Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]
FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_fork.c
Version:
- FREEBSD - FREEBSD-13-STABLE - FREEBSD-13-0 - FREEBSD-12-STABLE - FREEBSD-12-0 - FREEBSD-11-STABLE - FREEBSD-11-0 - FREEBSD-10-STABLE - FREEBSD-10-0 - FREEBSD-9-STABLE - FREEBSD-9-0 - FREEBSD-8-STABLE - FREEBSD-8-0 - FREEBSD-7-STABLE - FREEBSD-7-0 - FREEBSD-6-STABLE - FREEBSD-6-0 - FREEBSD-5-STABLE - FREEBSD-5-0 - FREEBSD-4-STABLE - FREEBSD-3-STABLE - FREEBSD22 - l41 - OPENBSD - linux-2.6 - MK84 - PLAN9 - xnu-8792
SearchContext: - none - 3 - 10
SearchContext: - none - 3 - 10
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 * 4. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94 35 */ 36 37 #include <sys/cdefs.h> 38 __FBSDID("$FreeBSD: releng/6.2/sys/kern/kern_fork.c 164286 2006-11-14 20:42:41Z cvs2svn $"); 39 40 #include "opt_ktrace.h" 41 #include "opt_mac.h" 42 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 #include <sys/sysproto.h> 46 #include <sys/eventhandler.h> 47 #include <sys/filedesc.h> 48 #include <sys/kernel.h> 49 #include <sys/kthread.h> 50 #include <sys/sysctl.h> 51 #include <sys/lock.h> 52 #include <sys/malloc.h> 53 #include <sys/mutex.h> 54 #include <sys/proc.h> 55 #include <sys/pioctl.h> 56 #include <sys/resourcevar.h> 57 #include <sys/sched.h> 58 #include <sys/syscall.h> 59 #include <sys/vmmeter.h> 60 #include <sys/vnode.h> 61 #include <sys/acct.h> 62 #include <sys/mac.h> 63 #include <sys/ktr.h> 64 #include <sys/ktrace.h> 65 #include <sys/unistd.h> 66 #include <sys/sx.h> 67 #include <sys/signalvar.h> 68 69 #include <security/audit/audit.h> 70 71 #include <vm/vm.h> 72 #include <vm/pmap.h> 73 #include <vm/vm_map.h> 74 #include <vm/vm_extern.h> 75 #include <vm/uma.h> 76 77 78 #ifndef _SYS_SYSPROTO_H_ 79 struct fork_args { 80 int dummy; 81 }; 82 #endif 83 84 static int forksleep; /* Place for fork1() to sleep on. */ 85 86 /* 87 * MPSAFE 88 */ 89 /* ARGSUSED */ 90 int 91 fork(td, uap) 92 struct thread *td; 93 struct fork_args *uap; 94 { 95 int error; 96 struct proc *p2; 97 98 error = fork1(td, RFFDG | RFPROC, 0, &p2); 99 if (error == 0) { 100 td->td_retval[0] = p2->p_pid; 101 td->td_retval[1] = 0; 102 } 103 return (error); 104 } 105 106 /* 107 * MPSAFE 108 */ 109 /* ARGSUSED */ 110 int 111 vfork(td, uap) 112 struct thread *td; 113 struct vfork_args *uap; 114 { 115 int error; 116 struct proc *p2; 117 118 error = fork1(td, RFFDG | RFPROC | RFPPWAIT | RFMEM, 0, &p2); 119 if (error == 0) { 120 td->td_retval[0] = p2->p_pid; 121 td->td_retval[1] = 0; 122 } 123 return (error); 124 } 125 126 /* 127 * MPSAFE 128 */ 129 int 130 rfork(td, uap) 131 struct thread *td; 132 struct rfork_args *uap; 133 { 134 struct proc *p2; 135 int error; 136 137 /* Don't allow kernel-only flags. */ 138 if ((uap->flags & RFKERNELONLY) != 0) 139 return (EINVAL); 140 141 AUDIT_ARG(fflags, uap->flags); 142 error = fork1(td, uap->flags, 0, &p2); 143 if (error == 0) { 144 td->td_retval[0] = p2 ? p2->p_pid : 0; 145 td->td_retval[1] = 0; 146 } 147 return (error); 148 } 149 150 int nprocs = 1; /* process 0 */ 151 int lastpid = 0; 152 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 153 "Last used PID"); 154 155 /* 156 * Random component to lastpid generation. We mix in a random factor to make 157 * it a little harder to predict. We sanity check the modulus value to avoid 158 * doing it in critical paths. Don't let it be too small or we pointlessly 159 * waste randomness entropy, and don't let it be impossibly large. Using a 160 * modulus that is too big causes a LOT more process table scans and slows 161 * down fork processing as the pidchecked caching is defeated. 162 */ 163 static int randompid = 0; 164 165 static int 166 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 167 { 168 int error, pid; 169 170 error = sysctl_wire_old_buffer(req, sizeof(int)); 171 if (error != 0) 172 return(error); 173 sx_xlock(&allproc_lock); 174 pid = randompid; 175 error = sysctl_handle_int(oidp, &pid, 0, req); 176 if (error == 0 && req->newptr != NULL) { 177 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 178 pid = PID_MAX - 100; 179 else if (pid < 2) /* NOP */ 180 pid = 0; 181 else if (pid < 100) /* Make it reasonable */ 182 pid = 100; 183 randompid = pid; 184 } 185 sx_xunlock(&allproc_lock); 186 return (error); 187 } 188 189 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 190 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 191 192 int 193 fork1(td, flags, pages, procp) 194 struct thread *td; 195 int flags; 196 int pages; 197 struct proc **procp; 198 { 199 struct proc *p1, *p2, *pptr; 200 struct proc *newproc; 201 int ok, trypid; 202 static int curfail, pidchecked = 0; 203 static struct timeval lastfail; 204 struct filedesc *fd; 205 struct filedesc_to_leader *fdtol; 206 struct thread *td2; 207 struct ksegrp *kg2; 208 struct sigacts *newsigacts; 209 int error; 210 211 /* Can't copy and clear. */ 212 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 213 return (EINVAL); 214 215 p1 = td->td_proc; 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 if ((p1->p_flag & P_HADTHREADS) && 223 (flags & (RFCFDG | RFFDG))) { 224 PROC_LOCK(p1); 225 if (thread_single(SINGLE_BOUNDARY)) { 226 PROC_UNLOCK(p1); 227 return (ERESTART); 228 } 229 PROC_UNLOCK(p1); 230 } 231 232 vm_forkproc(td, NULL, NULL, flags); 233 /* 234 * Close all file descriptors. 235 */ 236 if (flags & RFCFDG) { 237 struct filedesc *fdtmp; 238 fdtmp = fdinit(td->td_proc->p_fd); 239 fdfree(td); 240 p1->p_fd = fdtmp; 241 } 242 243 /* 244 * Unshare file descriptors (from parent). 245 */ 246 if (flags & RFFDG) 247 fdunshare(p1, td); 248 249 if ((p1->p_flag & P_HADTHREADS) && 250 (flags & (RFCFDG | RFFDG))) { 251 PROC_LOCK(p1); 252 thread_single_end(); 253 PROC_UNLOCK(p1); 254 } 255 *procp = NULL; 256 return (0); 257 } 258 259 /* 260 * Note 1:1 allows for forking with one thread coming out on the 261 * other side with the expectation that the process is about to 262 * exec. 263 */ 264 if (p1->p_flag & P_HADTHREADS) { 265 /* 266 * Idle the other threads for a second. 267 * Since the user space is copied, it must remain stable. 268 * In addition, all threads (from the user perspective) 269 * need to either be suspended or in the kernel, 270 * where they will try restart in the parent and will 271 * be aborted in the child. 272 */ 273 PROC_LOCK(p1); 274 if (thread_single(SINGLE_NO_EXIT)) { 275 /* Abort. Someone else is single threading before us. */ 276 PROC_UNLOCK(p1); 277 return (ERESTART); 278 } 279 PROC_UNLOCK(p1); 280 /* 281 * All other activity in this process 282 * is now suspended at the user boundary, 283 * (or other safe places if we think of any). 284 */ 285 } 286 287 /* Allocate new proc. */ 288 newproc = uma_zalloc(proc_zone, M_WAITOK); 289 #ifdef MAC 290 mac_init_proc(newproc); 291 #endif 292 #ifdef AUDIT 293 audit_proc_alloc(newproc); 294 #endif 295 knlist_init(&newproc->p_klist, &newproc->p_mtx, NULL, NULL, NULL); 296 STAILQ_INIT(&newproc->p_ktr); 297 298 /* We have to lock the process tree while we look for a pid. */ 299 sx_slock(&proctree_lock); 300 301 /* 302 * Although process entries are dynamically created, we still keep 303 * a global limit on the maximum number we will create. Don't allow 304 * a nonprivileged user to use the last ten processes; don't let root 305 * exceed the limit. The variable nprocs is the current number of 306 * processes, maxproc is the limit. 307 */ 308 sx_xlock(&allproc_lock); 309 if ((nprocs >= maxproc - 10 && 310 suser_cred(td->td_ucred, SUSER_RUID) != 0) || 311 nprocs >= maxproc) { 312 error = EAGAIN; 313 goto fail; 314 } 315 316 /* 317 * Increment the count of procs running with this uid. Don't allow 318 * a nonprivileged user to exceed their current limit. 319 */ 320 error = suser_cred(td->td_ucred, SUSER_RUID | SUSER_ALLOWJAIL); 321 if (error == 0) 322 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); 323 else { 324 PROC_LOCK(p1); 325 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 326 lim_cur(p1, RLIMIT_NPROC)); 327 PROC_UNLOCK(p1); 328 } 329 if (!ok) { 330 error = EAGAIN; 331 goto fail; 332 } 333 334 /* 335 * Increment the nprocs resource before blocking can occur. There 336 * are hard-limits as to the number of processes that can run. 337 */ 338 nprocs++; 339 340 /* 341 * Find an unused process ID. We remember a range of unused IDs 342 * ready to use (from lastpid+1 through pidchecked-1). 343 * 344 * If RFHIGHPID is set (used during system boot), do not allocate 345 * low-numbered pids. 346 */ 347 trypid = lastpid + 1; 348 if (flags & RFHIGHPID) { 349 if (trypid < 10) 350 trypid = 10; 351 } else { 352 if (randompid) 353 trypid += arc4random() % randompid; 354 } 355 retry: 356 /* 357 * If the process ID prototype has wrapped around, 358 * restart somewhat above 0, as the low-numbered procs 359 * tend to include daemons that don't exit. 360 */ 361 if (trypid >= PID_MAX) { 362 trypid = trypid % PID_MAX; 363 if (trypid < 100) 364 trypid += 100; 365 pidchecked = 0; 366 } 367 if (trypid >= pidchecked) { 368 int doingzomb = 0; 369 370 pidchecked = PID_MAX; 371 /* 372 * Scan the active and zombie procs to check whether this pid 373 * is in use. Remember the lowest pid that's greater 374 * than trypid, so we can avoid checking for a while. 375 */ 376 p2 = LIST_FIRST(&allproc); 377 again: 378 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 379 PROC_LOCK(p2); 380 while (p2->p_pid == trypid || 381 (p2->p_pgrp != NULL && 382 (p2->p_pgrp->pg_id == trypid || 383 (p2->p_session != NULL && 384 p2->p_session->s_sid == trypid)))) { 385 trypid++; 386 if (trypid >= pidchecked) { 387 PROC_UNLOCK(p2); 388 goto retry; 389 } 390 } 391 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 392 pidchecked = p2->p_pid; 393 if (p2->p_pgrp != NULL) { 394 if (p2->p_pgrp->pg_id > trypid && 395 pidchecked > p2->p_pgrp->pg_id) 396 pidchecked = p2->p_pgrp->pg_id; 397 if (p2->p_session != NULL && 398 p2->p_session->s_sid > trypid && 399 pidchecked > p2->p_session->s_sid) 400 pidchecked = p2->p_session->s_sid; 401 } 402 PROC_UNLOCK(p2); 403 } 404 if (!doingzomb) { 405 doingzomb = 1; 406 p2 = LIST_FIRST(&zombproc); 407 goto again; 408 } 409 } 410 sx_sunlock(&proctree_lock); 411 412 /* 413 * RFHIGHPID does not mess with the lastpid counter during boot. 414 */ 415 if (flags & RFHIGHPID) 416 pidchecked = 0; 417 else 418 lastpid = trypid; 419 420 p2 = newproc; 421 p2->p_state = PRS_NEW; /* protect against others */ 422 p2->p_pid = trypid; 423 AUDIT_ARG(pid, p2->p_pid); 424 LIST_INSERT_HEAD(&allproc, p2, p_list); 425 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 426 sx_xunlock(&allproc_lock); 427 428 /* 429 * Malloc things while we don't hold any locks. 430 */ 431 if (flags & RFSIGSHARE) 432 newsigacts = NULL; 433 else 434 newsigacts = sigacts_alloc(); 435 436 /* 437 * Copy filedesc. 438 */ 439 if (flags & RFCFDG) { 440 fd = fdinit(p1->p_fd); 441 fdtol = NULL; 442 } else if (flags & RFFDG) { 443 fd = fdcopy(p1->p_fd); 444 fdtol = NULL; 445 } else { 446 fd = fdshare(p1->p_fd); 447 if (p1->p_fdtol == NULL) 448 p1->p_fdtol = 449 filedesc_to_leader_alloc(NULL, 450 NULL, 451 p1->p_leader); 452 if ((flags & RFTHREAD) != 0) { 453 /* 454 * Shared file descriptor table and 455 * shared process leaders. 456 */ 457 fdtol = p1->p_fdtol; 458 FILEDESC_LOCK_FAST(p1->p_fd); 459 fdtol->fdl_refcount++; 460 FILEDESC_UNLOCK_FAST(p1->p_fd); 461 } else { 462 /* 463 * Shared file descriptor table, and 464 * different process leaders 465 */ 466 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 467 p1->p_fd, 468 p2); 469 } 470 } 471 /* 472 * Make a proc table entry for the new process. 473 * Start by zeroing the section of proc that is zero-initialized, 474 * then copy the section that is copied directly from the parent. 475 */ 476 td2 = FIRST_THREAD_IN_PROC(p2); 477 kg2 = FIRST_KSEGRP_IN_PROC(p2); 478 479 /* Allocate and switch to an alternate kstack if specified. */ 480 if (pages != 0) 481 vm_thread_new_altkstack(td2, pages); 482 483 PROC_LOCK(p2); 484 PROC_LOCK(p1); 485 486 bzero(&p2->p_startzero, 487 __rangeof(struct proc, p_startzero, p_endzero)); 488 bzero(&td2->td_startzero, 489 __rangeof(struct thread, td_startzero, td_endzero)); 490 bzero(&kg2->kg_startzero, 491 __rangeof(struct ksegrp, kg_startzero, kg_endzero)); 492 493 bcopy(&p1->p_startcopy, &p2->p_startcopy, 494 __rangeof(struct proc, p_startcopy, p_endcopy)); 495 bcopy(&td->td_startcopy, &td2->td_startcopy, 496 __rangeof(struct thread, td_startcopy, td_endcopy)); 497 bcopy(&td->td_ksegrp->kg_startcopy, &kg2->kg_startcopy, 498 __rangeof(struct ksegrp, kg_startcopy, kg_endcopy)); 499 500 td2->td_sigstk = td->td_sigstk; 501 td2->td_sigmask = td->td_sigmask; 502 503 /* 504 * Duplicate sub-structures as needed. 505 * Increase reference counts on shared objects. 506 */ 507 p2->p_flag = 0; 508 if (p1->p_flag & P_PROFIL) 509 startprofclock(p2); 510 mtx_lock_spin(&sched_lock); 511 p2->p_sflag = PS_INMEM; 512 /* 513 * Allow the scheduler to adjust the priority of the child and 514 * parent while we hold the sched_lock. 515 */ 516 sched_fork(td, td2); 517 518 mtx_unlock_spin(&sched_lock); 519 p2->p_ucred = crhold(td->td_ucred); 520 td2->td_ucred = crhold(p2->p_ucred); /* XXXKSE */ 521 #ifdef AUDIT 522 audit_proc_fork(p1, p2); 523 #endif 524 pargs_hold(p2->p_args); 525 526 if (flags & RFSIGSHARE) { 527 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 528 } else { 529 sigacts_copy(newsigacts, p1->p_sigacts); 530 p2->p_sigacts = newsigacts; 531 } 532 if (flags & RFLINUXTHPN) 533 p2->p_sigparent = SIGUSR1; 534 else 535 p2->p_sigparent = SIGCHLD; 536 537 p2->p_textvp = p1->p_textvp; 538 p2->p_fd = fd; 539 p2->p_fdtol = fdtol; 540 541 /* 542 * p_limit is copy-on-write. Bump its refcount. 543 */ 544 p2->p_limit = lim_hold(p1->p_limit); 545 546 pstats_fork(p1->p_stats, p2->p_stats); 547 548 PROC_UNLOCK(p1); 549 PROC_UNLOCK(p2); 550 551 /* Bump references to the text vnode (for procfs) */ 552 if (p2->p_textvp) 553 vref(p2->p_textvp); 554 555 /* 556 * Set up linkage for kernel based threading. 557 */ 558 if ((flags & RFTHREAD) != 0) { 559 mtx_lock(&ppeers_lock); 560 p2->p_peers = p1->p_peers; 561 p1->p_peers = p2; 562 p2->p_leader = p1->p_leader; 563 mtx_unlock(&ppeers_lock); 564 PROC_LOCK(p1->p_leader); 565 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 566 PROC_UNLOCK(p1->p_leader); 567 /* 568 * The task leader is exiting, so process p1 is 569 * going to be killed shortly. Since p1 obviously 570 * isn't dead yet, we know that the leader is either 571 * sending SIGKILL's to all the processes in this 572 * task or is sleeping waiting for all the peers to 573 * exit. We let p1 complete the fork, but we need 574 * to go ahead and kill the new process p2 since 575 * the task leader may not get a chance to send 576 * SIGKILL to it. We leave it on the list so that 577 * the task leader will wait for this new process 578 * to commit suicide. 579 */ 580 PROC_LOCK(p2); 581 psignal(p2, SIGKILL); 582 PROC_UNLOCK(p2); 583 } else 584 PROC_UNLOCK(p1->p_leader); 585 } else { 586 p2->p_peers = NULL; 587 p2->p_leader = p2; 588 } 589 590 sx_xlock(&proctree_lock); 591 PGRP_LOCK(p1->p_pgrp); 592 PROC_LOCK(p2); 593 PROC_LOCK(p1); 594 595 /* 596 * Preserve some more flags in subprocess. P_PROFIL has already 597 * been preserved. 598 */ 599 p2->p_flag |= p1->p_flag & P_SUGID; 600 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK; 601 SESS_LOCK(p1->p_session); 602 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 603 p2->p_flag |= P_CONTROLT; 604 SESS_UNLOCK(p1->p_session); 605 if (flags & RFPPWAIT) 606 p2->p_flag |= P_PPWAIT; 607 608 p2->p_pgrp = p1->p_pgrp; 609 LIST_INSERT_AFTER(p1, p2, p_pglist); 610 PGRP_UNLOCK(p1->p_pgrp); 611 LIST_INIT(&p2->p_children); 612 613 callout_init(&p2->p_itcallout, CALLOUT_MPSAFE); 614 615 #ifdef KTRACE 616 /* 617 * Copy traceflag and tracefile if enabled. 618 */ 619 mtx_lock(&ktrace_mtx); 620 KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode")); 621 if (p1->p_traceflag & KTRFAC_INHERIT) { 622 p2->p_traceflag = p1->p_traceflag; 623 if ((p2->p_tracevp = p1->p_tracevp) != NULL) { 624 VREF(p2->p_tracevp); 625 KASSERT(p1->p_tracecred != NULL, 626 ("ktrace vnode with no cred")); 627 p2->p_tracecred = crhold(p1->p_tracecred); 628 } 629 } 630 mtx_unlock(&ktrace_mtx); 631 #endif 632 633 /* 634 * If PF_FORK is set, the child process inherits the 635 * procfs ioctl flags from its parent. 636 */ 637 if (p1->p_pfsflags & PF_FORK) { 638 p2->p_stops = p1->p_stops; 639 p2->p_pfsflags = p1->p_pfsflags; 640 } 641 642 /* 643 * This begins the section where we must prevent the parent 644 * from being swapped. 645 */ 646 _PHOLD(p1); 647 PROC_UNLOCK(p1); 648 649 /* 650 * Attach the new process to its parent. 651 * 652 * If RFNOWAIT is set, the newly created process becomes a child 653 * of init. This effectively disassociates the child from the 654 * parent. 655 */ 656 if (flags & RFNOWAIT) 657 pptr = initproc; 658 else 659 pptr = p1; 660 p2->p_pptr = pptr; 661 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 662 sx_xunlock(&proctree_lock); 663 664 /* Inform accounting that we have forked. */ 665 p2->p_acflag = AFORK; 666 PROC_UNLOCK(p2); 667 668 /* 669 * Finish creating the child process. It will return via a different 670 * execution path later. (ie: directly into user mode) 671 */ 672 vm_forkproc(td, p2, td2, flags); 673 674 if (flags == (RFFDG | RFPROC)) { 675 atomic_add_int(&cnt.v_forks, 1); 676 atomic_add_int(&cnt.v_forkpages, p2->p_vmspace->vm_dsize + 677 p2->p_vmspace->vm_ssize); 678 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 679 atomic_add_int(&cnt.v_vforks, 1); 680 atomic_add_int(&cnt.v_vforkpages, p2->p_vmspace->vm_dsize + 681 p2->p_vmspace->vm_ssize); 682 } else if (p1 == &proc0) { 683 atomic_add_int(&cnt.v_kthreads, 1); 684 atomic_add_int(&cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + 685 p2->p_vmspace->vm_ssize); 686 } else { 687 atomic_add_int(&cnt.v_rforks, 1); 688 atomic_add_int(&cnt.v_rforkpages, p2->p_vmspace->vm_dsize + 689 p2->p_vmspace->vm_ssize); 690 } 691 692 /* 693 * Both processes are set up, now check if any loadable modules want 694 * to adjust anything. 695 * What if they have an error? XXX 696 */ 697 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 698 699 /* 700 * Set the child start time and mark the process as being complete. 701 */ 702 microuptime(&p2->p_stats->p_start); 703 mtx_lock_spin(&sched_lock); 704 p2->p_state = PRS_NORMAL; 705 706 /* 707 * If RFSTOPPED not requested, make child runnable and add to 708 * run queue. 709 */ 710 if ((flags & RFSTOPPED) == 0) { 711 TD_SET_CAN_RUN(td2); 712 setrunqueue(td2, SRQ_BORING); 713 } 714 mtx_unlock_spin(&sched_lock); 715 716 /* 717 * Now can be swapped. 718 */ 719 PROC_LOCK(p1); 720 _PRELE(p1); 721 722 /* 723 * Tell any interested parties about the new process. 724 */ 725 KNOTE_LOCKED(&p1->p_klist, NOTE_FORK | p2->p_pid); 726 727 PROC_UNLOCK(p1); 728 729 /* 730 * Preserve synchronization semantics of vfork. If waiting for 731 * child to exec or exit, set P_PPWAIT on child, and sleep on our 732 * proc (in case of exit). 733 */ 734 PROC_LOCK(p2); 735 while (p2->p_flag & P_PPWAIT) 736 msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0); 737 PROC_UNLOCK(p2); 738 739 /* 740 * If other threads are waiting, let them continue now. 741 */ 742 if (p1->p_flag & P_HADTHREADS) { 743 PROC_LOCK(p1); 744 thread_single_end(); 745 PROC_UNLOCK(p1); 746 } 747 748 /* 749 * Return child proc pointer to parent. 750 */ 751 *procp = p2; 752 return (0); 753 fail: 754 sx_sunlock(&proctree_lock); 755 if (ppsratecheck(&lastfail, &curfail, 1)) 756 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n", 757 td->td_ucred->cr_ruid); 758 sx_xunlock(&allproc_lock); 759 #ifdef MAC 760 mac_destroy_proc(newproc); 761 #endif 762 #ifdef AUDIT 763 audit_proc_free(newproc); 764 #endif 765 uma_zfree(proc_zone, newproc); 766 if (p1->p_flag & P_HADTHREADS) { 767 PROC_LOCK(p1); 768 thread_single_end(); 769 PROC_UNLOCK(p1); 770 } 771 tsleep(&forksleep, PUSER, "fork", hz / 2); 772 return (error); 773 } 774 775 /* 776 * Handle the return of a child process from fork1(). This function 777 * is called from the MD fork_trampoline() entry point. 778 */ 779 void 780 fork_exit(callout, arg, frame) 781 void (*callout)(void *, struct trapframe *); 782 void *arg; 783 struct trapframe *frame; 784 { 785 struct proc *p; 786 struct thread *td; 787 788 /* 789 * Finish setting up thread glue so that it begins execution in a 790 * non-nested critical section with sched_lock held but not recursed. 791 */ 792 td = curthread; 793 p = td->td_proc; 794 td->td_oncpu = PCPU_GET(cpuid); 795 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 796 797 sched_lock.mtx_lock = (uintptr_t)td; 798 mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED); 799 CTR4(KTR_PROC, "fork_exit: new thread %p (kse %p, pid %d, %s)", 800 td, td->td_sched, p->p_pid, p->p_comm); 801 802 /* 803 * Processes normally resume in mi_switch() after being 804 * cpu_switch()'ed to, but when children start up they arrive here 805 * instead, so we must do much the same things as mi_switch() would. 806 */ 807 808 if ((td = PCPU_GET(deadthread))) { 809 PCPU_SET(deadthread, NULL); 810 thread_stash(td); 811 } 812 td = curthread; 813 mtx_unlock_spin(&sched_lock); 814 815 /* 816 * cpu_set_fork_handler intercepts this function call to 817 * have this call a non-return function to stay in kernel mode. 818 * initproc has its own fork handler, but it does return. 819 */ 820 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 821 callout(arg, frame); 822 823 /* 824 * Check if a kernel thread misbehaved and returned from its main 825 * function. 826 */ 827 PROC_LOCK(p); 828 if (p->p_flag & P_KTHREAD) { 829 PROC_UNLOCK(p); 830 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 831 p->p_comm, p->p_pid); 832 kthread_exit(0); 833 } 834 PROC_UNLOCK(p); 835 mtx_assert(&Giant, MA_NOTOWNED); 836 } 837 838 /* 839 * Simplified back end of syscall(), used when returning from fork() 840 * directly into user mode. Giant is not held on entry, and must not 841 * be held on return. This function is passed in to fork_exit() as the 842 * first parameter and is called when returning to a new userland process. 843 */ 844 void 845 fork_return(td, frame) 846 struct thread *td; 847 struct trapframe *frame; 848 { 849 850 userret(td, frame, 0); 851 #ifdef KTRACE 852 if (KTRPOINT(td, KTR_SYSRET)) 853 ktrsysret(SYS_fork, 0, 0); 854 #endif 855 mtx_assert(&Giant, MA_NOTOWNED); 856 }
Cache object: 7ed1a5283fb2e20ca4bfa8d9c511a507
[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]