FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_exit.c

     /*-
      * Copyright (c) 1982, 1986, 1989, 1991, 1993
      *      The Regents of the University of California.  All rights reserved.
      * (c) UNIX System Laboratories, Inc.
      * All or some portions of this file are derived from material licensed
      * to the University of California by American Telephone and Telegraph
      * Co. or Unix System Laboratories, Inc. and are reproduced herein with
      * the permission of UNIX System Laboratories, Inc.
      *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 4. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)kern_exit.c 8.7 (Berkeley) 2/12/94
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD: releng/9.1/sys/kern/kern_exit.c 233920 2012-04-05 10:33:39Z kib $");
    
    #include "opt_compat.h"
    #include "opt_kdtrace.h"
    #include "opt_ktrace.h"
    #include "opt_procdesc.h"
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/sysproto.h>
    #include <sys/capability.h>
    #include <sys/eventhandler.h>
    #include <sys/kernel.h>
    #include <sys/malloc.h>
    #include <sys/lock.h>
    #include <sys/mutex.h>
    #include <sys/proc.h>
    #include <sys/procdesc.h>
    #include <sys/pioctl.h>
    #include <sys/jail.h>
    #include <sys/tty.h>
    #include <sys/wait.h>
    #include <sys/vmmeter.h>
    #include <sys/vnode.h>
    #include <sys/racct.h>
    #include <sys/resourcevar.h>
    #include <sys/sbuf.h>
    #include <sys/signalvar.h>
    #include <sys/sched.h>
    #include <sys/sx.h>
    #include <sys/syscallsubr.h>
    #include <sys/syslog.h>
    #include <sys/ptrace.h>
    #include <sys/acct.h>           /* for acct_process() function prototype */
    #include <sys/filedesc.h>
    #include <sys/sdt.h>
    #include <sys/shm.h>
    #include <sys/sem.h>
    #ifdef KTRACE
    #include <sys/ktrace.h>
    #endif
    
    #include <security/audit/audit.h>
    #include <security/mac/mac_framework.h>
    
    #include <vm/vm.h>
    #include <vm/vm_extern.h>
    #include <vm/vm_param.h>
    #include <vm/pmap.h>
    #include <vm/vm_map.h>
    #include <vm/vm_page.h>
    #include <vm/uma.h>
    
    #ifdef KDTRACE_HOOKS
    #include <sys/dtrace_bsd.h>
    dtrace_execexit_func_t  dtrace_fasttrap_exit;
    #endif
    
    SDT_PROVIDER_DECLARE(proc);
    SDT_PROBE_DEFINE(proc, kernel, , exit, exit);
    SDT_PROBE_ARGTYPE(proc, kernel, , exit, 0, "int");
    
   /* Hook for NFS teardown procedure. */
   void (*nlminfo_release_p)(struct proc *p);
   
   static void
   clear_orphan(struct proc *p)
   {
   
           PROC_LOCK_ASSERT(p, MA_OWNED);
   
           if (p->p_flag & P_ORPHAN) {
                   LIST_REMOVE(p, p_orphan);
                   p->p_flag &= ~P_ORPHAN;
           }
   }
   
   /*
    * exit -- death of process.
    */
   void
   sys_sys_exit(struct thread *td, struct sys_exit_args *uap)
   {
   
           exit1(td, W_EXITCODE(uap->rval, 0));
           /* NOTREACHED */
   }
   
   /*
    * Exit: deallocate address space and other resources, change proc state to
    * zombie, and unlink proc from allproc and parent's lists.  Save exit status
    * and rusage for wait().  Check for child processes and orphan them.
    */
   void
   exit1(struct thread *td, int rv)
   {
           struct proc *p, *nq, *q;
           struct vnode *vtmp;
           struct vnode *ttyvp = NULL;
           struct plimit *plim;
           int locked;
   
           mtx_assert(&Giant, MA_NOTOWNED);
   
           p = td->td_proc;
           /*
            * XXX in case we're rebooting we just let init die in order to
            * work around an unsolved stack overflow seen very late during
            * shutdown on sparc64 when the gmirror worker process exists.
            */ 
           if (p == initproc && rebooting == 0) {
                   printf("init died (signal %d, exit %d)\n",
                       WTERMSIG(rv), WEXITSTATUS(rv));
                   panic("Going nowhere without my init!");
           }
   
           /*
            * MUST abort all other threads before proceeding past here.
            */
           PROC_LOCK(p);
           while (p->p_flag & P_HADTHREADS) {
                   /*
                    * First check if some other thread got here before us..
                    * if so, act apropriatly, (exit or suspend);
                    */
                   thread_suspend_check(0);
   
                   /*
                    * Kill off the other threads. This requires
                    * some co-operation from other parts of the kernel
                    * so it may not be instantaneous.  With this state set
                    * any thread entering the kernel from userspace will
                    * thread_exit() in trap().  Any thread attempting to
                    * sleep will return immediately with EINTR or EWOULDBLOCK
                    * which will hopefully force them to back out to userland
                    * freeing resources as they go.  Any thread attempting
                    * to return to userland will thread_exit() from userret().
                    * thread_exit() will unsuspend us when the last of the
                    * other threads exits.
                    * If there is already a thread singler after resumption,
                    * calling thread_single will fail; in that case, we just
                    * re-check all suspension request, the thread should
                    * either be suspended there or exit.
                    */
                   if (! thread_single(SINGLE_EXIT))
                           break;
   
                   /*
                    * All other activity in this process is now stopped.
                    * Threading support has been turned off.
                    */
           }
           KASSERT(p->p_numthreads == 1,
               ("exit1: proc %p exiting with %d threads", p, p->p_numthreads));
           racct_sub(p, RACCT_NTHR, 1);
           /*
            * Wakeup anyone in procfs' PIOCWAIT.  They should have a hold
            * on our vmspace, so we should block below until they have
            * released their reference to us.  Note that if they have
            * requested S_EXIT stops we will block here until they ack
            * via PIOCCONT.
            */
           _STOPEVENT(p, S_EXIT, rv);
   
           /*
            * Note that we are exiting and do another wakeup of anyone in
            * PIOCWAIT in case they aren't listening for S_EXIT stops or
            * decided to wait again after we told them we are exiting.
            */
           p->p_flag |= P_WEXIT;
           wakeup(&p->p_stype);
   
           /*
            * Wait for any processes that have a hold on our vmspace to
            * release their reference.
            */
           while (p->p_lock > 0)
                   msleep(&p->p_lock, &p->p_mtx, PWAIT, "exithold", 0);
   
           p->p_xstat = rv;        /* Let event handler change exit status */
           PROC_UNLOCK(p);
           /* Drain the limit callout while we don't have the proc locked */
           callout_drain(&p->p_limco);
   
   #ifdef AUDIT
           /*
            * The Sun BSM exit token contains two components: an exit status as
            * passed to exit(), and a return value to indicate what sort of exit
            * it was.  The exit status is WEXITSTATUS(rv), but it's not clear
            * what the return value is.
            */
           AUDIT_ARG_EXIT(WEXITSTATUS(rv), 0);
           AUDIT_SYSCALL_EXIT(0, td);
   #endif
   
           /* Are we a task leader? */
           if (p == p->p_leader) {
                   mtx_lock(&ppeers_lock);
                   q = p->p_peers;
                   while (q != NULL) {
                           PROC_LOCK(q);
                           kern_psignal(q, SIGKILL);
                           PROC_UNLOCK(q);
                           q = q->p_peers;
                   }
                   while (p->p_peers != NULL)
                           msleep(p, &ppeers_lock, PWAIT, "exit1", 0);
                   mtx_unlock(&ppeers_lock);
           }
   
           /*
            * Check if any loadable modules need anything done at process exit.
            * E.g. SYSV IPC stuff
            * XXX what if one of these generates an error?
            */
           EVENTHANDLER_INVOKE(process_exit, p);
   
           /*
            * If parent is waiting for us to exit or exec,
            * P_PPWAIT is set; we will wakeup the parent below.
            */
           PROC_LOCK(p);
           rv = p->p_xstat;        /* Event handler could change exit status */
           stopprofclock(p);
           p->p_flag &= ~(P_TRACED | P_PPWAIT);
   
           /*
            * Stop the real interval timer.  If the handler is currently
            * executing, prevent it from rearming itself and let it finish.
            */
           if (timevalisset(&p->p_realtimer.it_value) &&
               callout_stop(&p->p_itcallout) == 0) {
                   timevalclear(&p->p_realtimer.it_interval);
                   msleep(&p->p_itcallout, &p->p_mtx, PWAIT, "ritwait", 0);
                   KASSERT(!timevalisset(&p->p_realtimer.it_value),
                       ("realtime timer is still armed"));
           }
           PROC_UNLOCK(p);
   
           /*
            * Reset any sigio structures pointing to us as a result of
            * F_SETOWN with our pid.
            */
           funsetownlst(&p->p_sigiolst);
   
           /*
            * If this process has an nlminfo data area (for lockd), release it
            */
           if (nlminfo_release_p != NULL && p->p_nlminfo != NULL)
                   (*nlminfo_release_p)(p);
   
           /*
            * Close open files and release open-file table.
            * This may block!
            */
           fdfree(td);
   
           /*
            * If this thread tickled GEOM, we need to wait for the giggling to
            * stop before we return to userland
            */
           if (td->td_pflags & TDP_GEOM)
                   g_waitidle();
   
           /*
            * Remove ourself from our leader's peer list and wake our leader.
            */
           mtx_lock(&ppeers_lock);
           if (p->p_leader->p_peers) {
                   q = p->p_leader;
                   while (q->p_peers != p)
                           q = q->p_peers;
                   q->p_peers = p->p_peers;
                   wakeup(p->p_leader);
           }
           mtx_unlock(&ppeers_lock);
   
           vmspace_exit(td);
   
           sx_xlock(&proctree_lock);
           if (SESS_LEADER(p)) {
                   struct session *sp = p->p_session;
                   struct tty *tp;
   
                   /*
                    * s_ttyp is not zero'd; we use this to indicate that
                    * the session once had a controlling terminal. (for
                    * logging and informational purposes)
                    */
                   SESS_LOCK(sp);
                   ttyvp = sp->s_ttyvp;
                   tp = sp->s_ttyp;
                   sp->s_ttyvp = NULL;
                   sp->s_ttydp = NULL;
                   sp->s_leader = NULL;
                   SESS_UNLOCK(sp);
   
                   /*
                    * Signal foreground pgrp and revoke access to
                    * controlling terminal if it has not been revoked
                    * already.
                    *
                    * Because the TTY may have been revoked in the mean
                    * time and could already have a new session associated
                    * with it, make sure we don't send a SIGHUP to a
                    * foreground process group that does not belong to this
                    * session.
                    */
   
                   if (tp != NULL) {
                           tty_lock(tp);
                           if (tp->t_session == sp)
                                   tty_signal_pgrp(tp, SIGHUP);
                           tty_unlock(tp);
                   }
   
                   if (ttyvp != NULL) {
                           sx_xunlock(&proctree_lock);
                           if (vn_lock(ttyvp, LK_EXCLUSIVE) == 0) {
                                   VOP_REVOKE(ttyvp, REVOKEALL);
                                   VOP_UNLOCK(ttyvp, 0);
                           }
                           sx_xlock(&proctree_lock);
                   }
           }
           fixjobc(p, p->p_pgrp, 0);
           sx_xunlock(&proctree_lock);
           (void)acct_process(td);
   
           /* Release the TTY now we've unlocked everything. */
           if (ttyvp != NULL)
                   vrele(ttyvp);
   #ifdef KTRACE
           ktrprocexit(td);
   #endif
           /*
            * Release reference to text vnode
            */
           if ((vtmp = p->p_textvp) != NULL) {
                   p->p_textvp = NULL;
                   locked = VFS_LOCK_GIANT(vtmp->v_mount);
                   vrele(vtmp);
                   VFS_UNLOCK_GIANT(locked);
           }
   
           /*
            * Release our limits structure.
            */
           PROC_LOCK(p);
           plim = p->p_limit;
           p->p_limit = NULL;
           PROC_UNLOCK(p);
           lim_free(plim);
   
           tidhash_remove(td);
   
           /*
            * Remove proc from allproc queue and pidhash chain.
            * Place onto zombproc.  Unlink from parent's child list.
            */
           sx_xlock(&allproc_lock);
           LIST_REMOVE(p, p_list);
           LIST_INSERT_HEAD(&zombproc, p, p_list);
           LIST_REMOVE(p, p_hash);
           sx_xunlock(&allproc_lock);
   
           /*
            * Call machine-dependent code to release any
            * machine-dependent resources other than the address space.
            * The address space is released by "vmspace_exitfree(p)" in
            * vm_waitproc().
            */
           cpu_exit(td);
   
           WITNESS_WARN(WARN_PANIC, NULL, "process (pid %d) exiting", p->p_pid);
   
           /*
            * Reparent all of our children to init.
            */
           sx_xlock(&proctree_lock);
           q = LIST_FIRST(&p->p_children);
           if (q != NULL)          /* only need this if any child is S_ZOMB */
                   wakeup(initproc);
           for (; q != NULL; q = nq) {
                   nq = LIST_NEXT(q, p_sibling);
                   PROC_LOCK(q);
                   proc_reparent(q, initproc);
                   q->p_sigparent = SIGCHLD;
                   /*
                    * Traced processes are killed
                    * since their existence means someone is screwing up.
                    */
                   if (q->p_flag & P_TRACED) {
                           struct thread *temp;
   
                           /*
                            * Since q was found on our children list, the
                            * proc_reparent() call moved q to the orphan
                            * list due to present P_TRACED flag. Clear
                            * orphan link for q now while q is locked.
                            */
                           clear_orphan(q);
                           q->p_flag &= ~(P_TRACED | P_STOPPED_TRACE);
                           FOREACH_THREAD_IN_PROC(q, temp)
                                   temp->td_dbgflags &= ~TDB_SUSPEND;
                           kern_psignal(q, SIGKILL);
                   }
                   PROC_UNLOCK(q);
           }
   
           /*
            * Also get rid of our orphans.
            */
           while ((q = LIST_FIRST(&p->p_orphans)) != NULL) {
                   PROC_LOCK(q);
                   clear_orphan(q);
                   PROC_UNLOCK(q);
           }
   
           /* Save exit status. */
           PROC_LOCK(p);
           p->p_xthread = td;
   
           /* Tell the prison that we are gone. */
           prison_proc_free(p->p_ucred->cr_prison);
   
   #ifdef KDTRACE_HOOKS
           /*
            * Tell the DTrace fasttrap provider about the exit if it
            * has declared an interest.
            */
           if (dtrace_fasttrap_exit)
                   dtrace_fasttrap_exit(p);
   #endif
   
           /*
            * Notify interested parties of our demise.
            */
           KNOTE_LOCKED(&p->p_klist, NOTE_EXIT);
   
   #ifdef KDTRACE_HOOKS
           int reason = CLD_EXITED;
           if (WCOREDUMP(rv))
                   reason = CLD_DUMPED;
           else if (WIFSIGNALED(rv))
                   reason = CLD_KILLED;
           SDT_PROBE(proc, kernel, , exit, reason, 0, 0, 0, 0);
   #endif
   
           /*
            * Just delete all entries in the p_klist. At this point we won't
            * report any more events, and there are nasty race conditions that
            * can beat us if we don't.
            */
           knlist_clear(&p->p_klist, 1);
   
           /*
            * If this is a process with a descriptor, we may not need to deliver
            * a signal to the parent.  proctree_lock is held over
            * procdesc_exit() to serialize concurrent calls to close() and
            * exit().
            */
   #ifdef PROCDESC
           if (p->p_procdesc == NULL || procdesc_exit(p)) {
   #endif
                   /*
                    * Notify parent that we're gone.  If parent has the
                    * PS_NOCLDWAIT flag set, or if the handler is set to SIG_IGN,
                    * notify process 1 instead (and hope it will handle this
                    * situation).
                    */
                   PROC_LOCK(p->p_pptr);
                   mtx_lock(&p->p_pptr->p_sigacts->ps_mtx);
                   if (p->p_pptr->p_sigacts->ps_flag &
                       (PS_NOCLDWAIT | PS_CLDSIGIGN)) {
                           struct proc *pp;
   
                           mtx_unlock(&p->p_pptr->p_sigacts->ps_mtx);
                           pp = p->p_pptr;
                           PROC_UNLOCK(pp);
                           proc_reparent(p, initproc);
                           p->p_sigparent = SIGCHLD;
                           PROC_LOCK(p->p_pptr);
   
                           /*
                            * Notify parent, so in case he was wait(2)ing or
                            * executing waitpid(2) with our pid, he will
                            * continue.
                            */
                           wakeup(pp);
                   } else
                           mtx_unlock(&p->p_pptr->p_sigacts->ps_mtx);
   
                   if (p->p_pptr == initproc)
                           kern_psignal(p->p_pptr, SIGCHLD);
                   else if (p->p_sigparent != 0) {
                           if (p->p_sigparent == SIGCHLD)
                                   childproc_exited(p);
                           else    /* LINUX thread */
                                   kern_psignal(p->p_pptr, p->p_sigparent);
                   }
   #ifdef PROCDESC
           } else
                   PROC_LOCK(p->p_pptr);
   #endif
           sx_xunlock(&proctree_lock);
   
           /*
            * The state PRS_ZOMBIE prevents other proesses from sending
            * signal to the process, to avoid memory leak, we free memory
            * for signal queue at the time when the state is set.
            */
           sigqueue_flush(&p->p_sigqueue);
           sigqueue_flush(&td->td_sigqueue);
   
           /*
            * We have to wait until after acquiring all locks before
            * changing p_state.  We need to avoid all possible context
            * switches (including ones from blocking on a mutex) while
            * marked as a zombie.  We also have to set the zombie state
            * before we release the parent process' proc lock to avoid
            * a lost wakeup.  So, we first call wakeup, then we grab the
            * sched lock, update the state, and release the parent process'
            * proc lock.
            */
           wakeup(p->p_pptr);
           cv_broadcast(&p->p_pwait);
           sched_exit(p->p_pptr, td);
           PROC_SLOCK(p);
           p->p_state = PRS_ZOMBIE;
           PROC_UNLOCK(p->p_pptr);
   
           /*
            * Hopefully no one will try to deliver a signal to the process this
            * late in the game.
            */
           knlist_destroy(&p->p_klist);
   
           /*
            * Save our children's rusage information in our exit rusage.
            */
           ruadd(&p->p_ru, &p->p_rux, &p->p_stats->p_cru, &p->p_crux);
   
           /*
            * Make sure the scheduler takes this thread out of its tables etc.
            * This will also release this thread's reference to the ucred.
            * Other thread parts to release include pcb bits and such.
            */
           thread_exit();
   }
   
   
   #ifndef _SYS_SYSPROTO_H_
   struct abort2_args {
           char *why;
           int nargs;
           void **args;
   };
   #endif
   
   int
   sys_abort2(struct thread *td, struct abort2_args *uap)
   {
           struct proc *p = td->td_proc;
           struct sbuf *sb;
           void *uargs[16];
           int error, i, sig;
   
           /*
            * Do it right now so we can log either proper call of abort2(), or
            * note, that invalid argument was passed. 512 is big enough to
            * handle 16 arguments' descriptions with additional comments.
            */
           sb = sbuf_new(NULL, NULL, 512, SBUF_FIXEDLEN);
           sbuf_clear(sb);
           sbuf_printf(sb, "%s(pid %d uid %d) aborted: ",
               p->p_comm, p->p_pid, td->td_ucred->cr_uid);
           /* 
            * Since we can't return from abort2(), send SIGKILL in cases, where
            * abort2() was called improperly
            */
           sig = SIGKILL;
           /* Prevent from DoSes from user-space. */
           if (uap->nargs < 0 || uap->nargs > 16)
                   goto out;
           if (uap->nargs > 0) {
                   if (uap->args == NULL)
                           goto out;
                   error = copyin(uap->args, uargs, uap->nargs * sizeof(void *));
                   if (error != 0)
                           goto out;
           }
           /*
            * Limit size of 'reason' string to 128. Will fit even when
            * maximal number of arguments was chosen to be logged.
            */
           if (uap->why != NULL) {
                   error = sbuf_copyin(sb, uap->why, 128);
                   if (error < 0)
                           goto out;
           } else {
                   sbuf_printf(sb, "(null)");
           }
           if (uap->nargs > 0) {
                   sbuf_printf(sb, "(");
                   for (i = 0;i < uap->nargs; i++)
                           sbuf_printf(sb, "%s%p", i == 0 ? "" : ", ", uargs[i]);
                   sbuf_printf(sb, ")");
           }
           /*
            * Final stage: arguments were proper, string has been
            * successfully copied from userspace, and copying pointers
            * from user-space succeed.
            */
           sig = SIGABRT;
   out:
           if (sig == SIGKILL) {
                   sbuf_trim(sb);
                   sbuf_printf(sb, " (Reason text inaccessible)");
           }
           sbuf_cat(sb, "\n");
           sbuf_finish(sb);
           log(LOG_INFO, "%s", sbuf_data(sb));
           sbuf_delete(sb);
           exit1(td, W_EXITCODE(0, sig));
           return (0);
   }
   
   
   #ifdef COMPAT_43
   /*
    * The dirty work is handled by kern_wait().
    */
   int
   owait(struct thread *td, struct owait_args *uap __unused)
   {
           int error, status;
   
           error = kern_wait(td, WAIT_ANY, &status, 0, NULL);
           if (error == 0)
                   td->td_retval[1] = status;
           return (error);
   }
   #endif /* COMPAT_43 */
   
   /*
    * The dirty work is handled by kern_wait().
    */
   int
   sys_wait4(struct thread *td, struct wait_args *uap)
   {
           struct rusage ru, *rup;
           int error, status;
   
           if (uap->rusage != NULL)
                   rup = &ru;
           else
                   rup = NULL;
           error = kern_wait(td, uap->pid, &status, uap->options, rup);
           if (uap->status != NULL && error == 0)
                   error = copyout(&status, uap->status, sizeof(status));
           if (uap->rusage != NULL && error == 0)
                   error = copyout(&ru, uap->rusage, sizeof(struct rusage));
           return (error);
   }
   
   /*
    * Reap the remains of a zombie process and optionally return status and
    * rusage.  Asserts and will release both the proctree_lock and the process
    * lock as part of its work.
    */
   void
   proc_reap(struct thread *td, struct proc *p, int *status, int options,
       struct rusage *rusage)
   {
           struct proc *q, *t;
   
           sx_assert(&proctree_lock, SA_XLOCKED);
           PROC_LOCK_ASSERT(p, MA_OWNED);
           PROC_SLOCK_ASSERT(p, MA_OWNED);
           KASSERT(p->p_state == PRS_ZOMBIE, ("proc_reap: !PRS_ZOMBIE"));
   
           q = td->td_proc;
           if (rusage) {
                   *rusage = p->p_ru;
                   calcru(p, &rusage->ru_utime, &rusage->ru_stime);
           }
           PROC_SUNLOCK(p);
           td->td_retval[0] = p->p_pid;
           if (status)
                   *status = p->p_xstat;   /* convert to int */
           if (options & WNOWAIT) {
                   /*
                    *  Only poll, returning the status.  Caller does not wish to
                    * release the proc struct just yet.
                    */
                   PROC_UNLOCK(p);
                   sx_xunlock(&proctree_lock);
                   return;
           }
   
           PROC_LOCK(q);
           sigqueue_take(p->p_ksi);
           PROC_UNLOCK(q);
           PROC_UNLOCK(p);
   
           /*
            * If we got the child via a ptrace 'attach', we need to give it back
            * to the old parent.
            */
           if (p->p_oppid && (t = pfind(p->p_oppid)) != NULL) {
                   PROC_LOCK(p);
                   proc_reparent(p, t);
                   p->p_oppid = 0;
                   PROC_UNLOCK(p);
                   pksignal(t, SIGCHLD, p->p_ksi);
                   wakeup(t);
                   cv_broadcast(&p->p_pwait);
                   PROC_UNLOCK(t);
                   sx_xunlock(&proctree_lock);
                   return;
           }
   
           /*
            * Remove other references to this process to ensure we have an
            * exclusive reference.
            */
           sx_xlock(&allproc_lock);
           LIST_REMOVE(p, p_list); /* off zombproc */
           sx_xunlock(&allproc_lock);
           LIST_REMOVE(p, p_sibling);
           PROC_LOCK(p);
           clear_orphan(p);
           PROC_UNLOCK(p);
           leavepgrp(p);
   #ifdef PROCDESC
           if (p->p_procdesc != NULL)
                   procdesc_reap(p);
   #endif
           sx_xunlock(&proctree_lock);
   
           /*
            * As a side effect of this lock, we know that all other writes to
            * this proc are visible now, so no more locking is needed for p.
            */
           PROC_LOCK(p);
           p->p_xstat = 0;         /* XXX: why? */
           PROC_UNLOCK(p);
           PROC_LOCK(q);
           ruadd(&q->p_stats->p_cru, &q->p_crux, &p->p_ru, &p->p_rux);
           PROC_UNLOCK(q);
   
           /*
            * Decrement the count of procs running with this uid.
            */
           (void)chgproccnt(p->p_ucred->cr_ruidinfo, -1, 0);
   
           /*
            * Destroy resource accounting information associated with the process.
            */
   #ifdef RACCT
           PROC_LOCK(p);
           racct_sub(p, RACCT_NPROC, 1);
           PROC_UNLOCK(p);
   #endif
           racct_proc_exit(p);
   
           /*
            * Free credentials, arguments, and sigacts.
            */
           crfree(p->p_ucred);
           p->p_ucred = NULL;
           pargs_drop(p->p_args);
           p->p_args = NULL;
           sigacts_free(p->p_sigacts);
           p->p_sigacts = NULL;
   
           /*
            * Do any thread-system specific cleanups.
            */
           thread_wait(p);
   
           /*
            * Give vm and machine-dependent layer a chance to free anything that
            * cpu_exit couldn't release while still running in process context.
            */
           vm_waitproc(p);
   #ifdef MAC
           mac_proc_destroy(p);
   #endif
           KASSERT(FIRST_THREAD_IN_PROC(p),
               ("proc_reap: no residual thread!"));
           uma_zfree(proc_zone, p);
           sx_xlock(&allproc_lock);
           nprocs--;
           sx_xunlock(&allproc_lock);
   }
   
   static int
   proc_to_reap(struct thread *td, struct proc *p, pid_t pid, int *status,
       int options, struct rusage *rusage)
   {
           struct proc *q;
   
           sx_assert(&proctree_lock, SA_XLOCKED);
   
           q = td->td_proc;
           PROC_LOCK(p);
           if (pid != WAIT_ANY && p->p_pid != pid && p->p_pgid != -pid) {
                   PROC_UNLOCK(p);
                   return (0);
           }
           if (p_canwait(td, p)) {
                   PROC_UNLOCK(p);
                   return (0);
           }
   
           /*
            * This special case handles a kthread spawned by linux_clone
            * (see linux_misc.c).  The linux_wait4 and linux_waitpid
            * functions need to be able to distinguish between waiting
            * on a process and waiting on a thread.  It is a thread if
            * p_sigparent is not SIGCHLD, and the WLINUXCLONE option
            * signifies we want to wait for threads and not processes.
            */
           if ((p->p_sigparent != SIGCHLD) ^
               ((options & WLINUXCLONE) != 0)) {
                   PROC_UNLOCK(p);
                   return (0);
           }
   
           PROC_SLOCK(p);
           if (p->p_state == PRS_ZOMBIE) {
                   proc_reap(td, p, status, options, rusage);
                   return (-1);
           }
           PROC_SUNLOCK(p);
           PROC_UNLOCK(p);
           return (1);
   }
   
   int
   kern_wait(struct thread *td, pid_t pid, int *status, int options,
       struct rusage *rusage)
   {
           struct proc *p, *q;
           int error, nfound, ret;
   
           AUDIT_ARG_PID(pid);
           AUDIT_ARG_VALUE(options);
   
           q = td->td_proc;
           if (pid == 0) {
                   PROC_LOCK(q);
                   pid = -q->p_pgid;
                   PROC_UNLOCK(q);
           }
           /* If we don't know the option, just return. */
           if (options & ~(WUNTRACED|WNOHANG|WCONTINUED|WNOWAIT|WLINUXCLONE))
                   return (EINVAL);
   loop:
           if (q->p_flag & P_STATCHILD) {
                   PROC_LOCK(q);
                   q->p_flag &= ~P_STATCHILD;
                   PROC_UNLOCK(q);
           }
           nfound = 0;
           sx_xlock(&proctree_lock);
           LIST_FOREACH(p, &q->p_children, p_sibling) {
                   ret = proc_to_reap(td, p, pid, status, options, rusage);
                   if (ret == 0)
                           continue;
                   else if (ret == 1)
                           nfound++;
                   else
                           return (0);
   
                   PROC_LOCK(p);
                   PROC_SLOCK(p);
                   if ((p->p_flag & P_STOPPED_SIG) &&
                       (p->p_suspcount == p->p_numthreads) &&
                       (p->p_flag & P_WAITED) == 0 &&
                       (p->p_flag & P_TRACED || options & WUNTRACED)) {
                           PROC_SUNLOCK(p);
                           p->p_flag |= P_WAITED;
                           sx_xunlock(&proctree_lock);
                           td->td_retval[0] = p->p_pid;
                           if (status)
                                   *status = W_STOPCODE(p->p_xstat);
   
                           PROC_LOCK(q);
                           sigqueue_take(p->p_ksi);
                           PROC_UNLOCK(q);
                           PROC_UNLOCK(p);
   
                           return (0);
                   }
                   PROC_SUNLOCK(p);
                   if (options & WCONTINUED && (p->p_flag & P_CONTINUED)) {
                           sx_xunlock(&proctree_lock);
                           td->td_retval[0] = p->p_pid;
                           p->p_flag &= ~P_CONTINUED;
   
                           PROC_LOCK(q);
                           sigqueue_take(p->p_ksi);
                           PROC_UNLOCK(q);
                           PROC_UNLOCK(p);
   
                           if (status)
                                   *status = SIGCONT;
                           return (0);
                   }
                   PROC_UNLOCK(p);
           }
   
           /*
            * Look in the orphans list too, to allow the parent to
            * collect it's child exit status even if child is being
            * debugged.
            *
            * Debugger detaches from the parent upon successful
            * switch-over from parent to child.  At this point due to
            * re-parenting the parent loses the child to debugger and a
            * wait4(2) call would report that it has no children to wait
            * for.  By maintaining a list of orphans we allow the parent
            * to successfully wait until the child becomes a zombie.
            */
           LIST_FOREACH(p, &q->p_orphans, p_orphan) {
                   ret = proc_to_reap(td, p, pid, status, options, rusage);
                   if (ret == 0)
                           continue;
                   else if (ret == 1)
                           nfound++;
                   else
                           return (0);
           }
           if (nfound == 0) {
                   sx_xunlock(&proctree_lock);
                   return (ECHILD);
           }
           if (options & WNOHANG) {
                   sx_xunlock(&proctree_lock);
                   td->td_retval[0] = 0;
                   return (0);
           }
           PROC_LOCK(q);
           sx_xunlock(&proctree_lock);
           if (q->p_flag & P_STATCHILD) {
                   q->p_flag &= ~P_STATCHILD;
                   error = 0;
           } else
                   error = msleep(q, &q->p_mtx, PWAIT | PCATCH, "wait", 0);
           PROC_UNLOCK(q);
           if (error)
                   return (error); 
           goto loop;
   }
   
   /*
    * Make process 'parent' the new parent of process 'child'.
    * Must be called with an exclusive hold of proctree lock.
    */
  void
  proc_reparent(struct proc *child, struct proc *parent)
  {
  
          sx_assert(&proctree_lock, SX_XLOCKED);
          PROC_LOCK_ASSERT(child, MA_OWNED);
          if (child->p_pptr == parent)
                  return;
  
          PROC_LOCK(child->p_pptr);
          sigqueue_take(child->p_ksi);
          PROC_UNLOCK(child->p_pptr);
          LIST_REMOVE(child, p_sibling);
          LIST_INSERT_HEAD(&parent->p_children, child, p_sibling);
  
          clear_orphan(child);
          if (child->p_flag & P_TRACED) {
                  LIST_INSERT_HEAD(&child->p_pptr->p_orphans, child, p_orphan);
                  child->p_flag |= P_ORPHAN;
          }
  
          child->p_pptr = parent;
  }

Cache object: a46cb2beb8bfd8f6b3c596ce96394b27