The Design and Implementation of the FreeBSD Operating System, Second Edition
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sys/kern/kern_exit.c

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    1 /*      $NetBSD: kern_exit.c,v 1.139 2004/03/14 01:08:47 cl Exp $       */
    2 
    3 /*-
    4  * Copyright (c) 1998, 1999 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.
   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  * 3. All advertising materials mentioning features or use of this software
   20  *    must display the following acknowledgement:
   21  *      This product includes software developed by the NetBSD
   22  *      Foundation, Inc. and its contributors.
   23  * 4. Neither the name of The NetBSD Foundation nor the names of its
   24  *    contributors may be used to endorse or promote products derived
   25  *    from this software without specific prior written permission.
   26  *
   27  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
   28  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
   29  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   30  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
   31  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   32  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   33  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   34  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   35  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   36  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   37  * POSSIBILITY OF SUCH DAMAGE.
   38  */
   39 
   40 /*
   41  * Copyright (c) 1982, 1986, 1989, 1991, 1993
   42  *      The Regents of the University of California.  All rights reserved.
   43  * (c) UNIX System Laboratories, Inc.
   44  * All or some portions of this file are derived from material licensed
   45  * to the University of California by American Telephone and Telegraph
   46  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
   47  * the permission of UNIX System Laboratories, Inc.
   48  *
   49  * Redistribution and use in source and binary forms, with or without
   50  * modification, are permitted provided that the following conditions
   51  * are met:
   52  * 1. Redistributions of source code must retain the above copyright
   53  *    notice, this list of conditions and the following disclaimer.
   54  * 2. Redistributions in binary form must reproduce the above copyright
   55  *    notice, this list of conditions and the following disclaimer in the
   56  *    documentation and/or other materials provided with the distribution.
   57  * 3. Neither the name of the University nor the names of its contributors
   58  *    may be used to endorse or promote products derived from this software
   59  *    without specific prior written permission.
   60  *
   61  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   62  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   63  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   64  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   65  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   66  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   67  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   68  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   69  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   70  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   71  * SUCH DAMAGE.
   72  *
   73  *      @(#)kern_exit.c 8.10 (Berkeley) 2/23/95
   74  */
   75 
   76 #include <sys/cdefs.h>
   77 __KERNEL_RCSID(0, "$NetBSD: kern_exit.c,v 1.139 2004/03/14 01:08:47 cl Exp $");
   78 
   79 #include "opt_ktrace.h"
   80 #include "opt_perfctrs.h"
   81 #include "opt_systrace.h"
   82 #include "opt_sysv.h"
   83 
   84 #include <sys/param.h>
   85 #include <sys/systm.h>
   86 #include <sys/ioctl.h>
   87 #include <sys/proc.h>
   88 #include <sys/tty.h>
   89 #include <sys/time.h>
   90 #include <sys/resource.h>
   91 #include <sys/kernel.h>
   92 #include <sys/ktrace.h>
   93 #include <sys/proc.h>
   94 #include <sys/buf.h>
   95 #include <sys/wait.h>
   96 #include <sys/file.h>
   97 #include <sys/vnode.h>
   98 #include <sys/syslog.h>
   99 #include <sys/malloc.h>
  100 #include <sys/pool.h>
  101 #include <sys/resourcevar.h>
  102 #if defined(PERFCTRS)
  103 #include <sys/pmc.h>
  104 #endif
  105 #include <sys/ptrace.h>
  106 #include <sys/acct.h>
  107 #include <sys/filedesc.h>
  108 #include <sys/ras.h>
  109 #include <sys/signalvar.h>
  110 #include <sys/sched.h>
  111 #include <sys/sa.h>
  112 #include <sys/savar.h>
  113 #include <sys/mount.h>
  114 #include <sys/syscallargs.h>
  115 #include <sys/systrace.h>
  116 
  117 #include <machine/cpu.h>
  118 
  119 #include <uvm/uvm_extern.h>
  120 
  121 #define DEBUG_EXIT
  122 
  123 #ifdef DEBUG_EXIT
  124 int debug_exit = 0;
  125 #define DPRINTF(x) if (debug_exit) printf x
  126 #else
  127 #define DPRINTF(x)
  128 #endif
  129 
  130 static void lwp_exit_hook(struct lwp *, void *);
  131 static void exit_psignal(struct proc *, struct proc *);
  132 
  133 /*
  134  * Fill in the appropriate signal information, and signal the parent.
  135  */
  136 static void
  137 exit_psignal(struct proc *p, struct proc *pp)
  138 {
  139         ksiginfo_t ksi;
  140 
  141         (void)memset(&ksi, 0, sizeof(ksi));
  142         if ((ksi.ksi_signo = P_EXITSIG(p)) == SIGCHLD) {
  143                 if (WIFSIGNALED(p->p_xstat)) {
  144                         if (WCOREDUMP(p->p_xstat))
  145                                 ksi.ksi_code = CLD_DUMPED;
  146                         else
  147                                 ksi.ksi_code = CLD_KILLED;
  148                 } else {
  149                         ksi.ksi_code = CLD_EXITED;
  150                 }
  151         }
  152         /*
  153          * we fill those in, even for non-SIGCHLD.
  154          */
  155         ksi.ksi_pid = p->p_pid;
  156         ksi.ksi_uid = p->p_ucred->cr_uid;
  157         ksi.ksi_status = p->p_xstat;
  158         /* XXX: is this still valid? */
  159         ksi.ksi_utime = p->p_ru->ru_utime.tv_sec;
  160         ksi.ksi_stime = p->p_ru->ru_stime.tv_sec;
  161         kpsignal(pp, &ksi, NULL);
  162 }
  163 
  164 /*
  165  * exit --
  166  *      Death of process.
  167  */
  168 int
  169 sys_exit(struct lwp *l, void *v, register_t *retval)
  170 {
  171         struct sys_exit_args /* {
  172                 syscallarg(int) rval;
  173         } */ *uap = v;
  174 
  175         /* Don't call exit1() multiple times in the same process.*/
  176         if (l->l_proc->p_flag & P_WEXIT)
  177                 lwp_exit(l);
  178 
  179         exit1(l, W_EXITCODE(SCARG(uap, rval), 0));
  180         /* NOTREACHED */
  181         return (0);
  182 }
  183 
  184 /*
  185  * Exit: deallocate address space and other resources, change proc state
  186  * to zombie, and unlink proc from allproc and parent's lists.  Save exit
  187  * status and rusage for wait().  Check for child processes and orphan them.
  188  */
  189 void
  190 exit1(struct lwp *l, int rv)
  191 {
  192         struct proc     *p, *q, *nq;
  193         int             s, sa;
  194 
  195         p = l->l_proc;
  196 
  197         if (__predict_false(p == initproc))
  198                 panic("init died (signal %d, exit %d)",
  199                     WTERMSIG(rv), WEXITSTATUS(rv));
  200 
  201         p->p_flag |= P_WEXIT;
  202         if (p->p_flag & P_STOPEXIT) {
  203                 int s;
  204 
  205                 sigminusset(&contsigmask, &p->p_sigctx.ps_siglist);
  206                 SCHED_LOCK(s);
  207                 p->p_stat = SSTOP;
  208                 l->l_stat = LSSTOP;
  209                 p->p_nrlwps--;
  210                 mi_switch(l, NULL);
  211                 SCHED_ASSERT_UNLOCKED();
  212                 splx(s);
  213         }
  214 
  215         DPRINTF(("exit1: %d.%d exiting.\n", p->p_pid, l->l_lid));
  216         /*
  217          * Disable scheduler activation upcalls. 
  218          * We're trying to get out of here. 
  219          */
  220         sa = 0;
  221         if (p->p_sa != NULL) {
  222                 l->l_flag &= ~L_SA;
  223 #if 0
  224                 p->p_flag &= ~P_SA;
  225 #endif
  226                 sa = 1;
  227         }
  228 
  229 #ifdef PGINPROF
  230         vmsizmon();
  231 #endif
  232         if (p->p_flag & P_PROFIL)
  233                 stopprofclock(p);
  234         p->p_ru = pool_get(&rusage_pool, PR_WAITOK);
  235         /*
  236          * If parent is waiting for us to exit or exec, P_PPWAIT is set; we
  237          * wake up the parent early to avoid deadlock.
  238          */
  239         if (p->p_flag & P_PPWAIT) {
  240                 p->p_flag &= ~P_PPWAIT;
  241                 wakeup(p->p_pptr);
  242         }
  243         sigfillset(&p->p_sigctx.ps_sigignore);
  244         sigemptyset(&p->p_sigctx.ps_siglist);
  245         p->p_sigctx.ps_sigcheck = 0;
  246         timers_free(p, TIMERS_ALL);
  247 
  248         if (sa || (p->p_nlwps > 1)) {
  249                 exit_lwps(l);
  250 
  251                 /*
  252                  * Collect thread u-areas.
  253                  */
  254                 uvm_uarea_drain(FALSE);
  255         }
  256 
  257 #if defined(__HAVE_RAS)
  258         ras_purgeall(p);
  259 #endif
  260 
  261         /*
  262          * Close open files and release open-file table.
  263          * This may block!
  264          */
  265         fdfree(p);
  266         cwdfree(p);
  267 
  268         doexithooks(p);
  269 
  270         if (SESS_LEADER(p)) {
  271                 struct session *sp = p->p_session;
  272                 struct tty *tp;
  273 
  274                 if (sp->s_ttyvp) {
  275                         int s;
  276                         /*
  277                          * Controlling process.
  278                          * Signal foreground pgrp,
  279                          * drain controlling terminal
  280                          * and revoke access to controlling terminal.
  281                          */
  282                         tp = sp->s_ttyp;
  283                         s = spltty();
  284                         TTY_LOCK(tp);
  285                         if (tp->t_session == sp) {
  286                                 if (tp->t_pgrp)
  287                                         pgsignal(tp->t_pgrp, SIGHUP, 1);
  288                                 /* we can't guarantee the revoke will do this */
  289                                 tp->t_pgrp = NULL;
  290                                 tp->t_session = NULL;
  291                                 TTY_UNLOCK(tp);
  292                                 splx(s);
  293                                 SESSRELE(sp);
  294                                 (void) ttywait(tp);
  295                                 /*
  296                                  * The tty could have been revoked
  297                                  * if we blocked.
  298                                  */
  299                                 if (sp->s_ttyvp)
  300                                         VOP_REVOKE(sp->s_ttyvp, REVOKEALL);
  301                         } else {
  302                                 TTY_UNLOCK(tp);
  303                                 splx(s);
  304                         }
  305                         if (sp->s_ttyvp)
  306                                 vrele(sp->s_ttyvp);
  307                         sp->s_ttyvp = NULL;
  308                         /*
  309                          * s_ttyp is not zero'd; we use this to indicate
  310                          * that the session once had a controlling terminal.
  311                          * (for logging and informational purposes)
  312                          */
  313                 }
  314                 sp->s_leader = NULL;
  315         }
  316         fixjobc(p, p->p_pgrp, 0);
  317         (void)acct_process(p);
  318 #ifdef KTRACE
  319         /* 
  320          * release trace file
  321          */
  322         ktrderef(p);
  323 #endif
  324 #ifdef SYSTRACE
  325         systrace_sys_exit(p);
  326 #endif
  327         /*
  328          * If emulation has process exit hook, call it now.
  329          */
  330         if (p->p_emul->e_proc_exit)
  331                 (*p->p_emul->e_proc_exit)(p);
  332 
  333         /*
  334          * Reset p_opptr pointer of all former children which got
  335          * traced by another process and were reparented. We reset
  336          * it to NULL here; the trace detach code then reparents
  337          * the child to initproc. We only check allproc list, since
  338          * eventual former children on zombproc list won't reference
  339          * p_opptr anymore.
  340          */
  341         s = proclist_lock_write();
  342         if (p->p_flag & P_CHTRACED) {
  343                 LIST_FOREACH(q, &allproc, p_list) {
  344                         if (q->p_opptr == p)
  345                                 q->p_opptr = NULL;
  346                 }
  347         }
  348 
  349         /*
  350          * Give orphaned children to init(8).
  351          */
  352         q = LIST_FIRST(&p->p_children);
  353         if (q)          /* only need this if any child is SZOMB */
  354                 wakeup(initproc);
  355         for (; q != NULL; q = nq) {
  356                 nq = LIST_NEXT(q, p_sibling);
  357 
  358                 /*
  359                  * Traced processes are killed since their existence
  360                  * means someone is screwing up. Since we reset the
  361                  * trace flags, the logic in sys_wait4() would not be
  362                  * triggered to reparent the process to its
  363                  * original parent, so we must do this here.
  364                  */
  365                 if (q->p_flag & P_TRACED) {
  366                         if (q->p_opptr != q->p_pptr) {
  367                                 struct proc *t = q->p_opptr;
  368                                 proc_reparent(q, t ? t : initproc);
  369                                 q->p_opptr = NULL;
  370                         } else
  371                                 proc_reparent(q, initproc);
  372                         q->p_flag &= ~(P_TRACED|P_WAITED|P_FSTRACE);
  373                         psignal(q, SIGKILL);
  374                 } else {
  375                         proc_reparent(q, initproc);
  376                 }
  377         }
  378         proclist_unlock_write(s);
  379 
  380         /*
  381          * Free the VM resources we're still holding on to.
  382          * We must do this from a valid thread because doing
  383          * so may block. This frees vmspace, which we don't
  384          * need anymore. The only remaining lwp is the one
  385          * we run at this moment, nothing runs in userland
  386          * anymore.
  387          */
  388         uvm_proc_exit(p);
  389 
  390         /*
  391          * Give machine-dependent code a chance to free any
  392          * MD LWP resources while we can still block. This must be done
  393          * before uvm_lwp_exit(), in case these resources are in the 
  394          * PCB.
  395          * THIS IS LAST BLOCKING OPERATION.
  396          */
  397 #ifndef __NO_CPU_LWP_FREE
  398         cpu_lwp_free(l, 1);
  399 #endif
  400 
  401         pmap_deactivate(l);
  402 
  403         /*
  404          * NOTE: WE ARE NO LONGER ALLOWED TO SLEEP!
  405          */
  406 
  407         /*
  408          * Save exit status and final rusage info, adding in child rusage
  409          * info and self times.
  410          * In order to pick up the time for the current execution, we must
  411          * do this before unlinking the lwp from l_list.
  412          */
  413         p->p_xstat = rv;
  414         *p->p_ru = p->p_stats->p_ru;
  415         calcru(p, &p->p_ru->ru_utime, &p->p_ru->ru_stime, NULL);
  416         ruadd(p->p_ru, &p->p_stats->p_cru);
  417 
  418         /*
  419          * Move proc from allproc to zombproc, it's now ready
  420          * to be collected by parent. Remaining lwp resources
  421          * will be freed in lwp_exit2() once we'd switch to idle
  422          * context.
  423          * Changing the state to SZOMB stops it being found by pfind().
  424          */
  425         s = proclist_lock_write();
  426         LIST_REMOVE(p, p_list);
  427         LIST_INSERT_HEAD(&zombproc, p, p_list);
  428         p->p_stat = SZOMB;
  429 
  430         LIST_REMOVE(l, l_list);
  431         LIST_REMOVE(l, l_sibling);
  432         l->l_flag |= L_DETACHED|L_PROCEXIT;     /* detached from proc too */
  433         l->l_stat = LSDEAD;
  434 
  435         p->p_nrlwps--;
  436         p->p_nlwps--;
  437 
  438         /* Put in front of parent's sibling list for parent to collect it */
  439         q = p->p_pptr;
  440         q->p_nstopchild++;
  441         if (LIST_FIRST(&q->p_children) != p) {
  442                 /* Put child where it can be found quickly */
  443                 LIST_REMOVE(p, p_sibling);
  444                 LIST_INSERT_HEAD(&q->p_children, p, p_sibling);
  445         }
  446 
  447         proclist_unlock_write(s);
  448 
  449         /*
  450          * Notify interested parties of our demise.
  451          */
  452         KNOTE(&p->p_klist, NOTE_EXIT);
  453 
  454 #if PERFCTRS
  455         /*
  456          * Save final PMC information in parent process & clean up.
  457          */
  458         if (PMC_ENABLED(p)) {
  459                 pmc_save_context(p);
  460                 pmc_accumulate(p->p_pptr, p);
  461                 pmc_process_exit(p);
  462         }
  463 #endif
  464 
  465         /*
  466          * Notify parent that we're gone.  If parent has the P_NOCLDWAIT
  467          * flag set, notify init instead (and hope it will handle
  468          * this situation).
  469          */
  470         if (p->p_pptr->p_flag & P_NOCLDWAIT) {
  471                 struct proc *pp = p->p_pptr;
  472                 proc_reparent(p, initproc);
  473 
  474                 /*
  475                  * If this was the last child of our parent, notify
  476                  * parent, so in case he was wait(2)ing, he will
  477                  * continue.
  478                  */
  479                 if (LIST_FIRST(&pp->p_children) == NULL)
  480                         wakeup(pp);
  481         }
  482 
  483         /* Wake up the parent so it can get exit status. */
  484         if ((p->p_flag & P_FSTRACE) == 0 && p->p_exitsig != 0)
  485                 exit_psignal(p, p->p_pptr);
  486         wakeup(p->p_pptr);
  487 
  488         /*
  489          * Release the process's signal state.
  490          */
  491         sigactsfree(p);
  492 
  493         /*
  494          * Clear curlwp after we've done all operations
  495          * that could block, and before tearing down the rest
  496          * of the process state that might be used from clock, etc.
  497          * Also, can't clear curlwp while we're still runnable,
  498          * as we're not on a run queue (we are current, just not
  499          * a proper proc any longer!).
  500          *
  501          * Other substructures are freed from wait().
  502          */
  503         curlwp = NULL;
  504         limfree(p->p_limit);
  505         pstatsfree(p->p_stats);
  506         p->p_limit = NULL;
  507 
  508         /* This process no longer needs to hold the kernel lock. */
  509         KERNEL_PROC_UNLOCK(l);
  510 
  511 #ifdef DEBUG
  512         /* Nothing should use the process link anymore */
  513         l->l_proc = NULL;
  514 #endif
  515 
  516         /*
  517          * Finally, call machine-dependent code to switch to a new
  518          * context (possibly the idle context).  Once we are no longer
  519          * using the dead lwp's stack, lwp_exit2() will be called
  520          * to arrange for the resources to be released.
  521          *
  522          * Note that cpu_exit() will end with a call equivalent to
  523          * cpu_switch(), finishing our execution (pun intended).
  524          */
  525 
  526         uvmexp.swtch++;
  527         cpu_exit(l);
  528 }
  529 
  530 void
  531 exit_lwps(struct lwp *l)
  532 {
  533         struct proc *p;
  534         struct lwp *l2;
  535         struct sadata_vp *vp;
  536         int s, error;
  537         lwpid_t         waited;
  538 
  539         p = l->l_proc;
  540 
  541         /* XXX SMP 
  542          * This would be the right place to IPI any LWPs running on 
  543          * other processors so that they can notice the userret exit hook.
  544          */
  545         p->p_userret = lwp_exit_hook;
  546         p->p_userret_arg = NULL;
  547 
  548         if (p->p_sa) {
  549                 SLIST_FOREACH(vp, &p->p_sa->sa_vps, savp_next) {
  550                         /*
  551                          * Make SA-cached LWPs normal process runnable
  552                          * LWPs so that they'll also self-destruct.
  553                          */
  554                         DPRINTF(("exit_lwps: Making cached LWPs of %d on VP %d runnable: ",
  555                                     p->p_pid, vp->savp_id));
  556                         SCHED_LOCK(s);
  557                         while ((l2 = sa_getcachelwp(vp)) != 0) {
  558                                 l2->l_priority = l2->l_usrpri;
  559                                 setrunnable(l2);
  560                                 DPRINTF(("%d ", l2->l_lid));
  561                         }
  562                         SCHED_UNLOCK(s);
  563                         DPRINTF(("\n"));
  564 
  565                         /*
  566                          * Clear wokenq, the LWPs on the queue will
  567                          * run below.
  568                          */
  569                         vp->savp_wokenq_head = NULL;
  570                 }
  571         }
  572         
  573         /*
  574          * Interrupt LWPs in interruptable sleep, unsuspend suspended
  575          * LWPs, make detached LWPs undetached (so we can wait for
  576          * them) and then wait for everyone else to finish.  
  577          */
  578         LIST_FOREACH(l2, &p->p_lwps, l_sibling) {
  579                 l2->l_flag &= ~(L_DETACHED|L_SA);
  580 
  581                 if ((l2->l_stat == LSSLEEP && (l2->l_flag & L_SINTR)) ||
  582                     l2->l_stat == LSSUSPENDED || l2->l_stat == LSSTOP) {
  583                         SCHED_LOCK(s);
  584                         setrunnable(l2);
  585                         SCHED_UNLOCK(s);
  586                         DPRINTF(("exit_lwps: Made %d.%d runnable\n",
  587                             p->p_pid, l2->l_lid));
  588                 }
  589         }
  590 
  591         
  592         while (p->p_nlwps > 1) {
  593                 DPRINTF(("exit_lwps: waiting for %d LWPs (%d runnable, %d zombies)\n", 
  594                     p->p_nlwps, p->p_nrlwps, p->p_nzlwps));
  595                 error = lwp_wait1(l, 0, &waited, LWPWAIT_EXITCONTROL);
  596                 if (error)
  597                         panic("exit_lwps: lwp_wait1 failed with error %d\n",
  598                             error);
  599                 DPRINTF(("exit_lwps: Got LWP %d from lwp_wait1()\n", waited));
  600         }       
  601 
  602         p->p_userret = NULL;
  603 }
  604 
  605 /* Wrapper function for use in p_userret */
  606 static void
  607 lwp_exit_hook(struct lwp *l, void *arg)
  608 {
  609         KERNEL_PROC_LOCK(l);
  610         lwp_exit(l);
  611 }
  612 
  613 int
  614 sys_wait4(struct lwp *l, void *v, register_t *retval)
  615 {
  616         struct sys_wait4_args /* {
  617                 syscallarg(int)                 pid;
  618                 syscallarg(int *)               status;
  619                 syscallarg(int)                 options;
  620                 syscallarg(struct rusage *)     rusage;
  621         } */ *uap = v;
  622         struct proc     *child, *parent;
  623         int             status, error;
  624 
  625         parent = l->l_proc;
  626 
  627         if (SCARG(uap, pid) == 0)
  628                 SCARG(uap, pid) = -parent->p_pgid;
  629         if (SCARG(uap, options) & ~(WUNTRACED|WNOHANG|WALTSIG|WALLSIG))
  630                 return (EINVAL);
  631 
  632         error = find_stopped_child(parent, SCARG(uap,pid), SCARG(uap,options),
  633                                 &child);
  634         if (error != 0)
  635                 return error;
  636         if (child == NULL) {
  637                 *retval = 0;
  638                 return 0;
  639         }
  640 
  641         /*
  642          * Collect child u-areas.
  643          */
  644         uvm_uarea_drain(FALSE);
  645 
  646         retval[0] = child->p_pid;
  647 
  648         if (child->p_stat == SZOMB) {
  649                 if (SCARG(uap, status)) {
  650                         status = child->p_xstat;        /* convert to int */
  651                         error = copyout(&status, SCARG(uap, status),
  652                                         sizeof(status));
  653                         if (error)
  654                                 return (error);
  655                 }
  656                 if (SCARG(uap, rusage)) {
  657                         error = copyout(child->p_ru, SCARG(uap, rusage),
  658                                     sizeof(struct rusage));
  659                         if (error)
  660                                 return (error);
  661                 }
  662 
  663                 proc_free(child);
  664                 return 0;
  665         }
  666 
  667         /* child state must be SSTOP */
  668         if (SCARG(uap, status)) {
  669                 status = W_STOPCODE(child->p_xstat);
  670                 return copyout(&status, SCARG(uap, status), sizeof(status));
  671         }
  672         return 0;
  673 }
  674 
  675 /*
  676  * Scan list of child processes for a child process that has stopped or
  677  * exited.  Used by sys_wait4 and 'compat' equivalents.
  678  */
  679 int
  680 find_stopped_child(struct proc *parent, pid_t pid, int options,
  681         struct proc **child_p)
  682 {
  683         struct proc *child;
  684         int error;
  685 
  686         for (;;) {
  687                 proclist_lock_read();
  688                 error = ECHILD;
  689                 LIST_FOREACH(child, &parent->p_children, p_sibling) {
  690                         if (pid >= 0) {
  691                                 if (child->p_pid != pid) {
  692                                         child = p_find(pid, PFIND_ZOMBIE |
  693                                                                 PFIND_LOCKED);
  694                                         if (child == NULL
  695                                             || child->p_pptr != parent) {
  696                                                 child = NULL;
  697                                                 break;
  698                                         }
  699                                 }
  700                         } else
  701                                 if (pid != WAIT_ANY && child->p_pgid != -pid)
  702                                         /* child not in correct pgrp */
  703                                         continue;
  704                         /*
  705                          * Wait for processes with p_exitsig != SIGCHLD
  706                          * processes only if WALTSIG is set; wait for
  707                          * processes with p_exitsig == SIGCHLD only
  708                          * if WALTSIG is clear.
  709                          */
  710                         if (((options & WALLSIG) == 0) &&
  711                             (options & WALTSIG ? child->p_exitsig == SIGCHLD
  712                                                 : P_EXITSIG(child) != SIGCHLD)){
  713                                 if (child->p_pid == pid) {
  714                                         child = NULL;
  715                                         break;
  716                                 }
  717                                 continue;
  718                         }
  719 
  720                         error = 0;
  721                         if (child->p_stat == SZOMB && !(options & WNOZOMBIE))
  722                                 break;
  723 
  724                         if (child->p_stat == SSTOP &&
  725                             (child->p_flag & P_WAITED) == 0 &&
  726                             (child->p_flag & P_TRACED || options & WUNTRACED)) {
  727                                 if ((options & WNOWAIT) == 0) {
  728                                         child->p_flag |= P_WAITED;
  729                                         parent->p_nstopchild--;
  730                                 }
  731                                 break;
  732                         }
  733                         if (parent->p_nstopchild == 0 || child->p_pid == pid) {
  734                                 child = NULL;
  735                                 break;
  736                         }
  737                 }
  738                 proclist_unlock_read();
  739                 if (child != NULL || error != 0 || options & WNOHANG) {
  740                         *child_p = child;
  741                         return error;
  742                 }
  743                 error = tsleep(parent, PWAIT | PCATCH, "wait", 0);
  744                 if (error != 0)
  745                         return error;
  746         }
  747 }
  748 
  749 /*
  750  * Free a process after parent has taken all the state info.
  751  */
  752 void
  753 proc_free(struct proc *p)
  754 {
  755         struct proc *parent = p->p_pptr;
  756         int s;
  757 
  758         KASSERT(p->p_nlwps == 0);
  759         KASSERT(p->p_nzlwps == 0);
  760         KASSERT(p->p_nrlwps == 0);
  761         KASSERT(LIST_EMPTY(&p->p_lwps));
  762 
  763         /*
  764          * If we got the child via ptrace(2) or procfs, and
  765          * the parent is different (meaning the process was
  766          * attached, rather than run as a child), then we need
  767          * to give it back to the old parent, and send the
  768          * parent the exit signal.  The rest of the cleanup
  769          * will be done when the old parent waits on the child.
  770          */
  771         if ((p->p_flag & P_TRACED) && p->p_opptr != parent){
  772                 parent = p->p_opptr;
  773                 if (parent == NULL)
  774                         parent = initproc;
  775                 proc_reparent(p, parent);
  776                 p->p_opptr = NULL;
  777                 p->p_flag &= ~(P_TRACED|P_WAITED|P_FSTRACE);
  778                 if (p->p_exitsig != 0)
  779                         exit_psignal(p, parent);
  780                 wakeup(parent);
  781                 return;
  782         }
  783 
  784         scheduler_wait_hook(parent, p);
  785         p->p_xstat = 0;
  786 
  787         ruadd(&parent->p_stats->p_cru, p->p_ru);
  788 
  789         /*
  790          * At this point we are going to start freeing the final resources.
  791          * If anyone tries to access the proc structure after here they
  792          * will get a shock - bits are missing.
  793          * Attempt to make it hard!
  794          */
  795 
  796         p->p_stat = SIDL;               /* not even a zombie any more */
  797 
  798         pool_put(&rusage_pool, p->p_ru);
  799 
  800         /*
  801          * Finally finished with old proc entry.
  802          * Unlink it from its process group and free it.
  803          */
  804         leavepgrp(p);
  805 
  806         s = proclist_lock_write();
  807         LIST_REMOVE(p, p_list); /* off zombproc */
  808         p->p_pptr->p_nstopchild--;
  809         LIST_REMOVE(p, p_sibling);
  810         proclist_unlock_write(s);
  811 
  812         /*
  813          * Decrement the count of procs running with this uid.
  814          */
  815         (void)chgproccnt(p->p_cred->p_ruid, -1);
  816 
  817         /*
  818          * Free up credentials.
  819          */
  820         if (--p->p_cred->p_refcnt == 0) {
  821                 crfree(p->p_cred->pc_ucred);
  822                 pool_put(&pcred_pool, p->p_cred);
  823         }
  824 
  825         /*
  826          * Release reference to text vnode
  827          */
  828         if (p->p_textvp)
  829                 vrele(p->p_textvp);
  830 
  831         /* Release any SA state. */
  832         if (p->p_sa)
  833                 sa_release(p);
  834 
  835         /* Free proc structure and let pid be reallocated */
  836         proc_free_mem(p);
  837 }
  838 
  839 /*
  840  * make process 'parent' the new parent of process 'child'.
  841  *
  842  * Must be called with proclist_lock_write() held.
  843  */
  844 void
  845 proc_reparent(struct proc *child, struct proc *parent)
  846 {
  847 
  848         if (child->p_pptr == parent)
  849                 return;
  850 
  851         if (child->p_stat == SZOMB
  852             || (child->p_stat == SSTOP && !(child->p_flag & P_WAITED))) {
  853                 child->p_pptr->p_nstopchild--;
  854                 parent->p_nstopchild++;
  855         }
  856         if (parent == initproc)
  857                 child->p_exitsig = SIGCHLD;
  858 
  859         LIST_REMOVE(child, p_sibling);
  860         LIST_INSERT_HEAD(&parent->p_children, child, p_sibling);
  861         child->p_pptr = parent;
  862 }

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