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