Using Sleep() while using timers through setitimer

Question

I am using a timer in my C++ code through setitimer function from sys/time.h. This maps the SIGALRM signal to my timer handler method. After this I am not able to use sleep function. I am assuming it is because sleep uses SIGALRM signal as well. Can you suggest any workaround for this problem?

Thanks for replying.

Answer 1

From the alarm(2) man page:

sleep() may be implemented using SIGALRM; mixing calls to alarm() and sleep() is a bad idea.

Some implementations don't use SIGALRM, find a machine like that and you're set. Otherwise, you can try nanosleep(); it's implemented safely. From the nanosleep(2) man page:

Compared to sleep(3) and usleep(3), nanosleep() has the advantage of not affecting any signals, it is standardized by POSIX, it provides higher timing resolution, and it allows to continue a sleep that has been interrupted by a signal more easily.

Answer 2

I'd use a library that gives an abstraction to these OS services. I use ACE library for timers and sleeps (ACE_OS::sleep, ACE_Reactor::schedule_timeout) and they work together without any problems. As far as I know ACE uses select for its timers. I guess boost::thread::sleep and boost::asio::deadline_timer will accomplish the task successfully as well.

Answer 3

You can try using select() just as a timer. I don't know if it uses SIGALRM or not but it should be simple to test. Something like:

   timeval t = {1, 0};

   select(0, NULL, NULL, NULL, &t);