FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_exit.c
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. 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_exit.c 8.7 (Berkeley) 2/12/94
35 * $FreeBSD: src/sys/kern/kern_exit.c,v 1.92.2.11 2003/01/13 22:51:16 dillon Exp $
36 */
37
38 #include "opt_compat.h"
39 #include "opt_ktrace.h"
40
41 #include <sys/param.h>
42 #include <sys/systm.h>
43 #include <sys/sysproto.h>
44 #include <sys/kernel.h>
45 #include <sys/malloc.h>
46 #include <sys/proc.h>
47 #include <sys/ktrace.h>
48 #include <sys/pioctl.h>
49 #include <sys/tty.h>
50 #include <sys/wait.h>
51 #include <sys/vnode.h>
52 #include <sys/resourcevar.h>
53 #include <sys/signalvar.h>
54 #include <sys/taskqueue.h>
55 #include <sys/ptrace.h>
56 #include <sys/acct.h> /* for acct_process() function prototype */
57 #include <sys/filedesc.h>
58 #include <sys/shm.h>
59 #include <sys/sem.h>
60 #include <sys/jail.h>
61 #include <sys/kern_syscall.h>
62 #include <sys/unistd.h>
63 #include <sys/eventhandler.h>
64 #include <sys/dsched.h>
65
66 #include <vm/vm.h>
67 #include <vm/vm_param.h>
68 #include <sys/lock.h>
69 #include <vm/pmap.h>
70 #include <vm/vm_map.h>
71 #include <vm/vm_extern.h>
72 #include <sys/user.h>
73
74 #include <sys/refcount.h>
75 #include <sys/thread2.h>
76 #include <sys/sysref2.h>
77 #include <sys/mplock2.h>
78
79 #include <machine/vmm.h>
80
81 static void reaplwps(void *context, int dummy);
82 static void reaplwp(struct lwp *lp);
83 static void killlwps(struct lwp *lp);
84
85 static MALLOC_DEFINE(M_ATEXIT, "atexit", "atexit callback");
86
87 /*
88 * callout list for things to do at exit time
89 */
90 struct exitlist {
91 exitlist_fn function;
92 TAILQ_ENTRY(exitlist) next;
93 };
94
95 TAILQ_HEAD(exit_list_head, exitlist);
96 static struct exit_list_head exit_list = TAILQ_HEAD_INITIALIZER(exit_list);
97
98 /*
99 * LWP reaper data
100 */
101 static struct task *deadlwp_task[MAXCPU];
102 static struct lwplist deadlwp_list[MAXCPU];
103 static struct lwkt_token deadlwp_token[MAXCPU];
104
105 /*
106 * exit --
107 * Death of process.
108 *
109 * SYS_EXIT_ARGS(int rval)
110 */
111 int
112 sys_exit(struct exit_args *uap)
113 {
114 exit1(W_EXITCODE(uap->rval, 0));
115 /* NOTREACHED */
116 }
117
118 /*
119 * Extended exit --
120 * Death of a lwp or process with optional bells and whistles.
121 */
122 int
123 sys_extexit(struct extexit_args *uap)
124 {
125 struct proc *p = curproc;
126 int action, who;
127 int error;
128
129 action = EXTEXIT_ACTION(uap->how);
130 who = EXTEXIT_WHO(uap->how);
131
132 /* Check parameters before we might perform some action */
133 switch (who) {
134 case EXTEXIT_PROC:
135 case EXTEXIT_LWP:
136 break;
137 default:
138 return (EINVAL);
139 }
140
141 switch (action) {
142 case EXTEXIT_SIMPLE:
143 break;
144 case EXTEXIT_SETINT:
145 error = copyout(&uap->status, uap->addr, sizeof(uap->status));
146 if (error)
147 return (error);
148 break;
149 default:
150 return (EINVAL);
151 }
152
153 lwkt_gettoken(&p->p_token);
154
155 switch (who) {
156 case EXTEXIT_LWP:
157 /*
158 * Be sure only to perform a simple lwp exit if there is at
159 * least one more lwp in the proc, which will call exit1()
160 * later, otherwise the proc will be an UNDEAD and not even a
161 * SZOMB!
162 */
163 if (p->p_nthreads > 1) {
164 lwp_exit(0, NULL); /* called w/ p_token held */
165 /* NOT REACHED */
166 }
167 /* else last lwp in proc: do the real thing */
168 /* FALLTHROUGH */
169 default: /* to help gcc */
170 case EXTEXIT_PROC:
171 lwkt_reltoken(&p->p_token);
172 exit1(W_EXITCODE(uap->status, 0));
173 /* NOTREACHED */
174 }
175
176 /* NOTREACHED */
177 lwkt_reltoken(&p->p_token); /* safety */
178 }
179
180 /*
181 * Kill all lwps associated with the current process except the
182 * current lwp. Return an error if we race another thread trying to
183 * do the same thing and lose the race.
184 *
185 * If forexec is non-zero the current thread and process flags are
186 * cleaned up so they can be reused.
187 *
188 * Caller must hold curproc->p_token
189 */
190 int
191 killalllwps(int forexec)
192 {
193 struct lwp *lp = curthread->td_lwp;
194 struct proc *p = lp->lwp_proc;
195
196 /*
197 * Interlock against P_WEXIT. Only one of the process's thread
198 * is allowed to do the master exit.
199 */
200 if (p->p_flags & P_WEXIT)
201 return (EALREADY);
202 p->p_flags |= P_WEXIT;
203
204 /*
205 * Interlock with LWP_MP_WEXIT and kill any remaining LWPs
206 */
207 atomic_set_int(&lp->lwp_mpflags, LWP_MP_WEXIT);
208 if (p->p_nthreads > 1)
209 killlwps(lp);
210
211 /*
212 * If doing this for an exec, clean up the remaining thread
213 * (us) for continuing operation after all the other threads
214 * have been killed.
215 */
216 if (forexec) {
217 atomic_clear_int(&lp->lwp_mpflags, LWP_MP_WEXIT);
218 p->p_flags &= ~P_WEXIT;
219 }
220 return(0);
221 }
222
223 /*
224 * Kill all LWPs except the current one. Do not try to signal
225 * LWPs which have exited on their own or have already been
226 * signaled.
227 */
228 static void
229 killlwps(struct lwp *lp)
230 {
231 struct proc *p = lp->lwp_proc;
232 struct lwp *tlp;
233
234 /*
235 * Kill the remaining LWPs. We must send the signal before setting
236 * LWP_MP_WEXIT. The setting of WEXIT is optional but helps reduce
237 * races. tlp must be held across the call as it might block and
238 * allow the target lwp to rip itself out from under our loop.
239 */
240 FOREACH_LWP_IN_PROC(tlp, p) {
241 LWPHOLD(tlp);
242 lwkt_gettoken(&tlp->lwp_token);
243 if ((tlp->lwp_mpflags & LWP_MP_WEXIT) == 0) {
244 lwpsignal(p, tlp, SIGKILL);
245 atomic_set_int(&tlp->lwp_mpflags, LWP_MP_WEXIT);
246 }
247 lwkt_reltoken(&tlp->lwp_token);
248 LWPRELE(tlp);
249 }
250
251 /*
252 * Wait for everything to clear out.
253 */
254 while (p->p_nthreads > 1)
255 tsleep(&p->p_nthreads, 0, "killlwps", 0);
256 }
257
258 /*
259 * Exit: deallocate address space and other resources, change proc state
260 * to zombie, and unlink proc from allproc and parent's lists. Save exit
261 * status and rusage for wait(). Check for child processes and orphan them.
262 */
263 void
264 exit1(int rv)
265 {
266 struct thread *td = curthread;
267 struct proc *p = td->td_proc;
268 struct lwp *lp = td->td_lwp;
269 struct proc *q;
270 struct proc *pp;
271 struct vmspace *vm;
272 struct vnode *vtmp;
273 struct exitlist *ep;
274 int error;
275
276 lwkt_gettoken(&p->p_token);
277
278 if (p->p_pid == 1) {
279 kprintf("init died (signal %d, exit %d)\n",
280 WTERMSIG(rv), WEXITSTATUS(rv));
281 panic("Going nowhere without my init!");
282 }
283 varsymset_clean(&p->p_varsymset);
284 lockuninit(&p->p_varsymset.vx_lock);
285
286 /*
287 * Kill all lwps associated with the current process, return an
288 * error if we race another thread trying to do the same thing
289 * and lose the race.
290 */
291 error = killalllwps(0);
292 if (error) {
293 lwp_exit(0, NULL);
294 /* NOT REACHED */
295 }
296
297 /* are we a task leader? */
298 if (p == p->p_leader) {
299 struct kill_args killArgs;
300 killArgs.signum = SIGKILL;
301 q = p->p_peers;
302 while(q) {
303 killArgs.pid = q->p_pid;
304 /*
305 * The interface for kill is better
306 * than the internal signal
307 */
308 sys_kill(&killArgs);
309 q = q->p_peers;
310 }
311 while (p->p_peers)
312 tsleep((caddr_t)p, 0, "exit1", 0);
313 }
314
315 #ifdef PGINPROF
316 vmsizmon();
317 #endif
318 STOPEVENT(p, S_EXIT, rv);
319 p->p_flags |= P_POSTEXIT; /* stop procfs stepping */
320
321 /*
322 * Check if any loadable modules need anything done at process exit.
323 * e.g. SYSV IPC stuff
324 * XXX what if one of these generates an error?
325 */
326 p->p_xstat = rv;
327 EVENTHANDLER_INVOKE(process_exit, p);
328
329 /*
330 * XXX: imho, the eventhandler stuff is much cleaner than this.
331 * Maybe we should move everything to use eventhandler.
332 */
333 TAILQ_FOREACH(ep, &exit_list, next)
334 (*ep->function)(td);
335
336 if (p->p_flags & P_PROFIL)
337 stopprofclock(p);
338
339 SIGEMPTYSET(p->p_siglist);
340 SIGEMPTYSET(lp->lwp_siglist);
341 if (timevalisset(&p->p_realtimer.it_value))
342 callout_stop_sync(&p->p_ithandle);
343
344 /*
345 * Reset any sigio structures pointing to us as a result of
346 * F_SETOWN with our pid.
347 */
348 funsetownlst(&p->p_sigiolst);
349
350 /*
351 * Close open files and release open-file table.
352 * This may block!
353 */
354 fdfree(p, NULL);
355
356 if (p->p_leader->p_peers) {
357 q = p->p_leader;
358 while(q->p_peers != p)
359 q = q->p_peers;
360 q->p_peers = p->p_peers;
361 wakeup((caddr_t)p->p_leader);
362 }
363
364 /*
365 * XXX Shutdown SYSV semaphores
366 */
367 semexit(p);
368
369 KKASSERT(p->p_numposixlocks == 0);
370
371 /* The next two chunks should probably be moved to vmspace_exit. */
372 vm = p->p_vmspace;
373
374 /*
375 * Clean up data related to virtual kernel operation. Clean up
376 * any vkernel context related to the current lwp now so we can
377 * destroy p_vkernel.
378 */
379 if (p->p_vkernel) {
380 vkernel_lwp_exit(lp);
381 vkernel_exit(p);
382 }
383
384 /*
385 * Release user portion of address space.
386 * This releases references to vnodes,
387 * which could cause I/O if the file has been unlinked.
388 * Need to do this early enough that we can still sleep.
389 * Can't free the entire vmspace as the kernel stack
390 * may be mapped within that space also.
391 *
392 * Processes sharing the same vmspace may exit in one order, and
393 * get cleaned up by vmspace_exit() in a different order. The
394 * last exiting process to reach this point releases as much of
395 * the environment as it can, and the last process cleaned up
396 * by vmspace_exit() (which decrements exitingcnt) cleans up the
397 * remainder.
398 */
399 vmspace_exitbump(vm);
400 sysref_put(&vm->vm_sysref);
401
402 if (SESS_LEADER(p)) {
403 struct session *sp = p->p_session;
404
405 if (sp->s_ttyvp) {
406 /*
407 * We are the controlling process. Signal the
408 * foreground process group, drain the controlling
409 * terminal, and revoke access to the controlling
410 * terminal.
411 *
412 * NOTE: while waiting for the process group to exit
413 * it is possible that one of the processes in the
414 * group will revoke the tty, so the ttyclosesession()
415 * function will re-check sp->s_ttyvp.
416 */
417 if (sp->s_ttyp && (sp->s_ttyp->t_session == sp)) {
418 if (sp->s_ttyp->t_pgrp)
419 pgsignal(sp->s_ttyp->t_pgrp, SIGHUP, 1);
420 ttywait(sp->s_ttyp);
421 ttyclosesession(sp, 1); /* also revoke */
422 }
423 /*
424 * Release the tty. If someone has it open via
425 * /dev/tty then close it (since they no longer can
426 * once we've NULL'd it out).
427 */
428 ttyclosesession(sp, 0);
429
430 /*
431 * s_ttyp is not zero'd; we use this to indicate
432 * that the session once had a controlling terminal.
433 * (for logging and informational purposes)
434 */
435 }
436 sp->s_leader = NULL;
437 }
438 fixjobc(p, p->p_pgrp, 0);
439 (void)acct_process(p);
440 #ifdef KTRACE
441 /*
442 * release trace file
443 */
444 if (p->p_tracenode)
445 ktrdestroy(&p->p_tracenode);
446 p->p_traceflag = 0;
447 #endif
448 /*
449 * Release reference to text vnode
450 */
451 if ((vtmp = p->p_textvp) != NULL) {
452 p->p_textvp = NULL;
453 vrele(vtmp);
454 }
455
456 /* Release namecache handle to text file */
457 if (p->p_textnch.ncp)
458 cache_drop(&p->p_textnch);
459
460 /*
461 * We have to handle PPWAIT here or proc_move_allproc_zombie()
462 * will block on the PHOLD() the parent is doing.
463 *
464 * We are using the flag as an interlock so an atomic op is
465 * necessary to synchronize with the parent's cpu.
466 */
467 if (p->p_flags & P_PPWAIT) {
468 atomic_clear_int(&p->p_flags, P_PPWAIT);
469 wakeup(p->p_pptr);
470 }
471
472 /*
473 * Move the process to the zombie list. This will block
474 * until the process p_lock count reaches 0. The process will
475 * not be reaped until TDF_EXITING is set by cpu_thread_exit(),
476 * which is called from cpu_proc_exit().
477 *
478 * Interlock against waiters using p_waitgen. We increment
479 * p_waitgen after completing the move of our process to the
480 * zombie list.
481 *
482 * WARNING: pp becomes stale when we block, clear it now as a
483 * reminder.
484 */
485 proc_move_allproc_zombie(p);
486 pp = p->p_pptr;
487 atomic_add_long(&pp->p_waitgen, 1);
488 pp = NULL;
489
490 /*
491 * Reparent all of this process's children to the init process.
492 * We must hold initproc->p_token in order to mess with
493 * initproc->p_children. We already hold p->p_token (to remove
494 * the children from our list).
495 */
496 q = LIST_FIRST(&p->p_children);
497 if (q) {
498 lwkt_gettoken(&initproc->p_token);
499 while ((q = LIST_FIRST(&p->p_children)) != NULL) {
500 PHOLD(q);
501 lwkt_gettoken(&q->p_token);
502 if (q != LIST_FIRST(&p->p_children)) {
503 lwkt_reltoken(&q->p_token);
504 PRELE(q);
505 continue;
506 }
507 LIST_REMOVE(q, p_sibling);
508 LIST_INSERT_HEAD(&initproc->p_children, q, p_sibling);
509 q->p_pptr = initproc;
510 q->p_sigparent = SIGCHLD;
511
512 /*
513 * Traced processes are killed
514 * since their existence means someone is screwing up.
515 */
516 if (q->p_flags & P_TRACED) {
517 q->p_flags &= ~P_TRACED;
518 ksignal(q, SIGKILL);
519 }
520 lwkt_reltoken(&q->p_token);
521 PRELE(q);
522 }
523 lwkt_reltoken(&initproc->p_token);
524 wakeup(initproc);
525 }
526
527 /*
528 * Save exit status and final rusage info, adding in child rusage
529 * info and self times.
530 */
531 calcru_proc(p, &p->p_ru);
532 ruadd(&p->p_ru, &p->p_cru);
533
534 /*
535 * notify interested parties of our demise.
536 */
537 KNOTE(&p->p_klist, NOTE_EXIT);
538
539 /*
540 * Notify parent that we're gone. If parent has the PS_NOCLDWAIT
541 * flag set, or if the handler is set to SIG_IGN, notify process 1
542 * instead (and hope it will handle this situation).
543 *
544 * (must reload pp)
545 */
546 if (p->p_pptr->p_sigacts->ps_flag & (PS_NOCLDWAIT | PS_CLDSIGIGN)) {
547 proc_reparent(p, initproc);
548 }
549
550 pp = p->p_pptr;
551 PHOLD(pp);
552 if (p->p_sigparent && pp != initproc) {
553 ksignal(pp, p->p_sigparent);
554 } else {
555 ksignal(pp, SIGCHLD);
556 }
557 p->p_flags &= ~P_TRACED;
558 PRELE(pp);
559
560 /*
561 * cpu_exit is responsible for clearing curproc, since
562 * it is heavily integrated with the thread/switching sequence.
563 *
564 * Other substructures are freed from wait().
565 */
566 plimit_free(p);
567
568 /*
569 * Finally, call machine-dependent code to release as many of the
570 * lwp's resources as we can and halt execution of this thread.
571 *
572 * pp is a wild pointer now but still the correct wakeup() target.
573 * lwp_exit() only uses it to send the wakeup() signal to the likely
574 * parent. Any reparenting race that occurs will get a signal
575 * automatically and not be an issue.
576 */
577 lwp_exit(1, pp);
578 }
579
580 /*
581 * Eventually called by every exiting LWP
582 *
583 * p->p_token must be held. mplock may be held and will be released.
584 */
585 void
586 lwp_exit(int masterexit, void *waddr)
587 {
588 struct thread *td = curthread;
589 struct lwp *lp = td->td_lwp;
590 struct proc *p = lp->lwp_proc;
591 int dowake = 0;
592
593 /*
594 * Release the current user process designation on the process so
595 * the userland scheduler can work in someone else.
596 */
597 p->p_usched->release_curproc(lp);
598
599 /*
600 * lwp_exit() may be called without setting LWP_MP_WEXIT, so
601 * make sure it is set here.
602 */
603 ASSERT_LWKT_TOKEN_HELD(&p->p_token);
604 atomic_set_int(&lp->lwp_mpflags, LWP_MP_WEXIT);
605
606 /*
607 * Clean up any virtualization
608 */
609 if (lp->lwp_vkernel)
610 vkernel_lwp_exit(lp);
611
612 if (td->td_vmm)
613 vmm_vmdestroy();
614
615 /*
616 * Clean up select/poll support
617 */
618 kqueue_terminate(&lp->lwp_kqueue);
619
620 /*
621 * Clean up any syscall-cached ucred
622 */
623 if (td->td_ucred) {
624 crfree(td->td_ucred);
625 td->td_ucred = NULL;
626 }
627
628 /*
629 * Nobody actually wakes us when the lock
630 * count reaches zero, so just wait one tick.
631 */
632 while (lp->lwp_lock > 0)
633 tsleep(lp, 0, "lwpexit", 1);
634
635 /* Hand down resource usage to our proc */
636 ruadd(&p->p_ru, &lp->lwp_ru);
637
638 /*
639 * If we don't hold the process until the LWP is reaped wait*()
640 * may try to dispose of its vmspace before all the LWPs have
641 * actually terminated.
642 */
643 PHOLD(p);
644
645 /*
646 * Do any remaining work that might block on us. We should be
647 * coded such that further blocking is ok after decrementing
648 * p_nthreads but don't take the chance.
649 */
650 dsched_exit_thread(td);
651 biosched_done(curthread);
652
653 /*
654 * We have to use the reaper for all the LWPs except the one doing
655 * the master exit. The LWP doing the master exit can just be
656 * left on p_lwps and the process reaper will deal with it
657 * synchronously, which is much faster.
658 *
659 * Wakeup anyone waiting on p_nthreads to drop to 1 or 0.
660 *
661 * The process is left held until the reaper calls lwp_dispose() on
662 * the lp (after calling lwp_wait()).
663 */
664 if (masterexit == 0) {
665 int cpu = mycpuid;
666
667 lwp_rb_tree_RB_REMOVE(&p->p_lwp_tree, lp);
668 --p->p_nthreads;
669 if ((p->p_flags & P_MAYBETHREADED) && p->p_nthreads <= 1)
670 dowake = 1;
671 lwkt_gettoken(&deadlwp_token[cpu]);
672 LIST_INSERT_HEAD(&deadlwp_list[cpu], lp, u.lwp_reap_entry);
673 taskqueue_enqueue(taskqueue_thread[cpu], deadlwp_task[cpu]);
674 lwkt_reltoken(&deadlwp_token[cpu]);
675 } else {
676 --p->p_nthreads;
677 if ((p->p_flags & P_MAYBETHREADED) && p->p_nthreads <= 1)
678 dowake = 1;
679 }
680
681 /*
682 * We no longer need p_token.
683 *
684 * Tell the userland scheduler that we are going away
685 */
686 lwkt_reltoken(&p->p_token);
687 p->p_usched->heuristic_exiting(lp, p);
688
689 /*
690 * Issue late wakeups after releasing our token to give us a chance
691 * to deschedule and switch away before another cpu in a wait*()
692 * reaps us. This is done as late as possible to reduce contention.
693 */
694 if (dowake)
695 wakeup(&p->p_nthreads);
696 if (waddr)
697 wakeup(waddr);
698
699 cpu_lwp_exit();
700 }
701
702 /*
703 * Wait until a lwp is completely dead. The final interlock in this drama
704 * is when TDF_EXITING is set in cpu_thread_exit() just before the final
705 * switchout.
706 *
707 * At the point TDF_EXITING is set a complete exit is accomplished when
708 * TDF_RUNNING and TDF_PREEMPT_LOCK are both clear. td_mpflags has two
709 * post-switch interlock flags that can be used to wait for the TDF_
710 * flags to clear.
711 *
712 * Returns non-zero on success, and zero if the caller needs to retry
713 * the lwp_wait().
714 */
715 static int
716 lwp_wait(struct lwp *lp)
717 {
718 struct thread *td = lp->lwp_thread;
719 u_int mpflags;
720
721 KKASSERT(lwkt_preempted_proc() != lp);
722
723 /*
724 * This bit of code uses the thread destruction interlock
725 * managed by lwkt_switch_return() to wait for the lwp's
726 * thread to completely disengage.
727 *
728 * It is possible for us to race another cpu core so we
729 * have to do this correctly.
730 */
731 for (;;) {
732 mpflags = td->td_mpflags;
733 cpu_ccfence();
734 if (mpflags & TDF_MP_EXITSIG)
735 break;
736 tsleep_interlock(td, 0);
737 if (atomic_cmpset_int(&td->td_mpflags, mpflags,
738 mpflags | TDF_MP_EXITWAIT)) {
739 tsleep(td, PINTERLOCKED, "lwpxt", 0);
740 }
741 }
742
743 /*
744 * We've already waited for the core exit but there can still
745 * be other refs from e.g. process scans and such.
746 */
747 if (lp->lwp_lock > 0) {
748 tsleep(lp, 0, "lwpwait1", 1);
749 return(0);
750 }
751 if (td->td_refs) {
752 tsleep(td, 0, "lwpwait2", 1);
753 return(0);
754 }
755
756 /*
757 * Now that we have the thread destruction interlock these flags
758 * really should already be cleaned up, keep a check for safety.
759 *
760 * We can't rip its stack out from under it until TDF_EXITING is
761 * set and both TDF_RUNNING and TDF_PREEMPT_LOCK are clear.
762 * TDF_PREEMPT_LOCK must be checked because TDF_RUNNING
763 * will be cleared temporarily if a thread gets preempted.
764 */
765 while ((td->td_flags & (TDF_RUNNING |
766 TDF_PREEMPT_LOCK |
767 TDF_EXITING)) != TDF_EXITING) {
768 tsleep(lp, 0, "lwpwait3", 1);
769 return (0);
770 }
771
772 KASSERT((td->td_flags & (TDF_RUNQ|TDF_TSLEEPQ)) == 0,
773 ("lwp_wait: td %p (%s) still on run or sleep queue",
774 td, td->td_comm));
775 return (1);
776 }
777
778 /*
779 * Release the resources associated with a lwp.
780 * The lwp must be completely dead.
781 */
782 void
783 lwp_dispose(struct lwp *lp)
784 {
785 struct thread *td = lp->lwp_thread;
786
787 KKASSERT(lwkt_preempted_proc() != lp);
788 KKASSERT(td->td_refs == 0);
789 KKASSERT((td->td_flags & (TDF_RUNNING |
790 TDF_PREEMPT_LOCK |
791 TDF_EXITING)) == TDF_EXITING);
792
793 PRELE(lp->lwp_proc);
794 lp->lwp_proc = NULL;
795 if (td != NULL) {
796 td->td_proc = NULL;
797 td->td_lwp = NULL;
798 lp->lwp_thread = NULL;
799 lwkt_free_thread(td);
800 }
801 kfree(lp, M_LWP);
802 }
803
804 int
805 sys_wait4(struct wait_args *uap)
806 {
807 struct rusage rusage;
808 int error, status;
809
810 error = kern_wait(uap->pid, (uap->status ? &status : NULL),
811 uap->options, (uap->rusage ? &rusage : NULL),
812 &uap->sysmsg_result);
813
814 if (error == 0 && uap->status)
815 error = copyout(&status, uap->status, sizeof(*uap->status));
816 if (error == 0 && uap->rusage)
817 error = copyout(&rusage, uap->rusage, sizeof(*uap->rusage));
818 return (error);
819 }
820
821 /*
822 * wait1()
823 *
824 * wait_args(int pid, int *status, int options, struct rusage *rusage)
825 */
826 int
827 kern_wait(pid_t pid, int *status, int options, struct rusage *rusage, int *res)
828 {
829 struct thread *td = curthread;
830 struct lwp *lp;
831 struct proc *q = td->td_proc;
832 struct proc *p, *t;
833 struct pargs *pa;
834 struct sigacts *ps;
835 int nfound, error;
836 long waitgen;
837
838 if (pid == 0)
839 pid = -q->p_pgid;
840 if (options &~ (WUNTRACED|WNOHANG|WCONTINUED|WLINUXCLONE))
841 return (EINVAL);
842
843 /*
844 * Protect the q->p_children list
845 */
846 lwkt_gettoken(&q->p_token);
847 loop:
848 /*
849 * All sorts of things can change due to blocking so we have to loop
850 * all the way back up here.
851 *
852 * The problem is that if a process group is stopped and the parent
853 * is doing a wait*(..., WUNTRACED, ...), it will see the STOP
854 * of the child and then stop itself when it tries to return from the
855 * system call. When the process group is resumed the parent will
856 * then get the STOP status even though the child has now resumed
857 * (a followup wait*() will get the CONT status).
858 *
859 * Previously the CONT would overwrite the STOP because the tstop
860 * was handled within tsleep(), and the parent would only see
861 * the CONT when both are stopped and continued together. This little
862 * two-line hack restores this effect.
863 */
864 while (q->p_stat == SSTOP)
865 tstop();
866
867 nfound = 0;
868
869 /*
870 * Loop on children.
871 *
872 * NOTE: We don't want to break q's p_token in the loop for the
873 * case where no children are found or we risk breaking the
874 * interlock between child and parent.
875 */
876 waitgen = atomic_fetchadd_long(&q->p_waitgen, 0x80000000);
877 LIST_FOREACH(p, &q->p_children, p_sibling) {
878 if (pid != WAIT_ANY &&
879 p->p_pid != pid && p->p_pgid != -pid) {
880 continue;
881 }
882
883 /*
884 * This special case handles a kthread spawned by linux_clone
885 * (see linux_misc.c). The linux_wait4 and linux_waitpid
886 * functions need to be able to distinguish between waiting
887 * on a process and waiting on a thread. It is a thread if
888 * p_sigparent is not SIGCHLD, and the WLINUXCLONE option
889 * signifies we want to wait for threads and not processes.
890 */
891 if ((p->p_sigparent != SIGCHLD) ^
892 ((options & WLINUXCLONE) != 0)) {
893 continue;
894 }
895
896 nfound++;
897 if (p->p_stat == SZOMB) {
898 /*
899 * We may go into SZOMB with threads still present.
900 * We must wait for them to exit before we can reap
901 * the master thread, otherwise we may race reaping
902 * non-master threads.
903 *
904 * Only this routine can remove a process from
905 * the zombie list and destroy it, use PACQUIREZOMB()
906 * to serialize us and loop if it blocks (interlocked
907 * by the parent's q->p_token).
908 *
909 * WARNING! (p) can be invalid when PHOLDZOMB(p)
910 * returns non-zero. Be sure not to
911 * mess with it.
912 */
913 if (PHOLDZOMB(p))
914 goto loop;
915 lwkt_gettoken(&p->p_token);
916 if (p->p_pptr != q) {
917 lwkt_reltoken(&p->p_token);
918 PRELEZOMB(p);
919 goto loop;
920 }
921 while (p->p_nthreads > 0) {
922 tsleep(&p->p_nthreads, 0, "lwpzomb", hz);
923 }
924
925 /*
926 * Reap any LWPs left in p->p_lwps. This is usually
927 * just the last LWP. This must be done before
928 * we loop on p_lock since the lwps hold a ref on
929 * it as a vmspace interlock.
930 *
931 * Once that is accomplished p_nthreads had better
932 * be zero.
933 */
934 while ((lp = RB_ROOT(&p->p_lwp_tree)) != NULL) {
935 lwp_rb_tree_RB_REMOVE(&p->p_lwp_tree, lp);
936 reaplwp(lp);
937 }
938 KKASSERT(p->p_nthreads == 0);
939
940 /*
941 * Don't do anything really bad until all references
942 * to the process go away. This may include other
943 * LWPs which are still in the process of being
944 * reaped. We can't just pull the rug out from under
945 * them because they may still be using the VM space.
946 *
947 * Certain kernel facilities such as /proc will also
948 * put a hold on the process for short periods of
949 * time.
950 */
951 PRELE(p);
952 PSTALL(p, "reap3", 0);
953
954 /* Take care of our return values. */
955 *res = p->p_pid;
956
957 if (status)
958 *status = p->p_xstat;
959 if (rusage)
960 *rusage = p->p_ru;
961
962 /*
963 * If we got the child via a ptrace 'attach',
964 * we need to give it back to the old parent.
965 */
966 if (p->p_oppid && (t = pfind(p->p_oppid)) != NULL) {
967 PHOLD(p);
968 p->p_oppid = 0;
969 proc_reparent(p, t);
970 ksignal(t, SIGCHLD);
971 wakeup((caddr_t)t);
972 error = 0;
973 PRELE(t);
974 lwkt_reltoken(&p->p_token);
975 PRELEZOMB(p);
976 goto done;
977 }
978
979 /*
980 * Unlink the proc from its process group so that
981 * the following operations won't lead to an
982 * inconsistent state for processes running down
983 * the zombie list.
984 */
985 proc_remove_zombie(p);
986 lwkt_reltoken(&p->p_token);
987 leavepgrp(p);
988
989 p->p_xstat = 0;
990 ruadd(&q->p_cru, &p->p_ru);
991
992 /*
993 * Decrement the count of procs running with this uid.
994 */
995 chgproccnt(p->p_ucred->cr_ruidinfo, -1, 0);
996
997 /*
998 * Free up credentials.
999 */
1000 crfree(p->p_ucred);
1001 p->p_ucred = NULL;
1002
1003 /*
1004 * Remove unused arguments
1005 */
1006 pa = p->p_args;
1007 p->p_args = NULL;
1008 if (pa && refcount_release(&pa->ar_ref)) {
1009 kfree(pa, M_PARGS);
1010 pa = NULL;
1011 }
1012
1013 ps = p->p_sigacts;
1014 p->p_sigacts = NULL;
1015 if (ps && refcount_release(&ps->ps_refcnt)) {
1016 kfree(ps, M_SUBPROC);
1017 ps = NULL;
1018 }
1019
1020 /*
1021 * Our exitingcount was incremented when the process
1022 * became a zombie, now that the process has been
1023 * removed from (almost) all lists we should be able
1024 * to safely destroy its vmspace. Wait for any current
1025 * holders to go away (so the vmspace remains stable),
1026 * then scrap it.
1027 */
1028 PSTALL(p, "reap4", 0);
1029 vmspace_exitfree(p);
1030 PSTALL(p, "reap5", 0);
1031
1032 /*
1033 * NOTE: We have to officially release ZOMB in order
1034 * to ensure that a racing thread in kern_wait()
1035 * which blocked on ZOMB is woken up.
1036 */
1037 PHOLD(p);
1038 PRELEZOMB(p);
1039 kfree(p, M_PROC);
1040 atomic_add_int(&nprocs, -1);
1041 error = 0;
1042 goto done;
1043 }
1044 if (p->p_stat == SSTOP && (p->p_flags & P_WAITED) == 0 &&
1045 ((p->p_flags & P_TRACED) || (options & WUNTRACED))) {
1046 PHOLD(p);
1047 lwkt_gettoken(&p->p_token);
1048 if (p->p_pptr != q) {
1049 lwkt_reltoken(&p->p_token);
1050 PRELE(p);
1051 goto loop;
1052 }
1053 if (p->p_stat != SSTOP ||
1054 (p->p_flags & P_WAITED) != 0 ||
1055 ((p->p_flags & P_TRACED) == 0 &&
1056 (options & WUNTRACED) == 0)) {
1057 lwkt_reltoken(&p->p_token);
1058 PRELE(p);
1059 goto loop;
1060 }
1061
1062 p->p_flags |= P_WAITED;
1063
1064 *res = p->p_pid;
1065 if (status)
1066 *status = W_STOPCODE(p->p_xstat);
1067 /* Zero rusage so we get something consistent. */
1068 if (rusage)
1069 bzero(rusage, sizeof(*rusage));
1070 error = 0;
1071 lwkt_reltoken(&p->p_token);
1072 PRELE(p);
1073 goto done;
1074 }
1075 if ((options & WCONTINUED) && (p->p_flags & P_CONTINUED)) {
1076 PHOLD(p);
1077 lwkt_gettoken(&p->p_token);
1078 if (p->p_pptr != q) {
1079 lwkt_reltoken(&p->p_token);
1080 PRELE(p);
1081 goto loop;
1082 }
1083 if ((p->p_flags & P_CONTINUED) == 0) {
1084 lwkt_reltoken(&p->p_token);
1085 PRELE(p);
1086 goto loop;
1087 }
1088
1089 *res = p->p_pid;
1090 p->p_flags &= ~P_CONTINUED;
1091
1092 if (status)
1093 *status = SIGCONT;
1094 error = 0;
1095 lwkt_reltoken(&p->p_token);
1096 PRELE(p);
1097 goto done;
1098 }
1099 }
1100 if (nfound == 0) {
1101 error = ECHILD;
1102 goto done;
1103 }
1104 if (options & WNOHANG) {
1105 *res = 0;
1106 error = 0;
1107 goto done;
1108 }
1109
1110 /*
1111 * Wait for signal - interlocked using q->p_waitgen.
1112 */
1113 error = 0;
1114 while ((waitgen & 0x7FFFFFFF) == (q->p_waitgen & 0x7FFFFFFF)) {
1115 tsleep_interlock(q, PCATCH);
1116 waitgen = atomic_fetchadd_long(&q->p_waitgen, 0x80000000);
1117 if ((waitgen & 0x7FFFFFFF) == (q->p_waitgen & 0x7FFFFFFF)) {
1118 error = tsleep(q, PCATCH | PINTERLOCKED, "wait", 0);
1119 break;
1120 }
1121 }
1122 if (error) {
1123 done:
1124 lwkt_reltoken(&q->p_token);
1125 return (error);
1126 }
1127 goto loop;
1128 }
1129
1130 /*
1131 * Change child's parent process to parent.
1132 *
1133 * p_children/p_sibling requires the parent's token, and
1134 * changing pptr requires the child's token, so we have to
1135 * get three tokens to do this operation. We also need to
1136 * hold pointers that might get ripped out from under us to
1137 * preserve structural integrity.
1138 *
1139 * It is possible to race another reparent or disconnect or other
1140 * similar operation. We must retry when this situation occurs.
1141 * Once we successfully reparent the process we no longer care
1142 * about any races.
1143 */
1144 void
1145 proc_reparent(struct proc *child, struct proc *parent)
1146 {
1147 struct proc *opp;
1148
1149 PHOLD(parent);
1150 while ((opp = child->p_pptr) != parent) {
1151 PHOLD(opp);
1152 lwkt_gettoken(&opp->p_token);
1153 lwkt_gettoken(&child->p_token);
1154 lwkt_gettoken(&parent->p_token);
1155 if (child->p_pptr != opp) {
1156 lwkt_reltoken(&parent->p_token);
1157 lwkt_reltoken(&child->p_token);
1158 lwkt_reltoken(&opp->p_token);
1159 PRELE(opp);
1160 continue;
1161 }
1162 LIST_REMOVE(child, p_sibling);
1163 LIST_INSERT_HEAD(&parent->p_children, child, p_sibling);
1164 child->p_pptr = parent;
1165 lwkt_reltoken(&parent->p_token);
1166 lwkt_reltoken(&child->p_token);
1167 lwkt_reltoken(&opp->p_token);
1168 if (LIST_EMPTY(&opp->p_children))
1169 wakeup(opp);
1170 PRELE(opp);
1171 break;
1172 }
1173 PRELE(parent);
1174 }
1175
1176 /*
1177 * The next two functions are to handle adding/deleting items on the
1178 * exit callout list
1179 *
1180 * at_exit():
1181 * Take the arguments given and put them onto the exit callout list,
1182 * However first make sure that it's not already there.
1183 * returns 0 on success.
1184 */
1185
1186 int
1187 at_exit(exitlist_fn function)
1188 {
1189 struct exitlist *ep;
1190
1191 #ifdef INVARIANTS
1192 /* Be noisy if the programmer has lost track of things */
1193 if (rm_at_exit(function))
1194 kprintf("WARNING: exit callout entry (%p) already present\n",
1195 function);
1196 #endif
1197 ep = kmalloc(sizeof(*ep), M_ATEXIT, M_NOWAIT);
1198 if (ep == NULL)
1199 return (ENOMEM);
1200 ep->function = function;
1201 TAILQ_INSERT_TAIL(&exit_list, ep, next);
1202 return (0);
1203 }
1204
1205 /*
1206 * Scan the exit callout list for the given item and remove it.
1207 * Returns the number of items removed (0 or 1)
1208 */
1209 int
1210 rm_at_exit(exitlist_fn function)
1211 {
1212 struct exitlist *ep;
1213
1214 TAILQ_FOREACH(ep, &exit_list, next) {
1215 if (ep->function == function) {
1216 TAILQ_REMOVE(&exit_list, ep, next);
1217 kfree(ep, M_ATEXIT);
1218 return(1);
1219 }
1220 }
1221 return (0);
1222 }
1223
1224 /*
1225 * LWP reaper related code.
1226 */
1227 static void
1228 reaplwps(void *context, int dummy)
1229 {
1230 struct lwplist *lwplist = context;
1231 struct lwp *lp;
1232 int cpu = mycpuid;
1233
1234 lwkt_gettoken(&deadlwp_token[cpu]);
1235 while ((lp = LIST_FIRST(lwplist))) {
1236 LIST_REMOVE(lp, u.lwp_reap_entry);
1237 reaplwp(lp);
1238 }
1239 lwkt_reltoken(&deadlwp_token[cpu]);
1240 }
1241
1242 static void
1243 reaplwp(struct lwp *lp)
1244 {
1245 while (lwp_wait(lp) == 0)
1246 ;
1247 lwp_dispose(lp);
1248 }
1249
1250 static void
1251 deadlwp_init(void)
1252 {
1253 int cpu;
1254
1255 for (cpu = 0; cpu < ncpus; cpu++) {
1256 lwkt_token_init(&deadlwp_token[cpu], "deadlwpl");
1257 LIST_INIT(&deadlwp_list[cpu]);
1258 deadlwp_task[cpu] = kmalloc(sizeof(*deadlwp_task[cpu]),
1259 M_DEVBUF, M_WAITOK);
1260 TASK_INIT(deadlwp_task[cpu], 0, reaplwps, &deadlwp_list[cpu]);
1261 }
1262 }
1263
1264 SYSINIT(deadlwpinit, SI_SUB_CONFIGURE, SI_ORDER_ANY, deadlwp_init, NULL);
Cache object: ca742d02367f2c8e364fbd317dc37906
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