Bring libcaps in line with recent LWKT changes.
[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
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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 1.18 2004/02/10 15:31:47 hmp 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;
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186 static int curfail = 0, pidchecked = 0;
187 static struct timeval lastfail;
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188 struct forklist *ep;
189 struct filedesc_to_leader *fdtol;
190
191 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
192 return (EINVAL);
193
194 /*
195 * Here we don't create a new process, but we divorce
196 * certain parts of a process from itself.
197 */
198 if ((flags & RFPROC) == 0) {
199
200 vm_fork(p1, 0, flags);
201
202 /*
203 * Close all file descriptors.
204 */
205 if (flags & RFCFDG) {
206 struct filedesc *fdtmp;
207 fdtmp = fdinit(p1);
208 fdfree(p1);
209 p1->p_fd = fdtmp;
210 }
211
212 /*
213 * Unshare file descriptors (from parent.)
214 */
215 if (flags & RFFDG) {
216 if (p1->p_fd->fd_refcnt > 1) {
217 struct filedesc *newfd;
218 newfd = fdcopy(p1);
219 fdfree(p1);
220 p1->p_fd = newfd;
221 }
222 }
223 *procp = NULL;
224 return (0);
225 }
226
227 /*
228 * Although process entries are dynamically created, we still keep
229 * a global limit on the maximum number we will create. Don't allow
230 * a nonprivileged user to use the last ten processes; don't let root
231 * exceed the limit. The variable nprocs is the current number of
232 * processes, maxproc is the limit.
233 */
41c20dac 234 uid = p1->p_ucred->cr_ruid;
984263bc 235 if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) {
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236 if (ppsratecheck(&lastfail, &curfail, 1))
237 printf("maxproc limit exceeded by uid %d, please "
238 "see tuning(7) and login.conf(5).\n", uid);
377d4740 239 tsleep(&forksleep, 0, "fork", hz / 2);
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240 return (EAGAIN);
241 }
242 /*
243 * Increment the nprocs resource before blocking can occur. There
244 * are hard-limits as to the number of processes that can run.
245 */
246 nprocs++;
247
248 /*
249 * Increment the count of procs running with this uid. Don't allow
250 * a nonprivileged user to exceed their current limit.
251 */
41c20dac 252 ok = chgproccnt(p1->p_ucred->cr_ruidinfo, 1,
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253 (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0);
254 if (!ok) {
255 /*
256 * Back out the process count
257 */
258 nprocs--;
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259 if (ppsratecheck(&lastfail, &curfail, 1))
260 printf("maxproc limit exceeded by uid %d, please "
261 "see tuning(7) and login.conf(5).\n", uid);
377d4740 262 tsleep(&forksleep, 0, "fork", hz / 2);
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263 return (EAGAIN);
264 }
265
266 /* Allocate new proc. */
267 newproc = zalloc(proc_zone);
268
269 /*
270 * Setup linkage for kernel based threading
271 */
272 if((flags & RFTHREAD) != 0) {
273 newproc->p_peers = p1->p_peers;
274 p1->p_peers = newproc;
275 newproc->p_leader = p1->p_leader;
276 } else {
277 newproc->p_peers = 0;
278 newproc->p_leader = newproc;
279 }
280
281 newproc->p_wakeup = 0;
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282 newproc->p_vmspace = NULL;
283
284 /*
285 * Find an unused process ID. We remember a range of unused IDs
286 * ready to use (from nextpid+1 through pidchecked-1).
287 */
288 nextpid++;
289 if (randompid)
290 nextpid += arc4random() % randompid;
291retry:
292 /*
293 * If the process ID prototype has wrapped around,
294 * restart somewhat above 0, as the low-numbered procs
295 * tend to include daemons that don't exit.
296 */
297 if (nextpid >= PID_MAX) {
298 nextpid = nextpid % PID_MAX;
299 if (nextpid < 100)
300 nextpid += 100;
301 pidchecked = 0;
302 }
303 if (nextpid >= pidchecked) {
304 int doingzomb = 0;
305
306 pidchecked = PID_MAX;
307 /*
308 * Scan the active and zombie procs to check whether this pid
309 * is in use. Remember the lowest pid that's greater
310 * than nextpid, so we can avoid checking for a while.
311 */
312 p2 = LIST_FIRST(&allproc);
313again:
314 for (; p2 != 0; p2 = LIST_NEXT(p2, p_list)) {
315 while (p2->p_pid == nextpid ||
316 p2->p_pgrp->pg_id == nextpid ||
317 p2->p_session->s_sid == nextpid) {
318 nextpid++;
319 if (nextpid >= pidchecked)
320 goto retry;
321 }
322 if (p2->p_pid > nextpid && pidchecked > p2->p_pid)
323 pidchecked = p2->p_pid;
324 if (p2->p_pgrp->pg_id > nextpid &&
325 pidchecked > p2->p_pgrp->pg_id)
326 pidchecked = p2->p_pgrp->pg_id;
327 if (p2->p_session->s_sid > nextpid &&
328 pidchecked > p2->p_session->s_sid)
329 pidchecked = p2->p_session->s_sid;
330 }
331 if (!doingzomb) {
332 doingzomb = 1;
333 p2 = LIST_FIRST(&zombproc);
334 goto again;
335 }
336 }
337
338 p2 = newproc;
339 p2->p_stat = SIDL; /* protect against others */
340 p2->p_pid = nextpid;
341 LIST_INSERT_HEAD(&allproc, p2, p_list);
342 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
343
344 /*
345 * Make a proc table entry for the new process.
346 * Start by zeroing the section of proc that is zero-initialized,
347 * then copy the section that is copied directly from the parent.
348 */
349 bzero(&p2->p_startzero,
350 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero));
351 bcopy(&p1->p_startcopy, &p2->p_startcopy,
352 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy));
353
354 p2->p_aioinfo = NULL;
355
356 /*
357 * Duplicate sub-structures as needed.
358 * Increase reference counts on shared objects.
359 * The p_stats and p_sigacts substructs are set in vm_fork.
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360 *
361 * P_CP_RELEASED indicates that the process is starting out in
362 * the kernel (in the fork trampoline). The flag will be converted
363 * to P_CURPROC when the new process calls userret() and attempts
364 * to return to userland
984263bc 365 */
a2a5ad0d 366 p2->p_flag = P_INMEM | P_CP_RELEASED;
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367 if (p1->p_flag & P_PROFIL)
368 startprofclock(p2);
dadab5e9 369 p2->p_ucred = crhold(p1->p_ucred);
984263bc 370
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371 if (p2->p_ucred->cr_prison) {
372 p2->p_ucred->cr_prison->pr_ref++;
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373 p2->p_flag |= P_JAILED;
374 }
375
376 if (p2->p_args)
377 p2->p_args->ar_ref++;
378
379 if (flags & RFSIGSHARE) {
380 p2->p_procsig = p1->p_procsig;
381 p2->p_procsig->ps_refcnt++;
382 if (p1->p_sigacts == &p1->p_addr->u_sigacts) {
383 struct sigacts *newsigacts;
384 int s;
385
386 /* Create the shared sigacts structure */
387 MALLOC(newsigacts, struct sigacts *,
388 sizeof(struct sigacts), M_SUBPROC, M_WAITOK);
389 s = splhigh();
390 /*
391 * Set p_sigacts to the new shared structure.
392 * Note that this is updating p1->p_sigacts at the
393 * same time, since p_sigacts is just a pointer to
394 * the shared p_procsig->ps_sigacts.
395 */
396 p2->p_sigacts = newsigacts;
397 bcopy(&p1->p_addr->u_sigacts, p2->p_sigacts,
398 sizeof(*p2->p_sigacts));
399 *p2->p_sigacts = p1->p_addr->u_sigacts;
400 splx(s);
401 }
402 } else {
403 MALLOC(p2->p_procsig, struct procsig *, sizeof(struct procsig),
404 M_SUBPROC, M_WAITOK);
405 bcopy(p1->p_procsig, p2->p_procsig, sizeof(*p2->p_procsig));
406 p2->p_procsig->ps_refcnt = 1;
407 p2->p_sigacts = NULL; /* finished in vm_fork() */
408 }
409 if (flags & RFLINUXTHPN)
410 p2->p_sigparent = SIGUSR1;
411 else
412 p2->p_sigparent = SIGCHLD;
413
414 /* bump references to the text vnode (for procfs) */
415 p2->p_textvp = p1->p_textvp;
416 if (p2->p_textvp)
417 VREF(p2->p_textvp);
418
419 if (flags & RFCFDG) {
420 p2->p_fd = fdinit(p1);
421 fdtol = NULL;
422 } else if (flags & RFFDG) {
423 p2->p_fd = fdcopy(p1);
424 fdtol = NULL;
425 } else {
426 p2->p_fd = fdshare(p1);
427 if (p1->p_fdtol == NULL)
428 p1->p_fdtol =
429 filedesc_to_leader_alloc(NULL,
430 p1->p_leader);
431 if ((flags & RFTHREAD) != 0) {
432 /*
433 * Shared file descriptor table and
434 * shared process leaders.
435 */
436 fdtol = p1->p_fdtol;
437 fdtol->fdl_refcount++;
438 } else {
439 /*
440 * Shared file descriptor table, and
441 * different process leaders
442 */
98a7f915 443 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, p2);
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444 }
445 }
446 p2->p_fdtol = fdtol;
447
448 /*
449 * If p_limit is still copy-on-write, bump refcnt,
450 * otherwise get a copy that won't be modified.
451 * (If PL_SHAREMOD is clear, the structure is shared
452 * copy-on-write.)
453 */
454 if (p1->p_limit->p_lflags & PL_SHAREMOD)
455 p2->p_limit = limcopy(p1->p_limit);
456 else {
457 p2->p_limit = p1->p_limit;
458 p2->p_limit->p_refcnt++;
459 }
460
461 /*
462 * Preserve some more flags in subprocess. P_PROFIL has already
463 * been preserved.
464 */
465 p2->p_flag |= p1->p_flag & (P_SUGID | P_ALTSTACK);
466 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
467 p2->p_flag |= P_CONTROLT;
468 if (flags & RFPPWAIT)
469 p2->p_flag |= P_PPWAIT;
470
471 LIST_INSERT_AFTER(p1, p2, p_pglist);
472
473 /*
474 * Attach the new process to its parent.
475 *
476 * If RFNOWAIT is set, the newly created process becomes a child
477 * of init. This effectively disassociates the child from the
478 * parent.
479 */
480 if (flags & RFNOWAIT)
481 pptr = initproc;
482 else
483 pptr = p1;
484 p2->p_pptr = pptr;
485 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
486 LIST_INIT(&p2->p_children);
98a7f915 487 varsymset_init(&p2->p_varsymset, &p1->p_varsymset);
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488
489#ifdef KTRACE
490 /*
491 * Copy traceflag and tracefile if enabled. If not inherited,
492 * these were zeroed above but we still could have a trace race
493 * so make sure p2's p_tracep is NULL.
494 */
495 if ((p1->p_traceflag & KTRFAC_INHERIT) && p2->p_tracep == NULL) {
496 p2->p_traceflag = p1->p_traceflag;
497 if ((p2->p_tracep = p1->p_tracep) != NULL)
498 VREF(p2->p_tracep);
499 }
500#endif
501
502 /*
503 * set priority of child to be that of parent
504 */
505 p2->p_estcpu = p1->p_estcpu;
506
507 /*
508 * This begins the section where we must prevent the parent
509 * from being swapped.
510 */
511 PHOLD(p1);
512
513 /*
514 * Finish creating the child process. It will return via a different
515 * execution path later. (ie: directly into user mode)
516 */
517 vm_fork(p1, p2, flags);
518
519 if (flags == (RFFDG | RFPROC)) {
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520 mycpu->gd_cnt.v_forks++;
521 mycpu->gd_cnt.v_forkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
984263bc 522 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
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523 mycpu->gd_cnt.v_vforks++;
524 mycpu->gd_cnt.v_vforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
984263bc 525 } else if (p1 == &proc0) {
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526 mycpu->gd_cnt.v_kthreads++;
527 mycpu->gd_cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
984263bc 528 } else {
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529 mycpu->gd_cnt.v_rforks++;
530 mycpu->gd_cnt.v_rforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
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531 }
532
533 /*
534 * Both processes are set up, now check if any loadable modules want
535 * to adjust anything.
536 * What if they have an error? XXX
537 */
538 TAILQ_FOREACH(ep, &fork_list, next) {
539 (*ep->function)(p1, p2, flags);
540 }
541
542 /*
543 * Make child runnable and add to run queue.
544 */
545 microtime(&(p2->p_stats->p_start));
546 p2->p_acflag = AFORK;
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547
548 /*
549 * tell any interested parties about the new process
550 */
551 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid);
552
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553 /*
554 * Return child proc pointer to parent.
555 */
556 *procp = p2;
557 return (0);
558}
559
560/*
561 * The next two functionms are general routines to handle adding/deleting
562 * items on the fork callout list.
563 *
564 * at_fork():
565 * Take the arguments given and put them onto the fork callout list,
566 * However first make sure that it's not already there.
567 * Returns 0 on success or a standard error number.
568 */
569
570int
571at_fork(function)
572 forklist_fn function;
573{
574 struct forklist *ep;
575
576#ifdef INVARIANTS
577 /* let the programmer know if he's been stupid */
578 if (rm_at_fork(function))
579 printf("WARNING: fork callout entry (%p) already present\n",
580 function);
581#endif
582 ep = malloc(sizeof(*ep), M_ATFORK, M_NOWAIT);
583 if (ep == NULL)
584 return (ENOMEM);
585 ep->function = function;
586 TAILQ_INSERT_TAIL(&fork_list, ep, next);
587 return (0);
588}
589
590/*
591 * Scan the exit callout list for the given item and remove it..
592 * Returns the number of items removed (0 or 1)
593 */
594
595int
596rm_at_fork(function)
597 forklist_fn function;
598{
599 struct forklist *ep;
600
601 TAILQ_FOREACH(ep, &fork_list, next) {
602 if (ep->function == function) {
603 TAILQ_REMOVE(&fork_list, ep, next);
604 free(ep, M_ATFORK);
605 return(1);
606 }
607 }
608 return (0);
609}
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610
611/*
612 * Add a forked process to the run queue after any remaining setup, such
613 * as setting the fork handler, has been completed.
614 */
615
616void
617start_forked_proc(struct proc *p1, struct proc *p2)
618{
619 /*
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620 * Move from SIDL to RUN queue, and activate the process's thread.
621 * Activation of the thread effectively makes the process "a"
622 * current process, so we do not setrunqueue().
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623 */
624 KASSERT(p2->p_stat == SIDL,
625 ("cannot start forked process, bad status: %p", p2));
626 (void) splhigh();
627 p2->p_stat = SRUN;
628 setrunqueue(p2);
629 (void) spl0();
630
631 /*
632 * Now can be swapped.
633 */
634 PRELE(p1);
635
636 /*
637 * Preserve synchronization semantics of vfork. If waiting for
638 * child to exec or exit, set P_PPWAIT on child, and sleep on our
639 * proc (in case of exit).
640 */
641 while (p2->p_flag & P_PPWAIT)
377d4740 642 tsleep(p1, 0, "ppwait", 0);
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643}
644