KPROC(9) KPROC(9)
NAME
kproc, pexit, postnote - kernel process creation,
termination and interrupt
SYNOPSIS
void kproc(char *name, void (*func)(void*), void *arg)
void pexit(char *note, int freemem)
void postnote(Proc *p, int dolock, char *n, int flag)
DESCRIPTION
Kproc creates a new kernel process to run the function func,
which is invoked as (*func)(arg). The string name is copied
into the text field of the Proc structure of the new pro-
cess; this value is the name of the kproc in the output of
ps(1). The process is made runnable; it will run when
selected by the scheduler sched(9). The process is created
with base and current priorities set to PriKproc. It shares
the kernel process group and thus name space.
A kernel process terminates only when it calls pexit,
thereby terminating itself. There is no mechanism for one
process to force the termination of another, although it can
send a software interrupt using postnote. Note is a null
string on normal termination, or the cause of If freemem is
non-zero, any memory allocated by the process is discarded;
it should normally be non-zero for any process created by
kproc. Use the following to terminate a kernel process nor-
mally:
pexit("", 1);
to terminate a kernel process normally.
Postnote sends a software interrupt to process p, causing
it, if necessary, to wake from sleep(9) or break out of a
rendezvous(2), with an error(9) `interrupted'. Up to NNOTE
notes can be pending at once (currently 5); if more than
that arrive, the process is forced out of sleep and
rendezvous, but the message itself is discarded. Postnote
returns non-zero iff the note has been delivered success-
fully. If dolock is non-zero, postnote synchronises deliv-
ery of the note with the debugger and other operations of
proc(3). Flag is zero, or one of the following
NDebug
Print the note message on the user's standard error.
Furthermore, suspend the process in a Broken state,
preserving its memory, for later debugging.
KPROC(9) KPROC(9)
NExit
Deliver the note quietly.
NUser
The note comes from another process, not the system.
The kernel uses postnote to signal processes that commit
grave faults, and to implement the note and kill functions
of proc(3). A device driver should use postnote only to tell
a service process, previously started by the driver using
kproc , that it should stop; the note will cause that pro-
cess to raise an error(9). For example, a process started to
read packets from a network device could be stopped as fol-
lows when the interface is unbound:
postnote(readp, 1, "unbind", 0);
where readp points to the appropriate Proc. The text of the
message is typically irrelevant.
SOURCE
/sys/src/9/port/proc.c