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: src/sys/kern/kern_fork.c,v 1.72.2.14 2003/06/26 04:15:10 silby Exp $ 40 * $DragonFly: src/sys/kern/kern_fork.c,v 1.44 2005/11/14 18:50:05 dillon Exp $ 41 */ 42 43 #include "opt_ktrace.h" 44 45 #include <sys/param.h> 46 #include <sys/systm.h> 47 #include <sys/sysproto.h> 48 #include <sys/filedesc.h> 49 #include <sys/kernel.h> 50 #include <sys/sysctl.h> 51 #include <sys/malloc.h> 52 #include <sys/proc.h> 53 #include <sys/resourcevar.h> 54 #include <sys/vnode.h> 55 #include <sys/acct.h> 56 #include <sys/ktrace.h> 57 #include <sys/unistd.h> 58 #include <sys/jail.h> 59 #include <sys/caps.h> 60 61 #include <vm/vm.h> 62 #include <sys/lock.h> 63 #include <vm/pmap.h> 64 #include <vm/vm_map.h> 65 #include <vm/vm_extern.h> 66 #include <vm/vm_zone.h> 67 68 #include <sys/vmmeter.h> 69 #include <sys/user.h> 70 #include <sys/thread2.h> 71 72 static MALLOC_DEFINE(M_ATFORK, "atfork", "atfork callback"); 73 74 /* 75 * These are the stuctures used to create a callout list for things to do 76 * when forking a process 77 */ 78 struct forklist { 79 forklist_fn function; 80 TAILQ_ENTRY(forklist) next; 81 }; 82 83 TAILQ_HEAD(forklist_head, forklist); 84 static struct forklist_head fork_list = TAILQ_HEAD_INITIALIZER(fork_list); 85 86 int forksleep; /* Place for fork1() to sleep on. */ 87 88 /* ARGSUSED */ 89 int 90 fork(struct fork_args *uap) 91 { 92 struct lwp *lp = curthread->td_lwp; 93 struct proc *p2; 94 int error; 95 96 error = fork1(lp, RFFDG | RFPROC, &p2); 97 if (error == 0) { 98 start_forked_proc(lp, p2); 99 uap->sysmsg_fds[0] = p2->p_pid; 100 uap->sysmsg_fds[1] = 0; 101 } 102 return error; 103 } 104 105 /* ARGSUSED */ 106 int 107 vfork(struct vfork_args *uap) 108 { 109 struct lwp *lp = curthread->td_lwp; 110 struct proc *p2; 111 int error; 112 113 error = fork1(lp, RFFDG | RFPROC | RFPPWAIT | RFMEM, &p2); 114 if (error == 0) { 115 start_forked_proc(lp, p2); 116 uap->sysmsg_fds[0] = p2->p_pid; 117 uap->sysmsg_fds[1] = 0; 118 } 119 return error; 120 } 121 122 /* 123 * Handle rforks. An rfork may (1) operate on the current process without 124 * creating a new, (2) create a new process that shared the current process's 125 * vmspace, signals, and/or descriptors, or (3) create a new process that does 126 * not share these things (normal fork). 127 * 128 * Note that we only call start_forked_proc() if a new process is actually 129 * created. 130 * 131 * rfork { int flags } 132 */ 133 int 134 rfork(struct rfork_args *uap) 135 { 136 struct lwp *lp = curthread->td_lwp; 137 struct proc *p2; 138 int error; 139 140 if ((uap->flags & RFKERNELONLY) != 0) 141 return (EINVAL); 142 143 error = fork1(lp, uap->flags, &p2); 144 if (error == 0) { 145 if (p2) 146 start_forked_proc(lp, p2); 147 uap->sysmsg_fds[0] = p2 ? p2->p_pid : 0; 148 uap->sysmsg_fds[1] = 0; 149 } 150 return error; 151 } 152 153 154 int nprocs = 1; /* process 0 */ 155 static int nextpid = 0; 156 157 /* 158 * Random component to nextpid generation. We mix in a random factor to make 159 * it a little harder to predict. We sanity check the modulus value to avoid 160 * doing it in critical paths. Don't let it be too small or we pointlessly 161 * waste randomness entropy, and don't let it be impossibly large. Using a 162 * modulus that is too big causes a LOT more process table scans and slows 163 * down fork processing as the pidchecked caching is defeated. 164 */ 165 static int randompid = 0; 166 167 static int 168 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 169 { 170 int error, pid; 171 172 pid = randompid; 173 error = sysctl_handle_int(oidp, &pid, 0, req); 174 if (error || !req->newptr) 175 return (error); 176 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 177 pid = PID_MAX - 100; 178 else if (pid < 2) /* NOP */ 179 pid = 0; 180 else if (pid < 100) /* Make it reasonable */ 181 pid = 100; 182 randompid = pid; 183 return (error); 184 } 185 186 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 187 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 188 189 int 190 fork1(struct lwp *lp1, int flags, struct proc **procp) 191 { 192 struct proc *p1 = lp1->lwp_proc; 193 struct proc *p2, *pptr; 194 struct lwp *lp2; 195 uid_t uid; 196 struct proc *newproc; 197 int ok; 198 static int curfail = 0, pidchecked = 0; 199 static struct timeval lastfail; 200 struct forklist *ep; 201 struct filedesc_to_leader *fdtol; 202 203 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 204 return (EINVAL); 205 206 /* 207 * Here we don't create a new process, but we divorce 208 * certain parts of a process from itself. 209 */ 210 if ((flags & RFPROC) == 0) { 211 212 vm_fork(p1, 0, flags); 213 214 /* 215 * Close all file descriptors. 216 */ 217 if (flags & RFCFDG) { 218 struct filedesc *fdtmp; 219 fdtmp = fdinit(p1); 220 fdfree(p1); 221 p1->p_fd = fdtmp; 222 } 223 224 /* 225 * Unshare file descriptors (from parent.) 226 */ 227 if (flags & RFFDG) { 228 if (p1->p_fd->fd_refcnt > 1) { 229 struct filedesc *newfd; 230 newfd = fdcopy(p1); 231 fdfree(p1); 232 p1->p_fd = newfd; 233 } 234 } 235 *procp = NULL; 236 return (0); 237 } 238 239 /* 240 * Although process entries are dynamically created, we still keep 241 * a global limit on the maximum number we will create. Don't allow 242 * a nonprivileged user to use the last ten processes; don't let root 243 * exceed the limit. The variable nprocs is the current number of 244 * processes, maxproc is the limit. 245 */ 246 uid = p1->p_ucred->cr_ruid; 247 if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) { 248 if (ppsratecheck(&lastfail, &curfail, 1)) 249 printf("maxproc limit exceeded by uid %d, please " 250 "see tuning(7) and login.conf(5).\n", uid); 251 tsleep(&forksleep, 0, "fork", hz / 2); 252 return (EAGAIN); 253 } 254 /* 255 * Increment the nprocs resource before blocking can occur. There 256 * are hard-limits as to the number of processes that can run. 257 */ 258 nprocs++; 259 260 /* 261 * Increment the count of procs running with this uid. Don't allow 262 * a nonprivileged user to exceed their current limit. 263 */ 264 ok = chgproccnt(p1->p_ucred->cr_ruidinfo, 1, 265 (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0); 266 if (!ok) { 267 /* 268 * Back out the process count 269 */ 270 nprocs--; 271 if (ppsratecheck(&lastfail, &curfail, 1)) 272 printf("maxproc limit exceeded by uid %d, please " 273 "see tuning(7) and login.conf(5).\n", uid); 274 tsleep(&forksleep, 0, "fork", hz / 2); 275 return (EAGAIN); 276 } 277 278 /* Allocate new proc. */ 279 newproc = zalloc(proc_zone); 280 281 /* 282 * Setup linkage for kernel based threading XXX lwp 283 */ 284 if ((flags & RFTHREAD) != 0) { 285 newproc->p_peers = p1->p_peers; 286 p1->p_peers = newproc; 287 newproc->p_leader = p1->p_leader; 288 } else { 289 newproc->p_peers = 0; 290 newproc->p_leader = newproc; 291 } 292 293 newproc->p_wakeup = 0; 294 newproc->p_vmspace = NULL; 295 TAILQ_INIT(&newproc->p_lwp.lwp_sysmsgq); 296 LIST_INIT(&newproc->p_lwps); 297 298 /* XXX lwp */ 299 lp2 = &newproc->p_lwp; 300 lp2->lwp_proc = newproc; 301 lp2->lwp_tid = 0; 302 LIST_INSERT_HEAD(&newproc->p_lwps, lp2, lwp_list); 303 newproc->p_nthreads = 1; 304 305 /* 306 * Find an unused process ID. We remember a range of unused IDs 307 * ready to use (from nextpid+1 through pidchecked-1). 308 */ 309 nextpid++; 310 if (randompid) 311 nextpid += arc4random() % randompid; 312 retry: 313 /* 314 * If the process ID prototype has wrapped around, 315 * restart somewhat above 0, as the low-numbered procs 316 * tend to include daemons that don't exit. 317 */ 318 if (nextpid >= PID_MAX) { 319 nextpid = nextpid % PID_MAX; 320 if (nextpid < 100) 321 nextpid += 100; 322 pidchecked = 0; 323 } 324 if (nextpid >= pidchecked) { 325 int doingzomb = 0; 326 327 pidchecked = PID_MAX; 328 /* 329 * Scan the active and zombie procs to check whether this pid 330 * is in use. Remember the lowest pid that's greater 331 * than nextpid, so we can avoid checking for a while. 332 */ 333 p2 = LIST_FIRST(&allproc); 334 again: 335 for (; p2 != 0; p2 = LIST_NEXT(p2, p_list)) { 336 while (p2->p_pid == nextpid || 337 p2->p_pgrp->pg_id == nextpid || 338 p2->p_session->s_sid == nextpid) { 339 nextpid++; 340 if (nextpid >= pidchecked) 341 goto retry; 342 } 343 if (p2->p_pid > nextpid && pidchecked > p2->p_pid) 344 pidchecked = p2->p_pid; 345 if (p2->p_pgrp->pg_id > nextpid && 346 pidchecked > p2->p_pgrp->pg_id) 347 pidchecked = p2->p_pgrp->pg_id; 348 if (p2->p_session->s_sid > nextpid && 349 pidchecked > p2->p_session->s_sid) 350 pidchecked = p2->p_session->s_sid; 351 } 352 if (!doingzomb) { 353 doingzomb = 1; 354 p2 = LIST_FIRST(&zombproc); 355 goto again; 356 } 357 } 358 359 p2 = newproc; 360 p2->p_stat = SIDL; /* protect against others */ 361 p2->p_pid = nextpid; 362 LIST_INSERT_HEAD(&allproc, p2, p_list); 363 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 364 365 /* 366 * Make a proc table entry for the new process. 367 * Start by zeroing the section of proc that is zero-initialized, 368 * then copy the section that is copied directly from the parent. 369 */ 370 bzero(&p2->p_startzero, 371 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 372 bzero(&lp2->lwp_startzero, 373 (unsigned) ((caddr_t)&lp2->lwp_endzero - 374 (caddr_t)&lp2->lwp_startzero)); 375 bcopy(&p1->p_startcopy, &p2->p_startcopy, 376 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 377 bcopy(&p1->p_lwp.lwp_startcopy, &lp2->lwp_startcopy, 378 (unsigned) ((caddr_t)&lp2->lwp_endcopy - 379 (caddr_t)&lp2->lwp_startcopy)); 380 381 p2->p_aioinfo = NULL; 382 383 /* 384 * Duplicate sub-structures as needed. 385 * Increase reference counts on shared objects. 386 * The p_stats and p_sigacts substructs are set in vm_fork. 387 */ 388 p2->p_flag = 0; 389 if (p1->p_flag & P_PROFIL) 390 startprofclock(p2); 391 p2->p_ucred = crhold(p1->p_ucred); 392 393 if (jailed(p2->p_ucred)) 394 p2->p_flag |= P_JAILED; 395 396 if (p2->p_args) 397 p2->p_args->ar_ref++; 398 399 if (flags & RFSIGSHARE) { 400 p2->p_procsig = p1->p_procsig; 401 p2->p_procsig->ps_refcnt++; 402 if (p1->p_sigacts == &p1->p_addr->u_sigacts) { 403 struct sigacts *newsigacts; 404 405 /* Create the shared sigacts structure */ 406 MALLOC(newsigacts, struct sigacts *, 407 sizeof(struct sigacts), M_SUBPROC, M_WAITOK); 408 crit_enter(); 409 /* 410 * Set p_sigacts to the new shared structure. 411 * Note that this is updating p1->p_sigacts at the 412 * same time, since p_sigacts is just a pointer to 413 * the shared p_procsig->ps_sigacts. 414 */ 415 p2->p_sigacts = newsigacts; 416 bcopy(&p1->p_addr->u_sigacts, p2->p_sigacts, 417 sizeof(*p2->p_sigacts)); 418 *p2->p_sigacts = p1->p_addr->u_sigacts; 419 crit_exit(); 420 } 421 } else { 422 MALLOC(p2->p_procsig, struct procsig *, sizeof(struct procsig), 423 M_SUBPROC, M_WAITOK); 424 bcopy(p1->p_procsig, p2->p_procsig, sizeof(*p2->p_procsig)); 425 p2->p_procsig->ps_refcnt = 1; 426 p2->p_sigacts = NULL; /* finished in vm_fork() */ 427 } 428 if (flags & RFLINUXTHPN) 429 p2->p_sigparent = SIGUSR1; 430 else 431 p2->p_sigparent = SIGCHLD; 432 433 /* bump references to the text vnode (for procfs) */ 434 p2->p_textvp = p1->p_textvp; 435 if (p2->p_textvp) 436 vref(p2->p_textvp); 437 438 if (flags & RFCFDG) { 439 p2->p_fd = fdinit(p1); 440 fdtol = NULL; 441 } else if (flags & RFFDG) { 442 p2->p_fd = fdcopy(p1); 443 fdtol = NULL; 444 } else { 445 p2->p_fd = fdshare(p1); 446 if (p1->p_fdtol == NULL) 447 p1->p_fdtol = 448 filedesc_to_leader_alloc(NULL, 449 p1->p_leader); 450 if ((flags & RFTHREAD) != 0) { 451 /* 452 * Shared file descriptor table and 453 * shared process leaders. 454 */ 455 fdtol = p1->p_fdtol; 456 fdtol->fdl_refcount++; 457 } else { 458 /* 459 * Shared file descriptor table, and 460 * different process leaders 461 */ 462 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, p2); 463 } 464 } 465 p2->p_fdtol = fdtol; 466 467 /* 468 * If p_limit is still copy-on-write, bump refcnt, 469 * otherwise get a copy that won't be modified. 470 * (If PL_SHAREMOD is clear, the structure is shared 471 * copy-on-write.) 472 */ 473 if (p1->p_limit->p_lflags & PL_SHAREMOD) { 474 p2->p_limit = limcopy(p1->p_limit); 475 } else { 476 p2->p_limit = p1->p_limit; 477 p2->p_limit->p_refcnt++; 478 } 479 480 /* 481 * Preserve some more flags in subprocess. P_PROFIL has already 482 * been preserved. 483 */ 484 p2->p_flag |= p1->p_flag & (P_SUGID | P_ALTSTACK); 485 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 486 p2->p_flag |= P_CONTROLT; 487 if (flags & RFPPWAIT) 488 p2->p_flag |= P_PPWAIT; 489 490 /* 491 * Once we are on a pglist we may receive signals. XXX we might 492 * race a ^C being sent to the process group by not receiving it 493 * at all prior to this line. 494 */ 495 LIST_INSERT_AFTER(p1, p2, p_pglist); 496 497 /* 498 * Attach the new process to its parent. 499 * 500 * If RFNOWAIT is set, the newly created process becomes a child 501 * of init. This effectively disassociates the child from the 502 * parent. 503 */ 504 if (flags & RFNOWAIT) 505 pptr = initproc; 506 else 507 pptr = p1; 508 p2->p_pptr = pptr; 509 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 510 LIST_INIT(&p2->p_children); 511 varsymset_init(&p2->p_varsymset, &p1->p_varsymset); 512 callout_init(&p2->p_ithandle); 513 514 #ifdef KTRACE 515 /* 516 * Copy traceflag and tracefile if enabled. If not inherited, 517 * these were zeroed above but we still could have a trace race 518 * so make sure p2's p_tracep is NULL. 519 */ 520 if ((p1->p_traceflag & KTRFAC_INHERIT) && p2->p_tracep == NULL) { 521 p2->p_traceflag = p1->p_traceflag; 522 if ((p2->p_tracep = p1->p_tracep) != NULL) 523 vref(p2->p_tracep); 524 } 525 #endif 526 527 /* 528 * Inherit the scheduler and initialize scheduler-related fields. 529 * Set cpbase to the last timeout that occured (not the upcoming 530 * timeout). 531 */ 532 p2->p_usched = p1->p_usched; 533 lp2->lwp_cpbase = mycpu->gd_schedclock.time - 534 mycpu->gd_schedclock.periodic; 535 p2->p_usched->heuristic_forking(&p1->p_lwp, lp2); 536 537 /* 538 * This begins the section where we must prevent the parent 539 * from being swapped. 540 */ 541 PHOLD(p1); 542 543 /* 544 * Finish creating the child process. It will return via a different 545 * execution path later. (ie: directly into user mode) 546 */ 547 vm_fork(p1, p2, flags); 548 caps_fork(p1, p2, flags); 549 550 if (flags == (RFFDG | RFPROC)) { 551 mycpu->gd_cnt.v_forks++; 552 mycpu->gd_cnt.v_forkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 553 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 554 mycpu->gd_cnt.v_vforks++; 555 mycpu->gd_cnt.v_vforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 556 } else if (p1 == &proc0) { 557 mycpu->gd_cnt.v_kthreads++; 558 mycpu->gd_cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 559 } else { 560 mycpu->gd_cnt.v_rforks++; 561 mycpu->gd_cnt.v_rforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 562 } 563 564 /* 565 * Both processes are set up, now check if any loadable modules want 566 * to adjust anything. 567 * What if they have an error? XXX 568 */ 569 TAILQ_FOREACH(ep, &fork_list, next) { 570 (*ep->function)(p1, p2, flags); 571 } 572 573 /* 574 * Set the start time. Note that the process is not runnable. The 575 * caller is responsible for making it runnable. 576 */ 577 microtime(&p2->p_start); 578 p2->p_acflag = AFORK; 579 580 /* 581 * tell any interested parties about the new process 582 */ 583 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 584 585 /* 586 * Return child proc pointer to parent. 587 */ 588 *procp = p2; 589 return (0); 590 } 591 592 /* 593 * The next two functionms are general routines to handle adding/deleting 594 * items on the fork callout list. 595 * 596 * at_fork(): 597 * Take the arguments given and put them onto the fork callout list, 598 * However first make sure that it's not already there. 599 * Returns 0 on success or a standard error number. 600 */ 601 int 602 at_fork(forklist_fn function) 603 { 604 struct forklist *ep; 605 606 #ifdef INVARIANTS 607 /* let the programmer know if he's been stupid */ 608 if (rm_at_fork(function)) { 609 printf("WARNING: fork callout entry (%p) already present\n", 610 function); 611 } 612 #endif 613 ep = malloc(sizeof(*ep), M_ATFORK, M_WAITOK|M_ZERO); 614 ep->function = function; 615 TAILQ_INSERT_TAIL(&fork_list, ep, next); 616 return (0); 617 } 618 619 /* 620 * Scan the exit callout list for the given item and remove it.. 621 * Returns the number of items removed (0 or 1) 622 */ 623 int 624 rm_at_fork(forklist_fn function) 625 { 626 struct forklist *ep; 627 628 TAILQ_FOREACH(ep, &fork_list, next) { 629 if (ep->function == function) { 630 TAILQ_REMOVE(&fork_list, ep, next); 631 free(ep, M_ATFORK); 632 return(1); 633 } 634 } 635 return (0); 636 } 637 638 /* 639 * Add a forked process to the run queue after any remaining setup, such 640 * as setting the fork handler, has been completed. 641 */ 642 void 643 start_forked_proc(struct lwp *lp1, struct proc *p2) 644 { 645 struct lwp *lp2; 646 647 KKASSERT(p2 != NULL && p2->p_nthreads == 1); 648 649 lp2 = LIST_FIRST(&p2->p_lwps); 650 651 /* 652 * Move from SIDL to RUN queue, and activate the process's thread. 653 * Activation of the thread effectively makes the process "a" 654 * current process, so we do not setrunqueue(). 655 * 656 * YYY setrunqueue works here but we should clean up the trampoline 657 * code so we just schedule the LWKT thread and let the trampoline 658 * deal with the userland scheduler on return to userland. 659 */ 660 KASSERT(p2->p_stat == SIDL, 661 ("cannot start forked process, bad status: %p", p2)); 662 p2->p_usched->resetpriority(lp2); 663 crit_enter(); 664 p2->p_stat = SRUN; 665 p2->p_usched->setrunqueue(lp2); 666 crit_exit(); 667 668 /* 669 * Now can be swapped. 670 */ 671 PRELE(lp1->lwp_proc); 672 673 /* 674 * Preserve synchronization semantics of vfork. If waiting for 675 * child to exec or exit, set P_PPWAIT on child, and sleep on our 676 * proc (in case of exit). 677 */ 678 while (p2->p_flag & P_PPWAIT) 679 tsleep(lp1->lwp_proc, 0, "ppwait", 0); 680 } 681