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/mnt_namespace.h>
  16#include <linux/iocontext.h>
  17#include <linux/key.h>
  18#include <linux/security.h>
  19#include <linux/cpu.h>
  20#include <linux/acct.h>
  21#include <linux/tsacct_kern.h>
  22#include <linux/file.h>
  23#include <linux/fdtable.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/freezer.h>
  36#include <linux/cgroup.h>
  37#include <linux/syscalls.h>
  38#include <linux/signal.h>
  39#include <linux/posix-timers.h>
  40#include <linux/cn_proc.h>
  41#include <linux/mutex.h>
  42#include <linux/futex.h>
  43#include <linux/pipe_fs_i.h>
  44#include <linux/audit.h> /* for audit_free() */
  45#include <linux/resource.h>
  46#include <linux/blkdev.h>
  47#include <linux/task_io_accounting_ops.h>
  48#include <linux/tracehook.h>
  49#include <trace/sched.h>
  50
  51#include <asm/uaccess.h>
  52#include <asm/unistd.h>
  53#include <asm/pgtable.h>
  54#include <asm/mmu_context.h>
  55
  56static void exit_mm(struct task_struct * tsk);
  57
  58static inline int task_detached(struct task_struct *p)
  59{
  60        return p->exit_signal == -1;
  61}
  62
  63static void __unhash_process(struct task_struct *p)
  64{
  65        nr_threads--;
  66        detach_pid(p, PIDTYPE_PID);
  67        if (thread_group_leader(p)) {
  68                detach_pid(p, PIDTYPE_PGID);
  69                detach_pid(p, PIDTYPE_SID);
  70
  71                list_del_rcu(&p->tasks);
  72                __get_cpu_var(process_counts)--;
  73        }
  74        list_del_rcu(&p->thread_group);
  75        list_del_init(&p->sibling);
  76}
  77
  78/*
  79 * This function expects the tasklist_lock write-locked.
  80 */
  81static void __exit_signal(struct task_struct *tsk)
  82{
  83        struct signal_struct *sig = tsk->signal;
  84        struct sighand_struct *sighand;
  85
  86        BUG_ON(!sig);
  87        BUG_ON(!atomic_read(&sig->count));
  88
  89        sighand = rcu_dereference(tsk->sighand);
  90        spin_lock(&sighand->siglock);
  91
  92        posix_cpu_timers_exit(tsk);
  93        if (atomic_dec_and_test(&sig->count))
  94                posix_cpu_timers_exit_group(tsk);
  95        else {
  96                /*
  97                 * If there is any task waiting for the group exit
  98                 * then notify it:
  99                 */
 100                if (sig->group_exit_task && atomic_read(&sig->count) == sig->notify_count)
 101                        wake_up_process(sig->group_exit_task);
 102
 103                if (tsk == sig->curr_target)
 104                        sig->curr_target = next_thread(tsk);
 105                /*
 106                 * Accumulate here the counters for all threads but the
 107                 * group leader as they die, so they can be added into
 108                 * the process-wide totals when those are taken.
 109                 * The group leader stays around as a zombie as long
 110                 * as there are other threads.  When it gets reaped,
 111                 * the exit.c code will add its counts into these totals.
 112                 * We won't ever get here for the group leader, since it
 113                 * will have been the last reference on the signal_struct.
 114                 */
 115                sig->gtime = cputime_add(sig->gtime, task_gtime(tsk));
 116                sig->min_flt += tsk->min_flt;
 117                sig->maj_flt += tsk->maj_flt;
 118                sig->nvcsw += tsk->nvcsw;
 119                sig->nivcsw += tsk->nivcsw;
 120                sig->inblock += task_io_get_inblock(tsk);
 121                sig->oublock += task_io_get_oublock(tsk);
 122                task_io_accounting_add(&sig->ioac, &tsk->ioac);
 123                sig = NULL; /* Marker for below. */
 124        }
 125
 126        __unhash_process(tsk);
 127
 128        /*
 129         * Do this under ->siglock, we can race with another thread
 130         * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals.
 131         */
 132        flush_sigqueue(&tsk->pending);
 133
 134        tsk->signal = NULL;
 135        tsk->sighand = NULL;
 136        spin_unlock(&sighand->siglock);
 137
 138        __cleanup_sighand(sighand);
 139        clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
 140        if (sig) {
 141                flush_sigqueue(&sig->shared_pending);
 142                taskstats_tgid_free(sig);
 143                /*
 144                 * Make sure ->signal can't go away under rq->lock,
 145                 * see account_group_exec_runtime().
 146                 */
 147                task_rq_unlock_wait(tsk);
 148                __cleanup_signal(sig);
 149        }
 150}
 151
 152static void delayed_put_task_struct(struct rcu_head *rhp)
 153{
 154        struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
 155
 156        trace_sched_process_free(tsk);
 157        put_task_struct(tsk);
 158}
 159
 160
 161void release_task(struct task_struct * p)
 162{
 163        struct task_struct *leader;
 164        int zap_leader;
 165repeat:
 166        tracehook_prepare_release_task(p);
 167        atomic_dec(&p->user->processes);
 168        proc_flush_task(p);
 169        write_lock_irq(&tasklist_lock);
 170        tracehook_finish_release_task(p);
 171        __exit_signal(p);
 172
 173        /*
 174         * If we are the last non-leader member of the thread
 175         * group, and the leader is zombie, then notify the
 176         * group leader's parent process. (if it wants notification.)
 177         */
 178        zap_leader = 0;
 179        leader = p->group_leader;
 180        if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
 181                BUG_ON(task_detached(leader));
 182                do_notify_parent(leader, leader->exit_signal);
 183                /*
 184                 * If we were the last child thread and the leader has
 185                 * exited already, and the leader's parent ignores SIGCHLD,
 186                 * then we are the one who should release the leader.
 187                 *
 188                 * do_notify_parent() will have marked it self-reaping in
 189                 * that case.
 190                 */
 191                zap_leader = task_detached(leader);
 192
 193                /*
 194                 * This maintains the invariant that release_task()
 195                 * only runs on a task in EXIT_DEAD, just for sanity.
 196                 */
 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 int has_stopped_jobs(struct pid *pgrp)
 269{
 270        int retval = 0;
 271        struct task_struct *p;
 272
 273        do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
 274                if (!task_is_stopped(p))
 275                        continue;
 276                retval = 1;
 277                break;
 278        } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
 279        return retval;
 280}
 281
 282/*
 283 * Check to see if any process groups have become orphaned as
 284 * a result of our exiting, and if they have any stopped jobs,
 285 * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
 286 */
 287static void
 288kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent)
 289{
 290        struct pid *pgrp = task_pgrp(tsk);
 291        struct task_struct *ignored_task = tsk;
 292
 293        if (!parent)
 294                 /* exit: our father is in a different pgrp than
 295                  * we are and we were the only connection outside.
 296                  */
 297                parent = tsk->real_parent;
 298        else
 299                /* reparent: our child is in a different pgrp than
 300                 * we are, and it was the only connection outside.
 301                 */
 302                ignored_task = NULL;
 303
 304        if (task_pgrp(parent) != pgrp &&
 305            task_session(parent) == task_session(tsk) &&
 306            will_become_orphaned_pgrp(pgrp, ignored_task) &&
 307            has_stopped_jobs(pgrp)) {
 308                __kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
 309                __kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
 310        }
 311}
 312
 313/**
 314 * reparent_to_kthreadd - Reparent the calling kernel thread to kthreadd
 315 *
 316 * If a kernel thread is launched as a result of a system call, or if
 317 * it ever exits, it should generally reparent itself to kthreadd so it
 318 * isn't in the way of other processes and is correctly cleaned up on exit.
 319 *
 320 * The various task state such as scheduling policy and priority may have
 321 * been inherited from a user process, so we reset them to sane values here.
 322 *
 323 * NOTE that reparent_to_kthreadd() gives the caller full capabilities.
 324 */
 325static void reparent_to_kthreadd(void)
 326{
 327        write_lock_irq(&tasklist_lock);
 328
 329        ptrace_unlink(current);
 330        /* Reparent to init */
 331        current->real_parent = current->parent = kthreadd_task;
 332        list_move_tail(&current->sibling, &current->real_parent->children);
 333
 334        /* Set the exit signal to SIGCHLD so we signal init on exit */
 335        current->exit_signal = SIGCHLD;
 336
 337        if (task_nice(current) < 0)
 338                set_user_nice(current, 0);
 339        /* cpus_allowed? */
 340        /* rt_priority? */
 341        /* signals? */
 342        security_task_reparent_to_init(current);
 343        memcpy(current->signal->rlim, init_task.signal->rlim,
 344               sizeof(current->signal->rlim));
 345        atomic_inc(&(INIT_USER->__count));
 346        write_unlock_irq(&tasklist_lock);
 347        switch_uid(INIT_USER);
 348}
 349
 350void __set_special_pids(struct pid *pid)
 351{
 352        struct task_struct *curr = current->group_leader;
 353        pid_t nr = pid_nr(pid);
 354
 355        if (task_session(curr) != pid) {
 356                change_pid(curr, PIDTYPE_SID, pid);
 357                set_task_session(curr, nr);
 358        }
 359        if (task_pgrp(curr) != pid) {
 360                change_pid(curr, PIDTYPE_PGID, pid);
 361                set_task_pgrp(curr, nr);
 362        }
 363}
 364
 365static void set_special_pids(struct pid *pid)
 366{
 367        write_lock_irq(&tasklist_lock);
 368        __set_special_pids(pid);
 369        write_unlock_irq(&tasklist_lock);
 370}
 371
 372/*
 373 * Let kernel threads use this to say that they
 374 * allow a certain signal (since daemonize() will
 375 * have disabled all of them by default).
 376 */
 377int allow_signal(int sig)
 378{
 379        if (!valid_signal(sig) || sig < 1)
 380                return -EINVAL;
 381
 382        spin_lock_irq(&current->sighand->siglock);
 383        sigdelset(&current->blocked, sig);
 384        if (!current->mm) {
 385                /* Kernel threads handle their own signals.
 386                   Let the signal code know it'll be handled, so
 387                   that they don't get converted to SIGKILL or
 388                   just silently dropped */
 389                current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2;
 390        }
 391        recalc_sigpending();
 392        spin_unlock_irq(&current->sighand->siglock);
 393        return 0;
 394}
 395
 396EXPORT_SYMBOL(allow_signal);
 397
 398int disallow_signal(int sig)
 399{
 400        if (!valid_signal(sig) || sig < 1)
 401                return -EINVAL;
 402
 403        spin_lock_irq(&current->sighand->siglock);
 404        current->sighand->action[(sig)-1].sa.sa_handler = SIG_IGN;
 405        recalc_sigpending();
 406        spin_unlock_irq(&current->sighand->siglock);
 407        return 0;
 408}
 409
 410EXPORT_SYMBOL(disallow_signal);
 411
 412/*
 413 *      Put all the gunge required to become a kernel thread without
 414 *      attached user resources in one place where it belongs.
 415 */
 416
 417void daemonize(const char *name, ...)
 418{
 419        va_list args;
 420        struct fs_struct *fs;
 421        sigset_t blocked;
 422
 423        va_start(args, name);
 424        vsnprintf(current->comm, sizeof(current->comm), name, args);
 425        va_end(args);
 426
 427        /*
 428         * If we were started as result of loading a module, close all of the
 429         * user space pages.  We don't need them, and if we didn't close them
 430         * they would be locked into memory.
 431         */
 432        exit_mm(current);
 433        /*
 434         * We don't want to have TIF_FREEZE set if the system-wide hibernation
 435         * or suspend transition begins right now.
 436         */
 437        current->flags |= (PF_NOFREEZE | PF_KTHREAD);
 438
 439        if (current->nsproxy != &init_nsproxy) {
 440                get_nsproxy(&init_nsproxy);
 441                switch_task_namespaces(current, &init_nsproxy);
 442        }
 443        set_special_pids(&init_struct_pid);
 444        proc_clear_tty(current);
 445
 446        /* Block and flush all signals */
 447        sigfillset(&blocked);
 448        sigprocmask(SIG_BLOCK, &blocked, NULL);
 449        flush_signals(current);
 450
 451        /* Become as one with the init task */
 452
 453        exit_fs(current);       /* current->fs->count--; */
 454        fs = init_task.fs;
 455        current->fs = fs;
 456        atomic_inc(&fs->count);
 457
 458        exit_files(current);
 459        current->files = init_task.files;
 460        atomic_inc(&current->files->count);
 461
 462        reparent_to_kthreadd();
 463}
 464
 465EXPORT_SYMBOL(daemonize);
 466
 467static void close_files(struct files_struct * files)
 468{
 469        int i, j;
 470        struct fdtable *fdt;
 471
 472        j = 0;
 473
 474        /*
 475         * It is safe to dereference the fd table without RCU or
 476         * ->file_lock because this is the last reference to the
 477         * files structure.
 478         */
 479        fdt = files_fdtable(files);
 480        for (;;) {
 481                unsigned long set;
 482                i = j * __NFDBITS;
 483                if (i >= fdt->max_fds)
 484                        break;
 485                set = fdt->open_fds->fds_bits[j++];
 486                while (set) {
 487                        if (set & 1) {
 488                                struct file * file = xchg(&fdt->fd[i], NULL);
 489                                if (file) {
 490                                        filp_close(file, files);
 491                                        cond_resched();
 492                                }
 493                        }
 494                        i++;
 495                        set >>= 1;
 496                }
 497        }
 498}
 499
 500struct files_struct *get_files_struct(struct task_struct *task)
 501{
 502        struct files_struct *files;
 503
 504        task_lock(task);
 505        files = task->files;
 506        if (files)
 507                atomic_inc(&files->count);
 508        task_unlock(task);
 509
 510        return files;
 511}
 512
 513void put_files_struct(struct files_struct *files)
 514{
 515        struct fdtable *fdt;
 516
 517        if (atomic_dec_and_test(&files->count)) {
 518                close_files(files);
 519                /*
 520                 * Free the fd and fdset arrays if we expanded them.
 521                 * If the fdtable was embedded, pass files for freeing
 522                 * at the end of the RCU grace period. Otherwise,
 523                 * you can free files immediately.
 524                 */
 525                fdt = files_fdtable(files);
 526                if (fdt != &files->fdtab)
 527                        kmem_cache_free(files_cachep, files);
 528                free_fdtable(fdt);
 529        }
 530}
 531
 532void reset_files_struct(struct files_struct *files)
 533{
 534        struct task_struct *tsk = current;
 535        struct files_struct *old;
 536
 537        old = tsk->files;
 538        task_lock(tsk);
 539        tsk->files = files;
 540        task_unlock(tsk);
 541        put_files_struct(old);
 542}
 543
 544void exit_files(struct task_struct *tsk)
 545{
 546        struct files_struct * files = tsk->files;
 547
 548        if (files) {
 549                task_lock(tsk);
 550                tsk->files = NULL;
 551                task_unlock(tsk);
 552                put_files_struct(files);
 553        }
 554}
 555
 556void put_fs_struct(struct fs_struct *fs)
 557{
 558        /* No need to hold fs->lock if we are killing it */
 559        if (atomic_dec_and_test(&fs->count)) {
 560                path_put(&fs->root);
 561                path_put(&fs->pwd);
 562                kmem_cache_free(fs_cachep, fs);
 563        }
 564}
 565
 566void exit_fs(struct task_struct *tsk)
 567{
 568        struct fs_struct * fs = tsk->fs;
 569
 570        if (fs) {
 571                task_lock(tsk);
 572                tsk->fs = NULL;
 573                task_unlock(tsk);
 574                put_fs_struct(fs);
 575        }
 576}
 577
 578EXPORT_SYMBOL_GPL(exit_fs);
 579
 580#ifdef CONFIG_MM_OWNER
 581/*
 582 * Task p is exiting and it owned mm, lets find a new owner for it
 583 */
 584static inline int
 585mm_need_new_owner(struct mm_struct *mm, struct task_struct *p)
 586{
 587        /*
 588         * If there are other users of the mm and the owner (us) is exiting
 589         * we need to find a new owner to take on the responsibility.
 590         */
 591        if (atomic_read(&mm->mm_users) <= 1)
 592                return 0;
 593        if (mm->owner != p)
 594                return 0;
 595        return 1;
 596}
 597
 598void mm_update_next_owner(struct mm_struct *mm)
 599{
 600        struct task_struct *c, *g, *p = current;
 601
 602retry:
 603        if (!mm_need_new_owner(mm, p))
 604                return;
 605
 606        read_lock(&tasklist_lock);
 607        /*
 608         * Search in the children
 609         */
 610        list_for_each_entry(c, &p->children, sibling) {
 611                if (c->mm == mm)
 612                        goto assign_new_owner;
 613        }
 614
 615        /*
 616         * Search in the siblings
 617         */
 618        list_for_each_entry(c, &p->parent->children, sibling) {
 619                if (c->mm == mm)
 620                        goto assign_new_owner;
 621        }
 622
 623        /*
 624         * Search through everything else. We should not get
 625         * here often
 626         */
 627        do_each_thread(g, c) {
 628                if (c->mm == mm)
 629                        goto assign_new_owner;
 630        } while_each_thread(g, c);
 631
 632        read_unlock(&tasklist_lock);
 633        /*
 634         * We found no owner yet mm_users > 1: this implies that we are
 635         * most likely racing with swapoff (try_to_unuse()) or /proc or
 636         * ptrace or page migration (get_task_mm()).  Mark owner as NULL,
 637         * so that subsystems can understand the callback and take action.
 638         */
 639        down_write(&mm->mmap_sem);
 640        cgroup_mm_owner_callbacks(mm->owner, NULL);
 641        mm->owner = NULL;
 642        up_write(&mm->mmap_sem);
 643        return;
 644
 645assign_new_owner:
 646        BUG_ON(c == p);
 647        get_task_struct(c);
 648        read_unlock(&tasklist_lock);
 649        down_write(&mm->mmap_sem);
 650        /*
 651         * The task_lock protects c->mm from changing.
 652         * We always want mm->owner->mm == mm
 653         */
 654        task_lock(c);
 655        if (c->mm != mm) {
 656                task_unlock(c);
 657                up_write(&mm->mmap_sem);
 658                put_task_struct(c);
 659                goto retry;
 660        }
 661        cgroup_mm_owner_callbacks(mm->owner, c);
 662        mm->owner = c;
 663        task_unlock(c);
 664        up_write(&mm->mmap_sem);
 665        put_task_struct(c);
 666}
 667#endif /* CONFIG_MM_OWNER */
 668
 669/*
 670 * Turn us into a lazy TLB process if we
 671 * aren't already..
 672 */
 673static void exit_mm(struct task_struct * tsk)
 674{
 675        struct mm_struct *mm = tsk->mm;
 676        struct core_state *core_state;
 677
 678        mm_release(tsk, mm);
 679        if (!mm)
 680                return;
 681        /*
 682         * Serialize with any possible pending coredump.
 683         * We must hold mmap_sem around checking core_state
 684         * and clearing tsk->mm.  The core-inducing thread
 685         * will increment ->nr_threads for each thread in the
 686         * group with ->mm != NULL.
 687         */
 688        down_read(&mm->mmap_sem);
 689        core_state = mm->core_state;
 690        if (core_state) {
 691                struct core_thread self;
 692                up_read(&mm->mmap_sem);
 693
 694                self.task = tsk;
 695                self.next = xchg(&core_state->dumper.next, &self);
 696                /*
 697                 * Implies mb(), the result of xchg() must be visible
 698                 * to core_state->dumper.
 699                 */
 700                if (atomic_dec_and_test(&core_state->nr_threads))
 701                        complete(&core_state->startup);
 702
 703                for (;;) {
 704                        set_task_state(tsk, TASK_UNINTERRUPTIBLE);
 705                        if (!self.task) /* see coredump_finish() */
 706                                break;
 707                        schedule();
 708                }
 709                __set_task_state(tsk, TASK_RUNNING);
 710                down_read(&mm->mmap_sem);
 711        }
 712        atomic_inc(&mm->mm_count);
 713        BUG_ON(mm != tsk->active_mm);
 714        /* more a memory barrier than a real lock */
 715        task_lock(tsk);
 716        tsk->mm = NULL;
 717        up_read(&mm->mmap_sem);
 718        enter_lazy_tlb(mm, current);
 719        /* We don't want this task to be frozen prematurely */
 720        clear_freeze_flag(tsk);
 721        task_unlock(tsk);
 722        mm_update_next_owner(mm);
 723        mmput(mm);
 724}
 725
 726/*
 727 * Return nonzero if @parent's children should reap themselves.
 728 *
 729 * Called with write_lock_irq(&tasklist_lock) held.
 730 */
 731static int ignoring_children(struct task_struct *parent)
 732{
 733        int ret;
 734        struct sighand_struct *psig = parent->sighand;
 735        unsigned long flags;
 736        spin_lock_irqsave(&psig->siglock, flags);
 737        ret = (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN ||
 738               (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT));
 739        spin_unlock_irqrestore(&psig->siglock, flags);
 740        return ret;
 741}
 742
 743/*
 744 * Detach all tasks we were using ptrace on.
 745 * Any that need to be release_task'd are put on the @dead list.
 746 *
 747 * Called with write_lock(&tasklist_lock) held.
 748 */
 749static void ptrace_exit(struct task_struct *parent, struct list_head *dead)
 750{
 751        struct task_struct *p, *n;
 752        int ign = -1;
 753
 754        list_for_each_entry_safe(p, n, &parent->ptraced, ptrace_entry) {
 755                __ptrace_unlink(p);
 756
 757                if (p->exit_state != EXIT_ZOMBIE)
 758                        continue;
 759
 760                /*
 761                 * If it's a zombie, our attachedness prevented normal
 762                 * parent notification or self-reaping.  Do notification
 763                 * now if it would have happened earlier.  If it should
 764                 * reap itself, add it to the @dead list.  We can't call
 765                 * release_task() here because we already hold tasklist_lock.
 766                 *
 767                 * If it's our own child, there is no notification to do.
 768                 * But if our normal children self-reap, then this child
 769                 * was prevented by ptrace and we must reap it now.
 770                 */
 771                if (!task_detached(p) && thread_group_empty(p)) {
 772                        if (!same_thread_group(p->real_parent, parent))
 773                                do_notify_parent(p, p->exit_signal);
 774                        else {
 775                                if (ign < 0)
 776                                        ign = ignoring_children(parent);
 777                                if (ign)
 778                                        p->exit_signal = -1;
 779                        }
 780                }
 781
 782                if (task_detached(p)) {
 783                        /*
 784                         * Mark it as in the process of being reaped.
 785                         */
 786                        p->exit_state = EXIT_DEAD;
 787                        list_add(&p->ptrace_entry, dead);
 788                }
 789        }
 790}
 791
 792/*
 793 * Finish up exit-time ptrace cleanup.
 794 *
 795 * Called without locks.
 796 */
 797static void ptrace_exit_finish(struct task_struct *parent,
 798                               struct list_head *dead)
 799{
 800        struct task_struct *p, *n;
 801
 802        BUG_ON(!list_empty(&parent->ptraced));
 803
 804        list_for_each_entry_safe(p, n, dead, ptrace_entry) {
 805                list_del_init(&p->ptrace_entry);
 806                release_task(p);
 807        }
 808}
 809
 810static void reparent_thread(struct task_struct *p, struct task_struct *father)
 811{
 812        if (p->pdeath_signal)
 813                /* We already hold the tasklist_lock here.  */
 814                group_send_sig_info(p->pdeath_signal, SEND_SIG_NOINFO, p);
 815
 816        list_move_tail(&p->sibling, &p->real_parent->children);
 817
 818        /* If this is a threaded reparent there is no need to
 819         * notify anyone anything has happened.
 820         */
 821        if (same_thread_group(p->real_parent, father))
 822                return;
 823
 824        /* We don't want people slaying init.  */
 825        if (!task_detached(p))
 826                p->exit_signal = SIGCHLD;
 827
 828        /* If we'd notified the old parent about this child's death,
 829         * also notify the new parent.
 830         */
 831        if (!ptrace_reparented(p) &&
 832            p->exit_state == EXIT_ZOMBIE &&
 833            !task_detached(p) && thread_group_empty(p))
 834                do_notify_parent(p, p->exit_signal);
 835
 836        kill_orphaned_pgrp(p, father);
 837}
 838
 839/*
 840 * When we die, we re-parent all our children.
 841 * Try to give them to another thread in our thread
 842 * group, and if no such member exists, give it to
 843 * the child reaper process (ie "init") in our pid
 844 * space.
 845 */
 846static struct task_struct *find_new_reaper(struct task_struct *father)
 847{
 848        struct pid_namespace *pid_ns = task_active_pid_ns(father);
 849        struct task_struct *thread;
 850
 851        thread = father;
 852        while_each_thread(father, thread) {
 853                if (thread->flags & PF_EXITING)
 854                        continue;
 855                if (unlikely(pid_ns->child_reaper == father))
 856                        pid_ns->child_reaper = thread;
 857                return thread;
 858        }
 859
 860        if (unlikely(pid_ns->child_reaper == father)) {
 861                write_unlock_irq(&tasklist_lock);
 862                if (unlikely(pid_ns == &init_pid_ns))
 863                        panic("Attempted to kill init!");
 864
 865                zap_pid_ns_processes(pid_ns);
 866                write_lock_irq(&tasklist_lock);
 867                /*
 868                 * We can not clear ->child_reaper or leave it alone.
 869                 * There may by stealth EXIT_DEAD tasks on ->children,
 870                 * forget_original_parent() must move them somewhere.
 871                 */
 872                pid_ns->child_reaper = init_pid_ns.child_reaper;
 873        }
 874
 875        return pid_ns->child_reaper;
 876}
 877
 878static void forget_original_parent(struct task_struct *father)
 879{
 880        struct task_struct *p, *n, *reaper;
 881        LIST_HEAD(ptrace_dead);
 882
 883        write_lock_irq(&tasklist_lock);
 884        reaper = find_new_reaper(father);
 885        /*
 886         * First clean up ptrace if we were using it.
 887         */
 888        ptrace_exit(father, &ptrace_dead);
 889
 890        list_for_each_entry_safe(p, n, &father->children, sibling) {
 891                p->real_parent = reaper;
 892                if (p->parent == father) {
 893                        BUG_ON(p->ptrace);
 894                        p->parent = p->real_parent;
 895                }
 896                reparent_thread(p, father);
 897        }
 898
 899        write_unlock_irq(&tasklist_lock);
 900        BUG_ON(!list_empty(&father->children));
 901
 902        ptrace_exit_finish(father, &ptrace_dead);
 903}
 904
 905/*
 906 * Send signals to all our closest relatives so that they know
 907 * to properly mourn us..
 908 */
 909static void exit_notify(struct task_struct *tsk, int group_dead)
 910{
 911        int signal;
 912        void *cookie;
 913
 914        /*
 915         * This does two things:
 916         *
 917         * A.  Make init inherit all the child processes
 918         * B.  Check to see if any process groups have become orphaned
 919         *      as a result of our exiting, and if they have any stopped
 920         *      jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
 921         */
 922        forget_original_parent(tsk);
 923        exit_task_namespaces(tsk);
 924
 925        write_lock_irq(&tasklist_lock);
 926        if (group_dead)
 927                kill_orphaned_pgrp(tsk->group_leader, NULL);
 928
 929        /* Let father know we died
 930         *
 931         * Thread signals are configurable, but you aren't going to use
 932         * that to send signals to arbitary processes.
 933         * That stops right now.
 934         *
 935         * If the parent exec id doesn't match the exec id we saved
 936         * when we started then we know the parent has changed security
 937         * domain.
 938         *
 939         * If our self_exec id doesn't match our parent_exec_id then
 940         * we have changed execution domain as these two values started
 941         * the same after a fork.
 942         */
 943        if (tsk->exit_signal != SIGCHLD && !task_detached(tsk) &&
 944            (tsk->parent_exec_id != tsk->real_parent->self_exec_id ||
 945             tsk->self_exec_id != tsk->parent_exec_id) &&
 946            !capable(CAP_KILL))
 947                tsk->exit_signal = SIGCHLD;
 948
 949        signal = tracehook_notify_death(tsk, &cookie, group_dead);
 950        if (signal >= 0)
 951                signal = do_notify_parent(tsk, signal);
 952
 953        tsk->exit_state = signal == DEATH_REAP ? EXIT_DEAD : EXIT_ZOMBIE;
 954
 955        /* mt-exec, de_thread() is waiting for us */
 956        if (thread_group_leader(tsk) &&
 957            tsk->signal->group_exit_task &&
 958            tsk->signal->notify_count < 0)
 959                wake_up_process(tsk->signal->group_exit_task);
 960
 961        write_unlock_irq(&tasklist_lock);
 962
 963        tracehook_report_death(tsk, signal, cookie, group_dead);
 964
 965        /* If the process is dead, release it - nobody will wait for it */
 966        if (signal == DEATH_REAP)
 967                release_task(tsk);
 968}
 969
 970#ifdef CONFIG_DEBUG_STACK_USAGE
 971static void check_stack_usage(void)
 972{
 973        static DEFINE_SPINLOCK(low_water_lock);
 974        static int lowest_to_date = THREAD_SIZE;
 975        unsigned long *n = end_of_stack(current);
 976        unsigned long free;
 977
 978        while (*n == 0)
 979                n++;
 980        free = (unsigned long)n - (unsigned long)end_of_stack(current);
 981
 982        if (free >= lowest_to_date)
 983                return;
 984
 985        spin_lock(&low_water_lock);
 986        if (free < lowest_to_date) {
 987                printk(KERN_WARNING "%s used greatest stack depth: %lu bytes "
 988                                "left\n",
 989                                current->comm, free);
 990                lowest_to_date = free;
 991        }
 992        spin_unlock(&low_water_lock);
 993}
 994#else
 995static inline void check_stack_usage(void) {}
 996#endif
 997
 998NORET_TYPE void do_exit(long code)
 999{
1000        struct task_struct *tsk = current;
1001        int group_dead;
1002
1003        profile_task_exit(tsk);
1004
1005        WARN_ON(atomic_read(&tsk->fs_excl));
1006
1007        if (unlikely(in_interrupt()))
1008                panic("Aiee, killing interrupt handler!");
1009        if (unlikely(!tsk->pid))
1010                panic("Attempted to kill the idle task!");
1011
1012        tracehook_report_exit(&code);
1013
1014        /*
1015         * We're taking recursive faults here in do_exit. Safest is to just
1016         * leave this task alone and wait for reboot.
1017         */
1018        if (unlikely(tsk->flags & PF_EXITING)) {
1019                printk(KERN_ALERT
1020                        "Fixing recursive fault but reboot is needed!\n");
1021                /*
1022                 * We can do this unlocked here. The futex code uses
1023                 * this flag just to verify whether the pi state
1024                 * cleanup has been done or not. In the worst case it
1025                 * loops once more. We pretend that the cleanup was
1026                 * done as there is no way to return. Either the
1027                 * OWNER_DIED bit is set by now or we push the blocked
1028                 * task into the wait for ever nirwana as well.
1029                 */
1030                tsk->flags |= PF_EXITPIDONE;
1031                if (tsk->io_context)
1032                        exit_io_context();
1033                set_current_state(TASK_UNINTERRUPTIBLE);
1034                schedule();
1035        }
1036
1037        exit_signals(tsk);  /* sets PF_EXITING */
1038        /*
1039         * tsk->flags are checked in the futex code to protect against
1040         * an exiting task cleaning up the robust pi futexes.
1041         */
1042        smp_mb();
1043        spin_unlock_wait(&tsk->pi_lock);
1044
1045        if (unlikely(in_atomic()))
1046                printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
1047                                current->comm, task_pid_nr(current),
1048                                preempt_count());
1049
1050        acct_update_integrals(tsk);
1051        if (tsk->mm) {
1052                update_hiwater_rss(tsk->mm);
1053                update_hiwater_vm(tsk->mm);
1054        }
1055        group_dead = atomic_dec_and_test(&tsk->signal->live);
1056        if (group_dead) {
1057                hrtimer_cancel(&tsk->signal->real_timer);
1058                exit_itimers(tsk->signal);
1059        }
1060        acct_collect(code, group_dead);
1061        if (group_dead)
1062                tty_audit_exit();
1063        if (unlikely(tsk->audit_context))
1064                audit_free(tsk);
1065
1066        tsk->exit_code = code;
1067        taskstats_exit(tsk, group_dead);
1068
1069        exit_mm(tsk);
1070
1071        if (group_dead)
1072                acct_process();
1073        trace_sched_process_exit(tsk);
1074
1075        exit_sem(tsk);
1076        exit_files(tsk);
1077        exit_fs(tsk);
1078        check_stack_usage();
1079        exit_thread();
1080        cgroup_exit(tsk, 1);
1081        exit_keys(tsk);
1082
1083        if (group_dead && tsk->signal->leader)
1084                disassociate_ctty(1);
1085
1086        module_put(task_thread_info(tsk)->exec_domain->module);
1087        if (tsk->binfmt)
1088                module_put(tsk->binfmt->module);
1089
1090        proc_exit_connector(tsk);
1091        exit_notify(tsk, group_dead);
1092#ifdef CONFIG_NUMA
1093        mpol_put(tsk->mempolicy);
1094        tsk->mempolicy = NULL;
1095#endif
1096#ifdef CONFIG_FUTEX
1097        /*
1098         * This must happen late, after the PID is not
1099         * hashed anymore:
1100         */
1101        if (unlikely(!list_empty(&tsk->pi_state_list)))
1102                exit_pi_state_list(tsk);
1103        if (unlikely(current->pi_state_cache))
1104                kfree(current->pi_state_cache);
1105#endif
1106        /*
1107         * Make sure we are holding no locks:
1108         */
1109        debug_check_no_locks_held(tsk);
1110        /*
1111         * We can do this unlocked here. The futex code uses this flag
1112         * just to verify whether the pi state cleanup has been done
1113         * or not. In the worst case it loops once more.
1114         */
1115        tsk->flags |= PF_EXITPIDONE;
1116
1117        if (tsk->io_context)
1118                exit_io_context();
1119
1120        if (tsk->splice_pipe)
1121                __free_pipe_info(tsk->splice_pipe);
1122
1123        preempt_disable();
1124        /* causes final put_task_struct in finish_task_switch(). */
1125        tsk->state = TASK_DEAD;
1126
1127        schedule();
1128        BUG();
1129        /* Avoid "noreturn function does return".  */
1130        for (;;)
1131                cpu_relax();    /* For when BUG is null */
1132}
1133
1134EXPORT_SYMBOL_GPL(do_exit);
1135
1136NORET_TYPE void complete_and_exit(struct completion *comp, long code)
1137{
1138        if (comp)
1139                complete(comp);
1140
1141        do_exit(code);
1142}
1143
1144EXPORT_SYMBOL(complete_and_exit);
1145
1146asmlinkage long sys_exit(int error_code)
1147{
1148        do_exit((error_code&0xff)<<8);
1149}
1150
1151/*
1152 * Take down every thread in the group.  This is called by fatal signals
1153 * as well as by sys_exit_group (below).
1154 */
1155NORET_TYPE void
1156do_group_exit(int exit_code)
1157{
1158        struct signal_struct *sig = current->signal;
1159
1160        BUG_ON(exit_code & 0x80); /* core dumps don't get here */
1161
1162        if (signal_group_exit(sig))
1163                exit_code = sig->group_exit_code;
1164        else if (!thread_group_empty(current)) {
1165                struct sighand_struct *const sighand = current->sighand;
1166                spin_lock_irq(&sighand->siglock);
1167                if (signal_group_exit(sig))
1168                        /* Another thread got here before we took the lock.  */
1169                        exit_code = sig->group_exit_code;
1170                else {
1171                        sig->group_exit_code = exit_code;
1172                        sig->flags = SIGNAL_GROUP_EXIT;
1173                        zap_other_threads(current);
1174                }
1175                spin_unlock_irq(&sighand->siglock);
1176        }
1177
1178        do_exit(exit_code);
1179        /* NOTREACHED */
1180}
1181
1182/*
1183 * this kills every thread in the thread group. Note that any externally
1184 * wait4()-ing process will get the correct exit code - even if this
1185 * thread is not the thread group leader.
1186 */
1187asmlinkage void sys_exit_group(int error_code)
1188{
1189        do_group_exit((error_code & 0xff) << 8);
1190}
1191
1192static struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
1193{
1194        struct pid *pid = NULL;
1195        if (type == PIDTYPE_PID)
1196                pid = task->pids[type].pid;
1197        else if (type < PIDTYPE_MAX)
1198                pid = task->group_leader->pids[type].pid;
1199        return pid;
1200}
1201
1202static int eligible_child(enum pid_type type, struct pid *pid, int options,
1203                          struct task_struct *p)
1204{
1205        int err;
1206
1207        if (type < PIDTYPE_MAX) {
1208                if (task_pid_type(p, type) != pid)
1209                        return 0;
1210        }
1211
1212        /* Wait for all children (clone and not) if __WALL is set;
1213         * otherwise, wait for clone children *only* if __WCLONE is
1214         * set; otherwise, wait for non-clone children *only*.  (Note:
1215         * A "clone" child here is one that reports to its parent
1216         * using a signal other than SIGCHLD.) */
1217        if (((p->exit_signal != SIGCHLD) ^ ((options & __WCLONE) != 0))
1218            && !(options & __WALL))
1219                return 0;
1220
1221        err = security_task_wait(p);
1222        if (err)
1223                return err;
1224
1225        return 1;
1226}
1227
1228static int wait_noreap_copyout(struct task_struct *p, pid_t pid, uid_t uid,
1229                               int why, int status,
1230                               struct siginfo __user *infop,
1231                               struct rusage __user *rusagep)
1232{
1233        int retval = rusagep ? getrusage(p, RUSAGE_BOTH, rusagep) : 0;
1234
1235        put_task_struct(p);
1236        if (!retval)
1237                retval = put_user(SIGCHLD, &infop->si_signo);
1238        if (!retval)
1239                retval = put_user(0, &infop->si_errno);
1240        if (!retval)
1241                retval = put_user((short)why, &infop->si_code);
1242        if (!retval)
1243                retval = put_user(pid, &infop->si_pid);
1244        if (!retval)
1245                retval = put_user(uid, &infop->si_uid);
1246        if (!retval)
1247                retval = put_user(status, &infop->si_status);
1248        if (!retval)
1249                retval = pid;
1250        return retval;
1251}
1252
1253/*
1254 * Handle sys_wait4 work for one task in state EXIT_ZOMBIE.  We hold
1255 * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1256 * the lock and this task is uninteresting.  If we return nonzero, we have
1257 * released the lock and the system call should return.
1258 */
1259static int wait_task_zombie(struct task_struct *p, int options,
1260                            struct siginfo __user *infop,
1261                            int __user *stat_addr, struct rusage __user *ru)
1262{
1263        unsigned long state;
1264        int retval, status, traced;
1265        pid_t pid = task_pid_vnr(p);
1266
1267        if (!likely(options & WEXITED))
1268                return 0;
1269
1270        if (unlikely(options & WNOWAIT)) {
1271                uid_t uid = p->uid;
1272                int exit_code = p->exit_code;
1273                int why, status;
1274
1275                get_task_struct(p);
1276                read_unlock(&tasklist_lock);
1277                if ((exit_code & 0x7f) == 0) {
1278                        why = CLD_EXITED;
1279                        status = exit_code >> 8;
1280                } else {
1281                        why = (exit_code & 0x80) ? CLD_DUMPED : CLD_KILLED;
1282                        status = exit_code & 0x7f;
1283                }
1284                return wait_noreap_copyout(p, pid, uid, why,
1285                                           status, infop, ru);
1286        }
1287
1288        /*
1289         * Try to move the task's state to DEAD
1290         * only one thread is allowed to do this:
1291         */
1292        state = xchg(&p->exit_state, EXIT_DEAD);
1293        if (state != EXIT_ZOMBIE) {
1294                BUG_ON(state != EXIT_DEAD);
1295                return 0;
1296        }
1297
1298        traced = ptrace_reparented(p);
1299
1300        if (likely(!traced)) {
1301                struct signal_struct *psig;
1302                struct signal_struct *sig;
1303                struct task_cputime cputime;
1304
1305                /*
1306                 * The resource counters for the group leader are in its
1307                 * own task_struct.  Those for dead threads in the group
1308                 * are in its signal_struct, as are those for the child
1309                 * processes it has previously reaped.  All these
1310                 * accumulate in the parent's signal_struct c* fields.
1311                 *
1312                 * We don't bother to take a lock here to protect these
1313                 * p->signal fields, because they are only touched by
1314                 * __exit_signal, which runs with tasklist_lock
1315                 * write-locked anyway, and so is excluded here.  We do
1316                 * need to protect the access to p->parent->signal fields,
1317                 * as other threads in the parent group can be right
1318                 * here reaping other children at the same time.
1319                 *
1320                 * We use thread_group_cputime() to get times for the thread
1321                 * group, which consolidates times for all threads in the
1322                 * group including the group leader.
1323                 */
1324                spin_lock_irq(&p->parent->sighand->siglock);
1325                psig = p->parent->signal;
1326                sig = p->signal;
1327                thread_group_cputime(p, &cputime);
1328                psig->cutime =
1329                        cputime_add(psig->cutime,
1330                        cputime_add(cputime.utime,
1331                                    sig->cutime));
1332                psig->cstime =
1333                        cputime_add(psig->cstime,
1334                        cputime_add(cputime.stime,
1335                                    sig->cstime));
1336                psig->cgtime =
1337                        cputime_add(psig->cgtime,
1338                        cputime_add(p->gtime,
1339                        cputime_add(sig->gtime,
1340                                    sig->cgtime)));
1341                psig->cmin_flt +=
1342                        p->min_flt + sig->min_flt + sig->cmin_flt;
1343                psig->cmaj_flt +=
1344                        p->maj_flt + sig->maj_flt + sig->cmaj_flt;
1345                psig->cnvcsw +=
1346                        p->nvcsw + sig->nvcsw + sig->cnvcsw;
1347                psig->cnivcsw +=
1348                        p->nivcsw + sig->nivcsw + sig->cnivcsw;
1349                psig->cinblock +=
1350                        task_io_get_inblock(p) +
1351                        sig->inblock + sig->cinblock;
1352                psig->coublock +=
1353                        task_io_get_oublock(p) +
1354                        sig->oublock + sig->coublock;
1355                task_io_accounting_add(&psig->ioac, &p->ioac);
1356                task_io_accounting_add(&psig->ioac, &sig->ioac);
1357                spin_unlock_irq(&p->parent->sighand->siglock);
1358        }
1359
1360        /*
1361         * Now we are sure this task is interesting, and no other
1362         * thread can reap it because we set its state to EXIT_DEAD.
1363         */
1364        read_unlock(&tasklist_lock);
1365
1366        retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
1367        status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1368                ? p->signal->group_exit_code : p->exit_code;
1369        if (!retval && stat_addr)
1370                retval = put_user(status, stat_addr);
1371        if (!retval && infop)
1372                retval = put_user(SIGCHLD, &infop->si_signo);
1373        if (!retval && infop)
1374                retval = put_user(0, &infop->si_errno);
1375        if (!retval && infop) {
1376                int why;
1377
1378                if ((status & 0x7f) == 0) {
1379                        why = CLD_EXITED;
1380                        status >>= 8;
1381                } else {
1382                        why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
1383                        status &= 0x7f;
1384                }
1385                retval = put_user((short)why, &infop->si_code);
1386                if (!retval)
1387                        retval = put_user(status, &infop->si_status);
1388        }
1389        if (!retval && infop)
1390                retval = put_user(pid, &infop->si_pid);
1391        if (!retval && infop)
1392                retval = put_user(p->uid, &infop->si_uid);
1393        if (!retval)
1394                retval = pid;
1395
1396        if (traced) {
1397                write_lock_irq(&tasklist_lock);
1398                /* We dropped tasklist, ptracer could die and untrace */
1399                ptrace_unlink(p);
1400                /*
1401                 * If this is not a detached task, notify the parent.
1402                 * If it's still not detached after that, don't release
1403                 * it now.
1404                 */
1405                if (!task_detached(p)) {
1406                        do_notify_parent(p, p->exit_signal);
1407                        if (!task_detached(p)) {
1408                                p->exit_state = EXIT_ZOMBIE;
1409                                p = NULL;
1410                        }
1411                }
1412                write_unlock_irq(&tasklist_lock);
1413        }
1414        if (p != NULL)
1415                release_task(p);
1416
1417        return retval;
1418}
1419
1420/*
1421 * Handle sys_wait4 work for one task in state TASK_STOPPED.  We hold
1422 * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1423 * the lock and this task is uninteresting.  If we return nonzero, we have
1424 * released the lock and the system call should return.
1425 */
1426static int wait_task_stopped(int ptrace, struct task_struct *p,
1427                             int options, struct siginfo __user *infop,
1428                             int __user *stat_addr, struct rusage __user *ru)
1429{
1430        int retval, exit_code, why;
1431        uid_t uid = 0; /* unneeded, required by compiler */
1432        pid_t pid;
1433
1434        if (!(options & WUNTRACED))
1435                return 0;
1436
1437        exit_code = 0;
1438        spin_lock_irq(&p->sighand->siglock);
1439
1440        if (unlikely(!task_is_stopped_or_traced(p)))
1441                goto unlock_sig;
1442
1443        if (!ptrace && p->signal->group_stop_count > 0)
1444                /*
1445                 * A group stop is in progress and this is the group leader.
1446                 * We won't report until all threads have stopped.
1447                 */
1448                goto unlock_sig;
1449
1450        exit_code = p->exit_code;
1451        if (!exit_code)
1452                goto unlock_sig;
1453
1454        if (!unlikely(options & WNOWAIT))
1455                p->exit_code = 0;
1456
1457        uid = p->uid;
1458unlock_sig:
1459        spin_unlock_irq(&p->sighand->siglock);
1460        if (!exit_code)
1461                return 0;
1462
1463        /*
1464         * Now we are pretty sure this task is interesting.
1465         * Make sure it doesn't get reaped out from under us while we
1466         * give up the lock and then examine it below.  We don't want to
1467         * keep holding onto the tasklist_lock while we call getrusage and
1468         * possibly take page faults for user memory.
1469         */
1470        get_task_struct(p);
1471        pid = task_pid_vnr(p);
1472        why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
1473        read_unlock(&tasklist_lock);
1474
1475        if (unlikely(options & WNOWAIT))
1476                return wait_noreap_copyout(p, pid, uid,
1477                                           why, exit_code,
1478                                           infop, ru);
1479
1480        retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
1481        if (!retval && stat_addr)
1482                retval = put_user((exit_code << 8) | 0x7f, stat_addr);
1483        if (!retval && infop)
1484                retval = put_user(SIGCHLD, &infop->si_signo);
1485        if (!retval && infop)
1486                retval = put_user(0, &infop->si_errno);
1487        if (!retval && infop)
1488                retval = put_user((short)why, &infop->si_code);
1489        if (!retval && infop)
1490                retval = put_user(exit_code, &infop->si_status);
1491        if (!retval && infop)
1492                retval = put_user(pid, &infop->si_pid);
1493        if (!retval && infop)
1494                retval = put_user(uid, &infop->si_uid);
1495        if (!retval)
1496                retval = pid;
1497        put_task_struct(p);
1498
1499        BUG_ON(!retval);
1500        return retval;
1501}
1502
1503/*
1504 * Handle do_wait work for one task in a live, non-stopped state.
1505 * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1506 * the lock and this task is uninteresting.  If we return nonzero, we have
1507 * released the lock and the system call should return.
1508 */
1509static int wait_task_continued(struct task_struct *p, int options,
1510                               struct siginfo __user *infop,
1511                               int __user *stat_addr, struct rusage __user *ru)
1512{
1513        int retval;
1514        pid_t pid;
1515        uid_t uid;
1516
1517        if (!unlikely(options & WCONTINUED))
1518                return 0;
1519
1520        if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
1521                return 0;
1522
1523        spin_lock_irq(&p->sighand->siglock);
1524        /* Re-check with the lock held.  */
1525        if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
1526                spin_unlock_irq(&p->sighand->siglock);
1527                return 0;
1528        }
1529        if (!unlikely(options & WNOWAIT))
1530                p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1531        spin_unlock_irq(&p->sighand->siglock);
1532
1533        pid = task_pid_vnr(p);
1534        uid = p->uid;
1535        get_task_struct(p);
1536        read_unlock(&tasklist_lock);
1537
1538        if (!infop) {
1539                retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
1540                put_task_struct(p);
1541                if (!retval && stat_addr)
1542                        retval = put_user(0xffff, stat_addr);
1543                if (!retval)
1544                        retval = pid;
1545        } else {
1546                retval = wait_noreap_copyout(p, pid, uid,
1547                                             CLD_CONTINUED, SIGCONT,
1548                                             infop, ru);
1549                BUG_ON(retval == 0);
1550        }
1551
1552        return retval;
1553}
1554
1555/*
1556 * Consider @p for a wait by @parent.
1557 *
1558 * -ECHILD should be in *@notask_error before the first call.
1559 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1560 * Returns zero if the search for a child should continue;
1561 * then *@notask_error is 0 if @p is an eligible child,
1562 * or another error from security_task_wait(), or still -ECHILD.
1563 */
1564static int wait_consider_task(struct task_struct *parent, int ptrace,
1565                              struct task_struct *p, int *notask_error,
1566                              enum pid_type type, struct pid *pid, int options,
1567                              struct siginfo __user *infop,
1568                              int __user *stat_addr, struct rusage __user *ru)
1569{
1570        int ret = eligible_child(type, pid, options, p);
1571        if (!ret)
1572                return ret;
1573
1574        if (unlikely(ret < 0)) {
1575                /*
1576                 * If we have not yet seen any eligible child,
1577                 * then let this error code replace -ECHILD.
1578                 * A permission error will give the user a clue
1579                 * to look for security policy problems, rather
1580                 * than for mysterious wait bugs.
1581                 */
1582                if (*notask_error)
1583                        *notask_error = ret;
1584        }
1585
1586        if (likely(!ptrace) && unlikely(p->ptrace)) {
1587                /*
1588                 * This child is hidden by ptrace.
1589                 * We aren't allowed to see it now, but eventually we will.
1590                 */
1591                *notask_error = 0;
1592                return 0;
1593        }
1594
1595        if (p->exit_state == EXIT_DEAD)
1596                return 0;
1597
1598        /*
1599         * We don't reap group leaders with subthreads.
1600         */
1601        if (p->exit_state == EXIT_ZOMBIE && !delay_group_leader(p))
1602                return wait_task_zombie(p, options, infop, stat_addr, ru);
1603
1604        /*
1605         * It's stopped or running now, so it might
1606         * later continue, exit, or stop again.
1607         */
1608        *notask_error = 0;
1609
1610        if (task_is_stopped_or_traced(p))
1611                return wait_task_stopped(ptrace, p, options,
1612                                         infop, stat_addr, ru);
1613
1614        return wait_task_continued(p, options, infop, stat_addr, ru);
1615}
1616
1617/*
1618 * Do the work of do_wait() for one thread in the group, @tsk.
1619 *
1620 * -ECHILD should be in *@notask_error before the first call.
1621 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1622 * Returns zero if the search for a child should continue; then
1623 * *@notask_error is 0 if there were any eligible children,
1624 * or another error from security_task_wait(), or still -ECHILD.
1625 */
1626static int do_wait_thread(struct task_struct *tsk, int *notask_error,
1627                          enum pid_type type, struct pid *pid, int options,
1628                          struct siginfo __user *infop, int __user *stat_addr,
1629                          struct rusage __user *ru)
1630{
1631        struct task_struct *p;
1632
1633        list_for_each_entry(p, &tsk->children, sibling) {
1634                /*
1635                 * Do not consider detached threads.
1636                 */
1637                if (!task_detached(p)) {
1638                        int ret = wait_consider_task(tsk, 0, p, notask_error,
1639                                                     type, pid, options,
1640                                                     infop, stat_addr, ru);
1641                        if (ret)
1642                                return ret;
1643                }
1644        }
1645
1646        return 0;
1647}
1648
1649static int ptrace_do_wait(struct task_struct *tsk, int *notask_error,
1650                          enum pid_type type, struct pid *pid, int options,
1651                          struct siginfo __user *infop, int __user *stat_addr,
1652                          struct rusage __user *ru)
1653{
1654        struct task_struct *p;
1655
1656        /*
1657         * Traditionally we see ptrace'd stopped tasks regardless of options.
1658         */
1659        options |= WUNTRACED;
1660
1661        list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
1662                int ret = wait_consider_task(tsk, 1, p, notask_error,
1663                                             type, pid, options,
1664                                             infop, stat_addr, ru);
1665                if (ret)
1666                        return ret;
1667        }
1668
1669        return 0;
1670}
1671
1672static long do_wait(enum pid_type type, struct pid *pid, int options,
1673                    struct siginfo __user *infop, int __user *stat_addr,
1674                    struct rusage __user *ru)
1675{
1676        DECLARE_WAITQUEUE(wait, current);
1677        struct task_struct *tsk;
1678        int retval;
1679
1680        trace_sched_process_wait(pid);
1681
1682        add_wait_queue(&current->signal->wait_chldexit,&wait);
1683repeat:
1684        /*
1685         * If there is nothing that can match our critiera just get out.
1686         * We will clear @retval to zero if we see any child that might later
1687         * match our criteria, even if we are not able to reap it yet.
1688         */
1689        retval = -ECHILD;
1690        if ((type < PIDTYPE_MAX) && (!pid || hlist_empty(&pid->tasks[type])))
1691                goto end;
1692
1693        current->state = TASK_INTERRUPTIBLE;
1694        read_lock(&tasklist_lock);
1695        tsk = current;
1696        do {
1697                int tsk_result = do_wait_thread(tsk, &retval,
1698                                                type, pid, options,
1699                                                infop, stat_addr, ru);
1700                if (!tsk_result)
1701                        tsk_result = ptrace_do_wait(tsk, &retval,
1702                                                    type, pid, options,
1703                                                    infop, stat_addr, ru);
1704                if (tsk_result) {
1705                        /*
1706                         * tasklist_lock is unlocked and we have a final result.
1707                         */
1708                        retval = tsk_result;
1709                        goto end;
1710                }
1711
1712                if (options & __WNOTHREAD)
1713                        break;
1714                tsk = next_thread(tsk);
1715                BUG_ON(tsk->signal != current->signal);
1716        } while (tsk != current);
1717        read_unlock(&tasklist_lock);
1718
1719        if (!retval && !(options & WNOHANG)) {
1720                retval = -ERESTARTSYS;
1721                if (!signal_pending(current)) {
1722                        schedule();
1723                        goto repeat;
1724                }
1725        }
1726
1727end:
1728        current->state = TASK_RUNNING;
1729        remove_wait_queue(&current->signal->wait_chldexit,&wait);
1730        if (infop) {
1731                if (retval > 0)
1732                        retval = 0;
1733                else {
1734                        /*
1735                         * For a WNOHANG return, clear out all the fields
1736                         * we would set so the user can easily tell the
1737                         * difference.
1738                         */
1739                        if (!retval)
1740                                retval = put_user(0, &infop->si_signo);
1741                        if (!retval)
1742                                retval = put_user(0, &infop->si_errno);
1743                        if (!retval)
1744                                retval = put_user(0, &infop->si_code);
1745                        if (!retval)
1746                                retval = put_user(0, &infop->si_pid);
1747                        if (!retval)
1748                                retval = put_user(0, &infop->si_uid);
1749                        if (!retval)
1750                                retval = put_user(0, &infop->si_status);
1751                }
1752        }
1753        return retval;
1754}
1755
1756asmlinkage long sys_waitid(int which, pid_t upid,
1757                           struct siginfo __user *infop, int options,
1758                           struct rusage __user *ru)
1759{
1760        struct pid *pid = NULL;
1761        enum pid_type type;
1762        long ret;
1763
1764        if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED))
1765                return -EINVAL;
1766        if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
1767                return -EINVAL;
1768
1769        switch (which) {
1770        case P_ALL:
1771                type = PIDTYPE_MAX;
1772                break;
1773        case P_PID:
1774                type = PIDTYPE_PID;
1775                if (upid <= 0)
1776                        return -EINVAL;
1777                break;
1778        case P_PGID:
1779                type = PIDTYPE_PGID;
1780                if (upid <= 0)
1781                        return -EINVAL;
1782                break;
1783        default:
1784                return -EINVAL;
1785        }
1786
1787        if (type < PIDTYPE_MAX)
1788                pid = find_get_pid(upid);
1789        ret = do_wait(type, pid, options, infop, NULL, ru);
1790        put_pid(pid);
1791
1792        /* avoid REGPARM breakage on x86: */
1793        asmlinkage_protect(5, ret, which, upid, infop, options, ru);
1794        return ret;
1795}
1796
1797asmlinkage long sys_wait4(pid_t upid, int __user *stat_addr,
1798                          int options, struct rusage __user *ru)
1799{
1800        struct pid *pid = NULL;
1801        enum pid_type type;
1802        long ret;
1803
1804        if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
1805                        __WNOTHREAD|__WCLONE|__WALL))
1806                return -EINVAL;
1807
1808        if (upid == -1)
1809                type = PIDTYPE_MAX;
1810        else if (upid < 0) {
1811                type = PIDTYPE_PGID;
1812                pid = find_get_pid(-upid);
1813        } else if (upid == 0) {
1814                type = PIDTYPE_PGID;
1815                pid = get_pid(task_pgrp(current));
1816        } else /* upid > 0 */ {
1817                type = PIDTYPE_PID;
1818                pid = find_get_pid(upid);
1819        }
1820
1821        ret = do_wait(type, pid, options | WEXITED, NULL, stat_addr, ru);
1822        put_pid(pid);
1823
1824        /* avoid REGPARM breakage on x86: */
1825        asmlinkage_protect(4, ret, upid, stat_addr, options, ru);
1826        return ret;
1827}
1828
1829#ifdef __ARCH_WANT_SYS_WAITPID
1830
1831/*
1832 * sys_waitpid() remains for compatibility. waitpid() should be
1833 * implemented by calling sys_wait4() from libc.a.
1834 */
1835asmlinkage long sys_waitpid(pid_t pid, int __user *stat_addr, int options)
1836{
1837        return sys_wait4(pid, stat_addr, options, NULL);
1838}
1839
1840#endif
1841
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