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/binfmts.h>
  24#include <linux/nsproxy.h>
  25#include <linux/pid_namespace.h>
  26#include <linux/ptrace.h>
  27#include <linux/profile.h>
  28#include <linux/mount.h>
  29#include <linux/proc_fs.h>
  30#include <linux/kthread.h>
  31#include <linux/mempolicy.h>
  32#include <linux/taskstats_kern.h>
  33#include <linux/delayacct.h>
  34#include <linux/freezer.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
  55#include <asm/uaccess.h>
  56#include <asm/unistd.h>
  57#include <asm/pgtable.h>
  58#include <asm/mmu_context.h>
  59
  60static void exit_mm(struct task_struct * tsk);
  61
  62static void __unhash_process(struct task_struct *p, bool group_dead)
  63{
  64	nr_threads--;
  65	detach_pid(p, PIDTYPE_PID);
  66	if (group_dead) {
 
  67		detach_pid(p, PIDTYPE_PGID);
  68		detach_pid(p, PIDTYPE_SID);
  69
  70		list_del_rcu(&p->tasks);
  71		list_del_init(&p->sibling);
  72		__this_cpu_dec(process_counts);
  73	}
  74	list_del_rcu(&p->thread_group);
 
  75}
  76
  77/*
  78 * This function expects the tasklist_lock write-locked.
  79 */
  80static void __exit_signal(struct task_struct *tsk)
  81{
  82	struct signal_struct *sig = tsk->signal;
  83	bool group_dead = thread_group_leader(tsk);
  84	struct sighand_struct *sighand;
  85	struct tty_struct *uninitialized_var(tty);
 
  86
  87	sighand = rcu_dereference_check(tsk->sighand,
  88					lockdep_tasklist_lock_is_held());
  89	spin_lock(&sighand->siglock);
  90
 
  91	posix_cpu_timers_exit(tsk);
  92	if (group_dead) {
  93		posix_cpu_timers_exit_group(tsk);
 
 
 
  94		tty = sig->tty;
  95		sig->tty = NULL;
  96	} else {
  97		/*
  98		 * This can only happen if the caller is de_thread().
  99		 * FIXME: this is the temporary hack, we should teach
 100		 * posix-cpu-timers to handle this case correctly.
 101		 */
 102		if (unlikely(has_group_leader_pid(tsk)))
 103			posix_cpu_timers_exit_group(tsk);
 104
 105		/*
 106		 * If there is any task waiting for the group exit
 107		 * then notify it:
 108		 */
 109		if (sig->notify_count > 0 && !--sig->notify_count)
 110			wake_up_process(sig->group_exit_task);
 111
 112		if (tsk == sig->curr_target)
 113			sig->curr_target = next_thread(tsk);
 114		/*
 115		 * Accumulate here the counters for all threads but the
 116		 * group leader as they die, so they can be added into
 117		 * the process-wide totals when those are taken.
 118		 * The group leader stays around as a zombie as long
 119		 * as there are other threads.  When it gets reaped,
 120		 * the exit.c code will add its counts into these totals.
 121		 * We won't ever get here for the group leader, since it
 122		 * will have been the last reference on the signal_struct.
 123		 */
 124		sig->utime = cputime_add(sig->utime, tsk->utime);
 125		sig->stime = cputime_add(sig->stime, tsk->stime);
 126		sig->gtime = cputime_add(sig->gtime, tsk->gtime);
 127		sig->min_flt += tsk->min_flt;
 128		sig->maj_flt += tsk->maj_flt;
 129		sig->nvcsw += tsk->nvcsw;
 130		sig->nivcsw += tsk->nivcsw;
 131		sig->inblock += task_io_get_inblock(tsk);
 132		sig->oublock += task_io_get_oublock(tsk);
 133		task_io_accounting_add(&sig->ioac, &tsk->ioac);
 134		sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
 135	}
 136
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 137	sig->nr_threads--;
 138	__unhash_process(tsk, group_dead);
 
 139
 140	/*
 141	 * Do this under ->siglock, we can race with another thread
 142	 * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals.
 143	 */
 144	flush_sigqueue(&tsk->pending);
 145	tsk->sighand = NULL;
 146	spin_unlock(&sighand->siglock);
 147
 148	__cleanup_sighand(sighand);
 149	clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
 150	if (group_dead) {
 151		flush_sigqueue(&sig->shared_pending);
 152		tty_kref_put(tty);
 153	}
 154}
 155
 156static void delayed_put_task_struct(struct rcu_head *rhp)
 157{
 158	struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
 159
 160	perf_event_delayed_put(tsk);
 161	trace_sched_process_free(tsk);
 162	put_task_struct(tsk);
 163}
 164
 
 
 
 
 
 165
 166void release_task(struct task_struct * p)
 167{
 168	struct task_struct *leader;
 
 169	int zap_leader;
 170repeat:
 171	/* don't need to get the RCU readlock here - the process is dead and
 172	 * can't be modifying its own credentials. But shut RCU-lockdep up */
 173	rcu_read_lock();
 174	atomic_dec(&__task_cred(p)->user->processes);
 175	rcu_read_unlock();
 176
 177	proc_flush_task(p);
 178
 179	write_lock_irq(&tasklist_lock);
 180	ptrace_release_task(p);
 
 181	__exit_signal(p);
 182
 183	/*
 184	 * If we are the last non-leader member of the thread
 185	 * group, and the leader is zombie, then notify the
 186	 * group leader's parent process. (if it wants notification.)
 187	 */
 188	zap_leader = 0;
 189	leader = p->group_leader;
 190	if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
 
 191		/*
 192		 * If we were the last child thread and the leader has
 193		 * exited already, and the leader's parent ignores SIGCHLD,
 194		 * then we are the one who should release the leader.
 195		 */
 196		zap_leader = do_notify_parent(leader, leader->exit_signal);
 197		if (zap_leader)
 198			leader->exit_state = EXIT_DEAD;
 199	}
 200
 201	write_unlock_irq(&tasklist_lock);
 
 
 
 202	release_thread(p);
 203	call_rcu(&p->rcu, delayed_put_task_struct);
 204
 205	p = leader;
 206	if (unlikely(zap_leader))
 207		goto repeat;
 208}
 209
 210/*
 211 * This checks not only the pgrp, but falls back on the pid if no
 212 * satisfactory pgrp is found. I dunno - gdb doesn't work correctly
 213 * without this...
 214 *
 215 * The caller must hold rcu lock or the tasklist lock.
 216 */
 217struct pid *session_of_pgrp(struct pid *pgrp)
 218{
 219	struct task_struct *p;
 220	struct pid *sid = NULL;
 221
 222	p = pid_task(pgrp, PIDTYPE_PGID);
 223	if (p == NULL)
 224		p = pid_task(pgrp, PIDTYPE_PID);
 225	if (p != NULL)
 226		sid = task_session(p);
 227
 228	return sid;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 229}
 
 230
 231/*
 232 * Determine if a process group is "orphaned", according to the POSIX
 233 * definition in 2.2.2.52.  Orphaned process groups are not to be affected
 234 * by terminal-generated stop signals.  Newly orphaned process groups are
 235 * to receive a SIGHUP and a SIGCONT.
 236 *
 237 * "I ask you, have you ever known what it is to be an orphan?"
 238 */
 239static int will_become_orphaned_pgrp(struct pid *pgrp, struct task_struct *ignored_task)
 
 240{
 241	struct task_struct *p;
 242
 243	do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
 244		if ((p == ignored_task) ||
 245		    (p->exit_state && thread_group_empty(p)) ||
 246		    is_global_init(p->real_parent))
 247			continue;
 248
 249		if (task_pgrp(p->real_parent) != pgrp &&
 250		    task_session(p->real_parent) == task_session(p))
 251			return 0;
 252	} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
 253
 254	return 1;
 255}
 256
 257int is_current_pgrp_orphaned(void)
 258{
 259	int retval;
 260
 261	read_lock(&tasklist_lock);
 262	retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
 263	read_unlock(&tasklist_lock);
 264
 265	return retval;
 266}
 267
 268static bool has_stopped_jobs(struct pid *pgrp)
 269{
 270	struct task_struct *p;
 271
 272	do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
 273		if (p->signal->flags & SIGNAL_STOP_STOPPED)
 274			return true;
 275	} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
 276
 277	return false;
 278}
 279
 280/*
 281 * Check to see if any process groups have become orphaned as
 282 * a result of our exiting, and if they have any stopped jobs,
 283 * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
 284 */
 285static void
 286kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent)
 287{
 288	struct pid *pgrp = task_pgrp(tsk);
 289	struct task_struct *ignored_task = tsk;
 290
 291	if (!parent)
 292		 /* exit: our father is in a different pgrp than
 293		  * we are and we were the only connection outside.
 294		  */
 295		parent = tsk->real_parent;
 296	else
 297		/* reparent: our child is in a different pgrp than
 298		 * we are, and it was the only connection outside.
 299		 */
 300		ignored_task = NULL;
 301
 302	if (task_pgrp(parent) != pgrp &&
 303	    task_session(parent) == task_session(tsk) &&
 304	    will_become_orphaned_pgrp(pgrp, ignored_task) &&
 305	    has_stopped_jobs(pgrp)) {
 306		__kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
 307		__kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
 308	}
 309}
 310
 311/**
 312 * reparent_to_kthreadd - Reparent the calling kernel thread to kthreadd
 313 *
 314 * If a kernel thread is launched as a result of a system call, or if
 315 * it ever exits, it should generally reparent itself to kthreadd so it
 316 * isn't in the way of other processes and is correctly cleaned up on exit.
 317 *
 318 * The various task state such as scheduling policy and priority may have
 319 * been inherited from a user process, so we reset them to sane values here.
 320 *
 321 * NOTE that reparent_to_kthreadd() gives the caller full capabilities.
 322 */
 323static void reparent_to_kthreadd(void)
 324{
 325	write_lock_irq(&tasklist_lock);
 326
 327	ptrace_unlink(current);
 328	/* Reparent to init */
 329	current->real_parent = current->parent = kthreadd_task;
 330	list_move_tail(&current->sibling, &current->real_parent->children);
 331
 332	/* Set the exit signal to SIGCHLD so we signal init on exit */
 333	current->exit_signal = SIGCHLD;
 334
 335	if (task_nice(current) < 0)
 336		set_user_nice(current, 0);
 337	/* cpus_allowed? */
 338	/* rt_priority? */
 339	/* signals? */
 340	memcpy(current->signal->rlim, init_task.signal->rlim,
 341	       sizeof(current->signal->rlim));
 342
 343	atomic_inc(&init_cred.usage);
 344	commit_creds(&init_cred);
 345	write_unlock_irq(&tasklist_lock);
 346}
 347
 348void __set_special_pids(struct pid *pid)
 349{
 350	struct task_struct *curr = current->group_leader;
 351
 352	if (task_session(curr) != pid)
 353		change_pid(curr, PIDTYPE_SID, pid);
 354
 355	if (task_pgrp(curr) != pid)
 356		change_pid(curr, PIDTYPE_PGID, pid);
 357}
 358
 359static void set_special_pids(struct pid *pid)
 360{
 361	write_lock_irq(&tasklist_lock);
 362	__set_special_pids(pid);
 363	write_unlock_irq(&tasklist_lock);
 364}
 365
 366/*
 367 * Let kernel threads use this to say that they allow a certain signal.
 368 * Must not be used if kthread was cloned with CLONE_SIGHAND.
 369 */
 370int allow_signal(int sig)
 371{
 372	if (!valid_signal(sig) || sig < 1)
 373		return -EINVAL;
 374
 375	spin_lock_irq(&current->sighand->siglock);
 376	/* This is only needed for daemonize()'ed kthreads */
 377	sigdelset(&current->blocked, sig);
 378	/*
 379	 * Kernel threads handle their own signals. Let the signal code
 380	 * know it'll be handled, so that they don't get converted to
 381	 * SIGKILL or just silently dropped.
 382	 */
 383	current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2;
 384	recalc_sigpending();
 385	spin_unlock_irq(&current->sighand->siglock);
 386	return 0;
 387}
 388
 389EXPORT_SYMBOL(allow_signal);
 390
 391int disallow_signal(int sig)
 392{
 393	if (!valid_signal(sig) || sig < 1)
 394		return -EINVAL;
 395
 396	spin_lock_irq(&current->sighand->siglock);
 397	current->sighand->action[(sig)-1].sa.sa_handler = SIG_IGN;
 398	recalc_sigpending();
 399	spin_unlock_irq(&current->sighand->siglock);
 400	return 0;
 401}
 402
 403EXPORT_SYMBOL(disallow_signal);
 404
 405/*
 406 *	Put all the gunge required to become a kernel thread without
 407 *	attached user resources in one place where it belongs.
 408 */
 409
 410void daemonize(const char *name, ...)
 411{
 412	va_list args;
 413	sigset_t blocked;
 414
 415	va_start(args, name);
 416	vsnprintf(current->comm, sizeof(current->comm), name, args);
 417	va_end(args);
 418
 419	/*
 420	 * If we were started as result of loading a module, close all of the
 421	 * user space pages.  We don't need them, and if we didn't close them
 422	 * they would be locked into memory.
 423	 */
 424	exit_mm(current);
 425	/*
 426	 * We don't want to have TIF_FREEZE set if the system-wide hibernation
 427	 * or suspend transition begins right now.
 428	 */
 429	current->flags |= (PF_NOFREEZE | PF_KTHREAD);
 430
 431	if (current->nsproxy != &init_nsproxy) {
 432		get_nsproxy(&init_nsproxy);
 433		switch_task_namespaces(current, &init_nsproxy);
 434	}
 435	set_special_pids(&init_struct_pid);
 436	proc_clear_tty(current);
 437
 438	/* Block and flush all signals */
 439	sigfillset(&blocked);
 440	sigprocmask(SIG_BLOCK, &blocked, NULL);
 441	flush_signals(current);
 442
 443	/* Become as one with the init task */
 444
 445	daemonize_fs_struct();
 446	exit_files(current);
 447	current->files = init_task.files;
 448	atomic_inc(&current->files->count);
 449
 450	reparent_to_kthreadd();
 451}
 452
 453EXPORT_SYMBOL(daemonize);
 454
 455static void close_files(struct files_struct * files)
 456{
 457	int i, j;
 458	struct fdtable *fdt;
 459
 460	j = 0;
 461
 462	/*
 463	 * It is safe to dereference the fd table without RCU or
 464	 * ->file_lock because this is the last reference to the
 465	 * files structure.  But use RCU to shut RCU-lockdep up.
 466	 */
 467	rcu_read_lock();
 468	fdt = files_fdtable(files);
 469	rcu_read_unlock();
 470	for (;;) {
 471		unsigned long set;
 472		i = j * __NFDBITS;
 473		if (i >= fdt->max_fds)
 474			break;
 475		set = fdt->open_fds->fds_bits[j++];
 476		while (set) {
 477			if (set & 1) {
 478				struct file * file = xchg(&fdt->fd[i], NULL);
 479				if (file) {
 480					filp_close(file, files);
 481					cond_resched();
 482				}
 483			}
 484			i++;
 485			set >>= 1;
 486		}
 487	}
 488}
 489
 490struct files_struct *get_files_struct(struct task_struct *task)
 491{
 492	struct files_struct *files;
 493
 494	task_lock(task);
 495	files = task->files;
 496	if (files)
 497		atomic_inc(&files->count);
 498	task_unlock(task);
 499
 500	return files;
 501}
 502
 503void put_files_struct(struct files_struct *files)
 504{
 505	struct fdtable *fdt;
 506
 507	if (atomic_dec_and_test(&files->count)) {
 508		close_files(files);
 509		/*
 510		 * Free the fd and fdset arrays if we expanded them.
 511		 * If the fdtable was embedded, pass files for freeing
 512		 * at the end of the RCU grace period. Otherwise,
 513		 * you can free files immediately.
 514		 */
 515		rcu_read_lock();
 516		fdt = files_fdtable(files);
 517		if (fdt != &files->fdtab)
 518			kmem_cache_free(files_cachep, files);
 519		free_fdtable(fdt);
 520		rcu_read_unlock();
 521	}
 522}
 523
 524void reset_files_struct(struct files_struct *files)
 525{
 526	struct task_struct *tsk = current;
 527	struct files_struct *old;
 528
 529	old = tsk->files;
 530	task_lock(tsk);
 531	tsk->files = files;
 532	task_unlock(tsk);
 533	put_files_struct(old);
 534}
 535
 536void exit_files(struct task_struct *tsk)
 537{
 538	struct files_struct * files = tsk->files;
 539
 540	if (files) {
 541		task_lock(tsk);
 542		tsk->files = NULL;
 543		task_unlock(tsk);
 544		put_files_struct(files);
 545	}
 546}
 547
 548#ifdef CONFIG_MM_OWNER
 549/*
 550 * A task is exiting.   If it owned this mm, find a new owner for the mm.
 551 */
 552void mm_update_next_owner(struct mm_struct *mm)
 553{
 554	struct task_struct *c, *g, *p = current;
 555
 556retry:
 557	/*
 558	 * If the exiting or execing task is not the owner, it's
 559	 * someone else's problem.
 560	 */
 561	if (mm->owner != p)
 562		return;
 563	/*
 564	 * The current owner is exiting/execing and there are no other
 565	 * candidates.  Do not leave the mm pointing to a possibly
 566	 * freed task structure.
 567	 */
 568	if (atomic_read(&mm->mm_users) <= 1) {
 569		mm->owner = NULL;
 570		return;
 571	}
 572
 573	read_lock(&tasklist_lock);
 574	/*
 575	 * Search in the children
 576	 */
 577	list_for_each_entry(c, &p->children, sibling) {
 578		if (c->mm == mm)
 579			goto assign_new_owner;
 580	}
 581
 582	/*
 583	 * Search in the siblings
 584	 */
 585	list_for_each_entry(c, &p->real_parent->children, sibling) {
 586		if (c->mm == mm)
 587			goto assign_new_owner;
 588	}
 589
 590	/*
 591	 * Search through everything else. We should not get
 592	 * here often
 593	 */
 594	do_each_thread(g, c) {
 595		if (c->mm == mm)
 596			goto assign_new_owner;
 597	} while_each_thread(g, c);
 598
 
 
 
 
 
 599	read_unlock(&tasklist_lock);
 600	/*
 601	 * We found no owner yet mm_users > 1: this implies that we are
 602	 * most likely racing with swapoff (try_to_unuse()) or /proc or
 603	 * ptrace or page migration (get_task_mm()).  Mark owner as NULL.
 604	 */
 605	mm->owner = NULL;
 606	return;
 607
 608assign_new_owner:
 609	BUG_ON(c == p);
 610	get_task_struct(c);
 611	/*
 612	 * The task_lock protects c->mm from changing.
 613	 * We always want mm->owner->mm == mm
 614	 */
 615	task_lock(c);
 616	/*
 617	 * Delay read_unlock() till we have the task_lock()
 618	 * to ensure that c does not slip away underneath us
 619	 */
 620	read_unlock(&tasklist_lock);
 621	if (c->mm != mm) {
 622		task_unlock(c);
 623		put_task_struct(c);
 624		goto retry;
 625	}
 626	mm->owner = c;
 627	task_unlock(c);
 628	put_task_struct(c);
 629}
 630#endif /* CONFIG_MM_OWNER */
 631
 632/*
 633 * Turn us into a lazy TLB process if we
 634 * aren't already..
 635 */
 636static void exit_mm(struct task_struct * tsk)
 637{
 638	struct mm_struct *mm = tsk->mm;
 639	struct core_state *core_state;
 640
 641	mm_release(tsk, mm);
 642	if (!mm)
 643		return;
 
 644	/*
 645	 * Serialize with any possible pending coredump.
 646	 * We must hold mmap_sem around checking core_state
 647	 * and clearing tsk->mm.  The core-inducing thread
 648	 * will increment ->nr_threads for each thread in the
 649	 * group with ->mm != NULL.
 650	 */
 651	down_read(&mm->mmap_sem);
 652	core_state = mm->core_state;
 653	if (core_state) {
 654		struct core_thread self;
 655		up_read(&mm->mmap_sem);
 656
 657		self.task = tsk;
 
 
 658		self.next = xchg(&core_state->dumper.next, &self);
 659		/*
 660		 * Implies mb(), the result of xchg() must be visible
 661		 * to core_state->dumper.
 662		 */
 663		if (atomic_dec_and_test(&core_state->nr_threads))
 664			complete(&core_state->startup);
 665
 666		for (;;) {
 667			set_task_state(tsk, TASK_UNINTERRUPTIBLE);
 668			if (!self.task) /* see coredump_finish() */
 669				break;
 670			schedule();
 671		}
 672		__set_task_state(tsk, TASK_RUNNING);
 673		down_read(&mm->mmap_sem);
 674	}
 675	atomic_inc(&mm->mm_count);
 676	BUG_ON(mm != tsk->active_mm);
 677	/* more a memory barrier than a real lock */
 678	task_lock(tsk);
 679	tsk->mm = NULL;
 680	up_read(&mm->mmap_sem);
 681	enter_lazy_tlb(mm, current);
 682	/* We don't want this task to be frozen prematurely */
 683	clear_freeze_flag(tsk);
 684	if (tsk->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
 685		atomic_dec(&mm->oom_disable_count);
 686	task_unlock(tsk);
 687	mm_update_next_owner(mm);
 688	mmput(mm);
 
 
 689}
 690
 691/*
 692 * When we die, we re-parent all our children.
 693 * Try to give them to another thread in our thread
 694 * group, and if no such member exists, give it to
 695 * the child reaper process (ie "init") in our pid
 696 * space.
 697 */
 698static struct task_struct *find_new_reaper(struct task_struct *father)
 
 
 
 
 
 699	__releases(&tasklist_lock)
 700	__acquires(&tasklist_lock)
 701{
 702	struct pid_namespace *pid_ns = task_active_pid_ns(father);
 703	struct task_struct *thread;
 
 704
 705	thread = father;
 706	while_each_thread(father, thread) {
 707		if (thread->flags & PF_EXITING)
 708			continue;
 709		if (unlikely(pid_ns->child_reaper == father))
 710			pid_ns->child_reaper = thread;
 711		return thread;
 712	}
 713
 714	if (unlikely(pid_ns->child_reaper == father)) {
 715		write_unlock_irq(&tasklist_lock);
 716		if (unlikely(pid_ns == &init_pid_ns))
 717			panic("Attempted to kill init!");
 718
 719		zap_pid_ns_processes(pid_ns);
 720		write_lock_irq(&tasklist_lock);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 721		/*
 722		 * We can not clear ->child_reaper or leave it alone.
 723		 * There may by stealth EXIT_DEAD tasks on ->children,
 724		 * forget_original_parent() must move them somewhere.
 
 
 
 725		 */
 726		pid_ns->child_reaper = init_pid_ns.child_reaper;
 
 
 
 
 
 
 
 
 
 
 727	}
 728
 729	return pid_ns->child_reaper;
 730}
 731
 732/*
 733* Any that need to be release_task'd are put on the @dead list.
 734 */
 735static void reparent_leader(struct task_struct *father, struct task_struct *p,
 736				struct list_head *dead)
 737{
 738	list_move_tail(&p->sibling, &p->real_parent->children);
 739
 740	if (p->exit_state == EXIT_DEAD)
 741		return;
 742	/*
 743	 * If this is a threaded reparent there is no need to
 744	 * notify anyone anything has happened.
 745	 */
 746	if (same_thread_group(p->real_parent, father))
 747		return;
 748
 749	/* We don't want people slaying init.  */
 750	p->exit_signal = SIGCHLD;
 751
 752	/* If it has exited notify the new parent about this child's death. */
 753	if (!p->ptrace &&
 754	    p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
 755		if (do_notify_parent(p, p->exit_signal)) {
 756			p->exit_state = EXIT_DEAD;
 757			list_move_tail(&p->sibling, dead);
 758		}
 759	}
 760
 761	kill_orphaned_pgrp(p, father);
 762}
 763
 764static void forget_original_parent(struct task_struct *father)
 765{
 766	struct task_struct *p, *n, *reaper;
 767	LIST_HEAD(dead_children);
 768
 769	write_lock_irq(&tasklist_lock);
 770	/*
 771	 * Note that exit_ptrace() and find_new_reaper() might
 772	 * drop tasklist_lock and reacquire it.
 773	 */
 774	exit_ptrace(father);
 775	reaper = find_new_reaper(father);
 
 
 
 
 
 
 
 
 776
 777	list_for_each_entry_safe(p, n, &father->children, sibling) {
 778		struct task_struct *t = p;
 779		do {
 780			t->real_parent = reaper;
 781			if (t->parent == father) {
 782				BUG_ON(t->ptrace);
 783				t->parent = t->real_parent;
 784			}
 785			if (t->pdeath_signal)
 786				group_send_sig_info(t->pdeath_signal,
 787						    SEND_SIG_NOINFO, t);
 788		} while_each_thread(p, t);
 789		reparent_leader(father, p, &dead_children);
 790	}
 791	write_unlock_irq(&tasklist_lock);
 792
 793	BUG_ON(!list_empty(&father->children));
 794
 795	list_for_each_entry_safe(p, n, &dead_children, sibling) {
 796		list_del_init(&p->sibling);
 797		release_task(p);
 798	}
 
 799}
 800
 801/*
 802 * Send signals to all our closest relatives so that they know
 803 * to properly mourn us..
 804 */
 805static void exit_notify(struct task_struct *tsk, int group_dead)
 806{
 807	bool autoreap;
 808
 809	/*
 810	 * This does two things:
 811	 *
 812  	 * A.  Make init inherit all the child processes
 813	 * B.  Check to see if any process groups have become orphaned
 814	 *	as a result of our exiting, and if they have any stopped
 815	 *	jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
 816	 */
 817	forget_original_parent(tsk);
 818	exit_task_namespaces(tsk);
 819
 820	write_lock_irq(&tasklist_lock);
 
 
 821	if (group_dead)
 822		kill_orphaned_pgrp(tsk->group_leader, NULL);
 823
 824	/* Let father know we died
 825	 *
 826	 * Thread signals are configurable, but you aren't going to use
 827	 * that to send signals to arbitrary processes.
 828	 * That stops right now.
 829	 *
 830	 * If the parent exec id doesn't match the exec id we saved
 831	 * when we started then we know the parent has changed security
 832	 * domain.
 833	 *
 834	 * If our self_exec id doesn't match our parent_exec_id then
 835	 * we have changed execution domain as these two values started
 836	 * the same after a fork.
 837	 */
 838	if (thread_group_leader(tsk) && tsk->exit_signal != SIGCHLD &&
 839	    (tsk->parent_exec_id != tsk->real_parent->self_exec_id ||
 840	     tsk->self_exec_id != tsk->parent_exec_id))
 841		tsk->exit_signal = SIGCHLD;
 842
 843	if (unlikely(tsk->ptrace)) {
 844		int sig = thread_group_leader(tsk) &&
 845				thread_group_empty(tsk) &&
 846				!ptrace_reparented(tsk) ?
 847			tsk->exit_signal : SIGCHLD;
 848		autoreap = do_notify_parent(tsk, sig);
 849	} else if (thread_group_leader(tsk)) {
 850		autoreap = thread_group_empty(tsk) &&
 851			do_notify_parent(tsk, tsk->exit_signal);
 852	} else {
 853		autoreap = true;
 854	}
 855
 856	tsk->exit_state = autoreap ? EXIT_DEAD : EXIT_ZOMBIE;
 
 
 
 857
 858	/* mt-exec, de_thread() is waiting for group leader */
 859	if (unlikely(tsk->signal->notify_count < 0))
 860		wake_up_process(tsk->signal->group_exit_task);
 861	write_unlock_irq(&tasklist_lock);
 862
 863	/* If the process is dead, release it - nobody will wait for it */
 864	if (autoreap)
 865		release_task(tsk);
 
 866}
 867
 868#ifdef CONFIG_DEBUG_STACK_USAGE
 869static void check_stack_usage(void)
 870{
 871	static DEFINE_SPINLOCK(low_water_lock);
 872	static int lowest_to_date = THREAD_SIZE;
 873	unsigned long free;
 874
 875	free = stack_not_used(current);
 876
 877	if (free >= lowest_to_date)
 878		return;
 879
 880	spin_lock(&low_water_lock);
 881	if (free < lowest_to_date) {
 882		printk(KERN_WARNING "%s used greatest stack depth: %lu bytes "
 883				"left\n",
 884				current->comm, free);
 885		lowest_to_date = free;
 886	}
 887	spin_unlock(&low_water_lock);
 888}
 889#else
 890static inline void check_stack_usage(void) {}
 891#endif
 892
 893NORET_TYPE void do_exit(long code)
 894{
 895	struct task_struct *tsk = current;
 896	int group_dead;
 897
 898	profile_task_exit(tsk);
 
 
 
 
 
 899
 900	WARN_ON(blk_needs_flush_plug(tsk));
 901
 902	if (unlikely(in_interrupt()))
 903		panic("Aiee, killing interrupt handler!");
 904	if (unlikely(!tsk->pid))
 905		panic("Attempted to kill the idle task!");
 906
 907	/*
 908	 * If do_exit is called because this processes oopsed, it's possible
 909	 * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before
 910	 * continuing. Amongst other possible reasons, this is to prevent
 911	 * mm_release()->clear_child_tid() from writing to a user-controlled
 912	 * kernel address.
 913	 */
 914	set_fs(USER_DS);
 
 
 
 
 
 
 
 
 
 
 915
 916	ptrace_event(PTRACE_EVENT_EXIT, code);
 917
 918	validate_creds_for_do_exit(tsk);
 919
 920	/*
 921	 * We're taking recursive faults here in do_exit. Safest is to just
 922	 * leave this task alone and wait for reboot.
 923	 */
 924	if (unlikely(tsk->flags & PF_EXITING)) {
 925		printk(KERN_ALERT
 926			"Fixing recursive fault but reboot is needed!\n");
 927		/*
 928		 * We can do this unlocked here. The futex code uses
 929		 * this flag just to verify whether the pi state
 930		 * cleanup has been done or not. In the worst case it
 931		 * loops once more. We pretend that the cleanup was
 932		 * done as there is no way to return. Either the
 933		 * OWNER_DIED bit is set by now or we push the blocked
 934		 * task into the wait for ever nirwana as well.
 935		 */
 936		tsk->flags |= PF_EXITPIDONE;
 937		set_current_state(TASK_UNINTERRUPTIBLE);
 938		schedule();
 939	}
 940
 941	exit_irq_thread();
 942
 943	exit_signals(tsk);  /* sets PF_EXITING */
 944	/*
 945	 * tsk->flags are checked in the futex code to protect against
 946	 * an exiting task cleaning up the robust pi futexes.
 947	 */
 948	smp_mb();
 949	raw_spin_unlock_wait(&tsk->pi_lock);
 950
 951	if (unlikely(in_atomic()))
 952		printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
 953				current->comm, task_pid_nr(current),
 954				preempt_count());
 955
 956	acct_update_integrals(tsk);
 957	/* sync mm's RSS info before statistics gathering */
 958	if (tsk->mm)
 959		sync_mm_rss(tsk, tsk->mm);
 
 960	group_dead = atomic_dec_and_test(&tsk->signal->live);
 961	if (group_dead) {
 
 
 
 
 
 
 
 
 
 962		hrtimer_cancel(&tsk->signal->real_timer);
 963		exit_itimers(tsk->signal);
 
 964		if (tsk->mm)
 965			setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm);
 966	}
 967	acct_collect(code, group_dead);
 968	if (group_dead)
 969		tty_audit_exit();
 970	if (unlikely(tsk->audit_context))
 971		audit_free(tsk);
 972
 973	tsk->exit_code = code;
 974	taskstats_exit(tsk, group_dead);
 975
 976	exit_mm(tsk);
 977
 978	if (group_dead)
 979		acct_process();
 980	trace_sched_process_exit(tsk);
 981
 982	exit_sem(tsk);
 983	exit_shm(tsk);
 984	exit_files(tsk);
 985	exit_fs(tsk);
 986	check_stack_usage();
 987	exit_thread();
 
 
 
 988
 989	/*
 990	 * Flush inherited counters to the parent - before the parent
 991	 * gets woken up by child-exit notifications.
 992	 *
 993	 * because of cgroup mode, must be called before cgroup_exit()
 994	 */
 995	perf_event_exit_task(tsk);
 996
 997	cgroup_exit(tsk, 1);
 998
 999	if (group_dead)
1000		disassociate_ctty(1);
1001
1002	module_put(task_thread_info(tsk)->exec_domain->module);
1003
1004	proc_exit_connector(tsk);
1005
1006	/*
1007	 * FIXME: do that only when needed, using sched_exit tracepoint
1008	 */
1009	ptrace_put_breakpoints(tsk);
1010
 
1011	exit_notify(tsk, group_dead);
1012#ifdef CONFIG_NUMA
1013	task_lock(tsk);
1014	mpol_put(tsk->mempolicy);
1015	tsk->mempolicy = NULL;
1016	task_unlock(tsk);
1017#endif
1018#ifdef CONFIG_FUTEX
1019	if (unlikely(current->pi_state_cache))
1020		kfree(current->pi_state_cache);
1021#endif
1022	/*
1023	 * Make sure we are holding no locks:
1024	 */
1025	debug_check_no_locks_held(tsk);
1026	/*
1027	 * We can do this unlocked here. The futex code uses this flag
1028	 * just to verify whether the pi state cleanup has been done
1029	 * or not. In the worst case it loops once more.
1030	 */
1031	tsk->flags |= PF_EXITPIDONE;
1032
1033	if (tsk->io_context)
1034		exit_io_context(tsk);
1035
1036	if (tsk->splice_pipe)
1037		__free_pipe_info(tsk->splice_pipe);
 
 
 
1038
1039	validate_creds_for_do_exit(tsk);
1040
 
1041	preempt_disable();
 
 
1042	exit_rcu();
1043	/* causes final put_task_struct in finish_task_switch(). */
1044	tsk->state = TASK_DEAD;
1045	schedule();
1046	BUG();
1047	/* Avoid "noreturn function does return".  */
1048	for (;;)
1049		cpu_relax();	/* For when BUG is null */
1050}
1051
 
 
 
1052EXPORT_SYMBOL_GPL(do_exit);
1053
1054NORET_TYPE void complete_and_exit(struct completion *comp, long code)
1055{
1056	if (comp)
1057		complete(comp);
1058
1059	do_exit(code);
1060}
1061
1062EXPORT_SYMBOL(complete_and_exit);
1063
1064SYSCALL_DEFINE1(exit, int, error_code)
1065{
1066	do_exit((error_code&0xff)<<8);
1067}
1068
1069/*
1070 * Take down every thread in the group.  This is called by fatal signals
1071 * as well as by sys_exit_group (below).
1072 */
1073NORET_TYPE void
1074do_group_exit(int exit_code)
1075{
1076	struct signal_struct *sig = current->signal;
1077
1078	BUG_ON(exit_code & 0x80); /* core dumps don't get here */
1079
1080	if (signal_group_exit(sig))
1081		exit_code = sig->group_exit_code;
1082	else if (!thread_group_empty(current)) {
1083		struct sighand_struct *const sighand = current->sighand;
 
1084		spin_lock_irq(&sighand->siglock);
1085		if (signal_group_exit(sig))
1086			/* Another thread got here before we took the lock.  */
1087			exit_code = sig->group_exit_code;
1088		else {
1089			sig->group_exit_code = exit_code;
1090			sig->flags = SIGNAL_GROUP_EXIT;
1091			zap_other_threads(current);
1092		}
1093		spin_unlock_irq(&sighand->siglock);
1094	}
1095
1096	do_exit(exit_code);
1097	/* NOTREACHED */
1098}
1099
1100/*
1101 * this kills every thread in the thread group. Note that any externally
1102 * wait4()-ing process will get the correct exit code - even if this
1103 * thread is not the thread group leader.
1104 */
1105SYSCALL_DEFINE1(exit_group, int, error_code)
1106{
1107	do_group_exit((error_code & 0xff) << 8);
1108	/* NOTREACHED */
1109	return 0;
1110}
1111
 
 
 
 
 
 
 
1112struct wait_opts {
1113	enum pid_type		wo_type;
1114	int			wo_flags;
1115	struct pid		*wo_pid;
1116
1117	struct siginfo __user	*wo_info;
1118	int __user		*wo_stat;
1119	struct rusage __user	*wo_rusage;
1120
1121	wait_queue_t		child_wait;
1122	int			notask_error;
1123};
1124
1125static inline
1126struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
1127{
1128	if (type != PIDTYPE_PID)
1129		task = task->group_leader;
1130	return task->pids[type].pid;
1131}
1132
1133static int eligible_pid(struct wait_opts *wo, struct task_struct *p)
1134{
1135	return	wo->wo_type == PIDTYPE_MAX ||
1136		task_pid_type(p, wo->wo_type) == wo->wo_pid;
1137}
1138
1139static int eligible_child(struct wait_opts *wo, struct task_struct *p)
 
1140{
1141	if (!eligible_pid(wo, p))
1142		return 0;
1143	/* Wait for all children (clone and not) if __WALL is set;
1144	 * otherwise, wait for clone children *only* if __WCLONE is
1145	 * set; otherwise, wait for non-clone children *only*.  (Note:
1146	 * A "clone" child here is one that reports to its parent
1147	 * using a signal other than SIGCHLD.) */
1148	if (((p->exit_signal != SIGCHLD) ^ !!(wo->wo_flags & __WCLONE))
1149	    && !(wo->wo_flags & __WALL))
1150		return 0;
1151
1152	return 1;
1153}
 
 
 
 
1154
1155static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
1156				pid_t pid, uid_t uid, int why, int status)
1157{
1158	struct siginfo __user *infop;
1159	int retval = wo->wo_rusage
1160		? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
 
 
 
 
1161
1162	put_task_struct(p);
1163	infop = wo->wo_info;
1164	if (infop) {
1165		if (!retval)
1166			retval = put_user(SIGCHLD, &infop->si_signo);
1167		if (!retval)
1168			retval = put_user(0, &infop->si_errno);
1169		if (!retval)
1170			retval = put_user((short)why, &infop->si_code);
1171		if (!retval)
1172			retval = put_user(pid, &infop->si_pid);
1173		if (!retval)
1174			retval = put_user(uid, &infop->si_uid);
1175		if (!retval)
1176			retval = put_user(status, &infop->si_status);
1177	}
1178	if (!retval)
1179		retval = pid;
1180	return retval;
1181}
1182
1183/*
1184 * Handle sys_wait4 work for one task in state EXIT_ZOMBIE.  We hold
1185 * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1186 * the lock and this task is uninteresting.  If we return nonzero, we have
1187 * released the lock and the system call should return.
1188 */
1189static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
1190{
1191	unsigned long state;
1192	int retval, status, traced;
1193	pid_t pid = task_pid_vnr(p);
1194	uid_t uid = __task_cred(p)->uid;
1195	struct siginfo __user *infop;
1196
1197	if (!likely(wo->wo_flags & WEXITED))
1198		return 0;
1199
1200	if (unlikely(wo->wo_flags & WNOWAIT)) {
1201		int exit_code = p->exit_code;
1202		int why;
1203
1204		get_task_struct(p);
1205		read_unlock(&tasklist_lock);
1206		if ((exit_code & 0x7f) == 0) {
1207			why = CLD_EXITED;
1208			status = exit_code >> 8;
1209		} else {
1210			why = (exit_code & 0x80) ? CLD_DUMPED : CLD_KILLED;
1211			status = exit_code & 0x7f;
1212		}
1213		return wait_noreap_copyout(wo, p, pid, uid, why, status);
1214	}
1215
1216	/*
1217	 * Try to move the task's state to DEAD
1218	 * only one thread is allowed to do this:
1219	 */
1220	state = xchg(&p->exit_state, EXIT_DEAD);
1221	if (state != EXIT_ZOMBIE) {
1222		BUG_ON(state != EXIT_DEAD);
1223		return 0;
1224	}
 
 
 
 
1225
1226	traced = ptrace_reparented(p);
1227	/*
1228	 * It can be ptraced but not reparented, check
1229	 * thread_group_leader() to filter out sub-threads.
1230	 */
1231	if (likely(!traced) && thread_group_leader(p)) {
1232		struct signal_struct *psig;
1233		struct signal_struct *sig;
1234		unsigned long maxrss;
1235		cputime_t tgutime, tgstime;
1236
1237		/*
1238		 * The resource counters for the group leader are in its
1239		 * own task_struct.  Those for dead threads in the group
1240		 * are in its signal_struct, as are those for the child
1241		 * processes it has previously reaped.  All these
1242		 * accumulate in the parent's signal_struct c* fields.
1243		 *
1244		 * We don't bother to take a lock here to protect these
1245		 * p->signal fields, because they are only touched by
1246		 * __exit_signal, which runs with tasklist_lock
1247		 * write-locked anyway, and so is excluded here.  We do
1248		 * need to protect the access to parent->signal fields,
1249		 * as other threads in the parent group can be right
1250		 * here reaping other children at the same time.
 
1251		 *
1252		 * We use thread_group_times() to get times for the thread
1253		 * group, which consolidates times for all threads in the
1254		 * group including the group leader.
1255		 */
1256		thread_group_times(p, &tgutime, &tgstime);
1257		spin_lock_irq(&p->real_parent->sighand->siglock);
1258		psig = p->real_parent->signal;
1259		sig = p->signal;
1260		psig->cutime =
1261			cputime_add(psig->cutime,
1262			cputime_add(tgutime,
1263				    sig->cutime));
1264		psig->cstime =
1265			cputime_add(psig->cstime,
1266			cputime_add(tgstime,
1267				    sig->cstime));
1268		psig->cgtime =
1269			cputime_add(psig->cgtime,
1270			cputime_add(p->gtime,
1271			cputime_add(sig->gtime,
1272				    sig->cgtime)));
1273		psig->cmin_flt +=
1274			p->min_flt + sig->min_flt + sig->cmin_flt;
1275		psig->cmaj_flt +=
1276			p->maj_flt + sig->maj_flt + sig->cmaj_flt;
1277		psig->cnvcsw +=
1278			p->nvcsw + sig->nvcsw + sig->cnvcsw;
1279		psig->cnivcsw +=
1280			p->nivcsw + sig->nivcsw + sig->cnivcsw;
1281		psig->cinblock +=
1282			task_io_get_inblock(p) +
1283			sig->inblock + sig->cinblock;
1284		psig->coublock +=
1285			task_io_get_oublock(p) +
1286			sig->oublock + sig->coublock;
1287		maxrss = max(sig->maxrss, sig->cmaxrss);
1288		if (psig->cmaxrss < maxrss)
1289			psig->cmaxrss = maxrss;
1290		task_io_accounting_add(&psig->ioac, &p->ioac);
1291		task_io_accounting_add(&psig->ioac, &sig->ioac);
1292		spin_unlock_irq(&p->real_parent->sighand->siglock);
 
1293	}
1294
1295	/*
1296	 * Now we are sure this task is interesting, and no other
1297	 * thread can reap it because we set its state to EXIT_DEAD.
1298	 */
1299	read_unlock(&tasklist_lock);
1300
1301	retval = wo->wo_rusage
1302		? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1303	status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1304		? p->signal->group_exit_code : p->exit_code;
1305	if (!retval && wo->wo_stat)
1306		retval = put_user(status, wo->wo_stat);
1307
1308	infop = wo->wo_info;
1309	if (!retval && infop)
1310		retval = put_user(SIGCHLD, &infop->si_signo);
1311	if (!retval && infop)
1312		retval = put_user(0, &infop->si_errno);
1313	if (!retval && infop) {
1314		int why;
1315
1316		if ((status & 0x7f) == 0) {
1317			why = CLD_EXITED;
1318			status >>= 8;
1319		} else {
1320			why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
1321			status &= 0x7f;
1322		}
1323		retval = put_user((short)why, &infop->si_code);
1324		if (!retval)
1325			retval = put_user(status, &infop->si_status);
1326	}
1327	if (!retval && infop)
1328		retval = put_user(pid, &infop->si_pid);
1329	if (!retval && infop)
1330		retval = put_user(uid, &infop->si_uid);
1331	if (!retval)
1332		retval = pid;
1333
1334	if (traced) {
1335		write_lock_irq(&tasklist_lock);
1336		/* We dropped tasklist, ptracer could die and untrace */
1337		ptrace_unlink(p);
1338		/*
1339		 * If this is not a sub-thread, notify the parent.
1340		 * If parent wants a zombie, don't release it now.
1341		 */
1342		if (thread_group_leader(p) &&
1343		    !do_notify_parent(p, p->exit_signal)) {
1344			p->exit_state = EXIT_ZOMBIE;
1345			p = NULL;
1346		}
1347		write_unlock_irq(&tasklist_lock);
1348	}
1349	if (p != NULL)
1350		release_task(p);
1351
1352	return retval;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1353}
1354
1355static int *task_stopped_code(struct task_struct *p, bool ptrace)
1356{
1357	if (ptrace) {
1358		if (task_is_stopped_or_traced(p) &&
1359		    !(p->jobctl & JOBCTL_LISTENING))
1360			return &p->exit_code;
1361	} else {
1362		if (p->signal->flags & SIGNAL_STOP_STOPPED)
1363			return &p->signal->group_exit_code;
1364	}
1365	return NULL;
1366}
1367
1368/**
1369 * wait_task_stopped - Wait for %TASK_STOPPED or %TASK_TRACED
1370 * @wo: wait options
1371 * @ptrace: is the wait for ptrace
1372 * @p: task to wait for
1373 *
1374 * Handle sys_wait4() work for %p in state %TASK_STOPPED or %TASK_TRACED.
1375 *
1376 * CONTEXT:
1377 * read_lock(&tasklist_lock), which is released if return value is
1378 * non-zero.  Also, grabs and releases @p->sighand->siglock.
1379 *
1380 * RETURNS:
1381 * 0 if wait condition didn't exist and search for other wait conditions
1382 * should continue.  Non-zero return, -errno on failure and @p's pid on
1383 * success, implies that tasklist_lock is released and wait condition
1384 * search should terminate.
1385 */
1386static int wait_task_stopped(struct wait_opts *wo,
1387				int ptrace, struct task_struct *p)
1388{
1389	struct siginfo __user *infop;
1390	int retval, exit_code, *p_code, why;
1391	uid_t uid = 0; /* unneeded, required by compiler */
1392	pid_t pid;
1393
1394	/*
1395	 * Traditionally we see ptrace'd stopped tasks regardless of options.
1396	 */
1397	if (!ptrace && !(wo->wo_flags & WUNTRACED))
1398		return 0;
1399
1400	if (!task_stopped_code(p, ptrace))
1401		return 0;
1402
1403	exit_code = 0;
1404	spin_lock_irq(&p->sighand->siglock);
1405
1406	p_code = task_stopped_code(p, ptrace);
1407	if (unlikely(!p_code))
1408		goto unlock_sig;
1409
1410	exit_code = *p_code;
1411	if (!exit_code)
1412		goto unlock_sig;
1413
1414	if (!unlikely(wo->wo_flags & WNOWAIT))
1415		*p_code = 0;
1416
1417	uid = task_uid(p);
1418unlock_sig:
1419	spin_unlock_irq(&p->sighand->siglock);
1420	if (!exit_code)
1421		return 0;
1422
1423	/*
1424	 * Now we are pretty sure this task is interesting.
1425	 * Make sure it doesn't get reaped out from under us while we
1426	 * give up the lock and then examine it below.  We don't want to
1427	 * keep holding onto the tasklist_lock while we call getrusage and
1428	 * possibly take page faults for user memory.
1429	 */
1430	get_task_struct(p);
1431	pid = task_pid_vnr(p);
1432	why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
1433	read_unlock(&tasklist_lock);
 
 
 
 
1434
1435	if (unlikely(wo->wo_flags & WNOWAIT))
1436		return wait_noreap_copyout(wo, p, pid, uid, why, exit_code);
1437
1438	retval = wo->wo_rusage
1439		? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1440	if (!retval && wo->wo_stat)
1441		retval = put_user((exit_code << 8) | 0x7f, wo->wo_stat);
1442
1443	infop = wo->wo_info;
1444	if (!retval && infop)
1445		retval = put_user(SIGCHLD, &infop->si_signo);
1446	if (!retval && infop)
1447		retval = put_user(0, &infop->si_errno);
1448	if (!retval && infop)
1449		retval = put_user((short)why, &infop->si_code);
1450	if (!retval && infop)
1451		retval = put_user(exit_code, &infop->si_status);
1452	if (!retval && infop)
1453		retval = put_user(pid, &infop->si_pid);
1454	if (!retval && infop)
1455		retval = put_user(uid, &infop->si_uid);
1456	if (!retval)
1457		retval = pid;
1458	put_task_struct(p);
1459
1460	BUG_ON(!retval);
1461	return retval;
1462}
1463
1464/*
1465 * Handle do_wait work for one task in a live, non-stopped state.
1466 * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1467 * the lock and this task is uninteresting.  If we return nonzero, we have
1468 * released the lock and the system call should return.
1469 */
1470static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
1471{
1472	int retval;
1473	pid_t pid;
1474	uid_t uid;
1475
1476	if (!unlikely(wo->wo_flags & WCONTINUED))
1477		return 0;
1478
1479	if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
1480		return 0;
1481
1482	spin_lock_irq(&p->sighand->siglock);
1483	/* Re-check with the lock held.  */
1484	if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
1485		spin_unlock_irq(&p->sighand->siglock);
1486		return 0;
1487	}
1488	if (!unlikely(wo->wo_flags & WNOWAIT))
1489		p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1490	uid = task_uid(p);
1491	spin_unlock_irq(&p->sighand->siglock);
1492
1493	pid = task_pid_vnr(p);
1494	get_task_struct(p);
1495	read_unlock(&tasklist_lock);
 
 
 
 
1496
1497	if (!wo->wo_info) {
1498		retval = wo->wo_rusage
1499			? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1500		put_task_struct(p);
1501		if (!retval && wo->wo_stat)
1502			retval = put_user(0xffff, wo->wo_stat);
1503		if (!retval)
1504			retval = pid;
1505	} else {
1506		retval = wait_noreap_copyout(wo, p, pid, uid,
1507					     CLD_CONTINUED, SIGCONT);
1508		BUG_ON(retval == 0);
 
1509	}
1510
1511	return retval;
1512}
1513
1514/*
1515 * Consider @p for a wait by @parent.
1516 *
1517 * -ECHILD should be in ->notask_error before the first call.
1518 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1519 * Returns zero if the search for a child should continue;
1520 * then ->notask_error is 0 if @p is an eligible child,
1521 * or another error from security_task_wait(), or still -ECHILD.
1522 */
1523static int wait_consider_task(struct wait_opts *wo, int ptrace,
1524				struct task_struct *p)
1525{
1526	int ret = eligible_child(wo, p);
 
 
 
 
 
 
 
 
 
 
 
1527	if (!ret)
1528		return ret;
1529
1530	ret = security_task_wait(p);
1531	if (unlikely(ret < 0)) {
1532		/*
1533		 * If we have not yet seen any eligible child,
1534		 * then let this error code replace -ECHILD.
1535		 * A permission error will give the user a clue
1536		 * to look for security policy problems, rather
1537		 * than for mysterious wait bugs.
1538		 */
1539		if (wo->notask_error)
1540			wo->notask_error = ret;
1541		return 0;
1542	}
1543
1544	/* dead body doesn't have much to contribute */
1545	if (p->exit_state == EXIT_DEAD)
1546		return 0;
1547
1548	/* slay zombie? */
1549	if (p->exit_state == EXIT_ZOMBIE) {
1550		/*
1551		 * A zombie ptracee is only visible to its ptracer.
1552		 * Notification and reaping will be cascaded to the real
1553		 * parent when the ptracer detaches.
 
 
 
 
 
 
1554		 */
1555		if (likely(!ptrace) && unlikely(p->ptrace)) {
1556			/* it will become visible, clear notask_error */
1557			wo->notask_error = 0;
1558			return 0;
1559		}
1560
 
 
1561		/* we don't reap group leaders with subthreads */
1562		if (!delay_group_leader(p))
1563			return wait_task_zombie(wo, p);
 
 
 
 
 
 
 
1564
1565		/*
1566		 * Allow access to stopped/continued state via zombie by
1567		 * falling through.  Clearing of notask_error is complex.
1568		 *
1569		 * When !@ptrace:
1570		 *
1571		 * If WEXITED is set, notask_error should naturally be
1572		 * cleared.  If not, subset of WSTOPPED|WCONTINUED is set,
1573		 * so, if there are live subthreads, there are events to
1574		 * wait for.  If all subthreads are dead, it's still safe
1575		 * to clear - this function will be called again in finite
1576		 * amount time once all the subthreads are released and
1577		 * will then return without clearing.
1578		 *
1579		 * When @ptrace:
1580		 *
1581		 * Stopped state is per-task and thus can't change once the
1582		 * target task dies.  Only continued and exited can happen.
1583		 * Clear notask_error if WCONTINUED | WEXITED.
1584		 */
1585		if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED)))
1586			wo->notask_error = 0;
1587	} else {
1588		/*
1589		 * If @p is ptraced by a task in its real parent's group,
1590		 * hide group stop/continued state when looking at @p as
1591		 * the real parent; otherwise, a single stop can be
1592		 * reported twice as group and ptrace stops.
1593		 *
1594		 * If a ptracer wants to distinguish the two events for its
1595		 * own children, it should create a separate process which
1596		 * takes the role of real parent.
1597		 */
1598		if (likely(!ptrace) && p->ptrace && !ptrace_reparented(p))
1599			return 0;
1600
1601		/*
1602		 * @p is alive and it's gonna stop, continue or exit, so
1603		 * there always is something to wait for.
1604		 */
1605		wo->notask_error = 0;
1606	}
1607
1608	/*
1609	 * Wait for stopped.  Depending on @ptrace, different stopped state
1610	 * is used and the two don't interact with each other.
1611	 */
1612	ret = wait_task_stopped(wo, ptrace, p);
1613	if (ret)
1614		return ret;
1615
1616	/*
1617	 * Wait for continued.  There's only one continued state and the
1618	 * ptracer can consume it which can confuse the real parent.  Don't
1619	 * use WCONTINUED from ptracer.  You don't need or want it.
1620	 */
1621	return wait_task_continued(wo, p);
1622}
1623
1624/*
1625 * Do the work of do_wait() for one thread in the group, @tsk.
1626 *
1627 * -ECHILD should be in ->notask_error before the first call.
1628 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1629 * Returns zero if the search for a child should continue; then
1630 * ->notask_error is 0 if there were any eligible children,
1631 * or another error from security_task_wait(), or still -ECHILD.
1632 */
1633static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk)
1634{
1635	struct task_struct *p;
1636
1637	list_for_each_entry(p, &tsk->children, sibling) {
1638		int ret = wait_consider_task(wo, 0, p);
 
1639		if (ret)
1640			return ret;
1641	}
1642
1643	return 0;
1644}
1645
1646static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk)
1647{
1648	struct task_struct *p;
1649
1650	list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
1651		int ret = wait_consider_task(wo, 1, p);
 
1652		if (ret)
1653			return ret;
1654	}
1655
1656	return 0;
1657}
1658
1659static int child_wait_callback(wait_queue_t *wait, unsigned mode,
1660				int sync, void *key)
1661{
1662	struct wait_opts *wo = container_of(wait, struct wait_opts,
1663						child_wait);
1664	struct task_struct *p = key;
1665
1666	if (!eligible_pid(wo, p))
1667		return 0;
1668
1669	if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent)
1670		return 0;
1671
1672	return default_wake_function(wait, mode, sync, key);
1673}
1674
1675void __wake_up_parent(struct task_struct *p, struct task_struct *parent)
1676{
1677	__wake_up_sync_key(&parent->signal->wait_chldexit,
1678				TASK_INTERRUPTIBLE, 1, p);
1679}
1680
1681static long do_wait(struct wait_opts *wo)
1682{
1683	struct task_struct *tsk;
1684	int retval;
1685
1686	trace_sched_process_wait(wo->wo_pid);
1687
1688	init_waitqueue_func_entry(&wo->child_wait, child_wait_callback);
1689	wo->child_wait.private = current;
1690	add_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1691repeat:
1692	/*
1693	 * If there is nothing that can match our critiera just get out.
1694	 * We will clear ->notask_error to zero if we see any child that
1695	 * might later match our criteria, even if we are not able to reap
1696	 * it yet.
1697	 */
1698	wo->notask_error = -ECHILD;
1699	if ((wo->wo_type < PIDTYPE_MAX) &&
1700	   (!wo->wo_pid || hlist_empty(&wo->wo_pid->tasks[wo->wo_type])))
1701		goto notask;
1702
1703	set_current_state(TASK_INTERRUPTIBLE);
1704	read_lock(&tasklist_lock);
1705	tsk = current;
1706	do {
1707		retval = do_wait_thread(wo, tsk);
1708		if (retval)
1709			goto end;
1710
1711		retval = ptrace_do_wait(wo, tsk);
1712		if (retval)
1713			goto end;
1714
1715		if (wo->wo_flags & __WNOTHREAD)
1716			break;
1717	} while_each_thread(current, tsk);
1718	read_unlock(&tasklist_lock);
1719
1720notask:
1721	retval = wo->notask_error;
1722	if (!retval && !(wo->wo_flags & WNOHANG)) {
1723		retval = -ERESTARTSYS;
1724		if (!signal_pending(current)) {
1725			schedule();
1726			goto repeat;
1727		}
1728	}
1729end:
1730	__set_current_state(TASK_RUNNING);
1731	remove_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1732	return retval;
1733}
1734
1735SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
1736		infop, int, options, struct rusage __user *, ru)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1737{
1738	struct wait_opts wo;
1739	struct pid *pid = NULL;
1740	enum pid_type type;
1741	long ret;
1742
1743	if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED))
 
1744		return -EINVAL;
1745	if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
1746		return -EINVAL;
1747
1748	switch (which) {
1749	case P_ALL:
1750		type = PIDTYPE_MAX;
1751		break;
1752	case P_PID:
1753		type = PIDTYPE_PID;
1754		if (upid <= 0)
1755			return -EINVAL;
 
 
1756		break;
1757	case P_PGID:
1758		type = PIDTYPE_PGID;
1759		if (upid <= 0)
 
 
 
 
 
 
 
 
 
 
1760			return -EINVAL;
 
 
 
 
1761		break;
1762	default:
1763		return -EINVAL;
1764	}
1765
1766	if (type < PIDTYPE_MAX)
1767		pid = find_get_pid(upid);
1768
1769	wo.wo_type	= type;
1770	wo.wo_pid	= pid;
1771	wo.wo_flags	= options;
1772	wo.wo_info	= infop;
1773	wo.wo_stat	= NULL;
1774	wo.wo_rusage	= ru;
1775	ret = do_wait(&wo);
1776
1777	if (ret > 0) {
1778		ret = 0;
1779	} else if (infop) {
1780		/*
1781		 * For a WNOHANG return, clear out all the fields
1782		 * we would set so the user can easily tell the
1783		 * difference.
1784		 */
1785		if (!ret)
1786			ret = put_user(0, &infop->si_signo);
1787		if (!ret)
1788			ret = put_user(0, &infop->si_errno);
1789		if (!ret)
1790			ret = put_user(0, &infop->si_code);
1791		if (!ret)
1792			ret = put_user(0, &infop->si_pid);
1793		if (!ret)
1794			ret = put_user(0, &infop->si_uid);
1795		if (!ret)
1796			ret = put_user(0, &infop->si_status);
1797	}
1798
1799	put_pid(pid);
1800
1801	/* avoid REGPARM breakage on x86: */
1802	asmlinkage_protect(5, ret, which, upid, infop, options, ru);
1803	return ret;
1804}
1805
1806SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
1807		int, options, struct rusage __user *, ru)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1808{
1809	struct wait_opts wo;
1810	struct pid *pid = NULL;
1811	enum pid_type type;
1812	long ret;
1813
1814	if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
1815			__WNOTHREAD|__WCLONE|__WALL))
1816		return -EINVAL;
1817
 
 
 
 
1818	if (upid == -1)
1819		type = PIDTYPE_MAX;
1820	else if (upid < 0) {
1821		type = PIDTYPE_PGID;
1822		pid = find_get_pid(-upid);
1823	} else if (upid == 0) {
1824		type = PIDTYPE_PGID;
1825		pid = get_task_pid(current, PIDTYPE_PGID);
1826	} else /* upid > 0 */ {
1827		type = PIDTYPE_PID;
1828		pid = find_get_pid(upid);
1829	}
1830
1831	wo.wo_type	= type;
1832	wo.wo_pid	= pid;
1833	wo.wo_flags	= options | WEXITED;
1834	wo.wo_info	= NULL;
1835	wo.wo_stat	= stat_addr;
1836	wo.wo_rusage	= ru;
1837	ret = do_wait(&wo);
1838	put_pid(pid);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1839
1840	/* avoid REGPARM breakage on x86: */
1841	asmlinkage_protect(4, ret, upid, stat_addr, options, ru);
 
 
1842	return ret;
1843}
1844
 
 
 
 
 
 
 
 
 
 
 
 
 
1845#ifdef __ARCH_WANT_SYS_WAITPID
1846
1847/*
1848 * sys_waitpid() remains for compatibility. waitpid() should be
1849 * implemented by calling sys_wait4() from libc.a.
1850 */
1851SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options)
1852{
1853	return sys_wait4(pid, stat_addr, options, NULL);
1854}
1855
1856#endif