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("$FreeBSD$"); 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 sys_acct(struct thread *td, struct acct_args *uap) 197 { 198 struct nameidata nd; 199 int error, flags, 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 | 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 NDFREE(&nd, NDF_ONLY_PNBUF); 217 #ifdef MAC 218 error = mac_system_check_acct(td->td_ucred, nd.ni_vp); 219 if (error) { 220 VOP_UNLOCK(nd.ni_vp, 0); 221 vn_close(nd.ni_vp, flags, td->td_ucred, td); 222 return (error); 223 } 224 #endif 225 VOP_UNLOCK(nd.ni_vp, 0); 226 if (nd.ni_vp->v_type != VREG) { 227 vn_close(nd.ni_vp, flags, td->td_ucred, td); 228 return (EACCES); 229 } 230 #ifdef MAC 231 } else { 232 error = mac_system_check_acct(td->td_ucred, NULL); 233 if (error) 234 return (error); 235 #endif 236 } 237 238 /* 239 * Disallow concurrent access to the accounting vnode while we swap 240 * it out, in order to prevent access after close. 241 */ 242 sx_xlock(&acct_sx); 243 244 /* 245 * Don't log spurious disable/enable messages if we are 246 * switching from one accounting file to another due to log 247 * rotation. 248 */ 249 replacing = (acct_vp != NULL && uap->path != NULL); 250 251 /* 252 * If accounting was previously enabled, kill the old space-watcher, 253 * close the file, and (if no new file was specified, leave). Reset 254 * the suspended state regardless of whether accounting remains 255 * enabled. 256 */ 257 acct_suspended = 0; 258 if (acct_vp != NULL) 259 error = acct_disable(td, !replacing); 260 if (uap->path == NULL) { 261 if (acct_state & ACCT_RUNNING) { 262 acct_state |= ACCT_EXITREQ; 263 wakeup(&acct_state); 264 } 265 sx_xunlock(&acct_sx); 266 return (error); 267 } 268 269 /* 270 * Save the new accounting file vnode, and schedule the new 271 * free space watcher. 272 */ 273 acct_vp = nd.ni_vp; 274 acct_cred = crhold(td->td_ucred); 275 acct_flags = flags; 276 if (acct_state & ACCT_RUNNING) 277 acct_state &= ~ACCT_EXITREQ; 278 else { 279 /* 280 * Try to start up an accounting kthread. We may start more 281 * than one, but if so the extras will commit suicide as 282 * soon as they start up. 283 */ 284 error = kproc_create(acct_thread, NULL, NULL, 0, 0, 285 "accounting"); 286 if (error) { 287 (void) vn_close(acct_vp, acct_flags, acct_cred, td); 288 crfree(acct_cred); 289 acct_configured = 0; 290 acct_vp = NULL; 291 acct_cred = NULL; 292 acct_flags = 0; 293 sx_xunlock(&acct_sx); 294 log(LOG_NOTICE, "Unable to start accounting thread\n"); 295 return (error); 296 } 297 } 298 acct_configured = 1; 299 sx_xunlock(&acct_sx); 300 if (!replacing) 301 log(LOG_NOTICE, "Accounting enabled\n"); 302 return (error); 303 } 304 305 /* 306 * Disable currently in-progress accounting by closing the vnode, dropping 307 * our reference to the credential, and clearing the vnode's flags. 308 */ 309 static int 310 acct_disable(struct thread *td, int logging) 311 { 312 int error; 313 314 sx_assert(&acct_sx, SX_XLOCKED); 315 error = vn_close(acct_vp, acct_flags, acct_cred, td); 316 crfree(acct_cred); 317 acct_configured = 0; 318 acct_vp = NULL; 319 acct_cred = NULL; 320 acct_flags = 0; 321 if (logging) 322 log(LOG_NOTICE, "Accounting disabled\n"); 323 return (error); 324 } 325 326 /* 327 * Write out process accounting information, on process exit. 328 * Data to be written out is specified in Leffler, et al. 329 * and are enumerated below. (They're also noted in the system 330 * "acct.h" header file.) 331 */ 332 int 333 acct_process(struct thread *td) 334 { 335 struct acctv2 acct; 336 struct timeval ut, st, tmp; 337 struct plimit *newlim, *oldlim; 338 struct proc *p; 339 struct rusage ru; 340 int t, ret; 341 342 /* 343 * Lockless check of accounting condition before doing the hard 344 * work. 345 */ 346 if (acct_vp == NULL || acct_suspended) 347 return (0); 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; 362 363 /* 364 * Get process accounting information. 365 */ 366 367 sx_slock(&proctree_lock); 368 PROC_LOCK(p); 369 370 /* (1) The terminal from which the process was started */ 371 if ((p->p_flag & P_CONTROLT) && p->p_pgrp->pg_session->s_ttyp) 372 acct.ac_tty = tty_udev(p->p_pgrp->pg_session->s_ttyp); 373 else 374 acct.ac_tty = NODEV; 375 sx_sunlock(&proctree_lock); 376 377 /* (2) The name of the command that ran */ 378 bcopy(p->p_comm, acct.ac_comm, sizeof acct.ac_comm); 379 380 /* (3) The amount of user and system time that was used */ 381 rufetchcalc(p, &ru, &ut, &st); 382 acct.ac_utime = encode_timeval(ut); 383 acct.ac_stime = encode_timeval(st); 384 385 /* (4) The elapsed time the command ran (and its starting time) */ 386 tmp = boottime; 387 timevaladd(&tmp, &p->p_stats->p_start); 388 acct.ac_btime = tmp.tv_sec; 389 microuptime(&tmp); 390 timevalsub(&tmp, &p->p_stats->p_start); 391 acct.ac_etime = encode_timeval(tmp); 392 393 /* (5) The average amount of memory used */ 394 tmp = ut; 395 timevaladd(&tmp, &st); 396 /* Convert tmp (i.e. u + s) into hz units to match ru_i*. */ 397 t = tmp.tv_sec * hz + tmp.tv_usec / tick; 398 if (t) 399 acct.ac_mem = encode_long((ru.ru_ixrss + ru.ru_idrss + 400 + ru.ru_isrss) / t); 401 else 402 acct.ac_mem = 0; 403 404 /* (6) The number of disk I/O operations done */ 405 acct.ac_io = encode_long(ru.ru_inblock + ru.ru_oublock); 406 407 /* (7) The UID and GID of the process */ 408 acct.ac_uid = p->p_ucred->cr_ruid; 409 acct.ac_gid = p->p_ucred->cr_rgid; 410 411 /* (8) The boolean flags that tell how the process terminated, etc. */ 412 acct.ac_flagx = p->p_acflag; 413 PROC_UNLOCK(p); 414 415 /* Setup ancillary structure fields. */ 416 acct.ac_flagx |= ANVER; 417 acct.ac_zero = 0; 418 acct.ac_version = 2; 419 acct.ac_len = acct.ac_len2 = sizeof(acct); 420 421 /* 422 * Eliminate any file size rlimit. 423 */ 424 newlim = lim_alloc(); 425 PROC_LOCK(p); 426 oldlim = p->p_limit; 427 lim_copy(newlim, oldlim); 428 newlim->pl_rlimit[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY; 429 p->p_limit = newlim; 430 PROC_UNLOCK(p); 431 lim_free(oldlim); 432 433 /* 434 * Write the accounting information to the file. 435 */ 436 ret = vn_rdwr(UIO_WRITE, acct_vp, (caddr_t)&acct, sizeof (acct), 437 (off_t)0, UIO_SYSSPACE, IO_APPEND|IO_UNIT, acct_cred, NOCRED, 438 NULL, td); 439 sx_sunlock(&acct_sx); 440 return (ret); 441 } 442 443 /* FLOAT_CONVERSION_START (Regression testing; don't remove this line.) */ 444 445 /* Convert timevals and longs into IEEE-754 bit patterns. */ 446 447 /* Mantissa mask (MSB is implied, so subtract 1). */ 448 #define MANT_MASK ((1 << (FLT_MANT_DIG - 1)) - 1) 449 450 /* 451 * We calculate integer values to a precision of approximately 452 * 28 bits. 453 * This is high-enough precision to fill the 24 float bits 454 * and low-enough to avoid overflowing the 32 int bits. 455 */ 456 #define CALC_BITS 28 457 458 /* log_2(1000000). */ 459 #define LOG2_1M 20 460 461 /* 462 * Convert the elements of a timeval into a 32-bit word holding 463 * the bits of a IEEE-754 float. 464 * The float value represents the timeval's value in microsecond units. 465 */ 466 static uint32_t 467 encode_timeval(struct timeval tv) 468 { 469 int log2_s; 470 int val, exp; /* Unnormalized value and exponent */ 471 int norm_exp; /* Normalized exponent */ 472 int shift; 473 474 /* 475 * First calculate value and exponent to about CALC_BITS precision. 476 * Note that the following conditionals have been ordered so that 477 * the most common cases appear first. 478 */ 479 if (tv.tv_sec == 0) { 480 if (tv.tv_usec == 0) 481 return (0); 482 exp = 0; 483 val = tv.tv_usec; 484 } else { 485 /* 486 * Calculate the value to a precision of approximately 487 * CALC_BITS. 488 */ 489 log2_s = fls(tv.tv_sec) - 1; 490 if (log2_s + LOG2_1M < CALC_BITS) { 491 exp = 0; 492 val = 1000000 * tv.tv_sec + tv.tv_usec; 493 } else { 494 exp = log2_s + LOG2_1M - CALC_BITS; 495 val = (unsigned int)(((uint64_t)1000000 * tv.tv_sec + 496 tv.tv_usec) >> exp); 497 } 498 } 499 /* Now normalize and pack the value into an IEEE-754 float. */ 500 norm_exp = fls(val) - 1; 501 shift = FLT_MANT_DIG - norm_exp - 1; 502 #ifdef ACCT_DEBUG 503 printf("val=%d exp=%d shift=%d log2(val)=%d\n", 504 val, exp, shift, norm_exp); 505 printf("exp=%x mant=%x\n", FLT_MAX_EXP - 1 + exp + norm_exp, 506 ((shift > 0 ? (val << shift) : (val >> -shift)) & MANT_MASK)); 507 #endif 508 return (((FLT_MAX_EXP - 1 + exp + norm_exp) << (FLT_MANT_DIG - 1)) | 509 ((shift > 0 ? val << shift : val >> -shift) & MANT_MASK)); 510 } 511 512 /* 513 * Convert a non-negative long value into the bit pattern of 514 * an IEEE-754 float value. 515 */ 516 static uint32_t 517 encode_long(long val) 518 { 519 int norm_exp; /* Normalized exponent */ 520 int shift; 521 522 if (val == 0) 523 return (0); 524 if (val < 0) { 525 log(LOG_NOTICE, 526 "encode_long: negative value %ld in accounting record\n", 527 val); 528 val = LONG_MAX; 529 } 530 norm_exp = fls(val) - 1; 531 shift = FLT_MANT_DIG - norm_exp - 1; 532 #ifdef ACCT_DEBUG 533 printf("val=%d shift=%d log2(val)=%d\n", 534 val, shift, norm_exp); 535 printf("exp=%x mant=%x\n", FLT_MAX_EXP - 1 + exp + norm_exp, 536 ((shift > 0 ? (val << shift) : (val >> -shift)) & MANT_MASK)); 537 #endif 538 return (((FLT_MAX_EXP - 1 + norm_exp) << (FLT_MANT_DIG - 1)) | 539 ((shift > 0 ? val << shift : val >> -shift) & MANT_MASK)); 540 } 541 542 /* FLOAT_CONVERSION_END (Regression testing; don't remove this line.) */ 543 544 /* 545 * Periodically check the filesystem to see if accounting 546 * should be turned on or off. Beware the case where the vnode 547 * has been vgone()'d out from underneath us, e.g. when the file 548 * system containing the accounting file has been forcibly unmounted. 549 */ 550 /* ARGSUSED */ 551 static void 552 acctwatch(void) 553 { 554 struct statfs sb; 555 556 sx_assert(&acct_sx, SX_XLOCKED); 557 558 /* 559 * If accounting was disabled before our kthread was scheduled, 560 * then acct_vp might be NULL. If so, just ask our kthread to 561 * exit and return. 562 */ 563 if (acct_vp == NULL) { 564 acct_state |= ACCT_EXITREQ; 565 return; 566 } 567 568 /* 569 * If our vnode is no longer valid, tear it down and signal the 570 * accounting thread to die. 571 */ 572 if (acct_vp->v_type == VBAD) { 573 (void) acct_disable(NULL, 1); 574 acct_state |= ACCT_EXITREQ; 575 return; 576 } 577 578 /* 579 * Stopping here is better than continuing, maybe it will be VBAD 580 * next time around. 581 */ 582 if (VFS_STATFS(acct_vp->v_mount, &sb) < 0) 583 return; 584 if (acct_suspended) { 585 if (sb.f_bavail > (int64_t)(acctresume * sb.f_blocks / 586 100)) { 587 acct_suspended = 0; 588 log(LOG_NOTICE, "Accounting resumed\n"); 589 } 590 } else { 591 if (sb.f_bavail <= (int64_t)(acctsuspend * sb.f_blocks / 592 100)) { 593 acct_suspended = 1; 594 log(LOG_NOTICE, "Accounting suspended\n"); 595 } 596 } 597 } 598 599 /* 600 * The main loop for the dedicated kernel thread that periodically calls 601 * acctwatch(). 602 */ 603 static void 604 acct_thread(void *dummy) 605 { 606 u_char pri; 607 608 /* This is a low-priority kernel thread. */ 609 pri = PRI_MAX_KERN; 610 thread_lock(curthread); 611 sched_prio(curthread, pri); 612 thread_unlock(curthread); 613 614 /* If another accounting kthread is already running, just die. */ 615 sx_xlock(&acct_sx); 616 if (acct_state & ACCT_RUNNING) { 617 sx_xunlock(&acct_sx); 618 kproc_exit(0); 619 } 620 acct_state |= ACCT_RUNNING; 621 622 /* Loop until we are asked to exit. */ 623 while (!(acct_state & ACCT_EXITREQ)) { 624 625 /* Perform our periodic checks. */ 626 acctwatch(); 627 628 /* 629 * We check this flag again before sleeping since the 630 * acctwatch() might have shut down accounting and asked us 631 * to exit. 632 */ 633 if (!(acct_state & ACCT_EXITREQ)) { 634 sx_sleep(&acct_state, &acct_sx, 0, "-", 635 acctchkfreq * hz); 636 } 637 } 638 639 /* 640 * Acknowledge the exit request and shutdown. We clear both the 641 * exit request and running flags. 642 */ 643 acct_state = 0; 644 sx_xunlock(&acct_sx); 645 kproc_exit(0); 646 } 647