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

NAME

     psignal, pgsignal, gsignal, tdsignal -- post signal to a thread, process, or process group

SYNOPSIS

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

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

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

     void
     gsignal(int pgid, int signum);

     void
     tdsignal(struct thread *td, int signum);

DESCRIPTION

     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 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:

	   o   The target process is sleeping uninterruptibly.	The signal will be noticed when the process returns from the system call or trap.

	   o   The target process is currently ignoring the signal.

	   o   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.

	   o   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 sig-
     nal 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 psignal() as appropriate.  If pgrp is NULL no action is
     taken.

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

SEE ALSO

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

BSD
								  October 8, 2011							       BSD