关于信号量例子的疑问

发布于 2010-01-06 14:15:46 浏览：5769 订阅该版

代码及运行结果如下：

/*
 * File      : application.c
 * This file is part of RT-Thread RTOS
 * COPYRIGHT (C) 2006, RT-Thread Development Team
 *
 * The license and distribution terms for this file may be
 * found in the file LICENSE in this distribution or at
 * [http://www.rt-thread.org/license/LICENSE](http://www.rt-thread.org/license/LICENSE)
 *
 * Change Logs:
 * Date           Author       Notes
 * 2009-01-05     Bernard      the first version
 */

/**
 * @addtogroup STM32
 */
/*@{*/

#include <rtthread.h>
#include "led.h"
#include <stdint.h >
#include "stm32f10x.h "
extern void assert_failed(u8* file, u32 line);
extern rt_base_t rt_hw_interrupt_disable(void);
/* enable interrupt */
extern   rt_hw_interrupt_enable(rt_base_t);

//当信号量的值等于零时，信号量值加一，并且唤醒等待在该信号量上的线程队列中的首线
//程，由它获取信号量。
//使用信号量的例子
/* 信号量对象*/
struct rt_semaphore sem;
/* thread1线程入口*/
void thread1_entry(void* parameter)
{
  while (1)
  {
     /* 采用永久等待方式获取信号量*/
	 rt_kprintf("thread1:taken semaphoreing......
");
     if(rt_sem_take(&sem, RT_WAITING_FOREVER) == RT_EOK){ /* 获取到信号量*/
		rt_kprintf("thread1:taken semaphore
");
        rt_thread_delay(10);
       // rt_sem_release(&sem);
     }
  }
}

/* thread2线程入口*/
void thread2_entry(void* parameter)
{ 
  //register rt_base_t temp;
  const char char_c0[] = {"thread2:in the thread2.
" };
  /* disable interrupt */
   
 while (1)
 {
    rt_sem_release(&sem);
	// temp = rt_hw_interrupt_disable();
	rt_kprintf(char_c0);	
    /* enable interrupt */
   // rt_hw_interrupt_enable(temp);
  	rt_thread_delay(100);

/* 以非等待方式试图获取信号量*/
 /* if(rt_sem_take(&sem, RT_WAITING_NO) == RT_EOK){
     rt_kprintf("thread2:taken semaphore ok with no waiting
");
     rt_thread_delay(10);
     rt_sem_release(&sem);
  }else{
        rt_kprintf("thread2: take semaphore failed with no waiting
");
  }
   */
 }
}

int rt_application_init()
{
    rt_thread_t thread;
	/* 初始化sem对象*/
    rt_sem_init(&sem, "semt", 0, 1);

/* 创建线程，入口是thread1 entry */
    thread = rt_thread_create("t1",thread1_entry, RT_NULL,512, 1, 10);
    if(thread != RT_NULL){
	   rt_thread_startup(thread);
	}	
	
	/* 创建线程，入口是thread2 entry */
    thread = rt_thread_create("t2", thread2_entry, RT_NULL, 512, 2, 10);
    if(thread != RT_NULL){
	   rt_thread_startup(thread);
    }   
	return 0;
}
/*@}*/

rt_sem_init(&sem, "semt", 0, 0);
运行结果如下：
  | /
- RT - Thread Operating System
 / |  0.3.0 build Jan  6 2010
 2006 - 2009 Copyright by rt-thread team
startup a thread:t1 with priority:1
thread resume:  t1
startup a thread:t2 with priority:2
thread resume:  t2
startup a thread:tidle with priority:31
thread resume:  tidle
thread1:taken semaphoreing......
thread suspend:  t1
thread resume:  t1
thread1:taken semaphore
thread suspend:  t1
thread2:in the thread2.
thread suspend:  t2
thread1:taken semaphoreing......
thread suspend:  t1
thread resume:  t1
thread1:taken semaphore
thread suspend:  t1
thread2:in the thread2.
thread suspend:  t2

rt_sem_init(&sem, "semt", 0, 1);
运行结果：
  | /
- RT - Thread Operating System
 / |  0.3.0 build Jan  6 2010
 2006 - 2009 Copyright by rt-thread team
startup a thread:t1 with priority:1
thread resume:  t1
startup a thread:t2 with priority:2
thread resume:  t2
startup a thread:tidle with priority:31
thread resume:  tidle
thread1:taken semaphoreing......
thread suspend:  t1
thread resume:    （这里出问题了？）
thread resume: thread disorder, 4
thread2:in the thread2.
thread suspend:  t2
thread2:in the thread2.
thread suspend:  t2
thread2:in the thread2.
thread suspend:  t2
thread2:in the thread2.
thread suspend:  t2
thread2:in the thread2.
thread suspend:  t2

8 个回答

dp_mcu 2010-01-06

这家伙很懒，什么也没写！

dp_mcu 2010-01-06

这家伙很懒，什么也没写！

flag=1时运行结果：
\ | /
- RT - Thread Operating System
 / | \ 0.3.0 build Jan  6 2010
 2006 - 2009 Copyright by rt-thread team
startup a thread:t1 with priority:1
thread resume:  t1
insert thread, the priority: 1
startup a thread:t2 with priority:2
thread resume:  t2
insert thread, the priority: 2
startup a thread:tidle with priority:31
thread resume:  tidle
insert thread, the priority: 31
thread1:taken semaphoreing......
thread suspend:  t1
remove thread, the priority: 1
[0]switch to priority#2 thread:t2
thread resume:  
thread resume: thread disorder, 4
thread2:in the thread2.
thread suspend:  t2
remove thread, the priority: 2
[0]switch to priority#31 thread:tidle
insert thread, the priority: 2
[1]switch to priority#2 thread:t2
switch in interrupt
thread2:in the thread2.
thread suspend:  t2
remove thread, the priority: 2
[0]switch to priority#31 thread:tidle
insert thread, the priority: 2
[1]switch to priority#2 thread:t2
switch in interrupt
thread2:in the thread2.
thread suspend:  t2
remove thread, the priority: 2
[0]switch to priority#31 thread:tidle
insert thread, the priority: 2
[1]switch to priority#2 thread:t2
switch in interrupt
thread2:in the thread2.
thread suspend:  t2
remove thread, the priority: 2
[0]switch to priority#31 thread:tidle
insert thread, the priority: 2
[1]switch to priority#2 thread:t2
switch in interrupt
thread2:in the thread2.
thread suspend:  t2
remove thread, the priority: 2
[0]switch to priority#31 thread:tidle

dp_mcu 2010-01-06

这家伙很懒，什么也没写！

flag=0
 \ | /
- RT - Thread Operating System
 / | \ 0.3.0 build Jan  6 2010
 2006 - 2009 Copyright by rt-thread team
startup a thread:t1 with priority:1
thread resume:  t1
insert thread, the priority: 1
startup a thread:t2 with priority:2
thread resume:  t2
insert thread, the priority: 2
startup a thread:tidle with priority:31
thread resume:  tidle
insert thread, the priority: 31
thread1:taken semaphoreing......
thread suspend:  t1
remove thread, the priority: 1
[0]switch to priority#2 thread:t2
thread resume:  t1
insert thread, the priority: 1
[0]switch to priority#1 thread:t1
thread1:taken semaphore
thread suspend:  t1
remove thread, the priority: 1
[0]switch to priority#2 thread:t2
thread2:in the thread2.
thread suspend:  t2
remove thread, the priority: 2
[0]switch to priority#31 thread:tidle
insert thread, the priority: 1
[1]switch to priority#1 thread:t1
switch in interrupt
thread1:taken semaphoreing......
thread suspend:  t1
remove thread, the priority: 1
[0]switch to priority#31 thread:tidle
insert thread, the priority: 2
[1]switch to priority#2 thread:t2
switch in interrupt
thread resume:  t1
insert thread, the priority: 1
[0]switch to priority#1 thread:t1
thread1:taken semaphore
thread suspend:  t1
remove thread, the priority: 1
[0]switch to priority#2 thread:t2
thread2:in the thread2.
thread suspend:  t2
remove thread, the priority: 2

bernard 2010-01-06

这家伙很懒，什么也没写！

dp_mcu 2010-01-06

这家伙很懒，什么也没写！

一开始就会打印：
采用优先级方式时，任务1申请信号，没有得到(它的优先级高)，所以会挂起，
打印如下：thread1:taken semaphoreing......
thread suspend:  t1
接着切换到任务2，任务2发送信号，于是就唤醒了任务1，接着打印：
thread resume:               //（这里出问题了,冒号后没有字符）
thread resume: thread disorder, 4
thread2:in the thread2.
thread suspend:  t2
thread2:in the thread2.
thread suspend:  t2

当flag=0时，采用fifo方式时，任务1申请信号，没有得到(它的优先级高)，所以会挂起，
打印如下：thread1:taken semaphoreing......
thread suspend:  t1
接着切换到任务2，任务2发送信号，于是就唤醒了任务1，接着打印：
thread resume:  t1
thread1:taken semaphore
thread suspend:  t1
thread2:in the thread2.
thread suspend:  t2
thread1:taken semaphoreing......
thread suspend:  t1
thread resume:  t1
thread1:taken semaphore
thread suspend:  t1

所以按照上述比较，我认为是t1的挂起操作没有成功，也即
rt_inline rt_err_t rt_ipc_object_suspend(struct rt_ipc_object *ipc, struct rt_thread *thread)
{
	/* suspend thread */
	rt_thread_suspend(thread);
	ipc->suspend_thread_count ++;

switch (ipc->parent.flag)
	{
	case RT_IPC_FLAG_FIFO:
		rt_list_insert_before(&(ipc->suspend_thread), &(thread->tlist));
		break;

case RT_IPC_FLAG_PRIO:
		{
			struct rt_list_node* n;
			struct rt_thread* sthread;

/* find a suitable position */
			for (n = ipc->suspend_thread.next; n != &(ipc->suspend_thread);
				n = n->next)
			{
				sthread = rt_list_entry(n, struct rt_thread, tlist);

/* find out */
				if (thread->current_priority < sthread->current_priority)
				{
					/* insert this thread before the sthread */
					rt_list_insert_before(&(sthread->tlist), &(thread->tlist));
					break;
				}
			}
		}
		break;
	}

return RT_EOK;
}

函数，现在我还看不太明白。

bernard 2010-01-06

这家伙很懒，什么也没写！

估计你用的是0.3.0 rc1以前的版本，这个问题softwind说过，并修正了，0.3.0 rc1的代码如下：

```

rt_inline rt_err_t rt_ipc_object_suspend(struct rt_ipc_object *ipc, struct rt_thread *thread)
{
	/* suspend thread */
	rt_thread_suspend(thread);
	ipc->suspend_thread_count ++;

switch (ipc->parent.flag)
	{
	case RT_IPC_FLAG_FIFO:
		rt_list_insert_before(&(ipc->suspend_thread), &(thread->tlist));
		break;

case RT_IPC_FLAG_PRIO:
		{
			struct rt_list_node* n;
			struct rt_thread* sthread;

/* find a suitable position */
			for (n = ipc->suspend_thread.next; n != &(ipc->suspend_thread);
				n = n->next)
			{
				sthread = rt_list_entry(n, struct rt_thread, tlist);

/* not found a suitable position, append to the end of suspend_thread list */
			if (n == &(ipc->suspend_thread))
				rt_list_insert_before(&(ipc->suspend_thread), &(thread->tlist));
		}
		break;
	}

return RT_EOK;
}

```