linux驱动12---kthread与wait_event

1. 功能
init中起两个线程,
  线程1等侍
  线程2每隔1秒唤醒线程1
2. 代码

#include <linux/init.h>
#include <linux/module.h>
#include <linux/workqueue.h>
#include <linux/device.h>
#include <linux/errno.h>
#include <linux/workqueue.h>
#include <linux/dma-mapping.h>
#include <linux/platform_device.h>
#include <linux/interrupt.h>
#include <linux/irqreturn.h>
#include <linux/types.h>
#include <linux/delay.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/spinlock.h>
#include <linux/sched.h>
#include <linux/kthread.h>
#include <linux/wait.h>

static wait_queue_head_t mythread_wq;
struct task_struct *wait_thread_task;
struct task_struct *waken_thread_task;
static int wake_up_condition = 0;

static int my_wait_thread(void* data)
{
    while(1)
    {
        wait_event_interruptible(mythread_wq, wake_up_condition);
        wake_up_condition = 0;
        printk("cong: %s:%d, wakeup \n",__FUNCTION__, __LINE__);
    }
}

static int my_waken_thread(void* data)
{
    while(1)
    {
        wake_up_condition = 1;
        wake_up_interruptible(&mythread_wq);
        msleep(1000);
        printk("cong: %s:%d, waken\n",__FUNCTION__, __LINE__);
    }
}

static int __init hello_init(void)
{
    printk(KERN_ALERT "my first driver\n");
    init_waitqueue_head(&mythread_wq);
    wait_thread_task = kthread_create(my_wait_thread, NULL, "my_wait_thread");
    if (IS_ERR(wait_thread_task)) {
        return PTR_ERR(wait_thread_task);
    }
    wake_up_process(wait_thread_task);

    waken_thread_task = kthread_create(my_waken_thread, NULL, "my_waken_thread");
    if (IS_ERR(waken_thread_task)) {
        return PTR_ERR(waken_thread_task);
    }
    wake_up_process(waken_thread_task);
    return 0;
}

static void __exit hello_exit(void)
{
    printk(KERN_ALERT "goodbye my first dirver\n");
    return ;
}

module_init(hello_init);
module_exit(hello_exit);
MODULE_LICENSE("GPL");

3. 说明
a. 关于kthread
  kthread_create创建的线程不会马上运行,需要调用wake_up_process()后线程开始执行
  kthread_run 会创建并启动线程的函数 
b. 关于wait_event
wait_event_interruptible()
wake_up_interruptible(&mythread_wq);
要想唤醒wait_event_interruptible()的进程，需要滿足两个条件:
  a.condition为真的前提下        //刚开始以为只要这个condition为真就可以了,后来发现不行
  b.还需要调用用wake_up

4.运行结果

[ 40.075829].(0)[1467:insmod]my first driver
[ 40.094922].(0)[1468:my_wait_thread]cong: my_wait_thread:32, wakeup
[ 41.101196].(0)[1469:my_waken_thread]cong: my_waken_thread:43, waken
[ 41.102065].(1)[1468:my_wait_thread]cong: my_wait_thread:32, wakeup
[ 42.111162].(0)[1469:my_waken_thread]cong: my_waken_thread:43, waken
[ 42.112043].(1)[1468:my_wait_thread]cong: my_wait_thread:32, wakeup
[ 43.121312].(0)[1469:my_waken_thread]cong: my_waken_thread:43, waken
[ 43.122197].(1)[1468:my_wait_thread]cong: my_wait_thread:32, wakeup
[ 44.131133].(0)[1469:my_waken_thread]cong: my_waken_thread:43, waken
[ 44.132010].(1)[1468:my_wait_thread]cong: my_wait_thread:32, wakeup
[ 45.141168].(1)[1469:my_waken_thread]cong: my_waken_thread:43, waken
[ 45.142013].(0)[1468:my_wait_thread]cong: my_wait_thread:32, wakeup
[ 46.151078].(0)[1469:my_waken_thread]cong: my_waken_thread:43, waken