Hi! On Tue, Jan 22, 2008 at 12:52:51AM -0800, William Ahern wrote:
>Signal handlers and masks are inherited across fork() and pthread_create(). >And masks are inherited across exec(), too, I think. >You could add code to each thread to do this. Of course, there are race >conditions. Imagine if a signal is raised after a thread starts but before >it can block the signal. This is especially troublesome if you dynamically >create threads. A way to avoid the race is to block all signals (using pthread_sigmask) in main() early and unblock them in *one* thread (which is in duty for signal handling) *only* later, after having created the other threads. If you create threads afterwards, block them again before pthread_create and unblock again afterwards, again. Then the other threads all inherit the signal mask blocking all signals so there's always only at maximum one thread which gets the signals. >With SIGPIPE the answer is simple, though. Block the signal from the main >thread before creating any other threads. All threads will inherit the >block, and SIGPIPE can never squeeze through. I think you mean *ignore* SIGPIPE. >But, by block I mean actually using sigaction(2) (see the code I posted >earlier), not by installing a libevent handler. Installing a SIGPIPE handler >through libevent is pointless and a waste of CPU, and of course it doesn't >do what you want anyway. sigaction doesn't *block* signals in Unix/POSIX terminology. It sets up signal *handling*, to either default handling, user handling or ignoring the signal. With libevent, you either ignore a signal using sigaction or you handle it using libevent and don't touch it yourself with sigaction (but you may block/unblock it using sigprocmask [in single threaded programs] or pthread_sigmask [in multithreaded programs]). Your recommendation of *ignoring* SIGPIPE still stands, and instead you handle EPIPE in write(2) (or send(2)). >[...] Kind regards, Hannah. _______________________________________________ Libevent-users mailing list Libevent-users@monkey.org http://monkeymail.org/mailman/listinfo/libevent-users
