linux/kernel/exit.c
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   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}
  78
  79/*
  80 * This function expects the tasklist_lock write-locked.
  81 */
  82static void __exit_signal(struct task_struct *tsk)
  83{
  84        struct signal_struct *sig = tsk->signal;
  85        bool group_dead = thread_group_leader(tsk);
  86        struct sighand_struct *sighand;
  87        struct tty_struct *uninitialized_var(tty);
  88        cputime_t utime, stime;
  89
  90        sighand = rcu_dereference_check(tsk->sighand,
  91                                        lockdep_tasklist_lock_is_held());
  92        spin_lock(&sighand->siglock);
  93
  94        posix_cpu_timers_exit(tsk);
  95        if (group_dead) {
  96                posix_cpu_timers_exit_group(tsk);
  97                tty = sig->tty;
  98                sig->tty = NULL;
  99        } else {
 100                /*
 101                 * This can only happen if the caller is de_thread().
 102                 * FIXME: this is the temporary hack, we should teach
 103                 * posix-cpu-timers to handle this case correctly.
 104                 */
 105                if (unlikely(has_group_leader_pid(tsk)))
 106                        posix_cpu_timers_exit_group(tsk);
 107
 108                /*
 109                 * If there is any task waiting for the group exit
 110                 * then notify it:
 111                 */
 112                if (sig->notify_count > 0 && !--sig->notify_count)
 113                        wake_up_process(sig->group_exit_task);
 114
 115                if (tsk == sig->curr_target)
 116                        sig->curr_target = next_thread(tsk);
 117                /*
 118                 * Accumulate here the counters for all threads but the
 119                 * group leader as they die, so they can be added into
 120                 * the process-wide totals when those are taken.
 121                 * The group leader stays around as a zombie as long
 122                 * as there are other threads.  When it gets reaped,
 123                 * the exit.c code will add its counts into these totals.
 124                 * We won't ever get here for the group leader, since it
 125                 * will have been the last reference on the signal_struct.
 126                 */
 127                task_cputime(tsk, &utime, &stime);
 128                sig->utime += utime;
 129                sig->stime += stime;
 130                sig->gtime += task_gtime(tsk);
 131                sig->min_flt += tsk->min_flt;
 132                sig->maj_flt += tsk->maj_flt;
 133                sig->nvcsw += tsk->nvcsw;
 134                sig->nivcsw += tsk->nivcsw;
 135                sig->inblock += task_io_get_inblock(tsk);
 136                sig->oublock += task_io_get_oublock(tsk);
 137                task_io_accounting_add(&sig->ioac, &tsk->ioac);
 138                sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
 139        }
 140
 141        sig->nr_threads--;
 142        __unhash_process(tsk, group_dead);
 143
 144        /*
 145         * Do this under ->siglock, we can race with another thread
 146         * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals.
 147         */
 148        flush_sigqueue(&tsk->pending);
 149        tsk->sighand = NULL;
 150        spin_unlock(&sighand->siglock);
 151
 152        __cleanup_sighand(sighand);
 153        clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
 154        if (group_dead) {
 155                flush_sigqueue(&sig->shared_pending);
 156                tty_kref_put(tty);
 157        }
 158}
 159
 160static void delayed_put_task_struct(struct rcu_head *rhp)
 161{
 162        struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
 163
 164        perf_event_delayed_put(tsk);
 165        trace_sched_process_free(tsk);
 166        put_task_struct(tsk);
 167}
 168
 169
 170void release_task(struct task_struct * p)
 171{
 172        struct task_struct *leader;
 173        int zap_leader;
 174repeat:
 175        /* don't need to get the RCU readlock here - the process is dead and
 176         * can't be modifying its own credentials. But shut RCU-lockdep up */
 177        rcu_read_lock();
 178        atomic_dec(&__task_cred(p)->user->processes);
 179        rcu_read_unlock();
 180
 181        proc_flush_task(p);
 182
 183        write_lock_irq(&tasklist_lock);
 184        ptrace_release_task(p);
 185        __exit_signal(p);
 186
 187        /*
 188         * If we are the last non-leader member of the thread
 189         * group, and the leader is zombie, then notify the
 190         * group leader's parent process. (if it wants notification.)
 191         */
 192        zap_leader = 0;
 193        leader = p->group_leader;
 194        if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
 195                /*
 196                 * If we were the last child thread and the leader has
 197                 * exited already, and the leader's parent ignores SIGCHLD,
 198                 * then we are the one who should release the leader.
 199                 */
 200                zap_leader = do_notify_parent(leader, leader->exit_signal);
 201                if (zap_leader)
 202                        leader->exit_state = EXIT_DEAD;
 203        }
 204
 205        write_unlock_irq(&tasklist_lock);
 206        release_thread(p);
 207        call_rcu(&p->rcu, delayed_put_task_struct);
 208
 209        p = leader;
 210        if (unlikely(zap_leader))
 211                goto repeat;
 212}
 213
 214/*
 215 * This checks not only the pgrp, but falls back on the pid if no
 216 * satisfactory pgrp is found. I dunno - gdb doesn't work correctly
 217 * without this...
 218 *
 219 * The caller must hold rcu lock or the tasklist lock.
 220 */
 221struct pid *session_of_pgrp(struct pid *pgrp)
 222{
 223        struct task_struct *p;
 224        struct pid *sid = NULL;
 225
 226        p = pid_task(pgrp, PIDTYPE_PGID);
 227        if (p == NULL)
 228                p = pid_task(pgrp, PIDTYPE_PID);
 229        if (p != NULL)
 230                sid = task_session(p);
 231
 232        return sid;
 233}
 234
 235/*
 236 * Determine if a process group is "orphaned", according to the POSIX
 237 * definition in 2.2.2.52.  Orphaned process groups are not to be affected
 238 * by terminal-generated stop signals.  Newly orphaned process groups are
 239 * to receive a SIGHUP and a SIGCONT.
 240 *
 241 * "I ask you, have you ever known what it is to be an orphan?"
 242 */
 243static int will_become_orphaned_pgrp(struct pid *pgrp, struct task_struct *ignored_task)
 244{
 245        struct task_struct *p;
 246
 247        do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
 248                if ((p == ignored_task) ||
 249                    (p->exit_state && thread_group_empty(p)) ||
 250                    is_global_init(p->real_parent))
 251                        continue;
 252
 253                if (task_pgrp(p->real_parent) != pgrp &&
 254                    task_session(p->real_parent) == task_session(p))
 255                        return 0;
 256        } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
 257
 258        return 1;
 259}
 260
 261int is_current_pgrp_orphaned(void)
 262{
 263        int retval;
 264
 265        read_lock(&tasklist_lock);
 266        retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
 267        read_unlock(&tasklist_lock);
 268
 269        return retval;
 270}
 271
 272static bool has_stopped_jobs(struct pid *pgrp)
 273{
 274        struct task_struct *p;
 275
 276        do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
 277                if (p->signal->flags & SIGNAL_STOP_STOPPED)
 278                        return true;
 279        } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
 280
 281        return false;
 282}
 283
 284/*
 285 * Check to see if any process groups have become orphaned as
 286 * a result of our exiting, and if they have any stopped jobs,
 287 * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
 288 */
 289static void
 290kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent)
 291{
 292        struct pid *pgrp = task_pgrp(tsk);
 293        struct task_struct *ignored_task = tsk;
 294
 295        if (!parent)
 296                 /* exit: our father is in a different pgrp than
 297                  * we are and we were the only connection outside.
 298                  */
 299                parent = tsk->real_parent;
 300        else
 301                /* reparent: our child is in a different pgrp than
 302                 * we are, and it was the only connection outside.
 303                 */
 304                ignored_task = NULL;
 305
 306        if (task_pgrp(parent) != pgrp &&
 307            task_session(parent) == task_session(tsk) &&
 308            will_become_orphaned_pgrp(pgrp, ignored_task) &&
 309            has_stopped_jobs(pgrp)) {
 310                __kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
 311                __kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
 312        }
 313}
 314
 315/*
 316 * Let kernel threads use this to say that they allow a certain signal.
 317 * Must not be used if kthread was cloned with CLONE_SIGHAND.
 318 */
 319int allow_signal(int sig)
 320{
 321        if (!valid_signal(sig) || sig < 1)
 322                return -EINVAL;
 323
 324        spin_lock_irq(&current->sighand->siglock);
 325        /* This is only needed for daemonize()'ed kthreads */
 326        sigdelset(&current->blocked, sig);
 327        /*
 328         * Kernel threads handle their own signals. Let the signal code
 329         * know it'll be handled, so that they don't get converted to
 330         * SIGKILL or just silently dropped.
 331         */
 332        current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2;
 333        recalc_sigpending();
 334        spin_unlock_irq(&current->sighand->siglock);
 335        return 0;
 336}
 337
 338EXPORT_SYMBOL(allow_signal);
 339
 340int disallow_signal(int sig)
 341{
 342        if (!valid_signal(sig) || sig < 1)
 343                return -EINVAL;
 344
 345        spin_lock_irq(&current->sighand->siglock);
 346        current->sighand->action[(sig)-1].sa.sa_handler = SIG_IGN;
 347        recalc_sigpending();
 348        spin_unlock_irq(&current->sighand->siglock);
 349        return 0;
 350}
 351
 352EXPORT_SYMBOL(disallow_signal);
 353
 354#ifdef CONFIG_MM_OWNER
 355/*
 356 * A task is exiting.   If it owned this mm, find a new owner for the mm.
 357 */
 358void mm_update_next_owner(struct mm_struct *mm)
 359{
 360        struct task_struct *c, *g, *p = current;
 361
 362retry:
 363        /*
 364         * If the exiting or execing task is not the owner, it's
 365         * someone else's problem.
 366         */
 367        if (mm->owner != p)
 368                return;
 369        /*
 370         * The current owner is exiting/execing and there are no other
 371         * candidates.  Do not leave the mm pointing to a possibly
 372         * freed task structure.
 373         */
 374        if (atomic_read(&mm->mm_users) <= 1) {
 375                mm->owner = NULL;
 376                return;
 377        }
 378
 379        read_lock(&tasklist_lock);
 380        /*
 381         * Search in the children
 382         */
 383        list_for_each_entry(c, &p->children, sibling) {
 384                if (c->mm == mm)
 385                        goto assign_new_owner;
 386        }
 387
 388        /*
 389         * Search in the siblings
 390         */
 391        list_for_each_entry(c, &p->real_parent->children, sibling) {
 392                if (c->mm == mm)
 393                        goto assign_new_owner;
 394        }
 395
 396        /*
 397         * Search through everything else. We should not get
 398         * here often
 399         */
 400        do_each_thread(g, c) {
 401                if (c->mm == mm)
 402                        goto assign_new_owner;
 403        } while_each_thread(g, c);
 404
 405        read_unlock(&tasklist_lock);
 406        /*
 407         * We found no owner yet mm_users > 1: this implies that we are
 408         * most likely racing with swapoff (try_to_unuse()) or /proc or
 409         * ptrace or page migration (get_task_mm()).  Mark owner as NULL.
 410         */
 411        mm->owner = NULL;
 412        return;
 413
 414assign_new_owner:
 415        BUG_ON(c == p);
 416        get_task_struct(c);
 417        /*
 418         * The task_lock protects c->mm from changing.
 419         * We always want mm->owner->mm == mm
 420         */
 421        task_lock(c);
 422        /*
 423         * Delay read_unlock() till we have the task_lock()
 424         * to ensure that c does not slip away underneath us
 425         */
 426        read_unlock(&tasklist_lock);
 427        if (c->mm != mm) {
 428                task_unlock(c);
 429                put_task_struct(c);
 430                goto retry;
 431        }
 432        mm->owner = c;
 433        task_unlock(c);
 434        put_task_struct(c);
 435}
 436#endif /* CONFIG_MM_OWNER */
 437
 438/*
 439 * Turn us into a lazy TLB process if we
 440 * aren't already..
 441 */
 442static void exit_mm(struct task_struct * tsk)
 443{
 444        struct mm_struct *mm = tsk->mm;
 445        struct core_state *core_state;
 446
 447        mm_release(tsk, mm);
 448        if (!mm)
 449                return;
 450        sync_mm_rss(mm);
 451        /*
 452         * Serialize with any possible pending coredump.
 453         * We must hold mmap_sem around checking core_state
 454         * and clearing tsk->mm.  The core-inducing thread
 455         * will increment ->nr_threads for each thread in the
 456         * group with ->mm != NULL.
 457         */
 458        down_read(&mm->mmap_sem);
 459        core_state = mm->core_state;
 460        if (core_state) {
 461                struct core_thread self;
 462                up_read(&mm->mmap_sem);
 463
 464                self.task = tsk;
 465                self.next = xchg(&core_state->dumper.next, &self);
 466                /*
 467                 * Implies mb(), the result of xchg() must be visible
 468                 * to core_state->dumper.
 469                 */
 470                if (atomic_dec_and_test(&core_state->nr_threads))
 471                        complete(&core_state->startup);
 472
 473                for (;;) {
 474                        set_task_state(tsk, TASK_UNINTERRUPTIBLE);
 475                        if (!self.task) /* see coredump_finish() */
 476                                break;
 477                        freezable_schedule();
 478                }
 479                __set_task_state(tsk, TASK_RUNNING);
 480                down_read(&mm->mmap_sem);
 481        }
 482        atomic_inc(&mm->mm_count);
 483        BUG_ON(mm != tsk->active_mm);
 484        /* more a memory barrier than a real lock */
 485        task_lock(tsk);
 486        tsk->mm = NULL;
 487        up_read(&mm->mmap_sem);
 488        enter_lazy_tlb(mm, current);
 489        task_unlock(tsk);
 490        mm_update_next_owner(mm);
 491        mmput(mm);
 492}
 493
 494/*
 495 * When we die, we re-parent all our children, and try to:
 496 * 1. give them to another thread in our thread group, if such a member exists
 497 * 2. give it to the first ancestor process which prctl'd itself as a
 498 *    child_subreaper for its children (like a service manager)
 499 * 3. give it to the init process (PID 1) in our pid namespace
 500 */
 501static struct task_struct *find_new_reaper(struct task_struct *father)
 502        __releases(&tasklist_lock)
 503        __acquires(&tasklist_lock)
 504{
 505        struct pid_namespace *pid_ns = task_active_pid_ns(father);
 506        struct task_struct *thread;
 507
 508        thread = father;
 509        while_each_thread(father, thread) {
 510                if (thread->flags & PF_EXITING)
 511                        continue;
 512                if (unlikely(pid_ns->child_reaper == father))
 513                        pid_ns->child_reaper = thread;
 514                return thread;
 515        }
 516
 517        if (unlikely(pid_ns->child_reaper == father)) {
 518                write_unlock_irq(&tasklist_lock);
 519                if (unlikely(pid_ns == &init_pid_ns)) {
 520                        panic("Attempted to kill init! exitcode=0x%08x\n",
 521                                father->signal->group_exit_code ?:
 522                                        father->exit_code);
 523                }
 524
 525                zap_pid_ns_processes(pid_ns);
 526                write_lock_irq(&tasklist_lock);
 527        } else if (father->signal->has_child_subreaper) {
 528                struct task_struct *reaper;
 529
 530                /*
 531                 * Find the first ancestor marked as child_subreaper.
 532                 * Note that the code below checks same_thread_group(reaper,
 533                 * pid_ns->child_reaper).  This is what we need to DTRT in a
 534                 * PID namespace. However we still need the check above, see
 535                 * http://marc.info/?l=linux-kernel&m=131385460420380
 536                 */
 537                for (reaper = father->real_parent;
 538                     reaper != &init_task;
 539                     reaper = reaper->real_parent) {
 540                        if (same_thread_group(reaper, pid_ns->child_reaper))
 541                                break;
 542                        if (!reaper->signal->is_child_subreaper)
 543                                continue;
 544                        thread = reaper;
 545                        do {
 546                                if (!(thread->flags & PF_EXITING))
 547                                        return reaper;
 548                        } while_each_thread(reaper, thread);
 549                }
 550        }
 551
 552        return pid_ns->child_reaper;
 553}
 554
 555/*
 556* Any that need to be release_task'd are put on the @dead list.
 557 */
 558static void reparent_leader(struct task_struct *father, struct task_struct *p,
 559                                struct list_head *dead)
 560{
 561        list_move_tail(&p->sibling, &p->real_parent->children);
 562
 563        if (p->exit_state == EXIT_DEAD)
 564                return;
 565        /*
 566         * If this is a threaded reparent there is no need to
 567         * notify anyone anything has happened.
 568         */
 569        if (same_thread_group(p->real_parent, father))
 570                return;
 571
 572        /* We don't want people slaying init.  */
 573        p->exit_signal = SIGCHLD;
 574
 575        /* If it has exited notify the new parent about this child's death. */
 576        if (!p->ptrace &&
 577            p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
 578                if (do_notify_parent(p, p->exit_signal)) {
 579                        p->exit_state = EXIT_DEAD;
 580                        list_move_tail(&p->sibling, dead);
 581                }
 582        }
 583
 584        kill_orphaned_pgrp(p, father);
 585}
 586
 587static void forget_original_parent(struct task_struct *father)
 588{
 589        struct task_struct *p, *n, *reaper;
 590        LIST_HEAD(dead_children);
 591
 592        write_lock_irq(&tasklist_lock);
 593        /*
 594         * Note that exit_ptrace() and find_new_reaper() might
 595         * drop tasklist_lock and reacquire it.
 596         */
 597        exit_ptrace(father);
 598        reaper = find_new_reaper(father);
 599
 600        list_for_each_entry_safe(p, n, &father->children, sibling) {
 601                struct task_struct *t = p;
 602                do {
 603                        t->real_parent = reaper;
 604                        if (t->parent == father) {
 605                                BUG_ON(t->ptrace);
 606                                t->parent = t->real_parent;
 607                        }
 608                        if (t->pdeath_signal)
 609                                group_send_sig_info(t->pdeath_signal,
 610                                                    SEND_SIG_NOINFO, t);
 611                } while_each_thread(p, t);
 612                reparent_leader(father, p, &dead_children);
 613        }
 614        write_unlock_irq(&tasklist_lock);
 615
 616        BUG_ON(!list_empty(&father->children));
 617
 618        list_for_each_entry_safe(p, n, &dead_children, sibling) {
 619                list_del_init(&p->sibling);
 620                release_task(p);
 621        }
 622}
 623
 624/*
 625 * Send signals to all our closest relatives so that they know
 626 * to properly mourn us..
 627 */
 628static void exit_notify(struct task_struct *tsk, int group_dead)
 629{
 630        bool autoreap;
 631
 632        /*
 633         * This does two things:
 634         *
 635         * A.  Make init inherit all the child processes
 636         * B.  Check to see if any process groups have become orphaned
 637         *      as a result of our exiting, and if they have any stopped
 638         *      jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
 639         */
 640        forget_original_parent(tsk);
 641
 642        write_lock_irq(&tasklist_lock);
 643        if (group_dead)
 644                kill_orphaned_pgrp(tsk->group_leader, NULL);
 645
 646        if (unlikely(tsk->ptrace)) {
 647                int sig = thread_group_leader(tsk) &&
 648                                thread_group_empty(tsk) &&
 649                                !ptrace_reparented(tsk) ?
 650                        tsk->exit_signal : SIGCHLD;
 651                autoreap = do_notify_parent(tsk, sig);
 652        } else if (thread_group_leader(tsk)) {
 653                autoreap = thread_group_empty(tsk) &&
 654                        do_notify_parent(tsk, tsk->exit_signal);
 655        } else {
 656                autoreap = true;
 657        }
 658
 659        tsk->exit_state = autoreap ? EXIT_DEAD : EXIT_ZOMBIE;
 660
 661        /* mt-exec, de_thread() is waiting for group leader */
 662        if (unlikely(tsk->signal->notify_count < 0))
 663                wake_up_process(tsk->signal->group_exit_task);
 664        write_unlock_irq(&tasklist_lock);
 665
 666        /* If the process is dead, release it - nobody will wait for it */
 667        if (autoreap)
 668                release_task(tsk);
 669}
 670
 671#ifdef CONFIG_DEBUG_STACK_USAGE
 672static void check_stack_usage(void)
 673{
 674        static DEFINE_SPINLOCK(low_water_lock);
 675        static int lowest_to_date = THREAD_SIZE;
 676        unsigned long free;
 677
 678        free = stack_not_used(current);
 679
 680        if (free >= lowest_to_date)
 681                return;
 682
 683        spin_lock(&low_water_lock);
 684        if (free < lowest_to_date) {
 685                printk(KERN_WARNING "%s (%d) used greatest stack depth: "
 686                                "%lu bytes left\n",
 687                                current->comm, task_pid_nr(current), free);
 688                lowest_to_date = free;
 689        }
 690        spin_unlock(&low_water_lock);
 691}
 692#else
 693static inline void check_stack_usage(void) {}
 694#endif
 695
 696void do_exit(long code)
 697{
 698        struct task_struct *tsk = current;
 699        int group_dead;
 700
 701        profile_task_exit(tsk);
 702
 703        WARN_ON(blk_needs_flush_plug(tsk));
 704
 705        if (unlikely(in_interrupt()))
 706                panic("Aiee, killing interrupt handler!");
 707        if (unlikely(!tsk->pid))
 708                panic("Attempted to kill the idle task!");
 709
 710        /*
 711         * If do_exit is called because this processes oopsed, it's possible
 712         * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before
 713         * continuing. Amongst other possible reasons, this is to prevent
 714         * mm_release()->clear_child_tid() from writing to a user-controlled
 715         * kernel address.
 716         */
 717        set_fs(USER_DS);
 718
 719        ptrace_event(PTRACE_EVENT_EXIT, code);
 720
 721        validate_creds_for_do_exit(tsk);
 722
 723        /*
 724         * We're taking recursive faults here in do_exit. Safest is to just
 725         * leave this task alone and wait for reboot.
 726         */
 727        if (unlikely(tsk->flags & PF_EXITING)) {
 728                printk(KERN_ALERT
 729                        "Fixing recursive fault but reboot is needed!\n");
 730                /*
 731                 * We can do this unlocked here. The futex code uses
 732                 * this flag just to verify whether the pi state
 733                 * cleanup has been done or not. In the worst case it
 734                 * loops once more. We pretend that the cleanup was
 735                 * done as there is no way to return. Either the
 736                 * OWNER_DIED bit is set by now or we push the blocked
 737                 * task into the wait for ever nirwana as well.
 738                 */
 739                tsk->flags |= PF_EXITPIDONE;
 740                set_current_state(TASK_UNINTERRUPTIBLE);
 741                schedule();
 742        }
 743
 744        exit_signals(tsk);  /* sets PF_EXITING */
 745        /*
 746         * tsk->flags are checked in the futex code to protect against
 747         * an exiting task cleaning up the robust pi futexes.
 748         */
 749        smp_mb();
 750        raw_spin_unlock_wait(&tsk->pi_lock);
 751
 752        if (unlikely(in_atomic()))
 753                printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
 754                                current->comm, task_pid_nr(current),
 755                                preempt_count());
 756
 757        acct_update_integrals(tsk);
 758        /* sync mm's RSS info before statistics gathering */
 759        if (tsk->mm)
 760                sync_mm_rss(tsk->mm);
 761        group_dead = atomic_dec_and_test(&tsk->signal->live);
 762        if (group_dead) {
 763                hrtimer_cancel(&tsk->signal->real_timer);
 764                exit_itimers(tsk->signal);
 765                if (tsk->mm)
 766                        setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm);
 767        }
 768        acct_collect(code, group_dead);
 769        if (group_dead)
 770                tty_audit_exit();
 771        audit_free(tsk);
 772
 773        tsk->exit_code = code;
 774        taskstats_exit(tsk, group_dead);
 775
 776        exit_mm(tsk);
 777
 778        if (group_dead)
 779                acct_process();
 780        trace_sched_process_exit(tsk);
 781
 782        exit_sem(tsk);
 783        exit_shm(tsk);
 784        exit_files(tsk);
 785        exit_fs(tsk);
 786        exit_task_namespaces(tsk);
 787        exit_task_work(tsk);
 788        check_stack_usage();
 789        exit_thread();
 790
 791        /*
 792         * Flush inherited counters to the parent - before the parent
 793         * gets woken up by child-exit notifications.
 794         *
 795         * because of cgroup mode, must be called before cgroup_exit()
 796         */
 797        perf_event_exit_task(tsk);
 798
 799        cgroup_exit(tsk, 1);
 800
 801        if (group_dead)
 802                disassociate_ctty(1);
 803
 804        module_put(task_thread_info(tsk)->exec_domain->module);
 805
 806        proc_exit_connector(tsk);
 807
 808        /*
 809         * FIXME: do that only when needed, using sched_exit tracepoint
 810         */
 811        flush_ptrace_hw_breakpoint(tsk);
 812
 813        exit_notify(tsk, group_dead);
 814#ifdef CONFIG_NUMA
 815        task_lock(tsk);
 816        mpol_put(tsk->mempolicy);
 817        tsk->mempolicy = NULL;
 818        task_unlock(tsk);
 819#endif
 820#ifdef CONFIG_FUTEX
 821        if (unlikely(current->pi_state_cache))
 822                kfree(current->pi_state_cache);
 823#endif
 824        /*
 825         * Make sure we are holding no locks:
 826         */
 827        debug_check_no_locks_held();
 828        /*
 829         * We can do this unlocked here. The futex code uses this flag
 830         * just to verify whether the pi state cleanup has been done
 831         * or not. In the worst case it loops once more.
 832         */
 833        tsk->flags |= PF_EXITPIDONE;
 834
 835        if (tsk->io_context)
 836                exit_io_context(tsk);
 837
 838        if (tsk->splice_pipe)
 839                free_pipe_info(tsk->splice_pipe);
 840
 841        if (tsk->task_frag.page)
 842                put_page(tsk->task_frag.page);
 843
 844        validate_creds_for_do_exit(tsk);
 845
 846        preempt_disable();
 847        if (tsk->nr_dirtied)
 848                __this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied);
 849        exit_rcu();
 850
 851        /*
 852         * The setting of TASK_RUNNING by try_to_wake_up() may be delayed
 853         * when the following two conditions become true.
 854         *   - There is race condition of mmap_sem (It is acquired by
 855         *     exit_mm()), and
 856         *   - SMI occurs before setting TASK_RUNINNG.
 857         *     (or hypervisor of virtual machine switches to other guest)
 858         *  As a result, we may become TASK_RUNNING after becoming TASK_DEAD
 859         *
 860         * To avoid it, we have to wait for releasing tsk->pi_lock which
 861         * is held by try_to_wake_up()
 862         */
 863        smp_mb();
 864        raw_spin_unlock_wait(&tsk->pi_lock);
 865
 866        /* causes final put_task_struct in finish_task_switch(). */
 867        tsk->state = TASK_DEAD;
 868        tsk->flags |= PF_NOFREEZE;      /* tell freezer to ignore us */
 869        schedule();
 870        BUG();
 871        /* Avoid "noreturn function does return".  */
 872        for (;;)
 873                cpu_relax();    /* For when BUG is null */
 874}
 875
 876EXPORT_SYMBOL_GPL(do_exit);
 877
 878void complete_and_exit(struct completion *comp, long code)
 879{
 880        if (comp)
 881                complete(comp);
 882
 883        do_exit(code);
 884}
 885
 886EXPORT_SYMBOL(complete_and_exit);
 887
 888SYSCALL_DEFINE1(exit, int, error_code)
 889{
 890        do_exit((error_code&0xff)<<8);
 891}
 892
 893/*
 894 * Take down every thread in the group.  This is called by fatal signals
 895 * as well as by sys_exit_group (below).
 896 */
 897void
 898do_group_exit(int exit_code)
 899{
 900        struct signal_struct *sig = current->signal;
 901
 902        BUG_ON(exit_code & 0x80); /* core dumps don't get here */
 903
 904        if (signal_group_exit(sig))
 905                exit_code = sig->group_exit_code;
 906        else if (!thread_group_empty(current)) {
 907                struct sighand_struct *const sighand = current->sighand;
 908                spin_lock_irq(&sighand->siglock);
 909                if (signal_group_exit(sig))
 910                        /* Another thread got here before we took the lock.  */
 911                        exit_code = sig->group_exit_code;
 912                else {
 913                        sig->group_exit_code = exit_code;
 914                        sig->flags = SIGNAL_GROUP_EXIT;
 915                        zap_other_threads(current);
 916                }
 917                spin_unlock_irq(&sighand->siglock);
 918        }
 919
 920        do_exit(exit_code);
 921        /* NOTREACHED */
 922}
 923
 924/*
 925 * this kills every thread in the thread group. Note that any externally
 926 * wait4()-ing process will get the correct exit code - even if this
 927 * thread is not the thread group leader.
 928 */
 929SYSCALL_DEFINE1(exit_group, int, error_code)
 930{
 931        do_group_exit((error_code & 0xff) << 8);
 932        /* NOTREACHED */
 933        return 0;
 934}
 935
 936struct wait_opts {
 937        enum pid_type           wo_type;
 938        int                     wo_flags;
 939        struct pid              *wo_pid;
 940
 941        struct siginfo __user   *wo_info;
 942        int __user              *wo_stat;
 943        struct rusage __user    *wo_rusage;
 944
 945        wait_queue_t            child_wait;
 946        int                     notask_error;
 947};
 948
 949static inline
 950struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
 951{
 952        if (type != PIDTYPE_PID)
 953                task = task->group_leader;
 954        return task->pids[type].pid;
 955}
 956
 957static int eligible_pid(struct wait_opts *wo, struct task_struct *p)
 958{
 959        return  wo->wo_type == PIDTYPE_MAX ||
 960                task_pid_type(p, wo->wo_type) == wo->wo_pid;
 961}
 962
 963static int eligible_child(struct wait_opts *wo, struct task_struct *p)
 964{
 965        if (!eligible_pid(wo, p))
 966                return 0;
 967        /* Wait for all children (clone and not) if __WALL is set;
 968         * otherwise, wait for clone children *only* if __WCLONE is
 969         * set; otherwise, wait for non-clone children *only*.  (Note:
 970         * A "clone" child here is one that reports to its parent
 971         * using a signal other than SIGCHLD.) */
 972        if (((p->exit_signal != SIGCHLD) ^ !!(wo->wo_flags & __WCLONE))
 973            && !(wo->wo_flags & __WALL))
 974                return 0;
 975
 976        return 1;
 977}
 978
 979static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
 980                                pid_t pid, uid_t uid, int why, int status)
 981{
 982        struct siginfo __user *infop;
 983        int retval = wo->wo_rusage
 984                ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
 985
 986        put_task_struct(p);
 987        infop = wo->wo_info;
 988        if (infop) {
 989                if (!retval)
 990                        retval = put_user(SIGCHLD, &infop->si_signo);
 991                if (!retval)
 992                        retval = put_user(0, &infop->si_errno);
 993                if (!retval)
 994                        retval = put_user((short)why, &infop->si_code);
 995                if (!retval)
 996                        retval = put_user(pid, &infop->si_pid);
 997                if (!retval)
 998                        retval = put_user(uid, &infop->si_uid);
 999                if (!retval)
1000                        retval = put_user(status, &infop->si_status);
1001        }
1002        if (!retval)
1003                retval = pid;
1004        return retval;
1005}
1006
1007/*
1008 * Handle sys_wait4 work for one task in state EXIT_ZOMBIE.  We hold
1009 * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1010 * the lock and this task is uninteresting.  If we return nonzero, we have
1011 * released the lock and the system call should return.
1012 */
1013static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
1014{
1015        unsigned long state;
1016        int retval, status, traced;
1017        pid_t pid = task_pid_vnr(p);
1018        uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p));
1019        struct siginfo __user *infop;
1020
1021        if (!likely(wo->wo_flags & WEXITED))
1022                return 0;
1023
1024        if (unlikely(wo->wo_flags & WNOWAIT)) {
1025                int exit_code = p->exit_code;
1026                int why;
1027
1028                get_task_struct(p);
1029                read_unlock(&tasklist_lock);
1030                if ((exit_code & 0x7f) == 0) {
1031                        why = CLD_EXITED;
1032                        status = exit_code >> 8;
1033                } else {
1034                        why = (exit_code & 0x80) ? CLD_DUMPED : CLD_KILLED;
1035                        status = exit_code & 0x7f;
1036                }
1037                return wait_noreap_copyout(wo, p, pid, uid, why, status);
1038        }
1039
1040        /*
1041         * Try to move the task's state to DEAD
1042         * only one thread is allowed to do this:
1043         */
1044        state = xchg(&p->exit_state, EXIT_DEAD);
1045        if (state != EXIT_ZOMBIE) {
1046                BUG_ON(state != EXIT_DEAD);
1047                return 0;
1048        }
1049
1050        traced = ptrace_reparented(p);
1051        /*
1052         * It can be ptraced but not reparented, check
1053         * thread_group_leader() to filter out sub-threads.
1054         */
1055        if (likely(!traced) && thread_group_leader(p)) {
1056                struct signal_struct *psig;
1057                struct signal_struct *sig;
1058                unsigned long maxrss;
1059                cputime_t tgutime, tgstime;
1060
1061                /*
1062                 * The resource counters for the group leader are in its
1063                 * own task_struct.  Those for dead threads in the group
1064                 * are in its signal_struct, as are those for the child
1065                 * processes it has previously reaped.  All these
1066                 * accumulate in the parent's signal_struct c* fields.
1067                 *
1068                 * We don't bother to take a lock here to protect these
1069                 * p->signal fields, because they are only touched by
1070                 * __exit_signal, which runs with tasklist_lock
1071                 * write-locked anyway, and so is excluded here.  We do
1072                 * need to protect the access to parent->signal fields,
1073                 * as other threads in the parent group can be right
1074                 * here reaping other children at the same time.
1075                 *
1076                 * We use thread_group_cputime_adjusted() to get times for the thread
1077                 * group, which consolidates times for all threads in the
1078                 * group including the group leader.
1079                 */
1080                thread_group_cputime_adjusted(p, &tgutime, &tgstime);
1081                spin_lock_irq(&p->real_parent->sighand->siglock);
1082                psig = p->real_parent->signal;
1083                sig = p->signal;
1084                psig->cutime += tgutime + sig->cutime;
1085                psig->cstime += tgstime + sig->cstime;
1086                psig->cgtime += task_gtime(p) + sig->gtime + sig->cgtime;
1087                psig->cmin_flt +=
1088                        p->min_flt + sig->min_flt + sig->cmin_flt;
1089                psig->cmaj_flt +=
1090                        p->maj_flt + sig->maj_flt + sig->cmaj_flt;
1091                psig->cnvcsw +=
1092                        p->nvcsw + sig->nvcsw + sig->cnvcsw;
1093                psig->cnivcsw +=
1094                        p->nivcsw + sig->nivcsw + sig->cnivcsw;
1095                psig->cinblock +=
1096                        task_io_get_inblock(p) +
1097                        sig->inblock + sig->cinblock;
1098                psig->coublock +=
1099                        task_io_get_oublock(p) +
1100                        sig->oublock + sig->coublock;
1101                maxrss = max(sig->maxrss, sig->cmaxrss);
1102                if (psig->cmaxrss < maxrss)
1103                        psig->cmaxrss = maxrss;
1104                task_io_accounting_add(&psig->ioac, &p->ioac);
1105                task_io_accounting_add(&psig->ioac, &sig->ioac);
1106                spin_unlock_irq(&p->real_parent->sighand->siglock);
1107        }
1108
1109        /*
1110         * Now we are sure this task is interesting, and no other
1111         * thread can reap it because we set its state to EXIT_DEAD.
1112         */
1113        read_unlock(&tasklist_lock);
1114
1115        retval = wo->wo_rusage
1116                ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1117        status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1118                ? p->signal->group_exit_code : p->exit_code;
1119        if (!retval && wo->wo_stat)
1120                retval = put_user(status, wo->wo_stat);
1121
1122        infop = wo->wo_info;
1123        if (!retval && infop)
1124                retval = put_user(SIGCHLD, &infop->si_signo);
1125        if (!retval && infop)
1126                retval = put_user(0, &infop->si_errno);
1127        if (!retval && infop) {
1128                int why;
1129
1130                if ((status & 0x7f) == 0) {
1131                        why = CLD_EXITED;
1132                        status >>= 8;
1133                } else {
1134                        why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
1135                        status &= 0x7f;
1136                }
1137                retval = put_user((short)why, &infop->si_code);
1138                if (!retval)
1139                        retval = put_user(status, &infop->si_status);
1140        }
1141        if (!retval && infop)
1142                retval = put_user(pid, &infop->si_pid);
1143        if (!retval && infop)
1144                retval = put_user(uid, &infop->si_uid);
1145        if (!retval)
1146                retval = pid;
1147
1148        if (traced) {
1149                write_lock_irq(&tasklist_lock);
1150                /* We dropped tasklist, ptracer could die and untrace */
1151                ptrace_unlink(p);
1152                /*
1153                 * If this is not a sub-thread, notify the parent.
1154                 * If parent wants a zombie, don't release it now.
1155                 */
1156                if (thread_group_leader(p) &&
1157                    !do_notify_parent(p, p->exit_signal)) {
1158                        p->exit_state = EXIT_ZOMBIE;
1159                        p = NULL;
1160                }
1161                write_unlock_irq(&tasklist_lock);
1162        }
1163        if (p != NULL)
1164                release_task(p);
1165
1166        return retval;
1167}
1168
1169static int *task_stopped_code(struct task_struct *p, bool ptrace)
1170{
1171        if (ptrace) {
1172                if (task_is_stopped_or_traced(p) &&
1173                    !(p->jobctl & JOBCTL_LISTENING))
1174                        return &p->exit_code;
1175        } else {
1176                if (p->signal->flags & SIGNAL_STOP_STOPPED)
1177                        return &p->signal->group_exit_code;
1178        }
1179        return NULL;
1180}
1181
1182/**
1183 * wait_task_stopped - Wait for %TASK_STOPPED or %TASK_TRACED
1184 * @wo: wait options
1185 * @ptrace: is the wait for ptrace
1186 * @p: task to wait for
1187 *
1188 * Handle sys_wait4() work for %p in state %TASK_STOPPED or %TASK_TRACED.
1189 *
1190 * CONTEXT:
1191 * read_lock(&tasklist_lock), which is released if return value is
1192 * non-zero.  Also, grabs and releases @p->sighand->siglock.
1193 *
1194 * RETURNS:
1195 * 0 if wait condition didn't exist and search for other wait conditions
1196 * should continue.  Non-zero return, -errno on failure and @p's pid on
1197 * success, implies that tasklist_lock is released and wait condition
1198 * search should terminate.
1199 */
1200static int wait_task_stopped(struct wait_opts *wo,
1201                                int ptrace, struct task_struct *p)
1202{
1203        struct siginfo __user *infop;
1204        int retval, exit_code, *p_code, why;
1205        uid_t uid = 0; /* unneeded, required by compiler */
1206        pid_t pid;
1207
1208        /*
1209         * Traditionally we see ptrace'd stopped tasks regardless of options.
1210         */
1211        if (!ptrace && !(wo->wo_flags & WUNTRACED))
1212                return 0;
1213
1214        if (!task_stopped_code(p, ptrace))
1215                return 0;
1216
1217        exit_code = 0;
1218        spin_lock_irq(&p->sighand->siglock);
1219
1220        p_code = task_stopped_code(p, ptrace);
1221        if (unlikely(!p_code))
1222                goto unlock_sig;
1223
1224        exit_code = *p_code;
1225        if (!exit_code)
1226                goto unlock_sig;
1227
1228        if (!unlikely(wo->wo_flags & WNOWAIT))
1229                *p_code = 0;
1230
1231        uid = from_kuid_munged(current_user_ns(), task_uid(p));
1232unlock_sig:
1233        spin_unlock_irq(&p->sighand->siglock);
1234        if (!exit_code)
1235                return 0;
1236
1237        /*
1238         * Now we are pretty sure this task is interesting.
1239         * Make sure it doesn't get reaped out from under us while we
1240         * give up the lock and then examine it below.  We don't want to
1241         * keep holding onto the tasklist_lock while we call getrusage and
1242         * possibly take page faults for user memory.
1243         */
1244        get_task_struct(p);
1245        pid = task_pid_vnr(p);
1246        why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
1247        read_unlock(&tasklist_lock);
1248
1249        if (unlikely(wo->wo_flags & WNOWAIT))
1250                return wait_noreap_copyout(wo, p, pid, uid, why, exit_code);
1251
1252        retval = wo->wo_rusage
1253                ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1254        if (!retval && wo->wo_stat)
1255                retval = put_user((exit_code << 8) | 0x7f, wo->wo_stat);
1256
1257        infop = wo->wo_info;
1258        if (!retval && infop)
1259                retval = put_user(SIGCHLD, &infop->si_signo);
1260        if (!retval && infop)
1261                retval = put_user(0, &infop->si_errno);
1262        if (!retval && infop)
1263                retval = put_user((short)why, &infop->si_code);
1264        if (!retval && infop)
1265                retval = put_user(exit_code, &infop->si_status);
1266        if (!retval && infop)
1267                retval = put_user(pid, &infop->si_pid);
1268        if (!retval && infop)
1269                retval = put_user(uid, &infop->si_uid);
1270        if (!retval)
1271                retval = pid;
1272        put_task_struct(p);
1273
1274        BUG_ON(!retval);
1275        return retval;
1276}
1277
1278/*
1279 * Handle do_wait work for one task in a live, non-stopped state.
1280 * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1281 * the lock and this task is uninteresting.  If we return nonzero, we have
1282 * released the lock and the system call should return.
1283 */
1284static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
1285{
1286        int retval;
1287        pid_t pid;
1288        uid_t uid;
1289
1290        if (!unlikely(wo->wo_flags & WCONTINUED))
1291                return 0;
1292
1293        if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
1294                return 0;
1295
1296        spin_lock_irq(&p->sighand->siglock);
1297        /* Re-check with the lock held.  */
1298        if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
1299                spin_unlock_irq(&p->sighand->siglock);
1300                return 0;
1301        }
1302        if (!unlikely(wo->wo_flags & WNOWAIT))
1303                p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1304        uid = from_kuid_munged(current_user_ns(), task_uid(p));
1305        spin_unlock_irq(&p->sighand->siglock);
1306
1307        pid = task_pid_vnr(p);
1308        get_task_struct(p);
1309        read_unlock(&tasklist_lock);
1310
1311        if (!wo->wo_info) {
1312                retval = wo->wo_rusage
1313                        ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1314                put_task_struct(p);
1315                if (!retval && wo->wo_stat)
1316                        retval = put_user(0xffff, wo->wo_stat);
1317                if (!retval)
1318                        retval = pid;
1319        } else {
1320                retval = wait_noreap_copyout(wo, p, pid, uid,
1321                                             CLD_CONTINUED, SIGCONT);
1322                BUG_ON(retval == 0);
1323        }
1324
1325        return retval;
1326}
1327
1328/*
1329 * Consider @p for a wait by @parent.
1330 *
1331 * -ECHILD should be in ->notask_error before the first call.
1332 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1333 * Returns zero if the search for a child should continue;
1334 * then ->notask_error is 0 if @p is an eligible child,
1335 * or another error from security_task_wait(), or still -ECHILD.
1336 */
1337static int wait_consider_task(struct wait_opts *wo, int ptrace,
1338                                struct task_struct *p)
1339{
1340        int ret = eligible_child(wo, p);
1341        if (!ret)
1342                return ret;
1343
1344        ret = security_task_wait(p);
1345        if (unlikely(ret < 0)) {
1346                /*
1347                 * If we have not yet seen any eligible child,
1348                 * then let this error code replace -ECHILD.
1349                 * A permission error will give the user a clue
1350                 * to look for security policy problems, rather
1351                 * than for mysterious wait bugs.
1352                 */
1353                if (wo->notask_error)
1354                        wo->notask_error = ret;
1355                return 0;
1356        }
1357
1358        /* dead body doesn't have much to contribute */
1359        if (unlikely(p->exit_state == EXIT_DEAD)) {
1360                /*
1361                 * But do not ignore this task until the tracer does
1362                 * wait_task_zombie()->do_notify_parent().
1363                 */
1364                if (likely(!ptrace) && unlikely(ptrace_reparented(p)))
1365                        wo->notask_error = 0;
1366                return 0;
1367        }
1368
1369        /* slay zombie? */
1370        if (p->exit_state == EXIT_ZOMBIE) {
1371                /*
1372                 * A zombie ptracee is only visible to its ptracer.
1373                 * Notification and reaping will be cascaded to the real
1374                 * parent when the ptracer detaches.
1375                 */
1376                if (likely(!ptrace) && unlikely(p->ptrace)) {
1377                        /* it will become visible, clear notask_error */
1378                        wo->notask_error = 0;
1379                        return 0;
1380                }
1381
1382                /* we don't reap group leaders with subthreads */
1383                if (!delay_group_leader(p))
1384                        return wait_task_zombie(wo, p);
1385
1386                /*
1387                 * Allow access to stopped/continued state via zombie by
1388                 * falling through.  Clearing of notask_error is complex.
1389                 *
1390                 * When !@ptrace:
1391                 *
1392                 * If WEXITED is set, notask_error should naturally be
1393                 * cleared.  If not, subset of WSTOPPED|WCONTINUED is set,
1394                 * so, if there are live subthreads, there are events to
1395                 * wait for.  If all subthreads are dead, it's still safe
1396                 * to clear - this function will be called again in finite
1397                 * amount time once all the subthreads are released and
1398                 * will then return without clearing.
1399                 *
1400                 * When @ptrace:
1401                 *
1402                 * Stopped state is per-task and thus can't change once the
1403                 * target task dies.  Only continued and exited can happen.
1404                 * Clear notask_error if WCONTINUED | WEXITED.
1405                 */
1406                if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED)))
1407                        wo->notask_error = 0;
1408        } else {
1409                /*
1410                 * If @p is ptraced by a task in its real parent's group,
1411                 * hide group stop/continued state when looking at @p as
1412                 * the real parent; otherwise, a single stop can be
1413                 * reported twice as group and ptrace stops.
1414                 *
1415                 * If a ptracer wants to distinguish the two events for its
1416                 * own children, it should create a separate process which
1417                 * takes the role of real parent.
1418                 */
1419                if (likely(!ptrace) && p->ptrace && !ptrace_reparented(p))
1420                        return 0;
1421
1422                /*
1423                 * @p is alive and it's gonna stop, continue or exit, so
1424                 * there always is something to wait for.
1425                 */
1426                wo->notask_error = 0;
1427        }
1428
1429        /*
1430         * Wait for stopped.  Depending on @ptrace, different stopped state
1431         * is used and the two don't interact with each other.
1432         */
1433        ret = wait_task_stopped(wo, ptrace, p);
1434        if (ret)
1435                return ret;
1436
1437        /*
1438         * Wait for continued.  There's only one continued state and the
1439         * ptracer can consume it which can confuse the real parent.  Don't
1440         * use WCONTINUED from ptracer.  You don't need or want it.
1441         */
1442        return wait_task_continued(wo, p);
1443}
1444
1445/*
1446 * Do the work of do_wait() for one thread in the group, @tsk.
1447 *
1448 * -ECHILD should be in ->notask_error before the first call.
1449 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1450 * Returns zero if the search for a child should continue; then
1451 * ->notask_error is 0 if there were any eligible children,
1452 * or another error from security_task_wait(), or still -ECHILD.
1453 */
1454static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk)
1455{
1456        struct task_struct *p;
1457
1458        list_for_each_entry(p, &tsk->children, sibling) {
1459                int ret = wait_consider_task(wo, 0, p);
1460                if (ret)
1461                        return ret;
1462        }
1463
1464        return 0;
1465}
1466
1467static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk)
1468{
1469        struct task_struct *p;
1470
1471        list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
1472                int ret = wait_consider_task(wo, 1, p);
1473                if (ret)
1474                        return ret;
1475        }
1476
1477        return 0;
1478}
1479
1480static int child_wait_callback(wait_queue_t *wait, unsigned mode,
1481                                int sync, void *key)
1482{
1483        struct wait_opts *wo = container_of(wait, struct wait_opts,
1484                                                child_wait);
1485        struct task_struct *p = key;
1486
1487        if (!eligible_pid(wo, p))
1488                return 0;
1489
1490        if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent)
1491                return 0;
1492
1493        return default_wake_function(wait, mode, sync, key);
1494}
1495
1496void __wake_up_parent(struct task_struct *p, struct task_struct *parent)
1497{
1498        __wake_up_sync_key(&parent->signal->wait_chldexit,
1499                                TASK_INTERRUPTIBLE, 1, p);
1500}
1501
1502static long do_wait(struct wait_opts *wo)
1503{
1504        struct task_struct *tsk;
1505        int retval;
1506
1507        trace_sched_process_wait(wo->wo_pid);
1508
1509        init_waitqueue_func_entry(&wo->child_wait, child_wait_callback);
1510        wo->child_wait.private = current;
1511        add_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1512repeat:
1513        /*
1514         * If there is nothing that can match our critiera just get out.
1515         * We will clear ->notask_error to zero if we see any child that
1516         * might later match our criteria, even if we are not able to reap
1517         * it yet.
1518         */
1519        wo->notask_error = -ECHILD;
1520        if ((wo->wo_type < PIDTYPE_MAX) &&
1521           (!wo->wo_pid || hlist_empty(&wo->wo_pid->tasks[wo->wo_type])))
1522                goto notask;
1523
1524        set_current_state(TASK_INTERRUPTIBLE);
1525        read_lock(&tasklist_lock);
1526        tsk = current;
1527        do {
1528                retval = do_wait_thread(wo, tsk);
1529                if (retval)
1530                        goto end;
1531
1532                retval = ptrace_do_wait(wo, tsk);
1533                if (retval)
1534                        goto end;
1535
1536                if (wo->wo_flags & __WNOTHREAD)
1537                        break;
1538        } while_each_thread(current, tsk);
1539        read_unlock(&tasklist_lock);
1540
1541notask:
1542        retval = wo->notask_error;
1543        if (!retval && !(wo->wo_flags & WNOHANG)) {
1544                retval = -ERESTARTSYS;
1545                if (!signal_pending(current)) {
1546                        schedule();
1547                        goto repeat;
1548                }
1549        }
1550end:
1551        __set_current_state(TASK_RUNNING);
1552        remove_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1553        return retval;
1554}
1555
1556SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
1557                infop, int, options, struct rusage __user *, ru)
1558{
1559        struct wait_opts wo;
1560        struct pid *pid = NULL;
1561        enum pid_type type;
1562        long ret;
1563
1564        if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED))
1565                return -EINVAL;
1566        if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
1567                return -EINVAL;
1568
1569        switch (which) {
1570        case P_ALL:
1571                type = PIDTYPE_MAX;
1572                break;
1573        case P_PID:
1574                type = PIDTYPE_PID;
1575                if (upid <= 0)
1576                        return -EINVAL;
1577                break;
1578        case P_PGID:
1579                type = PIDTYPE_PGID;
1580                if (upid <= 0)
1581                        return -EINVAL;
1582                break;
1583        default:
1584                return -EINVAL;
1585        }
1586
1587        if (type < PIDTYPE_MAX)
1588                pid = find_get_pid(upid);
1589
1590        wo.wo_type      = type;
1591        wo.wo_pid       = pid;
1592        wo.wo_flags     = options;
1593        wo.wo_info      = infop;
1594        wo.wo_stat      = NULL;
1595        wo.wo_rusage    = ru;
1596        ret = do_wait(&wo);
1597
1598        if (ret > 0) {
1599                ret = 0;
1600        } else if (infop) {
1601                /*
1602                 * For a WNOHANG return, clear out all the fields
1603                 * we would set so the user can easily tell the
1604                 * difference.
1605                 */
1606                if (!ret)
1607                        ret = put_user(0, &infop->si_signo);
1608                if (!ret)
1609                        ret = put_user(0, &infop->si_errno);
1610                if (!ret)
1611                        ret = put_user(0, &infop->si_code);
1612                if (!ret)
1613                        ret = put_user(0, &infop->si_pid);
1614                if (!ret)
1615                        ret = put_user(0, &infop->si_uid);
1616                if (!ret)
1617                        ret = put_user(0, &infop->si_status);
1618        }
1619
1620        put_pid(pid);
1621        return ret;
1622}
1623
1624SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
1625                int, options, struct rusage __user *, ru)
1626{
1627        struct wait_opts wo;
1628        struct pid *pid = NULL;
1629        enum pid_type type;
1630        long ret;
1631
1632        if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
1633                        __WNOTHREAD|__WCLONE|__WALL))
1634                return -EINVAL;
1635
1636        if (upid == -1)
1637                type = PIDTYPE_MAX;
1638        else if (upid < 0) {
1639                type = PIDTYPE_PGID;
1640                pid = find_get_pid(-upid);
1641        } else if (upid == 0) {
1642                type = PIDTYPE_PGID;
1643                pid = get_task_pid(current, PIDTYPE_PGID);
1644        } else /* upid > 0 */ {
1645                type = PIDTYPE_PID;
1646                pid = find_get_pid(upid);
1647        }
1648
1649        wo.wo_type      = type;
1650        wo.wo_pid       = pid;
1651        wo.wo_flags     = options | WEXITED;
1652        wo.wo_info      = NULL;
1653        wo.wo_stat      = stat_addr;
1654        wo.wo_rusage    = ru;
1655        ret = do_wait(&wo);
1656        put_pid(pid);
1657
1658        return ret;
1659}
1660
1661#ifdef __ARCH_WANT_SYS_WAITPID
1662
1663/*
1664 * sys_waitpid() remains for compatibility. waitpid() should be
1665 * implemented by calling sys_wait4() from libc.a.
1666 */
1667SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options)
1668{
1669        return sys_wait4(pid, stat_addr, options, NULL);
1670}
1671
1672#endif
1673
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