1 /*- 2 * SPDX-License-Identifier: BSD-4-Clause 3 * 4 * Copyright (c) 1982, 1986, 1989, 1993 5 * The Regents of the University of California. All rights reserved. 6 * (c) UNIX System Laboratories, Inc. 7 * Copyright (c) 2005 Robert N. M. Watson 8 * All rights reserved. 9 * 10 * All or some portions of this file are derived from material licensed 11 * to the University of California by American Telephone and Telegraph 12 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 13 * the permission of UNIX System Laboratories, Inc. 14 * 15 * Redistribution and use in source and binary forms, with or without 16 * modification, are permitted provided that the following conditions 17 * are met: 18 * 1. Redistributions of source code must retain the above copyright 19 * notice, this list of conditions and the following disclaimer. 20 * 2. Redistributions in binary form must reproduce the above copyright 21 * notice, this list of conditions and the following disclaimer in the 22 * documentation and/or other materials provided with the distribution. 23 * 3. Neither the name of the University nor the names of its contributors 24 * may be used to endorse or promote products derived from this software 25 * without specific prior written permission. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 28 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 29 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 30 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 31 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 32 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 33 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 34 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 35 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 36 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 37 * SUCH DAMAGE. 38 * 39 * Copyright (c) 1994 Christopher G. Demetriou 40 * 41 * Redistribution and use in source and binary forms, with or without 42 * modification, are permitted provided that the following conditions 43 * are met: 44 * 1. Redistributions of source code must retain the above copyright 45 * notice, this list of conditions and the following disclaimer. 46 * 2. Redistributions in binary form must reproduce the above copyright 47 * notice, this list of conditions and the following disclaimer in the 48 * documentation and/or other materials provided with the distribution. 49 * 3. All advertising materials mentioning features or use of this software 50 * must display the following acknowledgement: 51 * This product includes software developed by the University of 52 * California, Berkeley and its contributors. 53 * 4. Neither the name of the University nor the names of its contributors 54 * may be used to endorse or promote products derived from this software 55 * without specific prior written permission. 56 * 57 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 58 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 59 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 60 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 61 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 62 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 63 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 64 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 65 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 66 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 67 * SUCH DAMAGE. 68 */ 69 70 #include <sys/cdefs.h> 71 #include <sys/param.h> 72 #include <sys/systm.h> 73 #include <sys/acct.h> 74 #include <sys/fcntl.h> 75 #include <sys/kernel.h> 76 #include <sys/kthread.h> 77 #include <sys/limits.h> 78 #include <sys/lock.h> 79 #include <sys/malloc.h> 80 #include <sys/mount.h> 81 #include <sys/mutex.h> 82 #include <sys/namei.h> 83 #include <sys/priv.h> 84 #include <sys/proc.h> 85 #include <sys/resourcevar.h> 86 #include <sys/sched.h> 87 #include <sys/sx.h> 88 #include <sys/sysctl.h> 89 #include <sys/syslog.h> 90 #include <sys/sysproto.h> 91 #include <sys/tty.h> 92 #include <sys/vnode.h> 93 94 #include <security/mac/mac_framework.h> 95 96 _Static_assert(sizeof(struct acctv3) - offsetof(struct acctv3, ac_trailer) == 97 sizeof(struct acctv2) - offsetof(struct acctv2, ac_trailer), "trailer"); 98 _Static_assert(sizeof(struct acctv3) - offsetof(struct acctv3, ac_len2) == 99 sizeof(struct acctv2) - offsetof(struct acctv2, ac_len2), "len2"); 100 101 /* 102 * The routines implemented in this file are described in: 103 * Leffler, et al.: The Design and Implementation of the 4.3BSD 104 * UNIX Operating System (Addison Welley, 1989) 105 * on pages 62-63. 106 * On May 2007 the historic 3 bits base 8 exponent, 13 bit fraction 107 * compt_t representation described in the above reference was replaced 108 * with that of IEEE-754 floats. 109 * 110 * Arguably, to simplify accounting operations, this mechanism should 111 * be replaced by one in which an accounting log file (similar to /dev/klog) 112 * is read by a user process, etc. However, that has its own problems. 113 */ 114 115 /* Floating point definitions from <float.h>. */ 116 #define FLT_MANT_DIG 24 /* p */ 117 #define FLT_MAX_EXP 128 /* emax */ 118 119 /* 120 * Internal accounting functions. 121 * The former's operation is described in Leffler, et al., and the latter 122 * was provided by UCB with the 4.4BSD-Lite release 123 */ 124 static uint32_t encode_timeval(struct timeval); 125 static uint32_t encode_long(long); 126 static void acctwatch(void); 127 static void acct_thread(void *); 128 static int acct_disable(struct thread *, int); 129 130 /* 131 * Accounting vnode pointer, saved vnode pointer, and flags for each. 132 * acct_sx protects against changes to the active vnode and credentials 133 * while accounting records are being committed to disk. 134 */ 135 static int acct_configured; 136 static int acct_suspended; 137 static struct vnode *acct_vp; 138 static struct ucred *acct_cred; 139 static int acct_flags; 140 static struct sx acct_sx; 141 142 SX_SYSINIT(acct, &acct_sx, "acct_sx"); 143 144 /* 145 * State of the accounting kthread. 146 */ 147 static int acct_state; 148 149 #define ACCT_RUNNING 1 /* Accounting kthread is running. */ 150 #define ACCT_EXITREQ 2 /* Accounting kthread should exit. */ 151 152 /* 153 * Values associated with enabling and disabling accounting 154 */ 155 static int acctsuspend = 2; /* stop accounting when < 2% free space left */ 156 SYSCTL_INT(_kern, OID_AUTO, acct_suspend, CTLFLAG_RW, 157 &acctsuspend, 0, "percentage of free disk space below which accounting stops"); 158 159 static int acctresume = 4; /* resume when free space risen to > 4% */ 160 SYSCTL_INT(_kern, OID_AUTO, acct_resume, CTLFLAG_RW, 161 &acctresume, 0, "percentage of free disk space above which accounting resumes"); 162 163 static int acctchkfreq = 15; /* frequency (in seconds) to check space */ 164 165 static int 166 sysctl_acct_chkfreq(SYSCTL_HANDLER_ARGS) 167 { 168 int error, value; 169 170 /* Write out the old value. */ 171 error = SYSCTL_OUT(req, &acctchkfreq, sizeof(int)); 172 if (error || req->newptr == NULL) 173 return (error); 174 175 /* Read in and verify the new value. */ 176 error = SYSCTL_IN(req, &value, sizeof(int)); 177 if (error) 178 return (error); 179 if (value <= 0) 180 return (EINVAL); 181 acctchkfreq = value; 182 return (0); 183 } 184 SYSCTL_PROC(_kern, OID_AUTO, acct_chkfreq, 185 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, &acctchkfreq, 0, 186 sysctl_acct_chkfreq, "I", 187 "frequency for checking the free space"); 188 189 SYSCTL_INT(_kern, OID_AUTO, acct_configured, CTLFLAG_RD, &acct_configured, 0, 190 "Accounting configured or not"); 191 192 SYSCTL_INT(_kern, OID_AUTO, acct_suspended, CTLFLAG_RD, &acct_suspended, 0, 193 "Accounting suspended or not"); 194 195 /* 196 * Accounting system call. Written based on the specification and previous 197 * implementation done by Mark Tinguely. 198 */ 199 int 200 sys_acct(struct thread *td, struct acct_args *uap) 201 { 202 struct nameidata nd; 203 int error, flags, replacing; 204 205 error = priv_check(td, PRIV_ACCT); 206 if (error) 207 return (error); 208 209 /* 210 * If accounting is to be started to a file, open that file for 211 * appending and make sure it's a 'normal'. 212 */ 213 if (uap->path != NULL) { 214 NDINIT(&nd, LOOKUP, NOFOLLOW | AUDITVNODE1, UIO_USERSPACE, 215 uap->path); 216 flags = FWRITE | O_APPEND; 217 error = vn_open(&nd, &flags, 0, NULL); 218 if (error) 219 return (error); 220 NDFREE_PNBUF(&nd); 221 #ifdef MAC 222 error = mac_system_check_acct(td->td_ucred, nd.ni_vp); 223 if (error) { 224 VOP_UNLOCK(nd.ni_vp); 225 vn_close(nd.ni_vp, flags, td->td_ucred, td); 226 return (error); 227 } 228 #endif 229 VOP_UNLOCK(nd.ni_vp); 230 if (nd.ni_vp->v_type != VREG) { 231 vn_close(nd.ni_vp, flags, td->td_ucred, td); 232 return (EACCES); 233 } 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 error = acct_disable(td, !replacing); 264 if (uap->path == NULL) { 265 if (acct_state & ACCT_RUNNING) { 266 acct_state |= ACCT_EXITREQ; 267 wakeup(&acct_state); 268 } 269 sx_xunlock(&acct_sx); 270 return (error); 271 } 272 273 /* 274 * Save the new accounting file vnode, and schedule the new 275 * free space watcher. 276 */ 277 acct_vp = nd.ni_vp; 278 acct_cred = crhold(td->td_ucred); 279 acct_flags = flags; 280 if (acct_state & ACCT_RUNNING) 281 acct_state &= ~ACCT_EXITREQ; 282 else { 283 /* 284 * Try to start up an accounting kthread. We may start more 285 * than one, but if so the extras will commit suicide as 286 * soon as they start up. 287 */ 288 error = kproc_create(acct_thread, NULL, NULL, 0, 0, 289 "accounting"); 290 if (error) { 291 (void) acct_disable(td, 0); 292 sx_xunlock(&acct_sx); 293 log(LOG_NOTICE, "Unable to start accounting thread\n"); 294 return (error); 295 } 296 } 297 acct_configured = 1; 298 sx_xunlock(&acct_sx); 299 if (!replacing) 300 log(LOG_NOTICE, "Accounting enabled\n"); 301 return (error); 302 } 303 304 /* 305 * Disable currently in-progress accounting by closing the vnode, dropping 306 * our reference to the credential, and clearing the vnode's flags. 307 */ 308 static int 309 acct_disable(struct thread *td, int logging) 310 { 311 int error; 312 313 sx_assert(&acct_sx, SX_XLOCKED); 314 error = vn_close(acct_vp, acct_flags, acct_cred, td); 315 crfree(acct_cred); 316 acct_configured = 0; 317 acct_vp = NULL; 318 acct_cred = NULL; 319 acct_flags = 0; 320 if (logging) 321 log(LOG_NOTICE, "Accounting disabled\n"); 322 return (error); 323 } 324 325 /* 326 * Write out process accounting information, on process exit. 327 * Data to be written out is specified in Leffler, et al. 328 * and are enumerated below. (They're also noted in the system 329 * "acct.h" header file.) 330 */ 331 int 332 acct_process(struct thread *td) 333 { 334 struct acctv3 acct; 335 struct timeval ut, st, tmp; 336 struct proc *p; 337 struct rusage ru; 338 int t, ret; 339 340 /* 341 * Lockless check of accounting condition before doing the hard 342 * work. 343 */ 344 if (acct_vp == NULL || acct_suspended) 345 return (0); 346 347 memset(&acct, 0, sizeof(acct)); 348 349 sx_slock(&acct_sx); 350 351 /* 352 * If accounting isn't enabled, don't bother. Have to check again 353 * once we own the lock in case we raced with disabling of accounting 354 * by another thread. 355 */ 356 if (acct_vp == NULL || acct_suspended) { 357 sx_sunlock(&acct_sx); 358 return (0); 359 } 360 361 p = td->td_proc; 362 td->td_pflags2 |= TDP2_ACCT; 363 364 /* 365 * Get process accounting information. 366 */ 367 368 sx_slock(&proctree_lock); 369 PROC_LOCK(p); 370 371 /* (1) The terminal from which the process was started */ 372 if ((p->p_flag & P_CONTROLT) && p->p_pgrp->pg_session->s_ttyp) 373 acct.ac_tty = tty_udev(p->p_pgrp->pg_session->s_ttyp); 374 else 375 acct.ac_tty = NODEV; 376 sx_sunlock(&proctree_lock); 377 378 /* (2) The name of the command that ran */ 379 bcopy(p->p_comm, acct.ac_comm, sizeof acct.ac_comm); 380 381 /* (3) The amount of user and system time that was used */ 382 rufetchcalc(p, &ru, &ut, &st); 383 acct.ac_utime = encode_timeval(ut); 384 acct.ac_stime = encode_timeval(st); 385 386 /* (4) The elapsed time the command ran (and its starting time) */ 387 getboottime(&tmp); 388 timevaladd(&tmp, &p->p_stats->p_start); 389 acct.ac_btime = tmp.tv_sec; 390 microuptime(&tmp); 391 timevalsub(&tmp, &p->p_stats->p_start); 392 acct.ac_etime = encode_timeval(tmp); 393 394 /* (5) The average amount of memory used */ 395 tmp = ut; 396 timevaladd(&tmp, &st); 397 /* Convert tmp (i.e. u + s) into hz units to match ru_i*. */ 398 t = tmp.tv_sec * hz + tmp.tv_usec / tick; 399 if (t) 400 acct.ac_mem = encode_long((ru.ru_ixrss + ru.ru_idrss + 401 + ru.ru_isrss) / t); 402 else 403 acct.ac_mem = 0; 404 405 /* (6) The number of disk I/O operations done */ 406 acct.ac_io = encode_long(ru.ru_inblock + ru.ru_oublock); 407 408 /* (7) The UID and GID of the process */ 409 acct.ac_uid = p->p_ucred->cr_ruid; 410 acct.ac_gid = p->p_ucred->cr_rgid; 411 412 /* (8) The boolean flags that tell how the process terminated, etc. */ 413 acct.ac_flagx = p->p_acflag; 414 415 PROC_UNLOCK(p); 416 417 /* Setup ancillary structure fields. */ 418 acct.ac_flagx |= ANVER; 419 acct.ac_zero = 0; 420 acct.ac_version = 3; 421 acct.ac_len = acct.ac_len2 = sizeof(acct); 422 423 /* 424 * Write the accounting information to the file. 425 */ 426 ret = vn_rdwr(UIO_WRITE, acct_vp, (caddr_t)&acct, sizeof (acct), 427 (off_t)0, UIO_SYSSPACE, IO_APPEND|IO_UNIT, acct_cred, NOCRED, 428 NULL, td); 429 sx_sunlock(&acct_sx); 430 td->td_pflags2 &= ~TDP2_ACCT; 431 return (ret); 432 } 433 434 /* FLOAT_CONVERSION_START (Regression testing; don't remove this line.) */ 435 436 /* Convert timevals and longs into IEEE-754 bit patterns. */ 437 438 /* Mantissa mask (MSB is implied, so subtract 1). */ 439 #define MANT_MASK ((1 << (FLT_MANT_DIG - 1)) - 1) 440 441 /* 442 * We calculate integer values to a precision of approximately 443 * 28 bits. 444 * This is high-enough precision to fill the 24 float bits 445 * and low-enough to avoid overflowing the 32 int bits. 446 */ 447 #define CALC_BITS 28 448 449 /* log_2(1000000). */ 450 #define LOG2_1M 20 451 452 /* 453 * Convert the elements of a timeval into a 32-bit word holding 454 * the bits of a IEEE-754 float. 455 * The float value represents the timeval's value in microsecond units. 456 */ 457 static uint32_t 458 encode_timeval(struct timeval tv) 459 { 460 int log2_s; 461 int val, exp; /* Unnormalized value and exponent */ 462 int norm_exp; /* Normalized exponent */ 463 int shift; 464 465 /* 466 * First calculate value and exponent to about CALC_BITS precision. 467 * Note that the following conditionals have been ordered so that 468 * the most common cases appear first. 469 */ 470 if (tv.tv_sec == 0) { 471 if (tv.tv_usec == 0) 472 return (0); 473 exp = 0; 474 val = tv.tv_usec; 475 } else { 476 /* 477 * Calculate the value to a precision of approximately 478 * CALC_BITS. 479 */ 480 log2_s = fls(tv.tv_sec) - 1; 481 if (log2_s + LOG2_1M < CALC_BITS) { 482 exp = 0; 483 val = 1000000 * tv.tv_sec + tv.tv_usec; 484 } else { 485 exp = log2_s + LOG2_1M - CALC_BITS; 486 val = (unsigned int)(((uint64_t)1000000 * tv.tv_sec + 487 tv.tv_usec) >> exp); 488 } 489 } 490 /* Now normalize and pack the value into an IEEE-754 float. */ 491 norm_exp = fls(val) - 1; 492 shift = FLT_MANT_DIG - norm_exp - 1; 493 #ifdef ACCT_DEBUG 494 printf("val=%d exp=%d shift=%d log2(val)=%d\n", 495 val, exp, shift, norm_exp); 496 printf("exp=%x mant=%x\n", FLT_MAX_EXP - 1 + exp + norm_exp, 497 ((shift > 0 ? (val << shift) : (val >> -shift)) & MANT_MASK)); 498 #endif 499 return (((FLT_MAX_EXP - 1 + exp + norm_exp) << (FLT_MANT_DIG - 1)) | 500 ((shift > 0 ? val << shift : val >> -shift) & MANT_MASK)); 501 } 502 503 /* 504 * Convert a non-negative long value into the bit pattern of 505 * an IEEE-754 float value. 506 */ 507 static uint32_t 508 encode_long(long val) 509 { 510 int norm_exp; /* Normalized exponent */ 511 int shift; 512 513 if (val == 0) 514 return (0); 515 if (val < 0) { 516 log(LOG_NOTICE, 517 "encode_long: negative value %ld in accounting record\n", 518 val); 519 val = LONG_MAX; 520 } 521 norm_exp = fls(val) - 1; 522 shift = FLT_MANT_DIG - norm_exp - 1; 523 #ifdef ACCT_DEBUG 524 printf("val=%d shift=%d log2(val)=%d\n", 525 val, shift, norm_exp); 526 printf("exp=%x mant=%x\n", FLT_MAX_EXP - 1 + exp + norm_exp, 527 ((shift > 0 ? (val << shift) : (val >> -shift)) & MANT_MASK)); 528 #endif 529 return (((FLT_MAX_EXP - 1 + norm_exp) << (FLT_MANT_DIG - 1)) | 530 ((shift > 0 ? val << shift : val >> -shift) & MANT_MASK)); 531 } 532 533 /* FLOAT_CONVERSION_END (Regression testing; don't remove this line.) */ 534 535 /* 536 * Periodically check the filesystem to see if accounting 537 * should be turned on or off. Beware the case where the vnode 538 * has been vgone()'d out from underneath us, e.g. when the file 539 * system containing the accounting file has been forcibly unmounted. 540 */ 541 /* ARGSUSED */ 542 static void 543 acctwatch(void) 544 { 545 struct statfs *sp; 546 547 sx_assert(&acct_sx, SX_XLOCKED); 548 549 /* 550 * If accounting was disabled before our kthread was scheduled, 551 * then acct_vp might be NULL. If so, just ask our kthread to 552 * exit and return. 553 */ 554 if (acct_vp == NULL) { 555 acct_state |= ACCT_EXITREQ; 556 return; 557 } 558 559 /* 560 * If our vnode is no longer valid, tear it down and signal the 561 * accounting thread to die. 562 */ 563 if (acct_vp->v_type == VBAD) { 564 (void) acct_disable(NULL, 1); 565 acct_state |= ACCT_EXITREQ; 566 return; 567 } 568 569 /* 570 * Stopping here is better than continuing, maybe it will be VBAD 571 * next time around. 572 */ 573 sp = malloc(sizeof(struct statfs), M_STATFS, M_WAITOK); 574 if (VFS_STATFS(acct_vp->v_mount, sp) < 0) { 575 free(sp, M_STATFS); 576 return; 577 } 578 if (acct_suspended) { 579 if (sp->f_bavail > (int64_t)(acctresume * sp->f_blocks / 580 100)) { 581 acct_suspended = 0; 582 log(LOG_NOTICE, "Accounting resumed\n"); 583 } 584 } else { 585 if (sp->f_bavail <= (int64_t)(acctsuspend * sp->f_blocks / 586 100)) { 587 acct_suspended = 1; 588 log(LOG_NOTICE, "Accounting suspended\n"); 589 } 590 } 591 free(sp, M_STATFS); 592 } 593 594 /* 595 * The main loop for the dedicated kernel thread that periodically calls 596 * acctwatch(). 597 */ 598 static void 599 acct_thread(void *dummy) 600 { 601 u_char pri; 602 603 /* This is a low-priority kernel thread. */ 604 pri = PRI_MAX_KERN; 605 thread_lock(curthread); 606 sched_prio(curthread, pri); 607 thread_unlock(curthread); 608 609 /* If another accounting kthread is already running, just die. */ 610 sx_xlock(&acct_sx); 611 if (acct_state & ACCT_RUNNING) { 612 sx_xunlock(&acct_sx); 613 kproc_exit(0); 614 } 615 acct_state |= ACCT_RUNNING; 616 617 /* Loop until we are asked to exit. */ 618 while (!(acct_state & ACCT_EXITREQ)) { 619 /* Perform our periodic checks. */ 620 acctwatch(); 621 622 /* 623 * We check this flag again before sleeping since the 624 * acctwatch() might have shut down accounting and asked us 625 * to exit. 626 */ 627 if (!(acct_state & ACCT_EXITREQ)) { 628 sx_sleep(&acct_state, &acct_sx, 0, "-", 629 acctchkfreq * hz); 630 } 631 } 632 633 /* 634 * Acknowledge the exit request and shutdown. We clear both the 635 * exit request and running flags. 636 */ 637 acct_state = 0; 638 sx_xunlock(&acct_sx); 639 kproc_exit(0); 640 } 641