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kproc, setpri, swiproc, pexit - kernel process creation, priority change, interrupt and termination


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);


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 creating 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 following:

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)).
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.
If set, the new process shares the caller's environment group (currently applies in emu only).
Equivalent to all of the above.

If a particular option is not set, the new process will have a nil reference 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:

The highest priority, used by lock(10.2) for a process entering a critical section
Intended for processes supporting applications with real-time constraints, such as video telephony.
MPEG codec
Audio codec
Any task with keen time constraints.
The priority of most processes in the system.

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 terminating itself. There is no mechanism for one process to force the termination 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 ) Rev:  Thu Feb 15 14:42:59 GMT 2007