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 1.68 2007/04/29 18:25:34 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/thread2.h> 70 #include <sys/signal2.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 static struct lwp *lwp_fork(struct lwp *, struct proc *, int flags); 87 88 int forksleep; /* Place for fork1() to sleep on. */ 89 90 /* ARGSUSED */ 91 int 92 sys_fork(struct fork_args *uap) 93 { 94 struct lwp *lp = curthread->td_lwp; 95 struct proc *p2; 96 int error; 97 98 error = fork1(lp, RFFDG | RFPROC | RFPGLOCK, &p2); 99 if (error == 0) { 100 start_forked_proc(lp, p2); 101 uap->sysmsg_fds[0] = p2->p_pid; 102 uap->sysmsg_fds[1] = 0; 103 } 104 return error; 105 } 106 107 /* ARGSUSED */ 108 int 109 sys_vfork(struct vfork_args *uap) 110 { 111 struct lwp *lp = curthread->td_lwp; 112 struct proc *p2; 113 int error; 114 115 error = fork1(lp, RFFDG | RFPROC | RFPPWAIT | RFMEM | RFPGLOCK, &p2); 116 if (error == 0) { 117 start_forked_proc(lp, p2); 118 uap->sysmsg_fds[0] = p2->p_pid; 119 uap->sysmsg_fds[1] = 0; 120 } 121 return error; 122 } 123 124 /* 125 * Handle rforks. An rfork may (1) operate on the current process without 126 * creating a new, (2) create a new process that shared the current process's 127 * vmspace, signals, and/or descriptors, or (3) create a new process that does 128 * not share these things (normal fork). 129 * 130 * Note that we only call start_forked_proc() if a new process is actually 131 * created. 132 * 133 * rfork { int flags } 134 */ 135 int 136 sys_rfork(struct rfork_args *uap) 137 { 138 struct lwp *lp = curthread->td_lwp; 139 struct proc *p2; 140 int error; 141 142 if ((uap->flags & RFKERNELONLY) != 0) 143 return (EINVAL); 144 145 error = fork1(lp, uap->flags | RFPGLOCK, &p2); 146 if (error == 0) { 147 if (p2) 148 start_forked_proc(lp, p2); 149 uap->sysmsg_fds[0] = p2 ? p2->p_pid : 0; 150 uap->sysmsg_fds[1] = 0; 151 } 152 return error; 153 } 154 155 int 156 sys_lwp_create(struct lwp_create_args *uap) 157 { 158 struct proc *p = curproc; 159 struct lwp *lp; 160 struct lwp_params params; 161 int error; 162 163 error = copyin(uap->params, ¶ms, sizeof(params)); 164 if (error) 165 goto fail2; 166 167 lp = lwp_fork(curthread->td_lwp, p, RFPROC); 168 error = cpu_prepare_lwp(lp, ¶ms); 169 if (params.tid1 != NULL && 170 (error = copyout(&lp->lwp_tid, params.tid1, sizeof(lp->lwp_tid)))) 171 goto fail; 172 if (params.tid2 != NULL && 173 (error = copyout(&lp->lwp_tid, params.tid2, sizeof(lp->lwp_tid)))) 174 goto fail; 175 176 /* 177 * Now schedule the new lwp. 178 */ 179 p->p_usched->resetpriority(lp); 180 crit_enter(); 181 lp->lwp_stat = LSRUN; 182 p->p_usched->setrunqueue(lp); 183 crit_exit(); 184 185 return (0); 186 187 fail: 188 --p->p_nthreads; 189 LIST_REMOVE(lp, lwp_list); 190 /* lwp_dispose expects an exited lwp, and a held proc */ 191 lp->lwp_flag |= LWP_WEXIT; 192 lp->lwp_thread->td_flags |= TDF_EXITING; 193 PHOLD(p); 194 lwp_dispose(lp); 195 fail2: 196 return (error); 197 } 198 199 int nprocs = 1; /* process 0 */ 200 201 int 202 fork1(struct lwp *lp1, int flags, struct proc **procp) 203 { 204 struct proc *p1 = lp1->lwp_proc; 205 struct proc *p2, *pptr; 206 struct pgrp *pgrp; 207 uid_t uid; 208 int ok, error; 209 static int curfail = 0; 210 static struct timeval lastfail; 211 struct forklist *ep; 212 struct filedesc_to_leader *fdtol; 213 214 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 215 return (EINVAL); 216 217 /* 218 * Here we don't create a new process, but we divorce 219 * certain parts of a process from itself. 220 */ 221 if ((flags & RFPROC) == 0) { 222 /* 223 * This kind of stunt does not work anymore if 224 * there are native threads (lwps) running 225 */ 226 if (p1->p_nthreads != 1) 227 return (EINVAL); 228 229 vm_fork(p1, 0, flags); 230 231 /* 232 * Close all file descriptors. 233 */ 234 if (flags & RFCFDG) { 235 struct filedesc *fdtmp; 236 fdtmp = fdinit(p1); 237 fdfree(p1); 238 p1->p_fd = fdtmp; 239 } 240 241 /* 242 * Unshare file descriptors (from parent.) 243 */ 244 if (flags & RFFDG) { 245 if (p1->p_fd->fd_refcnt > 1) { 246 struct filedesc *newfd; 247 newfd = fdcopy(p1); 248 fdfree(p1); 249 p1->p_fd = newfd; 250 } 251 } 252 *procp = NULL; 253 return (0); 254 } 255 256 /* 257 * Interlock against process group signal delivery. If signals 258 * are pending after the interlock is obtained we have to restart 259 * the system call to process the signals. If we don't the child 260 * can miss a pgsignal (such as ^C) sent during the fork. 261 * 262 * We can't use CURSIG() here because it will process any STOPs 263 * and cause the process group lock to be held indefinitely. If 264 * a STOP occurs, the fork will be restarted after the CONT. 265 */ 266 error = 0; 267 pgrp = NULL; 268 if ((flags & RFPGLOCK) && (pgrp = p1->p_pgrp) != NULL) { 269 lockmgr(&pgrp->pg_lock, LK_SHARED); 270 if (CURSIGNB(lp1)) { 271 error = ERESTART; 272 goto done; 273 } 274 } 275 276 /* 277 * Although process entries are dynamically created, we still keep 278 * a global limit on the maximum number we will create. Don't allow 279 * a nonprivileged user to use the last ten processes; don't let root 280 * exceed the limit. The variable nprocs is the current number of 281 * processes, maxproc is the limit. 282 */ 283 uid = p1->p_ucred->cr_ruid; 284 if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) { 285 if (ppsratecheck(&lastfail, &curfail, 1)) 286 kprintf("maxproc limit exceeded by uid %d, please " 287 "see tuning(7) and login.conf(5).\n", uid); 288 tsleep(&forksleep, 0, "fork", hz / 2); 289 error = EAGAIN; 290 goto done; 291 } 292 /* 293 * Increment the nprocs resource before blocking can occur. There 294 * are hard-limits as to the number of processes that can run. 295 */ 296 nprocs++; 297 298 /* 299 * Increment the count of procs running with this uid. Don't allow 300 * a nonprivileged user to exceed their current limit. 301 */ 302 ok = chgproccnt(p1->p_ucred->cr_ruidinfo, 1, 303 (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0); 304 if (!ok) { 305 /* 306 * Back out the process count 307 */ 308 nprocs--; 309 if (ppsratecheck(&lastfail, &curfail, 1)) 310 kprintf("maxproc limit exceeded by uid %d, please " 311 "see tuning(7) and login.conf(5).\n", uid); 312 tsleep(&forksleep, 0, "fork", hz / 2); 313 error = EAGAIN; 314 goto done; 315 } 316 317 /* Allocate new proc. */ 318 p2 = zalloc(proc_zone); 319 bzero(p2, sizeof(*p2)); 320 321 /* 322 * Setup linkage for kernel based threading XXX lwp 323 */ 324 if (flags & RFTHREAD) { 325 p2->p_peers = p1->p_peers; 326 p1->p_peers = p2; 327 p2->p_leader = p1->p_leader; 328 } else { 329 p2->p_leader = p2; 330 } 331 332 LIST_INIT(&p2->p_lwps); 333 334 /* 335 * Setting the state to SIDL protects the partially initialized 336 * process once it starts getting hooked into the rest of the system. 337 */ 338 p2->p_stat = SIDL; 339 proc_add_allproc(p2); 340 341 /* 342 * Make a proc table entry for the new process. 343 * The whole structure was zeroed above, so copy the section that is 344 * copied directly from the parent. 345 */ 346 bcopy(&p1->p_startcopy, &p2->p_startcopy, 347 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 348 349 /* 350 * Duplicate sub-structures as needed. 351 * Increase reference counts on shared objects. 352 */ 353 if (p1->p_flag & P_PROFIL) 354 startprofclock(p2); 355 p2->p_ucred = crhold(p1->p_ucred); 356 357 if (jailed(p2->p_ucred)) 358 p2->p_flag |= P_JAILED; 359 360 if (p2->p_args) 361 p2->p_args->ar_ref++; 362 363 p2->p_usched = p1->p_usched; 364 365 if (flags & RFSIGSHARE) { 366 p2->p_sigacts = p1->p_sigacts; 367 p2->p_sigacts->ps_refcnt++; 368 } else { 369 p2->p_sigacts = (struct sigacts *)kmalloc(sizeof(*p2->p_sigacts), 370 M_SUBPROC, M_WAITOK); 371 bcopy(p1->p_sigacts, p2->p_sigacts, sizeof(*p2->p_sigacts)); 372 p2->p_sigacts->ps_refcnt = 1; 373 } 374 if (flags & RFLINUXTHPN) 375 p2->p_sigparent = SIGUSR1; 376 else 377 p2->p_sigparent = SIGCHLD; 378 379 /* bump references to the text vnode (for procfs) */ 380 p2->p_textvp = p1->p_textvp; 381 if (p2->p_textvp) 382 vref(p2->p_textvp); 383 384 /* 385 * Handle file descriptors 386 */ 387 if (flags & RFCFDG) { 388 p2->p_fd = fdinit(p1); 389 fdtol = NULL; 390 } else if (flags & RFFDG) { 391 p2->p_fd = fdcopy(p1); 392 fdtol = NULL; 393 } else { 394 p2->p_fd = fdshare(p1); 395 if (p1->p_fdtol == NULL) 396 p1->p_fdtol = 397 filedesc_to_leader_alloc(NULL, 398 p1->p_leader); 399 if ((flags & RFTHREAD) != 0) { 400 /* 401 * Shared file descriptor table and 402 * shared process leaders. 403 */ 404 fdtol = p1->p_fdtol; 405 fdtol->fdl_refcount++; 406 } else { 407 /* 408 * Shared file descriptor table, and 409 * different process leaders 410 */ 411 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, p2); 412 } 413 } 414 p2->p_fdtol = fdtol; 415 p2->p_limit = plimit_fork(p1->p_limit); 416 417 /* 418 * Preserve some more flags in subprocess. P_PROFIL has already 419 * been preserved. 420 */ 421 p2->p_flag |= p1->p_flag & P_SUGID; 422 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 423 p2->p_flag |= P_CONTROLT; 424 if (flags & RFPPWAIT) 425 p2->p_flag |= P_PPWAIT; 426 427 /* 428 * Inherit the virtual kernel structure (allows a virtual kernel 429 * to fork to simulate multiple cpus). 430 */ 431 if (p1->p_vkernel) 432 vkernel_inherit(p1, p2); 433 434 /* 435 * Once we are on a pglist we may receive signals. XXX we might 436 * race a ^C being sent to the process group by not receiving it 437 * at all prior to this line. 438 */ 439 LIST_INSERT_AFTER(p1, p2, p_pglist); 440 441 /* 442 * Attach the new process to its parent. 443 * 444 * If RFNOWAIT is set, the newly created process becomes a child 445 * of init. This effectively disassociates the child from the 446 * parent. 447 */ 448 if (flags & RFNOWAIT) 449 pptr = initproc; 450 else 451 pptr = p1; 452 p2->p_pptr = pptr; 453 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 454 LIST_INIT(&p2->p_children); 455 varsymset_init(&p2->p_varsymset, &p1->p_varsymset); 456 callout_init(&p2->p_ithandle); 457 458 #ifdef KTRACE 459 /* 460 * Copy traceflag and tracefile if enabled. If not inherited, 461 * these were zeroed above but we still could have a trace race 462 * so make sure p2's p_tracenode is NULL. 463 */ 464 if ((p1->p_traceflag & KTRFAC_INHERIT) && p2->p_tracenode == NULL) { 465 p2->p_traceflag = p1->p_traceflag; 466 p2->p_tracenode = ktrinherit(p1->p_tracenode); 467 } 468 #endif 469 470 /* 471 * This begins the section where we must prevent the parent 472 * from being swapped. 473 * 474 * Gets PRELE'd in the caller in start_forked_proc(). 475 */ 476 PHOLD(p1); 477 478 vm_fork(p1, p2, flags); 479 480 /* 481 * Create the first lwp associated with the new proc. 482 * It will return via a different execution path later, directly 483 * into userland, after it was put on the runq by 484 * start_forked_proc(). 485 */ 486 lwp_fork(lp1, p2, flags); 487 488 if (flags == (RFFDG | RFPROC)) { 489 mycpu->gd_cnt.v_forks++; 490 mycpu->gd_cnt.v_forkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 491 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 492 mycpu->gd_cnt.v_vforks++; 493 mycpu->gd_cnt.v_vforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 494 } else if (p1 == &proc0) { 495 mycpu->gd_cnt.v_kthreads++; 496 mycpu->gd_cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 497 } else { 498 mycpu->gd_cnt.v_rforks++; 499 mycpu->gd_cnt.v_rforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 500 } 501 502 /* 503 * Both processes are set up, now check if any loadable modules want 504 * to adjust anything. 505 * What if they have an error? XXX 506 */ 507 TAILQ_FOREACH(ep, &fork_list, next) { 508 (*ep->function)(p1, p2, flags); 509 } 510 511 /* 512 * Set the start time. Note that the process is not runnable. The 513 * caller is responsible for making it runnable. 514 */ 515 microtime(&p2->p_start); 516 p2->p_acflag = AFORK; 517 518 /* 519 * tell any interested parties about the new process 520 */ 521 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 522 523 /* 524 * Return child proc pointer to parent. 525 */ 526 *procp = p2; 527 done: 528 if (pgrp) 529 lockmgr(&pgrp->pg_lock, LK_RELEASE); 530 return (error); 531 } 532 533 static struct lwp * 534 lwp_fork(struct lwp *origlp, struct proc *destproc, int flags) 535 { 536 struct lwp *lp; 537 struct thread *td; 538 lwpid_t tid; 539 540 /* 541 * We need to prevent wrap-around collisions. 542 * Until we have a nice tid allocator, we need to 543 * start searching for free tids once we wrap around. 544 * 545 * XXX give me a nicer allocator 546 */ 547 if (destproc->p_lasttid + 1 <= 0) { 548 tid = 0; 549 restart: 550 FOREACH_LWP_IN_PROC(lp, destproc) { 551 if (lp->lwp_tid != tid) 552 continue; 553 /* tids match, search next. */ 554 tid++; 555 /* 556 * Wait -- the whole tid space is depleted? 557 * Impossible. 558 */ 559 if (tid <= 0) 560 panic("lwp_fork: All tids depleted?!"); 561 goto restart; 562 } 563 /* When we come here, the tid is not occupied */ 564 } else { 565 tid = destproc->p_lasttid++; 566 } 567 568 lp = zalloc(lwp_zone); 569 bzero(lp, sizeof(*lp)); 570 lp->lwp_proc = destproc; 571 lp->lwp_tid = tid; 572 LIST_INSERT_HEAD(&destproc->p_lwps, lp, lwp_list); 573 destproc->p_nthreads++; 574 lp->lwp_stat = LSRUN; 575 bcopy(&origlp->lwp_startcopy, &lp->lwp_startcopy, 576 (unsigned) ((caddr_t)&lp->lwp_endcopy - 577 (caddr_t)&lp->lwp_startcopy)); 578 lp->lwp_flag |= origlp->lwp_flag & LWP_ALTSTACK; 579 /* 580 * Set cpbase to the last timeout that occured (not the upcoming 581 * timeout). 582 * 583 * A critical section is required since a timer IPI can update 584 * scheduler specific data. 585 */ 586 crit_enter(); 587 lp->lwp_cpbase = mycpu->gd_schedclock.time - 588 mycpu->gd_schedclock.periodic; 589 destproc->p_usched->heuristic_forking(origlp, lp); 590 crit_exit(); 591 592 td = lwkt_alloc_thread(NULL, LWKT_THREAD_STACK, -1, 0); 593 lp->lwp_thread = td; 594 td->td_proc = destproc; 595 td->td_lwp = lp; 596 td->td_switch = cpu_heavy_switch; 597 #ifdef SMP 598 KKASSERT(td->td_mpcount == 1); 599 #endif 600 lwkt_setpri(td, TDPRI_KERN_USER); 601 lwkt_set_comm(td, "%s", destproc->p_comm); 602 603 /* 604 * cpu_fork will copy and update the pcb, set up the kernel stack, 605 * and make the child ready to run. 606 */ 607 cpu_fork(origlp, lp, flags); 608 caps_fork(origlp->lwp_thread, lp->lwp_thread); 609 610 return (lp); 611 } 612 613 /* 614 * The next two functionms are general routines to handle adding/deleting 615 * items on the fork callout list. 616 * 617 * at_fork(): 618 * Take the arguments given and put them onto the fork callout list, 619 * However first make sure that it's not already there. 620 * Returns 0 on success or a standard error number. 621 */ 622 int 623 at_fork(forklist_fn function) 624 { 625 struct forklist *ep; 626 627 #ifdef INVARIANTS 628 /* let the programmer know if he's been stupid */ 629 if (rm_at_fork(function)) { 630 kprintf("WARNING: fork callout entry (%p) already present\n", 631 function); 632 } 633 #endif 634 ep = kmalloc(sizeof(*ep), M_ATFORK, M_WAITOK|M_ZERO); 635 ep->function = function; 636 TAILQ_INSERT_TAIL(&fork_list, ep, next); 637 return (0); 638 } 639 640 /* 641 * Scan the exit callout list for the given item and remove it.. 642 * Returns the number of items removed (0 or 1) 643 */ 644 int 645 rm_at_fork(forklist_fn function) 646 { 647 struct forklist *ep; 648 649 TAILQ_FOREACH(ep, &fork_list, next) { 650 if (ep->function == function) { 651 TAILQ_REMOVE(&fork_list, ep, next); 652 kfree(ep, M_ATFORK); 653 return(1); 654 } 655 } 656 return (0); 657 } 658 659 /* 660 * Add a forked process to the run queue after any remaining setup, such 661 * as setting the fork handler, has been completed. 662 */ 663 void 664 start_forked_proc(struct lwp *lp1, struct proc *p2) 665 { 666 struct lwp *lp2 = ONLY_LWP_IN_PROC(p2); 667 668 /* 669 * Move from SIDL to RUN queue, and activate the process's thread. 670 * Activation of the thread effectively makes the process "a" 671 * current process, so we do not setrunqueue(). 672 * 673 * YYY setrunqueue works here but we should clean up the trampoline 674 * code so we just schedule the LWKT thread and let the trampoline 675 * deal with the userland scheduler on return to userland. 676 */ 677 KASSERT(p2->p_stat == SIDL, 678 ("cannot start forked process, bad status: %p", p2)); 679 p2->p_usched->resetpriority(lp2); 680 crit_enter(); 681 p2->p_stat = SACTIVE; 682 lp2->lwp_stat = LSRUN; 683 p2->p_usched->setrunqueue(lp2); 684 crit_exit(); 685 686 /* 687 * Now can be swapped. 688 */ 689 PRELE(lp1->lwp_proc); 690 691 /* 692 * Preserve synchronization semantics of vfork. If waiting for 693 * child to exec or exit, set P_PPWAIT on child, and sleep on our 694 * proc (in case of exit). 695 */ 696 while (p2->p_flag & P_PPWAIT) 697 tsleep(lp1->lwp_proc, 0, "ppwait", 0); 698 } 699