xref: /freebsd/sys/kern/kern_shutdown.c (revision c17d43407fe04133a94055b0dbc7ea8965654a9f)
1 /*-
2  * Copyright (c) 1986, 1988, 1991, 1993
3  *	The Regents of the University of California.  All rights reserved.
4  * (c) UNIX System Laboratories, Inc.
5  * All or some portions of this file are derived from material licensed
6  * to the University of California by American Telephone and Telegraph
7  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
8  * the permission of UNIX System Laboratories, Inc.
9  *
10  * Redistribution and use in source and binary forms, with or without
11  * modification, are permitted provided that the following conditions
12  * are met:
13  * 1. Redistributions of source code must retain the above copyright
14  *    notice, this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in the
17  *    documentation and/or other materials provided with the distribution.
18  * 3. All advertising materials mentioning features or use of this software
19  *    must display the following acknowledgement:
20  *	This product includes software developed by the University of
21  *	California, Berkeley and its contributors.
22  * 4. Neither the name of the University nor the names of its contributors
23  *    may be used to endorse or promote products derived from this software
24  *    without specific prior written permission.
25  *
26  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36  * SUCH DAMAGE.
37  *
38  *	@(#)kern_shutdown.c	8.3 (Berkeley) 1/21/94
39  * $FreeBSD$
40  */
41 
42 #include "opt_ddb.h"
43 #include "opt_hw_wdog.h"
44 #include "opt_panic.h"
45 #include "opt_show_busybufs.h"
46 
47 #include <sys/param.h>
48 #include <sys/systm.h>
49 #include <sys/bio.h>
50 #include <sys/buf.h>
51 #include <sys/conf.h>
52 #include <sys/cons.h>
53 #include <sys/disklabel.h>
54 #include <sys/eventhandler.h>
55 #include <sys/kernel.h>
56 #include <sys/kthread.h>
57 #include <sys/malloc.h>
58 #include <sys/mount.h>
59 #include <sys/proc.h>
60 #include <sys/reboot.h>
61 #include <sys/resourcevar.h>
62 #include <sys/smp.h>		/* smp_active */
63 #include <sys/sysctl.h>
64 #include <sys/sysproto.h>
65 #include <sys/vnode.h>
66 
67 #include <machine/pcb.h>
68 #include <machine/md_var.h>
69 #include <machine/smp.h>
70 
71 #include <sys/signalvar.h>
72 #ifdef DDB
73 #include <ddb/ddb.h>
74 #endif
75 
76 #ifndef PANIC_REBOOT_WAIT_TIME
77 #define PANIC_REBOOT_WAIT_TIME 15 /* default to 15 seconds */
78 #endif
79 
80 /*
81  * Note that stdarg.h and the ANSI style va_start macro is used for both
82  * ANSI and traditional C compilers.
83  */
84 #include <machine/stdarg.h>
85 
86 #ifdef DDB
87 #ifdef DDB_UNATTENDED
88 int debugger_on_panic = 0;
89 #else
90 int debugger_on_panic = 1;
91 #endif
92 SYSCTL_INT(_debug, OID_AUTO, debugger_on_panic, CTLFLAG_RW,
93 	&debugger_on_panic, 0, "Run debugger on kernel panic");
94 #endif
95 
96 int sync_on_panic = 1;
97 SYSCTL_INT(_kern, OID_AUTO, sync_on_panic, CTLFLAG_RW,
98 	&sync_on_panic, 0, "Do a sync before rebooting from a panic");
99 
100 SYSCTL_NODE(_kern, OID_AUTO, shutdown, CTLFLAG_RW, 0, "Shutdown environment");
101 
102 #ifdef	HW_WDOG
103 /*
104  * If there is a hardware watchdog, point this at the function needed to
105  * hold it off.
106  * It's needed when the kernel needs to do some lengthy operations.
107  * e.g. in wd.c when dumping core.. It's most annoying to have
108  * your precious core-dump only half written because the wdog kicked in.
109  */
110 watchdog_tickle_fn wdog_tickler = NULL;
111 #endif	/* HW_WDOG */
112 
113 /*
114  * Variable panicstr contains argument to first call to panic; used as flag
115  * to indicate that the kernel has already called panic.
116  */
117 const char *panicstr;
118 
119 int dumping;				 /* system is dumping */
120 
121 static void boot(int) __dead2;
122 static void dumpsys(void);
123 static void poweroff_wait(void *, int);
124 static void shutdown_halt(void *junk, int howto);
125 static void shutdown_panic(void *junk, int howto);
126 static void shutdown_reset(void *junk, int howto);
127 
128 /* register various local shutdown events */
129 static void
130 shutdown_conf(void *unused)
131 {
132 	EVENTHANDLER_REGISTER(shutdown_final, poweroff_wait, NULL, SHUTDOWN_PRI_FIRST);
133 	EVENTHANDLER_REGISTER(shutdown_final, shutdown_halt, NULL, SHUTDOWN_PRI_LAST + 100);
134 	EVENTHANDLER_REGISTER(shutdown_final, shutdown_panic, NULL, SHUTDOWN_PRI_LAST + 100);
135 	EVENTHANDLER_REGISTER(shutdown_final, shutdown_reset, NULL, SHUTDOWN_PRI_LAST + 200);
136 }
137 
138 SYSINIT(shutdown_conf, SI_SUB_INTRINSIC, SI_ORDER_ANY, shutdown_conf, NULL)
139 
140 /*
141  * The system call that results in a reboot
142  *
143  * MPSAFE
144  */
145 /* ARGSUSED */
146 int
147 reboot(struct thread *td, struct reboot_args *uap)
148 {
149 	int error;
150 
151 	mtx_lock(&Giant);
152 	if ((error = suser_td(td)) == 0)
153 		boot(uap->opt);
154 	mtx_unlock(&Giant);
155 	return (error);
156 }
157 
158 /*
159  * Called by events that want to shut down.. e.g  <CTL><ALT><DEL> on a PC
160  */
161 static int shutdown_howto = 0;
162 
163 void
164 shutdown_nice(int howto)
165 {
166 	shutdown_howto = howto;
167 
168 	/* Send a signal to init(8) and have it shutdown the world */
169 	if (initproc != NULL) {
170 		PROC_LOCK(initproc);
171 		psignal(initproc, SIGINT);
172 		PROC_UNLOCK(initproc);
173 	} else {
174 		/* No init(8) running, so simply reboot */
175 		boot(RB_NOSYNC);
176 	}
177 	return;
178 }
179 static int	waittime = -1;
180 static struct pcb dumppcb;
181 
182 static void
183 print_uptime(void)
184 {
185 	int f;
186 	struct timespec ts;
187 
188 	getnanouptime(&ts);
189 	printf("Uptime: ");
190 	f = 0;
191 	if (ts.tv_sec >= 86400) {
192 		printf("%ldd", (long)ts.tv_sec / 86400);
193 		ts.tv_sec %= 86400;
194 		f = 1;
195 	}
196 	if (f || ts.tv_sec >= 3600) {
197 		printf("%ldh", (long)ts.tv_sec / 3600);
198 		ts.tv_sec %= 3600;
199 		f = 1;
200 	}
201 	if (f || ts.tv_sec >= 60) {
202 		printf("%ldm", (long)ts.tv_sec / 60);
203 		ts.tv_sec %= 60;
204 		f = 1;
205 	}
206 	printf("%lds\n", (long)ts.tv_sec);
207 }
208 
209 /*
210  *  Go through the rigmarole of shutting down..
211  * this used to be in machdep.c but I'll be dammned if I could see
212  * anything machine dependant in it.
213  */
214 static void
215 boot(int howto)
216 {
217 
218 	/* collect extra flags that shutdown_nice might have set */
219 	howto |= shutdown_howto;
220 
221 #ifdef DDB
222 	/* We are out of the debugger now. */
223 	db_active = 0;
224 #endif
225 
226 #ifdef SMP
227 	if (smp_active)
228 		printf("boot() called on cpu#%d\n", PCPU_GET(cpuid));
229 #endif
230 	/*
231 	 * Do any callouts that should be done BEFORE syncing the filesystems.
232 	 */
233 	EVENTHANDLER_INVOKE(shutdown_pre_sync, howto);
234 
235 	/*
236 	 * Now sync filesystems
237 	 */
238 	if (!cold && (howto & RB_NOSYNC) == 0 && waittime < 0) {
239 		register struct buf *bp;
240 		int iter, nbusy, pbusy;
241 		int subiter;
242 
243 		waittime = 0;
244 		printf("\nsyncing disks... ");
245 
246 		sync(&thread0, NULL);
247 
248 		/*
249 		 * With soft updates, some buffers that are
250 		 * written will be remarked as dirty until other
251 		 * buffers are written.
252 		 */
253 		for (iter = pbusy = 0; iter < 20; iter++) {
254 			nbusy = 0;
255 			for (bp = &buf[nbuf]; --bp >= buf; ) {
256 				if ((bp->b_flags & B_INVAL) == 0 &&
257 				    BUF_REFCNT(bp) > 0) {
258 					nbusy++;
259 				} else if ((bp->b_flags & (B_DELWRI | B_INVAL))
260 						== B_DELWRI) {
261 					/* bawrite(bp);*/
262 					nbusy++;
263 				}
264 			}
265 			if (nbusy == 0)
266 				break;
267 			printf("%d ", nbusy);
268 			if (nbusy < pbusy)
269 				iter = 0;
270 			pbusy = nbusy;
271 			sync(&thread0, NULL);
272  			if (curthread != NULL) {
273 				DROP_GIANT();
274    				for (subiter = 0; subiter < 50 * iter; subiter++) {
275      					mtx_lock_spin(&sched_lock);
276 					setrunqueue(curthread);
277 					curthread->td_proc->p_stats->p_ru.ru_nvcsw++;
278      					mi_switch(); /* Allow interrupt threads to run */
279      					mtx_unlock_spin(&sched_lock);
280      					DELAY(1000);
281    				}
282 				PICKUP_GIANT();
283  			} else
284 			DELAY(50000 * iter);
285 		}
286 		printf("\n");
287 		/*
288 		 * Count only busy local buffers to prevent forcing
289 		 * a fsck if we're just a client of a wedged NFS server
290 		 */
291 		nbusy = 0;
292 		for (bp = &buf[nbuf]; --bp >= buf; ) {
293 			if (((bp->b_flags&B_INVAL) == 0 && BUF_REFCNT(bp)) ||
294 			    ((bp->b_flags & (B_DELWRI|B_INVAL)) == B_DELWRI)) {
295 				if (bp->b_dev == NODEV) {
296 					TAILQ_REMOVE(&mountlist,
297 					    bp->b_vp->v_mount, mnt_list);
298 					continue;
299 				}
300 				nbusy++;
301 #if defined(SHOW_BUSYBUFS) || defined(DIAGNOSTIC)
302 				printf(
303 			    "%d: dev:%s, flags:%08lx, blkno:%ld, lblkno:%ld\n",
304 				    nbusy, devtoname(bp->b_dev),
305 				    bp->b_flags, (long)bp->b_blkno,
306 				    (long)bp->b_lblkno);
307 #endif
308 			}
309 		}
310 		if (nbusy) {
311 			/*
312 			 * Failed to sync all blocks. Indicate this and don't
313 			 * unmount filesystems (thus forcing an fsck on reboot).
314 			 */
315 			printf("giving up on %d buffers\n", nbusy);
316 			DELAY(5000000);	/* 5 seconds */
317 		} else {
318 			printf("done\n");
319 			/*
320 			 * Unmount filesystems
321 			 */
322 			if (panicstr == 0)
323 				vfs_unmountall();
324 		}
325 		DELAY(100000);		/* wait for console output to finish */
326 	}
327 
328 	print_uptime();
329 
330 	/*
331 	 * Ok, now do things that assume all filesystem activity has
332 	 * been completed.
333 	 */
334 	EVENTHANDLER_INVOKE(shutdown_post_sync, howto);
335 	splhigh();
336 	if ((howto & (RB_HALT|RB_DUMP)) == RB_DUMP && !cold)
337 		dumpsys();
338 
339 	/* Now that we're going to really halt the system... */
340 	EVENTHANDLER_INVOKE(shutdown_final, howto);
341 
342 	for(;;) ;	/* safety against shutdown_reset not working */
343 	/* NOTREACHED */
344 }
345 
346 /*
347  * If the shutdown was a clean halt, behave accordingly.
348  */
349 static void
350 shutdown_halt(void *junk, int howto)
351 {
352 	if (howto & RB_HALT) {
353 		printf("\n");
354 		printf("The operating system has halted.\n");
355 		printf("Please press any key to reboot.\n\n");
356 		switch (cngetc()) {
357 		case -1:		/* No console, just die */
358 			cpu_halt();
359 			/* NOTREACHED */
360 		default:
361 			howto &= ~RB_HALT;
362 			break;
363 		}
364 	}
365 }
366 
367 /*
368  * Check to see if the system paniced, pause and then reboot
369  * according to the specified delay.
370  */
371 static void
372 shutdown_panic(void *junk, int howto)
373 {
374 	int loop;
375 
376 	if (howto & RB_DUMP) {
377 		if (PANIC_REBOOT_WAIT_TIME != 0) {
378 			if (PANIC_REBOOT_WAIT_TIME != -1) {
379 				printf("Automatic reboot in %d seconds - "
380 				       "press a key on the console to abort\n",
381 					PANIC_REBOOT_WAIT_TIME);
382 				for (loop = PANIC_REBOOT_WAIT_TIME * 10;
383 				     loop > 0; --loop) {
384 					DELAY(1000 * 100); /* 1/10th second */
385 					/* Did user type a key? */
386 					if (cncheckc() != -1)
387 						break;
388 				}
389 				if (!loop)
390 					return;
391 			}
392 		} else { /* zero time specified - reboot NOW */
393 			return;
394 		}
395 		printf("--> Press a key on the console to reboot,\n");
396 		printf("--> or switch off the system now.\n");
397 		cngetc();
398 	}
399 }
400 
401 /*
402  * Everything done, now reset
403  */
404 static void
405 shutdown_reset(void *junk, int howto)
406 {
407 	printf("Rebooting...\n");
408 	DELAY(1000000);	/* wait 1 sec for printf's to complete and be read */
409 	/* cpu_boot(howto); */ /* doesn't do anything at the moment */
410 	cpu_reset();
411 	/* NOTREACHED */ /* assuming reset worked */
412 }
413 
414 /*
415  * Magic number for savecore
416  *
417  * exported (symorder) and used at least by savecore(8)
418  *
419  */
420 static u_long const	dumpmag = 0x8fca0101UL;
421 
422 static int	dumpsize = 0;		/* also for savecore */
423 
424 static int	dodump = 1;
425 
426 SYSCTL_INT(_machdep, OID_AUTO, do_dump, CTLFLAG_RW, &dodump, 0,
427     "Try to perform coredump on kernel panic");
428 
429 static int
430 setdumpdev(dev_t dev)
431 {
432 	int psize;
433 	long newdumplo;
434 
435 	if (dev == NODEV) {
436 		dumpdev = dev;
437 		return (0);
438 	}
439 	if (devsw(dev) == NULL)
440 		return (ENXIO);		/* XXX is this right? */
441 	if (devsw(dev)->d_psize == NULL)
442 		return (ENXIO);		/* XXX should be ENODEV ? */
443 	psize = devsw(dev)->d_psize(dev);
444 	if (psize == -1)
445 		return (ENXIO);		/* XXX should be ENODEV ? */
446 	/*
447 	 * XXX should clean up checking in dumpsys() to be more like this.
448 	 */
449 	newdumplo = psize - Maxmem * (PAGE_SIZE / DEV_BSIZE);
450 	if (newdumplo <= LABELSECTOR)
451 		return (ENOSPC);
452 	dumpdev = dev;
453 	dumplo = newdumplo;
454 	return (0);
455 }
456 
457 
458 /* ARGSUSED */
459 static void
460 dump_conf(void *dummy)
461 {
462 	char *path;
463 	dev_t dev;
464 
465 	path = malloc(MNAMELEN, M_TEMP, M_WAITOK);
466 	if (TUNABLE_STR_FETCH("dumpdev", path, MNAMELEN) != 0) {
467 		dev = getdiskbyname(path);
468 		if (dev != NODEV)
469 			dumpdev = dev;
470 	}
471 	free(path, M_TEMP);
472 	if (setdumpdev(dumpdev) != 0)
473 		dumpdev = NODEV;
474 }
475 
476 SYSINIT(dump_conf, SI_SUB_DUMP_CONF, SI_ORDER_FIRST, dump_conf, NULL)
477 
478 static int
479 sysctl_kern_dumpdev(SYSCTL_HANDLER_ARGS)
480 {
481 	int error;
482 	udev_t ndumpdev;
483 
484 	ndumpdev = dev2udev(dumpdev);
485 	error = sysctl_handle_opaque(oidp, &ndumpdev, sizeof ndumpdev, req);
486 	if (error == 0 && req->newptr != NULL)
487 		error = setdumpdev(udev2dev(ndumpdev, 0));
488 	return (error);
489 }
490 
491 SYSCTL_PROC(_kern, KERN_DUMPDEV, dumpdev, CTLTYPE_OPAQUE|CTLFLAG_RW,
492 	0, sizeof dumpdev, sysctl_kern_dumpdev, "T,dev_t", "");
493 
494 /*
495  * Doadump comes here after turning off memory management and
496  * getting on the dump stack, either when called above, or by
497  * the auto-restart code.
498  */
499 static void
500 dumpsys(void)
501 {
502 	int	error;
503 
504 	savectx(&dumppcb);
505 	if (!dodump)
506 		return;
507 	if (dumpdev == NODEV)
508 		return;
509 	if (!(devsw(dumpdev)))
510 		return;
511 	if (!(devsw(dumpdev)->d_dump))
512 		return;
513 	if (dumping++) {
514 		dumping--;
515 		printf("Dump already in progress, bailing...\n");
516 		return;
517 	}
518 	dumpsize = Maxmem;
519 	printf("\ndumping to dev %s, offset %ld\n", devtoname(dumpdev), dumplo);
520 	printf("dump ");
521 	error = (*devsw(dumpdev)->d_dump)(dumpdev);
522 	dumping--;
523 	if (error == 0) {
524 		printf("succeeded\n");
525 		return;
526 	}
527 	printf("failed, reason: ");
528 	switch (error) {
529 	case ENODEV:
530 		printf("device doesn't support a dump routine\n");
531 		break;
532 
533 	case ENXIO:
534 		printf("device bad\n");
535 		break;
536 
537 	case EFAULT:
538 		printf("device not ready\n");
539 		break;
540 
541 	case EINVAL:
542 		printf("area improper\n");
543 		break;
544 
545 	case EIO:
546 		printf("i/o error\n");
547 		break;
548 
549 	case EINTR:
550 		printf("aborted from console\n");
551 		break;
552 
553 	default:
554 		printf("unknown, error = %d\n", error);
555 		break;
556 	}
557 }
558 
559 int
560 dumpstatus(vm_offset_t addr, off_t count)
561 {
562 	int c;
563 
564 	if (addr % (1024 * 1024) == 0) {
565 #ifdef HW_WDOG
566 		if (wdog_tickler)
567 			(*wdog_tickler)();
568 #endif
569 		printf("%ld ", (long)(count / (1024 * 1024)));
570 	}
571 
572 	if ((c = cncheckc()) == 0x03)
573 		return -1;
574 	else if (c != -1)
575 		printf("[CTRL-C to abort] ");
576 
577 	return 0;
578 }
579 
580 #ifdef SMP
581 static u_int panic_cpu = NOCPU;
582 #endif
583 
584 /*
585  * Panic is called on unresolvable fatal errors.  It prints "panic: mesg",
586  * and then reboots.  If we are called twice, then we avoid trying to sync
587  * the disks as this often leads to recursive panics.
588  *
589  * MPSAFE
590  */
591 void
592 panic(const char *fmt, ...)
593 {
594 	int bootopt;
595 	va_list ap;
596 	static char buf[256];
597 
598 #ifdef SMP
599 	/*
600 	 * We don't want multiple CPU's to panic at the same time, so we
601 	 * use panic_cpu as a simple spinlock.  We have to keep checking
602 	 * panic_cpu if we are spinning in case the panic on the first
603 	 * CPU is canceled.
604 	 */
605 	if (panic_cpu != PCPU_GET(cpuid))
606 		while (atomic_cmpset_int(&panic_cpu, NOCPU,
607 		    PCPU_GET(cpuid)) == 0)
608 			while (panic_cpu != NOCPU)
609 				; /* nothing */
610 #endif
611 
612 	bootopt = RB_AUTOBOOT | RB_DUMP;
613 	if (panicstr)
614 		bootopt |= RB_NOSYNC;
615 	else
616 		panicstr = fmt;
617 
618 	va_start(ap, fmt);
619 	(void)vsnprintf(buf, sizeof(buf), fmt, ap);
620 	if (panicstr == fmt)
621 		panicstr = buf;
622 	va_end(ap);
623 	printf("panic: %s\n", buf);
624 #ifdef SMP
625 	/* two separate prints in case of an unmapped page and trap */
626 	printf("cpuid = %d; ", PCPU_GET(cpuid));
627 #ifdef APIC_IO
628 	printf("lapic.id = %08x\n", lapic.id);
629 #endif
630 #endif
631 
632 #if defined(DDB)
633 	if (debugger_on_panic)
634 		Debugger ("panic");
635 #ifdef RESTARTABLE_PANICS
636 	/* See if the user aborted the panic, in which case we continue. */
637 	if (panicstr == NULL) {
638 #ifdef SMP
639 		atomic_store_rel_int(&panic_cpu, NOCPU);
640 #endif
641 		return;
642 	}
643 #endif
644 #endif
645 	if (!sync_on_panic)
646 		bootopt |= RB_NOSYNC;
647 	boot(bootopt);
648 }
649 
650 /*
651  * Support for poweroff delay.
652  */
653 #ifndef POWEROFF_DELAY
654 # define POWEROFF_DELAY 5000
655 #endif
656 static int poweroff_delay = POWEROFF_DELAY;
657 
658 SYSCTL_INT(_kern_shutdown, OID_AUTO, poweroff_delay, CTLFLAG_RW,
659 	&poweroff_delay, 0, "");
660 
661 static void
662 poweroff_wait(void *junk, int howto)
663 {
664 	if(!(howto & RB_POWEROFF) || poweroff_delay <= 0)
665 		return;
666 	DELAY(poweroff_delay * 1000);
667 }
668 
669 /*
670  * Some system processes (e.g. syncer) need to be stopped at appropriate
671  * points in their main loops prior to a system shutdown, so that they
672  * won't interfere with the shutdown process (e.g. by holding a disk buf
673  * to cause sync to fail).  For each of these system processes, register
674  * shutdown_kproc() as a handler for one of shutdown events.
675  */
676 static int kproc_shutdown_wait = 60;
677 SYSCTL_INT(_kern_shutdown, OID_AUTO, kproc_shutdown_wait, CTLFLAG_RW,
678     &kproc_shutdown_wait, 0, "");
679 
680 void
681 kproc_shutdown(void *arg, int howto)
682 {
683 	struct proc *p;
684 	int error;
685 
686 	if (panicstr)
687 		return;
688 
689 	p = (struct proc *)arg;
690 	printf("Waiting (max %d seconds) for system process `%s' to stop...",
691 	    kproc_shutdown_wait, p->p_comm);
692 	error = kthread_suspend(p, kproc_shutdown_wait * hz);
693 
694 	if (error == EWOULDBLOCK)
695 		printf("timed out\n");
696 	else
697 		printf("stopped\n");
698 }
699