Score a duh-point for myself. Change the remaining lines for the
[dragonfly.git] / sys / kern / kern_fork.c
CommitLineData
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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 1.72.2.13 2003/06/06 20:21:32 tegge Exp $
6654fbcb 40 * $DragonFly: src/sys/kern/kern_fork.c,v 1.17 2003/11/27 19:57:37 dillon Exp $
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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
60#include <vm/vm.h>
61#include <sys/lock.h>
62#include <vm/pmap.h>
63#include <vm/vm_map.h>
64#include <vm/vm_extern.h>
65#include <vm/vm_zone.h>
66
67#include <sys/vmmeter.h>
68#include <sys/user.h>
69
70static MALLOC_DEFINE(M_ATFORK, "atfork", "atfork callback");
71
72/*
73 * These are the stuctures used to create a callout list for things to do
74 * when forking a process
75 */
76struct forklist {
77 forklist_fn function;
78 TAILQ_ENTRY(forklist) next;
79};
80
81TAILQ_HEAD(forklist_head, forklist);
82static struct forklist_head fork_list = TAILQ_HEAD_INITIALIZER(fork_list);
83
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84int forksleep; /* Place for fork1() to sleep on. */
85
86/* ARGSUSED */
87int
41c20dac 88fork(struct fork_args *uap)
984263bc 89{
41c20dac 90 struct proc *p = curproc;
984263bc 91 struct proc *p2;
41c20dac 92 int error;
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93
94 error = fork1(p, RFFDG | RFPROC, &p2);
95 if (error == 0) {
7d0bac62 96 start_forked_proc(p, p2);
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97 uap->sysmsg_fds[0] = p2->p_pid;
98 uap->sysmsg_fds[1] = 0;
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99 }
100 return error;
101}
102
103/* ARGSUSED */
104int
41c20dac 105vfork(struct vfork_args *uap)
984263bc 106{
41c20dac 107 struct proc *p = curproc;
984263bc 108 struct proc *p2;
41c20dac 109 int error;
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110
111 error = fork1(p, RFFDG | RFPROC | RFPPWAIT | RFMEM, &p2);
112 if (error == 0) {
7d0bac62 113 start_forked_proc(p, p2);
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114 uap->sysmsg_fds[0] = p2->p_pid;
115 uap->sysmsg_fds[1] = 0;
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116 }
117 return error;
118}
119
120int
41c20dac 121rfork(struct rfork_args *uap)
984263bc 122{
41c20dac 123 struct proc *p = curproc;
984263bc 124 struct proc *p2;
41c20dac 125 int error;
984263bc 126
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127 /* Don't allow kernel only flags */
128 if ((uap->flags & RFKERNELONLY) != 0)
129 return (EINVAL);
130
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131 error = fork1(p, uap->flags, &p2);
132 if (error == 0) {
7d0bac62 133 start_forked_proc(p, p2);
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134 uap->sysmsg_fds[0] = p2 ? p2->p_pid : 0;
135 uap->sysmsg_fds[1] = 0;
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136 }
137 return error;
138}
139
140
141int nprocs = 1; /* process 0 */
142static int nextpid = 0;
143
144/*
145 * Random component to nextpid generation. We mix in a random factor to make
146 * it a little harder to predict. We sanity check the modulus value to avoid
147 * doing it in critical paths. Don't let it be too small or we pointlessly
148 * waste randomness entropy, and don't let it be impossibly large. Using a
149 * modulus that is too big causes a LOT more process table scans and slows
150 * down fork processing as the pidchecked caching is defeated.
151 */
152static int randompid = 0;
153
154static int
155sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
156{
157 int error, pid;
158
159 pid = randompid;
160 error = sysctl_handle_int(oidp, &pid, 0, req);
161 if (error || !req->newptr)
162 return (error);
163 if (pid < 0 || pid > PID_MAX - 100) /* out of range */
164 pid = PID_MAX - 100;
165 else if (pid < 2) /* NOP */
166 pid = 0;
167 else if (pid < 100) /* Make it reasonable */
168 pid = 100;
169 randompid = pid;
170 return (error);
171}
172
173SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW,
174 0, 0, sysctl_kern_randompid, "I", "Random PID modulus");
175
176int
177fork1(p1, flags, procp)
178 struct proc *p1;
179 int flags;
180 struct proc **procp;
181{
182 struct proc *p2, *pptr;
183 uid_t uid;
184 struct proc *newproc;
185 int ok;
186 static int pidchecked = 0;
187 struct forklist *ep;
188 struct filedesc_to_leader *fdtol;
189
190 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
191 return (EINVAL);
192
193 /*
194 * Here we don't create a new process, but we divorce
195 * certain parts of a process from itself.
196 */
197 if ((flags & RFPROC) == 0) {
198
199 vm_fork(p1, 0, flags);
200
201 /*
202 * Close all file descriptors.
203 */
204 if (flags & RFCFDG) {
205 struct filedesc *fdtmp;
206 fdtmp = fdinit(p1);
207 fdfree(p1);
208 p1->p_fd = fdtmp;
209 }
210
211 /*
212 * Unshare file descriptors (from parent.)
213 */
214 if (flags & RFFDG) {
215 if (p1->p_fd->fd_refcnt > 1) {
216 struct filedesc *newfd;
217 newfd = fdcopy(p1);
218 fdfree(p1);
219 p1->p_fd = newfd;
220 }
221 }
222 *procp = NULL;
223 return (0);
224 }
225
226 /*
227 * Although process entries are dynamically created, we still keep
228 * a global limit on the maximum number we will create. Don't allow
229 * a nonprivileged user to use the last ten processes; don't let root
230 * exceed the limit. The variable nprocs is the current number of
231 * processes, maxproc is the limit.
232 */
41c20dac 233 uid = p1->p_ucred->cr_ruid;
984263bc 234 if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) {
377d4740 235 tsleep(&forksleep, 0, "fork", hz / 2);
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236 return (EAGAIN);
237 }
238 /*
239 * Increment the nprocs resource before blocking can occur. There
240 * are hard-limits as to the number of processes that can run.
241 */
242 nprocs++;
243
244 /*
245 * Increment the count of procs running with this uid. Don't allow
246 * a nonprivileged user to exceed their current limit.
247 */
41c20dac 248 ok = chgproccnt(p1->p_ucred->cr_ruidinfo, 1,
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249 (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0);
250 if (!ok) {
251 /*
252 * Back out the process count
253 */
254 nprocs--;
377d4740 255 tsleep(&forksleep, 0, "fork", hz / 2);
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256 return (EAGAIN);
257 }
258
259 /* Allocate new proc. */
260 newproc = zalloc(proc_zone);
261
262 /*
263 * Setup linkage for kernel based threading
264 */
265 if((flags & RFTHREAD) != 0) {
266 newproc->p_peers = p1->p_peers;
267 p1->p_peers = newproc;
268 newproc->p_leader = p1->p_leader;
269 } else {
270 newproc->p_peers = 0;
271 newproc->p_leader = newproc;
272 }
273
274 newproc->p_wakeup = 0;
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275 newproc->p_vmspace = NULL;
276
277 /*
278 * Find an unused process ID. We remember a range of unused IDs
279 * ready to use (from nextpid+1 through pidchecked-1).
280 */
281 nextpid++;
282 if (randompid)
283 nextpid += arc4random() % randompid;
284retry:
285 /*
286 * If the process ID prototype has wrapped around,
287 * restart somewhat above 0, as the low-numbered procs
288 * tend to include daemons that don't exit.
289 */
290 if (nextpid >= PID_MAX) {
291 nextpid = nextpid % PID_MAX;
292 if (nextpid < 100)
293 nextpid += 100;
294 pidchecked = 0;
295 }
296 if (nextpid >= pidchecked) {
297 int doingzomb = 0;
298
299 pidchecked = PID_MAX;
300 /*
301 * Scan the active and zombie procs to check whether this pid
302 * is in use. Remember the lowest pid that's greater
303 * than nextpid, so we can avoid checking for a while.
304 */
305 p2 = LIST_FIRST(&allproc);
306again:
307 for (; p2 != 0; p2 = LIST_NEXT(p2, p_list)) {
308 while (p2->p_pid == nextpid ||
309 p2->p_pgrp->pg_id == nextpid ||
310 p2->p_session->s_sid == nextpid) {
311 nextpid++;
312 if (nextpid >= pidchecked)
313 goto retry;
314 }
315 if (p2->p_pid > nextpid && pidchecked > p2->p_pid)
316 pidchecked = p2->p_pid;
317 if (p2->p_pgrp->pg_id > nextpid &&
318 pidchecked > p2->p_pgrp->pg_id)
319 pidchecked = p2->p_pgrp->pg_id;
320 if (p2->p_session->s_sid > nextpid &&
321 pidchecked > p2->p_session->s_sid)
322 pidchecked = p2->p_session->s_sid;
323 }
324 if (!doingzomb) {
325 doingzomb = 1;
326 p2 = LIST_FIRST(&zombproc);
327 goto again;
328 }
329 }
330
331 p2 = newproc;
332 p2->p_stat = SIDL; /* protect against others */
333 p2->p_pid = nextpid;
334 LIST_INSERT_HEAD(&allproc, p2, p_list);
335 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
336
337 /*
338 * Make a proc table entry for the new process.
339 * Start by zeroing the section of proc that is zero-initialized,
340 * then copy the section that is copied directly from the parent.
341 */
342 bzero(&p2->p_startzero,
343 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero));
344 bcopy(&p1->p_startcopy, &p2->p_startcopy,
345 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy));
346
347 p2->p_aioinfo = NULL;
348
349 /*
350 * Duplicate sub-structures as needed.
351 * Increase reference counts on shared objects.
352 * The p_stats and p_sigacts substructs are set in vm_fork.
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353 *
354 * P_CP_RELEASED indicates that the process is starting out in
355 * the kernel (in the fork trampoline). The flag will be converted
356 * to P_CURPROC when the new process calls userret() and attempts
357 * to return to userland
984263bc 358 */
a2a5ad0d 359 p2->p_flag = P_INMEM | P_CP_RELEASED;
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360 if (p1->p_flag & P_PROFIL)
361 startprofclock(p2);
dadab5e9 362 p2->p_ucred = crhold(p1->p_ucred);
984263bc 363
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364 if (p2->p_ucred->cr_prison) {
365 p2->p_ucred->cr_prison->pr_ref++;
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366 p2->p_flag |= P_JAILED;
367 }
368
369 if (p2->p_args)
370 p2->p_args->ar_ref++;
371
372 if (flags & RFSIGSHARE) {
373 p2->p_procsig = p1->p_procsig;
374 p2->p_procsig->ps_refcnt++;
375 if (p1->p_sigacts == &p1->p_addr->u_sigacts) {
376 struct sigacts *newsigacts;
377 int s;
378
379 /* Create the shared sigacts structure */
380 MALLOC(newsigacts, struct sigacts *,
381 sizeof(struct sigacts), M_SUBPROC, M_WAITOK);
382 s = splhigh();
383 /*
384 * Set p_sigacts to the new shared structure.
385 * Note that this is updating p1->p_sigacts at the
386 * same time, since p_sigacts is just a pointer to
387 * the shared p_procsig->ps_sigacts.
388 */
389 p2->p_sigacts = newsigacts;
390 bcopy(&p1->p_addr->u_sigacts, p2->p_sigacts,
391 sizeof(*p2->p_sigacts));
392 *p2->p_sigacts = p1->p_addr->u_sigacts;
393 splx(s);
394 }
395 } else {
396 MALLOC(p2->p_procsig, struct procsig *, sizeof(struct procsig),
397 M_SUBPROC, M_WAITOK);
398 bcopy(p1->p_procsig, p2->p_procsig, sizeof(*p2->p_procsig));
399 p2->p_procsig->ps_refcnt = 1;
400 p2->p_sigacts = NULL; /* finished in vm_fork() */
401 }
402 if (flags & RFLINUXTHPN)
403 p2->p_sigparent = SIGUSR1;
404 else
405 p2->p_sigparent = SIGCHLD;
406
407 /* bump references to the text vnode (for procfs) */
408 p2->p_textvp = p1->p_textvp;
409 if (p2->p_textvp)
410 VREF(p2->p_textvp);
411
412 if (flags & RFCFDG) {
413 p2->p_fd = fdinit(p1);
414 fdtol = NULL;
415 } else if (flags & RFFDG) {
416 p2->p_fd = fdcopy(p1);
417 fdtol = NULL;
418 } else {
419 p2->p_fd = fdshare(p1);
420 if (p1->p_fdtol == NULL)
421 p1->p_fdtol =
422 filedesc_to_leader_alloc(NULL,
423 p1->p_leader);
424 if ((flags & RFTHREAD) != 0) {
425 /*
426 * Shared file descriptor table and
427 * shared process leaders.
428 */
429 fdtol = p1->p_fdtol;
430 fdtol->fdl_refcount++;
431 } else {
432 /*
433 * Shared file descriptor table, and
434 * different process leaders
435 */
98a7f915 436 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, p2);
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437 }
438 }
439 p2->p_fdtol = fdtol;
440
441 /*
442 * If p_limit is still copy-on-write, bump refcnt,
443 * otherwise get a copy that won't be modified.
444 * (If PL_SHAREMOD is clear, the structure is shared
445 * copy-on-write.)
446 */
447 if (p1->p_limit->p_lflags & PL_SHAREMOD)
448 p2->p_limit = limcopy(p1->p_limit);
449 else {
450 p2->p_limit = p1->p_limit;
451 p2->p_limit->p_refcnt++;
452 }
453
454 /*
455 * Preserve some more flags in subprocess. P_PROFIL has already
456 * been preserved.
457 */
458 p2->p_flag |= p1->p_flag & (P_SUGID | P_ALTSTACK);
459 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
460 p2->p_flag |= P_CONTROLT;
461 if (flags & RFPPWAIT)
462 p2->p_flag |= P_PPWAIT;
463
464 LIST_INSERT_AFTER(p1, p2, p_pglist);
465
466 /*
467 * Attach the new process to its parent.
468 *
469 * If RFNOWAIT is set, the newly created process becomes a child
470 * of init. This effectively disassociates the child from the
471 * parent.
472 */
473 if (flags & RFNOWAIT)
474 pptr = initproc;
475 else
476 pptr = p1;
477 p2->p_pptr = pptr;
478 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
479 LIST_INIT(&p2->p_children);
98a7f915 480 varsymset_init(&p2->p_varsymset, &p1->p_varsymset);
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481
482#ifdef KTRACE
483 /*
484 * Copy traceflag and tracefile if enabled. If not inherited,
485 * these were zeroed above but we still could have a trace race
486 * so make sure p2's p_tracep is NULL.
487 */
488 if ((p1->p_traceflag & KTRFAC_INHERIT) && p2->p_tracep == NULL) {
489 p2->p_traceflag = p1->p_traceflag;
490 if ((p2->p_tracep = p1->p_tracep) != NULL)
491 VREF(p2->p_tracep);
492 }
493#endif
494
495 /*
496 * set priority of child to be that of parent
497 */
498 p2->p_estcpu = p1->p_estcpu;
499
500 /*
501 * This begins the section where we must prevent the parent
502 * from being swapped.
503 */
504 PHOLD(p1);
505
506 /*
507 * Finish creating the child process. It will return via a different
508 * execution path later. (ie: directly into user mode)
509 */
510 vm_fork(p1, p2, flags);
511
512 if (flags == (RFFDG | RFPROC)) {
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513 mycpu->gd_cnt.v_forks++;
514 mycpu->gd_cnt.v_forkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
984263bc 515 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
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516 mycpu->gd_cnt.v_vforks++;
517 mycpu->gd_cnt.v_vforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
984263bc 518 } else if (p1 == &proc0) {
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519 mycpu->gd_cnt.v_kthreads++;
520 mycpu->gd_cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
984263bc 521 } else {
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522 mycpu->gd_cnt.v_rforks++;
523 mycpu->gd_cnt.v_rforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
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524 }
525
526 /*
527 * Both processes are set up, now check if any loadable modules want
528 * to adjust anything.
529 * What if they have an error? XXX
530 */
531 TAILQ_FOREACH(ep, &fork_list, next) {
532 (*ep->function)(p1, p2, flags);
533 }
534
535 /*
536 * Make child runnable and add to run queue.
537 */
538 microtime(&(p2->p_stats->p_start));
539 p2->p_acflag = AFORK;
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540
541 /*
542 * tell any interested parties about the new process
543 */
544 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid);
545
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546 /*
547 * Return child proc pointer to parent.
548 */
549 *procp = p2;
550 return (0);
551}
552
553/*
554 * The next two functionms are general routines to handle adding/deleting
555 * items on the fork callout list.
556 *
557 * at_fork():
558 * Take the arguments given and put them onto the fork callout list,
559 * However first make sure that it's not already there.
560 * Returns 0 on success or a standard error number.
561 */
562
563int
564at_fork(function)
565 forklist_fn function;
566{
567 struct forklist *ep;
568
569#ifdef INVARIANTS
570 /* let the programmer know if he's been stupid */
571 if (rm_at_fork(function))
572 printf("WARNING: fork callout entry (%p) already present\n",
573 function);
574#endif
575 ep = malloc(sizeof(*ep), M_ATFORK, M_NOWAIT);
576 if (ep == NULL)
577 return (ENOMEM);
578 ep->function = function;
579 TAILQ_INSERT_TAIL(&fork_list, ep, next);
580 return (0);
581}
582
583/*
584 * Scan the exit callout list for the given item and remove it..
585 * Returns the number of items removed (0 or 1)
586 */
587
588int
589rm_at_fork(function)
590 forklist_fn function;
591{
592 struct forklist *ep;
593
594 TAILQ_FOREACH(ep, &fork_list, next) {
595 if (ep->function == function) {
596 TAILQ_REMOVE(&fork_list, ep, next);
597 free(ep, M_ATFORK);
598 return(1);
599 }
600 }
601 return (0);
602}
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603
604/*
605 * Add a forked process to the run queue after any remaining setup, such
606 * as setting the fork handler, has been completed.
607 */
608
609void
610start_forked_proc(struct proc *p1, struct proc *p2)
611{
612 /*
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613 * Move from SIDL to RUN queue, and activate the process's thread.
614 * Activation of the thread effectively makes the process "a"
615 * current process, so we do not setrunqueue().
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616 */
617 KASSERT(p2->p_stat == SIDL,
618 ("cannot start forked process, bad status: %p", p2));
619 (void) splhigh();
620 p2->p_stat = SRUN;
621 setrunqueue(p2);
622 (void) spl0();
623
624 /*
625 * Now can be swapped.
626 */
627 PRELE(p1);
628
629 /*
630 * Preserve synchronization semantics of vfork. If waiting for
631 * child to exec or exit, set P_PPWAIT on child, and sleep on our
632 * proc (in case of exit).
633 */
634 while (p2->p_flag & P_PPWAIT)
377d4740 635 tsleep(p1, 0, "ppwait", 0);
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636}
637