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psignal, pgsignal, gsignal -- post signal to a process or process group
psignal(struct proc *p, int signum);
pgsignal(struct pgrp *pgrp, int signum, int checkctty);
gsignal(int pgid, int signum);
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:
+o The target process is sleeping uninterruptibly. The signal
will be noticed when the process returns from the system call
+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 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 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.
sigaction(2), signal(9), tsleep(9)