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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 1.70 2007/07/02 17:06:54 dillon Exp $
43 #include "opt_ktrace.h"
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>
53 #include <sys/resourcevar.h>
54 #include <sys/vnode.h>
56 #include <sys/ktrace.h>
57 #include <sys/unistd.h>
64 #include <vm/vm_map.h>
65 #include <vm/vm_extern.h>
66 #include <vm/vm_zone.h>
68 #include <sys/vmmeter.h>
69 #include <sys/thread2.h>
70 #include <sys/signal2.h>
72 static MALLOC_DEFINE(M_ATFORK, "atfork", "atfork callback");
75 * These are the stuctures used to create a callout list for things to do
76 * when forking a process
80 TAILQ_ENTRY(forklist) next;
83 TAILQ_HEAD(forklist_head, forklist);
84 static struct forklist_head fork_list = TAILQ_HEAD_INITIALIZER(fork_list);
86 static struct lwp *lwp_fork(struct lwp *, struct proc *, int flags);
88 int forksleep; /* Place for fork1() to sleep on. */
92 sys_fork(struct fork_args *uap)
94 struct lwp *lp = curthread->td_lwp;
98 error = fork1(lp, RFFDG | RFPROC | RFPGLOCK, &p2);
100 start_forked_proc(lp, p2);
101 uap->sysmsg_fds[0] = p2->p_pid;
102 uap->sysmsg_fds[1] = 0;
109 sys_vfork(struct vfork_args *uap)
111 struct lwp *lp = curthread->td_lwp;
115 error = fork1(lp, RFFDG | RFPROC | RFPPWAIT | RFMEM | RFPGLOCK, &p2);
117 start_forked_proc(lp, p2);
118 uap->sysmsg_fds[0] = p2->p_pid;
119 uap->sysmsg_fds[1] = 0;
125 * Handle rforks. An rfork may (1) operate on the current process without
126 * creating a new, (2) create a new process that shared the current process's
127 * vmspace, signals, and/or descriptors, or (3) create a new process that does
128 * not share these things (normal fork).
130 * Note that we only call start_forked_proc() if a new process is actually
133 * rfork { int flags }
136 sys_rfork(struct rfork_args *uap)
138 struct lwp *lp = curthread->td_lwp;
142 if ((uap->flags & RFKERNELONLY) != 0)
145 error = fork1(lp, uap->flags | RFPGLOCK, &p2);
148 start_forked_proc(lp, p2);
149 uap->sysmsg_fds[0] = p2 ? p2->p_pid : 0;
150 uap->sysmsg_fds[1] = 0;
156 sys_lwp_create(struct lwp_create_args *uap)
158 struct proc *p = curproc;
160 struct lwp_params params;
163 error = copyin(uap->params, ¶ms, sizeof(params));
167 lp = lwp_fork(curthread->td_lwp, p, RFPROC);
168 error = cpu_prepare_lwp(lp, ¶ms);
169 if (params.tid1 != NULL &&
170 (error = copyout(&lp->lwp_tid, params.tid1, sizeof(lp->lwp_tid))))
172 if (params.tid2 != NULL &&
173 (error = copyout(&lp->lwp_tid, params.tid2, sizeof(lp->lwp_tid))))
177 * Now schedule the new lwp.
179 p->p_usched->resetpriority(lp);
181 lp->lwp_stat = LSRUN;
182 p->p_usched->setrunqueue(lp);
189 LIST_REMOVE(lp, lwp_list);
190 /* lwp_dispose expects an exited lwp, and a held proc */
191 lp->lwp_flag |= LWP_WEXIT;
192 lp->lwp_thread->td_flags |= TDF_EXITING;
199 int nprocs = 1; /* process 0 */
202 fork1(struct lwp *lp1, int flags, struct proc **procp)
204 struct proc *p1 = lp1->lwp_proc;
205 struct proc *p2, *pptr;
209 static int curfail = 0;
210 static struct timeval lastfail;
212 struct filedesc_to_leader *fdtol;
214 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
218 * Here we don't create a new process, but we divorce
219 * certain parts of a process from itself.
221 if ((flags & RFPROC) == 0) {
223 * This kind of stunt does not work anymore if
224 * there are native threads (lwps) running
226 if (p1->p_nthreads != 1)
229 vm_fork(p1, 0, flags);
232 * Close all file descriptors.
234 if (flags & RFCFDG) {
235 struct filedesc *fdtmp;
242 * Unshare file descriptors (from parent.)
245 if (p1->p_fd->fd_refcnt > 1) {
246 struct filedesc *newfd;
257 * Interlock against process group signal delivery. If signals
258 * are pending after the interlock is obtained we have to restart
259 * the system call to process the signals. If we don't the child
260 * can miss a pgsignal (such as ^C) sent during the fork.
262 * We can't use CURSIG() here because it will process any STOPs
263 * and cause the process group lock to be held indefinitely. If
264 * a STOP occurs, the fork will be restarted after the CONT.
268 if ((flags & RFPGLOCK) && (pgrp = p1->p_pgrp) != NULL) {
269 lockmgr(&pgrp->pg_lock, LK_SHARED);
277 * Although process entries are dynamically created, we still keep
278 * a global limit on the maximum number we will create. Don't allow
279 * a nonprivileged user to use the last ten processes; don't let root
280 * exceed the limit. The variable nprocs is the current number of
281 * processes, maxproc is the limit.
283 uid = p1->p_ucred->cr_ruid;
284 if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) {
285 if (ppsratecheck(&lastfail, &curfail, 1))
286 kprintf("maxproc limit exceeded by uid %d, please "
287 "see tuning(7) and login.conf(5).\n", uid);
288 tsleep(&forksleep, 0, "fork", hz / 2);
293 * Increment the nprocs resource before blocking can occur. There
294 * are hard-limits as to the number of processes that can run.
299 * Increment the count of procs running with this uid. Don't allow
300 * a nonprivileged user to exceed their current limit.
302 ok = chgproccnt(p1->p_ucred->cr_ruidinfo, 1,
303 (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0);
306 * Back out the process count
309 if (ppsratecheck(&lastfail, &curfail, 1))
310 kprintf("maxproc limit exceeded by uid %d, please "
311 "see tuning(7) and login.conf(5).\n", uid);
312 tsleep(&forksleep, 0, "fork", hz / 2);
317 /* Allocate new proc. */
318 p2 = zalloc(proc_zone);
319 bzero(p2, sizeof(*p2));
322 * Setup linkage for kernel based threading XXX lwp
324 if (flags & RFTHREAD) {
325 p2->p_peers = p1->p_peers;
327 p2->p_leader = p1->p_leader;
332 LIST_INIT(&p2->p_lwps);
335 * Setting the state to SIDL protects the partially initialized
336 * process once it starts getting hooked into the rest of the system.
339 proc_add_allproc(p2);
342 * Make a proc table entry for the new process.
343 * The whole structure was zeroed above, so copy the section that is
344 * copied directly from the parent.
346 bcopy(&p1->p_startcopy, &p2->p_startcopy,
347 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy));
350 * Duplicate sub-structures as needed.
351 * Increase reference counts on shared objects.
353 if (p1->p_flag & P_PROFIL)
355 p2->p_ucred = crhold(p1->p_ucred);
357 if (jailed(p2->p_ucred))
358 p2->p_flag |= P_JAILED;
361 p2->p_args->ar_ref++;
363 p2->p_usched = p1->p_usched;
365 if (flags & RFSIGSHARE) {
366 p2->p_sigacts = p1->p_sigacts;
367 p2->p_sigacts->ps_refcnt++;
369 p2->p_sigacts = (struct sigacts *)kmalloc(sizeof(*p2->p_sigacts),
370 M_SUBPROC, M_WAITOK);
371 bcopy(p1->p_sigacts, p2->p_sigacts, sizeof(*p2->p_sigacts));
372 p2->p_sigacts->ps_refcnt = 1;
374 if (flags & RFLINUXTHPN)
375 p2->p_sigparent = SIGUSR1;
377 p2->p_sigparent = SIGCHLD;
379 /* bump references to the text vnode (for procfs) */
380 p2->p_textvp = p1->p_textvp;
385 * Handle file descriptors
387 if (flags & RFCFDG) {
388 p2->p_fd = fdinit(p1);
390 } else if (flags & RFFDG) {
391 p2->p_fd = fdcopy(p1);
394 p2->p_fd = fdshare(p1);
395 if (p1->p_fdtol == NULL)
397 filedesc_to_leader_alloc(NULL,
399 if ((flags & RFTHREAD) != 0) {
401 * Shared file descriptor table and
402 * shared process leaders.
405 fdtol->fdl_refcount++;
408 * Shared file descriptor table, and
409 * different process leaders
411 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, p2);
415 p2->p_limit = plimit_fork(p1->p_limit);
418 * Preserve some more flags in subprocess. P_PROFIL has already
421 p2->p_flag |= p1->p_flag & P_SUGID;
422 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
423 p2->p_flag |= P_CONTROLT;
424 if (flags & RFPPWAIT)
425 p2->p_flag |= P_PPWAIT;
428 * Inherit the virtual kernel structure (allows a virtual kernel
429 * to fork to simulate multiple cpus).
432 vkernel_inherit(p1, p2);
435 * Once we are on a pglist we may receive signals. XXX we might
436 * race a ^C being sent to the process group by not receiving it
437 * at all prior to this line.
439 LIST_INSERT_AFTER(p1, p2, p_pglist);
442 * Attach the new process to its parent.
444 * If RFNOWAIT is set, the newly created process becomes a child
445 * of init. This effectively disassociates the child from the
448 if (flags & RFNOWAIT)
453 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
454 LIST_INIT(&p2->p_children);
455 varsymset_init(&p2->p_varsymset, &p1->p_varsymset);
456 callout_init(&p2->p_ithandle);
460 * Copy traceflag and tracefile if enabled. If not inherited,
461 * these were zeroed above but we still could have a trace race
462 * so make sure p2's p_tracenode is NULL.
464 if ((p1->p_traceflag & KTRFAC_INHERIT) && p2->p_tracenode == NULL) {
465 p2->p_traceflag = p1->p_traceflag;
466 p2->p_tracenode = ktrinherit(p1->p_tracenode);
471 * This begins the section where we must prevent the parent
472 * from being swapped.
474 * Gets PRELE'd in the caller in start_forked_proc().
478 vm_fork(p1, p2, flags);
481 * Create the first lwp associated with the new proc.
482 * It will return via a different execution path later, directly
483 * into userland, after it was put on the runq by
484 * start_forked_proc().
486 lwp_fork(lp1, p2, flags);
488 if (flags == (RFFDG | RFPROC)) {
489 mycpu->gd_cnt.v_forks++;
490 mycpu->gd_cnt.v_forkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
491 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
492 mycpu->gd_cnt.v_vforks++;
493 mycpu->gd_cnt.v_vforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
494 } else if (p1 == &proc0) {
495 mycpu->gd_cnt.v_kthreads++;
496 mycpu->gd_cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
498 mycpu->gd_cnt.v_rforks++;
499 mycpu->gd_cnt.v_rforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
503 * Both processes are set up, now check if any loadable modules want
504 * to adjust anything.
505 * What if they have an error? XXX
507 TAILQ_FOREACH(ep, &fork_list, next) {
508 (*ep->function)(p1, p2, flags);
512 * Set the start time. Note that the process is not runnable. The
513 * caller is responsible for making it runnable.
515 microtime(&p2->p_start);
516 p2->p_acflag = AFORK;
519 * tell any interested parties about the new process
521 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid);
524 * Return child proc pointer to parent.
529 lockmgr(&pgrp->pg_lock, LK_RELEASE);
534 lwp_fork(struct lwp *origlp, struct proc *destproc, int flags)
541 * We need to prevent wrap-around collisions.
542 * Until we have a nice tid allocator, we need to
543 * start searching for free tids once we wrap around.
545 * XXX give me a nicer allocator
547 if (destproc->p_lasttid + 1 <= 0) {
550 FOREACH_LWP_IN_PROC(lp, destproc) {
551 if (lp->lwp_tid != tid)
553 /* tids match, search next. */
556 * Wait -- the whole tid space is depleted?
560 panic("lwp_fork: All tids depleted?!");
563 /* When we come here, the tid is not occupied */
565 tid = destproc->p_lasttid++;
568 lp = zalloc(lwp_zone);
569 bzero(lp, sizeof(*lp));
570 lp->lwp_proc = destproc;
571 lp->lwp_vmspace = destproc->p_vmspace;
573 LIST_INSERT_HEAD(&destproc->p_lwps, lp, lwp_list);
574 destproc->p_nthreads++;
575 lp->lwp_stat = LSRUN;
576 bcopy(&origlp->lwp_startcopy, &lp->lwp_startcopy,
577 (unsigned) ((caddr_t)&lp->lwp_endcopy -
578 (caddr_t)&lp->lwp_startcopy));
579 lp->lwp_flag |= origlp->lwp_flag & LWP_ALTSTACK;
581 * Set cpbase to the last timeout that occured (not the upcoming
584 * A critical section is required since a timer IPI can update
585 * scheduler specific data.
588 lp->lwp_cpbase = mycpu->gd_schedclock.time -
589 mycpu->gd_schedclock.periodic;
590 destproc->p_usched->heuristic_forking(origlp, lp);
592 lp->lwp_cpumask &= usched_mastermask;
594 td = lwkt_alloc_thread(NULL, LWKT_THREAD_STACK, -1, 0);
596 td->td_proc = destproc;
598 td->td_switch = cpu_heavy_switch;
600 KKASSERT(td->td_mpcount == 1);
602 lwkt_setpri(td, TDPRI_KERN_USER);
603 lwkt_set_comm(td, "%s", destproc->p_comm);
606 * cpu_fork will copy and update the pcb, set up the kernel stack,
607 * and make the child ready to run.
609 cpu_fork(origlp, lp, flags);
610 caps_fork(origlp->lwp_thread, lp->lwp_thread);
616 * The next two functionms are general routines to handle adding/deleting
617 * items on the fork callout list.
620 * Take the arguments given and put them onto the fork callout list,
621 * However first make sure that it's not already there.
622 * Returns 0 on success or a standard error number.
625 at_fork(forklist_fn function)
630 /* let the programmer know if he's been stupid */
631 if (rm_at_fork(function)) {
632 kprintf("WARNING: fork callout entry (%p) already present\n",
636 ep = kmalloc(sizeof(*ep), M_ATFORK, M_WAITOK|M_ZERO);
637 ep->function = function;
638 TAILQ_INSERT_TAIL(&fork_list, ep, next);
643 * Scan the exit callout list for the given item and remove it..
644 * Returns the number of items removed (0 or 1)
647 rm_at_fork(forklist_fn function)
651 TAILQ_FOREACH(ep, &fork_list, next) {
652 if (ep->function == function) {
653 TAILQ_REMOVE(&fork_list, ep, next);
662 * Add a forked process to the run queue after any remaining setup, such
663 * as setting the fork handler, has been completed.
666 start_forked_proc(struct lwp *lp1, struct proc *p2)
668 struct lwp *lp2 = ONLY_LWP_IN_PROC(p2);
671 * Move from SIDL to RUN queue, and activate the process's thread.
672 * Activation of the thread effectively makes the process "a"
673 * current process, so we do not setrunqueue().
675 * YYY setrunqueue works here but we should clean up the trampoline
676 * code so we just schedule the LWKT thread and let the trampoline
677 * deal with the userland scheduler on return to userland.
679 KASSERT(p2->p_stat == SIDL,
680 ("cannot start forked process, bad status: %p", p2));
681 p2->p_usched->resetpriority(lp2);
683 p2->p_stat = SACTIVE;
684 lp2->lwp_stat = LSRUN;
685 p2->p_usched->setrunqueue(lp2);
689 * Now can be swapped.
691 PRELE(lp1->lwp_proc);
694 * Preserve synchronization semantics of vfork. If waiting for
695 * child to exec or exit, set P_PPWAIT on child, and sleep on our
696 * proc (in case of exit).
698 while (p2->p_flag & P_PPWAIT)
699 tsleep(lp1->lwp_proc, 0, "ppwait", 0);