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

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    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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