Videos: Signals

Signals are the way that the operating system and other processes send alerts or requests to a process (to complement system calls, which are the way that a process makes requests to operating system).

• Signals 1: Polling with WNOHANG   1:14
  Polling with waitpid and WNOHANG as a step toward motivating signals.

• Signals 2: Introduction to signals   4:35
  Introduction to handling and sending signals

• Signals 3: SIGCHLD example   1:12
  Example program that handles SIGCHLD.

• Signals 4: Process signal state   2:39
  Details on signal properties and the signal state that must be kept for each process.

• Signals 5: Changing the signal mask   3:48
  Using sigprocmask to change the set of signals that are blocked for a process.

• Signals 6: Signal-handling effects and volatile   3:39
  Communication from a signal handler requires a kind of synchronization with the main program that can be implemented with volatile.

• Signals 7: Signal handling as concurrency   4:02
  Another example of how signal handling is a form of concurrency, and how blocking signals can synchronize interactions.

• Signals 8: Async-signal-safe   2:08
  Only async-signal-safe functions can be called safely from a signal handler.

• Signals 9: Signal handling and errno   2:02
  Signals handlers can interfere with errno, so handlers should save and restore it.

• Signals 10: Guidelines for safe signal handlers   0:56
  Summary of rules to follow to make your signal handlers work correctly.

• Signals 11: Waiting for a signal with sigsuspend   5:14
  Using sigsuspend to wait for a signal, and why using sleep instead doesn’t work.

• Signals 12: Stopped processes   3:32
  Stopping and continuing processes with SIGSTOP and SIGCONT.

• Signals 13: Process groups   4:13
  Process groups and the way that they interact with signals, especially as sent by a shell.