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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 1.77 2008/05/18 20:02:02 nth 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>
67 #include <sys/vmmeter.h>
68 #include <sys/thread2.h>
69 #include <sys/signal2.h>
70 #include <sys/spinlock2.h>
72 #include <sys/dsched.h>
74 static MALLOC_DEFINE(M_ATFORK, "atfork", "atfork callback");
77 * These are the stuctures used to create a callout list for things to do
78 * when forking a process
82 TAILQ_ENTRY(forklist) next;
85 TAILQ_HEAD(forklist_head, forklist);
86 static struct forklist_head fork_list = TAILQ_HEAD_INITIALIZER(fork_list);
88 static struct lwp *lwp_fork(struct lwp *, struct proc *, int flags);
90 int forksleep; /* Place for fork1() to sleep on. */
93 * Red-Black tree support for LWPs
97 rb_lwp_compare(struct lwp *lp1, struct lwp *lp2)
99 if (lp1->lwp_tid < lp2->lwp_tid)
101 if (lp1->lwp_tid > lp2->lwp_tid)
106 RB_GENERATE2(lwp_rb_tree, lwp, u.lwp_rbnode, rb_lwp_compare, lwpid_t, lwp_tid);
114 sys_fork(struct fork_args *uap)
116 struct lwp *lp = curthread->td_lwp;
120 error = fork1(lp, RFFDG | RFPROC | RFPGLOCK, &p2);
122 start_forked_proc(lp, p2);
123 uap->sysmsg_fds[0] = p2->p_pid;
124 uap->sysmsg_fds[1] = 0;
133 sys_vfork(struct vfork_args *uap)
135 struct lwp *lp = curthread->td_lwp;
139 error = fork1(lp, RFFDG | RFPROC | RFPPWAIT | RFMEM | RFPGLOCK, &p2);
141 start_forked_proc(lp, p2);
142 uap->sysmsg_fds[0] = p2->p_pid;
143 uap->sysmsg_fds[1] = 0;
149 * Handle rforks. An rfork may (1) operate on the current process without
150 * creating a new, (2) create a new process that shared the current process's
151 * vmspace, signals, and/or descriptors, or (3) create a new process that does
152 * not share these things (normal fork).
154 * Note that we only call start_forked_proc() if a new process is actually
157 * rfork { int flags }
162 sys_rfork(struct rfork_args *uap)
164 struct lwp *lp = curthread->td_lwp;
168 if ((uap->flags & RFKERNELONLY) != 0)
171 error = fork1(lp, uap->flags | RFPGLOCK, &p2);
174 start_forked_proc(lp, p2);
175 uap->sysmsg_fds[0] = p2 ? p2->p_pid : 0;
176 uap->sysmsg_fds[1] = 0;
185 sys_lwp_create(struct lwp_create_args *uap)
187 struct proc *p = curproc;
189 struct lwp_params params;
192 error = copyin(uap->params, ¶ms, sizeof(params));
196 lwkt_gettoken(&p->p_token);
197 plimit_lwp_fork(p); /* force exclusive access */
198 lp = lwp_fork(curthread->td_lwp, p, RFPROC);
199 error = cpu_prepare_lwp(lp, ¶ms);
200 if (params.tid1 != NULL &&
201 (error = copyout(&lp->lwp_tid, params.tid1, sizeof(lp->lwp_tid))))
203 if (params.tid2 != NULL &&
204 (error = copyout(&lp->lwp_tid, params.tid2, sizeof(lp->lwp_tid))))
208 * Now schedule the new lwp.
210 p->p_usched->resetpriority(lp);
212 lp->lwp_stat = LSRUN;
213 p->p_usched->setrunqueue(lp);
215 lwkt_reltoken(&p->p_token);
220 lwp_rb_tree_RB_REMOVE(&p->p_lwp_tree, lp);
222 /* lwp_dispose expects an exited lwp, and a held proc */
223 lp->lwp_flag |= LWP_WEXIT;
224 lp->lwp_thread->td_flags |= TDF_EXITING;
227 lwkt_reltoken(&p->p_token);
232 int nprocs = 1; /* process 0 */
235 fork1(struct lwp *lp1, int flags, struct proc **procp)
237 struct proc *p1 = lp1->lwp_proc;
238 struct proc *p2, *pptr;
242 static int curfail = 0;
243 static struct timeval lastfail;
245 struct filedesc_to_leader *fdtol;
247 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
250 lwkt_gettoken(&p1->p_token);
254 * Here we don't create a new process, but we divorce
255 * certain parts of a process from itself.
257 if ((flags & RFPROC) == 0) {
259 * This kind of stunt does not work anymore if
260 * there are native threads (lwps) running
262 if (p1->p_nthreads != 1) {
267 vm_fork(p1, 0, flags);
270 * Close all file descriptors.
272 if (flags & RFCFDG) {
273 struct filedesc *fdtmp;
279 * Unshare file descriptors (from parent.)
282 if (p1->p_fd->fd_refcnt > 1) {
283 struct filedesc *newfd;
294 * Interlock against process group signal delivery. If signals
295 * are pending after the interlock is obtained we have to restart
296 * the system call to process the signals. If we don't the child
297 * can miss a pgsignal (such as ^C) sent during the fork.
299 * We can't use CURSIG() here because it will process any STOPs
300 * and cause the process group lock to be held indefinitely. If
301 * a STOP occurs, the fork will be restarted after the CONT.
303 if ((flags & RFPGLOCK) && (pgrp = p1->p_pgrp) != NULL) {
304 lockmgr(&pgrp->pg_lock, LK_SHARED);
305 if (CURSIG_NOBLOCK(lp1)) {
312 * Although process entries are dynamically created, we still keep
313 * a global limit on the maximum number we will create. Don't allow
314 * a nonprivileged user to use the last ten processes; don't let root
315 * exceed the limit. The variable nprocs is the current number of
316 * processes, maxproc is the limit.
318 uid = lp1->lwp_thread->td_ucred->cr_ruid;
319 if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) {
320 if (ppsratecheck(&lastfail, &curfail, 1))
321 kprintf("maxproc limit exceeded by uid %d, please "
322 "see tuning(7) and login.conf(5).\n", uid);
323 tsleep(&forksleep, 0, "fork", hz / 2);
328 * Increment the nprocs resource before blocking can occur. There
329 * are hard-limits as to the number of processes that can run.
334 * Increment the count of procs running with this uid. Don't allow
335 * a nonprivileged user to exceed their current limit.
337 ok = chgproccnt(lp1->lwp_thread->td_ucred->cr_ruidinfo, 1,
338 (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0);
341 * Back out the process count
344 if (ppsratecheck(&lastfail, &curfail, 1))
345 kprintf("maxproc limit exceeded by uid %d, please "
346 "see tuning(7) and login.conf(5).\n", uid);
347 tsleep(&forksleep, 0, "fork", hz / 2);
352 /* Allocate new proc. */
353 p2 = kmalloc(sizeof(struct proc), M_PROC, M_WAITOK|M_ZERO);
356 * Setup linkage for kernel based threading XXX lwp
358 if (flags & RFTHREAD) {
359 p2->p_peers = p1->p_peers;
361 p2->p_leader = p1->p_leader;
366 RB_INIT(&p2->p_lwp_tree);
367 spin_init(&p2->p_spin);
368 lwkt_token_init(&p2->p_token, "iproc");
369 p2->p_lasttid = -1; /* first tid will be 0 */
372 * Setting the state to SIDL protects the partially initialized
373 * process once it starts getting hooked into the rest of the system.
376 proc_add_allproc(p2);
379 * Make a proc table entry for the new process.
380 * The whole structure was zeroed above, so copy the section that is
381 * copied directly from the parent.
383 bcopy(&p1->p_startcopy, &p2->p_startcopy,
384 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy));
387 * Duplicate sub-structures as needed.
388 * Increase reference counts on shared objects.
390 if (p1->p_flag & P_PROFIL)
392 p2->p_ucred = crhold(lp1->lwp_thread->td_ucred);
393 KKASSERT(p2->p_lock == 0);
395 if (jailed(p2->p_ucred))
396 p2->p_flag |= P_JAILED;
399 p2->p_args->ar_ref++;
401 p2->p_usched = p1->p_usched;
402 /* XXX: verify copy of the secondary iosched stuff */
405 if (flags & RFSIGSHARE) {
406 p2->p_sigacts = p1->p_sigacts;
407 p2->p_sigacts->ps_refcnt++;
409 p2->p_sigacts = (struct sigacts *)kmalloc(sizeof(*p2->p_sigacts),
410 M_SUBPROC, M_WAITOK);
411 bcopy(p1->p_sigacts, p2->p_sigacts, sizeof(*p2->p_sigacts));
412 p2->p_sigacts->ps_refcnt = 1;
414 if (flags & RFLINUXTHPN)
415 p2->p_sigparent = SIGUSR1;
417 p2->p_sigparent = SIGCHLD;
419 /* bump references to the text vnode (for procfs) */
420 p2->p_textvp = p1->p_textvp;
424 /* copy namecache handle to the text file */
425 if (p1->p_textnch.mount)
426 cache_copy(&p1->p_textnch, &p2->p_textnch);
429 * Handle file descriptors
431 if (flags & RFCFDG) {
432 p2->p_fd = fdinit(p1);
434 } else if (flags & RFFDG) {
435 p2->p_fd = fdcopy(p1);
438 p2->p_fd = fdshare(p1);
439 if (p1->p_fdtol == NULL) {
440 lwkt_gettoken(&p1->p_token);
442 filedesc_to_leader_alloc(NULL,
444 lwkt_reltoken(&p1->p_token);
446 if ((flags & RFTHREAD) != 0) {
448 * Shared file descriptor table and
449 * shared process leaders.
452 fdtol->fdl_refcount++;
455 * Shared file descriptor table, and
456 * different process leaders
458 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, p2);
462 p2->p_limit = plimit_fork(p1);
465 * Preserve some more flags in subprocess. P_PROFIL has already
468 p2->p_flag |= p1->p_flag & P_SUGID;
469 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
470 p2->p_flag |= P_CONTROLT;
471 if (flags & RFPPWAIT)
472 p2->p_flag |= P_PPWAIT;
475 * Inherit the virtual kernel structure (allows a virtual kernel
476 * to fork to simulate multiple cpus).
479 vkernel_inherit(p1, p2);
482 * Once we are on a pglist we may receive signals. XXX we might
483 * race a ^C being sent to the process group by not receiving it
484 * at all prior to this line.
486 LIST_INSERT_AFTER(p1, p2, p_pglist);
489 * Attach the new process to its parent.
491 * If RFNOWAIT is set, the newly created process becomes a child
492 * of init. This effectively disassociates the child from the
495 if (flags & RFNOWAIT)
500 LIST_INIT(&p2->p_children);
502 lwkt_gettoken(&pptr->p_token);
503 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
504 lwkt_reltoken(&pptr->p_token);
506 varsymset_init(&p2->p_varsymset, &p1->p_varsymset);
507 callout_init(&p2->p_ithandle);
511 * Copy traceflag and tracefile if enabled. If not inherited,
512 * these were zeroed above but we still could have a trace race
513 * so make sure p2's p_tracenode is NULL.
515 if ((p1->p_traceflag & KTRFAC_INHERIT) && p2->p_tracenode == NULL) {
516 p2->p_traceflag = p1->p_traceflag;
517 p2->p_tracenode = ktrinherit(p1->p_tracenode);
522 * This begins the section where we must prevent the parent
523 * from being swapped.
525 * Gets PRELE'd in the caller in start_forked_proc().
529 vm_fork(p1, p2, flags);
532 * Create the first lwp associated with the new proc.
533 * It will return via a different execution path later, directly
534 * into userland, after it was put on the runq by
535 * start_forked_proc().
537 lwp_fork(lp1, p2, flags);
539 if (flags == (RFFDG | RFPROC | RFPGLOCK)) {
540 mycpu->gd_cnt.v_forks++;
541 mycpu->gd_cnt.v_forkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
542 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM | RFPGLOCK)) {
543 mycpu->gd_cnt.v_vforks++;
544 mycpu->gd_cnt.v_vforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
545 } else if (p1 == &proc0) {
546 mycpu->gd_cnt.v_kthreads++;
547 mycpu->gd_cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
549 mycpu->gd_cnt.v_rforks++;
550 mycpu->gd_cnt.v_rforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
554 * Both processes are set up, now check if any loadable modules want
555 * to adjust anything.
556 * What if they have an error? XXX
558 TAILQ_FOREACH(ep, &fork_list, next) {
559 (*ep->function)(p1, p2, flags);
563 * Set the start time. Note that the process is not runnable. The
564 * caller is responsible for making it runnable.
566 microtime(&p2->p_start);
567 p2->p_acflag = AFORK;
570 * tell any interested parties about the new process
572 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid);
575 * Return child proc pointer to parent.
580 lwkt_reltoken(&p1->p_token);
582 lockmgr(&pgrp->pg_lock, LK_RELEASE);
587 lwp_fork(struct lwp *origlp, struct proc *destproc, int flags)
592 lp = kmalloc(sizeof(struct lwp), M_LWP, M_WAITOK|M_ZERO);
594 lp->lwp_proc = destproc;
595 lp->lwp_vmspace = destproc->p_vmspace;
596 lp->lwp_stat = LSRUN;
597 bcopy(&origlp->lwp_startcopy, &lp->lwp_startcopy,
598 (unsigned) ((caddr_t)&lp->lwp_endcopy -
599 (caddr_t)&lp->lwp_startcopy));
600 lp->lwp_flag |= origlp->lwp_flag & LWP_ALTSTACK;
602 * Set cpbase to the last timeout that occured (not the upcoming
605 * A critical section is required since a timer IPI can update
606 * scheduler specific data.
609 lp->lwp_cpbase = mycpu->gd_schedclock.time -
610 mycpu->gd_schedclock.periodic;
611 destproc->p_usched->heuristic_forking(origlp, lp);
613 lp->lwp_cpumask &= usched_mastermask;
616 * Assign a TID to the lp. Loop until the insert succeeds (returns
619 lp->lwp_tid = destproc->p_lasttid;
621 if (++lp->lwp_tid < 0)
623 } while (lwp_rb_tree_RB_INSERT(&destproc->p_lwp_tree, lp) != NULL);
624 destproc->p_lasttid = lp->lwp_tid;
625 destproc->p_nthreads++;
627 td = lwkt_alloc_thread(NULL, LWKT_THREAD_STACK, -1, 0);
629 td->td_proc = destproc;
631 td->td_switch = cpu_heavy_switch;
632 lwkt_setpri(td, TDPRI_KERN_USER);
633 lwkt_set_comm(td, "%s", destproc->p_comm);
636 * cpu_fork will copy and update the pcb, set up the kernel stack,
637 * and make the child ready to run.
639 cpu_fork(origlp, lp, flags);
640 caps_fork(origlp->lwp_thread, lp->lwp_thread);
641 kqueue_init(&lp->lwp_kqueue, destproc->p_fd);
647 * The next two functionms are general routines to handle adding/deleting
648 * items on the fork callout list.
651 * Take the arguments given and put them onto the fork callout list,
652 * However first make sure that it's not already there.
653 * Returns 0 on success or a standard error number.
656 at_fork(forklist_fn function)
661 /* let the programmer know if he's been stupid */
662 if (rm_at_fork(function)) {
663 kprintf("WARNING: fork callout entry (%p) already present\n",
667 ep = kmalloc(sizeof(*ep), M_ATFORK, M_WAITOK|M_ZERO);
668 ep->function = function;
669 TAILQ_INSERT_TAIL(&fork_list, ep, next);
674 * Scan the exit callout list for the given item and remove it..
675 * Returns the number of items removed (0 or 1)
678 rm_at_fork(forklist_fn function)
682 TAILQ_FOREACH(ep, &fork_list, next) {
683 if (ep->function == function) {
684 TAILQ_REMOVE(&fork_list, ep, next);
693 * Add a forked process to the run queue after any remaining setup, such
694 * as setting the fork handler, has been completed.
697 start_forked_proc(struct lwp *lp1, struct proc *p2)
699 struct lwp *lp2 = ONLY_LWP_IN_PROC(p2);
702 * Move from SIDL to RUN queue, and activate the process's thread.
703 * Activation of the thread effectively makes the process "a"
704 * current process, so we do not setrunqueue().
706 * YYY setrunqueue works here but we should clean up the trampoline
707 * code so we just schedule the LWKT thread and let the trampoline
708 * deal with the userland scheduler on return to userland.
710 KASSERT(p2->p_stat == SIDL,
711 ("cannot start forked process, bad status: %p", p2));
712 p2->p_usched->resetpriority(lp2);
714 p2->p_stat = SACTIVE;
715 lp2->lwp_stat = LSRUN;
716 p2->p_usched->setrunqueue(lp2);
720 * Now can be swapped.
722 PRELE(lp1->lwp_proc);
725 * Preserve synchronization semantics of vfork. If waiting for
726 * child to exec or exit, set P_PPWAIT on child, and sleep on our
727 * proc (in case of exit).
729 while (p2->p_flag & P_PPWAIT)
730 tsleep(lp1->lwp_proc, 0, "ppwait", 0);