kernel/exit.c

   1 /*
   2  *  linux/kernel/exit.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 #include <linux/config.h>
   8 #include <linux/mm.h>
   9 #include <linux/slab.h>
  10 #include <linux/interrupt.h>
  11 #include <linux/smp_lock.h>
  12 #include <linux/module.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
  32 #include <asm/uaccess.h>
  33 #include <asm/unistd.h>
  34 #include <asm/pgtable.h>
  35 #include <asm/mmu_context.h>
  36
  37 extern void sem_exit (void);
  38 extern struct task_struct *child_reaper;
  39
  40 int getrusage(struct task_struct *, int, struct rusage __user *);
  41
  42 static void exit_mm(struct task_struct * tsk);
  43
  44 static void __unhash_process(struct task_struct *p)
  45 {
  46         nr_threads--;
  47         detach_pid(p, PIDTYPE_PID);
  48         detach_pid(p, PIDTYPE_TGID);
  49         if (thread_group_leader(p)) {
  50                 detach_pid(p, PIDTYPE_PGID);
  51                 detach_pid(p, PIDTYPE_SID);
  52                 if (p->pid)
  53                         __get_cpu_var(process_counts)--;
  54         }
  55
  56         REMOVE_LINKS(p);
  57 }
  58
  59 void release_task(struct task_struct * p)
  60 {
  61         int zap_leader;
  62         task_t *leader;
  63         struct dentry *proc_dentry;
  64
  65 repeat:
  66         atomic_dec(&p->user->processes);
  67         spin_lock(&p->proc_lock);
  68         proc_dentry = proc_pid_unhash(p);
  69         write_lock_irq(&tasklist_lock);
  70         if (unlikely(p->ptrace))
  71                 __ptrace_unlink(p);
  72         BUG_ON(!list_empty(&p->ptrace_list) || !list_empty(&p->ptrace_children));
  73         __exit_signal(p);
  74         __exit_sighand(p);
  75         /*
  76          * Note that the fastpath in sys_times depends on __exit_signal having
  77          * updated the counters before a task is removed from the tasklist of
  78          * the process by __unhash_process.
  79          */
  80         __unhash_process(p);
  81
  82         /*
  83          * If we are the last non-leader member of the thread
  84          * group, and the leader is zombie, then notify the
  85          * group leader's parent process. (if it wants notification.)
  86          */
  87         zap_leader = 0;
  88         leader = p->group_leader;
  89         if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
  90                 BUG_ON(leader->exit_signal == -1);
  91                 do_notify_parent(leader, leader->exit_signal);
  92                 /*
  93                  * If we were the last child thread and the leader has
  94                  * exited already, and the leader's parent ignores SIGCHLD,
  95                  * then we are the one who should release the leader.
  96                  *
  97                  * do_notify_parent() will have marked it self-reaping in
  98                  * that case.
  99                  */
 100                 zap_leader = (leader->exit_signal == -1);
 101         }
 102
 103         sched_exit(p);
 104         write_unlock_irq(&tasklist_lock);
 105         spin_unlock(&p->proc_lock);
 106         proc_pid_flush(proc_dentry);
 107         release_thread(p);
 108         put_task_struct(p);
 109
 110         p = leader;
 111         if (unlikely(zap_leader))
 112                 goto repeat;
 113 }
 114
 115 /* we are using it only for SMP init */
 116
 117 void unhash_process(struct task_struct *p)
 118 {
 119         struct dentry *proc_dentry;
 120
 121         spin_lock(&p->proc_lock);
 122         proc_dentry = proc_pid_unhash(p);
 123         write_lock_irq(&tasklist_lock);
 124         __unhash_process(p);
 125         write_unlock_irq(&tasklist_lock);
 126         spin_unlock(&p->proc_lock);
 127         proc_pid_flush(proc_dentry);
 128 }
 129
 130 /*
 131  * This checks not only the pgrp, but falls back on the pid if no
 132  * satisfactory pgrp is found. I dunno - gdb doesn't work correctly
 133  * without this...
 134  */
 135 int session_of_pgrp(int pgrp)
 136 {
 137         struct task_struct *p;
 138         int sid = -1;
 139
 140         read_lock(&tasklist_lock);
 141         do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
 142                 if (p->signal->session > 0) {
 143                         sid = p->signal->session;
 144                         goto out;
 145                 }
 146         } while_each_task_pid(pgrp, PIDTYPE_PGID, p);
 147         p = find_task_by_pid(pgrp);
 148         if (p)
 149                 sid = p->signal->session;
 150 out:
 151         read_unlock(&tasklist_lock);
 152
 153         return sid;
 154 }
 155
 156 /*
 157  * Determine if a process group is "orphaned", according to the POSIX
 158  * definition in 2.2.2.52.  Orphaned process groups are not to be affected
 159  * by terminal-generated stop signals.  Newly orphaned process groups are
 160  * to receive a SIGHUP and a SIGCONT.
 161  *
 162  * "I ask you, have you ever known what it is to be an orphan?"
 163  */
 164 static int will_become_orphaned_pgrp(int pgrp, task_t *ignored_task)
 165 {
 166         struct task_struct *p;
 167         int ret = 1;
 168
 169         do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
 170                 if (p == ignored_task
 171                                 || p->exit_state
 172                                 || p->real_parent->pid == 1)
 173                         continue;
 174                 if (process_group(p->real_parent) != pgrp
 175                             && p->real_parent->signal->session == p->signal->session) {
 176                         ret = 0;
 177                         break;
 178                 }
 179         } while_each_task_pid(pgrp, PIDTYPE_PGID, p);
 180         return ret;     /* (sighing) "Often!" */
 181 }
 182
 183 int is_orphaned_pgrp(int pgrp)
 184 {
 185         int retval;
 186
 187         read_lock(&tasklist_lock);
 188         retval = will_become_orphaned_pgrp(pgrp, NULL);
 189         read_unlock(&tasklist_lock);
 190
 191         return retval;
 192 }
 193
 194 static inline int has_stopped_jobs(int pgrp)
 195 {
 196         int retval = 0;
 197         struct task_struct *p;
 198
 199         do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
 200                 if (p->state != TASK_STOPPED)
 201                         continue;
 202
 203                 /* If p is stopped by a debugger on a signal that won't
 204                    stop it, then don't count p as stopped.  This isn't
 205                    perfect but it's a good approximation.  */
 206                 if (unlikely (p->ptrace)
 207                     && p->exit_code != SIGSTOP
 208                     && p->exit_code != SIGTSTP
 209                     && p->exit_code != SIGTTOU
 210                     && p->exit_code != SIGTTIN)
 211                         continue;
 212
 213                 retval = 1;
 214                 break;
 215         } while_each_task_pid(pgrp, PIDTYPE_PGID, p);
 216         return retval;
 217 }
 218
 219 /**
 220  * reparent_to_init - Reparent the calling kernel thread to the init task.
 221  *
 222  * If a kernel thread is launched as a result of a system call, or if
 223  * it ever exits, it should generally reparent itself to init so that
 224  * it is correctly cleaned up on exit.
 225  *
 226  * The various task state such as scheduling policy and priority may have
 227  * been inherited from a user process, so we reset them to sane values here.
 228  *
 229  * NOTE that reparent_to_init() gives the caller full capabilities.
 230  */
 231 static inline void reparent_to_init(void)
 232 {
 233         write_lock_irq(&tasklist_lock);
 234
 235         ptrace_unlink(current);
 236         /* Reparent to init */
 237         REMOVE_LINKS(current);
 238         current->parent = child_reaper;
 239         current->real_parent = child_reaper;
 240         SET_LINKS(current);
 241
 242         /* Set the exit signal to SIGCHLD so we signal init on exit */
 243         current->exit_signal = SIGCHLD;
 244
 245         if ((current->policy == SCHED_NORMAL) && (task_nice(current) < 0))
 246                 set_user_nice(current, 0);
 247         /* cpus_allowed? */
 248         /* rt_priority? */
 249         /* signals? */
 250         security_task_reparent_to_init(current);
 251         memcpy(current->signal->rlim, init_task.signal->rlim,
 252                sizeof(current->signal->rlim));
 253         atomic_inc(&(INIT_USER->__count));
 254         write_unlock_irq(&tasklist_lock);
 255         switch_uid(INIT_USER);
 256 }
 257
 258 void __set_special_pids(pid_t session, pid_t pgrp)
 259 {
 260         struct task_struct *curr = current;
 261
 262         if (curr->signal->session != session) {
 263                 detach_pid(curr, PIDTYPE_SID);
 264                 curr->signal->session = session;
 265                 attach_pid(curr, PIDTYPE_SID, session);
 266         }
 267         if (process_group(curr) != pgrp) {
 268                 detach_pid(curr, PIDTYPE_PGID);
 269                 curr->signal->pgrp = pgrp;
 270                 attach_pid(curr, PIDTYPE_PGID, pgrp);
 271         }
 272 }
 273
 274 void set_special_pids(pid_t session, pid_t pgrp)
 275 {
 276         write_lock_irq(&tasklist_lock);
 277         __set_special_pids(session, pgrp);
 278         write_unlock_irq(&tasklist_lock);
 279 }
 280
 281 /*
 282  * Let kernel threads use this to say that they
 283  * allow a certain signal (since daemonize() will
 284  * have disabled all of them by default).
 285  */
 286 int allow_signal(int sig)
 287 {
 288         if (!valid_signal(sig) || sig < 1)
 289                 return -EINVAL;
 290
 291         spin_lock_irq(&current->sighand->siglock);
 292         sigdelset(&current->blocked, sig);
 293         if (!current->mm) {
 294                 /* Kernel threads handle their own signals.
 295                    Let the signal code know it'll be handled, so
 296                    that they don't get converted to SIGKILL or
 297                    just silently dropped */
 298                 current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2;
 299         }
 300         recalc_sigpending();
 301         spin_unlock_irq(&current->sighand->siglock);
 302         return 0;
 303 }
 304
 305 EXPORT_SYMBOL(allow_signal);
 306
 307 int disallow_signal(int sig)
 308 {
 309         if (!valid_signal(sig) || sig < 1)
 310                 return -EINVAL;
 311
 312         spin_lock_irq(&current->sighand->siglock);
 313         sigaddset(&current->blocked, sig);
 314         recalc_sigpending();
 315         spin_unlock_irq(&current->sighand->siglock);
 316         return 0;
 317 }
 318
 319 EXPORT_SYMBOL(disallow_signal);
 320
 321 /*
 322  *      Put all the gunge required to become a kernel thread without
 323  *      attached user resources in one place where it belongs.
 324  */
 325
 326 void daemonize(const char *name, ...)
 327 {
 328         va_list args;
 329         struct fs_struct *fs;
 330         sigset_t blocked;
 331
 332         va_start(args, name);
 333         vsnprintf(current->comm, sizeof(current->comm), name, args);
 334         va_end(args);
 335
 336         /*
 337          * If we were started as result of loading a module, close all of the
 338          * user space pages.  We don't need them, and if we didn't close them
 339          * they would be locked into memory.
 340          */
 341         exit_mm(current);
 342
 343         set_special_pids(1, 1);
 344         down(&tty_sem);
 345         current->signal->tty = NULL;
 346         up(&tty_sem);
 347
 348         /* Block and flush all signals */
 349         sigfillset(&blocked);
 350         sigprocmask(SIG_BLOCK, &blocked, NULL);
 351         flush_signals(current);
 352
 353         /* Become as one with the init task */
 354
 355         exit_fs(current);       /* current->fs->count--; */
 356         fs = init_task.fs;
 357         current->fs = fs;
 358         atomic_inc(&fs->count);
 359         exit_files(current);
 360         current->files = init_task.files;
 361         atomic_inc(&current->files->count);
 362
 363         reparent_to_init();
 364 }
 365
 366 EXPORT_SYMBOL(daemonize);
 367
 368 static inline void close_files(struct files_struct * files)
 369 {
 370         int i, j;
 371
 372         j = 0;
 373         for (;;) {
 374                 unsigned long set;
 375                 i = j * __NFDBITS;
 376                 if (i >= files->max_fdset || i >= files->max_fds)
 377                         break;
 378                 set = files->open_fds->fds_bits[j++];
 379                 while (set) {
 380                         if (set & 1) {
 381                                 struct file * file = xchg(&files->fd[i], NULL);
 382                                 if (file)
 383                                         filp_close(file, files);
 384                         }
 385                         i++;
 386                         set >>= 1;
 387                 }
 388         }
 389 }
 390
 391 struct files_struct *get_files_struct(struct task_struct *task)
 392 {
 393         struct files_struct *files;
 394
 395         task_lock(task);
 396         files = task->files;
 397         if (files)
 398                 atomic_inc(&files->count);
 399         task_unlock(task);
 400
 401         return files;
 402 }
 403
 404 void fastcall put_files_struct(struct files_struct *files)
 405 {
 406         if (atomic_dec_and_test(&files->count)) {
 407                 close_files(files);
 408                 /*
 409                  * Free the fd and fdset arrays if we expanded them.
 410                  */
 411                 if (files->fd != &files->fd_array[0])
 412                         free_fd_array(files->fd, files->max_fds);
 413                 if (files->max_fdset > __FD_SETSIZE) {
 414                         free_fdset(files->open_fds, files->max_fdset);
 415                         free_fdset(files->close_on_exec, files->max_fdset);
 416                 }
 417                 kmem_cache_free(files_cachep, files);
 418         }
 419 }
 420
 421 EXPORT_SYMBOL(put_files_struct);
 422
 423 static inline void __exit_files(struct task_struct *tsk)
 424 {
 425         struct files_struct * files = tsk->files;
 426
 427         if (files) {
 428                 task_lock(tsk);
 429                 tsk->files = NULL;
 430                 task_unlock(tsk);
 431                 put_files_struct(files);
 432         }
 433 }
 434
 435 void exit_files(struct task_struct *tsk)
 436 {
 437         __exit_files(tsk);
 438 }
 439
 440 static inline void __put_fs_struct(struct fs_struct *fs)
 441 {
 442         /* No need to hold fs->lock if we are killing it */
 443         if (atomic_dec_and_test(&fs->count)) {
 444                 dput(fs->root);
 445                 mntput(fs->rootmnt);
 446                 dput(fs->pwd);
 447                 mntput(fs->pwdmnt);
 448                 if (fs->altroot) {
 449                         dput(fs->altroot);
 450                         mntput(fs->altrootmnt);
 451                 }
 452                 kmem_cache_free(fs_cachep, fs);
 453         }
 454 }
 455
 456 void put_fs_struct(struct fs_struct *fs)
 457 {
 458         __put_fs_struct(fs);
 459 }
 460
 461 static inline void __exit_fs(struct task_struct *tsk)
 462 {
 463         struct fs_struct * fs = tsk->fs;
 464
 465         if (fs) {
 466                 task_lock(tsk);
 467                 tsk->fs = NULL;
 468                 task_unlock(tsk);
 469                 __put_fs_struct(fs);
 470         }
 471 }
 472
 473 void exit_fs(struct task_struct *tsk)
 474 {
 475         __exit_fs(tsk);
 476 }
 477
 478 EXPORT_SYMBOL_GPL(exit_fs);
 479
 480 /*
 481  * Turn us into a lazy TLB process if we
 482  * aren't already..
 483  */
 484 static void exit_mm(struct task_struct * tsk)
 485 {
 486         struct mm_struct *mm = tsk->mm;
 487
 488         mm_release(tsk, mm);
 489         if (!mm)
 490                 return;
 491         /*
 492          * Serialize with any possible pending coredump.
 493          * We must hold mmap_sem around checking core_waiters
 494          * and clearing tsk->mm.  The core-inducing thread
 495          * will increment core_waiters for each thread in the
 496          * group with ->mm != NULL.
 497          */
 498         down_read(&mm->mmap_sem);
 499         if (mm->core_waiters) {
 500                 up_read(&mm->mmap_sem);
 501                 down_write(&mm->mmap_sem);
 502                 if (!--mm->core_waiters)
 503                         complete(mm->core_startup_done);
 504                 up_write(&mm->mmap_sem);
 505
 506                 wait_for_completion(&mm->core_done);
 507                 down_read(&mm->mmap_sem);
 508         }
 509         atomic_inc(&mm->mm_count);
 510         if (mm != tsk->active_mm) BUG();
 511         /* more a memory barrier than a real lock */
 512         task_lock(tsk);
 513         tsk->mm = NULL;
 514         up_read(&mm->mmap_sem);
 515         enter_lazy_tlb(mm, current);
 516         task_unlock(tsk);
 517         mmput(mm);
 518 }
 519
 520 static inline void choose_new_parent(task_t *p, task_t *reaper, task_t *child_reaper)
 521 {
 522         /*
 523          * Make sure we're not reparenting to ourselves and that
 524          * the parent is not a zombie.
 525          */
 526         BUG_ON(p == reaper || reaper->exit_state >= EXIT_ZOMBIE);
 527         p->real_parent = reaper;
 528 }
 529
 530 static inline void reparent_thread(task_t *p, task_t *father, int traced)
 531 {
 532         /* We don't want people slaying init.  */
 533         if (p->exit_signal != -1)
 534                 p->exit_signal = SIGCHLD;
 535
 536         if (p->pdeath_signal)
 537                 /* We already hold the tasklist_lock here.  */
 538                 group_send_sig_info(p->pdeath_signal, (void *) 0, p);
 539
 540         /* Move the child from its dying parent to the new one.  */
 541         if (unlikely(traced)) {
 542                 /* Preserve ptrace links if someone else is tracing this child.  */
 543                 list_del_init(&p->ptrace_list);
 544                 if (p->parent != p->real_parent)
 545                         list_add(&p->ptrace_list, &p->real_parent->ptrace_children);
 546         } else {
 547                 /* If this child is being traced, then we're the one tracing it
 548                  * anyway, so let go of it.
 549                  */
 550                 p->ptrace = 0;
 551                 list_del_init(&p->sibling);
 552                 p->parent = p->real_parent;
 553                 list_add_tail(&p->sibling, &p->parent->children);
 554
 555                 /* If we'd notified the old parent about this child's death,
 556                  * also notify the new parent.
 557                  */
 558                 if (p->exit_state == EXIT_ZOMBIE && p->exit_signal != -1 &&
 559                     thread_group_empty(p))
 560                         do_notify_parent(p, p->exit_signal);
 561                 else if (p->state == TASK_TRACED) {
 562                         /*
 563                          * If it was at a trace stop, turn it into
 564                          * a normal stop since it's no longer being
 565                          * traced.
 566                          */
 567                         ptrace_untrace(p);
 568                 }
 569         }
 570
 571         /*
 572          * process group orphan check
 573          * Case ii: Our child is in a different pgrp
 574          * than we are, and it was the only connection
 575          * outside, so the child pgrp is now orphaned.
 576          */
 577         if ((process_group(p) != process_group(father)) &&
 578             (p->signal->session == father->signal->session)) {
 579                 int pgrp = process_group(p);
 580
 581                 if (will_become_orphaned_pgrp(pgrp, NULL) && has_stopped_jobs(pgrp)) {
 582                         __kill_pg_info(SIGHUP, (void *)1, pgrp);
 583                         __kill_pg_info(SIGCONT, (void *)1, pgrp);
 584                 }
 585         }
 586 }
 587
 588 /*
 589  * When we die, we re-parent all our children.
 590  * Try to give them to another thread in our thread
 591  * group, and if no such member exists, give it to
 592  * the global child reaper process (ie "init")
 593  */
 594 static inline void forget_original_parent(struct task_struct * father,
 595                                           struct list_head *to_release)
 596 {
 597         struct task_struct *p, *reaper = father;
 598         struct list_head *_p, *_n;
 599
 600         do {
 601                 reaper = next_thread(reaper);
 602                 if (reaper == father) {
 603                         reaper = child_reaper;
 604                         break;
 605                 }
 606         } while (reaper->exit_state);
 607
 608         /*
 609          * There are only two places where our children can be:
 610          *
 611          * - in our child list
 612          * - in our ptraced child list
 613          *
 614          * Search them and reparent children.
 615          */
 616         list_for_each_safe(_p, _n, &father->children) {
 617                 int ptrace;
 618                 p = list_entry(_p,struct task_struct,sibling);
 619
 620                 ptrace = p->ptrace;
 621
 622                 /* if father isn't the real parent, then ptrace must be enabled */
 623                 BUG_ON(father != p->real_parent && !ptrace);
 624
 625                 if (father == p->real_parent) {
 626                         /* reparent with a reaper, real father it's us */
 627                         choose_new_parent(p, reaper, child_reaper);
 628                         reparent_thread(p, father, 0);
 629                 } else {
 630                         /* reparent ptraced task to its real parent */
 631                         __ptrace_unlink (p);
 632                         if (p->exit_state == EXIT_ZOMBIE && p->exit_signal != -1 &&
 633                             thread_group_empty(p))
 634                                 do_notify_parent(p, p->exit_signal);
 635                 }
 636
 637                 /*
 638                  * if the ptraced child is a zombie with exit_signal == -1
 639                  * we must collect it before we exit, or it will remain
 640                  * zombie forever since we prevented it from self-reap itself
 641                  * while it was being traced by us, to be able to see it in wait4.
 642                  */
 643                 if (unlikely(ptrace && p->exit_state == EXIT_ZOMBIE && p->exit_signal == -1))
 644                         list_add(&p->ptrace_list, to_release);
 645         }
 646         list_for_each_safe(_p, _n, &father->ptrace_children) {
 647                 p = list_entry(_p,struct task_struct,ptrace_list);
 648                 choose_new_parent(p, reaper, child_reaper);
 649                 reparent_thread(p, father, 1);
 650         }
 651 }
 652
 653 /*
 654  * Send signals to all our closest relatives so that they know
 655  * to properly mourn us..
 656  */
 657 static void exit_notify(struct task_struct *tsk)
 658 {
 659         int state;
 660         struct task_struct *t;
 661         struct list_head ptrace_dead, *_p, *_n;
 662
 663         if (signal_pending(tsk) && !(tsk->signal->flags & SIGNAL_GROUP_EXIT)
 664             && !thread_group_empty(tsk)) {
 665                 /*
 666                  * This occurs when there was a race between our exit
 667                  * syscall and a group signal choosing us as the one to
 668                  * wake up.  It could be that we are the only thread
 669                  * alerted to check for pending signals, but another thread
 670                  * should be woken now to take the signal since we will not.
 671                  * Now we'll wake all the threads in the group just to make
 672                  * sure someone gets all the pending signals.
 673                  */
 674                 read_lock(&tasklist_lock);
 675                 spin_lock_irq(&tsk->sighand->siglock);
 676                 for (t = next_thread(tsk); t != tsk; t = next_thread(t))
 677                         if (!signal_pending(t) && !(t->flags & PF_EXITING)) {
 678                                 recalc_sigpending_tsk(t);
 679                                 if (signal_pending(t))
 680                                         signal_wake_up(t, 0);
 681                         }
 682                 spin_unlock_irq(&tsk->sighand->siglock);
 683                 read_unlock(&tasklist_lock);
 684         }
 685
 686         write_lock_irq(&tasklist_lock);
 687
 688         /*
 689          * This does two things:
 690          *
 691          * A.  Make init inherit all the child processes
 692          * B.  Check to see if any process groups have become orphaned
 693          *      as a result of our exiting, and if they have any stopped
 694          *      jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
 695          */
 696
 697         INIT_LIST_HEAD(&ptrace_dead);
 698         forget_original_parent(tsk, &ptrace_dead);
 699         BUG_ON(!list_empty(&tsk->children));
 700         BUG_ON(!list_empty(&tsk->ptrace_children));
 701
 702         /*
 703          * Check to see if any process groups have become orphaned
 704          * as a result of our exiting, and if they have any stopped
 705          * jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
 706          *
 707          * Case i: Our father is in a different pgrp than we are
 708          * and we were the only connection outside, so our pgrp
 709          * is about to become orphaned.
 710          */
 711
 712         t = tsk->real_parent;
 713
 714         if ((process_group(t) != process_group(tsk)) &&
 715             (t->signal->session == tsk->signal->session) &&
 716             will_become_orphaned_pgrp(process_group(tsk), tsk) &&
 717             has_stopped_jobs(process_group(tsk))) {
 718                 __kill_pg_info(SIGHUP, (void *)1, process_group(tsk));
 719                 __kill_pg_info(SIGCONT, (void *)1, process_group(tsk));
 720         }
 721
 722         /* Let father know we died
 723          *
 724          * Thread signals are configurable, but you aren't going to use
 725          * that to send signals to arbitary processes.
 726          * That stops right now.
 727          *
 728          * If the parent exec id doesn't match the exec id we saved
 729          * when we started then we know the parent has changed security
 730          * domain.
 731          *
 732          * If our self_exec id doesn't match our parent_exec_id then
 733          * we have changed execution domain as these two values started
 734          * the same after a fork.
 735          *
 736          */
 737
 738         if (tsk->exit_signal != SIGCHLD && tsk->exit_signal != -1 &&
 739             ( tsk->parent_exec_id != t->self_exec_id  ||
 740               tsk->self_exec_id != tsk->parent_exec_id)
 741             && !capable(CAP_KILL))
 742                 tsk->exit_signal = SIGCHLD;
 743
 744
 745         /* If something other than our normal parent is ptracing us, then
 746          * send it a SIGCHLD instead of honoring exit_signal.  exit_signal
 747          * only has special meaning to our real parent.
 748          */
 749         if (tsk->exit_signal != -1 && thread_group_empty(tsk)) {
 750                 int signal = tsk->parent == tsk->real_parent ? tsk->exit_signal : SIGCHLD;
 751                 do_notify_parent(tsk, signal);
 752         } else if (tsk->ptrace) {
 753                 do_notify_parent(tsk, SIGCHLD);
 754         }
 755
 756         state = EXIT_ZOMBIE;
 757         if (tsk->exit_signal == -1 &&
 758             (likely(tsk->ptrace == 0) ||
 759              unlikely(tsk->parent->signal->flags & SIGNAL_GROUP_EXIT)))
 760                 state = EXIT_DEAD;
 761         tsk->exit_state = state;
 762
 763         write_unlock_irq(&tasklist_lock);
 764
 765         list_for_each_safe(_p, _n, &ptrace_dead) {
 766                 list_del_init(_p);
 767                 t = list_entry(_p,struct task_struct,ptrace_list);
 768                 release_task(t);
 769         }
 770
 771         /* If the process is dead, release it - nobody will wait for it */
 772         if (state == EXIT_DEAD)
 773                 release_task(tsk);
 774
 775         /* PF_DEAD causes final put_task_struct after we schedule. */
 776         preempt_disable();
 777         tsk->flags |= PF_DEAD;
 778 }
 779
 780 fastcall NORET_TYPE void do_exit(long code)
 781 {
 782         struct task_struct *tsk = current;
 783         int group_dead;
 784
 785         profile_task_exit(tsk);
 786
 787         if (unlikely(in_interrupt()))
 788                 panic("Aiee, killing interrupt handler!");
 789         if (unlikely(!tsk->pid))
 790                 panic("Attempted to kill the idle task!");
 791         if (unlikely(tsk->pid == 1))
 792                 panic("Attempted to kill init!");
 793         if (tsk->io_context)
 794                 exit_io_context();
 795
 796         if (unlikely(current->ptrace & PT_TRACE_EXIT)) {
 797                 current->ptrace_message = code;
 798                 ptrace_notify((PTRACE_EVENT_EXIT << 8) | SIGTRAP);
 799         }
 800
 801         /*
 802          * We're taking recursive faults here in do_exit. Safest is to just
 803          * leave this task alone and wait for reboot.
 804          */
 805         if (unlikely(tsk->flags & PF_EXITING)) {
 806                 printk(KERN_ALERT
 807                         "Fixing recursive fault but reboot is needed!\n");
 808                 set_current_state(TASK_UNINTERRUPTIBLE);
 809                 schedule();
 810         }
 811
 812         tsk->flags |= PF_EXITING;
 813
 814         /*
 815          * Make sure we don't try to process any timer firings
 816          * while we are already exiting.
 817          */
 818         tsk->it_virt_expires = cputime_zero;
 819         tsk->it_prof_expires = cputime_zero;
 820         tsk->it_sched_expires = 0;
 821
 822         if (unlikely(in_atomic()))
 823                 printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
 824                                 current->comm, current->pid,
 825                                 preempt_count());
 826
 827         acct_update_integrals(tsk);
 828         update_mem_hiwater(tsk);
 829         group_dead = atomic_dec_and_test(&tsk->signal->live);
 830         if (group_dead)
 831                 acct_process(code);
 832         exit_mm(tsk);
 833
 834         exit_sem(tsk);
 835         __exit_files(tsk);
 836         __exit_fs(tsk);
 837         exit_namespace(tsk);
 838         exit_thread();
 839         cpuset_exit(tsk);
 840         exit_keys(tsk);
 841
 842         if (group_dead && tsk->signal->leader)
 843                 disassociate_ctty(1);
 844
 845         module_put(tsk->thread_info->exec_domain->module);
 846         if (tsk->binfmt)
 847                 module_put(tsk->binfmt->module);
 848
 849         tsk->exit_code = code;
 850         exit_notify(tsk);
 851 #ifdef CONFIG_NUMA
 852         mpol_free(tsk->mempolicy);
 853         tsk->mempolicy = NULL;
 854 #endif
 855
 856         BUG_ON(!(current->flags & PF_DEAD));
 857         schedule();
 858         BUG();
 859         /* Avoid "noreturn function does return".  */
 860         for (;;) ;
 861 }
 862
 863 EXPORT_SYMBOL_GPL(do_exit);
 864
 865 NORET_TYPE void complete_and_exit(struct completion *comp, long code)
 866 {
 867         if (comp)
 868                 complete(comp);
 869
 870         do_exit(code);
 871 }
 872
 873 EXPORT_SYMBOL(complete_and_exit);
 874
 875 asmlinkage long sys_exit(int error_code)
 876 {
 877         do_exit((error_code&0xff)<<8);
 878 }
 879
 880 task_t fastcall *next_thread(const task_t *p)
 881 {
 882         return pid_task(p->pids[PIDTYPE_TGID].pid_list.next, PIDTYPE_TGID);
 883 }
 884
 885 EXPORT_SYMBOL(next_thread);
 886
 887 /*
 888  * Take down every thread in the group.  This is called by fatal signals
 889  * as well as by sys_exit_group (below).
 890  */
 891 NORET_TYPE void
 892 do_group_exit(int exit_code)
 893 {
 894         BUG_ON(exit_code & 0x80); /* core dumps don't get here */
 895
 896         if (current->signal->flags & SIGNAL_GROUP_EXIT)
 897                 exit_code = current->signal->group_exit_code;
 898         else if (!thread_group_empty(current)) {
 899                 struct signal_struct *const sig = current->signal;
 900                 struct sighand_struct *const sighand = current->sighand;
 901                 read_lock(&tasklist_lock);
 902                 spin_lock_irq(&sighand->siglock);
 903                 if (sig->flags & SIGNAL_GROUP_EXIT)
 904                         /* Another thread got here before we took the lock.  */
 905                         exit_code = sig->group_exit_code;
 906                 else {
 907                         sig->flags = SIGNAL_GROUP_EXIT;
 908                         sig->group_exit_code = exit_code;
 909                         zap_other_threads(current);
 910                 }
 911                 spin_unlock_irq(&sighand->siglock);
 912                 read_unlock(&tasklist_lock);
 913         }
 914
 915         do_exit(exit_code);
 916         /* NOTREACHED */
 917 }
 918
 919 /*
 920  * this kills every thread in the thread group. Note that any externally
 921  * wait4()-ing process will get the correct exit code - even if this
 922  * thread is not the thread group leader.
 923  */
 924 asmlinkage void sys_exit_group(int error_code)
 925 {
 926         do_group_exit((error_code & 0xff) << 8);
 927 }
 928
 929 static int eligible_child(pid_t pid, int options, task_t *p)
 930 {
 931         if (pid > 0) {
 932                 if (p->pid != pid)
 933                         return 0;
 934         } else if (!pid) {
 935                 if (process_group(p) != process_group(current))
 936                         return 0;
 937         } else if (pid != -1) {
 938                 if (process_group(p) != -pid)
 939                         return 0;
 940         }
 941
 942         /*
 943          * Do not consider detached threads that are
 944          * not ptraced:
 945          */
 946         if (p->exit_signal == -1 && !p->ptrace)
 947                 return 0;
 948
 949         /* Wait for all children (clone and not) if __WALL is set;
 950          * otherwise, wait for clone children *only* if __WCLONE is
 951          * set; otherwise, wait for non-clone children *only*.  (Note:
 952          * A "clone" child here is one that reports to its parent
 953          * using a signal other than SIGCHLD.) */
 954         if (((p->exit_signal != SIGCHLD) ^ ((options & __WCLONE) != 0))
 955             && !(options & __WALL))
 956                 return 0;
 957         /*
 958          * Do not consider thread group leaders that are
 959          * in a non-empty thread group:
 960          */
 961         if (current->tgid != p->tgid && delay_group_leader(p))
 962                 return 2;
 963
 964         if (security_task_wait(p))
 965                 return 0;
 966
 967         return 1;
 968 }
 969
 970 static int wait_noreap_copyout(task_t *p, pid_t pid, uid_t uid,
 971                                int why, int status,
 972                                struct siginfo __user *infop,
 973                                struct rusage __user *rusagep)
 974 {
 975         int retval = rusagep ? getrusage(p, RUSAGE_BOTH, rusagep) : 0;
 976         put_task_struct(p);
 977         if (!retval)
 978                 retval = put_user(SIGCHLD, &infop->si_signo);
 979         if (!retval)
 980                 retval = put_user(0, &infop->si_errno);
 981         if (!retval)
 982                 retval = put_user((short)why, &infop->si_code);
 983         if (!retval)
 984                 retval = put_user(pid, &infop->si_pid);
 985         if (!retval)
 986                 retval = put_user(uid, &infop->si_uid);
 987         if (!retval)
 988                 retval = put_user(status, &infop->si_status);
 989         if (!retval)
 990                 retval = pid;
 991         return retval;
 992 }
 993
 994 /*
 995  * Handle sys_wait4 work for one task in state EXIT_ZOMBIE.  We hold
 996  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
 997  * the lock and this task is uninteresting.  If we return nonzero, we have
 998  * released the lock and the system call should return.
 999  */
1000 static int wait_task_zombie(task_t *p, int noreap,
1001                             struct siginfo __user *infop,
1002                             int __user *stat_addr, struct rusage __user *ru)
1003 {
1004         unsigned long state;
1005         int retval;
1006         int status;
1007
1008         if (unlikely(noreap)) {
1009                 pid_t pid = p->pid;
1010                 uid_t uid = p->uid;
1011                 int exit_code = p->exit_code;
1012                 int why, status;
1013
1014                 if (unlikely(p->exit_state != EXIT_ZOMBIE))
1015                         return 0;
1016                 if (unlikely(p->exit_signal == -1 && p->ptrace == 0))
1017                         return 0;
1018                 get_task_struct(p);
1019                 read_unlock(&tasklist_lock);
1020                 if ((exit_code & 0x7f) == 0) {
1021                         why = CLD_EXITED;
1022                         status = exit_code >> 8;
1023                 } else {
1024                         why = (exit_code & 0x80) ? CLD_DUMPED : CLD_KILLED;
1025                         status = exit_code & 0x7f;
1026                 }
1027                 return wait_noreap_copyout(p, pid, uid, why,
1028                                            status, infop, ru);
1029         }
1030
1031         /*
1032          * Try to move the task's state to DEAD
1033          * only one thread is allowed to do this:
1034          */
1035         state = xchg(&p->exit_state, EXIT_DEAD);
1036         if (state != EXIT_ZOMBIE) {
1037                 BUG_ON(state != EXIT_DEAD);
1038                 return 0;
1039         }
1040         if (unlikely(p->exit_signal == -1 && p->ptrace == 0)) {
1041                 /*
1042                  * This can only happen in a race with a ptraced thread
1043                  * dying on another processor.
1044                  */
1045                 return 0;
1046         }
1047
1048         if (likely(p->real_parent == p->parent) && likely(p->signal)) {
1049                 /*
1050                  * The resource counters for the group leader are in its
1051                  * own task_struct.  Those for dead threads in the group
1052                  * are in its signal_struct, as are those for the child
1053                  * processes it has previously reaped.  All these
1054                  * accumulate in the parent's signal_struct c* fields.
1055                  *
1056                  * We don't bother to take a lock here to protect these
1057                  * p->signal fields, because they are only touched by
1058                  * __exit_signal, which runs with tasklist_lock
1059                  * write-locked anyway, and so is excluded here.  We do
1060                  * need to protect the access to p->parent->signal fields,
1061                  * as other threads in the parent group can be right
1062                  * here reaping other children at the same time.
1063                  */
1064                 spin_lock_irq(&p->parent->sighand->siglock);
1065                 p->parent->signal->cutime =
1066                         cputime_add(p->parent->signal->cutime,
1067                         cputime_add(p->utime,
1068                         cputime_add(p->signal->utime,
1069                                     p->signal->cutime)));
1070                 p->parent->signal->cstime =
1071                         cputime_add(p->parent->signal->cstime,
1072                         cputime_add(p->stime,
1073                         cputime_add(p->signal->stime,
1074                                     p->signal->cstime)));
1075                 p->parent->signal->cmin_flt +=
1076                         p->min_flt + p->signal->min_flt + p->signal->cmin_flt;
1077                 p->parent->signal->cmaj_flt +=
1078                         p->maj_flt + p->signal->maj_flt + p->signal->cmaj_flt;
1079                 p->parent->signal->cnvcsw +=
1080                         p->nvcsw + p->signal->nvcsw + p->signal->cnvcsw;
1081                 p->parent->signal->cnivcsw +=
1082                         p->nivcsw + p->signal->nivcsw + p->signal->cnivcsw;
1083                 spin_unlock_irq(&p->parent->sighand->siglock);
1084         }
1085
1086         /*
1087          * Now we are sure this task is interesting, and no other
1088          * thread can reap it because we set its state to EXIT_DEAD.
1089          */
1090         read_unlock(&tasklist_lock);
1091
1092         retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
1093         status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1094                 ? p->signal->group_exit_code : p->exit_code;
1095         if (!retval && stat_addr)
1096                 retval = put_user(status, stat_addr);
1097         if (!retval && infop)
1098                 retval = put_user(SIGCHLD, &infop->si_signo);
1099         if (!retval && infop)
1100                 retval = put_user(0, &infop->si_errno);
1101         if (!retval && infop) {
1102                 int why;
1103
1104                 if ((status & 0x7f) == 0) {
1105                         why = CLD_EXITED;
1106                         status >>= 8;
1107                 } else {
1108                         why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
1109                         status &= 0x7f;
1110                 }
1111                 retval = put_user((short)why, &infop->si_code);
1112                 if (!retval)
1113                         retval = put_user(status, &infop->si_status);
1114         }
1115         if (!retval && infop)
1116                 retval = put_user(p->pid, &infop->si_pid);
1117         if (!retval && infop)
1118                 retval = put_user(p->uid, &infop->si_uid);
1119         if (retval) {
1120                 // TODO: is this safe?
1121                 p->exit_state = EXIT_ZOMBIE;
1122                 return retval;
1123         }
1124         retval = p->pid;
1125         if (p->real_parent != p->parent) {
1126                 write_lock_irq(&tasklist_lock);
1127                 /* Double-check with lock held.  */
1128                 if (p->real_parent != p->parent) {
1129                         __ptrace_unlink(p);
1130                         // TODO: is this safe?
1131                         p->exit_state = EXIT_ZOMBIE;
1132                         /*
1133                          * If this is not a detached task, notify the parent.
1134                          * If it's still not detached after that, don't release
1135                          * it now.
1136                          */
1137                         if (p->exit_signal != -1) {
1138                                 do_notify_parent(p, p->exit_signal);
1139                                 if (p->exit_signal != -1)
1140                                         p = NULL;
1141                         }
1142                 }
1143                 write_unlock_irq(&tasklist_lock);
1144         }
1145         if (p != NULL)
1146                 release_task(p);
1147         BUG_ON(!retval);
1148         return retval;
1149 }
1150
1151 /*
1152  * Handle sys_wait4 work for one task in state TASK_STOPPED.  We hold
1153  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1154  * the lock and this task is uninteresting.  If we return nonzero, we have
1155  * released the lock and the system call should return.
1156  */
1157 static int wait_task_stopped(task_t *p, int delayed_group_leader, int noreap,
1158                              struct siginfo __user *infop,
1159                              int __user *stat_addr, struct rusage __user *ru)
1160 {
1161         int retval, exit_code;
1162
1163         if (!p->exit_code)
1164                 return 0;
1165         if (delayed_group_leader && !(p->ptrace & PT_PTRACED) &&
1166             p->signal && p->signal->group_stop_count > 0)
1167                 /*
1168                  * A group stop is in progress and this is the group leader.
1169                  * We won't report until all threads have stopped.
1170                  */
1171                 return 0;
1172
1173         /*
1174          * Now we are pretty sure this task is interesting.
1175          * Make sure it doesn't get reaped out from under us while we
1176          * give up the lock and then examine it below.  We don't want to
1177          * keep holding onto the tasklist_lock while we call getrusage and
1178          * possibly take page faults for user memory.
1179          */
1180         get_task_struct(p);
1181         read_unlock(&tasklist_lock);
1182
1183         if (unlikely(noreap)) {
1184                 pid_t pid = p->pid;
1185                 uid_t uid = p->uid;
1186                 int why = (p->ptrace & PT_PTRACED) ? CLD_TRAPPED : CLD_STOPPED;
1187
1188                 exit_code = p->exit_code;
1189                 if (unlikely(!exit_code) ||
1190                     unlikely(p->state > TASK_STOPPED))
1191                         goto bail_ref;
1192                 return wait_noreap_copyout(p, pid, uid,
1193                                            why, (exit_code << 8) | 0x7f,
1194                                            infop, ru);
1195         }
1196
1197         write_lock_irq(&tasklist_lock);
1198
1199         /*
1200          * This uses xchg to be atomic with the thread resuming and setting
1201          * it.  It must also be done with the write lock held to prevent a
1202          * race with the EXIT_ZOMBIE case.
1203          */
1204         exit_code = xchg(&p->exit_code, 0);
1205         if (unlikely(p->exit_state)) {
1206                 /*
1207                  * The task resumed and then died.  Let the next iteration
1208                  * catch it in EXIT_ZOMBIE.  Note that exit_code might
1209                  * already be zero here if it resumed and did _exit(0).
1210                  * The task itself is dead and won't touch exit_code again;
1211                  * other processors in this function are locked out.
1212                  */
1213                 p->exit_code = exit_code;
1214                 exit_code = 0;
1215         }
1216         if (unlikely(exit_code == 0)) {
1217                 /*
1218                  * Another thread in this function got to it first, or it
1219                  * resumed, or it resumed and then died.
1220                  */
1221                 write_unlock_irq(&tasklist_lock);
1222 bail_ref:
1223                 put_task_struct(p);
1224                 /*
1225                  * We are returning to the wait loop without having successfully
1226                  * removed the process and having released the lock. We cannot
1227                  * continue, since the "p" task pointer is potentially stale.
1228                  *
1229                  * Return -EAGAIN, and do_wait() will restart the loop from the
1230                  * beginning. Do _not_ re-acquire the lock.
1231                  */
1232                 return -EAGAIN;
1233         }
1234
1235         /* move to end of parent's list to avoid starvation */
1236         remove_parent(p);
1237         add_parent(p, p->parent);
1238
1239         write_unlock_irq(&tasklist_lock);
1240
1241         retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
1242         if (!retval && stat_addr)
1243                 retval = put_user((exit_code << 8) | 0x7f, stat_addr);
1244         if (!retval && infop)
1245                 retval = put_user(SIGCHLD, &infop->si_signo);
1246         if (!retval && infop)
1247                 retval = put_user(0, &infop->si_errno);
1248         if (!retval && infop)
1249                 retval = put_user((short)((p->ptrace & PT_PTRACED)
1250                                           ? CLD_TRAPPED : CLD_STOPPED),
1251                                   &infop->si_code);
1252         if (!retval && infop)
1253                 retval = put_user(exit_code, &infop->si_status);
1254         if (!retval && infop)
1255                 retval = put_user(p->pid, &infop->si_pid);
1256         if (!retval && infop)
1257                 retval = put_user(p->uid, &infop->si_uid);
1258         if (!retval)
1259                 retval = p->pid;
1260         put_task_struct(p);
1261
1262         BUG_ON(!retval);
1263         return retval;
1264 }
1265
1266 /*
1267  * Handle do_wait work for one task in a live, non-stopped state.
1268  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1269  * the lock and this task is uninteresting.  If we return nonzero, we have
1270  * released the lock and the system call should return.
1271  */
1272 static int wait_task_continued(task_t *p, int noreap,
1273                                struct siginfo __user *infop,
1274                                int __user *stat_addr, struct rusage __user *ru)
1275 {
1276         int retval;
1277         pid_t pid;
1278         uid_t uid;
1279
1280         if (unlikely(!p->signal))
1281                 return 0;
1282
1283         if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
1284                 return 0;
1285
1286         spin_lock_irq(&p->sighand->siglock);
1287         /* Re-check with the lock held.  */
1288         if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
1289                 spin_unlock_irq(&p->sighand->siglock);
1290                 return 0;
1291         }
1292         if (!noreap)
1293                 p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1294         spin_unlock_irq(&p->sighand->siglock);
1295
1296         pid = p->pid;
1297         uid = p->uid;
1298         get_task_struct(p);
1299         read_unlock(&tasklist_lock);
1300
1301         if (!infop) {
1302                 retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
1303                 put_task_struct(p);
1304                 if (!retval && stat_addr)
1305                         retval = put_user(0xffff, stat_addr);
1306                 if (!retval)
1307                         retval = p->pid;
1308         } else {
1309                 retval = wait_noreap_copyout(p, pid, uid,
1310                                              CLD_CONTINUED, SIGCONT,
1311                                              infop, ru);
1312                 BUG_ON(retval == 0);
1313         }
1314
1315         return retval;
1316 }
1317
1318
1319 static inline int my_ptrace_child(struct task_struct *p)
1320 {
1321         if (!(p->ptrace & PT_PTRACED))
1322                 return 0;
1323         if (!(p->ptrace & PT_ATTACHED))
1324                 return 1;
1325         /*
1326          * This child was PTRACE_ATTACH'd.  We should be seeing it only if
1327          * we are the attacher.  If we are the real parent, this is a race
1328          * inside ptrace_attach.  It is waiting for the tasklist_lock,
1329          * which we have to switch the parent links, but has already set
1330          * the flags in p->ptrace.
1331          */
1332         return (p->parent != p->real_parent);
1333 }
1334
1335 static long do_wait(pid_t pid, int options, struct siginfo __user *infop,
1336                     int __user *stat_addr, struct rusage __user *ru)
1337 {
1338         DECLARE_WAITQUEUE(wait, current);
1339         struct task_struct *tsk;
1340         int flag, retval;
1341
1342         add_wait_queue(&current->signal->wait_chldexit,&wait);
1343 repeat:
1344         /*
1345          * We will set this flag if we see any child that might later
1346          * match our criteria, even if we are not able to reap it yet.
1347          */
1348         flag = 0;
1349         current->state = TASK_INTERRUPTIBLE;
1350         read_lock(&tasklist_lock);
1351         tsk = current;
1352         do {
1353                 struct task_struct *p;
1354                 struct list_head *_p;
1355                 int ret;
1356
1357                 list_for_each(_p,&tsk->children) {
1358                         p = list_entry(_p,struct task_struct,sibling);
1359
1360                         ret = eligible_child(pid, options, p);
1361                         if (!ret)
1362                                 continue;
1363
1364                         switch (p->state) {
1365                         case TASK_TRACED:
1366                                 if (!my_ptrace_child(p))
1367                                         continue;
1368                                 /*FALLTHROUGH*/
1369                         case TASK_STOPPED:
1370                                 /*
1371                                  * It's stopped now, so it might later
1372                                  * continue, exit, or stop again.
1373                                  */
1374                                 flag = 1;
1375                                 if (!(options & WUNTRACED) &&
1376                                     !my_ptrace_child(p))
1377                                         continue;
1378                                 retval = wait_task_stopped(p, ret == 2,
1379                                                            (options & WNOWAIT),
1380                                                            infop,
1381                                                            stat_addr, ru);
1382                                 if (retval == -EAGAIN)
1383                                         goto repeat;
1384                                 if (retval != 0) /* He released the lock.  */
1385                                         goto end;
1386                                 break;
1387                         default:
1388                         // case EXIT_DEAD:
1389                                 if (p->exit_state == EXIT_DEAD)
1390                                         continue;
1391                         // case EXIT_ZOMBIE:
1392                                 if (p->exit_state == EXIT_ZOMBIE) {
1393                                         /*
1394                                          * Eligible but we cannot release
1395                                          * it yet:
1396                                          */
1397                                         if (ret == 2)
1398                                                 goto check_continued;
1399                                         if (!likely(options & WEXITED))
1400                                                 continue;
1401                                         retval = wait_task_zombie(
1402                                                 p, (options & WNOWAIT),
1403                                                 infop, stat_addr, ru);
1404                                         /* He released the lock.  */
1405                                         if (retval != 0)
1406                                                 goto end;
1407                                         break;
1408                                 }
1409 check_continued:
1410                                 /*
1411                                  * It's running now, so it might later
1412                                  * exit, stop, or stop and then continue.
1413                                  */
1414                                 flag = 1;
1415                                 if (!unlikely(options & WCONTINUED))
1416                                         continue;
1417                                 retval = wait_task_continued(
1418                                         p, (options & WNOWAIT),
1419                                         infop, stat_addr, ru);
1420                                 if (retval != 0) /* He released the lock.  */
1421                                         goto end;
1422                                 break;
1423                         }
1424                 }
1425                 if (!flag) {
1426                         list_for_each(_p, &tsk->ptrace_children) {
1427                                 p = list_entry(_p, struct task_struct,
1428                                                 ptrace_list);
1429                                 if (!eligible_child(pid, options, p))
1430                                         continue;
1431                                 flag = 1;
1432                                 break;
1433                         }
1434                 }
1435                 if (options & __WNOTHREAD)
1436                         break;
1437                 tsk = next_thread(tsk);
1438                 if (tsk->signal != current->signal)
1439                         BUG();
1440         } while (tsk != current);
1441
1442         read_unlock(&tasklist_lock);
1443         if (flag) {
1444                 retval = 0;
1445                 if (options & WNOHANG)
1446                         goto end;
1447                 retval = -ERESTARTSYS;
1448                 if (signal_pending(current))
1449                         goto end;
1450                 schedule();
1451                 goto repeat;
1452         }
1453         retval = -ECHILD;
1454 end:
1455         current->state = TASK_RUNNING;
1456         remove_wait_queue(&current->signal->wait_chldexit,&wait);
1457         if (infop) {
1458                 if (retval > 0)
1459                 retval = 0;
1460                 else {
1461                         /*
1462                          * For a WNOHANG return, clear out all the fields
1463                          * we would set so the user can easily tell the
1464                          * difference.
1465                          */
1466                         if (!retval)
1467                                 retval = put_user(0, &infop->si_signo);
1468                         if (!retval)
1469                                 retval = put_user(0, &infop->si_errno);
1470                         if (!retval)
1471                                 retval = put_user(0, &infop->si_code);
1472                         if (!retval)
1473                                 retval = put_user(0, &infop->si_pid);
1474                         if (!retval)
1475                                 retval = put_user(0, &infop->si_uid);
1476                         if (!retval)
1477                                 retval = put_user(0, &infop->si_status);
1478                 }
1479         }
1480         return retval;
1481 }
1482
1483 asmlinkage long sys_waitid(int which, pid_t pid,
1484                            struct siginfo __user *infop, int options,
1485                            struct rusage __user *ru)
1486 {
1487         long ret;
1488
1489         if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED))
1490                 return -EINVAL;
1491         if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
1492                 return -EINVAL;
1493
1494         switch (which) {
1495         case P_ALL:
1496                 pid = -1;
1497                 break;
1498         case P_PID:
1499                 if (pid <= 0)
1500                         return -EINVAL;
1501                 break;
1502         case P_PGID:
1503                 if (pid <= 0)
1504                         return -EINVAL;
1505                 pid = -pid;
1506                 break;
1507         default:
1508                 return -EINVAL;
1509         }
1510
1511         ret = do_wait(pid, options, infop, NULL, ru);
1512
1513         /* avoid REGPARM breakage on x86: */
1514         prevent_tail_call(ret);
1515         return ret;
1516 }
1517
1518 asmlinkage long sys_wait4(pid_t pid, int __user *stat_addr,
1519                           int options, struct rusage __user *ru)
1520 {
1521         long ret;
1522
1523         if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
1524                         __WNOTHREAD|__WCLONE|__WALL))
1525                 return -EINVAL;
1526         ret = do_wait(pid, options | WEXITED, NULL, stat_addr, ru);
1527
1528         /* avoid REGPARM breakage on x86: */
1529         prevent_tail_call(ret);
1530         return ret;
1531 }
1532
1533 #ifdef __ARCH_WANT_SYS_WAITPID
1534
1535 /*
1536  * sys_waitpid() remains for compatibility. waitpid() should be
1537  * implemented by calling sys_wait4() from libc.a.
1538  */
1539 asmlinkage long sys_waitpid(pid_t pid, int __user *stat_addr, int options)
1540 {
1541         return sys_wait4(pid, stat_addr, options, NULL);
1542 }
1543
1544 #endif