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 1.77 2008/05/18 20:02:02 nth 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 67 #include <sys/vmmeter.h> 68 #include <sys/thread2.h> 69 #include <sys/signal2.h> 70 #include <sys/spinlock2.h> 71 72 #include <sys/dsched.h> 73 74 static MALLOC_DEFINE(M_ATFORK, "atfork", "atfork callback"); 75 76 /* 77 * These are the stuctures used to create a callout list for things to do 78 * when forking a process 79 */ 80 struct forklist { 81 forklist_fn function; 82 TAILQ_ENTRY(forklist) next; 83 }; 84 85 TAILQ_HEAD(forklist_head, forklist); 86 static struct forklist_head fork_list = TAILQ_HEAD_INITIALIZER(fork_list); 87 88 static struct lwp *lwp_fork(struct lwp *, struct proc *, int flags); 89 90 int forksleep; /* Place for fork1() to sleep on. */ 91 92 /* 93 * Red-Black tree support for LWPs 94 */ 95 96 static int 97 rb_lwp_compare(struct lwp *lp1, struct lwp *lp2) 98 { 99 if (lp1->lwp_tid < lp2->lwp_tid) 100 return(-1); 101 if (lp1->lwp_tid > lp2->lwp_tid) 102 return(1); 103 return(0); 104 } 105 106 RB_GENERATE2(lwp_rb_tree, lwp, u.lwp_rbnode, rb_lwp_compare, lwpid_t, lwp_tid); 107 108 /* 109 * Fork system call 110 * 111 * MPALMOSTSAFE 112 */ 113 int 114 sys_fork(struct fork_args *uap) 115 { 116 struct lwp *lp = curthread->td_lwp; 117 struct proc *p2; 118 int error; 119 120 error = fork1(lp, RFFDG | RFPROC | RFPGLOCK, &p2); 121 if (error == 0) { 122 start_forked_proc(lp, p2); 123 uap->sysmsg_fds[0] = p2->p_pid; 124 uap->sysmsg_fds[1] = 0; 125 } 126 return error; 127 } 128 129 /* 130 * MPALMOSTSAFE 131 */ 132 int 133 sys_vfork(struct vfork_args *uap) 134 { 135 struct lwp *lp = curthread->td_lwp; 136 struct proc *p2; 137 int error; 138 139 error = fork1(lp, RFFDG | RFPROC | RFPPWAIT | RFMEM | RFPGLOCK, &p2); 140 if (error == 0) { 141 start_forked_proc(lp, p2); 142 uap->sysmsg_fds[0] = p2->p_pid; 143 uap->sysmsg_fds[1] = 0; 144 } 145 return error; 146 } 147 148 /* 149 * Handle rforks. An rfork may (1) operate on the current process without 150 * creating a new, (2) create a new process that shared the current process's 151 * vmspace, signals, and/or descriptors, or (3) create a new process that does 152 * not share these things (normal fork). 153 * 154 * Note that we only call start_forked_proc() if a new process is actually 155 * created. 156 * 157 * rfork { int flags } 158 * 159 * MPALMOSTSAFE 160 */ 161 int 162 sys_rfork(struct rfork_args *uap) 163 { 164 struct lwp *lp = curthread->td_lwp; 165 struct proc *p2; 166 int error; 167 168 if ((uap->flags & RFKERNELONLY) != 0) 169 return (EINVAL); 170 171 error = fork1(lp, uap->flags | RFPGLOCK, &p2); 172 if (error == 0) { 173 if (p2) 174 start_forked_proc(lp, p2); 175 uap->sysmsg_fds[0] = p2 ? p2->p_pid : 0; 176 uap->sysmsg_fds[1] = 0; 177 } 178 return error; 179 } 180 181 /* 182 * MPALMOSTSAFE 183 */ 184 int 185 sys_lwp_create(struct lwp_create_args *uap) 186 { 187 struct proc *p = curproc; 188 struct lwp *lp; 189 struct lwp_params params; 190 int error; 191 192 error = copyin(uap->params, ¶ms, sizeof(params)); 193 if (error) 194 goto fail2; 195 196 lwkt_gettoken(&p->p_token); 197 plimit_lwp_fork(p); /* force exclusive access */ 198 lp = lwp_fork(curthread->td_lwp, p, RFPROC); 199 error = cpu_prepare_lwp(lp, ¶ms); 200 if (params.tid1 != NULL && 201 (error = copyout(&lp->lwp_tid, params.tid1, sizeof(lp->lwp_tid)))) 202 goto fail; 203 if (params.tid2 != NULL && 204 (error = copyout(&lp->lwp_tid, params.tid2, sizeof(lp->lwp_tid)))) 205 goto fail; 206 207 /* 208 * Now schedule the new lwp. 209 */ 210 p->p_usched->resetpriority(lp); 211 crit_enter(); 212 lp->lwp_stat = LSRUN; 213 p->p_usched->setrunqueue(lp); 214 crit_exit(); 215 lwkt_reltoken(&p->p_token); 216 217 return (0); 218 219 fail: 220 lwp_rb_tree_RB_REMOVE(&p->p_lwp_tree, lp); 221 --p->p_nthreads; 222 /* lwp_dispose expects an exited lwp, and a held proc */ 223 lp->lwp_flag |= LWP_WEXIT; 224 lp->lwp_thread->td_flags |= TDF_EXITING; 225 PHOLD(p); 226 lwp_dispose(lp); 227 lwkt_reltoken(&p->p_token); 228 fail2: 229 return (error); 230 } 231 232 int nprocs = 1; /* process 0 */ 233 234 int 235 fork1(struct lwp *lp1, int flags, struct proc **procp) 236 { 237 struct proc *p1 = lp1->lwp_proc; 238 struct proc *p2, *pptr; 239 struct pgrp *p1grp; 240 struct pgrp *plkgrp; 241 uid_t uid; 242 int ok, error; 243 static int curfail = 0; 244 static struct timeval lastfail; 245 struct forklist *ep; 246 struct filedesc_to_leader *fdtol; 247 248 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 249 return (EINVAL); 250 251 lwkt_gettoken(&p1->p_token); 252 plkgrp = NULL; 253 254 /* 255 * Here we don't create a new process, but we divorce 256 * certain parts of a process from itself. 257 */ 258 if ((flags & RFPROC) == 0) { 259 /* 260 * This kind of stunt does not work anymore if 261 * there are native threads (lwps) running 262 */ 263 if (p1->p_nthreads != 1) { 264 error = EINVAL; 265 goto done; 266 } 267 268 vm_fork(p1, 0, flags); 269 270 /* 271 * Close all file descriptors. 272 */ 273 if (flags & RFCFDG) { 274 struct filedesc *fdtmp; 275 fdtmp = fdinit(p1); 276 fdfree(p1, fdtmp); 277 } 278 279 /* 280 * Unshare file descriptors (from parent.) 281 */ 282 if (flags & RFFDG) { 283 if (p1->p_fd->fd_refcnt > 1) { 284 struct filedesc *newfd; 285 newfd = fdcopy(p1); 286 fdfree(p1, newfd); 287 } 288 } 289 *procp = NULL; 290 error = 0; 291 goto done; 292 } 293 294 /* 295 * Interlock against process group signal delivery. If signals 296 * are pending after the interlock is obtained we have to restart 297 * the system call to process the signals. If we don't the child 298 * can miss a pgsignal (such as ^C) sent during the fork. 299 * 300 * We can't use CURSIG() here because it will process any STOPs 301 * and cause the process group lock to be held indefinitely. If 302 * a STOP occurs, the fork will be restarted after the CONT. 303 */ 304 p1grp = p1->p_pgrp; 305 if ((flags & RFPGLOCK) && (plkgrp = p1->p_pgrp) != NULL) { 306 pgref(plkgrp); 307 lockmgr(&plkgrp->pg_lock, LK_SHARED); 308 if (CURSIG_NOBLOCK(lp1)) { 309 error = ERESTART; 310 goto done; 311 } 312 } 313 314 /* 315 * Although process entries are dynamically created, we still keep 316 * a global limit on the maximum number we will create. Don't allow 317 * a nonprivileged user to use the last ten processes; don't let root 318 * exceed the limit. The variable nprocs is the current number of 319 * processes, maxproc is the limit. 320 */ 321 uid = lp1->lwp_thread->td_ucred->cr_ruid; 322 if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) { 323 if (ppsratecheck(&lastfail, &curfail, 1)) 324 kprintf("maxproc limit exceeded by uid %d, please " 325 "see tuning(7) and login.conf(5).\n", uid); 326 tsleep(&forksleep, 0, "fork", hz / 2); 327 error = EAGAIN; 328 goto done; 329 } 330 /* 331 * Increment the nprocs resource before blocking can occur. There 332 * are hard-limits as to the number of processes that can run. 333 */ 334 nprocs++; 335 336 /* 337 * Increment the count of procs running with this uid. Don't allow 338 * a nonprivileged user to exceed their current limit. 339 */ 340 ok = chgproccnt(lp1->lwp_thread->td_ucred->cr_ruidinfo, 1, 341 (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0); 342 if (!ok) { 343 /* 344 * Back out the process count 345 */ 346 nprocs--; 347 if (ppsratecheck(&lastfail, &curfail, 1)) 348 kprintf("maxproc limit exceeded by uid %d, please " 349 "see tuning(7) and login.conf(5).\n", uid); 350 tsleep(&forksleep, 0, "fork", hz / 2); 351 error = EAGAIN; 352 goto done; 353 } 354 355 /* Allocate new proc. */ 356 p2 = kmalloc(sizeof(struct proc), M_PROC, M_WAITOK|M_ZERO); 357 358 /* 359 * Setup linkage for kernel based threading XXX lwp 360 */ 361 if (flags & RFTHREAD) { 362 p2->p_peers = p1->p_peers; 363 p1->p_peers = p2; 364 p2->p_leader = p1->p_leader; 365 } else { 366 p2->p_leader = p2; 367 } 368 369 RB_INIT(&p2->p_lwp_tree); 370 spin_init(&p2->p_spin); 371 lwkt_token_init(&p2->p_token, "iproc"); 372 p2->p_lasttid = -1; /* first tid will be 0 */ 373 374 /* 375 * Setting the state to SIDL protects the partially initialized 376 * process once it starts getting hooked into the rest of the system. 377 */ 378 p2->p_stat = SIDL; 379 proc_add_allproc(p2); 380 381 /* 382 * Make a proc table entry for the new process. 383 * The whole structure was zeroed above, so copy the section that is 384 * copied directly from the parent. 385 */ 386 bcopy(&p1->p_startcopy, &p2->p_startcopy, 387 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 388 389 /* 390 * Duplicate sub-structures as needed. Increase reference counts 391 * on shared objects. 392 * 393 * NOTE: because we are now on the allproc list it is possible for 394 * other consumers to gain temporary references to p2 395 * (p2->p_lock can change). 396 */ 397 if (p1->p_flag & P_PROFIL) 398 startprofclock(p2); 399 p2->p_ucred = crhold(lp1->lwp_thread->td_ucred); 400 401 if (jailed(p2->p_ucred)) 402 p2->p_flag |= P_JAILED; 403 404 if (p2->p_args) 405 p2->p_args->ar_ref++; 406 407 p2->p_usched = p1->p_usched; 408 /* XXX: verify copy of the secondary iosched stuff */ 409 dsched_new_proc(p2); 410 411 if (flags & RFSIGSHARE) { 412 p2->p_sigacts = p1->p_sigacts; 413 p2->p_sigacts->ps_refcnt++; 414 } else { 415 p2->p_sigacts = (struct sigacts *)kmalloc(sizeof(*p2->p_sigacts), 416 M_SUBPROC, M_WAITOK); 417 bcopy(p1->p_sigacts, p2->p_sigacts, sizeof(*p2->p_sigacts)); 418 p2->p_sigacts->ps_refcnt = 1; 419 } 420 if (flags & RFLINUXTHPN) 421 p2->p_sigparent = SIGUSR1; 422 else 423 p2->p_sigparent = SIGCHLD; 424 425 /* bump references to the text vnode (for procfs) */ 426 p2->p_textvp = p1->p_textvp; 427 if (p2->p_textvp) 428 vref(p2->p_textvp); 429 430 /* copy namecache handle to the text file */ 431 if (p1->p_textnch.mount) 432 cache_copy(&p1->p_textnch, &p2->p_textnch); 433 434 /* 435 * Handle file descriptors 436 */ 437 if (flags & RFCFDG) { 438 p2->p_fd = fdinit(p1); 439 fdtol = NULL; 440 } else if (flags & RFFDG) { 441 p2->p_fd = fdcopy(p1); 442 fdtol = NULL; 443 } else { 444 p2->p_fd = fdshare(p1); 445 if (p1->p_fdtol == NULL) { 446 lwkt_gettoken(&p1->p_token); 447 p1->p_fdtol = 448 filedesc_to_leader_alloc(NULL, 449 p1->p_leader); 450 lwkt_reltoken(&p1->p_token); 451 } 452 if ((flags & RFTHREAD) != 0) { 453 /* 454 * Shared file descriptor table and 455 * shared process leaders. 456 */ 457 fdtol = p1->p_fdtol; 458 fdtol->fdl_refcount++; 459 } else { 460 /* 461 * Shared file descriptor table, and 462 * different process leaders 463 */ 464 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, p2); 465 } 466 } 467 p2->p_fdtol = fdtol; 468 p2->p_limit = plimit_fork(p1); 469 470 /* 471 * Preserve some more flags in subprocess. P_PROFIL has already 472 * been preserved. 473 */ 474 p2->p_flag |= p1->p_flag & P_SUGID; 475 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 476 p2->p_flag |= P_CONTROLT; 477 if (flags & RFPPWAIT) 478 p2->p_flag |= P_PPWAIT; 479 480 /* 481 * Inherit the virtual kernel structure (allows a virtual kernel 482 * to fork to simulate multiple cpus). 483 */ 484 if (p1->p_vkernel) 485 vkernel_inherit(p1, p2); 486 487 /* 488 * Once we are on a pglist we may receive signals. XXX we might 489 * race a ^C being sent to the process group by not receiving it 490 * at all prior to this line. 491 */ 492 pgref(p1grp); 493 lwkt_gettoken(&p1grp->pg_token); 494 LIST_INSERT_AFTER(p1, p2, p_pglist); 495 lwkt_reltoken(&p1grp->pg_token); 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_INIT(&p2->p_children); 510 511 lwkt_gettoken(&pptr->p_token); 512 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 513 lwkt_reltoken(&pptr->p_token); 514 515 varsymset_init(&p2->p_varsymset, &p1->p_varsymset); 516 callout_init(&p2->p_ithandle); 517 518 #ifdef KTRACE 519 /* 520 * Copy traceflag and tracefile if enabled. If not inherited, 521 * these were zeroed above but we still could have a trace race 522 * so make sure p2's p_tracenode is NULL. 523 */ 524 if ((p1->p_traceflag & KTRFAC_INHERIT) && p2->p_tracenode == NULL) { 525 p2->p_traceflag = p1->p_traceflag; 526 p2->p_tracenode = ktrinherit(p1->p_tracenode); 527 } 528 #endif 529 530 /* 531 * This begins the section where we must prevent the parent 532 * from being swapped. 533 * 534 * Gets PRELE'd in the caller in start_forked_proc(). 535 */ 536 PHOLD(p1); 537 538 vm_fork(p1, p2, flags); 539 540 /* 541 * Create the first lwp associated with the new proc. 542 * It will return via a different execution path later, directly 543 * into userland, after it was put on the runq by 544 * start_forked_proc(). 545 */ 546 lwp_fork(lp1, p2, flags); 547 548 if (flags == (RFFDG | RFPROC | RFPGLOCK)) { 549 mycpu->gd_cnt.v_forks++; 550 mycpu->gd_cnt.v_forkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 551 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM | RFPGLOCK)) { 552 mycpu->gd_cnt.v_vforks++; 553 mycpu->gd_cnt.v_vforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 554 } else if (p1 == &proc0) { 555 mycpu->gd_cnt.v_kthreads++; 556 mycpu->gd_cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 557 } else { 558 mycpu->gd_cnt.v_rforks++; 559 mycpu->gd_cnt.v_rforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 560 } 561 562 /* 563 * Both processes are set up, now check if any loadable modules want 564 * to adjust anything. 565 * What if they have an error? XXX 566 */ 567 TAILQ_FOREACH(ep, &fork_list, next) { 568 (*ep->function)(p1, p2, flags); 569 } 570 571 /* 572 * Set the start time. Note that the process is not runnable. The 573 * caller is responsible for making it runnable. 574 */ 575 microtime(&p2->p_start); 576 p2->p_acflag = AFORK; 577 578 /* 579 * tell any interested parties about the new process 580 */ 581 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 582 583 /* 584 * Return child proc pointer to parent. 585 */ 586 *procp = p2; 587 error = 0; 588 done: 589 lwkt_reltoken(&p1->p_token); 590 if (plkgrp) { 591 lockmgr(&plkgrp->pg_lock, LK_RELEASE); 592 pgrel(plkgrp); 593 } 594 return (error); 595 } 596 597 static struct lwp * 598 lwp_fork(struct lwp *origlp, struct proc *destproc, int flags) 599 { 600 struct lwp *lp; 601 struct thread *td; 602 603 lp = kmalloc(sizeof(struct lwp), M_LWP, M_WAITOK|M_ZERO); 604 605 lp->lwp_proc = destproc; 606 lp->lwp_vmspace = destproc->p_vmspace; 607 lp->lwp_stat = LSRUN; 608 bcopy(&origlp->lwp_startcopy, &lp->lwp_startcopy, 609 (unsigned) ((caddr_t)&lp->lwp_endcopy - 610 (caddr_t)&lp->lwp_startcopy)); 611 lp->lwp_flag |= origlp->lwp_flag & LWP_ALTSTACK; 612 /* 613 * Set cpbase to the last timeout that occured (not the upcoming 614 * timeout). 615 * 616 * A critical section is required since a timer IPI can update 617 * scheduler specific data. 618 */ 619 crit_enter(); 620 lp->lwp_cpbase = mycpu->gd_schedclock.time - 621 mycpu->gd_schedclock.periodic; 622 destproc->p_usched->heuristic_forking(origlp, lp); 623 crit_exit(); 624 lp->lwp_cpumask &= usched_mastermask; 625 626 /* 627 * Assign a TID to the lp. Loop until the insert succeeds (returns 628 * NULL). 629 */ 630 lp->lwp_tid = destproc->p_lasttid; 631 do { 632 if (++lp->lwp_tid < 0) 633 lp->lwp_tid = 1; 634 } while (lwp_rb_tree_RB_INSERT(&destproc->p_lwp_tree, lp) != NULL); 635 destproc->p_lasttid = lp->lwp_tid; 636 destproc->p_nthreads++; 637 638 td = lwkt_alloc_thread(NULL, LWKT_THREAD_STACK, -1, 0); 639 lp->lwp_thread = td; 640 td->td_proc = destproc; 641 td->td_lwp = lp; 642 td->td_switch = cpu_heavy_switch; 643 lwkt_setpri(td, TDPRI_KERN_USER); 644 lwkt_set_comm(td, "%s", destproc->p_comm); 645 646 /* 647 * cpu_fork will copy and update the pcb, set up the kernel stack, 648 * and make the child ready to run. 649 */ 650 cpu_fork(origlp, lp, flags); 651 caps_fork(origlp->lwp_thread, lp->lwp_thread); 652 kqueue_init(&lp->lwp_kqueue, destproc->p_fd); 653 654 return (lp); 655 } 656 657 /* 658 * The next two functionms are general routines to handle adding/deleting 659 * items on the fork callout list. 660 * 661 * at_fork(): 662 * Take the arguments given and put them onto the fork callout list, 663 * However first make sure that it's not already there. 664 * Returns 0 on success or a standard error number. 665 */ 666 int 667 at_fork(forklist_fn function) 668 { 669 struct forklist *ep; 670 671 #ifdef INVARIANTS 672 /* let the programmer know if he's been stupid */ 673 if (rm_at_fork(function)) { 674 kprintf("WARNING: fork callout entry (%p) already present\n", 675 function); 676 } 677 #endif 678 ep = kmalloc(sizeof(*ep), M_ATFORK, M_WAITOK|M_ZERO); 679 ep->function = function; 680 TAILQ_INSERT_TAIL(&fork_list, ep, next); 681 return (0); 682 } 683 684 /* 685 * Scan the exit callout list for the given item and remove it.. 686 * Returns the number of items removed (0 or 1) 687 */ 688 int 689 rm_at_fork(forklist_fn function) 690 { 691 struct forklist *ep; 692 693 TAILQ_FOREACH(ep, &fork_list, next) { 694 if (ep->function == function) { 695 TAILQ_REMOVE(&fork_list, ep, next); 696 kfree(ep, M_ATFORK); 697 return(1); 698 } 699 } 700 return (0); 701 } 702 703 /* 704 * Add a forked process to the run queue after any remaining setup, such 705 * as setting the fork handler, has been completed. 706 */ 707 void 708 start_forked_proc(struct lwp *lp1, struct proc *p2) 709 { 710 struct lwp *lp2 = ONLY_LWP_IN_PROC(p2); 711 712 /* 713 * Move from SIDL to RUN queue, and activate the process's thread. 714 * Activation of the thread effectively makes the process "a" 715 * current process, so we do not setrunqueue(). 716 * 717 * YYY setrunqueue works here but we should clean up the trampoline 718 * code so we just schedule the LWKT thread and let the trampoline 719 * deal with the userland scheduler on return to userland. 720 */ 721 KASSERT(p2->p_stat == SIDL, 722 ("cannot start forked process, bad status: %p", p2)); 723 p2->p_usched->resetpriority(lp2); 724 crit_enter(); 725 p2->p_stat = SACTIVE; 726 lp2->lwp_stat = LSRUN; 727 p2->p_usched->setrunqueue(lp2); 728 crit_exit(); 729 730 /* 731 * Now can be swapped. 732 */ 733 PRELE(lp1->lwp_proc); 734 735 /* 736 * Preserve synchronization semantics of vfork. If waiting for 737 * child to exec or exit, set P_PPWAIT on child, and sleep on our 738 * proc (in case of exit). 739 */ 740 while (p2->p_flag & P_PPWAIT) 741 tsleep(lp1->lwp_proc, 0, "ppwait", 0); 742 } 743