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kern_exit.c revision 1.211
      1 /*	$NetBSD: kern_exit.c,v 1.211 2008/06/16 09:51:14 ad Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1998, 1999, 2006, 2007, 2008 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
      9  * NASA Ames Research Center, and by Andrew Doran.
     10  *
     11  * Redistribution and use in source and binary forms, with or without
     12  * modification, are permitted provided that the following conditions
     13  * are met:
     14  * 1. Redistributions of source code must retain the above copyright
     15  *    notice, this list of conditions and the following disclaimer.
     16  * 2. Redistributions in binary form must reproduce the above copyright
     17  *    notice, this list of conditions and the following disclaimer in the
     18  *    documentation and/or other materials provided with the distribution.
     19  *
     20  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     21  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     22  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     23  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     24  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     25  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     26  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     27  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     28  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     29  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     30  * POSSIBILITY OF SUCH DAMAGE.
     31  */
     32 
     33 /*
     34  * Copyright (c) 1982, 1986, 1989, 1991, 1993
     35  *	The Regents of the University of California.  All rights reserved.
     36  * (c) UNIX System Laboratories, Inc.
     37  * All or some portions of this file are derived from material licensed
     38  * to the University of California by American Telephone and Telegraph
     39  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
     40  * the permission of UNIX System Laboratories, Inc.
     41  *
     42  * Redistribution and use in source and binary forms, with or without
     43  * modification, are permitted provided that the following conditions
     44  * are met:
     45  * 1. Redistributions of source code must retain the above copyright
     46  *    notice, this list of conditions and the following disclaimer.
     47  * 2. Redistributions in binary form must reproduce the above copyright
     48  *    notice, this list of conditions and the following disclaimer in the
     49  *    documentation and/or other materials provided with the distribution.
     50  * 3. Neither the name of the University nor the names of its contributors
     51  *    may be used to endorse or promote products derived from this software
     52  *    without specific prior written permission.
     53  *
     54  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     55  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     56  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     57  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     58  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     59  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     60  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     61  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     62  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     63  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     64  * SUCH DAMAGE.
     65  *
     66  *	@(#)kern_exit.c	8.10 (Berkeley) 2/23/95
     67  */
     68 
     69 #include <sys/cdefs.h>
     70 __KERNEL_RCSID(0, "$NetBSD: kern_exit.c,v 1.211 2008/06/16 09:51:14 ad Exp $");
     71 
     72 #include "opt_ktrace.h"
     73 #include "opt_perfctrs.h"
     74 #include "opt_sysv.h"
     75 
     76 #include <sys/param.h>
     77 #include <sys/aio.h>
     78 #include <sys/systm.h>
     79 #include <sys/ioctl.h>
     80 #include <sys/tty.h>
     81 #include <sys/time.h>
     82 #include <sys/resource.h>
     83 #include <sys/kernel.h>
     84 #include <sys/proc.h>
     85 #include <sys/buf.h>
     86 #include <sys/wait.h>
     87 #include <sys/file.h>
     88 #include <sys/vnode.h>
     89 #include <sys/syslog.h>
     90 #include <sys/malloc.h>
     91 #include <sys/pool.h>
     92 #include <sys/resourcevar.h>
     93 #if defined(PERFCTRS)
     94 #include <sys/pmc.h>
     95 #endif
     96 #include <sys/ptrace.h>
     97 #include <sys/acct.h>
     98 #include <sys/filedesc.h>
     99 #include <sys/ras.h>
    100 #include <sys/signalvar.h>
    101 #include <sys/sched.h>
    102 #include <sys/mount.h>
    103 #include <sys/syscallargs.h>
    104 #include <sys/kauth.h>
    105 #include <sys/sleepq.h>
    106 #include <sys/lockdebug.h>
    107 #include <sys/ktrace.h>
    108 #include <sys/cpu.h>
    109 #include <sys/lwpctl.h>
    110 #include <sys/atomic.h>
    111 
    112 #include <uvm/uvm_extern.h>
    113 
    114 #define DEBUG_EXIT
    115 
    116 #ifdef DEBUG_EXIT
    117 int debug_exit = 0;
    118 #define DPRINTF(x) if (debug_exit) printf x
    119 #else
    120 #define DPRINTF(x)
    121 #endif
    122 
    123 static int find_stopped_child(struct proc *, pid_t, int, struct proc **, int *);
    124 static void proc_free(struct proc *, struct rusage *);
    125 
    126 /*
    127  * Fill in the appropriate signal information, and signal the parent.
    128  */
    129 static void
    130 exit_psignal(struct proc *p, struct proc *pp, ksiginfo_t *ksi)
    131 {
    132 
    133 	KSI_INIT(ksi);
    134 	if ((ksi->ksi_signo = P_EXITSIG(p)) == SIGCHLD) {
    135 		if (WIFSIGNALED(p->p_xstat)) {
    136 			if (WCOREDUMP(p->p_xstat))
    137 				ksi->ksi_code = CLD_DUMPED;
    138 			else
    139 				ksi->ksi_code = CLD_KILLED;
    140 		} else {
    141 			ksi->ksi_code = CLD_EXITED;
    142 		}
    143 	}
    144 	/*
    145 	 * We fill those in, even for non-SIGCHLD.
    146 	 * It's safe to access p->p_cred unlocked here.
    147 	 */
    148 	ksi->ksi_pid = p->p_pid;
    149 	ksi->ksi_uid = kauth_cred_geteuid(p->p_cred);
    150 	ksi->ksi_status = p->p_xstat;
    151 	/* XXX: is this still valid? */
    152 	ksi->ksi_utime = p->p_stats->p_ru.ru_utime.tv_sec;
    153 	ksi->ksi_stime = p->p_stats->p_ru.ru_stime.tv_sec;
    154 }
    155 
    156 /*
    157  * exit --
    158  *	Death of process.
    159  */
    160 int
    161 sys_exit(struct lwp *l, const struct sys_exit_args *uap, register_t *retval)
    162 {
    163 	/* {
    164 		syscallarg(int)	rval;
    165 	} */
    166 	struct proc *p = l->l_proc;
    167 
    168 	/* Don't call exit1() multiple times in the same process. */
    169 	mutex_enter(p->p_lock);
    170 	if (p->p_sflag & PS_WEXIT) {
    171 		mutex_exit(p->p_lock);
    172 		lwp_exit(l);
    173 	}
    174 
    175 	/* exit1() will release the mutex. */
    176 	exit1(l, W_EXITCODE(SCARG(uap, rval), 0));
    177 	/* NOTREACHED */
    178 	return (0);
    179 }
    180 
    181 /*
    182  * Exit: deallocate address space and other resources, change proc state
    183  * to zombie, and unlink proc from allproc and parent's lists.  Save exit
    184  * status and rusage for wait().  Check for child processes and orphan them.
    185  *
    186  * Must be called with p->p_lock held.  Does not return.
    187  */
    188 void
    189 exit1(struct lwp *l, int rv)
    190 {
    191 	struct proc	*p, *q, *nq;
    192 	struct pgrp	*pgrp;
    193 	ksiginfo_t	ksi;
    194 	ksiginfoq_t	kq;
    195 	int		wakeinit;
    196 
    197 	p = l->l_proc;
    198 
    199 	KASSERT(mutex_owned(p->p_lock));
    200 
    201 	if (__predict_false(p == initproc))
    202 		panic("init died (signal %d, exit %d)",
    203 		    WTERMSIG(rv), WEXITSTATUS(rv));
    204 
    205 	p->p_sflag |= PS_WEXIT;
    206 
    207 	/*
    208 	 * Force all other LWPs to exit before we do.  Only then can we
    209 	 * begin to tear down the rest of the process state.
    210 	 */
    211 	if (p->p_nlwps > 1)
    212 		exit_lwps(l);
    213 
    214 	ksiginfo_queue_init(&kq);
    215 
    216 	/*
    217 	 * If we have been asked to stop on exit, do so now.
    218 	 */
    219 	if (__predict_false(p->p_sflag & PS_STOPEXIT)) {
    220 		KERNEL_UNLOCK_ALL(l, &l->l_biglocks);
    221 		sigclearall(p, &contsigmask, &kq);
    222 		p->p_waited = 0;
    223 		membar_producer();
    224 		p->p_stat = SSTOP;
    225 		lwp_lock(l);
    226 		p->p_nrlwps--;
    227 		l->l_stat = LSSTOP;
    228 		mutex_exit(p->p_lock);
    229 		mi_switch(l);
    230 		KERNEL_LOCK(l->l_biglocks, l);
    231 		mutex_enter(p->p_lock);
    232 	}
    233 
    234 	/*
    235 	 * Bin any remaining signals and mark the process as dying so it will
    236 	 * not be found for, e.g. signals.
    237 	 */
    238 	sigfillset(&p->p_sigctx.ps_sigignore);
    239 	sigclearall(p, NULL, &kq);
    240 	p->p_stat = SDYING;
    241 	mutex_exit(p->p_lock);
    242 	ksiginfo_queue_drain(&kq);
    243 
    244 	/* Destroy any lwpctl info. */
    245 	if (p->p_lwpctl != NULL)
    246 		lwp_ctl_exit();
    247 
    248 	/* Destroy all AIO works */
    249 	aio_exit(p, p->p_aio);
    250 
    251 	/*
    252 	 * Drain all remaining references that procfs, ptrace and others may
    253 	 * have on the process.
    254 	 */
    255 	rw_enter(&p->p_reflock, RW_WRITER);
    256 
    257 	DPRINTF(("exit1: %d.%d exiting.\n", p->p_pid, l->l_lid));
    258 
    259 	timers_free(p, TIMERS_ALL);
    260 #if defined(__HAVE_RAS)
    261 	ras_purgeall();
    262 #endif
    263 
    264 	/*
    265 	 * Close open files, release open-file table and free signal
    266 	 * actions.  This may block!
    267 	 */
    268 	fd_free();
    269 	cwdfree(p->p_cwdi);
    270 	p->p_cwdi = NULL;
    271 	doexithooks(p);
    272 	sigactsfree(p->p_sigacts);
    273 
    274 	/*
    275 	 * Write out accounting data.
    276 	 */
    277 	(void)acct_process(l);
    278 
    279 #ifdef KTRACE
    280 	/*
    281 	 * Release trace file.
    282 	 */
    283 	if (p->p_tracep != NULL) {
    284 		mutex_enter(&ktrace_lock);
    285 		ktrderef(p);
    286 		mutex_exit(&ktrace_lock);
    287 	}
    288 #endif
    289 
    290 	/*
    291 	 * If emulation has process exit hook, call it now.
    292 	 * Set the exit status now so that the exit hook has
    293 	 * an opportunity to tweak it (COMPAT_LINUX requires
    294 	 * this for thread group emulation)
    295 	 */
    296 	p->p_xstat = rv;
    297 	if (p->p_emul->e_proc_exit)
    298 		(*p->p_emul->e_proc_exit)(p);
    299 
    300 	/*
    301 	 * Free the VM resources we're still holding on to.
    302 	 * We must do this from a valid thread because doing
    303 	 * so may block. This frees vmspace, which we don't
    304 	 * need anymore. The only remaining lwp is the one
    305 	 * we run at this moment, nothing runs in userland
    306 	 * anymore.
    307 	 */
    308 	uvm_proc_exit(p);
    309 
    310 	/*
    311 	 * Stop profiling.
    312 	 */
    313 	if (__predict_false((p->p_stflag & PST_PROFIL) != 0)) {
    314 		mutex_spin_enter(&p->p_stmutex);
    315 		stopprofclock(p);
    316 		mutex_spin_exit(&p->p_stmutex);
    317 	}
    318 
    319 	/*
    320 	 * If parent is waiting for us to exit or exec, P_PPWAIT is set; we
    321 	 * wake up the parent early to avoid deadlock.  We can do this once
    322 	 * the VM resources are released.
    323 	 */
    324 	mutex_enter(proc_lock);
    325 	if (p->p_lflag & PL_PPWAIT) {
    326 		p->p_lflag &= ~PL_PPWAIT;
    327 		cv_broadcast(&p->p_pptr->p_waitcv);
    328 	}
    329 
    330 	if (SESS_LEADER(p)) {
    331 		struct vnode *vprele = NULL, *vprevoke = NULL;
    332 		struct session *sp = p->p_session;
    333 		struct tty *tp;
    334 
    335 		if (sp->s_ttyvp) {
    336 			/*
    337 			 * Controlling process.
    338 			 * Signal foreground pgrp,
    339 			 * drain controlling terminal
    340 			 * and revoke access to controlling terminal.
    341 			 */
    342 			tp = sp->s_ttyp;
    343 			mutex_spin_enter(&tty_lock);
    344 			if (tp->t_session == sp) {
    345 				/* we can't guarantee the revoke will do this */
    346 				pgrp = tp->t_pgrp;
    347 				tp->t_pgrp = NULL;
    348 				tp->t_session = NULL;
    349 				mutex_spin_exit(&tty_lock);
    350 				if (pgrp != NULL) {
    351 					pgsignal(pgrp, SIGHUP, 1);
    352 				}
    353 				mutex_exit(proc_lock);
    354 				(void) ttywait(tp);
    355 				mutex_enter(proc_lock);
    356 
    357 				/* The tty could have been revoked. */
    358 				vprevoke = sp->s_ttyvp;
    359 			} else
    360 				mutex_spin_exit(&tty_lock);
    361 			vprele = sp->s_ttyvp;
    362 			sp->s_ttyvp = NULL;
    363 			/*
    364 			 * s_ttyp is not zero'd; we use this to indicate
    365 			 * that the session once had a controlling terminal.
    366 			 * (for logging and informational purposes)
    367 			 */
    368 		}
    369 		sp->s_leader = NULL;
    370 
    371 		if (vprevoke != NULL || vprele != NULL) {
    372 			if (vprevoke != NULL) {
    373 				SESSRELE(sp);
    374 				mutex_exit(proc_lock);
    375 				VOP_REVOKE(vprevoke, REVOKEALL);
    376 			} else
    377 				mutex_exit(proc_lock);
    378 			if (vprele != NULL)
    379 				vrele(vprele);
    380 			mutex_enter(proc_lock);
    381 		}
    382 	}
    383 	fixjobc(p, p->p_pgrp, 0);
    384 
    385 	/*
    386 	 * Finalize the last LWP's specificdata, as well as the
    387 	 * specificdata for the proc itself.
    388 	 */
    389 	lwp_finispecific(l);
    390 	proc_finispecific(p);
    391 
    392 	/*
    393 	 * Notify interested parties of our demise.
    394 	 */
    395 	KNOTE(&p->p_klist, NOTE_EXIT);
    396 
    397 #if PERFCTRS
    398 	/*
    399 	 * Save final PMC information in parent process & clean up.
    400 	 */
    401 	if (PMC_ENABLED(p)) {
    402 		pmc_save_context(p);
    403 		pmc_accumulate(p->p_pptr, p);
    404 		pmc_process_exit(p);
    405 	}
    406 #endif
    407 
    408 	/*
    409 	 * Reset p_opptr pointer of all former children which got
    410 	 * traced by another process and were reparented. We reset
    411 	 * it to NULL here; the trace detach code then reparents
    412 	 * the child to initproc. We only check allproc list, since
    413 	 * eventual former children on zombproc list won't reference
    414 	 * p_opptr anymore.
    415 	 */
    416 	if (__predict_false(p->p_slflag & PSL_CHTRACED)) {
    417 		PROCLIST_FOREACH(q, &allproc) {
    418 			if ((q->p_flag & PK_MARKER) != 0)
    419 				continue;
    420 			if (q->p_opptr == p)
    421 				q->p_opptr = NULL;
    422 		}
    423 	}
    424 
    425 	/*
    426 	 * Give orphaned children to init(8).
    427 	 */
    428 	q = LIST_FIRST(&p->p_children);
    429 	wakeinit = (q != NULL);
    430 	for (; q != NULL; q = nq) {
    431 		nq = LIST_NEXT(q, p_sibling);
    432 
    433 		/*
    434 		 * Traced processes are killed since their existence
    435 		 * means someone is screwing up. Since we reset the
    436 		 * trace flags, the logic in sys_wait4() would not be
    437 		 * triggered to reparent the process to its
    438 		 * original parent, so we must do this here.
    439 		 */
    440 		if (__predict_false(q->p_slflag & PSL_TRACED)) {
    441 			mutex_enter(p->p_lock);
    442 			q->p_slflag &= ~(PSL_TRACED|PSL_FSTRACE|PSL_SYSCALL);
    443 			mutex_exit(p->p_lock);
    444 			if (q->p_opptr != q->p_pptr) {
    445 				struct proc *t = q->p_opptr;
    446 				proc_reparent(q, t ? t : initproc);
    447 				q->p_opptr = NULL;
    448 			} else
    449 				proc_reparent(q, initproc);
    450 			killproc(q, "orphaned traced process");
    451 		} else
    452 			proc_reparent(q, initproc);
    453 	}
    454 
    455 	/*
    456 	 * Move proc from allproc to zombproc, it's now nearly ready to be
    457 	 * collected by parent.
    458 	 */
    459 	LIST_REMOVE(l, l_list);
    460 	LIST_REMOVE(p, p_list);
    461 	LIST_INSERT_HEAD(&zombproc, p, p_list);
    462 
    463 	/*
    464 	 * Mark the process as dead.  We must do this before we signal
    465 	 * the parent.
    466 	 */
    467 	p->p_stat = SDEAD;
    468 
    469 	/* Put in front of parent's sibling list for parent to collect it */
    470 	q = p->p_pptr;
    471 	q->p_nstopchild++;
    472 	if (LIST_FIRST(&q->p_children) != p) {
    473 		/* Put child where it can be found quickly */
    474 		LIST_REMOVE(p, p_sibling);
    475 		LIST_INSERT_HEAD(&q->p_children, p, p_sibling);
    476 	}
    477 
    478 	/*
    479 	 * Notify parent that we're gone.  If parent has the P_NOCLDWAIT
    480 	 * flag set, notify init instead (and hope it will handle
    481 	 * this situation).
    482 	 */
    483 	if (q->p_flag & (PK_NOCLDWAIT|PK_CLDSIGIGN)) {
    484 		proc_reparent(p, initproc);
    485 		wakeinit = 1;
    486 
    487 		/*
    488 		 * If this was the last child of our parent, notify
    489 		 * parent, so in case he was wait(2)ing, he will
    490 		 * continue.
    491 		 */
    492 		if (LIST_FIRST(&q->p_children) == NULL)
    493 			cv_broadcast(&q->p_waitcv);
    494 	}
    495 
    496 	/* Reload parent pointer, since p may have been reparented above */
    497 	q = p->p_pptr;
    498 
    499 	if (__predict_false((p->p_slflag & PSL_FSTRACE) == 0 && p->p_exitsig != 0)) {
    500 		exit_psignal(p, q, &ksi);
    501 		kpsignal(q, &ksi, NULL);
    502 	}
    503 
    504 	/* Calculate the final rusage info.  */
    505 	calcru(p, &p->p_stats->p_ru.ru_utime, &p->p_stats->p_ru.ru_stime,
    506 	    NULL, NULL);
    507 
    508 	if (wakeinit)
    509 		cv_broadcast(&initproc->p_waitcv);
    510 
    511 	callout_destroy(&l->l_timeout_ch);
    512 
    513 	/*
    514 	 * Remaining lwp resources will be freed in lwp_exit2() once we've
    515 	 * switch to idle context; at that point, we will be marked as a
    516 	 * full blown zombie.
    517 	 */
    518 	mutex_enter(p->p_lock);
    519 	lwp_drainrefs(l);
    520 	lwp_lock(l);
    521 	l->l_prflag &= ~LPR_DETACHED;
    522 	l->l_stat = LSZOMB;
    523 	lwp_unlock(l);
    524 	KASSERT(curlwp == l);
    525 	KASSERT(p->p_nrlwps == 1);
    526 	KASSERT(p->p_nlwps == 1);
    527 	p->p_stat = SZOMB;
    528 	p->p_nrlwps--;
    529 	p->p_nzlwps++;
    530 	p->p_ndlwps = 0;
    531 	mutex_exit(p->p_lock);
    532 
    533 	/*
    534 	 * Signal the parent to collect us, and drop the proclist lock.
    535 	 * Drop debugger/procfs lock; no new references can be gained.
    536 	 */
    537 	cv_broadcast(&p->p_pptr->p_waitcv);
    538 	mutex_exit(proc_lock);
    539 	rw_exit(&p->p_reflock);
    540 
    541 	/* Verify that we hold no locks other than the kernel lock. */
    542 	LOCKDEBUG_BARRIER(&kernel_lock, 0);
    543 
    544 	/*
    545 	 * NOTE: WE ARE NO LONGER ALLOWED TO SLEEP!
    546 	 */
    547 
    548 	/*
    549 	 * Give machine-dependent code a chance to free any MD LWP
    550 	 * resources.  This must be done before uvm_lwp_exit(), in
    551 	 * case these resources are in the PCB.
    552 	 */
    553 #ifndef __NO_CPU_LWP_FREE
    554 	cpu_lwp_free(l, 1);
    555 #endif
    556 	pmap_deactivate(l);
    557 
    558 	/* This process no longer needs to hold the kernel lock. */
    559 #ifdef notyet
    560 	/* XXXSMP hold in lwp_userret() */
    561 	KERNEL_UNLOCK_LAST(l);
    562 #else
    563 	KERNEL_UNLOCK_ALL(l, NULL);
    564 #endif
    565 
    566 	lwp_exit_switchaway(l);
    567 }
    568 
    569 void
    570 exit_lwps(struct lwp *l)
    571 {
    572 	struct proc *p;
    573 	struct lwp *l2;
    574 	int error;
    575 	lwpid_t waited;
    576 	int nlocks;
    577 
    578 	KERNEL_UNLOCK_ALL(l, &nlocks);
    579 
    580 	p = l->l_proc;
    581 	KASSERT(mutex_owned(p->p_lock));
    582 
    583  retry:
    584 	/*
    585 	 * Interrupt LWPs in interruptable sleep, unsuspend suspended
    586 	 * LWPs and then wait for everyone else to finish.
    587 	 */
    588 	LIST_FOREACH(l2, &p->p_lwps, l_sibling) {
    589 		if (l2 == l)
    590 			continue;
    591 		lwp_lock(l2);
    592 		l2->l_flag |= LW_WEXIT;
    593 		if ((l2->l_stat == LSSLEEP && (l2->l_flag & LW_SINTR)) ||
    594 		    l2->l_stat == LSSUSPENDED || l2->l_stat == LSSTOP) {
    595 		    	/* setrunnable() will release the lock. */
    596 			setrunnable(l2);
    597 			DPRINTF(("exit_lwps: Made %d.%d runnable\n",
    598 			    p->p_pid, l2->l_lid));
    599 			continue;
    600 		}
    601 		lwp_unlock(l2);
    602 	}
    603 	while (p->p_nlwps > 1) {
    604 		DPRINTF(("exit_lwps: waiting for %d LWPs (%d zombies)\n",
    605 		    p->p_nlwps, p->p_nzlwps));
    606 		error = lwp_wait1(l, 0, &waited, LWPWAIT_EXITCONTROL);
    607 		if (p->p_nlwps == 1)
    608 			break;
    609 		if (error == EDEADLK) {
    610 			/*
    611 			 * LWPs can get suspended/slept behind us.
    612 			 * (eg. sa_setwoken)
    613 			 * kick them again and retry.
    614 			 */
    615 			goto retry;
    616 		}
    617 		if (error)
    618 			panic("exit_lwps: lwp_wait1 failed with error %d",
    619 			    error);
    620 		DPRINTF(("exit_lwps: Got LWP %d from lwp_wait1()\n", waited));
    621 	}
    622 
    623 	KERNEL_LOCK(nlocks, l);
    624 	KASSERT(p->p_nlwps == 1);
    625 }
    626 
    627 int
    628 do_sys_wait(struct lwp *l, int *pid, int *status, int options,
    629     struct rusage *ru, int *was_zombie)
    630 {
    631 	struct proc	*child;
    632 	int		error;
    633 
    634 	mutex_enter(proc_lock);
    635 	error = find_stopped_child(l->l_proc, *pid, options, &child, status);
    636 
    637 	if (child == NULL) {
    638 		mutex_exit(proc_lock);
    639 		*pid = 0;
    640 		return error;
    641 	}
    642 
    643 	*pid = child->p_pid;
    644 
    645 	if (child->p_stat == SZOMB) {
    646 		/* proc_free() will release the proc_lock. */
    647 		*was_zombie = 1;
    648 		if (options & WNOWAIT)
    649 			mutex_exit(proc_lock);
    650 		else {
    651 			proc_free(child, ru);
    652 		}
    653 	} else {
    654 		/* Child state must have been SSTOP. */
    655 		*was_zombie = 0;
    656 		mutex_exit(proc_lock);
    657 		*status = W_STOPCODE(*status);
    658 	}
    659 
    660 	return 0;
    661 }
    662 
    663 int
    664 sys_wait4(struct lwp *l, const struct sys_wait4_args *uap, register_t *retval)
    665 {
    666 	/* {
    667 		syscallarg(int)			pid;
    668 		syscallarg(int *)		status;
    669 		syscallarg(int)			options;
    670 		syscallarg(struct rusage *)	rusage;
    671 	} */
    672 	int		status, error;
    673 	int		was_zombie;
    674 	struct rusage	ru;
    675 	int pid = SCARG(uap, pid);
    676 
    677 	error = do_sys_wait(l, &pid, &status, SCARG(uap, options),
    678 	    SCARG(uap, rusage) != NULL ? &ru : NULL, &was_zombie);
    679 
    680 	retval[0] = pid;
    681 	if (pid == 0)
    682 		return error;
    683 
    684 	if (SCARG(uap, rusage))
    685 		error = copyout(&ru, SCARG(uap, rusage), sizeof(ru));
    686 
    687 	if (error == 0 && SCARG(uap, status))
    688 		error = copyout(&status, SCARG(uap, status), sizeof(status));
    689 
    690 	return error;
    691 }
    692 
    693 /*
    694  * Scan list of child processes for a child process that has stopped or
    695  * exited.  Used by sys_wait4 and 'compat' equivalents.
    696  *
    697  * Must be called with the proc_lock held, and may release while waiting.
    698  */
    699 static int
    700 find_stopped_child(struct proc *parent, pid_t pid, int options,
    701 		   struct proc **child_p, int *status_p)
    702 {
    703 	struct proc *child, *dead;
    704 	int error;
    705 
    706 	KASSERT(mutex_owned(proc_lock));
    707 
    708 	if (options & ~(WUNTRACED|WNOHANG|WALTSIG|WALLSIG)
    709 	    && !(options & WOPTSCHECKED)) {
    710 		*child_p = NULL;
    711 		return EINVAL;
    712 	}
    713 
    714 	if (pid == 0 && !(options & WOPTSCHECKED))
    715 		pid = -parent->p_pgid;
    716 
    717 	for (;;) {
    718 		error = ECHILD;
    719 		dead = NULL;
    720 
    721 		LIST_FOREACH(child, &parent->p_children, p_sibling) {
    722 			if (pid >= 0) {
    723 				if (child->p_pid != pid) {
    724 					child = p_find(pid, PFIND_ZOMBIE |
    725 					    PFIND_LOCKED);
    726 					if (child == NULL ||
    727 					    child->p_pptr != parent) {
    728 						child = NULL;
    729 						break;
    730 					}
    731 				}
    732 			} else if (pid != WAIT_ANY && child->p_pgid != -pid) {
    733 				/* Child not in correct pgrp */
    734 				continue;
    735 			}
    736 
    737 			/*
    738 			 * Wait for processes with p_exitsig != SIGCHLD
    739 			 * processes only if WALTSIG is set; wait for
    740 			 * processes with p_exitsig == SIGCHLD only
    741 			 * if WALTSIG is clear.
    742 			 */
    743 			if (((options & WALLSIG) == 0) &&
    744 			    (options & WALTSIG ? child->p_exitsig == SIGCHLD
    745 						: P_EXITSIG(child) != SIGCHLD)){
    746 				if (child->p_pid == pid) {
    747 					child = NULL;
    748 					break;
    749 				}
    750 				continue;
    751 			}
    752 
    753 			error = 0;
    754 			if ((options & WNOZOMBIE) == 0) {
    755 				if (child->p_stat == SZOMB)
    756 					break;
    757 				if (child->p_stat == SDEAD) {
    758 					/*
    759 					 * We may occasionally arrive here
    760 					 * after receiving a signal, but
    761 					 * immediatley before the child
    762 					 * process is zombified.  The wait
    763 					 * will be short, so avoid returning
    764 					 * to userspace.
    765 					 */
    766 					dead = child;
    767 				}
    768 			}
    769 
    770 			if (child->p_stat == SSTOP &&
    771 			    child->p_waited == 0 &&
    772 			    (child->p_slflag & PSL_TRACED ||
    773 			    options & WUNTRACED)) {
    774 				if ((options & WNOWAIT) == 0) {
    775 					child->p_waited = 1;
    776 					parent->p_nstopchild--;
    777 				}
    778 				break;
    779 			}
    780 			if (parent->p_nstopchild == 0 || child->p_pid == pid) {
    781 				child = NULL;
    782 				break;
    783 			}
    784 		}
    785 
    786 		if (child != NULL || error != 0 ||
    787 		    ((options & WNOHANG) != 0 && dead == NULL)) {
    788 		    	if (child != NULL) {
    789 			    	*status_p = child->p_xstat;
    790 			}
    791 			*child_p = child;
    792 			return error;
    793 		}
    794 
    795 		/*
    796 		 * Wait for another child process to stop.
    797 		 */
    798 		error = cv_wait_sig(&parent->p_waitcv, proc_lock);
    799 
    800 		if (error != 0) {
    801 			*child_p = NULL;
    802 			return error;
    803 		}
    804 	}
    805 }
    806 
    807 /*
    808  * Free a process after parent has taken all the state info.  Must be called
    809  * with the proclist lock held, and will release before returning.
    810  *
    811  * *ru is returned to the caller, and must be freed by the caller.
    812  */
    813 static void
    814 proc_free(struct proc *p, struct rusage *ru)
    815 {
    816 	struct proc *parent;
    817 	struct lwp *l;
    818 	ksiginfo_t ksi;
    819 	kauth_cred_t cred1, cred2;
    820 	uid_t uid;
    821 
    822 	KASSERT(mutex_owned(proc_lock));
    823 	KASSERT(p->p_nlwps == 1);
    824 	KASSERT(p->p_nzlwps == 1);
    825 	KASSERT(p->p_nrlwps == 0);
    826 	KASSERT(p->p_stat == SZOMB);
    827 
    828 	/*
    829 	 * If we got the child via ptrace(2) or procfs, and
    830 	 * the parent is different (meaning the process was
    831 	 * attached, rather than run as a child), then we need
    832 	 * to give it back to the old parent, and send the
    833 	 * parent the exit signal.  The rest of the cleanup
    834 	 * will be done when the old parent waits on the child.
    835 	 */
    836 	if ((p->p_slflag & PSL_TRACED) != 0) {
    837 		parent = p->p_pptr;
    838 		if (p->p_opptr != parent){
    839 			mutex_enter(p->p_lock);
    840 			p->p_slflag &= ~(PSL_TRACED|PSL_FSTRACE|PSL_SYSCALL);
    841 			mutex_exit(p->p_lock);
    842 			parent = p->p_opptr;
    843 			if (parent == NULL)
    844 				parent = initproc;
    845 			proc_reparent(p, parent);
    846 			p->p_opptr = NULL;
    847 			if (p->p_exitsig != 0) {
    848 				exit_psignal(p, parent, &ksi);
    849 				kpsignal(parent, &ksi, NULL);
    850 			}
    851 			cv_broadcast(&parent->p_waitcv);
    852 			mutex_exit(proc_lock);
    853 			return;
    854 		}
    855 	}
    856 
    857 	/*
    858 	 * Finally finished with old proc entry.  Unlink it from its process
    859 	 * group.
    860 	 */
    861 	leavepgrp(p);
    862 
    863 	parent = p->p_pptr;
    864 	sched_proc_exit(parent, p);
    865 
    866 	/*
    867 	 * Add child times of exiting process onto its own times.
    868 	 * This cannot be done any earlier else it might get done twice.
    869 	 */
    870 	l = LIST_FIRST(&p->p_lwps);
    871 	p->p_stats->p_ru.ru_nvcsw += (l->l_ncsw - l->l_nivcsw);
    872 	p->p_stats->p_ru.ru_nivcsw += l->l_nivcsw;
    873 	ruadd(&p->p_stats->p_ru, &l->l_ru);
    874 	ruadd(&p->p_stats->p_ru, &p->p_stats->p_cru);
    875 	ruadd(&parent->p_stats->p_cru, &p->p_stats->p_ru);
    876 	if (ru != NULL)
    877 		*ru = p->p_stats->p_ru;
    878 	p->p_xstat = 0;
    879 
    880 	/*
    881 	 * At this point we are going to start freeing the final resources.
    882 	 * If anyone tries to access the proc structure after here they will
    883 	 * get a shock - bits are missing.  Attempt to make it hard!  We
    884 	 * don't bother with any further locking past this point.
    885 	 */
    886 	p->p_stat = SIDL;		/* not even a zombie any more */
    887 	LIST_REMOVE(p, p_list);	/* off zombproc */
    888 	parent = p->p_pptr;
    889 	p->p_pptr->p_nstopchild--;
    890 	LIST_REMOVE(p, p_sibling);
    891 
    892 	/*
    893 	 * Let pid be reallocated.
    894 	 */
    895 	proc_free_pid(p);
    896 	mutex_exit(proc_lock);
    897 
    898 	/*
    899 	 * Delay release until after lwp_free.
    900 	 */
    901 	cred2 = l->l_cred;
    902 
    903 	/*
    904 	 * Free the last LWP's resources.
    905 	 *
    906 	 * lwp_free ensures the LWP is no longer running on another CPU.
    907 	 */
    908 	lwp_free(l, false, true);
    909 
    910 	/*
    911 	 * Now no one except us can reach the process p.
    912 	 */
    913 
    914 	/*
    915 	 * Decrement the count of procs running with this uid.
    916 	 */
    917 	cred1 = p->p_cred;
    918 	uid = kauth_cred_getuid(cred1);
    919 	(void)chgproccnt(uid, -1);
    920 
    921 	/*
    922 	 * Release substructures.
    923 	 */
    924 
    925 	limfree(p->p_limit);
    926 	pstatsfree(p->p_stats);
    927 	kauth_cred_free(cred1);
    928 	kauth_cred_free(cred2);
    929 
    930 	/*
    931 	 * Release reference to text vnode
    932 	 */
    933 	if (p->p_textvp)
    934 		vrele(p->p_textvp);
    935 
    936 	mutex_destroy(&p->p_auxlock);
    937 	mutex_obj_free(p->p_lock);
    938 	mutex_destroy(&p->p_stmutex);
    939 	cv_destroy(&p->p_waitcv);
    940 	cv_destroy(&p->p_lwpcv);
    941 	rw_destroy(&p->p_reflock);
    942 
    943 	proc_free_mem(p);
    944 }
    945 
    946 /*
    947  * make process 'parent' the new parent of process 'child'.
    948  *
    949  * Must be called with proc_lock held.
    950  */
    951 void
    952 proc_reparent(struct proc *child, struct proc *parent)
    953 {
    954 
    955 	KASSERT(mutex_owned(proc_lock));
    956 
    957 	if (child->p_pptr == parent)
    958 		return;
    959 
    960 	if (child->p_stat == SZOMB ||
    961 	    (child->p_stat == SSTOP && !child->p_waited)) {
    962 		child->p_pptr->p_nstopchild--;
    963 		parent->p_nstopchild++;
    964 	}
    965 	if (parent == initproc)
    966 		child->p_exitsig = SIGCHLD;
    967 
    968 	LIST_REMOVE(child, p_sibling);
    969 	LIST_INSERT_HEAD(&parent->p_children, child, p_sibling);
    970 	child->p_pptr = parent;
    971 	child->p_ppid = parent->p_pid;
    972 }
    973