KPROC(10.2) KPROC(10.2)
NAME
kproc, setpri, swiproc, pexit - kernel process creation, priority
change, interrupt and termination
SYNOPSIS
void kproc(char *name, void (*func)(void*), void *arg, int flags);
int setpri(int pri);
void swiproc(Proc *p, int interp);
void pexit(char*, int);
DESCRIPTION
Kproc creates a new Inferno 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 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.
The new process always acquires the following attributes from the cre‐
ating process:
owner (Inferno user name)
host user and group IDs (in emu only)
floating-point attributes
Several resources can be shared with the creating process on request,
as determined by flags, which is the logical OR of a subset of the fol‐
lowing:
KPDUPPG
If set, the new process shares the caller's process group, which
includes its process group ID (for killgrp), name space (mounts,
root and current directory), and PIN for /dev/pin (see cons(3)).
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 newfgrp(10.2) to obtain an
empty file descriptor group.
KPDUPENVG
If set, the new process shares the caller's environment group
(currently applies in emu only).
KPDUP Equivalent to all of the above.
If a particular option is not set, the new process will have a nil ref‐
erence for the corresponding resource.
Setpri sets the priority of the calling process to 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:
PriLock
The highest priority, used by lock(10.2) for a process entering
a critical section
PriRealtime
Intended for processes supporting applications with real-time
constraints, such as video telephony.
PriHicodec
MPEG codec
PriLocodec
Audio codec
PriHi Any task with keen time constraints.
PriNormal
The priority of most processes in the system.
PriLo
PriBackground
Swiproc sends a software interrupt to process p, causing it to wake
from sleep(10.2) with an error(10.2) `interrupted'. Unless interp is
non-zero (ie, the Dis interpreter is the caller), the process is also
marked `killed'.
An Inferno process terminates only when it calls pexit, thereby termi‐
nating itself. There is no mechanism for one process to force the ter‐
mination of another, although it can send a software interrupt using
swiproc. The arguments to pexit are ignored in Inferno, but are
included for compatibility with kernel components of Plan 9; use
pexit("", 0);
KPROC(10.2)
