aboutsummaryrefslogtreecommitdiff
path: root/sys/kern/kern_acct.c
blob: ad272676083e4849e18a8ae8fbfe10177432b94a (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
/*-
 * SPDX-License-Identifier: BSD-4-Clause
 *
 * Copyright (c) 1982, 1986, 1989, 1993
 *	The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * Copyright (c) 2005 Robert N. M. Watson
 * All rights reserved.
 *
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * Copyright (c) 1994 Christopher G. Demetriou
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)kern_acct.c	8.1 (Berkeley) 6/14/93
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/acct.h>
#include <sys/fcntl.h>
#include <sys/kernel.h>
#include <sys/kthread.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/mutex.h>
#include <sys/namei.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
#include <sys/sched.h>
#include <sys/sx.h>
#include <sys/sysctl.h>
#include <sys/sysent.h>
#include <sys/syslog.h>
#include <sys/sysproto.h>
#include <sys/tty.h>
#include <sys/vnode.h>

#include <security/mac/mac_framework.h>

_Static_assert(sizeof(struct acctv3) - offsetof(struct acctv3, ac_trailer) ==
    sizeof(struct acctv2) - offsetof(struct acctv2, ac_trailer), "trailer");
_Static_assert(sizeof(struct acctv3) - offsetof(struct acctv3, ac_len2) ==
    sizeof(struct acctv2) - offsetof(struct acctv2, ac_len2), "len2");

/*
 * The routines implemented in this file are described in:
 *      Leffler, et al.: The Design and Implementation of the 4.3BSD
 *	    UNIX Operating System (Addison Welley, 1989)
 * on pages 62-63.
 * On May 2007 the historic 3 bits base 8 exponent, 13 bit fraction
 * compt_t representation described in the above reference was replaced
 * with that of IEEE-754 floats.
 *
 * Arguably, to simplify accounting operations, this mechanism should
 * be replaced by one in which an accounting log file (similar to /dev/klog)
 * is read by a user process, etc.  However, that has its own problems.
 */

/* Floating point definitions from <float.h>. */
#define FLT_MANT_DIG    24              /* p */
#define FLT_MAX_EXP     128             /* emax */

/*
 * Internal accounting functions.
 * The former's operation is described in Leffler, et al., and the latter
 * was provided by UCB with the 4.4BSD-Lite release
 */
static uint32_t	encode_timeval(struct timeval);
static uint32_t	encode_long(long);
static void	acctwatch(void);
static void	acct_thread(void *);
static int	acct_disable(struct thread *, int);

/*
 * Accounting vnode pointer, saved vnode pointer, and flags for each.
 * acct_sx protects against changes to the active vnode and credentials
 * while accounting records are being committed to disk.
 */
static int		 acct_configured;
static int		 acct_suspended;
static struct vnode	*acct_vp;
static struct ucred	*acct_cred;
static int		 acct_flags;
static struct sx	 acct_sx;

SX_SYSINIT(acct, &acct_sx, "acct_sx");

/*
 * State of the accounting kthread.
 */
static int		 acct_state;

#define	ACCT_RUNNING	1	/* Accounting kthread is running. */
#define	ACCT_EXITREQ	2	/* Accounting kthread should exit. */

/*
 * Values associated with enabling and disabling accounting
 */
static int acctsuspend = 2;	/* stop accounting when < 2% free space left */
SYSCTL_INT(_kern, OID_AUTO, acct_suspend, CTLFLAG_RW,
	&acctsuspend, 0, "percentage of free disk space below which accounting stops");

static int acctresume = 4;	/* resume when free space risen to > 4% */
SYSCTL_INT(_kern, OID_AUTO, acct_resume, CTLFLAG_RW,
	&acctresume, 0, "percentage of free disk space above which accounting resumes");

static int acctchkfreq = 15;	/* frequency (in seconds) to check space */

static int
sysctl_acct_chkfreq(SYSCTL_HANDLER_ARGS)
{
	int error, value;

	/* Write out the old value. */
	error = SYSCTL_OUT(req, &acctchkfreq, sizeof(int));
	if (error || req->newptr == NULL)
		return (error);

	/* Read in and verify the new value. */
	error = SYSCTL_IN(req, &value, sizeof(int));
	if (error)
		return (error);
	if (value <= 0)
		return (EINVAL);
	acctchkfreq = value;
	return (0);
}
SYSCTL_PROC(_kern, OID_AUTO, acct_chkfreq,
    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, &acctchkfreq, 0,
    sysctl_acct_chkfreq, "I",
    "frequency for checking the free space");

SYSCTL_INT(_kern, OID_AUTO, acct_configured, CTLFLAG_RD, &acct_configured, 0,
	"Accounting configured or not");

SYSCTL_INT(_kern, OID_AUTO, acct_suspended, CTLFLAG_RD, &acct_suspended, 0,
	"Accounting suspended or not");

/*
 * Accounting system call.  Written based on the specification and previous
 * implementation done by Mark Tinguely.
 */
int
sys_acct(struct thread *td, struct acct_args *uap)
{
	struct nameidata nd;
	int error, flags, replacing;

	error = priv_check(td, PRIV_ACCT);
	if (error)
		return (error);

	/*
	 * If accounting is to be started to a file, open that file for
	 * appending and make sure it's a 'normal'.
	 */
	if (uap->path != NULL) {
		NDINIT(&nd, LOOKUP, NOFOLLOW | AUDITVNODE1,
		    UIO_USERSPACE, uap->path, td);
		flags = FWRITE | O_APPEND;
		error = vn_open(&nd, &flags, 0, NULL);
		if (error)
			return (error);
		NDFREE(&nd, NDF_ONLY_PNBUF);
#ifdef MAC
		error = mac_system_check_acct(td->td_ucred, nd.ni_vp);
		if (error) {
			VOP_UNLOCK(nd.ni_vp);
			vn_close(nd.ni_vp, flags, td->td_ucred, td);
			return (error);
		}
#endif
		VOP_UNLOCK(nd.ni_vp);
		if (nd.ni_vp->v_type != VREG) {
			vn_close(nd.ni_vp, flags, td->td_ucred, td);
			return (EACCES);
		}
#ifdef MAC
	} else {
		error = mac_system_check_acct(td->td_ucred, NULL);
		if (error)
			return (error);
#endif
	}

	/*
	 * Disallow concurrent access to the accounting vnode while we swap
	 * it out, in order to prevent access after close.
	 */
	sx_xlock(&acct_sx);

	/*
	 * Don't log spurious disable/enable messages if we are
	 * switching from one accounting file to another due to log
	 * rotation.
	 */
	replacing = (acct_vp != NULL && uap->path != NULL);

	/*
	 * If accounting was previously enabled, kill the old space-watcher,
	 * close the file, and (if no new file was specified, leave).  Reset
	 * the suspended state regardless of whether accounting remains
	 * enabled.
	 */
	acct_suspended = 0;
	if (acct_vp != NULL)
		error = acct_disable(td, !replacing);
	if (uap->path == NULL) {
		if (acct_state & ACCT_RUNNING) {
			acct_state |= ACCT_EXITREQ;
			wakeup(&acct_state);
		}
		sx_xunlock(&acct_sx);
		return (error);
	}

	/*
	 * Save the new accounting file vnode, and schedule the new
	 * free space watcher.
	 */
	acct_vp = nd.ni_vp;
	acct_cred = crhold(td->td_ucred);
	acct_flags = flags;
	if (acct_state & ACCT_RUNNING)
		acct_state &= ~ACCT_EXITREQ;
	else {
		/*
		 * Try to start up an accounting kthread.  We may start more
		 * than one, but if so the extras will commit suicide as
		 * soon as they start up.
		 */
		error = kproc_create(acct_thread, NULL, NULL, 0, 0,
		    "accounting");
		if (error) {
			(void) acct_disable(td, 0);
			sx_xunlock(&acct_sx);
			log(LOG_NOTICE, "Unable to start accounting thread\n");
			return (error);
		}
	}
	acct_configured = 1;
	sx_xunlock(&acct_sx);
	if (!replacing)
		log(LOG_NOTICE, "Accounting enabled\n");
	return (error);
}

/*
 * Disable currently in-progress accounting by closing the vnode, dropping
 * our reference to the credential, and clearing the vnode's flags.
 */
static int
acct_disable(struct thread *td, int logging)
{
	int error;

	sx_assert(&acct_sx, SX_XLOCKED);
	error = vn_close(acct_vp, acct_flags, acct_cred, td);
	crfree(acct_cred);
	acct_configured = 0;
	acct_vp = NULL;
	acct_cred = NULL;
	acct_flags = 0;
	if (logging)
		log(LOG_NOTICE, "Accounting disabled\n");
	return (error);
}

/*
 * Write out process accounting information, on process exit.
 * Data to be written out is specified in Leffler, et al.
 * and are enumerated below.  (They're also noted in the system
 * "acct.h" header file.)
 */
int
acct_process(struct thread *td)
{
	struct acctv3 acct;
	struct timeval ut, st, tmp;
	struct proc *p;
	struct rusage ru;
	int t, ret;

	/*
	 * Lockless check of accounting condition before doing the hard
	 * work.
	 */
	if (acct_vp == NULL || acct_suspended)
		return (0);

	memset(&acct, 0, sizeof(acct));

	sx_slock(&acct_sx);

	/*
	 * If accounting isn't enabled, don't bother.  Have to check again
	 * once we own the lock in case we raced with disabling of accounting
	 * by another thread.
	 */
	if (acct_vp == NULL || acct_suspended) {
		sx_sunlock(&acct_sx);
		return (0);
	}

	p = td->td_proc;
	td->td_pflags2 |= TDP2_ACCT;

	/*
	 * Get process accounting information.
	 */

	sx_slock(&proctree_lock);
	PROC_LOCK(p);

	/* (1) The terminal from which the process was started */
	if ((p->p_flag & P_CONTROLT) && p->p_pgrp->pg_session->s_ttyp)
		acct.ac_tty = tty_udev(p->p_pgrp->pg_session->s_ttyp);
	else
		acct.ac_tty = NODEV;
	sx_sunlock(&proctree_lock);

	/* (2) The name of the command that ran */
	bcopy(p->p_comm, acct.ac_comm, sizeof acct.ac_comm);

	/* (3) The amount of user and system time that was used */
	rufetchcalc(p, &ru, &ut, &st);
	acct.ac_utime = encode_timeval(ut);
	acct.ac_stime = encode_timeval(st);

	/* (4) The elapsed time the command ran (and its starting time) */
	getboottime(&tmp);
	timevaladd(&tmp, &p->p_stats->p_start);
	acct.ac_btime = tmp.tv_sec;
	microuptime(&tmp);
	timevalsub(&tmp, &p->p_stats->p_start);
	acct.ac_etime = encode_timeval(tmp);

	/* (5) The average amount of memory used */
	tmp = ut;
	timevaladd(&tmp, &st);
	/* Convert tmp (i.e. u + s) into hz units to match ru_i*. */
	t = tmp.tv_sec * hz + tmp.tv_usec / tick;
	if (t)
		acct.ac_mem = encode_long((ru.ru_ixrss + ru.ru_idrss +
		    + ru.ru_isrss) / t);
	else
		acct.ac_mem = 0;

	/* (6) The number of disk I/O operations done */
	acct.ac_io = encode_long(ru.ru_inblock + ru.ru_oublock);

	/* (7) The UID and GID of the process */
	acct.ac_uid = p->p_ucred->cr_ruid;
	acct.ac_gid = p->p_ucred->cr_rgid;

	/* (8) The boolean flags that tell how the process terminated, etc. */
	acct.ac_flagx = p->p_acflag;

	PROC_UNLOCK(p);

	/* Setup ancillary structure fields. */
	acct.ac_flagx |= ANVER;
	acct.ac_zero = 0;
	acct.ac_version = 3;
	acct.ac_len = acct.ac_len2 = sizeof(acct);

	/*
	 * Write the accounting information to the file.
	 */
	ret = vn_rdwr(UIO_WRITE, acct_vp, (caddr_t)&acct, sizeof (acct),
	    (off_t)0, UIO_SYSSPACE, IO_APPEND|IO_UNIT, acct_cred, NOCRED,
	    NULL, td);
	sx_sunlock(&acct_sx);
	td->td_pflags2 &= ~TDP2_ACCT;
	return (ret);
}

/* FLOAT_CONVERSION_START (Regression testing; don't remove this line.) */

/* Convert timevals and longs into IEEE-754 bit patterns. */

/* Mantissa mask (MSB is implied, so subtract 1). */
#define MANT_MASK ((1 << (FLT_MANT_DIG - 1)) - 1)

/*
 * We calculate integer values to a precision of approximately
 * 28 bits.
 * This is high-enough precision to fill the 24 float bits
 * and low-enough to avoid overflowing the 32 int bits.
 */
#define CALC_BITS 28

/* log_2(1000000). */
#define LOG2_1M 20

/*
 * Convert the elements of a timeval into a 32-bit word holding
 * the bits of a IEEE-754 float.
 * The float value represents the timeval's value in microsecond units.
 */
static uint32_t
encode_timeval(struct timeval tv)
{
	int log2_s;
	int val, exp;	/* Unnormalized value and exponent */
	int norm_exp;	/* Normalized exponent */
	int shift;

	/*
	 * First calculate value and exponent to about CALC_BITS precision.
	 * Note that the following conditionals have been ordered so that
	 * the most common cases appear first.
	 */
	if (tv.tv_sec == 0) {
		if (tv.tv_usec == 0)
			return (0);
		exp = 0;
		val = tv.tv_usec;
	} else {
		/*
		 * Calculate the value to a precision of approximately
		 * CALC_BITS.
		 */
		log2_s = fls(tv.tv_sec) - 1;
		if (log2_s + LOG2_1M < CALC_BITS) {
			exp = 0;
			val = 1000000 * tv.tv_sec + tv.tv_usec;
		} else {
			exp = log2_s + LOG2_1M - CALC_BITS;
			val = (unsigned int)(((uint64_t)1000000 * tv.tv_sec +
			    tv.tv_usec) >> exp);
		}
	}
	/* Now normalize and pack the value into an IEEE-754 float. */
	norm_exp = fls(val) - 1;
	shift = FLT_MANT_DIG - norm_exp - 1;
#ifdef ACCT_DEBUG
	printf("val=%d exp=%d shift=%d log2(val)=%d\n",
	    val, exp, shift, norm_exp);
	printf("exp=%x mant=%x\n", FLT_MAX_EXP - 1 + exp + norm_exp,
	    ((shift > 0 ? (val << shift) : (val >> -shift)) & MANT_MASK));
#endif
	return (((FLT_MAX_EXP - 1 + exp + norm_exp) << (FLT_MANT_DIG - 1)) |
	    ((shift > 0 ? val << shift : val >> -shift) & MANT_MASK));
}

/*
 * Convert a non-negative long value into the bit pattern of
 * an IEEE-754 float value.
 */
static uint32_t
encode_long(long val)
{
	int norm_exp;	/* Normalized exponent */
	int shift;

	if (val == 0)
		return (0);
	if (val < 0) {
		log(LOG_NOTICE,
		    "encode_long: negative value %ld in accounting record\n",
		    val);
		val = LONG_MAX;
	}
	norm_exp = fls(val) - 1;
	shift = FLT_MANT_DIG - norm_exp - 1;
#ifdef ACCT_DEBUG
	printf("val=%d shift=%d log2(val)=%d\n",
	    val, shift, norm_exp);
	printf("exp=%x mant=%x\n", FLT_MAX_EXP - 1 + exp + norm_exp,
	    ((shift > 0 ? (val << shift) : (val >> -shift)) & MANT_MASK));
#endif
	return (((FLT_MAX_EXP - 1 + norm_exp) << (FLT_MANT_DIG - 1)) |
	    ((shift > 0 ? val << shift : val >> -shift) & MANT_MASK));
}

/* FLOAT_CONVERSION_END (Regression testing; don't remove this line.) */

/*
 * Periodically check the filesystem to see if accounting
 * should be turned on or off.  Beware the case where the vnode
 * has been vgone()'d out from underneath us, e.g. when the file
 * system containing the accounting file has been forcibly unmounted.
 */
/* ARGSUSED */
static void
acctwatch(void)
{
	struct statfs *sp;

	sx_assert(&acct_sx, SX_XLOCKED);

	/*
	 * If accounting was disabled before our kthread was scheduled,
	 * then acct_vp might be NULL.  If so, just ask our kthread to
	 * exit and return.
	 */
	if (acct_vp == NULL) {
		acct_state |= ACCT_EXITREQ;
		return;
	}

	/*
	 * If our vnode is no longer valid, tear it down and signal the
	 * accounting thread to die.
	 */
	if (acct_vp->v_type == VBAD) {
		(void) acct_disable(NULL, 1);
		acct_state |= ACCT_EXITREQ;
		return;
	}

	/*
	 * Stopping here is better than continuing, maybe it will be VBAD
	 * next time around.
	 */
	sp = malloc(sizeof(struct statfs), M_STATFS, M_WAITOK);
	if (VFS_STATFS(acct_vp->v_mount, sp) < 0) {
		free(sp, M_STATFS);
		return;
	}
	if (acct_suspended) {
		if (sp->f_bavail > (int64_t)(acctresume * sp->f_blocks /
		    100)) {
			acct_suspended = 0;
			log(LOG_NOTICE, "Accounting resumed\n");
		}
	} else {
		if (sp->f_bavail <= (int64_t)(acctsuspend * sp->f_blocks /
		    100)) {
			acct_suspended = 1;
			log(LOG_NOTICE, "Accounting suspended\n");
		}
	}
	free(sp, M_STATFS);
}

/*
 * The main loop for the dedicated kernel thread that periodically calls
 * acctwatch().
 */
static void
acct_thread(void *dummy)
{
	u_char pri;

	/* This is a low-priority kernel thread. */
	pri = PRI_MAX_KERN;
	thread_lock(curthread);
	sched_prio(curthread, pri);
	thread_unlock(curthread);

	/* If another accounting kthread is already running, just die. */
	sx_xlock(&acct_sx);
	if (acct_state & ACCT_RUNNING) {
		sx_xunlock(&acct_sx);
		kproc_exit(0);
	}
	acct_state |= ACCT_RUNNING;

	/* Loop until we are asked to exit. */
	while (!(acct_state & ACCT_EXITREQ)) {
		/* Perform our periodic checks. */
		acctwatch();

		/*
		 * We check this flag again before sleeping since the
		 * acctwatch() might have shut down accounting and asked us
		 * to exit.
		 */
		if (!(acct_state & ACCT_EXITREQ)) {
			sx_sleep(&acct_state, &acct_sx, 0, "-",
			    acctchkfreq * hz);
		}
	}

	/*
	 * Acknowledge the exit request and shutdown.  We clear both the
	 * exit request and running flags.
	 */
	acct_state = 0;
	sx_xunlock(&acct_sx);
	kproc_exit(0);
}