1 /* 2 * Copyright (c) 1982, 1986, 1989, 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_fork.c 8.6 (Berkeley) 4/8/94 39 * $FreeBSD$ 40 */ 41 42 #include "opt_ktrace.h" 43 44 #include <sys/param.h> 45 #include <sys/systm.h> 46 #include <sys/sysproto.h> 47 #include <sys/filedesc.h> 48 #include <sys/kernel.h> 49 #include <sys/sysctl.h> 50 #include <sys/malloc.h> 51 #include <sys/mutex.h> 52 #include <sys/proc.h> 53 #include <sys/resourcevar.h> 54 #include <sys/syscall.h> 55 #include <sys/vnode.h> 56 #include <sys/acct.h> 57 #include <sys/ktr.h> 58 #include <sys/ktrace.h> 59 #include <sys/kthread.h> 60 #include <sys/unistd.h> 61 #include <sys/jail.h> 62 63 #include <vm/vm.h> 64 #include <sys/lock.h> 65 #include <vm/pmap.h> 66 #include <vm/vm_map.h> 67 #include <vm/vm_extern.h> 68 #include <vm/vm_zone.h> 69 70 #include <sys/vmmeter.h> 71 #include <sys/user.h> 72 73 static MALLOC_DEFINE(M_ATFORK, "atfork", "atfork callback"); 74 75 static int fast_vfork = 1; 76 SYSCTL_INT(_kern, OID_AUTO, fast_vfork, CTLFLAG_RW, &fast_vfork, 0, 77 "flag to indicate whether we have a fast vfork()"); 78 79 /* 80 * These are the stuctures used to create a callout list for things to do 81 * when forking a process 82 */ 83 struct forklist { 84 forklist_fn function; 85 TAILQ_ENTRY(forklist) next; 86 }; 87 88 TAILQ_HEAD(forklist_head, forklist); 89 static struct forklist_head fork_list = TAILQ_HEAD_INITIALIZER(fork_list); 90 91 #ifndef _SYS_SYSPROTO_H_ 92 struct fork_args { 93 int dummy; 94 }; 95 #endif 96 97 /* ARGSUSED */ 98 int 99 fork(p, uap) 100 struct proc *p; 101 struct fork_args *uap; 102 { 103 int error; 104 struct proc *p2; 105 106 error = fork1(p, RFFDG | RFPROC, &p2); 107 if (error == 0) { 108 p->p_retval[0] = p2->p_pid; 109 p->p_retval[1] = 0; 110 } 111 return error; 112 } 113 114 /* ARGSUSED */ 115 int 116 vfork(p, uap) 117 struct proc *p; 118 struct vfork_args *uap; 119 { 120 int error; 121 struct proc *p2; 122 123 error = fork1(p, RFFDG | RFPROC | RFPPWAIT | RFMEM, &p2); 124 if (error == 0) { 125 p->p_retval[0] = p2->p_pid; 126 p->p_retval[1] = 0; 127 } 128 return error; 129 } 130 131 int 132 rfork(p, uap) 133 struct proc *p; 134 struct rfork_args *uap; 135 { 136 int error; 137 struct proc *p2; 138 139 /* mask kernel only flags out of the user flags */ 140 error = fork1(p, uap->flags & ~RFKERNELONLY, &p2); 141 if (error == 0) { 142 p->p_retval[0] = p2 ? p2->p_pid : 0; 143 p->p_retval[1] = 0; 144 } 145 return error; 146 } 147 148 149 int nprocs = 1; /* process 0 */ 150 static int nextpid = 0; 151 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &nextpid, 0, 152 "Last used PID"); 153 154 /* 155 * Random component to nextpid generation. We mix in a random factor to make 156 * it a little harder to predict. We sanity check the modulus value to avoid 157 * doing it in critical paths. Don't let it be too small or we pointlessly 158 * waste randomness entropy, and don't let it be impossibly large. Using a 159 * modulus that is too big causes a LOT more process table scans and slows 160 * down fork processing as the pidchecked caching is defeated. 161 */ 162 static int randompid = 0; 163 164 static int 165 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 166 { 167 int error, pid; 168 169 pid = randompid; 170 error = sysctl_handle_int(oidp, &pid, 0, req); 171 if (error || !req->newptr) 172 return (error); 173 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 174 pid = PID_MAX - 100; 175 else if (pid < 2) /* NOP */ 176 pid = 0; 177 else if (pid < 100) /* Make it reasonable */ 178 pid = 100; 179 randompid = pid; 180 return (error); 181 } 182 183 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 184 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 185 186 int 187 fork1(p1, flags, procp) 188 struct proc *p1; /* parent proc */ 189 int flags; 190 struct proc **procp; /* child proc */ 191 { 192 struct proc *p2, *pptr; 193 uid_t uid; 194 struct proc *newproc; 195 int trypid; 196 int ok; 197 static int pidchecked = 0; 198 struct forklist *ep; 199 200 /* Can't copy and clear */ 201 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 202 return (EINVAL); 203 204 /* 205 * Here we don't create a new process, but we divorce 206 * certain parts of a process from itself. 207 */ 208 if ((flags & RFPROC) == 0) { 209 210 vm_fork(p1, 0, flags); 211 212 /* 213 * Close all file descriptors. 214 */ 215 if (flags & RFCFDG) { 216 struct filedesc *fdtmp; 217 fdtmp = fdinit(p1); 218 fdfree(p1); 219 p1->p_fd = fdtmp; 220 } 221 222 /* 223 * Unshare file descriptors (from parent.) 224 */ 225 if (flags & RFFDG) { 226 if (p1->p_fd->fd_refcnt > 1) { 227 struct filedesc *newfd; 228 newfd = fdcopy(p1); 229 fdfree(p1); 230 p1->p_fd = newfd; 231 } 232 } 233 *procp = NULL; 234 return (0); 235 } 236 237 /* 238 * Although process entries are dynamically created, we still keep 239 * a global limit on the maximum number we will create. Don't allow 240 * a nonprivileged user to use the last process; don't let root 241 * exceed the limit. The variable nprocs is the current number of 242 * processes, maxproc is the limit. 243 */ 244 uid = p1->p_cred->p_ruid; 245 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 246 tablefull("proc"); 247 return (EAGAIN); 248 } 249 /* 250 * Increment the nprocs resource before blocking can occur. There 251 * are hard-limits as to the number of processes that can run. 252 */ 253 nprocs++; 254 255 /* 256 * Increment the count of procs running with this uid. Don't allow 257 * a nonprivileged user to exceed their current limit. 258 */ 259 ok = chgproccnt(p1->p_cred->p_uidinfo, 1, 260 (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0); 261 if (!ok) { 262 /* 263 * Back out the process count 264 */ 265 nprocs--; 266 return (EAGAIN); 267 } 268 269 /* Allocate new proc. */ 270 newproc = zalloc(proc_zone); 271 272 /* 273 * Setup linkage for kernel based threading 274 */ 275 if((flags & RFTHREAD) != 0) { 276 newproc->p_peers = p1->p_peers; 277 p1->p_peers = newproc; 278 newproc->p_leader = p1->p_leader; 279 } else { 280 newproc->p_peers = NULL; 281 newproc->p_leader = newproc; 282 } 283 284 newproc->p_vmspace = NULL; 285 286 /* 287 * Find an unused process ID. We remember a range of unused IDs 288 * ready to use (from nextpid+1 through pidchecked-1). 289 * 290 * If RFHIGHPID is set (used during system boot), do not allocate 291 * low-numbered pids. 292 */ 293 ALLPROC_LOCK(AP_EXCLUSIVE); 294 trypid = nextpid + 1; 295 if (flags & RFHIGHPID) { 296 if (trypid < 10) { 297 trypid = 10; 298 } 299 } else { 300 if (randompid) 301 trypid += arc4random() % randompid; 302 } 303 retry: 304 /* 305 * If the process ID prototype has wrapped around, 306 * restart somewhat above 0, as the low-numbered procs 307 * tend to include daemons that don't exit. 308 */ 309 if (trypid >= PID_MAX) { 310 trypid = trypid % PID_MAX; 311 if (trypid < 100) 312 trypid += 100; 313 pidchecked = 0; 314 } 315 if (trypid >= pidchecked) { 316 int doingzomb = 0; 317 318 pidchecked = PID_MAX; 319 /* 320 * Scan the active and zombie procs to check whether this pid 321 * is in use. Remember the lowest pid that's greater 322 * than trypid, so we can avoid checking for a while. 323 */ 324 p2 = LIST_FIRST(&allproc); 325 again: 326 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 327 while (p2->p_pid == trypid || 328 p2->p_pgrp->pg_id == trypid || 329 p2->p_session->s_sid == trypid) { 330 trypid++; 331 if (trypid >= pidchecked) 332 goto retry; 333 } 334 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 335 pidchecked = p2->p_pid; 336 if (p2->p_pgrp->pg_id > trypid && 337 pidchecked > p2->p_pgrp->pg_id) 338 pidchecked = p2->p_pgrp->pg_id; 339 if (p2->p_session->s_sid > trypid && 340 pidchecked > p2->p_session->s_sid) 341 pidchecked = p2->p_session->s_sid; 342 } 343 if (!doingzomb) { 344 doingzomb = 1; 345 p2 = LIST_FIRST(&zombproc); 346 goto again; 347 } 348 } 349 350 /* 351 * RFHIGHPID does not mess with the nextpid counter during boot. 352 */ 353 if (flags & RFHIGHPID) 354 pidchecked = 0; 355 else 356 nextpid = trypid; 357 358 p2 = newproc; 359 p2->p_intr_nesting_level = 0; 360 p2->p_stat = SIDL; /* protect against others */ 361 p2->p_pid = trypid; 362 LIST_INSERT_HEAD(&allproc, p2, p_list); 363 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 364 ALLPROC_LOCK(AP_RELEASE); 365 366 /* 367 * Make a proc table entry for the new process. 368 * Start by zeroing the section of proc that is zero-initialized, 369 * then copy the section that is copied directly from the parent. 370 */ 371 bzero(&p2->p_startzero, 372 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 373 bcopy(&p1->p_startcopy, &p2->p_startcopy, 374 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 375 376 mtx_init(&p2->p_mtx, "process lock", MTX_DEF); 377 p2->p_aioinfo = NULL; 378 379 /* 380 * Duplicate sub-structures as needed. 381 * Increase reference counts on shared objects. 382 * The p_stats and p_sigacts substructs are set in vm_fork. 383 */ 384 p2->p_flag = 0; 385 mtx_lock_spin(&sched_lock); 386 p2->p_sflag = PS_INMEM; 387 if (p1->p_sflag & PS_PROFIL) 388 startprofclock(p2); 389 mtx_unlock_spin(&sched_lock); 390 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 391 M_SUBPROC, M_WAITOK); 392 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 393 p2->p_cred->p_refcnt = 1; 394 crhold(p1->p_ucred); 395 uihold(p1->p_cred->p_uidinfo); 396 397 if (p2->p_prison) { 398 p2->p_prison->pr_ref++; 399 p2->p_flag |= P_JAILED; 400 } 401 402 if (p2->p_args) 403 p2->p_args->ar_ref++; 404 405 if (flags & RFSIGSHARE) { 406 p2->p_procsig = p1->p_procsig; 407 p2->p_procsig->ps_refcnt++; 408 if (p1->p_sigacts == &p1->p_addr->u_sigacts) { 409 struct sigacts *newsigacts; 410 int s; 411 412 /* Create the shared sigacts structure */ 413 MALLOC(newsigacts, struct sigacts *, 414 sizeof(struct sigacts), M_SUBPROC, M_WAITOK); 415 s = splhigh(); 416 /* 417 * Set p_sigacts to the new shared structure. 418 * Note that this is updating p1->p_sigacts at the 419 * same time, since p_sigacts is just a pointer to 420 * the shared p_procsig->ps_sigacts. 421 */ 422 p2->p_sigacts = newsigacts; 423 bcopy(&p1->p_addr->u_sigacts, p2->p_sigacts, 424 sizeof(*p2->p_sigacts)); 425 *p2->p_sigacts = p1->p_addr->u_sigacts; 426 splx(s); 427 } 428 } else { 429 MALLOC(p2->p_procsig, struct procsig *, sizeof(struct procsig), 430 M_SUBPROC, M_WAITOK); 431 bcopy(p1->p_procsig, p2->p_procsig, sizeof(*p2->p_procsig)); 432 p2->p_procsig->ps_refcnt = 1; 433 p2->p_sigacts = NULL; /* finished in vm_fork() */ 434 } 435 if (flags & RFLINUXTHPN) 436 p2->p_sigparent = SIGUSR1; 437 else 438 p2->p_sigparent = SIGCHLD; 439 440 /* bump references to the text vnode (for procfs) */ 441 p2->p_textvp = p1->p_textvp; 442 if (p2->p_textvp) 443 VREF(p2->p_textvp); 444 445 if (flags & RFCFDG) 446 p2->p_fd = fdinit(p1); 447 else if (flags & RFFDG) 448 p2->p_fd = fdcopy(p1); 449 else 450 p2->p_fd = fdshare(p1); 451 452 /* 453 * If p_limit is still copy-on-write, bump refcnt, 454 * otherwise get a copy that won't be modified. 455 * (If PL_SHAREMOD is clear, the structure is shared 456 * copy-on-write.) 457 */ 458 if (p1->p_limit->p_lflags & PL_SHAREMOD) 459 p2->p_limit = limcopy(p1->p_limit); 460 else { 461 p2->p_limit = p1->p_limit; 462 p2->p_limit->p_refcnt++; 463 } 464 465 /* 466 * Preserve some more flags in subprocess. P_PROFIL has already 467 * been preserved. 468 */ 469 p2->p_flag |= p1->p_flag & P_SUGID; 470 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 471 p2->p_flag |= P_CONTROLT; 472 if (flags & RFPPWAIT) 473 p2->p_flag |= P_PPWAIT; 474 475 LIST_INSERT_AFTER(p1, p2, p_pglist); 476 477 /* 478 * Attach the new process to its parent. 479 * 480 * If RFNOWAIT is set, the newly created process becomes a child 481 * of init. This effectively disassociates the child from the 482 * parent. 483 */ 484 if (flags & RFNOWAIT) 485 pptr = initproc; 486 else 487 pptr = p1; 488 PROCTREE_LOCK(PT_EXCLUSIVE); 489 p2->p_pptr = pptr; 490 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 491 PROCTREE_LOCK(PT_RELEASE); 492 LIST_INIT(&p2->p_children); 493 LIST_INIT(&p2->p_heldmtx); 494 LIST_INIT(&p2->p_contested); 495 496 callout_init(&p2->p_itcallout, 0); 497 callout_init(&p2->p_slpcallout, 1); 498 499 #ifdef KTRACE 500 /* 501 * Copy traceflag and tracefile if enabled. 502 * If not inherited, these were zeroed above. 503 */ 504 if (p1->p_traceflag&KTRFAC_INHERIT) { 505 p2->p_traceflag = p1->p_traceflag; 506 if ((p2->p_tracep = p1->p_tracep) != NULL) 507 VREF(p2->p_tracep); 508 } 509 #endif 510 511 /* 512 * set priority of child to be that of parent 513 */ 514 p2->p_estcpu = p1->p_estcpu; 515 516 /* 517 * This begins the section where we must prevent the parent 518 * from being swapped. 519 */ 520 PHOLD(p1); 521 522 /* 523 * Finish creating the child process. It will return via a different 524 * execution path later. (ie: directly into user mode) 525 */ 526 vm_fork(p1, p2, flags); 527 528 if (flags == (RFFDG | RFPROC)) { 529 cnt.v_forks++; 530 cnt.v_forkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 531 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 532 cnt.v_vforks++; 533 cnt.v_vforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 534 } else if (p1 == &proc0) { 535 cnt.v_kthreads++; 536 cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 537 } else { 538 cnt.v_rforks++; 539 cnt.v_rforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 540 } 541 542 /* 543 * Both processes are set up, now check if any loadable modules want 544 * to adjust anything. 545 * What if they have an error? XXX 546 */ 547 TAILQ_FOREACH(ep, &fork_list, next) { 548 (*ep->function)(p1, p2, flags); 549 } 550 551 /* 552 * If RFSTOPPED not requested, make child runnable and add to 553 * run queue. 554 */ 555 microtime(&(p2->p_stats->p_start)); 556 p2->p_acflag = AFORK; 557 if ((flags & RFSTOPPED) == 0) { 558 splhigh(); 559 mtx_lock_spin(&sched_lock); 560 p2->p_stat = SRUN; 561 setrunqueue(p2); 562 mtx_unlock_spin(&sched_lock); 563 spl0(); 564 } 565 566 /* 567 * Now can be swapped. 568 */ 569 PRELE(p1); 570 571 /* 572 * tell any interested parties about the new process 573 */ 574 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 575 576 /* 577 * Preserve synchronization semantics of vfork. If waiting for 578 * child to exec or exit, set P_PPWAIT on child, and sleep on our 579 * proc (in case of exit). 580 */ 581 while (p2->p_flag & P_PPWAIT) 582 tsleep(p1, PWAIT, "ppwait", 0); 583 584 /* 585 * Return child proc pointer to parent. 586 */ 587 *procp = p2; 588 return (0); 589 } 590 591 /* 592 * The next two functionms are general routines to handle adding/deleting 593 * items on the fork callout list. 594 * 595 * at_fork(): 596 * Take the arguments given and put them onto the fork callout list, 597 * However first make sure that it's not already there. 598 * Returns 0 on success or a standard error number. 599 */ 600 601 int 602 at_fork(function) 603 forklist_fn function; 604 { 605 struct forklist *ep; 606 607 #ifdef INVARIANTS 608 /* let the programmer know if he's been stupid */ 609 if (rm_at_fork(function)) 610 printf("WARNING: fork callout entry (%p) already present\n", 611 function); 612 #endif 613 ep = malloc(sizeof(*ep), M_ATFORK, M_NOWAIT); 614 if (ep == NULL) 615 return (ENOMEM); 616 ep->function = function; 617 TAILQ_INSERT_TAIL(&fork_list, ep, next); 618 return (0); 619 } 620 621 /* 622 * Scan the exit callout list for the given item and remove it.. 623 * Returns the number of items removed (0 or 1) 624 */ 625 626 int 627 rm_at_fork(function) 628 forklist_fn function; 629 { 630 struct forklist *ep; 631 632 TAILQ_FOREACH(ep, &fork_list, next) { 633 if (ep->function == function) { 634 TAILQ_REMOVE(&fork_list, ep, next); 635 free(ep, M_ATFORK); 636 return(1); 637 } 638 } 639 return (0); 640 } 641 642 /* 643 * Handle the return of a child process from fork1(). This function 644 * is called from the MD fork_trampoline() entry point. 645 */ 646 void 647 fork_exit(callout, arg, frame) 648 void (*callout)(void *, struct trapframe *); 649 void *arg; 650 struct trapframe *frame; 651 { 652 struct proc *p; 653 654 mtx_unlock_spin(&sched_lock); 655 /* 656 * XXX: We really shouldn't have to do this. 657 */ 658 enable_intr(); 659 660 #ifdef SMP 661 if (PCPU_GET(switchtime.tv_sec) == 0) 662 microuptime(PCPU_PTR(switchtime)); 663 PCPU_SET(switchticks, ticks); 664 #endif 665 666 /* 667 * cpu_set_fork_handler intercepts this function call to 668 * have this call a non-return function to stay in kernel mode. 669 * initproc has its own fork handler, but it does return. 670 */ 671 callout(arg, frame); 672 673 /* 674 * Check if a kernel thread misbehaved and returned from its main 675 * function. 676 */ 677 p = CURPROC; 678 if (p->p_flag & P_KTHREAD) { 679 mtx_lock(&Giant); 680 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 681 p->p_comm, p->p_pid); 682 kthread_exit(0); 683 } 684 mtx_assert(&Giant, MA_NOTOWNED); 685 } 686 687 /* 688 * Simplified back end of syscall(), used when returning from fork() 689 * directly into user mode. Giant is not held on entry, and must not 690 * be held on return. This function is passed in to fork_exit() as the 691 * first parameter and is called when returning to a new userland process. 692 */ 693 void 694 fork_return(p, frame) 695 struct proc *p; 696 struct trapframe *frame; 697 { 698 699 userret(p, frame, 0); 700 #ifdef KTRACE 701 if (KTRPOINT(p, KTR_SYSRET)) { 702 if (!mtx_owned(&Giant)) 703 mtx_lock(&Giant); 704 ktrsysret(p->p_tracep, SYS_fork, 0, 0); 705 } 706 #endif 707 if (mtx_owned(&Giant)) 708 mtx_unlock(&Giant); 709 mtx_assert(&Giant, MA_NOTOWNED); 710 } 711