harvey/sys/src/cmd/aux/watchdog.c

/*
 * This file is part of the UCB release of Plan 9. It is subject to the license
 * terms in the LICENSE file found in the top-level directory of this
 * distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No
 * part of the UCB release of Plan 9, including this file, may be copied,
 * modified, propagated, or distributed except according to the terms contained
 * in the LICENSE file.
 */

#include <u.h>
#include <libc.h>

static int wdog;

int
procctl(int pid)
{
	int ctlfd;
	char *ctl;

	ctl = smprint("/proc/%d/ctl", pid);
	ctlfd = open(ctl, OWRITE);
	if (ctlfd < 0)
		sysfatal("open %s: %r", ctl);
	free(ctl);
	return ctlfd;
}

void
main(int argc, char **argv)
{
	int ctl;

	wdog = open("#w/wdctl", ORDWR);
	if (wdog < 0)
		sysfatal("open #w/wdctl: %r");

	switch(rfork(RFPROC|RFNOWAIT|RFFDG)){
	case 0:
		break;
	default:
		exits(0);
	}

	ctl = procctl(getpid());
	fprint(ctl, "pri 18");
	close(ctl);

	if (fprint(wdog, "enable") < 0)
		sysfatal("write #w/wdctl enable: %r");
	for(;;){
		sleep(300);		/* allows 4.2GHz CPU, with some slop */
		seek(wdog, 0, 0);
		if (fprint(wdog, "restart") < 0)
			sysfatal("write #w/wdctl restart: %r");
	}
}