Open System Services Programmer's Guide

Types of Signals
Signals are categorized as synchronous, asynchronous, or process level:
• Synchronous signals result from an event that occurs inside a process and are delivered
synchronously with that event. These signals are delivered to current active thread. If current
active thread has not installed the signal handler, then default actions are performed. Signals
in this category are:
4
SIGABRT
SIGFPE
SIGILL
SIGIO
SIGLIMIT
SIGMEMERR
SIGMEMMGR
SIGNOMEM
SIGSEGV
SIGSTK
SIGWINCH
• Asynchronous signals result from an event that is external to the process and are delivered at
any point in the execution of a thread. These signals are delivered to the active threads in
FIFO order. If no active threads have installed a signal handler for the signal, the process-level
actions described in Table 56 (page 316) are performed. Signals in this category are:
SIGINT
SIGPIPE
4
SIGQUIT
SIGTERM
SIGURG
4
SIGUSR1
SIGUSR2
• For process level signals only process level actions can be performed. Signal handlers for
these signals are registered directly to the operating system, so an existing handler for a given
signal is overwritten when a new signal handler is defined for that signal. Signals in this
category are:
SIGABEND (can’t be handled by a user-defined signal handler)
SIGCONT
SIGKILL (can’t be handled by a user-defined signal handler)
SIGSTOP (can’t be handled by a user-defined signal handler)
SIGTSTP (process level action is performed)
SIGTIMEOUT (not supported on G-series RVUs)
SIGTTIN
SIGTTOU
SIGUNCP (supported on H-series RVUs only)
318 Using the Standard POSIX Threads Library