The Often-Forgotten EINTR

• What they do NOT teach in "Intro To OS 101", is that system calls are sometimes aborted prematurely if the process running them received a signal.
• In this case, the system call will return an error (-1), with errno set to EINTR.
• If we don't handle these cases properly, we will either think we had a "real" error and abort the program, or we will not handle the premature awakening at all and start having a negative time-drift (or, time flowing faster then it should).

Originally written by guy keren