DCE, POSIX, UI) Why does my threaded program not handle signals sensibly?
Signals and threads do not mix well. A lot of programmers start out by writing their code under the mistaken assumption that they can set a signal handler for each thread; this is not the way things work. You can block or unblock signals on a thread-by-thread basis, but this is not the same thing. When it comes to dealing with signals, the best thing you can do is create a thread whose sole purpose is to handle signals for the entire process. This thread should loop calling sigwait(2); this allows it to deal with signals synchronously. You should also make sure that all threads (including the one that calls sigwait) have the signals you are interested in handling blocked. Handling signals synchronously in this way greatly simplifies things. Note, also, that sending signals to other threads within your own process is not a friendly thing to do, unless you are careful with signal masks. For an explanation, see the section on asynchronous cancellation. Finally, using sigwait and installin
