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


psignal, kern_psignal, pgsignal, gsignal, tdsignalpost signal to a thread, process, or process group


#include <sys/types.h>
#include <sys/signalvar.h>

kern_psignal(struct proc *p, int signum);

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

gsignal(int pgid, int signum);

tdsignal(struct thread *td, int signum);


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

The () function posts signal number signum to the process represented by the process structure p. The kern_psignal() function used to be called () but was renamed in order to eliminate a name collision with the libc function of that name and facilitate code reuse. 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 kern_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.
  • 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 () 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 () 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. pgsignal() is implemented by walking along the process list headed by the field pg_members of the process group structure pointed at by pgrp and calling kern_psignal() as appropriate. If pgrp is NULL no action is taken.

The () function posts signal number signum to each member of the process group identified by the group id pgid. gsignal() first finds the group structure associated with pgid, then invokes pgsignal() with the argument checkctty set to zero. If pgid is zero no action is taken.

The () function posts signal number signum to the thread represented by the thread structure td.


sigaction(2), signal(9), tsleep(9)


The psignal() function was renamed to kern_psignal() in FreeBSD 9.0.

October 8, 2011 Debian