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 compltion my_completion; init_completion(&my_completion);
completion的相关定义包含在kernel/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: