Signals

• Triggered by the kernel (possibly via system calls) and handled by individual processes
• Software interrupts
• Using as syscall
  1. Kernel receives signal via system call
  2. System call flags that process, indicating there is a signal pending
  3. When the time comes for the process to run, instead of running, the signal is dealt with
• If there is no registered handler assigned to that signal, the target process is terminated
• Example
  • SIGILL: Illegal Instruction (from kernel)
  • SIGSEGV: Segmentation Fault (from kernel)
  • SIGTERM: Polite kill (from syscall)
  • SIGKILL: (from syscall)