FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_acct.c
1 /*-
2 * Copyright (c) 1982, 1986, 1989, 1993
3 * The Regents of the University of California. All rights reserved.
4 * (c) UNIX System Laboratories, Inc.
5 * Copyright (c) 2005 Robert N. M. Watson
6 * All rights reserved.
7 *
8 * All or some portions of this file are derived from material licensed
9 * to the University of California by American Telephone and Telegraph
10 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
11 * the permission of UNIX System Laboratories, Inc.
12 *
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
15 * are met:
16 * 1. Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 * 2. Redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution.
21 * 4. Neither the name of the University nor the names of its contributors
22 * may be used to endorse or promote products derived from this software
23 * without specific prior written permission.
24 *
25 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
26 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
27 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
28 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
29 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
30 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
31 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
32 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
33 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
34 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
35 * SUCH DAMAGE.
36 *
37 * Copyright (c) 1994 Christopher G. Demetriou
38 *
39 * Redistribution and use in source and binary forms, with or without
40 * modification, are permitted provided that the following conditions
41 * are met:
42 * 1. Redistributions of source code must retain the above copyright
43 * notice, this list of conditions and the following disclaimer.
44 * 2. Redistributions in binary form must reproduce the above copyright
45 * notice, this list of conditions and the following disclaimer in the
46 * documentation and/or other materials provided with the distribution.
47 * 3. All advertising materials mentioning features or use of this software
48 * must display the following acknowledgement:
49 * This product includes software developed by the University of
50 * California, Berkeley and its contributors.
51 * 4. Neither the name of the University nor the names of its contributors
52 * may be used to endorse or promote products derived from this software
53 * without specific prior written permission.
54 *
55 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
56 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
57 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
58 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
59 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
60 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
61 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
62 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
63 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
64 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
65 * SUCH DAMAGE.
66 *
67 * @(#)kern_acct.c 8.1 (Berkeley) 6/14/93
68 */
69
70 #include <sys/cdefs.h>
71 __FBSDID("$FreeBSD: releng/8.4/sys/kern/kern_acct.c 247322 2013-02-26 16:55:59Z jhb $");
72
73 #include <sys/param.h>
74 #include <sys/systm.h>
75 #include <sys/acct.h>
76 #include <sys/fcntl.h>
77 #include <sys/kernel.h>
78 #include <sys/kthread.h>
79 #include <sys/limits.h>
80 #include <sys/lock.h>
81 #include <sys/mount.h>
82 #include <sys/mutex.h>
83 #include <sys/namei.h>
84 #include <sys/priv.h>
85 #include <sys/proc.h>
86 #include <sys/resourcevar.h>
87 #include <sys/sched.h>
88 #include <sys/sx.h>
89 #include <sys/sysctl.h>
90 #include <sys/sysent.h>
91 #include <sys/syslog.h>
92 #include <sys/sysproto.h>
93 #include <sys/tty.h>
94 #include <sys/vnode.h>
95
96 #include <security/mac/mac_framework.h>
97
98 /*
99 * The routines implemented in this file are described in:
100 * Leffler, et al.: The Design and Implementation of the 4.3BSD
101 * UNIX Operating System (Addison Welley, 1989)
102 * on pages 62-63.
103 * On May 2007 the historic 3 bits base 8 exponent, 13 bit fraction
104 * compt_t representation described in the above reference was replaced
105 * with that of IEEE-754 floats.
106 *
107 * Arguably, to simplify accounting operations, this mechanism should
108 * be replaced by one in which an accounting log file (similar to /dev/klog)
109 * is read by a user process, etc. However, that has its own problems.
110 */
111
112 /* Floating point definitions from <float.h>. */
113 #define FLT_MANT_DIG 24 /* p */
114 #define FLT_MAX_EXP 128 /* emax */
115
116 /*
117 * Internal accounting functions.
118 * The former's operation is described in Leffler, et al., and the latter
119 * was provided by UCB with the 4.4BSD-Lite release
120 */
121 static uint32_t encode_timeval(struct timeval);
122 static uint32_t encode_long(long);
123 static void acctwatch(void);
124 static void acct_thread(void *);
125 static int acct_disable(struct thread *, int);
126
127 /*
128 * Accounting vnode pointer, saved vnode pointer, and flags for each.
129 * acct_sx protects against changes to the active vnode and credentials
130 * while accounting records are being committed to disk.
131 */
132 static int acct_configured;
133 static int acct_suspended;
134 static struct vnode *acct_vp;
135 static struct ucred *acct_cred;
136 static int acct_flags;
137 static struct sx acct_sx;
138
139 SX_SYSINIT(acct, &acct_sx, "acct_sx");
140
141 /*
142 * State of the accounting kthread.
143 */
144 static int acct_state;
145
146 #define ACCT_RUNNING 1 /* Accounting kthread is running. */
147 #define ACCT_EXITREQ 2 /* Accounting kthread should exit. */
148
149 /*
150 * Values associated with enabling and disabling accounting
151 */
152 static int acctsuspend = 2; /* stop accounting when < 2% free space left */
153 SYSCTL_INT(_kern, OID_AUTO, acct_suspend, CTLFLAG_RW,
154 &acctsuspend, 0, "percentage of free disk space below which accounting stops");
155
156 static int acctresume = 4; /* resume when free space risen to > 4% */
157 SYSCTL_INT(_kern, OID_AUTO, acct_resume, CTLFLAG_RW,
158 &acctresume, 0, "percentage of free disk space above which accounting resumes");
159
160 static int acctchkfreq = 15; /* frequency (in seconds) to check space */
161
162 static int
163 sysctl_acct_chkfreq(SYSCTL_HANDLER_ARGS)
164 {
165 int error, value;
166
167 /* Write out the old value. */
168 error = SYSCTL_OUT(req, &acctchkfreq, sizeof(int));
169 if (error || req->newptr == NULL)
170 return (error);
171
172 /* Read in and verify the new value. */
173 error = SYSCTL_IN(req, &value, sizeof(int));
174 if (error)
175 return (error);
176 if (value <= 0)
177 return (EINVAL);
178 acctchkfreq = value;
179 return (0);
180 }
181 SYSCTL_PROC(_kern, OID_AUTO, acct_chkfreq, CTLTYPE_INT|CTLFLAG_RW,
182 &acctchkfreq, 0, sysctl_acct_chkfreq, "I",
183 "frequency for checking the free space");
184
185 SYSCTL_INT(_kern, OID_AUTO, acct_configured, CTLFLAG_RD, &acct_configured, 0,
186 "Accounting configured or not");
187
188 SYSCTL_INT(_kern, OID_AUTO, acct_suspended, CTLFLAG_RD, &acct_suspended, 0,
189 "Accounting suspended or not");
190
191 /*
192 * Accounting system call. Written based on the specification and previous
193 * implementation done by Mark Tinguely.
194 */
195 int
196 acct(struct thread *td, struct acct_args *uap)
197 {
198 struct nameidata nd;
199 int error, flags, vfslocked, replacing;
200
201 error = priv_check(td, PRIV_ACCT);
202 if (error)
203 return (error);
204
205 /*
206 * If accounting is to be started to a file, open that file for
207 * appending and make sure it's a 'normal'.
208 */
209 if (uap->path != NULL) {
210 NDINIT(&nd, LOOKUP, NOFOLLOW | MPSAFE | AUDITVNODE1,
211 UIO_USERSPACE, uap->path, td);
212 flags = FWRITE | O_APPEND;
213 error = vn_open(&nd, &flags, 0, NULL);
214 if (error)
215 return (error);
216 vfslocked = NDHASGIANT(&nd);
217 NDFREE(&nd, NDF_ONLY_PNBUF);
218 #ifdef MAC
219 error = mac_system_check_acct(td->td_ucred, nd.ni_vp);
220 if (error) {
221 VOP_UNLOCK(nd.ni_vp, 0);
222 vn_close(nd.ni_vp, flags, td->td_ucred, td);
223 VFS_UNLOCK_GIANT(vfslocked);
224 return (error);
225 }
226 #endif
227 VOP_UNLOCK(nd.ni_vp, 0);
228 if (nd.ni_vp->v_type != VREG) {
229 vn_close(nd.ni_vp, flags, td->td_ucred, td);
230 VFS_UNLOCK_GIANT(vfslocked);
231 return (EACCES);
232 }
233 VFS_UNLOCK_GIANT(vfslocked);
234 #ifdef MAC
235 } else {
236 error = mac_system_check_acct(td->td_ucred, NULL);
237 if (error)
238 return (error);
239 #endif
240 }
241
242 /*
243 * Disallow concurrent access to the accounting vnode while we swap
244 * it out, in order to prevent access after close.
245 */
246 sx_xlock(&acct_sx);
247
248 /*
249 * Don't log spurious disable/enable messages if we are
250 * switching from one accounting file to another due to log
251 * rotation.
252 */
253 replacing = (acct_vp != NULL && uap->path != NULL);
254
255 /*
256 * If accounting was previously enabled, kill the old space-watcher,
257 * close the file, and (if no new file was specified, leave). Reset
258 * the suspended state regardless of whether accounting remains
259 * enabled.
260 */
261 acct_suspended = 0;
262 if (acct_vp != NULL) {
263 vfslocked = VFS_LOCK_GIANT(acct_vp->v_mount);
264 error = acct_disable(td, !replacing);
265 VFS_UNLOCK_GIANT(vfslocked);
266 }
267 if (uap->path == NULL) {
268 if (acct_state & ACCT_RUNNING) {
269 acct_state |= ACCT_EXITREQ;
270 wakeup(&acct_state);
271 }
272 sx_xunlock(&acct_sx);
273 return (error);
274 }
275
276 /*
277 * Save the new accounting file vnode, and schedule the new
278 * free space watcher.
279 */
280 acct_vp = nd.ni_vp;
281 acct_cred = crhold(td->td_ucred);
282 acct_flags = flags;
283 if (acct_state & ACCT_RUNNING)
284 acct_state &= ~ACCT_EXITREQ;
285 else {
286 /*
287 * Try to start up an accounting kthread. We may start more
288 * than one, but if so the extras will commit suicide as
289 * soon as they start up.
290 */
291 error = kproc_create(acct_thread, NULL, NULL, 0, 0,
292 "accounting");
293 if (error) {
294 vfslocked = VFS_LOCK_GIANT(acct_vp->v_mount);
295 (void) vn_close(acct_vp, acct_flags, acct_cred, td);
296 VFS_UNLOCK_GIANT(vfslocked);
297 crfree(acct_cred);
298 acct_configured = 0;
299 acct_vp = NULL;
300 acct_cred = NULL;
301 acct_flags = 0;
302 sx_xunlock(&acct_sx);
303 log(LOG_NOTICE, "Unable to start accounting thread\n");
304 return (error);
305 }
306 }
307 acct_configured = 1;
308 sx_xunlock(&acct_sx);
309 if (!replacing)
310 log(LOG_NOTICE, "Accounting enabled\n");
311 return (error);
312 }
313
314 /*
315 * Disable currently in-progress accounting by closing the vnode, dropping
316 * our reference to the credential, and clearing the vnode's flags.
317 */
318 static int
319 acct_disable(struct thread *td, int logging)
320 {
321 int error;
322
323 sx_assert(&acct_sx, SX_XLOCKED);
324 error = vn_close(acct_vp, acct_flags, acct_cred, td);
325 crfree(acct_cred);
326 acct_configured = 0;
327 acct_vp = NULL;
328 acct_cred = NULL;
329 acct_flags = 0;
330 if (logging)
331 log(LOG_NOTICE, "Accounting disabled\n");
332 return (error);
333 }
334
335 /*
336 * Write out process accounting information, on process exit.
337 * Data to be written out is specified in Leffler, et al.
338 * and are enumerated below. (They're also noted in the system
339 * "acct.h" header file.)
340 */
341 int
342 acct_process(struct thread *td)
343 {
344 struct acctv2 acct;
345 struct timeval ut, st, tmp;
346 struct plimit *newlim, *oldlim;
347 struct proc *p;
348 struct rusage ru;
349 int t, ret, vfslocked;
350
351 /*
352 * Lockless check of accounting condition before doing the hard
353 * work.
354 */
355 if (acct_vp == NULL || acct_suspended)
356 return (0);
357
358 sx_slock(&acct_sx);
359
360 /*
361 * If accounting isn't enabled, don't bother. Have to check again
362 * once we own the lock in case we raced with disabling of accounting
363 * by another thread.
364 */
365 if (acct_vp == NULL || acct_suspended) {
366 sx_sunlock(&acct_sx);
367 return (0);
368 }
369
370 p = td->td_proc;
371
372 /*
373 * Get process accounting information.
374 */
375
376 sx_slock(&proctree_lock);
377 PROC_LOCK(p);
378
379 /* (1) The terminal from which the process was started */
380 if ((p->p_flag & P_CONTROLT) && p->p_pgrp->pg_session->s_ttyp)
381 acct.ac_tty = tty_udev(p->p_pgrp->pg_session->s_ttyp);
382 else
383 acct.ac_tty = NODEV;
384 sx_sunlock(&proctree_lock);
385
386 /* (2) The name of the command that ran */
387 bcopy(p->p_comm, acct.ac_comm, sizeof acct.ac_comm);
388
389 /* (3) The amount of user and system time that was used */
390 rufetchcalc(p, &ru, &ut, &st);
391 acct.ac_utime = encode_timeval(ut);
392 acct.ac_stime = encode_timeval(st);
393
394 /* (4) The elapsed time the command ran (and its starting time) */
395 tmp = boottime;
396 timevaladd(&tmp, &p->p_stats->p_start);
397 acct.ac_btime = tmp.tv_sec;
398 microuptime(&tmp);
399 timevalsub(&tmp, &p->p_stats->p_start);
400 acct.ac_etime = encode_timeval(tmp);
401
402 /* (5) The average amount of memory used */
403 tmp = ut;
404 timevaladd(&tmp, &st);
405 /* Convert tmp (i.e. u + s) into hz units to match ru_i*. */
406 t = tmp.tv_sec * hz + tmp.tv_usec / tick;
407 if (t)
408 acct.ac_mem = encode_long((ru.ru_ixrss + ru.ru_idrss +
409 + ru.ru_isrss) / t);
410 else
411 acct.ac_mem = 0;
412
413 /* (6) The number of disk I/O operations done */
414 acct.ac_io = encode_long(ru.ru_inblock + ru.ru_oublock);
415
416 /* (7) The UID and GID of the process */
417 acct.ac_uid = p->p_ucred->cr_ruid;
418 acct.ac_gid = p->p_ucred->cr_rgid;
419
420 /* (8) The boolean flags that tell how the process terminated, etc. */
421 acct.ac_flagx = p->p_acflag;
422 PROC_UNLOCK(p);
423
424 /* Setup ancillary structure fields. */
425 acct.ac_flagx |= ANVER;
426 acct.ac_zero = 0;
427 acct.ac_version = 2;
428 acct.ac_len = acct.ac_len2 = sizeof(acct);
429
430 /*
431 * Eliminate any file size rlimit.
432 */
433 newlim = lim_alloc();
434 PROC_LOCK(p);
435 oldlim = p->p_limit;
436 lim_copy(newlim, oldlim);
437 newlim->pl_rlimit[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;
438 p->p_limit = newlim;
439 PROC_UNLOCK(p);
440 lim_free(oldlim);
441
442 /*
443 * Write the accounting information to the file.
444 */
445 vfslocked = VFS_LOCK_GIANT(acct_vp->v_mount);
446 ret = vn_rdwr(UIO_WRITE, acct_vp, (caddr_t)&acct, sizeof (acct),
447 (off_t)0, UIO_SYSSPACE, IO_APPEND|IO_UNIT, acct_cred, NOCRED,
448 NULL, td);
449 VFS_UNLOCK_GIANT(vfslocked);
450 sx_sunlock(&acct_sx);
451 return (ret);
452 }
453
454 /* FLOAT_CONVERSION_START (Regression testing; don't remove this line.) */
455
456 /* Convert timevals and longs into IEEE-754 bit patterns. */
457
458 /* Mantissa mask (MSB is implied, so subtract 1). */
459 #define MANT_MASK ((1 << (FLT_MANT_DIG - 1)) - 1)
460
461 /*
462 * We calculate integer values to a precision of approximately
463 * 28 bits.
464 * This is high-enough precision to fill the 24 float bits
465 * and low-enough to avoid overflowing the 32 int bits.
466 */
467 #define CALC_BITS 28
468
469 /* log_2(1000000). */
470 #define LOG2_1M 20
471
472 /*
473 * Convert the elements of a timeval into a 32-bit word holding
474 * the bits of a IEEE-754 float.
475 * The float value represents the timeval's value in microsecond units.
476 */
477 static uint32_t
478 encode_timeval(struct timeval tv)
479 {
480 int log2_s;
481 int val, exp; /* Unnormalized value and exponent */
482 int norm_exp; /* Normalized exponent */
483 int shift;
484
485 /*
486 * First calculate value and exponent to about CALC_BITS precision.
487 * Note that the following conditionals have been ordered so that
488 * the most common cases appear first.
489 */
490 if (tv.tv_sec == 0) {
491 if (tv.tv_usec == 0)
492 return (0);
493 exp = 0;
494 val = tv.tv_usec;
495 } else {
496 /*
497 * Calculate the value to a precision of approximately
498 * CALC_BITS.
499 */
500 log2_s = fls(tv.tv_sec) - 1;
501 if (log2_s + LOG2_1M < CALC_BITS) {
502 exp = 0;
503 val = 1000000 * tv.tv_sec + tv.tv_usec;
504 } else {
505 exp = log2_s + LOG2_1M - CALC_BITS;
506 val = (unsigned int)(((u_int64_t)1000000 * tv.tv_sec +
507 tv.tv_usec) >> exp);
508 }
509 }
510 /* Now normalize and pack the value into an IEEE-754 float. */
511 norm_exp = fls(val) - 1;
512 shift = FLT_MANT_DIG - norm_exp - 1;
513 #ifdef ACCT_DEBUG
514 printf("val=%d exp=%d shift=%d log2(val)=%d\n",
515 val, exp, shift, norm_exp);
516 printf("exp=%x mant=%x\n", FLT_MAX_EXP - 1 + exp + norm_exp,
517 ((shift > 0 ? (val << shift) : (val >> -shift)) & MANT_MASK));
518 #endif
519 return (((FLT_MAX_EXP - 1 + exp + norm_exp) << (FLT_MANT_DIG - 1)) |
520 ((shift > 0 ? val << shift : val >> -shift) & MANT_MASK));
521 }
522
523 /*
524 * Convert a non-negative long value into the bit pattern of
525 * an IEEE-754 float value.
526 */
527 static uint32_t
528 encode_long(long val)
529 {
530 int norm_exp; /* Normalized exponent */
531 int shift;
532
533 if (val == 0)
534 return (0);
535 if (val < 0) {
536 log(LOG_NOTICE,
537 "encode_long: negative value %ld in accounting record\n",
538 val);
539 val = LONG_MAX;
540 }
541 norm_exp = fls(val) - 1;
542 shift = FLT_MANT_DIG - norm_exp - 1;
543 #ifdef ACCT_DEBUG
544 printf("val=%d shift=%d log2(val)=%d\n",
545 val, shift, norm_exp);
546 printf("exp=%x mant=%x\n", FLT_MAX_EXP - 1 + exp + norm_exp,
547 ((shift > 0 ? (val << shift) : (val >> -shift)) & MANT_MASK));
548 #endif
549 return (((FLT_MAX_EXP - 1 + norm_exp) << (FLT_MANT_DIG - 1)) |
550 ((shift > 0 ? val << shift : val >> -shift) & MANT_MASK));
551 }
552
553 /* FLOAT_CONVERSION_END (Regression testing; don't remove this line.) */
554
555 /*
556 * Periodically check the filesystem to see if accounting
557 * should be turned on or off. Beware the case where the vnode
558 * has been vgone()'d out from underneath us, e.g. when the file
559 * system containing the accounting file has been forcibly unmounted.
560 */
561 /* ARGSUSED */
562 static void
563 acctwatch(void)
564 {
565 struct statfs sb;
566 int vfslocked;
567
568 sx_assert(&acct_sx, SX_XLOCKED);
569
570 /*
571 * If accounting was disabled before our kthread was scheduled,
572 * then acct_vp might be NULL. If so, just ask our kthread to
573 * exit and return.
574 */
575 if (acct_vp == NULL) {
576 acct_state |= ACCT_EXITREQ;
577 return;
578 }
579
580 /*
581 * If our vnode is no longer valid, tear it down and signal the
582 * accounting thread to die.
583 */
584 vfslocked = VFS_LOCK_GIANT(acct_vp->v_mount);
585 if (acct_vp->v_type == VBAD) {
586 (void) acct_disable(NULL, 1);
587 VFS_UNLOCK_GIANT(vfslocked);
588 acct_state |= ACCT_EXITREQ;
589 return;
590 }
591
592 /*
593 * Stopping here is better than continuing, maybe it will be VBAD
594 * next time around.
595 */
596 if (VFS_STATFS(acct_vp->v_mount, &sb) < 0) {
597 VFS_UNLOCK_GIANT(vfslocked);
598 return;
599 }
600 VFS_UNLOCK_GIANT(vfslocked);
601 if (acct_suspended) {
602 if (sb.f_bavail > (int64_t)(acctresume * sb.f_blocks /
603 100)) {
604 acct_suspended = 0;
605 log(LOG_NOTICE, "Accounting resumed\n");
606 }
607 } else {
608 if (sb.f_bavail <= (int64_t)(acctsuspend * sb.f_blocks /
609 100)) {
610 acct_suspended = 1;
611 log(LOG_NOTICE, "Accounting suspended\n");
612 }
613 }
614 }
615
616 /*
617 * The main loop for the dedicated kernel thread that periodically calls
618 * acctwatch().
619 */
620 static void
621 acct_thread(void *dummy)
622 {
623 u_char pri;
624
625 /* This is a low-priority kernel thread. */
626 pri = PRI_MAX_KERN;
627 thread_lock(curthread);
628 sched_prio(curthread, pri);
629 thread_unlock(curthread);
630
631 /* If another accounting kthread is already running, just die. */
632 sx_xlock(&acct_sx);
633 if (acct_state & ACCT_RUNNING) {
634 sx_xunlock(&acct_sx);
635 kproc_exit(0);
636 }
637 acct_state |= ACCT_RUNNING;
638
639 /* Loop until we are asked to exit. */
640 while (!(acct_state & ACCT_EXITREQ)) {
641
642 /* Perform our periodic checks. */
643 acctwatch();
644
645 /*
646 * We check this flag again before sleeping since the
647 * acctwatch() might have shut down accounting and asked us
648 * to exit.
649 */
650 if (!(acct_state & ACCT_EXITREQ)) {
651 sx_sleep(&acct_state, &acct_sx, 0, "-",
652 acctchkfreq * hz);
653 }
654 }
655
656 /*
657 * Acknowledge the exit request and shutdown. We clear both the
658 * exit request and running flags.
659 */
660 acct_state = 0;
661 sx_xunlock(&acct_sx);
662 kproc_exit(0);
663 }
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