ref: 8a788aea84aad3bfbd5b39d78c1925654f3b9e14
dir: purgatorio/man/10/kproc
.TH KPROC 10.2
.SH NAME
kproc, setpri, swiproc, pexit \- kernel process creation, priority change, interrupt and termination
.SH SYNOPSIS
.ta \w'\fLchar* 'u
.B
void kproc(char *name, void (*func)(void*), void *arg, int flags);
.PP
.B
int setpri(int pri);
.PP
.B
void swiproc(Proc *p, int interp);
.PP
.B
void pexit(char*, int);
.SH DESCRIPTION
.I Kproc
creates a new Inferno kernel process
to run the function
.IR func ,
which is invoked as
.BR "(*func)(arg)" .
The string
.I name
is copied into the
.B text
field of the
.B Proc
structure of the new process; although the value is not visible to Limbo
applications, it can appear in system messages written to the console.
The process is made runnable; it
will run when selected by the scheduler.
.PP
The new process always acquires the following attributes from the creating process:
.IP
owner (Inferno user name)
.br
host user and group IDs (in
.I emu
only)
.br
floating-point attributes
.PP
Several resources can be shared with the creating process on request, as determined by
.IR flags ,
which is the logical OR
of a subset of the following:
.TF KPDUPENVG
.TP
.B KPDUPPG
If set, the new process shares the caller's process group,
which includes its process group ID
(for
.IR killgrp ),
name space (mounts, root and current directory),
and PIN for
.B /dev/pin
(see
.IR cons (3)).
.TP
.B KPDUPFDG
If set, the new process shares the caller's file descriptor group;
otherwise, it has no file descriptor group, and (if it intends to open files) must call
.IR newfgrp (10.2)
to obtain an empty file descriptor group.
.TP
.B KPDUPENVG
If set, the new process shares the caller's environment group
(currently applies in
.I emu
only).
.TP
.B KPDUP
Equivalent to all of the above.
.PD
.PP
If a particular option is not set, the new process will have a
.B nil
reference for the corresponding resource.
.PP
.I Setpri
sets the priority of the calling process to
.I pri
and returns its previous priority level.
If a (now) higher priority process is ready to run, the system will reschedule.
The available priority levels are shown below,
arranged from highest to lowest priority,
with examples of the type of processes intended to use them:
.TF PriBackground
.TP
.B PriLock
The highest priority, used by
.IR lock (10.2)
for a process entering a critical section
.TP
.B PriRealtime
Intended for processes supporting applications with real-time constraints, such as video telephony.
.TP
.B PriHicodec
MPEG codec
.TP
.B PriLocodec
Audio codec
.TP
.B PriHi
Any task with keen time constraints.
.TP
.B PriNormal
The priority of most processes in the system.
.TP
.B PriLo
.TP
.B PriBackground
.PD
.PP
.I Swiproc
sends a software interrupt to process
.IR p ,
causing it to wake from
.IR sleep (10.2)
with an
.IR error (10.2)
`interrupted'.
Unless
.I interp
is non-zero (ie, the Dis interpreter is the caller), the process is also marked `killed'.
.PP
An Inferno process terminates only when it calls
.IR 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
.IR swiproc .
The arguments to
.I pexit
are ignored in Inferno, but are included for compatibility
with kernel components of Plan 9; use
.IP
.EX
pexit("", 0);
.EE