Thanks Matthew and Robby! I'll give the self-pipe trick a try. Regards, Tony
On 12/21/2014 09:01 AM, Matthew Flatt wrote: > You're right that can't post to a Racket semaphore in a signal handler. > > The way to allocate a global and make it available to Racket code is to > create a new kind of event; the 2006 post is still accurate. In > particular, the new event's polling function (which is called by the > scheduler) can check the global. Calling scheme_signal_received() from > a signal handler ensures that the event's polling function is called > after the global is changed. > > A self-pipe is also a fine approach, since the event wrapper for a pipe > is already available via scheme_make_fd_input_port(). > > At Sat, 20 Dec 2014 14:05:32 -0500, Tony Garnock-Jones wrote: >> Hi all, >> >> If I wanted to catch a Unix signal (say, SIGUSR1) within my Racket >> program, how should I go about it? >> >> My current best guess is: >> - load a C extension, which >> - creates a semaphore and >> - hooks the signal with a handler (MZ_SIGSET looks relevant), which >> - posts to the semaphore when the signal arrives. >> >> However this seems like a recipe for problems. Is it even permitted to >> post to a semaphore from a signal handler? Will the runtime be upset >> about unscheduled intrusions into its demesne? Is it possible for a C >> extension to allocate a global value like a semaphore and make it >> available to Racket code? >> >> Is there a better way? >> >> - Perhaps a self-pipe would be better than a semaphore? >> - A thread from 2006 [1] points at scheme_signal_received() but >> I don't understand why creating an event type is the right thing >> to do. >> >> Tony >> >> [1] http://lists.racket-lang.org/users/archive/2006-July/013999.html >> >> ____________________ >> Racket Users list: >> http://lists.racket-lang.org/users ____________________ Racket Users list: http://lists.racket-lang.org/users
