关于sigsuspend的返回问题

lsmup

int main(void) {
   sigset_t   newmask, oldmask, zeromask;
   if (signal(SIGINT, sig_int) == SIG_ERR)
      err_sys("signal(SIGINT) error");
   sigemptyset(&zeromask);
   sigemptyset(&newmask);
   sigaddset(&newmask, SIGINT);
   /* block SIGINT and save current signal mask */
   if (sigprocmask(SIG_BLOCK, &newmask, &oldmask) int sigsuspend(const sigset_t *sigmask);
           Returns: 1 with errno set to EINTR
    both reset the signal mask and put the process to sleep in a single atomic operation.
   The signal mask of the process is set to the value pointed to by sigmask.
Then the process is suspended until a signal is caught or until a
signal occurs that terminates the process. If a signal is caught and if
the signal handler returns, then sigsuspend returns, and the signal mask of the process is set to its value before the call to sigsuspend.
开始的signalmask:(sigprocmask(SIG_BLOCK, &newmask, &oldmask)
调用sigsuspend：zeromask.
调用返回后：oldmask
进程挂起直到：
1：捕捉到一个信号并且从该信号的处理程序返回之后，sigsuspend才返回。将该进程的sigmask设置为调    用该函数之前的sigmask.
2: 一个信号的发生引起了该进程的终止
现在的关键问题是：sigsuspend将sigmask设置为了zeromask,但是结果：in sig_int: SIGINT
－－－－－If a signal is caught and if
the signal handler returns, then sigsuspend returns, and the signal mask of the process is set to its value before the call to sigsuspend.
这里的and之后的语句应该是说在sigsuspend返回之前就已经产生了的结果，更确切地说应该是在signal handler执行之前就已经恢复了sigmask------不然不会产生这样的结果。
有空的时候好好分析下，把脉络理清楚


本文来自ChinaUnix博客，如果查看原文请点：http://blog.chinaunix.net/u1/35079/showart_273392.html