PSIGNAL(9) | Kernel Developer's Manual | PSIGNAL(9)

# NAME

`psignal`, `pgsignal`, `pgsigio` — post signal to a process

# SYNOPSIS

void
`psignal`(struct proc *p, int signum);

void
`pgsignal`(struct pgrp *pgrp, int signum, int checkctty);

void
`pgsigio`(struct sigio_ref *sir, int sigum, int checkctty);

# DESCRIPTION

These functions post a signal to one or more processes. The argument signum common to all three functions should be in the range [1-`NSIG`].

The `psignal`() function posts signal number signum to the process represented by the process structure p. With a few exceptions noted below, the target process signal disposition is updated and is marked as runnable, so further handling of the signal is done in the context of the target process after a context switch. Note that `psignal`() does not by itself cause a context switch to happen.

The target process is not marked as runnable in the following cases:

- The target process is sleeping uninterruptibly. The signal will be noticed when the process returns from the system call or trap.
- The target process is currently ignoring the signal.
- If a stop signal is sent to a sleeping process that takes the default action (see sigaction(2)), the process is stopped without awakening it.
- `SIGCONT` restarts a stopped process (or puts them back to sleep) regardless of the signal action (e.g., blocked or ignored).

If the target process is being traced, `psignal`() behaves as if the target process were taking the default action for signum. This allows the tracing process to be notified of the signal.

The `pgsignal`() function posts signal number signum to each member of the process group described by pgrp. If checkctty is non-zero, the signal will be posted only to processes that have a controlling terminal. If pgrp is `NULL`, no action is taken.

The `pgsigio`() function posts signal number signum to the process or each member of the process group indicated by reference sir. If checkctty is non-zero, the signal will be posted only to processes that have a controlling terminal.

# CODE REFERENCES

These functions are implemented in the file sys/kern/kern_sig.c.

# SEE ALSO

sigaction(2), sigio_setown(9), tsleep(9)

March 31, 2022 | Debian