", tid3->current_priority);
 rt_kprintf("test OK.\n");
 }
}

/* 线程 2 入口 */
static void thread2_entry(void *parameter)
{
 rt_err_t result;

 rt_kprintf("the priority of thread2 is: %d\n", tid2->current_priority);

 /* 先让低优先级线程运行 */
 rt_thread_mdelay(50);

 /*
 * 试图持有互斥锁，此时 thread3 持有，应把 thread3 的优先级提升
 * 到 thread2 相同的优先级
 */
 result = rt_mutex_take(mutex, RT_WAITING_FOREVER);

 if (result == RT_EOK)
 {
 /* 释放互斥锁 */
 rt_mutex_release(mutex);
 }
}

/* 线程 3 入口 */
static void thread3_entry(void *parameter)
{
 rt_tick_t tick;
 rt_err_t result;

 rt_kprintf("the priority of thread3 is: %d\n", tid3->current_priority);

 result = rt_mutex_take(mutex, RT_WAITING_FOREVER);
 if (result != RT_EOK)
 {
 rt_kprintf("thread3 take a mutex, failed.\n");
 }

 /* 做一个长时间的循环，500ms */
 tick = rt_tick_get();
 while (rt_tick_get() - tick < (RT_TICK_PER_SECOND / 2)) ;

 rt_mutex_release(mutex);
}

int pri_inversion(void)
{
 /* 创建互斥锁 */
 mutex = rt_mutex_create("mutex", RT_IPC_FLAG_FIFO);
 if (mutex == RT_NULL)
 {
 rt_kprintf("create dynamic mutex failed.\n");
 return -1;
 }

 /* 创建线程 1 */
 tid1 = rt_thread_create("thread1",
 thread1_entry,
 RT_NULL,
 THREAD_STACK_SIZE,
 THREAD_PRIORITY - 1, THREAD_TIMESLICE);
 if (tid1 != RT_NULL)
 rt_thread_startup(tid1);

 /* 创建线程 2 */
 tid2 = rt_thread_create("thread2",
 thread2_entry,
 RT_NULL,
 THREAD_STACK_SIZE,
 THREAD_PRIORITY, THREAD_TIMESLICE);
 if (tid2 != RT_NULL)
 rt_thread_startup(tid2);

 /* 创建线程 3 */
 tid3 = rt_thread_create("thread3",
 thread3_entry,
 RT_NULL,
 THREAD_STACK_SIZE,
 THREAD_PRIORITY + 1, THREAD_TIMESLICE);
 if (tid3 != RT_NULL)
 rt_thread_startup(tid3);

 return 0;
}

/* 导出到 msh 命令列表中 */
MSH_CMD_EXPORT(pri_inversion, pri_inversion sample);