Some information about tasklet

最新推荐文章于 2024-07-05 15:58:58 发布

vincent_zou

最新推荐文章于 2024-07-05 15:58:58 发布

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分类专栏： Quotation from reading 文章标签： reference struct structure locking function prototype

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本文详细介绍了Linux内核中Tasklets的概念及使用方法。Tasklets是一种轻量级的任务调度机制，用于在中断上下文中安排延迟执行的任务。文章解释了Tasklets的数据结构、声明方式，并强调了在编写Tasklets处理器函数时需要注意的问题。

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Tasklets

The Tasklet Structure

Tasklets are represented by the tasklet_struct structure. Each structure represents a unique tasklet. The structure is declared in <linux/interrupt.h>:

struct tasklet_struct {
        struct tasklet_struct *next;  /* next tasklet in the list */
        unsigned long state;          /* state of the tasklet */
        atomic_t count;               /* reference counter */
        void (*func)(unsigned long);  /* tasklet handler function */
        unsigned long data;           /* argument to the tasklet function */
};

Using Tasklets

Declaring Your Tasklet

You can create tasklets statically or dynamically. 
What option you choose depends on whether
 you have (or want) a direct or indirect reference to the tasklet. 
If you are going to statically create the tasklet
 (and thus have a direct reference to it), 
use one of two macros in <linux/interrupt.h>:
DECLARE_TASKLET(name, func, data);//the argument "name" is up to you !not 
					//so importent! 


Writing Your Tasklet Handler
The tasklet handler must match the correct prototype:
void tasklet_handler(unsigned long data)


    As with softirqs, tasklets cannot sleep. This means you cannot 
use semaphores or other blocking functions in a tasklet. Tasklets 
also run with all interrupts enabled, so you must take 
precautions (for example, disable interrupts and obtain a lock)
if your tasklet shares data with an interrupt handler. Unlike softirqs,
however, two of the same tasklets never run concurrentlyalthough 
two different tasklets can run at the same time on two different processors. 
If your tasklet shares data with another tasklet or softirq, you need to use
proper locking .