kernel/exit.c

   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/smp_lock.h>
  11 #include <linux/module.h>
  12 #include <linux/capability.h>
  13 #include <linux/completion.h>
  14 #include <linux/personality.h>
  15 #include <linux/tty.h>
  16 #include <linux/namespace.h>
  17 #include <linux/key.h>
  18 #include <linux/security.h>
  19 #include <linux/cpu.h>
  20 #include <linux/acct.h>
  21 #include <linux/file.h>
  22 #include <linux/binfmts.h>
  23 #include <linux/ptrace.h>
  24 #include <linux/profile.h>
  25 #include <linux/mount.h>
  26 #include <linux/proc_fs.h>
  27 #include <linux/mempolicy.h>
  28 #include <linux/cpuset.h>
  29 #include <linux/syscalls.h>
  30 #include <linux/signal.h>
  31 #include <linux/posix-timers.h>
  32 #include <linux/cn_proc.h>
  33 #include <linux/mutex.h>
  34 #include <linux/futex.h>
  35 #include <linux/compat.h>
  36 #include <linux/pipe_fs_i.h>
  37 #include <linux/audit.h> /* for audit_free() */
  38 #include <linux/resource.h>
  39
  40 #include <asm/uaccess.h>
  41 #include <asm/unistd.h>
  42 #include <asm/pgtable.h>
  43 #include <asm/mmu_context.h>
  44
  45 extern void sem_exit (void);
  46 extern struct task_struct *child_reaper;
  47
  48 static void exit_mm(struct task_struct * tsk);
  49
  50 static void __unhash_process(struct task_struct *p)
  51 {
  52         nr_threads--;
  53         detach_pid(p, PIDTYPE_PID);
  54         if (thread_group_leader(p)) {
  55                 detach_pid(p, PIDTYPE_PGID);
  56                 detach_pid(p, PIDTYPE_SID);
  57
  58                 list_del_rcu(&p->tasks);
  59                 __get_cpu_var(process_counts)--;
  60         }
  61         list_del_rcu(&p->thread_group);
  62         remove_parent(p);
  63 }
  64
  65 /*
  66  * This function expects the tasklist_lock write-locked.
  67  */
  68 static void __exit_signal(struct task_struct *tsk)
  69 {
  70         struct signal_struct *sig = tsk->signal;
  71         struct sighand_struct *sighand;
  72
  73         BUG_ON(!sig);
  74         BUG_ON(!atomic_read(&sig->count));
  75
  76         rcu_read_lock();
  77         sighand = rcu_dereference(tsk->sighand);
  78         spin_lock(&sighand->siglock);
  79
  80         posix_cpu_timers_exit(tsk);
  81         if (atomic_dec_and_test(&sig->count))
  82                 posix_cpu_timers_exit_group(tsk);
  83         else {
  84                 /*
  85                  * If there is any task waiting for the group exit
  86                  * then notify it:
  87                  */
  88                 if (sig->group_exit_task && atomic_read(&sig->count) == sig->notify_count) {
  89                         wake_up_process(sig->group_exit_task);
  90                         sig->group_exit_task = NULL;
  91                 }
  92                 if (tsk == sig->curr_target)
  93                         sig->curr_target = next_thread(tsk);
  94                 /*
  95                  * Accumulate here the counters for all threads but the
  96                  * group leader as they die, so they can be added into
  97                  * the process-wide totals when those are taken.
  98                  * The group leader stays around as a zombie as long
  99                  * as there are other threads.  When it gets reaped,
 100                  * the exit.c code will add its counts into these totals.
 101                  * We won't ever get here for the group leader, since it
 102                  * will have been the last reference on the signal_struct.
 103                  */
 104                 sig->utime = cputime_add(sig->utime, tsk->utime);
 105                 sig->stime = cputime_add(sig->stime, tsk->stime);
 106                 sig->min_flt += tsk->min_flt;
 107                 sig->maj_flt += tsk->maj_flt;
 108                 sig->nvcsw += tsk->nvcsw;
 109                 sig->nivcsw += tsk->nivcsw;
 110                 sig->sched_time += tsk->sched_time;
 111                 sig = NULL; /* Marker for below. */
 112         }
 113
 114         __unhash_process(tsk);
 115
 116         tsk->signal = NULL;
 117         tsk->sighand = NULL;
 118         spin_unlock(&sighand->siglock);
 119         rcu_read_unlock();
 120
 121         __cleanup_sighand(sighand);
 122         clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
 123         flush_sigqueue(&tsk->pending);
 124         if (sig) {
 125                 flush_sigqueue(&sig->shared_pending);
 126                 __cleanup_signal(sig);
 127         }
 128 }
 129
 130 static void delayed_put_task_struct(struct rcu_head *rhp)
 131 {
 132         put_task_struct(container_of(rhp, struct task_struct, rcu));
 133 }
 134
 135 void release_task(struct task_struct * p)
 136 {
 137         struct task_struct *leader;
 138         int zap_leader;
 139 repeat:
 140         atomic_dec(&p->user->processes);
 141         write_lock_irq(&tasklist_lock);
 142         ptrace_unlink(p);
 143         BUG_ON(!list_empty(&p->ptrace_list) || !list_empty(&p->ptrace_children));
 144         __exit_signal(p);
 145
 146         /*
 147          * If we are the last non-leader member of the thread
 148          * group, and the leader is zombie, then notify the
 149          * group leader's parent process. (if it wants notification.)
 150          */
 151         zap_leader = 0;
 152         leader = p->group_leader;
 153         if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
 154                 BUG_ON(leader->exit_signal == -1);
 155                 do_notify_parent(leader, leader->exit_signal);
 156                 /*
 157                  * If we were the last child thread and the leader has
 158                  * exited already, and the leader's parent ignores SIGCHLD,
 159                  * then we are the one who should release the leader.
 160                  *
 161                  * do_notify_parent() will have marked it self-reaping in
 162                  * that case.
 163                  */
 164                 zap_leader = (leader->exit_signal == -1);
 165         }
 166
 167         sched_exit(p);
 168         write_unlock_irq(&tasklist_lock);
 169         proc_flush_task(p);
 170         release_thread(p);
 171         call_rcu(&p->rcu, delayed_put_task_struct);
 172
 173         p = leader;
 174         if (unlikely(zap_leader))
 175                 goto repeat;
 176 }
 177
 178 /*
 179  * This checks not only the pgrp, but falls back on the pid if no
 180  * satisfactory pgrp is found. I dunno - gdb doesn't work correctly
 181  * without this...
 182  */
 183 int session_of_pgrp(int pgrp)
 184 {
 185         struct task_struct *p;
 186         int sid = -1;
 187
 188         read_lock(&tasklist_lock);
 189         do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
 190                 if (p->signal->session > 0) {
 191                         sid = p->signal->session;
 192                         goto out;
 193                 }
 194         } while_each_task_pid(pgrp, PIDTYPE_PGID, p);
 195         p = find_task_by_pid(pgrp);
 196         if (p)
 197                 sid = p->signal->session;
 198 out:
 199         read_unlock(&tasklist_lock);
 200
 201         return sid;
 202 }
 203
 204 /*
 205  * Determine if a process group is "orphaned", according to the POSIX
 206  * definition in 2.2.2.52.  Orphaned process groups are not to be affected
 207  * by terminal-generated stop signals.  Newly orphaned process groups are
 208  * to receive a SIGHUP and a SIGCONT.
 209  *
 210  * "I ask you, have you ever known what it is to be an orphan?"
 211  */
 212 static int will_become_orphaned_pgrp(int pgrp, struct task_struct *ignored_task)
 213 {
 214         struct task_struct *p;
 215         int ret = 1;
 216
 217         do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
 218                 if (p == ignored_task
 219                                 || p->exit_state
 220                                 || p->real_parent->pid == 1)
 221                         continue;
 222                 if (process_group(p->real_parent) != pgrp
 223                             && p->real_parent->signal->session == p->signal->session) {
 224                         ret = 0;
 225                         break;
 226                 }
 227         } while_each_task_pid(pgrp, PIDTYPE_PGID, p);
 228         return ret;     /* (sighing) "Often!" */
 229 }
 230
 231 int is_orphaned_pgrp(int pgrp)
 232 {
 233         int retval;
 234
 235         read_lock(&tasklist_lock);
 236         retval = will_become_orphaned_pgrp(pgrp, NULL);
 237         read_unlock(&tasklist_lock);
 238
 239         return retval;
 240 }
 241
 242 static int has_stopped_jobs(int pgrp)
 243 {
 244         int retval = 0;
 245         struct task_struct *p;
 246
 247         do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
 248                 if (p->state != TASK_STOPPED)
 249                         continue;
 250
 251                 /* If p is stopped by a debugger on a signal that won't
 252                    stop it, then don't count p as stopped.  This isn't
 253                    perfect but it's a good approximation.  */
 254                 if (unlikely (p->ptrace)
 255                     && p->exit_code != SIGSTOP
 256                     && p->exit_code != SIGTSTP
 257                     && p->exit_code != SIGTTOU
 258                     && p->exit_code != SIGTTIN)
 259                         continue;
 260
 261                 retval = 1;
 262                 break;
 263         } while_each_task_pid(pgrp, PIDTYPE_PGID, p);
 264         return retval;
 265 }
 266
 267 /**
 268  * reparent_to_init - Reparent the calling kernel thread to the init task.
 269  *
 270  * If a kernel thread is launched as a result of a system call, or if
 271  * it ever exits, it should generally reparent itself to init so that
 272  * it is correctly cleaned up on exit.
 273  *
 274  * The various task state such as scheduling policy and priority may have
 275  * been inherited from a user process, so we reset them to sane values here.
 276  *
 277  * NOTE that reparent_to_init() gives the caller full capabilities.
 278  */
 279 static void reparent_to_init(void)
 280 {
 281         write_lock_irq(&tasklist_lock);
 282
 283         ptrace_unlink(current);
 284         /* Reparent to init */
 285         remove_parent(current);
 286         current->parent = child_reaper;
 287         current->real_parent = child_reaper;
 288         add_parent(current);
 289
 290         /* Set the exit signal to SIGCHLD so we signal init on exit */
 291         current->exit_signal = SIGCHLD;
 292
 293         if ((current->policy == SCHED_NORMAL ||
 294                         current->policy == SCHED_BATCH)
 295                                 && (task_nice(current) < 0))
 296                 set_user_nice(current, 0);
 297         /* cpus_allowed? */
 298         /* rt_priority? */
 299         /* signals? */
 300         security_task_reparent_to_init(current);
 301         memcpy(current->signal->rlim, init_task.signal->rlim,
 302                sizeof(current->signal->rlim));
 303         atomic_inc(&(INIT_USER->__count));
 304         write_unlock_irq(&tasklist_lock);
 305         switch_uid(INIT_USER);
 306 }
 307
 308 void __set_special_pids(pid_t session, pid_t pgrp)
 309 {
 310         struct task_struct *curr = current->group_leader;
 311
 312         if (curr->signal->session != session) {
 313                 detach_pid(curr, PIDTYPE_SID);
 314                 curr->signal->session = session;
 315                 attach_pid(curr, PIDTYPE_SID, session);
 316         }
 317         if (process_group(curr) != pgrp) {
 318                 detach_pid(curr, PIDTYPE_PGID);
 319                 curr->signal->pgrp = pgrp;
 320                 attach_pid(curr, PIDTYPE_PGID, pgrp);
 321         }
 322 }
 323
 324 void set_special_pids(pid_t session, pid_t pgrp)
 325 {
 326         write_lock_irq(&tasklist_lock);
 327         __set_special_pids(session, pgrp);
 328         write_unlock_irq(&tasklist_lock);
 329 }
 330
 331 /*
 332  * Let kernel threads use this to say that they
 333  * allow a certain signal (since daemonize() will
 334  * have disabled all of them by default).
 335  */
 336 int allow_signal(int sig)
 337 {
 338         if (!valid_signal(sig) || sig < 1)
 339                 return -EINVAL;
 340
 341         spin_lock_irq(&current->sighand->siglock);
 342         sigdelset(&current->blocked, sig);
 343         if (!current->mm) {
 344                 /* Kernel threads handle their own signals.
 345                    Let the signal code know it'll be handled, so
 346                    that they don't get converted to SIGKILL or
 347                    just silently dropped */
 348                 current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2;
 349         }
 350         recalc_sigpending();
 351         spin_unlock_irq(&current->sighand->siglock);
 352         return 0;
 353 }
 354
 355 EXPORT_SYMBOL(allow_signal);
 356
 357 int disallow_signal(int sig)
 358 {
 359         if (!valid_signal(sig) || sig < 1)
 360                 return -EINVAL;
 361
 362         spin_lock_irq(&current->sighand->siglock);
 363         sigaddset(&current->blocked, sig);
 364         recalc_sigpending();
 365         spin_unlock_irq(&current->sighand->siglock);
 366         return 0;
 367 }
 368
 369 EXPORT_SYMBOL(disallow_signal);
 370
 371 /*
 372  *      Put all the gunge required to become a kernel thread without
 373  *      attached user resources in one place where it belongs.
 374  */
 375
 376 void daemonize(const char *name, ...)
 377 {
 378         va_list args;
 379         struct fs_struct *fs;
 380         sigset_t blocked;
 381
 382         va_start(args, name);
 383         vsnprintf(current->comm, sizeof(current->comm), name, args);
 384         va_end(args);
 385
 386         /*
 387          * If we were started as result of loading a module, close all of the
 388          * user space pages.  We don't need them, and if we didn't close them
 389          * they would be locked into memory.
 390          */
 391         exit_mm(current);
 392
 393         set_special_pids(1, 1);
 394         mutex_lock(&tty_mutex);
 395         current->signal->tty = NULL;
 396         mutex_unlock(&tty_mutex);
 397
 398         /* Block and flush all signals */
 399         sigfillset(&blocked);
 400         sigprocmask(SIG_BLOCK, &blocked, NULL);
 401         flush_signals(current);
 402
 403         /* Become as one with the init task */
 404
 405         exit_fs(current);       /* current->fs->count--; */
 406         fs = init_task.fs;
 407         current->fs = fs;
 408         atomic_inc(&fs->count);
 409         exit_namespace(current);
 410         current->namespace = init_task.namespace;
 411         get_namespace(current->namespace);
 412         exit_files(current);
 413         current->files = init_task.files;
 414         atomic_inc(&current->files->count);
 415
 416         reparent_to_init();
 417 }
 418
 419 EXPORT_SYMBOL(daemonize);
 420
 421 static void close_files(struct files_struct * files)
 422 {
 423         int i, j;
 424         struct fdtable *fdt;
 425
 426         j = 0;
 427
 428         /*
 429          * It is safe to dereference the fd table without RCU or
 430          * ->file_lock because this is the last reference to the
 431          * files structure.
 432          */
 433         fdt = files_fdtable(files);
 434         for (;;) {
 435                 unsigned long set;
 436                 i = j * __NFDBITS;
 437                 if (i >= fdt->max_fdset || i >= fdt->max_fds)
 438                         break;
 439                 set = fdt->open_fds->fds_bits[j++];
 440                 while (set) {
 441                         if (set & 1) {
 442                                 struct file * file = xchg(&fdt->fd[i], NULL);
 443                                 if (file)
 444                                         filp_close(file, files);
 445                         }
 446                         i++;
 447                         set >>= 1;
 448                 }
 449         }
 450 }
 451
 452 struct files_struct *get_files_struct(struct task_struct *task)
 453 {
 454         struct files_struct *files;
 455
 456         task_lock(task);
 457         files = task->files;
 458         if (files)
 459                 atomic_inc(&files->count);
 460         task_unlock(task);
 461
 462         return files;
 463 }
 464
 465 void fastcall put_files_struct(struct files_struct *files)
 466 {
 467         struct fdtable *fdt;
 468
 469         if (atomic_dec_and_test(&files->count)) {
 470                 close_files(files);
 471                 /*
 472                  * Free the fd and fdset arrays if we expanded them.
 473                  * If the fdtable was embedded, pass files for freeing
 474                  * at the end of the RCU grace period. Otherwise,
 475                  * you can free files immediately.
 476                  */
 477                 fdt = files_fdtable(files);
 478                 if (fdt == &files->fdtab)
 479                         fdt->free_files = files;
 480                 else
 481                         kmem_cache_free(files_cachep, files);
 482                 free_fdtable(fdt);
 483         }
 484 }
 485
 486 EXPORT_SYMBOL(put_files_struct);
 487
 488 static inline void __exit_files(struct task_struct *tsk)
 489 {
 490         struct files_struct * files = tsk->files;
 491
 492         if (files) {
 493                 task_lock(tsk);
 494                 tsk->files = NULL;
 495                 task_unlock(tsk);
 496                 put_files_struct(files);
 497         }
 498 }
 499
 500 void exit_files(struct task_struct *tsk)
 501 {
 502         __exit_files(tsk);
 503 }
 504
 505 static inline void __put_fs_struct(struct fs_struct *fs)
 506 {
 507         /* No need to hold fs->lock if we are killing it */
 508         if (atomic_dec_and_test(&fs->count)) {
 509                 dput(fs->root);
 510                 mntput(fs->rootmnt);
 511                 dput(fs->pwd);
 512                 mntput(fs->pwdmnt);
 513                 if (fs->altroot) {
 514                         dput(fs->altroot);
 515                         mntput(fs->altrootmnt);
 516                 }
 517                 kmem_cache_free(fs_cachep, fs);
 518         }
 519 }
 520
 521 void put_fs_struct(struct fs_struct *fs)
 522 {
 523         __put_fs_struct(fs);
 524 }
 525
 526 static inline void __exit_fs(struct task_struct *tsk)
 527 {
 528         struct fs_struct * fs = tsk->fs;
 529
 530         if (fs) {
 531                 task_lock(tsk);
 532                 tsk->fs = NULL;
 533                 task_unlock(tsk);
 534                 __put_fs_struct(fs);
 535         }
 536 }
 537
 538 void exit_fs(struct task_struct *tsk)
 539 {
 540         __exit_fs(tsk);
 541 }
 542
 543 EXPORT_SYMBOL_GPL(exit_fs);
 544
 545 /*
 546  * Turn us into a lazy TLB process if we
 547  * aren't already..
 548  */
 549 static void exit_mm(struct task_struct * tsk)
 550 {
 551         struct mm_struct *mm = tsk->mm;
 552
 553         mm_release(tsk, mm);
 554         if (!mm)
 555                 return;
 556         /*
 557          * Serialize with any possible pending coredump.
 558          * We must hold mmap_sem around checking core_waiters
 559          * and clearing tsk->mm.  The core-inducing thread
 560          * will increment core_waiters for each thread in the
 561          * group with ->mm != NULL.
 562          */
 563         down_read(&mm->mmap_sem);
 564         if (mm->core_waiters) {
 565                 up_read(&mm->mmap_sem);
 566                 down_write(&mm->mmap_sem);
 567                 if (!--mm->core_waiters)
 568                         complete(mm->core_startup_done);
 569                 up_write(&mm->mmap_sem);
 570
 571                 wait_for_completion(&mm->core_done);
 572                 down_read(&mm->mmap_sem);
 573         }
 574         atomic_inc(&mm->mm_count);
 575         BUG_ON(mm != tsk->active_mm);
 576         /* more a memory barrier than a real lock */
 577         task_lock(tsk);
 578         tsk->mm = NULL;
 579         up_read(&mm->mmap_sem);
 580         enter_lazy_tlb(mm, current);
 581         task_unlock(tsk);
 582         mmput(mm);
 583 }
 584
 585 static inline void
 586 choose_new_parent(struct task_struct *p, struct task_struct *reaper)
 587 {
 588         /*
 589          * Make sure we're not reparenting to ourselves and that
 590          * the parent is not a zombie.
 591          */
 592         BUG_ON(p == reaper || reaper->exit_state);
 593         p->real_parent = reaper;
 594 }
 595
 596 static void
 597 reparent_thread(struct task_struct *p, struct task_struct *father, int traced)
 598 {
 599         /* We don't want people slaying init.  */
 600         if (p->exit_signal != -1)
 601                 p->exit_signal = SIGCHLD;
 602
 603         if (p->pdeath_signal)
 604                 /* We already hold the tasklist_lock here.  */
 605                 group_send_sig_info(p->pdeath_signal, SEND_SIG_NOINFO, p);
 606
 607         /* Move the child from its dying parent to the new one.  */
 608         if (unlikely(traced)) {
 609                 /* Preserve ptrace links if someone else is tracing this child.  */
 610                 list_del_init(&p->ptrace_list);
 611                 if (p->parent != p->real_parent)
 612                         list_add(&p->ptrace_list, &p->real_parent->ptrace_children);
 613         } else {
 614                 /* If this child is being traced, then we're the one tracing it
 615                  * anyway, so let go of it.
 616                  */
 617                 p->ptrace = 0;
 618                 remove_parent(p);
 619                 p->parent = p->real_parent;
 620                 add_parent(p);
 621
 622                 /* If we'd notified the old parent about this child's death,
 623                  * also notify the new parent.
 624                  */
 625                 if (p->exit_state == EXIT_ZOMBIE && p->exit_signal != -1 &&
 626                     thread_group_empty(p))
 627                         do_notify_parent(p, p->exit_signal);
 628                 else if (p->state == TASK_TRACED) {
 629                         /*
 630                          * If it was at a trace stop, turn it into
 631                          * a normal stop since it's no longer being
 632                          * traced.
 633                          */
 634                         ptrace_untrace(p);
 635                 }
 636         }
 637
 638         /*
 639          * process group orphan check
 640          * Case ii: Our child is in a different pgrp
 641          * than we are, and it was the only connection
 642          * outside, so the child pgrp is now orphaned.
 643          */
 644         if ((process_group(p) != process_group(father)) &&
 645             (p->signal->session == father->signal->session)) {
 646                 int pgrp = process_group(p);
 647
 648                 if (will_become_orphaned_pgrp(pgrp, NULL) && has_stopped_jobs(pgrp)) {
 649                         __kill_pg_info(SIGHUP, SEND_SIG_PRIV, pgrp);
 650                         __kill_pg_info(SIGCONT, SEND_SIG_PRIV, pgrp);
 651                 }
 652         }
 653 }
 654
 655 /*
 656  * When we die, we re-parent all our children.
 657  * Try to give them to another thread in our thread
 658  * group, and if no such member exists, give it to
 659  * the global child reaper process (ie "init")
 660  */
 661 static void
 662 forget_original_parent(struct task_struct *father, struct list_head *to_release)
 663 {
 664         struct task_struct *p, *reaper = father;
 665         struct list_head *_p, *_n;
 666
 667         do {
 668                 reaper = next_thread(reaper);
 669                 if (reaper == father) {
 670                         reaper = child_reaper;
 671                         break;
 672                 }
 673         } while (reaper->exit_state);
 674
 675         /*
 676          * There are only two places where our children can be:
 677          *
 678          * - in our child list
 679          * - in our ptraced child list
 680          *
 681          * Search them and reparent children.
 682          */
 683         list_for_each_safe(_p, _n, &father->children) {
 684                 int ptrace;
 685                 p = list_entry(_p, struct task_struct, sibling);
 686
 687                 ptrace = p->ptrace;
 688
 689                 /* if father isn't the real parent, then ptrace must be enabled */
 690                 BUG_ON(father != p->real_parent && !ptrace);
 691
 692                 if (father == p->real_parent) {
 693                         /* reparent with a reaper, real father it's us */
 694                         choose_new_parent(p, reaper);
 695                         reparent_thread(p, father, 0);
 696                 } else {
 697                         /* reparent ptraced task to its real parent */
 698                         __ptrace_unlink (p);
 699                         if (p->exit_state == EXIT_ZOMBIE && p->exit_signal != -1 &&
 700                             thread_group_empty(p))
 701                                 do_notify_parent(p, p->exit_signal);
 702                 }
 703
 704                 /*
 705                  * if the ptraced child is a zombie with exit_signal == -1
 706                  * we must collect it before we exit, or it will remain
 707                  * zombie forever since we prevented it from self-reap itself
 708                  * while it was being traced by us, to be able to see it in wait4.
 709                  */
 710                 if (unlikely(ptrace && p->exit_state == EXIT_ZOMBIE && p->exit_signal == -1))
 711                         list_add(&p->ptrace_list, to_release);
 712         }
 713         list_for_each_safe(_p, _n, &father->ptrace_children) {
 714                 p = list_entry(_p, struct task_struct, ptrace_list);
 715                 choose_new_parent(p, reaper);
 716                 reparent_thread(p, father, 1);
 717         }
 718 }
 719
 720 /*
 721  * Send signals to all our closest relatives so that they know
 722  * to properly mourn us..
 723  */
 724 static void exit_notify(struct task_struct *tsk)
 725 {
 726         int state;
 727         struct task_struct *t;
 728         struct list_head ptrace_dead, *_p, *_n;
 729
 730         if (signal_pending(tsk) && !(tsk->signal->flags & SIGNAL_GROUP_EXIT)
 731             && !thread_group_empty(tsk)) {
 732                 /*
 733                  * This occurs when there was a race between our exit
 734                  * syscall and a group signal choosing us as the one to
 735                  * wake up.  It could be that we are the only thread
 736                  * alerted to check for pending signals, but another thread
 737                  * should be woken now to take the signal since we will not.
 738                  * Now we'll wake all the threads in the group just to make
 739                  * sure someone gets all the pending signals.
 740                  */
 741                 read_lock(&tasklist_lock);
 742                 spin_lock_irq(&tsk->sighand->siglock);
 743                 for (t = next_thread(tsk); t != tsk; t = next_thread(t))
 744                         if (!signal_pending(t) && !(t->flags & PF_EXITING)) {
 745                                 recalc_sigpending_tsk(t);
 746                                 if (signal_pending(t))
 747                                         signal_wake_up(t, 0);
 748                         }
 749                 spin_unlock_irq(&tsk->sighand->siglock);
 750                 read_unlock(&tasklist_lock);
 751         }
 752
 753         write_lock_irq(&tasklist_lock);
 754
 755         /*
 756          * This does two things:
 757          *
 758          * A.  Make init inherit all the child processes
 759          * B.  Check to see if any process groups have become orphaned
 760          *      as a result of our exiting, and if they have any stopped
 761          *      jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
 762          */
 763
 764         INIT_LIST_HEAD(&ptrace_dead);
 765         forget_original_parent(tsk, &ptrace_dead);
 766         BUG_ON(!list_empty(&tsk->children));
 767         BUG_ON(!list_empty(&tsk->ptrace_children));
 768
 769         /*
 770          * Check to see if any process groups have become orphaned
 771          * as a result of our exiting, and if they have any stopped
 772          * jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
 773          *
 774          * Case i: Our father is in a different pgrp than we are
 775          * and we were the only connection outside, so our pgrp
 776          * is about to become orphaned.
 777          */
 778
 779         t = tsk->real_parent;
 780
 781         if ((process_group(t) != process_group(tsk)) &&
 782             (t->signal->session == tsk->signal->session) &&
 783             will_become_orphaned_pgrp(process_group(tsk), tsk) &&
 784             has_stopped_jobs(process_group(tsk))) {
 785                 __kill_pg_info(SIGHUP, SEND_SIG_PRIV, process_group(tsk));
 786                 __kill_pg_info(SIGCONT, SEND_SIG_PRIV, process_group(tsk));
 787         }
 788
 789         /* Let father know we died
 790          *
 791          * Thread signals are configurable, but you aren't going to use
 792          * that to send signals to arbitary processes.
 793          * That stops right now.
 794          *
 795          * If the parent exec id doesn't match the exec id we saved
 796          * when we started then we know the parent has changed security
 797          * domain.
 798          *
 799          * If our self_exec id doesn't match our parent_exec_id then
 800          * we have changed execution domain as these two values started
 801          * the same after a fork.
 802          *
 803          */
 804
 805         if (tsk->exit_signal != SIGCHLD && tsk->exit_signal != -1 &&
 806             ( tsk->parent_exec_id != t->self_exec_id  ||
 807               tsk->self_exec_id != tsk->parent_exec_id)
 808             && !capable(CAP_KILL))
 809                 tsk->exit_signal = SIGCHLD;
 810
 811
 812         /* If something other than our normal parent is ptracing us, then
 813          * send it a SIGCHLD instead of honoring exit_signal.  exit_signal
 814          * only has special meaning to our real parent.
 815          */
 816         if (tsk->exit_signal != -1 && thread_group_empty(tsk)) {
 817                 int signal = tsk->parent == tsk->real_parent ? tsk->exit_signal : SIGCHLD;
 818                 do_notify_parent(tsk, signal);
 819         } else if (tsk->ptrace) {
 820                 do_notify_parent(tsk, SIGCHLD);
 821         }
 822
 823         state = EXIT_ZOMBIE;
 824         if (tsk->exit_signal == -1 &&
 825             (likely(tsk->ptrace == 0) ||
 826              unlikely(tsk->parent->signal->flags & SIGNAL_GROUP_EXIT)))
 827                 state = EXIT_DEAD;
 828         tsk->exit_state = state;
 829
 830         write_unlock_irq(&tasklist_lock);
 831
 832         list_for_each_safe(_p, _n, &ptrace_dead) {
 833                 list_del_init(_p);
 834                 t = list_entry(_p, struct task_struct, ptrace_list);
 835                 release_task(t);
 836         }
 837
 838         /* If the process is dead, release it - nobody will wait for it */
 839         if (state == EXIT_DEAD)
 840                 release_task(tsk);
 841 }
 842
 843 fastcall NORET_TYPE void do_exit(long code)
 844 {
 845         struct task_struct *tsk = current;
 846         int group_dead;
 847
 848         profile_task_exit(tsk);
 849
 850         WARN_ON(atomic_read(&tsk->fs_excl));
 851
 852         if (unlikely(in_interrupt()))
 853                 panic("Aiee, killing interrupt handler!");
 854         if (unlikely(!tsk->pid))
 855                 panic("Attempted to kill the idle task!");
 856         if (unlikely(tsk == child_reaper))
 857                 panic("Attempted to kill init!");
 858
 859         if (unlikely(current->ptrace & PT_TRACE_EXIT)) {
 860                 current->ptrace_message = code;
 861                 ptrace_notify((PTRACE_EVENT_EXIT << 8) | SIGTRAP);
 862         }
 863
 864         /*
 865          * We're taking recursive faults here in do_exit. Safest is to just
 866          * leave this task alone and wait for reboot.
 867          */
 868         if (unlikely(tsk->flags & PF_EXITING)) {
 869                 printk(KERN_ALERT
 870                         "Fixing recursive fault but reboot is needed!\n");
 871                 if (tsk->io_context)
 872                         exit_io_context();
 873                 set_current_state(TASK_UNINTERRUPTIBLE);
 874                 schedule();
 875         }
 876
 877         tsk->flags |= PF_EXITING;
 878
 879         if (unlikely(in_atomic()))
 880                 printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
 881                                 current->comm, current->pid,
 882                                 preempt_count());
 883
 884         acct_update_integrals(tsk);
 885         if (tsk->mm) {
 886                 update_hiwater_rss(tsk->mm);
 887                 update_hiwater_vm(tsk->mm);
 888         }
 889         group_dead = atomic_dec_and_test(&tsk->signal->live);
 890         if (group_dead) {
 891                 hrtimer_cancel(&tsk->signal->real_timer);
 892                 exit_itimers(tsk->signal);
 893         }
 894         acct_collect(code, group_dead);
 895         if (unlikely(tsk->robust_list))
 896                 exit_robust_list(tsk);
 897 #if defined(CONFIG_FUTEX) && defined(CONFIG_COMPAT)
 898         if (unlikely(tsk->compat_robust_list))
 899                 compat_exit_robust_list(tsk);
 900 #endif
 901         if (unlikely(tsk->audit_context))
 902                 audit_free(tsk);
 903         exit_mm(tsk);
 904
 905         if (group_dead)
 906                 acct_process();
 907         exit_sem(tsk);
 908         __exit_files(tsk);
 909         __exit_fs(tsk);
 910         exit_namespace(tsk);
 911         exit_thread();
 912         cpuset_exit(tsk);
 913         exit_keys(tsk);
 914
 915         if (group_dead && tsk->signal->leader)
 916                 disassociate_ctty(1);
 917
 918         module_put(task_thread_info(tsk)->exec_domain->module);
 919         if (tsk->binfmt)
 920                 module_put(tsk->binfmt->module);
 921
 922         tsk->exit_code = code;
 923         proc_exit_connector(tsk);
 924         exit_notify(tsk);
 925 #ifdef CONFIG_NUMA
 926         mpol_free(tsk->mempolicy);
 927         tsk->mempolicy = NULL;
 928 #endif
 929         /*
 930          * This must happen late, after the PID is not
 931          * hashed anymore:
 932          */
 933         if (unlikely(!list_empty(&tsk->pi_state_list)))
 934                 exit_pi_state_list(tsk);
 935         if (unlikely(current->pi_state_cache))
 936                 kfree(current->pi_state_cache);
 937         /*
 938          * Make sure we are holding no locks:
 939          */
 940         debug_check_no_locks_held(tsk);
 941
 942         if (tsk->io_context)
 943                 exit_io_context();
 944
 945         if (tsk->splice_pipe)
 946                 __free_pipe_info(tsk->splice_pipe);
 947
 948         /* PF_DEAD causes final put_task_struct after we schedule. */
 949         preempt_disable();
 950         BUG_ON(tsk->flags & PF_DEAD);
 951         tsk->flags |= PF_DEAD;
 952
 953         schedule();
 954         BUG();
 955         /* Avoid "noreturn function does return".  */
 956         for (;;) ;
 957 }
 958
 959 EXPORT_SYMBOL_GPL(do_exit);
 960
 961 NORET_TYPE void complete_and_exit(struct completion *comp, long code)
 962 {
 963         if (comp)
 964                 complete(comp);
 965
 966         do_exit(code);
 967 }
 968
 969 EXPORT_SYMBOL(complete_and_exit);
 970
 971 asmlinkage long sys_exit(int error_code)
 972 {
 973         do_exit((error_code&0xff)<<8);
 974 }
 975
 976 /*
 977  * Take down every thread in the group.  This is called by fatal signals
 978  * as well as by sys_exit_group (below).
 979  */
 980 NORET_TYPE void
 981 do_group_exit(int exit_code)
 982 {
 983         BUG_ON(exit_code & 0x80); /* core dumps don't get here */
 984
 985         if (current->signal->flags & SIGNAL_GROUP_EXIT)
 986                 exit_code = current->signal->group_exit_code;
 987         else if (!thread_group_empty(current)) {
 988                 struct signal_struct *const sig = current->signal;
 989                 struct sighand_struct *const sighand = current->sighand;
 990                 spin_lock_irq(&sighand->siglock);
 991                 if (sig->flags & SIGNAL_GROUP_EXIT)
 992                         /* Another thread got here before we took the lock.  */
 993                         exit_code = sig->group_exit_code;
 994                 else {
 995                         sig->group_exit_code = exit_code;
 996                         zap_other_threads(current);
 997                 }
 998                 spin_unlock_irq(&sighand->siglock);
 999         }
1000
1001         do_exit(exit_code);
1002         /* NOTREACHED */
1003 }
1004
1005 /*
1006  * this kills every thread in the thread group. Note that any externally
1007  * wait4()-ing process will get the correct exit code - even if this
1008  * thread is not the thread group leader.
1009  */
1010 asmlinkage void sys_exit_group(int error_code)
1011 {
1012         do_group_exit((error_code & 0xff) << 8);
1013 }
1014
1015 static int eligible_child(pid_t pid, int options, struct task_struct *p)
1016 {
1017         if (pid > 0) {
1018                 if (p->pid != pid)
1019                         return 0;
1020         } else if (!pid) {
1021                 if (process_group(p) != process_group(current))
1022                         return 0;
1023         } else if (pid != -1) {
1024                 if (process_group(p) != -pid)
1025                         return 0;
1026         }
1027
1028         /*
1029          * Do not consider detached threads that are
1030          * not ptraced:
1031          */
1032         if (p->exit_signal == -1 && !p->ptrace)
1033                 return 0;
1034
1035         /* Wait for all children (clone and not) if __WALL is set;
1036          * otherwise, wait for clone children *only* if __WCLONE is
1037          * set; otherwise, wait for non-clone children *only*.  (Note:
1038          * A "clone" child here is one that reports to its parent
1039          * using a signal other than SIGCHLD.) */
1040         if (((p->exit_signal != SIGCHLD) ^ ((options & __WCLONE) != 0))
1041             && !(options & __WALL))
1042                 return 0;
1043         /*
1044          * Do not consider thread group leaders that are
1045          * in a non-empty thread group:
1046          */
1047         if (current->tgid != p->tgid && delay_group_leader(p))
1048                 return 2;
1049
1050         if (security_task_wait(p))
1051                 return 0;
1052
1053         return 1;
1054 }
1055
1056 static int wait_noreap_copyout(struct task_struct *p, pid_t pid, uid_t uid,
1057                                int why, int status,
1058                                struct siginfo __user *infop,
1059                                struct rusage __user *rusagep)
1060 {
1061         int retval = rusagep ? getrusage(p, RUSAGE_BOTH, rusagep) : 0;
1062
1063         put_task_struct(p);
1064         if (!retval)
1065                 retval = put_user(SIGCHLD, &infop->si_signo);
1066         if (!retval)
1067                 retval = put_user(0, &infop->si_errno);
1068         if (!retval)
1069                 retval = put_user((short)why, &infop->si_code);
1070         if (!retval)
1071                 retval = put_user(pid, &infop->si_pid);
1072         if (!retval)
1073                 retval = put_user(uid, &infop->si_uid);
1074         if (!retval)
1075                 retval = put_user(status, &infop->si_status);
1076         if (!retval)
1077                 retval = pid;
1078         return retval;
1079 }
1080
1081 /*
1082  * Handle sys_wait4 work for one task in state EXIT_ZOMBIE.  We hold
1083  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1084  * the lock and this task is uninteresting.  If we return nonzero, we have
1085  * released the lock and the system call should return.
1086  */
1087 static int wait_task_zombie(struct task_struct *p, int noreap,
1088                             struct siginfo __user *infop,
1089                             int __user *stat_addr, struct rusage __user *ru)
1090 {
1091         unsigned long state;
1092         int retval;
1093         int status;
1094
1095         if (unlikely(noreap)) {
1096                 pid_t pid = p->pid;
1097                 uid_t uid = p->uid;
1098                 int exit_code = p->exit_code;
1099                 int why, status;
1100
1101                 if (unlikely(p->exit_state != EXIT_ZOMBIE))
1102                         return 0;
1103                 if (unlikely(p->exit_signal == -1 && p->ptrace == 0))
1104                         return 0;
1105                 get_task_struct(p);
1106                 read_unlock(&tasklist_lock);
1107                 if ((exit_code & 0x7f) == 0) {
1108                         why = CLD_EXITED;
1109                         status = exit_code >> 8;
1110                 } else {
1111                         why = (exit_code & 0x80) ? CLD_DUMPED : CLD_KILLED;
1112                         status = exit_code & 0x7f;
1113                 }
1114                 return wait_noreap_copyout(p, pid, uid, why,
1115                                            status, infop, ru);
1116         }
1117
1118         /*
1119          * Try to move the task's state to DEAD
1120          * only one thread is allowed to do this:
1121          */
1122         state = xchg(&p->exit_state, EXIT_DEAD);
1123         if (state != EXIT_ZOMBIE) {
1124                 BUG_ON(state != EXIT_DEAD);
1125                 return 0;
1126         }
1127         if (unlikely(p->exit_signal == -1 && p->ptrace == 0)) {
1128                 /*
1129                  * This can only happen in a race with a ptraced thread
1130                  * dying on another processor.
1131                  */
1132                 return 0;
1133         }
1134
1135         if (likely(p->real_parent == p->parent) && likely(p->signal)) {
1136                 struct signal_struct *psig;
1137                 struct signal_struct *sig;
1138
1139                 /*
1140                  * The resource counters for the group leader are in its
1141                  * own task_struct.  Those for dead threads in the group
1142                  * are in its signal_struct, as are those for the child
1143                  * processes it has previously reaped.  All these
1144                  * accumulate in the parent's signal_struct c* fields.
1145                  *
1146                  * We don't bother to take a lock here to protect these
1147                  * p->signal fields, because they are only touched by
1148                  * __exit_signal, which runs with tasklist_lock
1149                  * write-locked anyway, and so is excluded here.  We do
1150                  * need to protect the access to p->parent->signal fields,
1151                  * as other threads in the parent group can be right
1152                  * here reaping other children at the same time.
1153                  */
1154                 spin_lock_irq(&p->parent->sighand->siglock);
1155                 psig = p->parent->signal;
1156                 sig = p->signal;
1157                 psig->cutime =
1158                         cputime_add(psig->cutime,
1159                         cputime_add(p->utime,
1160                         cputime_add(sig->utime,
1161                                     sig->cutime)));
1162                 psig->cstime =
1163                         cputime_add(psig->cstime,
1164                         cputime_add(p->stime,
1165                         cputime_add(sig->stime,
1166                                     sig->cstime)));
1167                 psig->cmin_flt +=
1168                         p->min_flt + sig->min_flt + sig->cmin_flt;
1169                 psig->cmaj_flt +=
1170                         p->maj_flt + sig->maj_flt + sig->cmaj_flt;
1171                 psig->cnvcsw +=
1172                         p->nvcsw + sig->nvcsw + sig->cnvcsw;
1173                 psig->cnivcsw +=
1174                         p->nivcsw + sig->nivcsw + sig->cnivcsw;
1175                 spin_unlock_irq(&p->parent->sighand->siglock);
1176         }
1177
1178         /*
1179          * Now we are sure this task is interesting, and no other
1180          * thread can reap it because we set its state to EXIT_DEAD.
1181          */
1182         read_unlock(&tasklist_lock);
1183
1184         retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
1185         status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1186                 ? p->signal->group_exit_code : p->exit_code;
1187         if (!retval && stat_addr)
1188                 retval = put_user(status, stat_addr);
1189         if (!retval && infop)
1190                 retval = put_user(SIGCHLD, &infop->si_signo);
1191         if (!retval && infop)
1192                 retval = put_user(0, &infop->si_errno);
1193         if (!retval && infop) {
1194                 int why;
1195
1196                 if ((status & 0x7f) == 0) {
1197                         why = CLD_EXITED;
1198                         status >>= 8;
1199                 } else {
1200                         why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
1201                         status &= 0x7f;
1202                 }
1203                 retval = put_user((short)why, &infop->si_code);
1204                 if (!retval)
1205                         retval = put_user(status, &infop->si_status);
1206         }
1207         if (!retval && infop)
1208                 retval = put_user(p->pid, &infop->si_pid);
1209         if (!retval && infop)
1210                 retval = put_user(p->uid, &infop->si_uid);
1211         if (retval) {
1212                 // TODO: is this safe?
1213                 p->exit_state = EXIT_ZOMBIE;
1214                 return retval;
1215         }
1216         retval = p->pid;
1217         if (p->real_parent != p->parent) {
1218                 write_lock_irq(&tasklist_lock);
1219                 /* Double-check with lock held.  */
1220                 if (p->real_parent != p->parent) {
1221                         __ptrace_unlink(p);
1222                         // TODO: is this safe?
1223                         p->exit_state = EXIT_ZOMBIE;
1224                         /*
1225                          * If this is not a detached task, notify the parent.
1226                          * If it's still not detached after that, don't release
1227                          * it now.
1228                          */
1229                         if (p->exit_signal != -1) {
1230                                 do_notify_parent(p, p->exit_signal);
1231                                 if (p->exit_signal != -1)
1232                                         p = NULL;
1233                         }
1234                 }
1235                 write_unlock_irq(&tasklist_lock);
1236         }
1237         if (p != NULL)
1238                 release_task(p);
1239         BUG_ON(!retval);
1240         return retval;
1241 }
1242
1243 /*
1244  * Handle sys_wait4 work for one task in state TASK_STOPPED.  We hold
1245  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1246  * the lock and this task is uninteresting.  If we return nonzero, we have
1247  * released the lock and the system call should return.
1248  */
1249 static int wait_task_stopped(struct task_struct *p, int delayed_group_leader,
1250                              int noreap, struct siginfo __user *infop,
1251                              int __user *stat_addr, struct rusage __user *ru)
1252 {
1253         int retval, exit_code;
1254
1255         if (!p->exit_code)
1256                 return 0;
1257         if (delayed_group_leader && !(p->ptrace & PT_PTRACED) &&
1258             p->signal && p->signal->group_stop_count > 0)
1259                 /*
1260                  * A group stop is in progress and this is the group leader.
1261                  * We won't report until all threads have stopped.
1262                  */
1263                 return 0;
1264
1265         /*
1266          * Now we are pretty sure this task is interesting.
1267          * Make sure it doesn't get reaped out from under us while we
1268          * give up the lock and then examine it below.  We don't want to
1269          * keep holding onto the tasklist_lock while we call getrusage and
1270          * possibly take page faults for user memory.
1271          */
1272         get_task_struct(p);
1273         read_unlock(&tasklist_lock);
1274
1275         if (unlikely(noreap)) {
1276                 pid_t pid = p->pid;
1277                 uid_t uid = p->uid;
1278                 int why = (p->ptrace & PT_PTRACED) ? CLD_TRAPPED : CLD_STOPPED;
1279
1280                 exit_code = p->exit_code;
1281                 if (unlikely(!exit_code) ||
1282                     unlikely(p->state & TASK_TRACED))
1283                         goto bail_ref;
1284                 return wait_noreap_copyout(p, pid, uid,
1285                                            why, (exit_code << 8) | 0x7f,
1286                                            infop, ru);
1287         }
1288
1289         write_lock_irq(&tasklist_lock);
1290
1291         /*
1292          * This uses xchg to be atomic with the thread resuming and setting
1293          * it.  It must also be done with the write lock held to prevent a
1294          * race with the EXIT_ZOMBIE case.
1295          */
1296         exit_code = xchg(&p->exit_code, 0);
1297         if (unlikely(p->exit_state)) {
1298                 /*
1299                  * The task resumed and then died.  Let the next iteration
1300                  * catch it in EXIT_ZOMBIE.  Note that exit_code might
1301                  * already be zero here if it resumed and did _exit(0).
1302                  * The task itself is dead and won't touch exit_code again;
1303                  * other processors in this function are locked out.
1304                  */
1305                 p->exit_code = exit_code;
1306                 exit_code = 0;
1307         }
1308         if (unlikely(exit_code == 0)) {
1309                 /*
1310                  * Another thread in this function got to it first, or it
1311                  * resumed, or it resumed and then died.
1312                  */
1313                 write_unlock_irq(&tasklist_lock);
1314 bail_ref:
1315                 put_task_struct(p);
1316                 /*
1317                  * We are returning to the wait loop without having successfully
1318                  * removed the process and having released the lock. We cannot
1319                  * continue, since the "p" task pointer is potentially stale.
1320                  *
1321                  * Return -EAGAIN, and do_wait() will restart the loop from the
1322                  * beginning. Do _not_ re-acquire the lock.
1323                  */
1324                 return -EAGAIN;
1325         }
1326
1327         /* move to end of parent's list to avoid starvation */
1328         remove_parent(p);
1329         add_parent(p);
1330
1331         write_unlock_irq(&tasklist_lock);
1332
1333         retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
1334         if (!retval && stat_addr)
1335                 retval = put_user((exit_code << 8) | 0x7f, stat_addr);
1336         if (!retval && infop)
1337                 retval = put_user(SIGCHLD, &infop->si_signo);
1338         if (!retval && infop)
1339                 retval = put_user(0, &infop->si_errno);
1340         if (!retval && infop)
1341                 retval = put_user((short)((p->ptrace & PT_PTRACED)
1342                                           ? CLD_TRAPPED : CLD_STOPPED),
1343                                   &infop->si_code);
1344         if (!retval && infop)
1345                 retval = put_user(exit_code, &infop->si_status);
1346         if (!retval && infop)
1347                 retval = put_user(p->pid, &infop->si_pid);
1348         if (!retval && infop)
1349                 retval = put_user(p->uid, &infop->si_uid);
1350         if (!retval)
1351                 retval = p->pid;
1352         put_task_struct(p);
1353
1354         BUG_ON(!retval);
1355         return retval;
1356 }
1357
1358 /*
1359  * Handle do_wait work for one task in a live, non-stopped state.
1360  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1361  * the lock and this task is uninteresting.  If we return nonzero, we have
1362  * released the lock and the system call should return.
1363  */
1364 static int wait_task_continued(struct task_struct *p, int noreap,
1365                                struct siginfo __user *infop,
1366                                int __user *stat_addr, struct rusage __user *ru)
1367 {
1368         int retval;
1369         pid_t pid;
1370         uid_t uid;
1371
1372         if (unlikely(!p->signal))
1373                 return 0;
1374
1375         if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
1376                 return 0;
1377
1378         spin_lock_irq(&p->sighand->siglock);
1379         /* Re-check with the lock held.  */
1380         if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
1381                 spin_unlock_irq(&p->sighand->siglock);
1382                 return 0;
1383         }
1384         if (!noreap)
1385                 p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1386         spin_unlock_irq(&p->sighand->siglock);
1387
1388         pid = p->pid;
1389         uid = p->uid;
1390         get_task_struct(p);
1391         read_unlock(&tasklist_lock);
1392
1393         if (!infop) {
1394                 retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
1395                 put_task_struct(p);
1396                 if (!retval && stat_addr)
1397                         retval = put_user(0xffff, stat_addr);
1398                 if (!retval)
1399                         retval = p->pid;
1400         } else {
1401                 retval = wait_noreap_copyout(p, pid, uid,
1402                                              CLD_CONTINUED, SIGCONT,
1403                                              infop, ru);
1404                 BUG_ON(retval == 0);
1405         }
1406
1407         return retval;
1408 }
1409
1410
1411 static inline int my_ptrace_child(struct task_struct *p)
1412 {
1413         if (!(p->ptrace & PT_PTRACED))
1414                 return 0;
1415         if (!(p->ptrace & PT_ATTACHED))
1416                 return 1;
1417         /*
1418          * This child was PTRACE_ATTACH'd.  We should be seeing it only if
1419          * we are the attacher.  If we are the real parent, this is a race
1420          * inside ptrace_attach.  It is waiting for the tasklist_lock,
1421          * which we have to switch the parent links, but has already set
1422          * the flags in p->ptrace.
1423          */
1424         return (p->parent != p->real_parent);
1425 }
1426
1427 static long do_wait(pid_t pid, int options, struct siginfo __user *infop,
1428                     int __user *stat_addr, struct rusage __user *ru)
1429 {
1430         DECLARE_WAITQUEUE(wait, current);
1431         struct task_struct *tsk;
1432         int flag, retval;
1433
1434         add_wait_queue(&current->signal->wait_chldexit,&wait);
1435 repeat:
1436         /*
1437          * We will set this flag if we see any child that might later
1438          * match our criteria, even if we are not able to reap it yet.
1439          */
1440         flag = 0;
1441         current->state = TASK_INTERRUPTIBLE;
1442         read_lock(&tasklist_lock);
1443         tsk = current;
1444         do {
1445                 struct task_struct *p;
1446                 struct list_head *_p;
1447                 int ret;
1448
1449                 list_for_each(_p,&tsk->children) {
1450                         p = list_entry(_p, struct task_struct, sibling);
1451
1452                         ret = eligible_child(pid, options, p);
1453                         if (!ret)
1454                                 continue;
1455
1456                         switch (p->state) {
1457                         case TASK_TRACED:
1458                                 /*
1459                                  * When we hit the race with PTRACE_ATTACH,
1460                                  * we will not report this child.  But the
1461                                  * race means it has not yet been moved to
1462                                  * our ptrace_children list, so we need to
1463                                  * set the flag here to avoid a spurious ECHILD
1464                                  * when the race happens with the only child.
1465                                  */
1466                                 flag = 1;
1467                                 if (!my_ptrace_child(p))
1468                                         continue;
1469                                 /*FALLTHROUGH*/
1470                         case TASK_STOPPED:
1471                                 /*
1472                                  * It's stopped now, so it might later
1473                                  * continue, exit, or stop again.
1474                                  */
1475                                 flag = 1;
1476                                 if (!(options & WUNTRACED) &&
1477                                     !my_ptrace_child(p))
1478                                         continue;
1479                                 retval = wait_task_stopped(p, ret == 2,
1480                                                            (options & WNOWAIT),
1481                                                            infop,
1482                                                            stat_addr, ru);
1483                                 if (retval == -EAGAIN)
1484                                         goto repeat;
1485                                 if (retval != 0) /* He released the lock.  */
1486                                         goto end;
1487                                 break;
1488                         default:
1489                         // case EXIT_DEAD:
1490                                 if (p->exit_state == EXIT_DEAD)
1491                                         continue;
1492                         // case EXIT_ZOMBIE:
1493                                 if (p->exit_state == EXIT_ZOMBIE) {
1494                                         /*
1495                                          * Eligible but we cannot release
1496                                          * it yet:
1497                                          */
1498                                         if (ret == 2)
1499                                                 goto check_continued;
1500                                         if (!likely(options & WEXITED))
1501                                                 continue;
1502                                         retval = wait_task_zombie(
1503                                                 p, (options & WNOWAIT),
1504                                                 infop, stat_addr, ru);
1505                                         /* He released the lock.  */
1506                                         if (retval != 0)
1507                                                 goto end;
1508                                         break;
1509                                 }
1510 check_continued:
1511                                 /*
1512                                  * It's running now, so it might later
1513                                  * exit, stop, or stop and then continue.
1514                                  */
1515                                 flag = 1;
1516                                 if (!unlikely(options & WCONTINUED))
1517                                         continue;
1518                                 retval = wait_task_continued(
1519                                         p, (options & WNOWAIT),
1520                                         infop, stat_addr, ru);
1521                                 if (retval != 0) /* He released the lock.  */
1522                                         goto end;
1523                                 break;
1524                         }
1525                 }
1526                 if (!flag) {
1527                         list_for_each(_p, &tsk->ptrace_children) {
1528                                 p = list_entry(_p, struct task_struct,
1529                                                 ptrace_list);
1530                                 if (!eligible_child(pid, options, p))
1531                                         continue;
1532                                 flag = 1;
1533                                 break;
1534                         }
1535                 }
1536                 if (options & __WNOTHREAD)
1537                         break;
1538                 tsk = next_thread(tsk);
1539                 BUG_ON(tsk->signal != current->signal);
1540         } while (tsk != current);
1541
1542         read_unlock(&tasklist_lock);
1543         if (flag) {
1544                 retval = 0;
1545                 if (options & WNOHANG)
1546                         goto end;
1547                 retval = -ERESTARTSYS;
1548                 if (signal_pending(current))
1549                         goto end;
1550                 schedule();
1551                 goto repeat;
1552         }
1553         retval = -ECHILD;
1554 end:
1555         current->state = TASK_RUNNING;
1556         remove_wait_queue(&current->signal->wait_chldexit,&wait);
1557         if (infop) {
1558                 if (retval > 0)
1559                 retval = 0;
1560                 else {
1561                         /*
1562                          * For a WNOHANG return, clear out all the fields
1563                          * we would set so the user can easily tell the
1564                          * difference.
1565                          */
1566                         if (!retval)
1567                                 retval = put_user(0, &infop->si_signo);
1568                         if (!retval)
1569                                 retval = put_user(0, &infop->si_errno);
1570                         if (!retval)
1571                                 retval = put_user(0, &infop->si_code);
1572                         if (!retval)
1573                                 retval = put_user(0, &infop->si_pid);
1574                         if (!retval)
1575                                 retval = put_user(0, &infop->si_uid);
1576                         if (!retval)
1577                                 retval = put_user(0, &infop->si_status);
1578                 }
1579         }
1580         return retval;
1581 }
1582
1583 asmlinkage long sys_waitid(int which, pid_t pid,
1584                            struct siginfo __user *infop, int options,
1585                            struct rusage __user *ru)
1586 {
1587         long ret;
1588
1589         if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED))
1590                 return -EINVAL;
1591         if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
1592                 return -EINVAL;
1593
1594         switch (which) {
1595         case P_ALL:
1596                 pid = -1;
1597                 break;
1598         case P_PID:
1599                 if (pid <= 0)
1600                         return -EINVAL;
1601                 break;
1602         case P_PGID:
1603                 if (pid <= 0)
1604                         return -EINVAL;
1605                 pid = -pid;
1606                 break;
1607         default:
1608                 return -EINVAL;
1609         }
1610
1611         ret = do_wait(pid, options, infop, NULL, ru);
1612
1613         /* avoid REGPARM breakage on x86: */
1614         prevent_tail_call(ret);
1615         return ret;
1616 }
1617
1618 asmlinkage long sys_wait4(pid_t pid, int __user *stat_addr,
1619                           int options, struct rusage __user *ru)
1620 {
1621         long ret;
1622
1623         if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
1624                         __WNOTHREAD|__WCLONE|__WALL))
1625                 return -EINVAL;
1626         ret = do_wait(pid, options | WEXITED, NULL, stat_addr, ru);
1627
1628         /* avoid REGPARM breakage on x86: */
1629         prevent_tail_call(ret);
1630         return ret;
1631 }
1632
1633 #ifdef __ARCH_WANT_SYS_WAITPID
1634
1635 /*
1636  * sys_waitpid() remains for compatibility. waitpid() should be
1637  * implemented by calling sys_wait4() from libc.a.
1638  */
1639 asmlinkage long sys_waitpid(pid_t pid, int __user *stat_addr, int options)
1640 {
1641         return sys_wait4(pid, stat_addr, options, NULL);
1642 }
1643
1644 #endif