/* $NetBSD: kern_exit.c,v 1.130 2003/12/06 04:16:33 atatat Exp $ */ /*- * Copyright (c) 1998, 1999 The NetBSD Foundation, Inc. * All rights reserved. * * This code is derived from software contributed to The NetBSD Foundation * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility, * NASA Ames Research Center. * * 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. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the NetBSD * Foundation, Inc. and its contributors. * 4. Neither the name of The NetBSD Foundation 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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. */ /* * 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. * 3. 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 8.10 (Berkeley) 2/23/95 */ #include __KERNEL_RCSID(0, "$NetBSD: kern_exit.c,v 1.130 2003/12/06 04:16:33 atatat Exp $"); #include "opt_ktrace.h" #include "opt_perfctrs.h" #include "opt_systrace.h" #include "opt_sysv.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #if defined(PERFCTRS) #include #endif #include #include #include #include #include #include #include #include #include #include #include #include #include #define DEBUG_EXIT #ifdef DEBUG_EXIT int debug_exit = 0; #define DPRINTF(x) if (debug_exit) printf x #else #define DPRINTF(x) #endif static void lwp_exit_hook(struct lwp *, void *); static void exit_psignal(struct proc *, struct proc *); /* * Fill in the appropriate signal information, and kill the parent. */ static void exit_psignal(struct proc *p, struct proc *pp) { ksiginfo_t ksi; (void)memset(&ksi, 0, sizeof(ksi)); if ((ksi.ksi_signo = P_EXITSIG(p)) == SIGCHLD) { if (WIFSIGNALED(p->p_xstat)) { if (WCOREDUMP(p->p_xstat)) ksi.ksi_code = CLD_DUMPED; else ksi.ksi_code = CLD_KILLED; } else { ksi.ksi_code = CLD_EXITED; } } /* * we fill those in, even for non-SIGCHLD. */ ksi.ksi_pid = p->p_pid; ksi.ksi_uid = p->p_ucred->cr_uid; ksi.ksi_status = p->p_xstat; /* XXX: is this still valid? */ ksi.ksi_utime = p->p_ru->ru_utime.tv_sec; ksi.ksi_stime = p->p_ru->ru_stime.tv_sec; kpsignal(pp, &ksi, NULL); } /* * exit -- * Death of process. */ int sys_exit(struct lwp *l, void *v, register_t *retval) { struct sys_exit_args /* { syscallarg(int) rval; } */ *uap = v; /* Don't call exit1() multiple times in the same process.*/ if (l->l_proc->p_flag & P_WEXIT) lwp_exit(l); exit1(l, W_EXITCODE(SCARG(uap, rval), 0)); /* NOTREACHED */ return (0); } /* * 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 lwp *l, int rv) { struct proc *p, *q, *nq; int s, sa; p = l->l_proc; if (__predict_false(p == initproc)) panic("init died (signal %d, exit %d)", WTERMSIG(rv), WEXITSTATUS(rv)); p->p_flag |= P_WEXIT; if (p->p_flag & P_STOPEXIT) { int s; sigminusset(&contsigmask, &p->p_sigctx.ps_siglist); SCHED_LOCK(s); p->p_stat = SSTOP; l->l_stat = LSSTOP; p->p_nrlwps--; mi_switch(l, NULL); SCHED_ASSERT_UNLOCKED(); splx(s); } DPRINTF(("exit1: %d.%d exiting.\n", p->p_pid, l->l_lid)); /* * Disable scheduler activation upcalls. * We're trying to get out of here. */ sa = 0; if (p->p_sa != NULL) { l->l_flag &= ~L_SA; #if 0 p->p_flag &= ~P_SA; #endif sa = 1; } #ifdef PGINPROF vmsizmon(); #endif if (p->p_flag & P_PROFIL) stopprofclock(p); p->p_ru = pool_get(&rusage_pool, PR_WAITOK); /* * If parent is waiting for us to exit or exec, P_PPWAIT is set; we * wake up the parent early to avoid deadlock. */ if (p->p_flag & P_PPWAIT) { p->p_flag &= ~P_PPWAIT; wakeup(p->p_pptr); } sigfillset(&p->p_sigctx.ps_sigignore); sigemptyset(&p->p_sigctx.ps_siglist); p->p_sigctx.ps_sigcheck = 0; timers_free(p, TIMERS_ALL); if (sa || (p->p_nlwps > 1)) exit_lwps(l); #if defined(__HAVE_RAS) ras_purgeall(p); #endif /* * Close open files and release open-file table. * This may block! */ fdfree(p); cwdfree(p); doexithooks(p); if (SESS_LEADER(p)) { struct session *sp = p->p_session; struct tty *tp; if (sp->s_ttyvp) { /* * Controlling process. * Signal foreground pgrp, * drain controlling terminal * and revoke access to controlling terminal. */ tp = sp->s_ttyp; TTY_LOCK(tp); if (tp->t_session == sp) { if (tp->t_pgrp) pgsignal(tp->t_pgrp, SIGHUP, 1); /* we can't guarantee the revoke will do this */ tp->t_pgrp = NULL; tp->t_session = NULL; TTY_UNLOCK(tp); SESSRELE(sp); (void) ttywait(tp); /* * The tty could have been revoked * if we blocked. */ if (sp->s_ttyvp) VOP_REVOKE(sp->s_ttyvp, REVOKEALL); } else TTY_UNLOCK(tp); if (sp->s_ttyvp) vrele(sp->s_ttyvp); sp->s_ttyvp = NULL; /* * s_ttyp is not zero'd; we use this to indicate * that the session once had a controlling terminal. * (for logging and informational purposes) */ } sp->s_leader = NULL; } fixjobc(p, p->p_pgrp, 0); (void)acct_process(p); #ifdef KTRACE /* * release trace file */ ktrderef(p); #endif #ifdef SYSTRACE systrace_sys_exit(p); #endif /* * If emulation has process exit hook, call it now. */ if (p->p_emul->e_proc_exit) (*p->p_emul->e_proc_exit)(p); /* * Reset p_opptr pointer of all former children which got * traced by another process and were reparented. We reset * it to NULL here; the trace detach code then reparents * the child to initproc. We only check allproc list, since * eventual former children on zombproc list won't reference * p_opptr anymore. */ s = proclist_lock_write(); if (p->p_flag & P_CHTRACED) { LIST_FOREACH(q, &allproc, p_list) { if (q->p_opptr == p) q->p_opptr = NULL; } } /* * Give orphaned children to init(8). */ q = LIST_FIRST(&p->p_children); if (q) /* only need this if any child is S_ZOMB */ wakeup(initproc); for (; q != 0; q = nq) { nq = LIST_NEXT(q, p_sibling); /* * Traced processes are killed since their existence * means someone is screwing up. Since we reset the * trace flags, the logic in sys_wait4() would not be * triggered to reparent the process to its * original parent, so we must do this here. */ if (q->p_flag & P_TRACED) { if (q->p_opptr != q->p_pptr) { struct proc *t = q->p_opptr; proc_reparent(q, t ? t : initproc); q->p_opptr = NULL; } else proc_reparent(q, initproc); q->p_flag &= ~(P_TRACED|P_WAITED|P_FSTRACE); psignal(q, SIGKILL); } else { proc_reparent(q, initproc); } } proclist_unlock_write(s); /* * Save exit status and final rusage info, adding in child rusage * info and self times. * In order to pick up the time for the current execution, we must * do this before unlinking the lwp from l_list. */ p->p_xstat = rv; *p->p_ru = p->p_stats->p_ru; calcru(p, &p->p_ru->ru_utime, &p->p_ru->ru_stime, NULL); ruadd(p->p_ru, &p->p_stats->p_cru); /* * NOTE: WE ARE NO LONGER ALLOWED TO SLEEP! */ /* * Move proc from allproc to zombproc, but do not yet * wake up the reaper. We will put the proc on the * deadproc list later (using the p_dead member), and * wake up the reaper when we do. * Changing the state to SDEAD stops it being found by pfind(). */ s = proclist_lock_write(); p->p_stat = SDEAD; p->p_nrlwps--; l->l_stat = LSDEAD; LIST_REMOVE(p, p_list); LIST_INSERT_HEAD(&zombproc, p, p_list); LIST_REMOVE(l, l_list); l->l_flag |= L_DETACHED; proclist_unlock_write(s); /* * Notify interested parties of our demise. */ KNOTE(&p->p_klist, NOTE_EXIT); #if PERFCTRS /* * Save final PMC information in parent process & clean up. */ if (PMC_ENABLED(p)) { pmc_save_context(p); pmc_accumulate(p->p_pptr, p); pmc_process_exit(p); } #endif /* * Notify parent that we're gone. If parent has the P_NOCLDWAIT * flag set, notify init instead (and hope it will handle * this situation). */ if (p->p_pptr->p_flag & P_NOCLDWAIT) { struct proc *pp = p->p_pptr; proc_reparent(p, initproc); /* * If this was the last child of our parent, notify * parent, so in case he was wait(2)ing, he will * continue. */ if (LIST_FIRST(&pp->p_children) == NULL) wakeup(pp); } /* * Release the process's signal state. */ sigactsfree(p); /* * Clear curlwp after we've done all operations * that could block, and before tearing down the rest * of the process state that might be used from clock, etc. * Also, can't clear curlwp while we're still runnable, * as we're not on a run queue (we are current, just not * a proper proc any longer!). * * Other substructures are freed from wait(). */ curlwp = NULL; limfree(p->p_limit); pstatsfree(p->p_stats); p->p_limit = NULL; /* This process no longer needs to hold the kernel lock. */ KERNEL_PROC_UNLOCK(l); /* * Finally, call machine-dependent code to switch to a new * context (possibly the idle context). Once we are no longer * using the dead process's vmspace and stack, exit2() will be * called to schedule those resources to be released by the * reaper thread. * * Note that cpu_exit() will end with a call equivalent to * cpu_switch(), finishing our execution (pun intended). */ cpu_exit(l, 1); } void exit_lwps(struct lwp *l) { struct proc *p; struct lwp *l2; int s, error; lwpid_t waited; p = l->l_proc; /* XXX SMP * This would be the right place to IPI any LWPs running on * other processors so that they can notice the userret exit hook. */ p->p_userret = lwp_exit_hook; p->p_userret_arg = NULL; /* * Make SA-cached LWPs normal process runnable LWPs so that * they'll also self-destruct. */ if (p->p_sa && p->p_sa->sa_ncached > 0) { DPRINTF(("exit_lwps: Making cached LWPs of %d runnable: ", p->p_pid)); SCHED_LOCK(s); while ((l2 = sa_getcachelwp(p)) != 0) { l2->l_priority = l2->l_usrpri; setrunnable(l2); DPRINTF(("%d ", l2->l_lid)); } DPRINTF(("\n")); SCHED_UNLOCK(s); } /* * Interrupt LWPs in interruptable sleep, unsuspend suspended * LWPs, make detached LWPs undetached (so we can wait for * them) and then wait for everyone else to finish. */ LIST_FOREACH(l2, &p->p_lwps, l_sibling) { l2->l_flag &= ~(L_DETACHED|L_SA); if (l2->l_wchan == &l2->l_upcallstack) wakeup(&l2->l_upcallstack); if ((l2->l_stat == LSSLEEP && (l2->l_flag & L_SINTR)) || l2->l_stat == LSSUSPENDED || l2->l_stat == LSSTOP) { SCHED_LOCK(s); setrunnable(l2); SCHED_UNLOCK(s); DPRINTF(("exit_lwps: Made %d.%d runnable\n", p->p_pid, l2->l_lid)); } } while (p->p_nlwps > 1) { DPRINTF(("exit_lwps: waiting for %d LWPs (%d runnable, %d zombies)\n", p->p_nlwps, p->p_nrlwps, p->p_nzlwps)); error = lwp_wait1(l, 0, &waited, LWPWAIT_EXITCONTROL); if (error) panic("exit_lwps: lwp_wait1 failed with error %d\n", error); DPRINTF(("exit_lwps: Got LWP %d from lwp_wait1()\n", waited)); } p->p_userret = NULL; } /* Wrapper function for use in p_userret */ static void lwp_exit_hook(struct lwp *l, void *arg) { KERNEL_PROC_LOCK(l); lwp_exit(l); } /* * We are called from cpu_exit() once it is safe to schedule the * dead process's resources to be freed (i.e., once we've switched to * the idle PCB for the current CPU). * * NOTE: One must be careful with locking in this routine. It's * called from a critical section in machine-dependent code, so * we should refrain from changing any interrupt state. * * We lock the deadproc list (a spin lock), place the proc on that * list (using the p_dead member), and wake up the reaper. */ void exit2(struct lwp *l) { struct proc *p = l->l_proc; simple_lock(&deadproc_slock); SLIST_INSERT_HEAD(&deadprocs, p, p_dead); simple_unlock(&deadproc_slock); /* lwp_exit2() will wake up deadproc for us. */ lwp_exit2(l); } /* * Process reaper. This is run by a kernel thread to free the resources * of a dead process. Once the resources are free, the process becomes * a zombie, and the parent is allowed to read the undead's status. */ void reaper(void *arg) { struct proc *p, *parent; struct lwp *l; KERNEL_PROC_UNLOCK(curlwp); for (;;) { simple_lock(&deadproc_slock); p = SLIST_FIRST(&deadprocs); l = LIST_FIRST(&deadlwp); if (p == NULL && l == NULL) { /* No work for us; go to sleep until someone exits. */ (void) ltsleep(&deadprocs, PVM|PNORELOCK, "reaper", 0, &deadproc_slock); continue; } if (l != NULL ) { p = l->l_proc; /* Remove lwp from the deadlwp list. */ LIST_REMOVE(l, l_list); simple_unlock(&deadproc_slock); KERNEL_PROC_LOCK(curlwp); /* * Give machine-dependent code a chance to free any * resources it couldn't free while still running on * that process's context. This must be done before * uvm_lwp_exit(), in case these resources are in the * PCB. */ cpu_wait(l); /* * Free the VM resources we're still holding on to. */ uvm_lwp_exit(l); l->l_stat = LSZOMB; if (l->l_flag & L_DETACHED) { /* Nobody waits for detached LWPs. */ LIST_REMOVE(l, l_sibling); p->p_nlwps--; pool_put(&lwp_pool, l); } else { p->p_nzlwps++; wakeup(&p->p_nlwps); } /* XXXNJW where should this be with respect to * the wakeup() above? */ KERNEL_PROC_UNLOCK(curlwp); } else { /* Remove proc from the deadproc list. */ SLIST_REMOVE_HEAD(&deadprocs, p_dead); simple_unlock(&deadproc_slock); KERNEL_PROC_LOCK(curlwp); /* * Free the VM resources we're still holding on to. * We must do this from a valid thread because doing * so may block. */ uvm_proc_exit(p); /* Process is now a true zombie. */ p->p_stat = SZOMB; parent = p->p_pptr; parent->p_nstopchild++; if (LIST_FIRST(&parent->p_children) != p) { /* Put child where it can be found quickly */ LIST_REMOVE(p, p_sibling); LIST_INSERT_HEAD(&parent->p_children, p, p_sibling); } /* Wake up the parent so it can get exit status. */ if ((p->p_flag & P_FSTRACE) == 0 && p->p_exitsig != 0) exit_psignal(p, p->p_pptr); KERNEL_PROC_UNLOCK(curlwp); wakeup(p->p_pptr); } } } int sys_wait4(struct lwp *l, void *v, register_t *retval) { struct sys_wait4_args /* { syscallarg(int) pid; syscallarg(int *) status; syscallarg(int) options; syscallarg(struct rusage *) rusage; } */ *uap = v; struct proc *child, *parent; int status, error; parent = l->l_proc; if (SCARG(uap, pid) == 0) SCARG(uap, pid) = -parent->p_pgid; if (SCARG(uap, options) & ~(WUNTRACED|WNOHANG|WALTSIG|WALLSIG)) return (EINVAL); error = find_stopped_child(parent, SCARG(uap,pid), SCARG(uap,options), &child); if (error != 0) return error; if (child == NULL) { *retval = 0; return 0; } retval[0] = child->p_pid; if (child->p_stat == SZOMB) { if (SCARG(uap, status)) { status = child->p_xstat; /* convert to int */ error = copyout(&status, SCARG(uap, status), sizeof(status)); if (error) return (error); } if (SCARG(uap, rusage)) { error = copyout(child->p_ru, SCARG(uap, rusage), sizeof(struct rusage)); if (error) return (error); } proc_free(child); return 0; } /* child state must be SSTOP */ if (SCARG(uap, status)) { status = W_STOPCODE(child->p_xstat); return copyout(&status, SCARG(uap, status), sizeof(status)); } return 0; } /* * Scan list of child processes for a child process that has stopped or * exited. Used by sys_wait4 and 'compat' equivalents. */ int find_stopped_child(struct proc *parent, pid_t pid, int options, struct proc **child_p) { struct proc *child; int error; for (;;) { proclist_lock_read(); error = ECHILD; LIST_FOREACH(child, &parent->p_children, p_sibling) { if (pid >= 0) { if (child->p_pid != pid) { child = p_find(pid, PFIND_ZOMBIE | PFIND_LOCKED); if (child == NULL || child->p_pptr != parent) { child = NULL; break; } } } else if (pid != WAIT_ANY && child->p_pgid != -pid) /* child not in correct pgrp */ continue; /* * Wait for processes with p_exitsig != SIGCHLD * processes only if WALTSIG is set; wait for * processes with p_exitsig == SIGCHLD only * if WALTSIG is clear. */ if (((options & WALLSIG) == 0) && (options & WALTSIG ? child->p_exitsig == SIGCHLD : P_EXITSIG(child) != SIGCHLD)){ if (child->p_pid == pid) { child = NULL; break; } continue; } error = 0; if (child->p_stat == SZOMB && !(options & WNOZOMBIE)) break; if (child->p_stat == SSTOP && (child->p_flag & P_WAITED) == 0 && (child->p_flag & P_TRACED || options & WUNTRACED)) { if ((options & WNOWAIT) == 0) { child->p_flag |= P_WAITED; parent->p_nstopchild--; } break; } if (parent->p_nstopchild == 0 || child->p_pid == pid) { child = NULL; break; } } proclist_unlock_read(); if (child != NULL || error != 0 || options & WNOHANG) { *child_p = child; return error; } error = tsleep(parent, PWAIT | PCATCH, "wait", 0); if (error != 0) return error; } } /* * Free a process after parent has taken all the state info. */ void proc_free(struct proc *p) { struct proc *parent = p->p_pptr; int s; /* * If we got the child via ptrace(2) or procfs, and * the parent is different (meaning the process was * attached, rather than run as a child), then we need * to give it back to the old parent, and send the * parent the exit signal. The rest of the cleanup * will be done when the old parent waits on the child. */ if ((p->p_flag & P_TRACED) && p->p_opptr != parent){ parent = p->p_opptr; if (parent == NULL) parent = initproc; proc_reparent(p, parent); p->p_opptr = NULL; p->p_flag &= ~(P_TRACED|P_WAITED|P_FSTRACE); if (p->p_exitsig != 0) exit_psignal(p, parent); wakeup(parent); return; } scheduler_wait_hook(parent, p); p->p_xstat = 0; ruadd(&parent->p_stats->p_cru, p->p_ru); /* * At this point we are going to start freeing the final resources. * If anyone tries to access the proc structure after here they * will get a shock - bits are missing. * Attempt to make it hard! */ p->p_stat = SIDL; /* not even a zombie any more */ pool_put(&rusage_pool, p->p_ru); /* * Finally finished with old proc entry. * Unlink it from its process group and free it. */ leavepgrp(p); s = proclist_lock_write(); LIST_REMOVE(p, p_list); /* off zombproc */ p->p_pptr->p_nstopchild--; LIST_REMOVE(p, p_sibling); proclist_unlock_write(s); /* * Decrement the count of procs running with this uid. */ (void)chgproccnt(p->p_cred->p_ruid, -1); /* * Free up credentials. */ if (--p->p_cred->p_refcnt == 0) { crfree(p->p_cred->pc_ucred); pool_put(&pcred_pool, p->p_cred); } /* * Release reference to text vnode */ if (p->p_textvp) vrele(p->p_textvp); /* Release any SA state. */ if (p->p_sa) sa_release(p); /* Free proc structure and let pid be reallocated */ proc_free_mem(p); } /* * make process 'parent' the new parent of process 'child'. * * Must be called with proclist_lock_write() held. */ void proc_reparent(struct proc *child, struct proc *parent) { if (child->p_pptr == parent) return; if (child->p_stat == SZOMB || (child->p_stat == SSTOP && !(child->p_flag & P_WAITED))) { child->p_pptr->p_nstopchild--; parent->p_nstopchild++; } if (parent == initproc) child->p_exitsig = SIGCHLD; LIST_REMOVE(child, p_sibling); LIST_INSERT_HEAD(&parent->p_children, child, p_sibling); child->p_pptr = parent; }