CS 355 - Systems Programming class notes

Reference: Molay, Understanding Unix/Linux Programming, Chapter 7.7-7.12

Signal handling using signal()

signal() is unreliable when multiple signals arrive at short succession. Possibilities:

Unreliable signals (mousetrap)
SIGY interrupts SIGX handler
SIGX interrupts SIGX handler
Interrupted system calls

Signal handling using sigaction()

int sigaction(int signum, const struct sigaction *action, struct sigaction *prevaction);

signum signal to handle
action pointer to struct describing action
prevaction pointer to struct to receive old action

Critical sections

Data can get corrupted when multiple signals arrive and attempt to modify the same data structure. A section of code is called a critical section if interruptions to that section can result in incomplete or damaged data. A critical section should block signals with sigprocmask() and sigsetops(). A signal handler or any function that can be called when it is already active and not cause any problems is said to be reentrant.

Signals and timers in a video game

Timer driven
Immediate/asynchronous input
State variables