Linux源码 DECLARE_COMPLETION宏

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Linux

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completion是一种轻量级的机制,它允许一个线程告诉另一个线程工作已经完成。可以利用下面的宏静态创建completion:

DECLARE_COMPLETION(my_completion);

如果运行时创建completion,则必须采用以下方法动态创建和初始化:

struct compeltion my_completion;
init_completion(&my_completion);

comletion的相关定义包含在include/linux/completion.h中:

struct completion {
unsigned int done;
wait_queue_head_t wait;
};
#define COMPLETION_INITIALIZER(work)
{ 0, __WAIT_QUEUE_HEAD_INITIALIZER((work).wait) }
#define DECLARE_COMPLETION(work)
struct completion work = COMPLETION_INITIALIZER(work)
static inline void init_completion(struct completion *x)
{
x->done = 0;
init_waitqueue_head(&x->wait);
}

要等待completion,可进行如下调用:

void wait_for_completion(struct completion *c);

触发completion事件,调用:

void complete(struct completion *c); //唤醒一个等待线程
void complete_all(struct completion *c); //唤醒所有的等待线程