1/*
   2 *  linux/kernel/exit.c
   3 *
   4 *  Copyright (C) 1991, 1992  Linus Torvalds
   5 */
   6
   7#include <linux/mm.h>
   8#include <linux/slab.h>
 
 
 
 
 
 
   9#include <linux/interrupt.h>
  10#include <linux/module.h>
  11#include <linux/capability.h>
  12#include <linux/completion.h>
  13#include <linux/personality.h>
  14#include <linux/tty.h>
  15#include <linux/iocontext.h>
  16#include <linux/key.h>
  17#include <linux/security.h>
  18#include <linux/cpu.h>
  19#include <linux/acct.h>
  20#include <linux/tsacct_kern.h>
  21#include <linux/file.h>
  22#include <linux/fdtable.h>
  23#include <linux/freezer.h>
  24#include <linux/binfmts.h>
  25#include <linux/nsproxy.h>
  26#include <linux/pid_namespace.h>
  27#include <linux/ptrace.h>
  28#include <linux/profile.h>
  29#include <linux/mount.h>
  30#include <linux/proc_fs.h>
  31#include <linux/kthread.h>
  32#include <linux/mempolicy.h>
  33#include <linux/taskstats_kern.h>
  34#include <linux/delayacct.h>
  35#include <linux/cgroup.h>
  36#include <linux/syscalls.h>
  37#include <linux/signal.h>
  38#include <linux/posix-timers.h>
  39#include <linux/cn_proc.h>
  40#include <linux/mutex.h>
  41#include <linux/futex.h>
  42#include <linux/pipe_fs_i.h>
  43#include <linux/audit.h> /* for audit_free() */
  44#include <linux/resource.h>
  45#include <linux/blkdev.h>
  46#include <linux/task_io_accounting_ops.h>
  47#include <linux/tracehook.h>
 
  48#include <linux/fs_struct.h>
  49#include <linux/init_task.h>
  50#include <linux/perf_event.h>
  51#include <trace/events/sched.h>
  52#include <linux/hw_breakpoint.h>
  53#include <linux/oom.h>
  54#include <linux/writeback.h>
  55#include <linux/shm.h>
 
 
 
 
 
 
 
 
 
 
 
 
 
  56
  57#include <asm/uaccess.h>
  58#include <asm/unistd.h>
  59#include <asm/pgtable.h>
  60#include <asm/mmu_context.h>
  61
  62static void exit_mm(struct task_struct * tsk);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  63
  64static void __unhash_process(struct task_struct *p, bool group_dead)
  65{
  66	nr_threads--;
  67	detach_pid(p, PIDTYPE_PID);
  68	if (group_dead) {
 
  69		detach_pid(p, PIDTYPE_PGID);
  70		detach_pid(p, PIDTYPE_SID);
  71
  72		list_del_rcu(&p->tasks);
  73		list_del_init(&p->sibling);
  74		__this_cpu_dec(process_counts);
  75	}
  76	list_del_rcu(&p->thread_group);
  77	list_del_rcu(&p->thread_node);
  78}
  79
  80/*
  81 * This function expects the tasklist_lock write-locked.
  82 */
  83static void __exit_signal(struct task_struct *tsk)
  84{
  85	struct signal_struct *sig = tsk->signal;
  86	bool group_dead = thread_group_leader(tsk);
  87	struct sighand_struct *sighand;
  88	struct tty_struct *uninitialized_var(tty);
  89	cputime_t utime, stime;
  90
  91	sighand = rcu_dereference_check(tsk->sighand,
  92					lockdep_tasklist_lock_is_held());
  93	spin_lock(&sighand->siglock);
  94
 
  95	posix_cpu_timers_exit(tsk);
  96	if (group_dead) {
  97		posix_cpu_timers_exit_group(tsk);
 
 
 
  98		tty = sig->tty;
  99		sig->tty = NULL;
 100	} else {
 101		/*
 102		 * This can only happen if the caller is de_thread().
 103		 * FIXME: this is the temporary hack, we should teach
 104		 * posix-cpu-timers to handle this case correctly.
 105		 */
 106		if (unlikely(has_group_leader_pid(tsk)))
 107			posix_cpu_timers_exit_group(tsk);
 108
 109		/*
 110		 * If there is any task waiting for the group exit
 111		 * then notify it:
 112		 */
 113		if (sig->notify_count > 0 && !--sig->notify_count)
 114			wake_up_process(sig->group_exit_task);
 115
 116		if (tsk == sig->curr_target)
 117			sig->curr_target = next_thread(tsk);
 118		/*
 119		 * Accumulate here the counters for all threads but the
 120		 * group leader as they die, so they can be added into
 121		 * the process-wide totals when those are taken.
 122		 * The group leader stays around as a zombie as long
 123		 * as there are other threads.  When it gets reaped,
 124		 * the exit.c code will add its counts into these totals.
 125		 * We won't ever get here for the group leader, since it
 126		 * will have been the last reference on the signal_struct.
 127		 */
 128		task_cputime(tsk, &utime, &stime);
 129		sig->utime += utime;
 130		sig->stime += stime;
 131		sig->gtime += task_gtime(tsk);
 132		sig->min_flt += tsk->min_flt;
 133		sig->maj_flt += tsk->maj_flt;
 134		sig->nvcsw += tsk->nvcsw;
 135		sig->nivcsw += tsk->nivcsw;
 136		sig->inblock += task_io_get_inblock(tsk);
 137		sig->oublock += task_io_get_oublock(tsk);
 138		task_io_accounting_add(&sig->ioac, &tsk->ioac);
 139		sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
 140	}
 141
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 142	sig->nr_threads--;
 143	__unhash_process(tsk, group_dead);
 
 144
 145	/*
 146	 * Do this under ->siglock, we can race with another thread
 147	 * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals.
 148	 */
 149	flush_sigqueue(&tsk->pending);
 150	tsk->sighand = NULL;
 151	spin_unlock(&sighand->siglock);
 152
 153	__cleanup_sighand(sighand);
 154	clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
 155	if (group_dead) {
 156		flush_sigqueue(&sig->shared_pending);
 157		tty_kref_put(tty);
 158	}
 159}
 160
 161static void delayed_put_task_struct(struct rcu_head *rhp)
 162{
 163	struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
 164
 
 
 165	perf_event_delayed_put(tsk);
 166	trace_sched_process_free(tsk);
 167	put_task_struct(tsk);
 168}
 169
 
 
 
 
 
 170
 171void release_task(struct task_struct * p)
 
 
 
 
 172{
 173	struct task_struct *leader;
 
 174	int zap_leader;
 175repeat:
 176	/* don't need to get the RCU readlock here - the process is dead and
 177	 * can't be modifying its own credentials. But shut RCU-lockdep up */
 178	rcu_read_lock();
 179	atomic_dec(&__task_cred(p)->user->processes);
 180	rcu_read_unlock();
 181
 182	proc_flush_task(p);
 183
 184	write_lock_irq(&tasklist_lock);
 185	ptrace_release_task(p);
 
 186	__exit_signal(p);
 187
 188	/*
 189	 * If we are the last non-leader member of the thread
 190	 * group, and the leader is zombie, then notify the
 191	 * group leader's parent process. (if it wants notification.)
 192	 */
 193	zap_leader = 0;
 194	leader = p->group_leader;
 195	if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
 
 196		/*
 197		 * If we were the last child thread and the leader has
 198		 * exited already, and the leader's parent ignores SIGCHLD,
 199		 * then we are the one who should release the leader.
 200		 */
 201		zap_leader = do_notify_parent(leader, leader->exit_signal);
 202		if (zap_leader)
 203			leader->exit_state = EXIT_DEAD;
 204	}
 205
 206	write_unlock_irq(&tasklist_lock);
 
 
 
 207	release_thread(p);
 208	call_rcu(&p->rcu, delayed_put_task_struct);
 209
 210	p = leader;
 211	if (unlikely(zap_leader))
 212		goto repeat;
 213}
 214
 215/*
 216 * This checks not only the pgrp, but falls back on the pid if no
 217 * satisfactory pgrp is found. I dunno - gdb doesn't work correctly
 218 * without this...
 219 *
 220 * The caller must hold rcu lock or the tasklist lock.
 221 */
 222struct pid *session_of_pgrp(struct pid *pgrp)
 223{
 224	struct task_struct *p;
 225	struct pid *sid = NULL;
 
 
 226
 227	p = pid_task(pgrp, PIDTYPE_PGID);
 228	if (p == NULL)
 229		p = pid_task(pgrp, PIDTYPE_PID);
 230	if (p != NULL)
 231		sid = task_session(p);
 
 
 
 
 
 
 
 
 
 
 
 
 232
 233	return sid;
 234}
 
 235
 236/*
 237 * Determine if a process group is "orphaned", according to the POSIX
 238 * definition in 2.2.2.52.  Orphaned process groups are not to be affected
 239 * by terminal-generated stop signals.  Newly orphaned process groups are
 240 * to receive a SIGHUP and a SIGCONT.
 241 *
 242 * "I ask you, have you ever known what it is to be an orphan?"
 243 */
 244static int will_become_orphaned_pgrp(struct pid *pgrp, struct task_struct *ignored_task)
 
 245{
 246	struct task_struct *p;
 247
 248	do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
 249		if ((p == ignored_task) ||
 250		    (p->exit_state && thread_group_empty(p)) ||
 251		    is_global_init(p->real_parent))
 252			continue;
 253
 254		if (task_pgrp(p->real_parent) != pgrp &&
 255		    task_session(p->real_parent) == task_session(p))
 256			return 0;
 257	} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
 258
 259	return 1;
 260}
 261
 262int is_current_pgrp_orphaned(void)
 263{
 264	int retval;
 265
 266	read_lock(&tasklist_lock);
 267	retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
 268	read_unlock(&tasklist_lock);
 269
 270	return retval;
 271}
 272
 273static bool has_stopped_jobs(struct pid *pgrp)
 274{
 275	struct task_struct *p;
 276
 277	do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
 278		if (p->signal->flags & SIGNAL_STOP_STOPPED)
 279			return true;
 280	} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
 281
 282	return false;
 283}
 284
 285/*
 286 * Check to see if any process groups have become orphaned as
 287 * a result of our exiting, and if they have any stopped jobs,
 288 * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
 289 */
 290static void
 291kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent)
 292{
 293	struct pid *pgrp = task_pgrp(tsk);
 294	struct task_struct *ignored_task = tsk;
 295
 296	if (!parent)
 297		 /* exit: our father is in a different pgrp than
 298		  * we are and we were the only connection outside.
 299		  */
 300		parent = tsk->real_parent;
 301	else
 302		/* reparent: our child is in a different pgrp than
 303		 * we are, and it was the only connection outside.
 304		 */
 305		ignored_task = NULL;
 306
 307	if (task_pgrp(parent) != pgrp &&
 308	    task_session(parent) == task_session(tsk) &&
 309	    will_become_orphaned_pgrp(pgrp, ignored_task) &&
 310	    has_stopped_jobs(pgrp)) {
 311		__kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
 312		__kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
 313	}
 314}
 315
 316/*
 317 * Let kernel threads use this to say that they allow a certain signal.
 318 * Must not be used if kthread was cloned with CLONE_SIGHAND.
 319 */
 320int allow_signal(int sig)
 321{
 322	if (!valid_signal(sig) || sig < 1)
 323		return -EINVAL;
 324
 325	spin_lock_irq(&current->sighand->siglock);
 326	/* This is only needed for daemonize()'ed kthreads */
 327	sigdelset(&current->blocked, sig);
 328	/*
 329	 * Kernel threads handle their own signals. Let the signal code
 330	 * know it'll be handled, so that they don't get converted to
 331	 * SIGKILL or just silently dropped.
 332	 */
 333	current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2;
 334	recalc_sigpending();
 335	spin_unlock_irq(&current->sighand->siglock);
 336	return 0;
 337}
 338
 339EXPORT_SYMBOL(allow_signal);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 340
 341int disallow_signal(int sig)
 342{
 343	if (!valid_signal(sig) || sig < 1)
 344		return -EINVAL;
 
 
 
 
 
 
 
 345
 346	spin_lock_irq(&current->sighand->siglock);
 347	current->sighand->action[(sig)-1].sa.sa_handler = SIG_IGN;
 348	recalc_sigpending();
 349	spin_unlock_irq(&current->sighand->siglock);
 350	return 0;
 
 
 
 351}
 352
 353EXPORT_SYMBOL(disallow_signal);
 354
 355#ifdef CONFIG_MM_OWNER
 356/*
 357 * A task is exiting.   If it owned this mm, find a new owner for the mm.
 358 */
 359void mm_update_next_owner(struct mm_struct *mm)
 360{
 361	struct task_struct *c, *g, *p = current;
 362
 363retry:
 364	/*
 365	 * If the exiting or execing task is not the owner, it's
 366	 * someone else's problem.
 367	 */
 368	if (mm->owner != p)
 369		return;
 370	/*
 371	 * The current owner is exiting/execing and there are no other
 372	 * candidates.  Do not leave the mm pointing to a possibly
 373	 * freed task structure.
 374	 */
 375	if (atomic_read(&mm->mm_users) <= 1) {
 376		mm->owner = NULL;
 377		return;
 378	}
 379
 380	read_lock(&tasklist_lock);
 381	/*
 382	 * Search in the children
 383	 */
 384	list_for_each_entry(c, &p->children, sibling) {
 385		if (c->mm == mm)
 386			goto assign_new_owner;
 387	}
 388
 389	/*
 390	 * Search in the siblings
 391	 */
 392	list_for_each_entry(c, &p->real_parent->children, sibling) {
 393		if (c->mm == mm)
 394			goto assign_new_owner;
 395	}
 396
 397	/*
 398	 * Search through everything else. We should not get
 399	 * here often
 400	 */
 401	do_each_thread(g, c) {
 402		if (c->mm == mm)
 403			goto assign_new_owner;
 404	} while_each_thread(g, c);
 405
 
 
 
 
 
 406	read_unlock(&tasklist_lock);
 407	/*
 408	 * We found no owner yet mm_users > 1: this implies that we are
 409	 * most likely racing with swapoff (try_to_unuse()) or /proc or
 410	 * ptrace or page migration (get_task_mm()).  Mark owner as NULL.
 411	 */
 412	mm->owner = NULL;
 413	return;
 414
 415assign_new_owner:
 416	BUG_ON(c == p);
 417	get_task_struct(c);
 418	/*
 419	 * The task_lock protects c->mm from changing.
 420	 * We always want mm->owner->mm == mm
 421	 */
 422	task_lock(c);
 423	/*
 424	 * Delay read_unlock() till we have the task_lock()
 425	 * to ensure that c does not slip away underneath us
 426	 */
 427	read_unlock(&tasklist_lock);
 428	if (c->mm != mm) {
 429		task_unlock(c);
 430		put_task_struct(c);
 431		goto retry;
 432	}
 433	mm->owner = c;
 
 434	task_unlock(c);
 435	put_task_struct(c);
 436}
 437#endif /* CONFIG_MM_OWNER */
 438
 439/*
 440 * Turn us into a lazy TLB process if we
 441 * aren't already..
 442 */
 443static void exit_mm(struct task_struct * tsk)
 444{
 445	struct mm_struct *mm = tsk->mm;
 446	struct core_state *core_state;
 447
 448	mm_release(tsk, mm);
 449	if (!mm)
 450		return;
 451	sync_mm_rss(mm);
 452	/*
 453	 * Serialize with any possible pending coredump.
 454	 * We must hold mmap_sem around checking core_state
 455	 * and clearing tsk->mm.  The core-inducing thread
 456	 * will increment ->nr_threads for each thread in the
 457	 * group with ->mm != NULL.
 458	 */
 459	down_read(&mm->mmap_sem);
 460	core_state = mm->core_state;
 461	if (core_state) {
 462		struct core_thread self;
 463		up_read(&mm->mmap_sem);
 464
 465		self.task = tsk;
 466		self.next = xchg(&core_state->dumper.next, &self);
 467		/*
 468		 * Implies mb(), the result of xchg() must be visible
 469		 * to core_state->dumper.
 470		 */
 471		if (atomic_dec_and_test(&core_state->nr_threads))
 472			complete(&core_state->startup);
 473
 474		for (;;) {
 475			set_task_state(tsk, TASK_UNINTERRUPTIBLE);
 476			if (!self.task) /* see coredump_finish() */
 477				break;
 478			freezable_schedule();
 479		}
 480		__set_task_state(tsk, TASK_RUNNING);
 481		down_read(&mm->mmap_sem);
 482	}
 483	atomic_inc(&mm->mm_count);
 484	BUG_ON(mm != tsk->active_mm);
 485	/* more a memory barrier than a real lock */
 486	task_lock(tsk);
 487	tsk->mm = NULL;
 488	up_read(&mm->mmap_sem);
 
 
 
 
 
 
 
 
 
 
 
 
 489	enter_lazy_tlb(mm, current);
 490	task_unlock(tsk);
 
 
 491	mm_update_next_owner(mm);
 492	mmput(mm);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 493}
 494
 495/*
 496 * When we die, we re-parent all our children, and try to:
 497 * 1. give them to another thread in our thread group, if such a member exists
 498 * 2. give it to the first ancestor process which prctl'd itself as a
 499 *    child_subreaper for its children (like a service manager)
 500 * 3. give it to the init process (PID 1) in our pid namespace
 501 */
 502static struct task_struct *find_new_reaper(struct task_struct *father)
 503	__releases(&tasklist_lock)
 504	__acquires(&tasklist_lock)
 505{
 506	struct pid_namespace *pid_ns = task_active_pid_ns(father);
 507	struct task_struct *thread;
 508
 509	thread = father;
 510	while_each_thread(father, thread) {
 511		if (thread->flags & PF_EXITING)
 512			continue;
 513		if (unlikely(pid_ns->child_reaper == father))
 514			pid_ns->child_reaper = thread;
 515		return thread;
 516	}
 517
 518	if (unlikely(pid_ns->child_reaper == father)) {
 519		write_unlock_irq(&tasklist_lock);
 520		if (unlikely(pid_ns == &init_pid_ns)) {
 521			panic("Attempted to kill init! exitcode=0x%08x\n",
 522				father->signal->group_exit_code ?:
 523					father->exit_code);
 524		}
 525
 526		zap_pid_ns_processes(pid_ns);
 527		write_lock_irq(&tasklist_lock);
 528	} else if (father->signal->has_child_subreaper) {
 529		struct task_struct *reaper;
 530
 
 
 531		/*
 532		 * Find the first ancestor marked as child_subreaper.
 533		 * Note that the code below checks same_thread_group(reaper,
 534		 * pid_ns->child_reaper).  This is what we need to DTRT in a
 535		 * PID namespace. However we still need the check above, see
 536		 * http://marc.info/?l=linux-kernel&m=131385460420380
 
 537		 */
 538		for (reaper = father->real_parent;
 539		     reaper != &init_task;
 540		     reaper = reaper->real_parent) {
 541			if (same_thread_group(reaper, pid_ns->child_reaper))
 542				break;
 543			if (!reaper->signal->is_child_subreaper)
 544				continue;
 545			thread = reaper;
 546			do {
 547				if (!(thread->flags & PF_EXITING))
 548					return reaper;
 549			} while_each_thread(reaper, thread);
 550		}
 551	}
 552
 553	return pid_ns->child_reaper;
 554}
 555
 556/*
 557* Any that need to be release_task'd are put on the @dead list.
 558 */
 559static void reparent_leader(struct task_struct *father, struct task_struct *p,
 560				struct list_head *dead)
 561{
 562	list_move_tail(&p->sibling, &p->real_parent->children);
 563
 564	if (p->exit_state == EXIT_DEAD)
 565		return;
 566	/*
 567	 * If this is a threaded reparent there is no need to
 568	 * notify anyone anything has happened.
 569	 */
 570	if (same_thread_group(p->real_parent, father))
 571		return;
 572
 573	/* We don't want people slaying init. */
 574	p->exit_signal = SIGCHLD;
 575
 576	/* If it has exited notify the new parent about this child's death. */
 577	if (!p->ptrace &&
 578	    p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
 579		if (do_notify_parent(p, p->exit_signal)) {
 580			p->exit_state = EXIT_DEAD;
 581			list_move_tail(&p->sibling, dead);
 582		}
 583	}
 584
 585	kill_orphaned_pgrp(p, father);
 586}
 587
 588static void forget_original_parent(struct task_struct *father)
 
 
 
 
 
 
 
 
 
 589{
 590	struct task_struct *p, *n, *reaper;
 591	LIST_HEAD(dead_children);
 592
 593	write_lock_irq(&tasklist_lock);
 594	/*
 595	 * Note that exit_ptrace() and find_new_reaper() might
 596	 * drop tasklist_lock and reacquire it.
 597	 */
 598	exit_ptrace(father);
 599	reaper = find_new_reaper(father);
 600
 601	list_for_each_entry_safe(p, n, &father->children, sibling) {
 602		struct task_struct *t = p;
 603		do {
 604			t->real_parent = reaper;
 605			if (t->parent == father) {
 606				BUG_ON(t->ptrace);
 
 
 
 
 
 607				t->parent = t->real_parent;
 608			}
 609			if (t->pdeath_signal)
 610				group_send_sig_info(t->pdeath_signal,
 611						    SEND_SIG_NOINFO, t);
 612		} while_each_thread(p, t);
 613		reparent_leader(father, p, &dead_children);
 614	}
 615	write_unlock_irq(&tasklist_lock);
 616
 617	BUG_ON(!list_empty(&father->children));
 618
 619	list_for_each_entry_safe(p, n, &dead_children, sibling) {
 620		list_del_init(&p->sibling);
 621		release_task(p);
 622	}
 
 623}
 624
 625/*
 626 * Send signals to all our closest relatives so that they know
 627 * to properly mourn us..
 628 */
 629static void exit_notify(struct task_struct *tsk, int group_dead)
 630{
 631	bool autoreap;
 632
 633	/*
 634	 * This does two things:
 635	 *
 636  	 * A.  Make init inherit all the child processes
 637	 * B.  Check to see if any process groups have become orphaned
 638	 *	as a result of our exiting, and if they have any stopped
 639	 *	jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
 640	 */
 641	forget_original_parent(tsk);
 642
 643	write_lock_irq(&tasklist_lock);
 
 
 644	if (group_dead)
 645		kill_orphaned_pgrp(tsk->group_leader, NULL);
 646
 
 647	if (unlikely(tsk->ptrace)) {
 648		int sig = thread_group_leader(tsk) &&
 649				thread_group_empty(tsk) &&
 650				!ptrace_reparented(tsk) ?
 651			tsk->exit_signal : SIGCHLD;
 652		autoreap = do_notify_parent(tsk, sig);
 653	} else if (thread_group_leader(tsk)) {
 654		autoreap = thread_group_empty(tsk) &&
 655			do_notify_parent(tsk, tsk->exit_signal);
 656	} else {
 657		autoreap = true;
 658	}
 659
 660	tsk->exit_state = autoreap ? EXIT_DEAD : EXIT_ZOMBIE;
 
 
 
 661
 662	/* mt-exec, de_thread() is waiting for group leader */
 663	if (unlikely(tsk->signal->notify_count < 0))
 664		wake_up_process(tsk->signal->group_exit_task);
 665	write_unlock_irq(&tasklist_lock);
 666
 667	/* If the process is dead, release it - nobody will wait for it */
 668	if (autoreap)
 669		release_task(tsk);
 
 670}
 671
 672#ifdef CONFIG_DEBUG_STACK_USAGE
 673static void check_stack_usage(void)
 674{
 675	static DEFINE_SPINLOCK(low_water_lock);
 676	static int lowest_to_date = THREAD_SIZE;
 677	unsigned long free;
 678
 679	free = stack_not_used(current);
 680
 681	if (free >= lowest_to_date)
 682		return;
 683
 684	spin_lock(&low_water_lock);
 685	if (free < lowest_to_date) {
 686		printk(KERN_WARNING "%s (%d) used greatest stack depth: "
 687				"%lu bytes left\n",
 688				current->comm, task_pid_nr(current), free);
 689		lowest_to_date = free;
 690	}
 691	spin_unlock(&low_water_lock);
 692}
 693#else
 694static inline void check_stack_usage(void) {}
 695#endif
 696
 697void do_exit(long code)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 698{
 699	struct task_struct *tsk = current;
 700	int group_dead;
 701
 702	profile_task_exit(tsk);
 703
 704	WARN_ON(blk_needs_flush_plug(tsk));
 705
 706	if (unlikely(in_interrupt()))
 707		panic("Aiee, killing interrupt handler!");
 708	if (unlikely(!tsk->pid))
 709		panic("Attempted to kill the idle task!");
 710
 711	/*
 712	 * If do_exit is called because this processes oopsed, it's possible
 713	 * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before
 714	 * continuing. Amongst other possible reasons, this is to prevent
 715	 * mm_release()->clear_child_tid() from writing to a user-controlled
 716	 * kernel address.
 717	 */
 718	set_fs(USER_DS);
 719
 
 720	ptrace_event(PTRACE_EVENT_EXIT, code);
 
 721
 722	validate_creds_for_do_exit(tsk);
 723
 724	/*
 725	 * We're taking recursive faults here in do_exit. Safest is to just
 726	 * leave this task alone and wait for reboot.
 727	 */
 728	if (unlikely(tsk->flags & PF_EXITING)) {
 729		printk(KERN_ALERT
 730			"Fixing recursive fault but reboot is needed!\n");
 731		/*
 732		 * We can do this unlocked here. The futex code uses
 733		 * this flag just to verify whether the pi state
 734		 * cleanup has been done or not. In the worst case it
 735		 * loops once more. We pretend that the cleanup was
 736		 * done as there is no way to return. Either the
 737		 * OWNER_DIED bit is set by now or we push the blocked
 738		 * task into the wait for ever nirwana as well.
 739		 */
 740		tsk->flags |= PF_EXITPIDONE;
 741		set_current_state(TASK_UNINTERRUPTIBLE);
 742		schedule();
 743	}
 744
 745	exit_signals(tsk);  /* sets PF_EXITING */
 746	/*
 747	 * tsk->flags are checked in the futex code to protect against
 748	 * an exiting task cleaning up the robust pi futexes.
 749	 */
 750	smp_mb();
 751	raw_spin_unlock_wait(&tsk->pi_lock);
 752
 753	if (unlikely(in_atomic()))
 754		printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
 755				current->comm, task_pid_nr(current),
 756				preempt_count());
 757
 758	acct_update_integrals(tsk);
 759	/* sync mm's RSS info before statistics gathering */
 760	if (tsk->mm)
 761		sync_mm_rss(tsk->mm);
 762	group_dead = atomic_dec_and_test(&tsk->signal->live);
 763	if (group_dead) {
 
 
 
 
 
 
 
 
 
 764		hrtimer_cancel(&tsk->signal->real_timer);
 765		exit_itimers(tsk->signal);
 
 766		if (tsk->mm)
 767			setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm);
 768	}
 769	acct_collect(code, group_dead);
 770	if (group_dead)
 771		tty_audit_exit();
 772	audit_free(tsk);
 773
 774	tsk->exit_code = code;
 775	taskstats_exit(tsk, group_dead);
 776
 777	exit_mm(tsk);
 778
 779	if (group_dead)
 780		acct_process();
 781	trace_sched_process_exit(tsk);
 782
 783	exit_sem(tsk);
 784	exit_shm(tsk);
 785	exit_files(tsk);
 786	exit_fs(tsk);
 787	if (group_dead)
 788		disassociate_ctty(1);
 789	exit_task_namespaces(tsk);
 790	exit_task_work(tsk);
 791	exit_thread();
 792
 793	/*
 794	 * Flush inherited counters to the parent - before the parent
 795	 * gets woken up by child-exit notifications.
 796	 *
 797	 * because of cgroup mode, must be called before cgroup_exit()
 798	 */
 799	perf_event_exit_task(tsk);
 800
 
 801	cgroup_exit(tsk);
 802
 803	module_put(task_thread_info(tsk)->exec_domain->module);
 804
 805	/*
 806	 * FIXME: do that only when needed, using sched_exit tracepoint
 807	 */
 808	flush_ptrace_hw_breakpoint(tsk);
 809
 
 810	exit_notify(tsk, group_dead);
 811	proc_exit_connector(tsk);
 812#ifdef CONFIG_NUMA
 813	task_lock(tsk);
 814	mpol_put(tsk->mempolicy);
 815	tsk->mempolicy = NULL;
 816	task_unlock(tsk);
 817#endif
 818#ifdef CONFIG_FUTEX
 819	if (unlikely(current->pi_state_cache))
 820		kfree(current->pi_state_cache);
 821#endif
 822	/*
 823	 * Make sure we are holding no locks:
 824	 */
 825	debug_check_no_locks_held();
 826	/*
 827	 * We can do this unlocked here. The futex code uses this flag
 828	 * just to verify whether the pi state cleanup has been done
 829	 * or not. In the worst case it loops once more.
 830	 */
 831	tsk->flags |= PF_EXITPIDONE;
 832
 833	if (tsk->io_context)
 834		exit_io_context(tsk);
 835
 836	if (tsk->splice_pipe)
 837		free_pipe_info(tsk->splice_pipe);
 838
 839	if (tsk->task_frag.page)
 840		put_page(tsk->task_frag.page);
 841
 842	validate_creds_for_do_exit(tsk);
 843
 844	check_stack_usage();
 845	preempt_disable();
 846	if (tsk->nr_dirtied)
 847		__this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied);
 848	exit_rcu();
 
 
 
 
 
 849
 
 
 850	/*
 851	 * The setting of TASK_RUNNING by try_to_wake_up() may be delayed
 852	 * when the following two conditions become true.
 853	 *   - There is race condition of mmap_sem (It is acquired by
 854	 *     exit_mm()), and
 855	 *   - SMI occurs before setting TASK_RUNINNG.
 856	 *     (or hypervisor of virtual machine switches to other guest)
 857	 *  As a result, we may become TASK_RUNNING after becoming TASK_DEAD
 858	 *
 859	 * To avoid it, we have to wait for releasing tsk->pi_lock which
 860	 * is held by try_to_wake_up()
 
 
 861	 */
 862	smp_mb();
 863	raw_spin_unlock_wait(&tsk->pi_lock);
 864
 865	/* causes final put_task_struct in finish_task_switch(). */
 866	tsk->state = TASK_DEAD;
 867	tsk->flags |= PF_NOFREEZE;	/* tell freezer to ignore us */
 868	schedule();
 869	BUG();
 870	/* Avoid "noreturn function does return".  */
 871	for (;;)
 872		cpu_relax();	/* For when BUG is null */
 873}
 874
 875EXPORT_SYMBOL_GPL(do_exit);
 
 
 
 
 
 
 
 
 
 
 876
 877void complete_and_exit(struct completion *comp, long code)
 878{
 879	if (comp)
 880		complete(comp);
 
 
 
 
 
 
 
 
 
 881
 882	do_exit(code);
 883}
 
 
 
 
 
 
 
 
 
 884
 885EXPORT_SYMBOL(complete_and_exit);
 
 886
 887SYSCALL_DEFINE1(exit, int, error_code)
 888{
 889	do_exit((error_code&0xff)<<8);
 890}
 891
 892/*
 893 * Take down every thread in the group.  This is called by fatal signals
 894 * as well as by sys_exit_group (below).
 895 */
 896void
 897do_group_exit(int exit_code)
 898{
 899	struct signal_struct *sig = current->signal;
 900
 901	BUG_ON(exit_code & 0x80); /* core dumps don't get here */
 902
 903	if (signal_group_exit(sig))
 904		exit_code = sig->group_exit_code;
 905	else if (!thread_group_empty(current)) {
 
 
 906		struct sighand_struct *const sighand = current->sighand;
 
 907		spin_lock_irq(&sighand->siglock);
 908		if (signal_group_exit(sig))
 909			/* Another thread got here before we took the lock.  */
 910			exit_code = sig->group_exit_code;
 
 
 911		else {
 912			sig->group_exit_code = exit_code;
 913			sig->flags = SIGNAL_GROUP_EXIT;
 914			zap_other_threads(current);
 915		}
 916		spin_unlock_irq(&sighand->siglock);
 917	}
 918
 919	do_exit(exit_code);
 920	/* NOTREACHED */
 921}
 922
 923/*
 924 * this kills every thread in the thread group. Note that any externally
 925 * wait4()-ing process will get the correct exit code - even if this
 926 * thread is not the thread group leader.
 927 */
 928SYSCALL_DEFINE1(exit_group, int, error_code)
 929{
 930	do_group_exit((error_code & 0xff) << 8);
 931	/* NOTREACHED */
 932	return 0;
 933}
 934
 935struct wait_opts {
 936	enum pid_type		wo_type;
 937	int			wo_flags;
 938	struct pid		*wo_pid;
 939
 940	struct siginfo __user	*wo_info;
 941	int __user		*wo_stat;
 942	struct rusage __user	*wo_rusage;
 943
 944	wait_queue_t		child_wait;
 945	int			notask_error;
 946};
 947
 948static inline
 949struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
 950{
 951	if (type != PIDTYPE_PID)
 952		task = task->group_leader;
 953	return task->pids[type].pid;
 954}
 955
 956static int eligible_pid(struct wait_opts *wo, struct task_struct *p)
 957{
 958	return	wo->wo_type == PIDTYPE_MAX ||
 959		task_pid_type(p, wo->wo_type) == wo->wo_pid;
 960}
 961
 962static int eligible_child(struct wait_opts *wo, struct task_struct *p)
 
 963{
 964	if (!eligible_pid(wo, p))
 965		return 0;
 966	/* Wait for all children (clone and not) if __WALL is set;
 967	 * otherwise, wait for clone children *only* if __WCLONE is
 968	 * set; otherwise, wait for non-clone children *only*.  (Note:
 969	 * A "clone" child here is one that reports to its parent
 970	 * using a signal other than SIGCHLD.) */
 971	if (((p->exit_signal != SIGCHLD) ^ !!(wo->wo_flags & __WCLONE))
 972	    && !(wo->wo_flags & __WALL))
 973		return 0;
 974
 975	return 1;
 976}
 
 
 
 
 977
 978static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
 979				pid_t pid, uid_t uid, int why, int status)
 980{
 981	struct siginfo __user *infop;
 982	int retval = wo->wo_rusage
 983		? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
 
 
 
 
 984
 985	put_task_struct(p);
 986	infop = wo->wo_info;
 987	if (infop) {
 988		if (!retval)
 989			retval = put_user(SIGCHLD, &infop->si_signo);
 990		if (!retval)
 991			retval = put_user(0, &infop->si_errno);
 992		if (!retval)
 993			retval = put_user((short)why, &infop->si_code);
 994		if (!retval)
 995			retval = put_user(pid, &infop->si_pid);
 996		if (!retval)
 997			retval = put_user(uid, &infop->si_uid);
 998		if (!retval)
 999			retval = put_user(status, &infop->si_status);
1000	}
1001	if (!retval)
1002		retval = pid;
1003	return retval;
1004}
1005
1006/*
1007 * Handle sys_wait4 work for one task in state EXIT_ZOMBIE.  We hold
1008 * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1009 * the lock and this task is uninteresting.  If we return nonzero, we have
1010 * released the lock and the system call should return.
1011 */
1012static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
1013{
1014	unsigned long state;
1015	int retval, status, traced;
1016	pid_t pid = task_pid_vnr(p);
1017	uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p));
1018	struct siginfo __user *infop;
1019
1020	if (!likely(wo->wo_flags & WEXITED))
1021		return 0;
1022
1023	if (unlikely(wo->wo_flags & WNOWAIT)) {
1024		int exit_code = p->exit_code;
1025		int why;
1026
1027		get_task_struct(p);
1028		read_unlock(&tasklist_lock);
1029		if ((exit_code & 0x7f) == 0) {
1030			why = CLD_EXITED;
1031			status = exit_code >> 8;
1032		} else {
1033			why = (exit_code & 0x80) ? CLD_DUMPED : CLD_KILLED;
1034			status = exit_code & 0x7f;
1035		}
1036		return wait_noreap_copyout(wo, p, pid, uid, why, status);
1037	}
1038
1039	traced = ptrace_reparented(p);
1040	/*
1041	 * Move the task's state to DEAD/TRACE, only one thread can do this.
1042	 */
1043	state = traced && thread_group_leader(p) ? EXIT_TRACE : EXIT_DEAD;
 
1044	if (cmpxchg(&p->exit_state, EXIT_ZOMBIE, state) != EXIT_ZOMBIE)
1045		return 0;
1046	/*
1047	 * It can be ptraced but not reparented, check
1048	 * thread_group_leader() to filter out sub-threads.
 
 
 
 
 
1049	 */
1050	if (likely(!traced) && thread_group_leader(p)) {
1051		struct signal_struct *psig;
1052		struct signal_struct *sig;
1053		unsigned long maxrss;
1054		cputime_t tgutime, tgstime;
1055
1056		/*
1057		 * The resource counters for the group leader are in its
1058		 * own task_struct.  Those for dead threads in the group
1059		 * are in its signal_struct, as are those for the child
1060		 * processes it has previously reaped.  All these
1061		 * accumulate in the parent's signal_struct c* fields.
1062		 *
1063		 * We don't bother to take a lock here to protect these
1064		 * p->signal fields, because they are only touched by
1065		 * __exit_signal, which runs with tasklist_lock
1066		 * write-locked anyway, and so is excluded here.  We do
1067		 * need to protect the access to parent->signal fields,
1068		 * as other threads in the parent group can be right
1069		 * here reaping other children at the same time.
1070		 *
1071		 * We use thread_group_cputime_adjusted() to get times for the thread
1072		 * group, which consolidates times for all threads in the
1073		 * group including the group leader.
 
 
 
1074		 */
1075		thread_group_cputime_adjusted(p, &tgutime, &tgstime);
1076		spin_lock_irq(&p->real_parent->sighand->siglock);
1077		psig = p->real_parent->signal;
1078		sig = p->signal;
1079		psig->cutime += tgutime + sig->cutime;
1080		psig->cstime += tgstime + sig->cstime;
1081		psig->cgtime += task_gtime(p) + sig->gtime + sig->cgtime;
1082		psig->cmin_flt +=
1083			p->min_flt + sig->min_flt + sig->cmin_flt;
1084		psig->cmaj_flt +=
1085			p->maj_flt + sig->maj_flt + sig->cmaj_flt;
1086		psig->cnvcsw +=
1087			p->nvcsw + sig->nvcsw + sig->cnvcsw;
1088		psig->cnivcsw +=
1089			p->nivcsw + sig->nivcsw + sig->cnivcsw;
1090		psig->cinblock +=
1091			task_io_get_inblock(p) +
1092			sig->inblock + sig->cinblock;
1093		psig->coublock +=
1094			task_io_get_oublock(p) +
1095			sig->oublock + sig->coublock;
1096		maxrss = max(sig->maxrss, sig->cmaxrss);
1097		if (psig->cmaxrss < maxrss)
1098			psig->cmaxrss = maxrss;
1099		task_io_accounting_add(&psig->ioac, &p->ioac);
1100		task_io_accounting_add(&psig->ioac, &sig->ioac);
1101		spin_unlock_irq(&p->real_parent->sighand->siglock);
1102	}
1103
1104	/*
1105	 * Now we are sure this task is interesting, and no other
1106	 * thread can reap it because we its state == DEAD/TRACE.
1107	 */
1108	read_unlock(&tasklist_lock);
1109
1110	retval = wo->wo_rusage
1111		? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1112	status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1113		? p->signal->group_exit_code : p->exit_code;
1114	if (!retval && wo->wo_stat)
1115		retval = put_user(status, wo->wo_stat);
1116
1117	infop = wo->wo_info;
1118	if (!retval && infop)
1119		retval = put_user(SIGCHLD, &infop->si_signo);
1120	if (!retval && infop)
1121		retval = put_user(0, &infop->si_errno);
1122	if (!retval && infop) {
1123		int why;
1124
1125		if ((status & 0x7f) == 0) {
1126			why = CLD_EXITED;
1127			status >>= 8;
1128		} else {
1129			why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
1130			status &= 0x7f;
1131		}
1132		retval = put_user((short)why, &infop->si_code);
1133		if (!retval)
1134			retval = put_user(status, &infop->si_status);
1135	}
1136	if (!retval && infop)
1137		retval = put_user(pid, &infop->si_pid);
1138	if (!retval && infop)
1139		retval = put_user(uid, &infop->si_uid);
1140	if (!retval)
1141		retval = pid;
1142
1143	if (state == EXIT_TRACE) {
1144		write_lock_irq(&tasklist_lock);
1145		/* We dropped tasklist, ptracer could die and untrace */
1146		ptrace_unlink(p);
1147
1148		/* If parent wants a zombie, don't release it now */
1149		state = EXIT_ZOMBIE;
1150		if (do_notify_parent(p, p->exit_signal))
1151			state = EXIT_DEAD;
1152		p->exit_state = state;
1153		write_unlock_irq(&tasklist_lock);
1154	}
1155	if (state == EXIT_DEAD)
1156		release_task(p);
1157
1158	return retval;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1159}
1160
1161static int *task_stopped_code(struct task_struct *p, bool ptrace)
1162{
1163	if (ptrace) {
1164		if (task_is_stopped_or_traced(p) &&
1165		    !(p->jobctl & JOBCTL_LISTENING))
1166			return &p->exit_code;
1167	} else {
1168		if (p->signal->flags & SIGNAL_STOP_STOPPED)
1169			return &p->signal->group_exit_code;
1170	}
1171	return NULL;
1172}
1173
1174/**
1175 * wait_task_stopped - Wait for %TASK_STOPPED or %TASK_TRACED
1176 * @wo: wait options
1177 * @ptrace: is the wait for ptrace
1178 * @p: task to wait for
1179 *
1180 * Handle sys_wait4() work for %p in state %TASK_STOPPED or %TASK_TRACED.
1181 *
1182 * CONTEXT:
1183 * read_lock(&tasklist_lock), which is released if return value is
1184 * non-zero.  Also, grabs and releases @p->sighand->siglock.
1185 *
1186 * RETURNS:
1187 * 0 if wait condition didn't exist and search for other wait conditions
1188 * should continue.  Non-zero return, -errno on failure and @p's pid on
1189 * success, implies that tasklist_lock is released and wait condition
1190 * search should terminate.
1191 */
1192static int wait_task_stopped(struct wait_opts *wo,
1193				int ptrace, struct task_struct *p)
1194{
1195	struct siginfo __user *infop;
1196	int retval, exit_code, *p_code, why;
1197	uid_t uid = 0; /* unneeded, required by compiler */
1198	pid_t pid;
1199
1200	/*
1201	 * Traditionally we see ptrace'd stopped tasks regardless of options.
1202	 */
1203	if (!ptrace && !(wo->wo_flags & WUNTRACED))
1204		return 0;
1205
1206	if (!task_stopped_code(p, ptrace))
1207		return 0;
1208
1209	exit_code = 0;
1210	spin_lock_irq(&p->sighand->siglock);
1211
1212	p_code = task_stopped_code(p, ptrace);
1213	if (unlikely(!p_code))
1214		goto unlock_sig;
1215
1216	exit_code = *p_code;
1217	if (!exit_code)
1218		goto unlock_sig;
1219
1220	if (!unlikely(wo->wo_flags & WNOWAIT))
1221		*p_code = 0;
1222
1223	uid = from_kuid_munged(current_user_ns(), task_uid(p));
1224unlock_sig:
1225	spin_unlock_irq(&p->sighand->siglock);
1226	if (!exit_code)
1227		return 0;
1228
1229	/*
1230	 * Now we are pretty sure this task is interesting.
1231	 * Make sure it doesn't get reaped out from under us while we
1232	 * give up the lock and then examine it below.  We don't want to
1233	 * keep holding onto the tasklist_lock while we call getrusage and
1234	 * possibly take page faults for user memory.
1235	 */
1236	get_task_struct(p);
1237	pid = task_pid_vnr(p);
1238	why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
1239	read_unlock(&tasklist_lock);
 
 
 
 
1240
1241	if (unlikely(wo->wo_flags & WNOWAIT))
1242		return wait_noreap_copyout(wo, p, pid, uid, why, exit_code);
1243
1244	retval = wo->wo_rusage
1245		? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1246	if (!retval && wo->wo_stat)
1247		retval = put_user((exit_code << 8) | 0x7f, wo->wo_stat);
1248
1249	infop = wo->wo_info;
1250	if (!retval && infop)
1251		retval = put_user(SIGCHLD, &infop->si_signo);
1252	if (!retval && infop)
1253		retval = put_user(0, &infop->si_errno);
1254	if (!retval && infop)
1255		retval = put_user((short)why, &infop->si_code);
1256	if (!retval && infop)
1257		retval = put_user(exit_code, &infop->si_status);
1258	if (!retval && infop)
1259		retval = put_user(pid, &infop->si_pid);
1260	if (!retval && infop)
1261		retval = put_user(uid, &infop->si_uid);
1262	if (!retval)
1263		retval = pid;
1264	put_task_struct(p);
1265
1266	BUG_ON(!retval);
1267	return retval;
1268}
1269
1270/*
1271 * Handle do_wait work for one task in a live, non-stopped state.
1272 * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1273 * the lock and this task is uninteresting.  If we return nonzero, we have
1274 * released the lock and the system call should return.
1275 */
1276static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
1277{
1278	int retval;
1279	pid_t pid;
1280	uid_t uid;
1281
1282	if (!unlikely(wo->wo_flags & WCONTINUED))
1283		return 0;
1284
1285	if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
1286		return 0;
1287
1288	spin_lock_irq(&p->sighand->siglock);
1289	/* Re-check with the lock held.  */
1290	if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
1291		spin_unlock_irq(&p->sighand->siglock);
1292		return 0;
1293	}
1294	if (!unlikely(wo->wo_flags & WNOWAIT))
1295		p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1296	uid = from_kuid_munged(current_user_ns(), task_uid(p));
1297	spin_unlock_irq(&p->sighand->siglock);
1298
1299	pid = task_pid_vnr(p);
1300	get_task_struct(p);
1301	read_unlock(&tasklist_lock);
 
 
 
 
1302
1303	if (!wo->wo_info) {
1304		retval = wo->wo_rusage
1305			? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1306		put_task_struct(p);
1307		if (!retval && wo->wo_stat)
1308			retval = put_user(0xffff, wo->wo_stat);
1309		if (!retval)
1310			retval = pid;
1311	} else {
1312		retval = wait_noreap_copyout(wo, p, pid, uid,
1313					     CLD_CONTINUED, SIGCONT);
1314		BUG_ON(retval == 0);
 
1315	}
1316
1317	return retval;
1318}
1319
1320/*
1321 * Consider @p for a wait by @parent.
1322 *
1323 * -ECHILD should be in ->notask_error before the first call.
1324 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1325 * Returns zero if the search for a child should continue;
1326 * then ->notask_error is 0 if @p is an eligible child,
1327 * or another error from security_task_wait(), or still -ECHILD.
1328 */
1329static int wait_consider_task(struct wait_opts *wo, int ptrace,
1330				struct task_struct *p)
1331{
 
 
 
 
 
 
1332	int ret;
1333
1334	if (unlikely(p->exit_state == EXIT_DEAD))
1335		return 0;
1336
1337	ret = eligible_child(wo, p);
1338	if (!ret)
1339		return ret;
1340
1341	ret = security_task_wait(p);
1342	if (unlikely(ret < 0)) {
1343		/*
1344		 * If we have not yet seen any eligible child,
1345		 * then let this error code replace -ECHILD.
1346		 * A permission error will give the user a clue
1347		 * to look for security policy problems, rather
1348		 * than for mysterious wait bugs.
1349		 */
1350		if (wo->notask_error)
1351			wo->notask_error = ret;
1352		return 0;
1353	}
1354
1355	if (unlikely(p->exit_state == EXIT_TRACE)) {
1356		/*
1357		 * ptrace == 0 means we are the natural parent. In this case
1358		 * we should clear notask_error, debugger will notify us.
1359		 */
1360		if (likely(!ptrace))
1361			wo->notask_error = 0;
1362		return 0;
1363	}
1364
1365	if (likely(!ptrace) && unlikely(p->ptrace)) {
1366		/*
1367		 * If it is traced by its real parent's group, just pretend
1368		 * the caller is ptrace_do_wait() and reap this child if it
1369		 * is zombie.
1370		 *
1371		 * This also hides group stop state from real parent; otherwise
1372		 * a single stop can be reported twice as group and ptrace stop.
1373		 * If a ptracer wants to distinguish these two events for its
1374		 * own children it should create a separate process which takes
1375		 * the role of real parent.
1376		 */
1377		if (!ptrace_reparented(p))
1378			ptrace = 1;
1379	}
1380
1381	/* slay zombie? */
1382	if (p->exit_state == EXIT_ZOMBIE) {
1383		/* we don't reap group leaders with subthreads */
1384		if (!delay_group_leader(p)) {
1385			/*
1386			 * A zombie ptracee is only visible to its ptracer.
1387			 * Notification and reaping will be cascaded to the
1388			 * real parent when the ptracer detaches.
1389			 */
1390			if (unlikely(ptrace) || likely(!p->ptrace))
1391				return wait_task_zombie(wo, p);
1392		}
1393
1394		/*
1395		 * Allow access to stopped/continued state via zombie by
1396		 * falling through.  Clearing of notask_error is complex.
1397		 *
1398		 * When !@ptrace:
1399		 *
1400		 * If WEXITED is set, notask_error should naturally be
1401		 * cleared.  If not, subset of WSTOPPED|WCONTINUED is set,
1402		 * so, if there are live subthreads, there are events to
1403		 * wait for.  If all subthreads are dead, it's still safe
1404		 * to clear - this function will be called again in finite
1405		 * amount time once all the subthreads are released and
1406		 * will then return without clearing.
1407		 *
1408		 * When @ptrace:
1409		 *
1410		 * Stopped state is per-task and thus can't change once the
1411		 * target task dies.  Only continued and exited can happen.
1412		 * Clear notask_error if WCONTINUED | WEXITED.
1413		 */
1414		if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED)))
1415			wo->notask_error = 0;
1416	} else {
1417		/*
1418		 * @p is alive and it's gonna stop, continue or exit, so
1419		 * there always is something to wait for.
1420		 */
1421		wo->notask_error = 0;
1422	}
1423
1424	/*
1425	 * Wait for stopped.  Depending on @ptrace, different stopped state
1426	 * is used and the two don't interact with each other.
1427	 */
1428	ret = wait_task_stopped(wo, ptrace, p);
1429	if (ret)
1430		return ret;
1431
1432	/*
1433	 * Wait for continued.  There's only one continued state and the
1434	 * ptracer can consume it which can confuse the real parent.  Don't
1435	 * use WCONTINUED from ptracer.  You don't need or want it.
1436	 */
1437	return wait_task_continued(wo, p);
1438}
1439
1440/*
1441 * Do the work of do_wait() for one thread in the group, @tsk.
1442 *
1443 * -ECHILD should be in ->notask_error before the first call.
1444 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1445 * Returns zero if the search for a child should continue; then
1446 * ->notask_error is 0 if there were any eligible children,
1447 * or another error from security_task_wait(), or still -ECHILD.
1448 */
1449static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk)
1450{
1451	struct task_struct *p;
1452
1453	list_for_each_entry(p, &tsk->children, sibling) {
1454		int ret = wait_consider_task(wo, 0, p);
 
1455		if (ret)
1456			return ret;
1457	}
1458
1459	return 0;
1460}
1461
1462static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk)
1463{
1464	struct task_struct *p;
1465
1466	list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
1467		int ret = wait_consider_task(wo, 1, p);
 
1468		if (ret)
1469			return ret;
1470	}
1471
1472	return 0;
1473}
1474
1475static int child_wait_callback(wait_queue_t *wait, unsigned mode,
 
 
 
 
 
 
 
 
 
 
 
1476				int sync, void *key)
1477{
1478	struct wait_opts *wo = container_of(wait, struct wait_opts,
1479						child_wait);
1480	struct task_struct *p = key;
1481
1482	if (!eligible_pid(wo, p))
1483		return 0;
1484
1485	if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent)
1486		return 0;
1487
1488	return default_wake_function(wait, mode, sync, key);
1489}
1490
1491void __wake_up_parent(struct task_struct *p, struct task_struct *parent)
1492{
1493	__wake_up_sync_key(&parent->signal->wait_chldexit,
1494				TASK_INTERRUPTIBLE, 1, p);
1495}
1496
1497static long do_wait(struct wait_opts *wo)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1498{
1499	struct task_struct *tsk;
 
1500	int retval;
1501
1502	trace_sched_process_wait(wo->wo_pid);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1503
1504	init_waitqueue_func_entry(&wo->child_wait, child_wait_callback);
1505	wo->child_wait.private = current;
1506	add_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1507repeat:
1508	/*
1509	 * If there is nothing that can match our critiera just get out.
1510	 * We will clear ->notask_error to zero if we see any child that
1511	 * might later match our criteria, even if we are not able to reap
1512	 * it yet.
1513	 */
1514	wo->notask_error = -ECHILD;
1515	if ((wo->wo_type < PIDTYPE_MAX) &&
1516	   (!wo->wo_pid || hlist_empty(&wo->wo_pid->tasks[wo->wo_type])))
1517		goto notask;
1518
1519	set_current_state(TASK_INTERRUPTIBLE);
1520	read_lock(&tasklist_lock);
1521	tsk = current;
1522	do {
1523		retval = do_wait_thread(wo, tsk);
1524		if (retval)
1525			goto end;
1526
1527		retval = ptrace_do_wait(wo, tsk);
 
1528		if (retval)
1529			goto end;
 
 
1530
1531		if (wo->wo_flags & __WNOTHREAD)
1532			break;
1533	} while_each_thread(current, tsk);
 
 
 
 
 
 
 
 
 
 
1534	read_unlock(&tasklist_lock);
1535
1536notask:
1537	retval = wo->notask_error;
1538	if (!retval && !(wo->wo_flags & WNOHANG)) {
1539		retval = -ERESTARTSYS;
1540		if (!signal_pending(current)) {
1541			schedule();
1542			goto repeat;
1543		}
1544	}
1545end:
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1546	__set_current_state(TASK_RUNNING);
1547	remove_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1548	return retval;
1549}
1550
1551SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
1552		infop, int, options, struct rusage __user *, ru)
 
1553{
1554	struct wait_opts wo;
1555	struct pid *pid = NULL;
1556	enum pid_type type;
1557	long ret;
1558
1559	if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED))
 
1560		return -EINVAL;
1561	if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
1562		return -EINVAL;
1563
1564	switch (which) {
1565	case P_ALL:
1566		type = PIDTYPE_MAX;
1567		break;
1568	case P_PID:
1569		type = PIDTYPE_PID;
1570		if (upid <= 0)
1571			return -EINVAL;
 
 
1572		break;
1573	case P_PGID:
1574		type = PIDTYPE_PGID;
1575		if (upid <= 0)
1576			return -EINVAL;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1577		break;
1578	default:
1579		return -EINVAL;
1580	}
1581
1582	if (type < PIDTYPE_MAX)
1583		pid = find_get_pid(upid);
 
 
 
 
 
1584
1585	wo.wo_type	= type;
1586	wo.wo_pid	= pid;
1587	wo.wo_flags	= options;
1588	wo.wo_info	= infop;
1589	wo.wo_stat	= NULL;
1590	wo.wo_rusage	= ru;
1591	ret = do_wait(&wo);
1592
1593	if (ret > 0) {
1594		ret = 0;
1595	} else if (infop) {
1596		/*
1597		 * For a WNOHANG return, clear out all the fields
1598		 * we would set so the user can easily tell the
1599		 * difference.
1600		 */
1601		if (!ret)
1602			ret = put_user(0, &infop->si_signo);
1603		if (!ret)
1604			ret = put_user(0, &infop->si_errno);
1605		if (!ret)
1606			ret = put_user(0, &infop->si_code);
1607		if (!ret)
1608			ret = put_user(0, &infop->si_pid);
1609		if (!ret)
1610			ret = put_user(0, &infop->si_uid);
1611		if (!ret)
1612			ret = put_user(0, &infop->si_status);
1613	}
1614
1615	put_pid(pid);
 
 
 
 
 
 
 
 
1616	return ret;
1617}
1618
1619SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
1620		int, options, struct rusage __user *, ru)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1621{
1622	struct wait_opts wo;
1623	struct pid *pid = NULL;
1624	enum pid_type type;
1625	long ret;
1626
1627	if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
1628			__WNOTHREAD|__WCLONE|__WALL))
1629		return -EINVAL;
1630
 
 
 
 
1631	if (upid == -1)
1632		type = PIDTYPE_MAX;
1633	else if (upid < 0) {
1634		type = PIDTYPE_PGID;
1635		pid = find_get_pid(-upid);
1636	} else if (upid == 0) {
1637		type = PIDTYPE_PGID;
1638		pid = get_task_pid(current, PIDTYPE_PGID);
1639	} else /* upid > 0 */ {
1640		type = PIDTYPE_PID;
1641		pid = find_get_pid(upid);
1642	}
1643
1644	wo.wo_type	= type;
1645	wo.wo_pid	= pid;
1646	wo.wo_flags	= options | WEXITED;
1647	wo.wo_info	= NULL;
1648	wo.wo_stat	= stat_addr;
1649	wo.wo_rusage	= ru;
1650	ret = do_wait(&wo);
1651	put_pid(pid);
 
 
1652
1653	return ret;
1654}
1655
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1656#ifdef __ARCH_WANT_SYS_WAITPID
1657
1658/*
1659 * sys_waitpid() remains for compatibility. waitpid() should be
1660 * implemented by calling sys_wait4() from libc.a.
1661 */
1662SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options)
1663{
1664	return sys_wait4(pid, stat_addr, options, NULL);
1665}
1666
1667#endif