学步园

               linux 系统的中断分上半部与下半部2部分，上半部是硬件中断，会关闭中断，一般处理时间较短，处于中断上下文。下半部有Tasklet与工作队列2种，是中断处理的延时操作，如果中断需要处理较复杂的事务，一般会放到下半部来执行。Tasklet运行在中断上下文，不允许睡眠。工作队列运行在进程上下文，可以睡眠，意味着会引起进程的切换。

              1.  一般的中断代码

                   (1). 包含头文件

                          #include <linux/interrupt.h>

                   (2). 中断例程函数

                          irqreturn_t demo_isr(int irq, void *dev_id)
                         {
                                 int status;
                                 status = read_intr_reg();
                                 if(status)
                                 {
                                       return IRQ_NONE; 
                                 }
                                 else
                                 {
                                        //handle 
                                 }
 
                                 return IRQ_HANDLED
                          }

                   (3). 申请中断

                          static struct demo_dev dev;
                          int retval = request_irq(irq, demo_isr, IRQF_SHARED, "demo_device", &dev);

                   (4). 释放中断

                          free_irq(irq, &dev);

              2.  tasklet 处理代码

                    (1). 包含头文件

                           #include <linux/interrupt.h>

                    (2). 定义tasklet 处理函数

                           void my_tasklet_handle(unsigned long data)
                          {
                                  printk("my tasklet handle\n");
                          }

                    (3). 定义tasklet变量并把该 变量跟tasklet处理函数关联

                           DECLARE_TASKLET(my_tasklet, my_tasklet_handle, NULL);

                    (4). 启动及调度tasklet

                          tasklet_schedule(&my_tasklet);

              3.  工作队列

                   (1). 包含头文件

                          #include <linux/workqueue.h>

                   (2). 定义工作节点变量

                          struct work_struct my_work;

                   (3). 定义及实现工作函数

                          void my_work_function(unsigned long data)
                         {
                                 printk("my work handle\n");
                         }

                   (4). 使工作节点与工作函数相关联

                          DECLARE_WORK(my_work, my_work_function);

                   (5). 启动工作线程

                          schedule_work(&my_work);