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

     psignal, kern_psignal, pgsignal, gsignal, tdsignal — post 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

     The kern_psignal() function posts signal number signum to the process
     represented by the process structure p.  The kern_psignal() function used
     to be called psignal() 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.

           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 kern_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.  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 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.

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

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

BSD                              October 8, 2011                             BSD