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/refcount.h> 69 #include <sys/thread2.h> 70 #include <sys/signal2.h> 71 #include <sys/spinlock2.h> 72 73 #include <sys/dsched.h> 74 75 static MALLOC_DEFINE(M_ATFORK, "atfork", "atfork callback"); 76 77 /* 78 * These are the stuctures used to create a callout list for things to do 79 * when forking a process 80 */ 81 struct forklist { 82 forklist_fn function; 83 TAILQ_ENTRY(forklist) next; 84 }; 85 86 TAILQ_HEAD(forklist_head, forklist); 87 static struct forklist_head fork_list = TAILQ_HEAD_INITIALIZER(fork_list); 88 89 static struct lwp *lwp_fork(struct lwp *, struct proc *, int flags); 90 91 int forksleep; /* Place for fork1() to sleep on. */ 92 93 /* 94 * Red-Black tree support for LWPs 95 */ 96 97 static int 98 rb_lwp_compare(struct lwp *lp1, struct lwp *lp2) 99 { 100 if (lp1->lwp_tid < lp2->lwp_tid) 101 return(-1); 102 if (lp1->lwp_tid > lp2->lwp_tid) 103 return(1); 104 return(0); 105 } 106 107 RB_GENERATE2(lwp_rb_tree, lwp, u.lwp_rbnode, rb_lwp_compare, lwpid_t, lwp_tid); 108 109 /* 110 * Fork system call 111 * 112 * MPALMOSTSAFE 113 */ 114 int 115 sys_fork(struct fork_args *uap) 116 { 117 struct lwp *lp = curthread->td_lwp; 118 struct proc *p2; 119 int error; 120 121 error = fork1(lp, RFFDG | RFPROC | RFPGLOCK, &p2); 122 if (error == 0) { 123 start_forked_proc(lp, p2); 124 uap->sysmsg_fds[0] = p2->p_pid; 125 uap->sysmsg_fds[1] = 0; 126 } 127 return error; 128 } 129 130 /* 131 * MPALMOSTSAFE 132 */ 133 int 134 sys_vfork(struct vfork_args *uap) 135 { 136 struct lwp *lp = curthread->td_lwp; 137 struct proc *p2; 138 int error; 139 140 error = fork1(lp, RFFDG | RFPROC | RFPPWAIT | RFMEM | RFPGLOCK, &p2); 141 if (error == 0) { 142 start_forked_proc(lp, p2); 143 uap->sysmsg_fds[0] = p2->p_pid; 144 uap->sysmsg_fds[1] = 0; 145 } 146 return error; 147 } 148 149 /* 150 * Handle rforks. An rfork may (1) operate on the current process without 151 * creating a new, (2) create a new process that shared the current process's 152 * vmspace, signals, and/or descriptors, or (3) create a new process that does 153 * not share these things (normal fork). 154 * 155 * Note that we only call start_forked_proc() if a new process is actually 156 * created. 157 * 158 * rfork { int flags } 159 * 160 * MPALMOSTSAFE 161 */ 162 int 163 sys_rfork(struct rfork_args *uap) 164 { 165 struct lwp *lp = curthread->td_lwp; 166 struct proc *p2; 167 int error; 168 169 if ((uap->flags & RFKERNELONLY) != 0) 170 return (EINVAL); 171 172 error = fork1(lp, uap->flags | RFPGLOCK, &p2); 173 if (error == 0) { 174 if (p2) 175 start_forked_proc(lp, p2); 176 uap->sysmsg_fds[0] = p2 ? p2->p_pid : 0; 177 uap->sysmsg_fds[1] = 0; 178 } 179 return error; 180 } 181 182 /* 183 * MPALMOSTSAFE 184 */ 185 int 186 sys_lwp_create(struct lwp_create_args *uap) 187 { 188 struct proc *p = curproc; 189 struct lwp *lp; 190 struct lwp_params params; 191 int error; 192 193 error = copyin(uap->params, ¶ms, sizeof(params)); 194 if (error) 195 goto fail2; 196 197 lwkt_gettoken(&p->p_token); 198 plimit_lwp_fork(p); /* force exclusive access */ 199 lp = lwp_fork(curthread->td_lwp, p, RFPROC); 200 error = cpu_prepare_lwp(lp, ¶ms); 201 if (params.tid1 != NULL && 202 (error = copyout(&lp->lwp_tid, params.tid1, sizeof(lp->lwp_tid)))) 203 goto fail; 204 if (params.tid2 != NULL && 205 (error = copyout(&lp->lwp_tid, params.tid2, sizeof(lp->lwp_tid)))) 206 goto fail; 207 208 /* 209 * Now schedule the new lwp. 210 */ 211 p->p_usched->resetpriority(lp); 212 crit_enter(); 213 lp->lwp_stat = LSRUN; 214 p->p_usched->setrunqueue(lp); 215 crit_exit(); 216 lwkt_reltoken(&p->p_token); 217 218 return (0); 219 220 fail: 221 lwp_rb_tree_RB_REMOVE(&p->p_lwp_tree, lp); 222 --p->p_nthreads; 223 /* lwp_dispose expects an exited lwp, and a held proc */ 224 lp->lwp_flag |= LWP_WEXIT; 225 lp->lwp_thread->td_flags |= TDF_EXITING; 226 PHOLD(p); 227 lwp_dispose(lp); 228 lwkt_reltoken(&p->p_token); 229 fail2: 230 return (error); 231 } 232 233 int nprocs = 1; /* process 0 */ 234 235 int 236 fork1(struct lwp *lp1, int flags, struct proc **procp) 237 { 238 struct proc *p1 = lp1->lwp_proc; 239 struct proc *p2, *pptr; 240 struct pgrp *p1grp; 241 struct pgrp *plkgrp; 242 uid_t uid; 243 int ok, error; 244 static int curfail = 0; 245 static struct timeval lastfail; 246 struct forklist *ep; 247 struct filedesc_to_leader *fdtol; 248 249 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 250 return (EINVAL); 251 252 lwkt_gettoken(&p1->p_token); 253 plkgrp = NULL; 254 255 /* 256 * Here we don't create a new process, but we divorce 257 * certain parts of a process from itself. 258 */ 259 if ((flags & RFPROC) == 0) { 260 /* 261 * This kind of stunt does not work anymore if 262 * there are native threads (lwps) running 263 */ 264 if (p1->p_nthreads != 1) { 265 error = EINVAL; 266 goto done; 267 } 268 269 vm_fork(p1, 0, flags); 270 271 /* 272 * Close all file descriptors. 273 */ 274 if (flags & RFCFDG) { 275 struct filedesc *fdtmp; 276 fdtmp = fdinit(p1); 277 fdfree(p1, fdtmp); 278 } 279 280 /* 281 * Unshare file descriptors (from parent.) 282 */ 283 if (flags & RFFDG) { 284 if (p1->p_fd->fd_refcnt > 1) { 285 struct filedesc *newfd; 286 error = fdcopy(p1, &newfd); 287 if (error != 0) { 288 error = ENOMEM; 289 goto done; 290 } 291 fdfree(p1, newfd); 292 } 293 } 294 *procp = NULL; 295 error = 0; 296 goto done; 297 } 298 299 /* 300 * Interlock against process group signal delivery. If signals 301 * are pending after the interlock is obtained we have to restart 302 * the system call to process the signals. If we don't the child 303 * can miss a pgsignal (such as ^C) sent during the fork. 304 * 305 * We can't use CURSIG() here because it will process any STOPs 306 * and cause the process group lock to be held indefinitely. If 307 * a STOP occurs, the fork will be restarted after the CONT. 308 */ 309 p1grp = p1->p_pgrp; 310 if ((flags & RFPGLOCK) && (plkgrp = p1->p_pgrp) != NULL) { 311 pgref(plkgrp); 312 lockmgr(&plkgrp->pg_lock, LK_SHARED); 313 if (CURSIG_NOBLOCK(lp1)) { 314 error = ERESTART; 315 goto done; 316 } 317 } 318 319 /* 320 * Although process entries are dynamically created, we still keep 321 * a global limit on the maximum number we will create. Don't allow 322 * a nonprivileged user to use the last ten processes; don't let root 323 * exceed the limit. The variable nprocs is the current number of 324 * processes, maxproc is the limit. 325 */ 326 uid = lp1->lwp_thread->td_ucred->cr_ruid; 327 if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) { 328 if (ppsratecheck(&lastfail, &curfail, 1)) 329 kprintf("maxproc limit exceeded by uid %d, please " 330 "see tuning(7) and login.conf(5).\n", uid); 331 tsleep(&forksleep, 0, "fork", hz / 2); 332 error = EAGAIN; 333 goto done; 334 } 335 /* 336 * Increment the nprocs resource before blocking can occur. There 337 * are hard-limits as to the number of processes that can run. 338 */ 339 nprocs++; 340 341 /* 342 * Increment the count of procs running with this uid. Don't allow 343 * a nonprivileged user to exceed their current limit. 344 */ 345 ok = chgproccnt(lp1->lwp_thread->td_ucred->cr_ruidinfo, 1, 346 (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0); 347 if (!ok) { 348 /* 349 * Back out the process count 350 */ 351 nprocs--; 352 if (ppsratecheck(&lastfail, &curfail, 1)) 353 kprintf("maxproc limit exceeded by uid %d, please " 354 "see tuning(7) and login.conf(5).\n", uid); 355 tsleep(&forksleep, 0, "fork", hz / 2); 356 error = EAGAIN; 357 goto done; 358 } 359 360 /* Allocate new proc. */ 361 p2 = kmalloc(sizeof(struct proc), M_PROC, M_WAITOK|M_ZERO); 362 363 /* 364 * Setup linkage for kernel based threading XXX lwp 365 */ 366 if (flags & RFTHREAD) { 367 p2->p_peers = p1->p_peers; 368 p1->p_peers = p2; 369 p2->p_leader = p1->p_leader; 370 } else { 371 p2->p_leader = p2; 372 } 373 374 RB_INIT(&p2->p_lwp_tree); 375 spin_init(&p2->p_spin); 376 lwkt_token_init(&p2->p_token, "iproc"); 377 p2->p_lasttid = -1; /* first tid will be 0 */ 378 379 /* 380 * Setting the state to SIDL protects the partially initialized 381 * process once it starts getting hooked into the rest of the system. 382 */ 383 p2->p_stat = SIDL; 384 proc_add_allproc(p2); 385 386 /* 387 * Make a proc table entry for the new process. 388 * The whole structure was zeroed above, so copy the section that is 389 * copied directly from the parent. 390 */ 391 bcopy(&p1->p_startcopy, &p2->p_startcopy, 392 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 393 394 /* 395 * Duplicate sub-structures as needed. Increase reference counts 396 * on shared objects. 397 * 398 * NOTE: because we are now on the allproc list it is possible for 399 * other consumers to gain temporary references to p2 400 * (p2->p_lock can change). 401 */ 402 if (p1->p_flag & P_PROFIL) 403 startprofclock(p2); 404 p2->p_ucred = crhold(lp1->lwp_thread->td_ucred); 405 406 if (jailed(p2->p_ucred)) 407 p2->p_flag |= P_JAILED; 408 409 if (p2->p_args) 410 refcount_acquire(&p2->p_args->ar_ref); 411 412 p2->p_usched = p1->p_usched; 413 /* XXX: verify copy of the secondary iosched stuff */ 414 dsched_new_proc(p2); 415 416 if (flags & RFSIGSHARE) { 417 p2->p_sigacts = p1->p_sigacts; 418 refcount_acquire(&p2->p_sigacts->ps_refcnt); 419 } else { 420 p2->p_sigacts = kmalloc(sizeof(*p2->p_sigacts), 421 M_SUBPROC, M_WAITOK); 422 bcopy(p1->p_sigacts, p2->p_sigacts, sizeof(*p2->p_sigacts)); 423 refcount_init(&p2->p_sigacts->ps_refcnt, 1); 424 } 425 if (flags & RFLINUXTHPN) 426 p2->p_sigparent = SIGUSR1; 427 else 428 p2->p_sigparent = SIGCHLD; 429 430 /* bump references to the text vnode (for procfs) */ 431 p2->p_textvp = p1->p_textvp; 432 if (p2->p_textvp) 433 vref(p2->p_textvp); 434 435 /* copy namecache handle to the text file */ 436 if (p1->p_textnch.mount) 437 cache_copy(&p1->p_textnch, &p2->p_textnch); 438 439 /* 440 * Handle file descriptors 441 */ 442 if (flags & RFCFDG) { 443 p2->p_fd = fdinit(p1); 444 fdtol = NULL; 445 } else if (flags & RFFDG) { 446 error = fdcopy(p1, &p2->p_fd); 447 if (error != 0) { 448 error = ENOMEM; 449 goto done; 450 } 451 fdtol = NULL; 452 } else { 453 p2->p_fd = fdshare(p1); 454 if (p1->p_fdtol == NULL) { 455 lwkt_gettoken(&p1->p_token); 456 p1->p_fdtol = 457 filedesc_to_leader_alloc(NULL, 458 p1->p_leader); 459 lwkt_reltoken(&p1->p_token); 460 } 461 if ((flags & RFTHREAD) != 0) { 462 /* 463 * Shared file descriptor table and 464 * shared process leaders. 465 */ 466 fdtol = p1->p_fdtol; 467 fdtol->fdl_refcount++; 468 } else { 469 /* 470 * Shared file descriptor table, and 471 * different process leaders 472 */ 473 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, p2); 474 } 475 } 476 p2->p_fdtol = fdtol; 477 p2->p_limit = plimit_fork(p1); 478 479 /* 480 * Preserve some more flags in subprocess. P_PROFIL has already 481 * been preserved. 482 */ 483 p2->p_flag |= p1->p_flag & P_SUGID; 484 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 485 p2->p_flag |= P_CONTROLT; 486 if (flags & RFPPWAIT) 487 p2->p_flag |= P_PPWAIT; 488 489 /* 490 * Inherit the virtual kernel structure (allows a virtual kernel 491 * to fork to simulate multiple cpus). 492 */ 493 if (p1->p_vkernel) 494 vkernel_inherit(p1, p2); 495 496 /* 497 * Once we are on a pglist we may receive signals. XXX we might 498 * race a ^C being sent to the process group by not receiving it 499 * at all prior to this line. 500 */ 501 pgref(p1grp); 502 lwkt_gettoken(&p1grp->pg_token); 503 LIST_INSERT_AFTER(p1, p2, p_pglist); 504 lwkt_reltoken(&p1grp->pg_token); 505 506 /* 507 * Attach the new process to its parent. 508 * 509 * If RFNOWAIT is set, the newly created process becomes a child 510 * of init. This effectively disassociates the child from the 511 * parent. 512 */ 513 if (flags & RFNOWAIT) 514 pptr = initproc; 515 else 516 pptr = p1; 517 p2->p_pptr = pptr; 518 LIST_INIT(&p2->p_children); 519 520 lwkt_gettoken(&pptr->p_token); 521 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 522 lwkt_reltoken(&pptr->p_token); 523 524 varsymset_init(&p2->p_varsymset, &p1->p_varsymset); 525 callout_init(&p2->p_ithandle); 526 527 #ifdef KTRACE 528 /* 529 * Copy traceflag and tracefile if enabled. If not inherited, 530 * these were zeroed above but we still could have a trace race 531 * so make sure p2's p_tracenode is NULL. 532 */ 533 if ((p1->p_traceflag & KTRFAC_INHERIT) && p2->p_tracenode == NULL) { 534 p2->p_traceflag = p1->p_traceflag; 535 p2->p_tracenode = ktrinherit(p1->p_tracenode); 536 } 537 #endif 538 539 /* 540 * This begins the section where we must prevent the parent 541 * from being swapped. 542 * 543 * Gets PRELE'd in the caller in start_forked_proc(). 544 */ 545 PHOLD(p1); 546 547 vm_fork(p1, p2, flags); 548 549 /* 550 * Create the first lwp associated with the new proc. 551 * It will return via a different execution path later, directly 552 * into userland, after it was put on the runq by 553 * start_forked_proc(). 554 */ 555 lwp_fork(lp1, p2, flags); 556 557 if (flags == (RFFDG | RFPROC | RFPGLOCK)) { 558 mycpu->gd_cnt.v_forks++; 559 mycpu->gd_cnt.v_forkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 560 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM | RFPGLOCK)) { 561 mycpu->gd_cnt.v_vforks++; 562 mycpu->gd_cnt.v_vforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 563 } else if (p1 == &proc0) { 564 mycpu->gd_cnt.v_kthreads++; 565 mycpu->gd_cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 566 } else { 567 mycpu->gd_cnt.v_rforks++; 568 mycpu->gd_cnt.v_rforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 569 } 570 571 /* 572 * Both processes are set up, now check if any loadable modules want 573 * to adjust anything. 574 * What if they have an error? XXX 575 */ 576 TAILQ_FOREACH(ep, &fork_list, next) { 577 (*ep->function)(p1, p2, flags); 578 } 579 580 /* 581 * Set the start time. Note that the process is not runnable. The 582 * caller is responsible for making it runnable. 583 */ 584 microtime(&p2->p_start); 585 p2->p_acflag = AFORK; 586 587 /* 588 * tell any interested parties about the new process 589 */ 590 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 591 592 /* 593 * Return child proc pointer to parent. 594 */ 595 *procp = p2; 596 error = 0; 597 done: 598 lwkt_reltoken(&p1->p_token); 599 if (plkgrp) { 600 lockmgr(&plkgrp->pg_lock, LK_RELEASE); 601 pgrel(plkgrp); 602 } 603 return (error); 604 } 605 606 static struct lwp * 607 lwp_fork(struct lwp *origlp, struct proc *destproc, int flags) 608 { 609 struct lwp *lp; 610 struct thread *td; 611 612 lp = kmalloc(sizeof(struct lwp), M_LWP, M_WAITOK|M_ZERO); 613 614 lp->lwp_proc = destproc; 615 lp->lwp_vmspace = destproc->p_vmspace; 616 lp->lwp_stat = LSRUN; 617 bcopy(&origlp->lwp_startcopy, &lp->lwp_startcopy, 618 (unsigned) ((caddr_t)&lp->lwp_endcopy - 619 (caddr_t)&lp->lwp_startcopy)); 620 lp->lwp_flag |= origlp->lwp_flag & LWP_ALTSTACK; 621 /* 622 * Set cpbase to the last timeout that occured (not the upcoming 623 * timeout). 624 * 625 * A critical section is required since a timer IPI can update 626 * scheduler specific data. 627 */ 628 crit_enter(); 629 lp->lwp_cpbase = mycpu->gd_schedclock.time - 630 mycpu->gd_schedclock.periodic; 631 destproc->p_usched->heuristic_forking(origlp, lp); 632 crit_exit(); 633 lp->lwp_cpumask &= usched_mastermask; 634 635 td = lwkt_alloc_thread(NULL, LWKT_THREAD_STACK, -1, 0); 636 lp->lwp_thread = td; 637 td->td_proc = destproc; 638 td->td_lwp = lp; 639 td->td_switch = cpu_heavy_switch; 640 lwkt_setpri(td, TDPRI_KERN_USER); 641 lwkt_set_comm(td, "%s", destproc->p_comm); 642 643 /* 644 * cpu_fork will copy and update the pcb, set up the kernel stack, 645 * and make the child ready to run. 646 */ 647 cpu_fork(origlp, lp, flags); 648 caps_fork(origlp->lwp_thread, lp->lwp_thread); 649 kqueue_init(&lp->lwp_kqueue, destproc->p_fd); 650 651 /* 652 * Assign a TID to the lp. Loop until the insert succeeds (returns 653 * NULL). 654 */ 655 lp->lwp_tid = destproc->p_lasttid; 656 do { 657 if (++lp->lwp_tid < 0) 658 lp->lwp_tid = 1; 659 } while (lwp_rb_tree_RB_INSERT(&destproc->p_lwp_tree, lp) != NULL); 660 destproc->p_lasttid = lp->lwp_tid; 661 destproc->p_nthreads++; 662 663 664 return (lp); 665 } 666 667 /* 668 * The next two functionms are general routines to handle adding/deleting 669 * items on the fork callout list. 670 * 671 * at_fork(): 672 * Take the arguments given and put them onto the fork callout list, 673 * However first make sure that it's not already there. 674 * Returns 0 on success or a standard error number. 675 */ 676 int 677 at_fork(forklist_fn function) 678 { 679 struct forklist *ep; 680 681 #ifdef INVARIANTS 682 /* let the programmer know if he's been stupid */ 683 if (rm_at_fork(function)) { 684 kprintf("WARNING: fork callout entry (%p) already present\n", 685 function); 686 } 687 #endif 688 ep = kmalloc(sizeof(*ep), M_ATFORK, M_WAITOK|M_ZERO); 689 ep->function = function; 690 TAILQ_INSERT_TAIL(&fork_list, ep, next); 691 return (0); 692 } 693 694 /* 695 * Scan the exit callout list for the given item and remove it.. 696 * Returns the number of items removed (0 or 1) 697 */ 698 int 699 rm_at_fork(forklist_fn function) 700 { 701 struct forklist *ep; 702 703 TAILQ_FOREACH(ep, &fork_list, next) { 704 if (ep->function == function) { 705 TAILQ_REMOVE(&fork_list, ep, next); 706 kfree(ep, M_ATFORK); 707 return(1); 708 } 709 } 710 return (0); 711 } 712 713 /* 714 * Add a forked process to the run queue after any remaining setup, such 715 * as setting the fork handler, has been completed. 716 */ 717 void 718 start_forked_proc(struct lwp *lp1, struct proc *p2) 719 { 720 struct lwp *lp2 = ONLY_LWP_IN_PROC(p2); 721 722 /* 723 * Move from SIDL to RUN queue, and activate the process's thread. 724 * Activation of the thread effectively makes the process "a" 725 * current process, so we do not setrunqueue(). 726 * 727 * YYY setrunqueue works here but we should clean up the trampoline 728 * code so we just schedule the LWKT thread and let the trampoline 729 * deal with the userland scheduler on return to userland. 730 */ 731 KASSERT(p2->p_stat == SIDL, 732 ("cannot start forked process, bad status: %p", p2)); 733 p2->p_usched->resetpriority(lp2); 734 crit_enter(); 735 p2->p_stat = SACTIVE; 736 lp2->lwp_stat = LSRUN; 737 p2->p_usched->setrunqueue(lp2); 738 crit_exit(); 739 740 /* 741 * Now can be swapped. 742 */ 743 PRELE(lp1->lwp_proc); 744 745 /* 746 * Preserve synchronization semantics of vfork. If waiting for 747 * child to exec or exit, set P_PPWAIT on child, and sleep on our 748 * proc (in case of exit). 749 */ 750 while (p2->p_flag & P_PPWAIT) 751 tsleep(lp1->lwp_proc, 0, "ppwait", 0); 752 } 753