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Terminal (work station) activity
Calling an API such as the X/Open kill() function, the American National
Standard C raise() function, or the ILE CEESGL (signal a condition) function.
The signal action vector is a list of signal-handling actions for each defined signal.
The signal action vector is maintained separately for each process and is inherited
from the parent process. The signal action vector specifies the signal-handling
actions for both synchronously and asynchronously generated signals.
A signal is said to be delivered to a process when the specified signal-handling
action for the signal is taken.
The following describes some of the support provided by OS/400 signal manage-
ment. The set of defined signals is determined by the system. The system speci-
fies the attributes for each defined signal. These attributes consist of a signal
number, the initial signal action, and the signal default action. The system also
specifies an initial signal blocking mask. The set of defined signals, the signal attri-
butes, and signal blocking mask are referred to as signal controls.
A signal can be generated or delivered only to a process that has expressed an
interest in signals. An error condition results under the following conditions:
An attempt is made to generate a signal when the system signal controls have
not been initialized.
An attempt is made to generate a signal for a process that has not been
enabled for signals.
A process can express an interest in signals by calling the Qp0sEnableSignals()
API. In addition, calling particular signal APIs implicitly enables the process for
signals.
If the process has not been enabled for signals, the process signal controls are set
from signal controls established by the system during IPL (the system signal con-
trols). An error condition results if an attempt is made to enable signals for the
process before the system signal controls have been initialized.
Once the process signal controls have been initialized, the user is permitted to
change the signal controls for the process.
The attributes for each defined signal are stored in an object called a signal
monitor. The system supports a maximum of 63 signal monitors for each process.
The process signal action vector is a list of signal monitors, one for each defined
signal. The signal monitor contains, but is not limited to, the following information:
Signal action
Signal default action
Signal options
The signal action defines the action to be taken by the system when a process
receives an unblocked signal. The user can change the signal action for a process
signal monitor.
The signal default action field defines the action to be taken by the system when
the signal action is set to
handle using signal default action
. The signal default
action for a signal monitor is set in the system signal controls and cannot be
changed for a process signal monitor.
8-24 System API Programming V4R1