一步一步學Linux C：sigsuspend 執行過程分析

用於在接受到某個信號之前，臨時用mask替換進程的信號掩碼，並暫停進程執行，直到收到信號為止。

1. 　　/*The sigsuspend() function replaces the current signal mask of the calling thread with the set of signals pointed
2. to by sigmask and then suspends the thread until delivery of a signal whose action is either to execute a signal-catching
3. function or to terminate the process. This will not cause any other signals that may have been pending on the process to
4. become pending on the thread.
5. 　　If the action is to terminate the process then sigsuspend() will never return. If the action is to execute a signal-catching
6. function, thensigsuspend() will return after the signal-catching function returns, with the signal mask restored to the set
7. that existed prior to thesigsuspend() call.
8. 　　It is not possible to block signals that cannot be ignored. This is enforced by the system without causing an error to be indicated.*/