__pid_affinity() — Add or delete process affinity

Standards

Format

#define  _OPEN_SYS
#include <unistd.h>

int __pid_affinity(int   function_code,
                   pid_t target_pid,
                   pid_t signal_pid,
                   int   signal);

General description

The __pid_affinity() function adds or deletes an entry in a process's affinity list. When a process terminates, each process in its affinity list is notified (sent a signal) of the termination. The __pid_affinity() function provides the ability to dynamically create or break an association between two processes that is similar to the notification mechanism between parent and child processes without the processes being related.

The target_pid identifies the process whose affinity list will be altered.

The signal_pid identifies the process that upon termination of the target_pid will be sent signal signal.

The signal identifies the signal that the signal_pid process will receive when the target_pid process terminates.

Usage notes

1. Either the Target_Pid or Signal_Pid must contain the PID of the caller's process.
2. The __pid affinity service is limited to adding and deleting entries in the caller's affinity list, or adding and deleting entries that contain the caller's PID (Signal_Pid) in other processes affinity list.
3. When the PAF_DELETE_PID# function is specified the Signal is ignored. It is not validated and may contain any value.
4. An entry is only deleted (PAF_DELETE_PID# specified) when the Signal_Pid matches an entry in the Target_Pid process's affinity list.
5. Entries with duplicate PIDs are not allowed in an affinity list. If adding an entry (PAF_ADD_PID# specified) and an entry with a PID that matches the Signal_Pid is found the entry is reused. This may result in the loss of a specific signal.
6. No permission is required when adding the caller's PID to another process's affinity list. All processes have permission to send a signal to themselves (raise()).
7. The PIDs specified by the Target_Pid and Signal_Pid parameters must be greater than 1. Specifying a PID equal to or less than 1 will result in a error.

Returned value

If successful, __pid_affinity() returns 0.

Related information

• unistd.h
• kill() — Send a signal to a process