TASK_KILLABLE：Linux 中的新进程状态

完成机制的适用情况是：您希望将某个任务置为睡眠状态,但随后需要在某些事件完成时唤醒它.它提供了一种简单的、无竞态条件的同步机制.例程 wait_for_completion(struct completion *comp) 将使调用任务处于不可中断睡眠状态,除非完成已经发生.它要求通过 complete(struct completion *comp) 或 complete_all(struct completion *comp) 函数来唤醒进程.

除了 wait_for_completion_killable() 之外,其他正在等待的例程包括：

• wait_for_completion_timeout()
• wait_for_completion_interruptible()
• wait_for_completion_interruptible_timeout()

有关完成结构的定义,请参阅 include/linux/completion.h.

Linux Kernel 2.6.18                          Linux Kernel 2.6.26

==========================================   =============================================

#define nfs_wait_event(clnt, wq, condition)  #define nfs_wait_event(clnt, wq, condition)

 ({                                           ({

  int __retval = 0;                            int __retval = 

                                                   wait_event_killable(wq, condition);

    if (clnt->cl_intr) {                        __retval;

     sigset_t oldmask;                        })

     rpc_clnt_sigmask(clnt, &oldmask);

     __retval = 

     wait_event_interruptible(wq, condition);

       rpc_clnt_sigunmask(clnt, &oldmask);

    } else

        wait_event(wq, condition);

        __retval;

 })

Linux Kernel 2.6.18                                   

=================================           

static ssize_t nfs_direct_wait(struct nfs_direct_req *dreq) 

{                                                           

  ssize_t result = -EIOCBQUEUED;                              



  /* Async requests don''t wait here */                         

 if (dreq->iocb)                                              

      goto out;                                                    



 result = wait_for_completion_interruptible(&dreq->completion);



 if (!result)                                                 

   result = dreq->error;                                        

 if (!result)                                                 

   result = dreq->count;                                        



out:                                                            

  kref_put(&dreq->kref, nfs_direct_req_release);

  return (ssize_t) result;

}                                                               







Linux Kernel 2.6.26

=====================

static ssize_t nfs_direct_wait(struct nfs_direct_req *dreq)

{

  ssize_t result = -EIOCBQUEUED;

  /* Async requests don''t wait here */

  if (dreq->iocb)

    goto out;



  result = wait_for_completion_killable(&dreq->completion);

  if (!result)

    result = dreq->error;

  if (!result)

    result = dreq->count;

out:

   return (ssize_t) result;

 }