Question

在向用户空间发送中断的过程中，我看到了以下代码片段，但我不了解si_int如何影响信号传播。

static int SendToUsrSpace(void) {
  struct siginfo info;
  struct task_struct *t;
  int ret;

  memset(&info, 0, sizeof(struct siginfo));
  info.si_signo = 44;
  info.si_code = SI_QUEUE;
  info.si_int = 1234; // WHY NOT 36 or any random number?
  [...]
  ret = send_sig_info(44, &info, t);
  [...]
}

Answer 1

我认为explanation is in sigqueue(3)。从文本中：

       sigqueue() sends the signal specified in sig to the process whose PID
       is given in pid.  The permissions required to send a signal are the
       same as for kill(2).  As with kill(2), the null signal (0) can be
       used to check if a process with a given PID exists.

       The value argument is used to specify an accompanying item of data
       (either an integer or a pointer value) to be sent with the signal,
       and has the following type:

           union sigval {
               int   sival_int;
               void *sival_ptr;
           };

       If the receiving process has installed a handler for this signal
       using the SA_SIGINFO flag to sigaction(2), then it can obtain this
       data via the si_value field of the siginfo_t structure passed as the
       second argument to the handler.  Furthermore, the si_code field of
       that structure will be set to SI_QUEUE.

因此，1234看起来像一个进程可以拉出的任意值（如果它具有此信号的处理程序）。看起来像一种通过信号发送数据的方式。

其他阅读：我从sigaction(2)到达sigqueue，它列出了siginfo_t的数据类型。

siginfo中的si_int是什么以及它如何影响信号传播

1 个答案: