kernel/exit.c

   1 /*
   2  *  linux/kernel/exit.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 #include <linux/mm.h>
   8 #include <linux/slab.h>
   9 #include <linux/interrupt.h>
  10 #include <linux/module.h>
  11 #include <linux/capability.h>
  12 #include <linux/completion.h>
  13 #include <linux/personality.h>
  14 #include <linux/tty.h>
  15 #include <linux/mnt_namespace.h>
  16 #include <linux/iocontext.h>
  17 #include <linux/key.h>
  18 #include <linux/security.h>
  19 #include <linux/cpu.h>
  20 #include <linux/acct.h>
  21 #include <linux/tsacct_kern.h>
  22 #include <linux/file.h>
  23 #include <linux/fdtable.h>
  24 #include <linux/binfmts.h>
  25 #include <linux/nsproxy.h>
  26 #include <linux/pid_namespace.h>
  27 #include <linux/ptrace.h>
  28 #include <linux/profile.h>
  29 #include <linux/mount.h>
  30 #include <linux/proc_fs.h>
  31 #include <linux/kthread.h>
  32 #include <linux/mempolicy.h>
  33 #include <linux/taskstats_kern.h>
  34 #include <linux/delayacct.h>
  35 #include <linux/freezer.h>
  36 #include <linux/cgroup.h>
  37 #include <linux/syscalls.h>
  38 #include <linux/signal.h>
  39 #include <linux/posix-timers.h>
  40 #include <linux/cn_proc.h>
  41 #include <linux/mutex.h>
  42 #include <linux/futex.h>
  43 #include <linux/pipe_fs_i.h>
  44 #include <linux/audit.h> /* for audit_free() */
  45 #include <linux/resource.h>
  46 #include <linux/blkdev.h>
  47 #include <linux/task_io_accounting_ops.h>
  48 #include <linux/tracehook.h>
  49 #include <linux/init_task.h>
  50 #include <trace/sched.h>
  51
  52 #include <asm/uaccess.h>
  53 #include <asm/unistd.h>
  54 #include <asm/pgtable.h>
  55 #include <asm/mmu_context.h>
  56 #include "cred-internals.h"
  57
  58 DEFINE_TRACE(sched_process_free);
  59 DEFINE_TRACE(sched_process_exit);
  60 DEFINE_TRACE(sched_process_wait);
  61
  62 static void exit_mm(struct task_struct * tsk);
  63
  64 static inline int task_detached(struct task_struct *p)
  65 {
  66         return p->exit_signal == -1;
  67 }
  68
  69 static void __unhash_process(struct task_struct *p)
  70 {
  71         nr_threads--;
  72         detach_pid(p, PIDTYPE_PID);
  73         if (thread_group_leader(p)) {
  74                 detach_pid(p, PIDTYPE_PGID);
  75                 detach_pid(p, PIDTYPE_SID);
  76
  77                 list_del_rcu(&p->tasks);
  78                 __get_cpu_var(process_counts)--;
  79         }
  80         list_del_rcu(&p->thread_group);
  81         list_del_init(&p->sibling);
  82 }
  83
  84 /*
  85  * This function expects the tasklist_lock write-locked.
  86  */
  87 static void __exit_signal(struct task_struct *tsk)
  88 {
  89         struct signal_struct *sig = tsk->signal;
  90         struct sighand_struct *sighand;
  91
  92         BUG_ON(!sig);
  93         BUG_ON(!atomic_read(&sig->count));
  94
  95         sighand = rcu_dereference(tsk->sighand);
  96         spin_lock(&sighand->siglock);
  97
  98         posix_cpu_timers_exit(tsk);
  99         if (atomic_dec_and_test(&sig->count))
 100                 posix_cpu_timers_exit_group(tsk);
 101         else {
 102                 /*
 103                  * If there is any task waiting for the group exit
 104                  * then notify it:
 105                  */
 106                 if (sig->group_exit_task && atomic_read(&sig->count) == sig->notify_count)
 107                         wake_up_process(sig->group_exit_task);
 108
 109                 if (tsk == sig->curr_target)
 110                         sig->curr_target = next_thread(tsk);
 111                 /*
 112                  * Accumulate here the counters for all threads but the
 113                  * group leader as they die, so they can be added into
 114                  * the process-wide totals when those are taken.
 115                  * The group leader stays around as a zombie as long
 116                  * as there are other threads.  When it gets reaped,
 117                  * the exit.c code will add its counts into these totals.
 118                  * We won't ever get here for the group leader, since it
 119                  * will have been the last reference on the signal_struct.
 120                  */
 121                 sig->utime = cputime_add(sig->utime, task_utime(tsk));
 122                 sig->stime = cputime_add(sig->stime, task_stime(tsk));
 123                 sig->gtime = cputime_add(sig->gtime, task_gtime(tsk));
 124                 sig->min_flt += tsk->min_flt;
 125                 sig->maj_flt += tsk->maj_flt;
 126                 sig->nvcsw += tsk->nvcsw;
 127                 sig->nivcsw += tsk->nivcsw;
 128                 sig->inblock += task_io_get_inblock(tsk);
 129                 sig->oublock += task_io_get_oublock(tsk);
 130                 task_io_accounting_add(&sig->ioac, &tsk->ioac);
 131                 sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
 132                 sig = NULL; /* Marker for below. */
 133         }
 134
 135         __unhash_process(tsk);
 136
 137         /*
 138          * Do this under ->siglock, we can race with another thread
 139          * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals.
 140          */
 141         flush_sigqueue(&tsk->pending);
 142
 143         tsk->signal = NULL;
 144         tsk->sighand = NULL;
 145         spin_unlock(&sighand->siglock);
 146
 147         __cleanup_sighand(sighand);
 148         clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
 149         if (sig) {
 150                 flush_sigqueue(&sig->shared_pending);
 151                 taskstats_tgid_free(sig);
 152                 /*
 153                  * Make sure ->signal can't go away under rq->lock,
 154                  * see account_group_exec_runtime().
 155                  */
 156                 task_rq_unlock_wait(tsk);
 157                 __cleanup_signal(sig);
 158         }
 159 }
 160
 161 static void delayed_put_task_struct(struct rcu_head *rhp)
 162 {
 163         struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
 164
 165         trace_sched_process_free(tsk);
 166         put_task_struct(tsk);
 167 }
 168
 169
 170 void release_task(struct task_struct * p)
 171 {
 172         struct task_struct *leader;
 173         int zap_leader;
 174 repeat:
 175         tracehook_prepare_release_task(p);
 176         /* don't need to get the RCU readlock here - the process is dead and
 177          * can't be modifying its own credentials */
 178         atomic_dec(&__task_cred(p)->user->processes);
 179
 180         proc_flush_task(p);
 181         write_lock_irq(&tasklist_lock);
 182         tracehook_finish_release_task(p);
 183         __exit_signal(p);
 184
 185         /*
 186          * If we are the last non-leader member of the thread
 187          * group, and the leader is zombie, then notify the
 188          * group leader's parent process. (if it wants notification.)
 189          */
 190         zap_leader = 0;
 191         leader = p->group_leader;
 192         if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
 193                 BUG_ON(task_detached(leader));
 194                 do_notify_parent(leader, leader->exit_signal);
 195                 /*
 196                  * If we were the last child thread and the leader has
 197                  * exited already, and the leader's parent ignores SIGCHLD,
 198                  * then we are the one who should release the leader.
 199                  *
 200                  * do_notify_parent() will have marked it self-reaping in
 201                  * that case.
 202                  */
 203                 zap_leader = task_detached(leader);
 204
 205                 /*
 206                  * This maintains the invariant that release_task()
 207                  * only runs on a task in EXIT_DEAD, just for sanity.
 208                  */
 209                 if (zap_leader)
 210                         leader->exit_state = EXIT_DEAD;
 211         }
 212
 213         write_unlock_irq(&tasklist_lock);
 214         release_thread(p);
 215         call_rcu(&p->rcu, delayed_put_task_struct);
 216
 217         p = leader;
 218         if (unlikely(zap_leader))
 219                 goto repeat;
 220 }
 221
 222 /*
 223  * This checks not only the pgrp, but falls back on the pid if no
 224  * satisfactory pgrp is found. I dunno - gdb doesn't work correctly
 225  * without this...
 226  *
 227  * The caller must hold rcu lock or the tasklist lock.
 228  */
 229 struct pid *session_of_pgrp(struct pid *pgrp)
 230 {
 231         struct task_struct *p;
 232         struct pid *sid = NULL;
 233
 234         p = pid_task(pgrp, PIDTYPE_PGID);
 235         if (p == NULL)
 236                 p = pid_task(pgrp, PIDTYPE_PID);
 237         if (p != NULL)
 238                 sid = task_session(p);
 239
 240         return sid;
 241 }
 242
 243 /*
 244  * Determine if a process group is "orphaned", according to the POSIX
 245  * definition in 2.2.2.52.  Orphaned process groups are not to be affected
 246  * by terminal-generated stop signals.  Newly orphaned process groups are
 247  * to receive a SIGHUP and a SIGCONT.
 248  *
 249  * "I ask you, have you ever known what it is to be an orphan?"
 250  */
 251 static int will_become_orphaned_pgrp(struct pid *pgrp, struct task_struct *ignored_task)
 252 {
 253         struct task_struct *p;
 254
 255         do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
 256                 if ((p == ignored_task) ||
 257                     (p->exit_state && thread_group_empty(p)) ||
 258                     is_global_init(p->real_parent))
 259                         continue;
 260
 261                 if (task_pgrp(p->real_parent) != pgrp &&
 262                     task_session(p->real_parent) == task_session(p))
 263                         return 0;
 264         } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
 265
 266         return 1;
 267 }
 268
 269 int is_current_pgrp_orphaned(void)
 270 {
 271         int retval;
 272
 273         read_lock(&tasklist_lock);
 274         retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
 275         read_unlock(&tasklist_lock);
 276
 277         return retval;
 278 }
 279
 280 static int has_stopped_jobs(struct pid *pgrp)
 281 {
 282         int retval = 0;
 283         struct task_struct *p;
 284
 285         do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
 286                 if (!task_is_stopped(p))
 287                         continue;
 288                 retval = 1;
 289                 break;
 290         } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
 291         return retval;
 292 }
 293
 294 /*
 295  * Check to see if any process groups have become orphaned as
 296  * a result of our exiting, and if they have any stopped jobs,
 297  * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
 298  */
 299 static void
 300 kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent)
 301 {
 302         struct pid *pgrp = task_pgrp(tsk);
 303         struct task_struct *ignored_task = tsk;
 304
 305         if (!parent)
 306                  /* exit: our father is in a different pgrp than
 307                   * we are and we were the only connection outside.
 308                   */
 309                 parent = tsk->real_parent;
 310         else
 311                 /* reparent: our child is in a different pgrp than
 312                  * we are, and it was the only connection outside.
 313                  */
 314                 ignored_task = NULL;
 315
 316         if (task_pgrp(parent) != pgrp &&
 317             task_session(parent) == task_session(tsk) &&
 318             will_become_orphaned_pgrp(pgrp, ignored_task) &&
 319             has_stopped_jobs(pgrp)) {
 320                 __kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
 321                 __kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
 322         }
 323 }
 324
 325 /**
 326  * reparent_to_kthreadd - Reparent the calling kernel thread to kthreadd
 327  *
 328  * If a kernel thread is launched as a result of a system call, or if
 329  * it ever exits, it should generally reparent itself to kthreadd so it
 330  * isn't in the way of other processes and is correctly cleaned up on exit.
 331  *
 332  * The various task state such as scheduling policy and priority may have
 333  * been inherited from a user process, so we reset them to sane values here.
 334  *
 335  * NOTE that reparent_to_kthreadd() gives the caller full capabilities.
 336  */
 337 static void reparent_to_kthreadd(void)
 338 {
 339         write_lock_irq(&tasklist_lock);
 340
 341         ptrace_unlink(current);
 342         /* Reparent to init */
 343         current->real_parent = current->parent = kthreadd_task;
 344         list_move_tail(&current->sibling, &current->real_parent->children);
 345
 346         /* Set the exit signal to SIGCHLD so we signal init on exit */
 347         current->exit_signal = SIGCHLD;
 348
 349         if (task_nice(current) < 0)
 350                 set_user_nice(current, 0);
 351         /* cpus_allowed? */
 352         /* rt_priority? */
 353         /* signals? */
 354         memcpy(current->signal->rlim, init_task.signal->rlim,
 355                sizeof(current->signal->rlim));
 356
 357         atomic_inc(&init_cred.usage);
 358         commit_creds(&init_cred);
 359         write_unlock_irq(&tasklist_lock);
 360 }
 361
 362 void __set_special_pids(struct pid *pid)
 363 {
 364         struct task_struct *curr = current->group_leader;
 365         pid_t nr = pid_nr(pid);
 366
 367         if (task_session(curr) != pid) {
 368                 change_pid(curr, PIDTYPE_SID, pid);
 369                 set_task_session(curr, nr);
 370         }
 371         if (task_pgrp(curr) != pid) {
 372                 change_pid(curr, PIDTYPE_PGID, pid);
 373                 set_task_pgrp(curr, nr);
 374         }
 375 }
 376
 377 static void set_special_pids(struct pid *pid)
 378 {
 379         write_lock_irq(&tasklist_lock);
 380         __set_special_pids(pid);
 381         write_unlock_irq(&tasklist_lock);
 382 }
 383
 384 /*
 385  * Let kernel threads use this to say that they
 386  * allow a certain signal (since daemonize() will
 387  * have disabled all of them by default).
 388  */
 389 int allow_signal(int sig)
 390 {
 391         if (!valid_signal(sig) || sig < 1)
 392                 return -EINVAL;
 393
 394         spin_lock_irq(&current->sighand->siglock);
 395         sigdelset(&current->blocked, sig);
 396         if (!current->mm) {
 397                 /* Kernel threads handle their own signals.
 398                    Let the signal code know it'll be handled, so
 399                    that they don't get converted to SIGKILL or
 400                    just silently dropped */
 401                 current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2;
 402         }
 403         recalc_sigpending();
 404         spin_unlock_irq(&current->sighand->siglock);
 405         return 0;
 406 }
 407
 408 EXPORT_SYMBOL(allow_signal);
 409
 410 int disallow_signal(int sig)
 411 {
 412         if (!valid_signal(sig) || sig < 1)
 413                 return -EINVAL;
 414
 415         spin_lock_irq(&current->sighand->siglock);
 416         current->sighand->action[(sig)-1].sa.sa_handler = SIG_IGN;
 417         recalc_sigpending();
 418         spin_unlock_irq(&current->sighand->siglock);
 419         return 0;
 420 }
 421
 422 EXPORT_SYMBOL(disallow_signal);
 423
 424 /*
 425  *      Put all the gunge required to become a kernel thread without
 426  *      attached user resources in one place where it belongs.
 427  */
 428
 429 void daemonize(const char *name, ...)
 430 {
 431         va_list args;
 432         struct fs_struct *fs;
 433         sigset_t blocked;
 434
 435         va_start(args, name);
 436         vsnprintf(current->comm, sizeof(current->comm), name, args);
 437         va_end(args);
 438
 439         /*
 440          * If we were started as result of loading a module, close all of the
 441          * user space pages.  We don't need them, and if we didn't close them
 442          * they would be locked into memory.
 443          */
 444         exit_mm(current);
 445         /*
 446          * We don't want to have TIF_FREEZE set if the system-wide hibernation
 447          * or suspend transition begins right now.
 448          */
 449         current->flags |= (PF_NOFREEZE | PF_KTHREAD);
 450
 451         if (current->nsproxy != &init_nsproxy) {
 452                 get_nsproxy(&init_nsproxy);
 453                 switch_task_namespaces(current, &init_nsproxy);
 454         }
 455         set_special_pids(&init_struct_pid);
 456         proc_clear_tty(current);
 457
 458         /* Block and flush all signals */
 459         sigfillset(&blocked);
 460         sigprocmask(SIG_BLOCK, &blocked, NULL);
 461         flush_signals(current);
 462
 463         /* Become as one with the init task */
 464
 465         exit_fs(current);       /* current->fs->count--; */
 466         fs = init_task.fs;
 467         current->fs = fs;
 468         atomic_inc(&fs->count);
 469
 470         exit_files(current);
 471         current->files = init_task.files;
 472         atomic_inc(&current->files->count);
 473
 474         reparent_to_kthreadd();
 475 }
 476
 477 EXPORT_SYMBOL(daemonize);
 478
 479 static void close_files(struct files_struct * files)
 480 {
 481         int i, j;
 482         struct fdtable *fdt;
 483
 484         j = 0;
 485
 486         /*
 487          * It is safe to dereference the fd table without RCU or
 488          * ->file_lock because this is the last reference to the
 489          * files structure.
 490          */
 491         fdt = files_fdtable(files);
 492         for (;;) {
 493                 unsigned long set;
 494                 i = j * __NFDBITS;
 495                 if (i >= fdt->max_fds)
 496                         break;
 497                 set = fdt->open_fds->fds_bits[j++];
 498                 while (set) {
 499                         if (set & 1) {
 500                                 struct file * file = xchg(&fdt->fd[i], NULL);
 501                                 if (file) {
 502                                         filp_close(file, files);
 503                                         cond_resched();
 504                                 }
 505                         }
 506                         i++;
 507                         set >>= 1;
 508                 }
 509         }
 510 }
 511
 512 struct files_struct *get_files_struct(struct task_struct *task)
 513 {
 514         struct files_struct *files;
 515
 516         task_lock(task);
 517         files = task->files;
 518         if (files)
 519                 atomic_inc(&files->count);
 520         task_unlock(task);
 521
 522         return files;
 523 }
 524
 525 void put_files_struct(struct files_struct *files)
 526 {
 527         struct fdtable *fdt;
 528
 529         if (atomic_dec_and_test(&files->count)) {
 530                 close_files(files);
 531                 /*
 532                  * Free the fd and fdset arrays if we expanded them.
 533                  * If the fdtable was embedded, pass files for freeing
 534                  * at the end of the RCU grace period. Otherwise,
 535                  * you can free files immediately.
 536                  */
 537                 fdt = files_fdtable(files);
 538                 if (fdt != &files->fdtab)
 539                         kmem_cache_free(files_cachep, files);
 540                 free_fdtable(fdt);
 541         }
 542 }
 543
 544 void reset_files_struct(struct files_struct *files)
 545 {
 546         struct task_struct *tsk = current;
 547         struct files_struct *old;
 548
 549         old = tsk->files;
 550         task_lock(tsk);
 551         tsk->files = files;
 552         task_unlock(tsk);
 553         put_files_struct(old);
 554 }
 555
 556 void exit_files(struct task_struct *tsk)
 557 {
 558         struct files_struct * files = tsk->files;
 559
 560         if (files) {
 561                 task_lock(tsk);
 562                 tsk->files = NULL;
 563                 task_unlock(tsk);
 564                 put_files_struct(files);
 565         }
 566 }
 567
 568 void put_fs_struct(struct fs_struct *fs)
 569 {
 570         /* No need to hold fs->lock if we are killing it */
 571         if (atomic_dec_and_test(&fs->count)) {
 572                 path_put(&fs->root);
 573                 path_put(&fs->pwd);
 574                 kmem_cache_free(fs_cachep, fs);
 575         }
 576 }
 577
 578 void exit_fs(struct task_struct *tsk)
 579 {
 580         struct fs_struct * fs = tsk->fs;
 581
 582         if (fs) {
 583                 task_lock(tsk);
 584                 tsk->fs = NULL;
 585                 task_unlock(tsk);
 586                 put_fs_struct(fs);
 587         }
 588 }
 589
 590 EXPORT_SYMBOL_GPL(exit_fs);
 591
 592 #ifdef CONFIG_MM_OWNER
 593 /*
 594  * Task p is exiting and it owned mm, lets find a new owner for it
 595  */
 596 static inline int
 597 mm_need_new_owner(struct mm_struct *mm, struct task_struct *p)
 598 {
 599         /*
 600          * If there are other users of the mm and the owner (us) is exiting
 601          * we need to find a new owner to take on the responsibility.
 602          */
 603         if (atomic_read(&mm->mm_users) <= 1)
 604                 return 0;
 605         if (mm->owner != p)
 606                 return 0;
 607         return 1;
 608 }
 609
 610 void mm_update_next_owner(struct mm_struct *mm)
 611 {
 612         struct task_struct *c, *g, *p = current;
 613
 614 retry:
 615         if (!mm_need_new_owner(mm, p))
 616                 return;
 617
 618         read_lock(&tasklist_lock);
 619         /*
 620          * Search in the children
 621          */
 622         list_for_each_entry(c, &p->children, sibling) {
 623                 if (c->mm == mm)
 624                         goto assign_new_owner;
 625         }
 626
 627         /*
 628          * Search in the siblings
 629          */
 630         list_for_each_entry(c, &p->parent->children, sibling) {
 631                 if (c->mm == mm)
 632                         goto assign_new_owner;
 633         }
 634
 635         /*
 636          * Search through everything else. We should not get
 637          * here often
 638          */
 639         do_each_thread(g, c) {
 640                 if (c->mm == mm)
 641                         goto assign_new_owner;
 642         } while_each_thread(g, c);
 643
 644         read_unlock(&tasklist_lock);
 645         /*
 646          * We found no owner yet mm_users > 1: this implies that we are
 647          * most likely racing with swapoff (try_to_unuse()) or /proc or
 648          * ptrace or page migration (get_task_mm()).  Mark owner as NULL.
 649          */
 650         mm->owner = NULL;
 651         return;
 652
 653 assign_new_owner:
 654         BUG_ON(c == p);
 655         get_task_struct(c);
 656         /*
 657          * The task_lock protects c->mm from changing.
 658          * We always want mm->owner->mm == mm
 659          */
 660         task_lock(c);
 661         /*
 662          * Delay read_unlock() till we have the task_lock()
 663          * to ensure that c does not slip away underneath us
 664          */
 665         read_unlock(&tasklist_lock);
 666         if (c->mm != mm) {
 667                 task_unlock(c);
 668                 put_task_struct(c);
 669                 goto retry;
 670         }
 671         mm->owner = c;
 672         task_unlock(c);
 673         put_task_struct(c);
 674 }
 675 #endif /* CONFIG_MM_OWNER */
 676
 677 /*
 678  * Turn us into a lazy TLB process if we
 679  * aren't already..
 680  */
 681 static void exit_mm(struct task_struct * tsk)
 682 {
 683         struct mm_struct *mm = tsk->mm;
 684         struct core_state *core_state;
 685
 686         mm_release(tsk, mm);
 687         if (!mm)
 688                 return;
 689         /*
 690          * Serialize with any possible pending coredump.
 691          * We must hold mmap_sem around checking core_state
 692          * and clearing tsk->mm.  The core-inducing thread
 693          * will increment ->nr_threads for each thread in the
 694          * group with ->mm != NULL.
 695          */
 696         down_read(&mm->mmap_sem);
 697         core_state = mm->core_state;
 698         if (core_state) {
 699                 struct core_thread self;
 700                 up_read(&mm->mmap_sem);
 701
 702                 self.task = tsk;
 703                 self.next = xchg(&core_state->dumper.next, &self);
 704                 /*
 705                  * Implies mb(), the result of xchg() must be visible
 706                  * to core_state->dumper.
 707                  */
 708                 if (atomic_dec_and_test(&core_state->nr_threads))
 709                         complete(&core_state->startup);
 710
 711                 for (;;) {
 712                         set_task_state(tsk, TASK_UNINTERRUPTIBLE);
 713                         if (!self.task) /* see coredump_finish() */
 714                                 break;
 715                         schedule();
 716                 }
 717                 __set_task_state(tsk, TASK_RUNNING);
 718                 down_read(&mm->mmap_sem);
 719         }
 720         atomic_inc(&mm->mm_count);
 721         BUG_ON(mm != tsk->active_mm);
 722         /* more a memory barrier than a real lock */
 723         task_lock(tsk);
 724         tsk->mm = NULL;
 725         up_read(&mm->mmap_sem);
 726         enter_lazy_tlb(mm, current);
 727         /* We don't want this task to be frozen prematurely */
 728         clear_freeze_flag(tsk);
 729         task_unlock(tsk);
 730         mm_update_next_owner(mm);
 731         mmput(mm);
 732 }
 733
 734 /*
 735  * Return nonzero if @parent's children should reap themselves.
 736  *
 737  * Called with write_lock_irq(&tasklist_lock) held.
 738  */
 739 static int ignoring_children(struct task_struct *parent)
 740 {
 741         int ret;
 742         struct sighand_struct *psig = parent->sighand;
 743         unsigned long flags;
 744         spin_lock_irqsave(&psig->siglock, flags);
 745         ret = (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN ||
 746                (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT));
 747         spin_unlock_irqrestore(&psig->siglock, flags);
 748         return ret;
 749 }
 750
 751 /*
 752  * Detach all tasks we were using ptrace on.
 753  * Any that need to be release_task'd are put on the @dead list.
 754  *
 755  * Called with write_lock(&tasklist_lock) held.
 756  */
 757 static void ptrace_exit(struct task_struct *parent, struct list_head *dead)
 758 {
 759         struct task_struct *p, *n;
 760         int ign = -1;
 761
 762         list_for_each_entry_safe(p, n, &parent->ptraced, ptrace_entry) {
 763                 __ptrace_unlink(p);
 764
 765                 if (p->exit_state != EXIT_ZOMBIE)
 766                         continue;
 767
 768                 /*
 769                  * If it's a zombie, our attachedness prevented normal
 770                  * parent notification or self-reaping.  Do notification
 771                  * now if it would have happened earlier.  If it should
 772                  * reap itself, add it to the @dead list.  We can't call
 773                  * release_task() here because we already hold tasklist_lock.
 774                  *
 775                  * If it's our own child, there is no notification to do.
 776                  * But if our normal children self-reap, then this child
 777                  * was prevented by ptrace and we must reap it now.
 778                  */
 779                 if (!task_detached(p) && thread_group_empty(p)) {
 780                         if (!same_thread_group(p->real_parent, parent))
 781                                 do_notify_parent(p, p->exit_signal);
 782                         else {
 783                                 if (ign < 0)
 784                                         ign = ignoring_children(parent);
 785                                 if (ign)
 786                                         p->exit_signal = -1;
 787                         }
 788                 }
 789
 790                 if (task_detached(p)) {
 791                         /*
 792                          * Mark it as in the process of being reaped.
 793                          */
 794                         p->exit_state = EXIT_DEAD;
 795                         list_add(&p->ptrace_entry, dead);
 796                 }
 797         }
 798 }
 799
 800 /*
 801  * Finish up exit-time ptrace cleanup.
 802  *
 803  * Called without locks.
 804  */
 805 static void ptrace_exit_finish(struct task_struct *parent,
 806                                struct list_head *dead)
 807 {
 808         struct task_struct *p, *n;
 809
 810         BUG_ON(!list_empty(&parent->ptraced));
 811
 812         list_for_each_entry_safe(p, n, dead, ptrace_entry) {
 813                 list_del_init(&p->ptrace_entry);
 814                 release_task(p);
 815         }
 816 }
 817
 818 static void reparent_thread(struct task_struct *p, struct task_struct *father)
 819 {
 820         if (p->pdeath_signal)
 821                 /* We already hold the tasklist_lock here.  */
 822                 group_send_sig_info(p->pdeath_signal, SEND_SIG_NOINFO, p);
 823
 824         list_move_tail(&p->sibling, &p->real_parent->children);
 825
 826         /* If this is a threaded reparent there is no need to
 827          * notify anyone anything has happened.
 828          */
 829         if (same_thread_group(p->real_parent, father))
 830                 return;
 831
 832         /* We don't want people slaying init.  */
 833         if (!task_detached(p))
 834                 p->exit_signal = SIGCHLD;
 835
 836         /* If we'd notified the old parent about this child's death,
 837          * also notify the new parent.
 838          */
 839         if (!ptrace_reparented(p) &&
 840             p->exit_state == EXIT_ZOMBIE &&
 841             !task_detached(p) && thread_group_empty(p))
 842                 do_notify_parent(p, p->exit_signal);
 843
 844         kill_orphaned_pgrp(p, father);
 845 }
 846
 847 /*
 848  * When we die, we re-parent all our children.
 849  * Try to give them to another thread in our thread
 850  * group, and if no such member exists, give it to
 851  * the child reaper process (ie "init") in our pid
 852  * space.
 853  */
 854 static struct task_struct *find_new_reaper(struct task_struct *father)
 855 {
 856         struct pid_namespace *pid_ns = task_active_pid_ns(father);
 857         struct task_struct *thread;
 858
 859         thread = father;
 860         while_each_thread(father, thread) {
 861                 if (thread->flags & PF_EXITING)
 862                         continue;
 863                 if (unlikely(pid_ns->child_reaper == father))
 864                         pid_ns->child_reaper = thread;
 865                 return thread;
 866         }
 867
 868         if (unlikely(pid_ns->child_reaper == father)) {
 869                 write_unlock_irq(&tasklist_lock);
 870                 if (unlikely(pid_ns == &init_pid_ns))
 871                         panic("Attempted to kill init!");
 872
 873                 zap_pid_ns_processes(pid_ns);
 874                 write_lock_irq(&tasklist_lock);
 875                 /*
 876                  * We can not clear ->child_reaper or leave it alone.
 877                  * There may by stealth EXIT_DEAD tasks on ->children,
 878                  * forget_original_parent() must move them somewhere.
 879                  */
 880                 pid_ns->child_reaper = init_pid_ns.child_reaper;
 881         }
 882
 883         return pid_ns->child_reaper;
 884 }
 885
 886 static void forget_original_parent(struct task_struct *father)
 887 {
 888         struct task_struct *p, *n, *reaper;
 889         LIST_HEAD(ptrace_dead);
 890
 891         write_lock_irq(&tasklist_lock);
 892         reaper = find_new_reaper(father);
 893         /*
 894          * First clean up ptrace if we were using it.
 895          */
 896         ptrace_exit(father, &ptrace_dead);
 897
 898         list_for_each_entry_safe(p, n, &father->children, sibling) {
 899                 p->real_parent = reaper;
 900                 if (p->parent == father) {
 901                         BUG_ON(p->ptrace);
 902                         p->parent = p->real_parent;
 903                 }
 904                 reparent_thread(p, father);
 905         }
 906
 907         write_unlock_irq(&tasklist_lock);
 908         BUG_ON(!list_empty(&father->children));
 909
 910         ptrace_exit_finish(father, &ptrace_dead);
 911 }
 912
 913 /*
 914  * Send signals to all our closest relatives so that they know
 915  * to properly mourn us..
 916  */
 917 static void exit_notify(struct task_struct *tsk, int group_dead)
 918 {
 919         int signal;
 920         void *cookie;
 921
 922         /*
 923          * This does two things:
 924          *
 925          * A.  Make init inherit all the child processes
 926          * B.  Check to see if any process groups have become orphaned
 927          *      as a result of our exiting, and if they have any stopped
 928          *      jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
 929          */
 930         forget_original_parent(tsk);
 931         exit_task_namespaces(tsk);
 932
 933         write_lock_irq(&tasklist_lock);
 934         if (group_dead)
 935                 kill_orphaned_pgrp(tsk->group_leader, NULL);
 936
 937         /* Let father know we died
 938          *
 939          * Thread signals are configurable, but you aren't going to use
 940          * that to send signals to arbitary processes.
 941          * That stops right now.
 942          *
 943          * If the parent exec id doesn't match the exec id we saved
 944          * when we started then we know the parent has changed security
 945          * domain.
 946          *
 947          * If our self_exec id doesn't match our parent_exec_id then
 948          * we have changed execution domain as these two values started
 949          * the same after a fork.
 950          */
 951         if (tsk->exit_signal != SIGCHLD && !task_detached(tsk) &&
 952             (tsk->parent_exec_id != tsk->real_parent->self_exec_id ||
 953              tsk->self_exec_id != tsk->parent_exec_id) &&
 954             !capable(CAP_KILL))
 955                 tsk->exit_signal = SIGCHLD;
 956
 957         signal = tracehook_notify_death(tsk, &cookie, group_dead);
 958         if (signal >= 0)
 959                 signal = do_notify_parent(tsk, signal);
 960
 961         tsk->exit_state = signal == DEATH_REAP ? EXIT_DEAD : EXIT_ZOMBIE;
 962
 963         /* mt-exec, de_thread() is waiting for us */
 964         if (thread_group_leader(tsk) &&
 965             tsk->signal->group_exit_task &&
 966             tsk->signal->notify_count < 0)
 967                 wake_up_process(tsk->signal->group_exit_task);
 968
 969         write_unlock_irq(&tasklist_lock);
 970
 971         tracehook_report_death(tsk, signal, cookie, group_dead);
 972
 973         /* If the process is dead, release it - nobody will wait for it */
 974         if (signal == DEATH_REAP)
 975                 release_task(tsk);
 976 }
 977
 978 #ifdef CONFIG_DEBUG_STACK_USAGE
 979 static void check_stack_usage(void)
 980 {
 981         static DEFINE_SPINLOCK(low_water_lock);
 982         static int lowest_to_date = THREAD_SIZE;
 983         unsigned long free;
 984
 985         free = stack_not_used(current);
 986
 987         if (free >= lowest_to_date)
 988                 return;
 989
 990         spin_lock(&low_water_lock);
 991         if (free < lowest_to_date) {
 992                 printk(KERN_WARNING "%s used greatest stack depth: %lu bytes "
 993                                 "left\n",
 994                                 current->comm, free);
 995                 lowest_to_date = free;
 996         }
 997         spin_unlock(&low_water_lock);
 998 }
 999 #else
1000 static inline void check_stack_usage(void) {}
1001 #endif
1002
1003 NORET_TYPE void do_exit(long code)
1004 {
1005         struct task_struct *tsk = current;
1006         int group_dead;
1007
1008         profile_task_exit(tsk);
1009
1010         WARN_ON(atomic_read(&tsk->fs_excl));
1011
1012         if (unlikely(in_interrupt()))
1013                 panic("Aiee, killing interrupt handler!");
1014         if (unlikely(!tsk->pid))
1015                 panic("Attempted to kill the idle task!");
1016
1017         tracehook_report_exit(&code);
1018
1019         /*
1020          * We're taking recursive faults here in do_exit. Safest is to just
1021          * leave this task alone and wait for reboot.
1022          */
1023         if (unlikely(tsk->flags & PF_EXITING)) {
1024                 printk(KERN_ALERT
1025                         "Fixing recursive fault but reboot is needed!\n");
1026                 /*
1027                  * We can do this unlocked here. The futex code uses
1028                  * this flag just to verify whether the pi state
1029                  * cleanup has been done or not. In the worst case it
1030                  * loops once more. We pretend that the cleanup was
1031                  * done as there is no way to return. Either the
1032                  * OWNER_DIED bit is set by now or we push the blocked
1033                  * task into the wait for ever nirwana as well.
1034                  */
1035                 tsk->flags |= PF_EXITPIDONE;
1036                 set_current_state(TASK_UNINTERRUPTIBLE);
1037                 schedule();
1038         }
1039
1040         exit_signals(tsk);  /* sets PF_EXITING */
1041         /*
1042          * tsk->flags are checked in the futex code to protect against
1043          * an exiting task cleaning up the robust pi futexes.
1044          */
1045         smp_mb();
1046         spin_unlock_wait(&tsk->pi_lock);
1047
1048         if (unlikely(in_atomic()))
1049                 printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
1050                                 current->comm, task_pid_nr(current),
1051                                 preempt_count());
1052
1053         acct_update_integrals(tsk);
1054
1055         group_dead = atomic_dec_and_test(&tsk->signal->live);
1056         if (group_dead) {
1057                 hrtimer_cancel(&tsk->signal->real_timer);
1058                 exit_itimers(tsk->signal);
1059         }
1060         acct_collect(code, group_dead);
1061         if (group_dead)
1062                 tty_audit_exit();
1063         if (unlikely(tsk->audit_context))
1064                 audit_free(tsk);
1065
1066         tsk->exit_code = code;
1067         taskstats_exit(tsk, group_dead);
1068
1069         exit_mm(tsk);
1070
1071         if (group_dead)
1072                 acct_process();
1073         trace_sched_process_exit(tsk);
1074
1075         exit_sem(tsk);
1076         exit_files(tsk);
1077         exit_fs(tsk);
1078         check_stack_usage();
1079         exit_thread();
1080         cgroup_exit(tsk, 1);
1081
1082         if (group_dead && tsk->signal->leader)
1083                 disassociate_ctty(1);
1084
1085         module_put(task_thread_info(tsk)->exec_domain->module);
1086         if (tsk->binfmt)
1087                 module_put(tsk->binfmt->module);
1088
1089         proc_exit_connector(tsk);
1090         exit_notify(tsk, group_dead);
1091 #ifdef CONFIG_NUMA
1092         mpol_put(tsk->mempolicy);
1093         tsk->mempolicy = NULL;
1094 #endif
1095 #ifdef CONFIG_FUTEX
1096         /*
1097          * This must happen late, after the PID is not
1098          * hashed anymore:
1099          */
1100         if (unlikely(!list_empty(&tsk->pi_state_list)))
1101                 exit_pi_state_list(tsk);
1102         if (unlikely(current->pi_state_cache))
1103                 kfree(current->pi_state_cache);
1104 #endif
1105         /*
1106          * Make sure we are holding no locks:
1107          */
1108         debug_check_no_locks_held(tsk);
1109         /*
1110          * We can do this unlocked here. The futex code uses this flag
1111          * just to verify whether the pi state cleanup has been done
1112          * or not. In the worst case it loops once more.
1113          */
1114         tsk->flags |= PF_EXITPIDONE;
1115
1116         if (tsk->io_context)
1117                 exit_io_context();
1118
1119         if (tsk->splice_pipe)
1120                 __free_pipe_info(tsk->splice_pipe);
1121
1122         preempt_disable();
1123         /* causes final put_task_struct in finish_task_switch(). */
1124         tsk->state = TASK_DEAD;
1125         schedule();
1126         BUG();
1127         /* Avoid "noreturn function does return".  */
1128         for (;;)
1129                 cpu_relax();    /* For when BUG is null */
1130 }
1131
1132 EXPORT_SYMBOL_GPL(do_exit);
1133
1134 NORET_TYPE void complete_and_exit(struct completion *comp, long code)
1135 {
1136         if (comp)
1137                 complete(comp);
1138
1139         do_exit(code);
1140 }
1141
1142 EXPORT_SYMBOL(complete_and_exit);
1143
1144 SYSCALL_DEFINE1(exit, int, error_code)
1145 {
1146         do_exit((error_code&0xff)<<8);
1147 }
1148
1149 /*
1150  * Take down every thread in the group.  This is called by fatal signals
1151  * as well as by sys_exit_group (below).
1152  */
1153 NORET_TYPE void
1154 do_group_exit(int exit_code)
1155 {
1156         struct signal_struct *sig = current->signal;
1157
1158         BUG_ON(exit_code & 0x80); /* core dumps don't get here */
1159
1160         if (signal_group_exit(sig))
1161                 exit_code = sig->group_exit_code;
1162         else if (!thread_group_empty(current)) {
1163                 struct sighand_struct *const sighand = current->sighand;
1164                 spin_lock_irq(&sighand->siglock);
1165                 if (signal_group_exit(sig))
1166                         /* Another thread got here before we took the lock.  */
1167                         exit_code = sig->group_exit_code;
1168                 else {
1169                         sig->group_exit_code = exit_code;
1170                         sig->flags = SIGNAL_GROUP_EXIT;
1171                         zap_other_threads(current);
1172                 }
1173                 spin_unlock_irq(&sighand->siglock);
1174         }
1175
1176         do_exit(exit_code);
1177         /* NOTREACHED */
1178 }
1179
1180 /*
1181  * this kills every thread in the thread group. Note that any externally
1182  * wait4()-ing process will get the correct exit code - even if this
1183  * thread is not the thread group leader.
1184  */
1185 SYSCALL_DEFINE1(exit_group, int, error_code)
1186 {
1187         do_group_exit((error_code & 0xff) << 8);
1188         /* NOTREACHED */
1189         return 0;
1190 }
1191
1192 static struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
1193 {
1194         struct pid *pid = NULL;
1195         if (type == PIDTYPE_PID)
1196                 pid = task->pids[type].pid;
1197         else if (type < PIDTYPE_MAX)
1198                 pid = task->group_leader->pids[type].pid;
1199         return pid;
1200 }
1201
1202 static int eligible_child(enum pid_type type, struct pid *pid, int options,
1203                           struct task_struct *p)
1204 {
1205         int err;
1206
1207         if (type < PIDTYPE_MAX) {
1208                 if (task_pid_type(p, type) != pid)
1209                         return 0;
1210         }
1211
1212         /* Wait for all children (clone and not) if __WALL is set;
1213          * otherwise, wait for clone children *only* if __WCLONE is
1214          * set; otherwise, wait for non-clone children *only*.  (Note:
1215          * A "clone" child here is one that reports to its parent
1216          * using a signal other than SIGCHLD.) */
1217         if (((p->exit_signal != SIGCHLD) ^ ((options & __WCLONE) != 0))
1218             && !(options & __WALL))
1219                 return 0;
1220
1221         err = security_task_wait(p);
1222         if (err)
1223                 return err;
1224
1225         return 1;
1226 }
1227
1228 static int wait_noreap_copyout(struct task_struct *p, pid_t pid, uid_t uid,
1229                                int why, int status,
1230                                struct siginfo __user *infop,
1231                                struct rusage __user *rusagep)
1232 {
1233         int retval = rusagep ? getrusage(p, RUSAGE_BOTH, rusagep) : 0;
1234
1235         put_task_struct(p);
1236         if (!retval)
1237                 retval = put_user(SIGCHLD, &infop->si_signo);
1238         if (!retval)
1239                 retval = put_user(0, &infop->si_errno);
1240         if (!retval)
1241                 retval = put_user((short)why, &infop->si_code);
1242         if (!retval)
1243                 retval = put_user(pid, &infop->si_pid);
1244         if (!retval)
1245                 retval = put_user(uid, &infop->si_uid);
1246         if (!retval)
1247                 retval = put_user(status, &infop->si_status);
1248         if (!retval)
1249                 retval = pid;
1250         return retval;
1251 }
1252
1253 /*
1254  * Handle sys_wait4 work for one task in state EXIT_ZOMBIE.  We hold
1255  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1256  * the lock and this task is uninteresting.  If we return nonzero, we have
1257  * released the lock and the system call should return.
1258  */
1259 static int wait_task_zombie(struct task_struct *p, int options,
1260                             struct siginfo __user *infop,
1261                             int __user *stat_addr, struct rusage __user *ru)
1262 {
1263         unsigned long state;
1264         int retval, status, traced;
1265         pid_t pid = task_pid_vnr(p);
1266         uid_t uid = __task_cred(p)->uid;
1267
1268         if (!likely(options & WEXITED))
1269                 return 0;
1270
1271         if (unlikely(options & WNOWAIT)) {
1272                 int exit_code = p->exit_code;
1273                 int why, status;
1274
1275                 get_task_struct(p);
1276                 read_unlock(&tasklist_lock);
1277                 if ((exit_code & 0x7f) == 0) {
1278                         why = CLD_EXITED;
1279                         status = exit_code >> 8;
1280                 } else {
1281                         why = (exit_code & 0x80) ? CLD_DUMPED : CLD_KILLED;
1282                         status = exit_code & 0x7f;
1283                 }
1284                 return wait_noreap_copyout(p, pid, uid, why,
1285                                            status, infop, ru);
1286         }
1287
1288         /*
1289          * Try to move the task's state to DEAD
1290          * only one thread is allowed to do this:
1291          */
1292         state = xchg(&p->exit_state, EXIT_DEAD);
1293         if (state != EXIT_ZOMBIE) {
1294                 BUG_ON(state != EXIT_DEAD);
1295                 return 0;
1296         }
1297
1298         traced = ptrace_reparented(p);
1299
1300         if (likely(!traced)) {
1301                 struct signal_struct *psig;
1302                 struct signal_struct *sig;
1303                 struct task_cputime cputime;
1304
1305                 /*
1306                  * The resource counters for the group leader are in its
1307                  * own task_struct.  Those for dead threads in the group
1308                  * are in its signal_struct, as are those for the child
1309                  * processes it has previously reaped.  All these
1310                  * accumulate in the parent's signal_struct c* fields.
1311                  *
1312                  * We don't bother to take a lock here to protect these
1313                  * p->signal fields, because they are only touched by
1314                  * __exit_signal, which runs with tasklist_lock
1315                  * write-locked anyway, and so is excluded here.  We do
1316                  * need to protect the access to p->parent->signal fields,
1317                  * as other threads in the parent group can be right
1318                  * here reaping other children at the same time.
1319                  *
1320                  * We use thread_group_cputime() to get times for the thread
1321                  * group, which consolidates times for all threads in the
1322                  * group including the group leader.
1323                  */
1324                 thread_group_cputime(p, &cputime);
1325                 spin_lock_irq(&p->parent->sighand->siglock);
1326                 psig = p->parent->signal;
1327                 sig = p->signal;
1328                 psig->cutime =
1329                         cputime_add(psig->cutime,
1330                         cputime_add(cputime.utime,
1331                                     sig->cutime));
1332                 psig->cstime =
1333                         cputime_add(psig->cstime,
1334                         cputime_add(cputime.stime,
1335                                     sig->cstime));
1336                 psig->cgtime =
1337                         cputime_add(psig->cgtime,
1338                         cputime_add(p->gtime,
1339                         cputime_add(sig->gtime,
1340                                     sig->cgtime)));
1341                 psig->cmin_flt +=
1342                         p->min_flt + sig->min_flt + sig->cmin_flt;
1343                 psig->cmaj_flt +=
1344                         p->maj_flt + sig->maj_flt + sig->cmaj_flt;
1345                 psig->cnvcsw +=
1346                         p->nvcsw + sig->nvcsw + sig->cnvcsw;
1347                 psig->cnivcsw +=
1348                         p->nivcsw + sig->nivcsw + sig->cnivcsw;
1349                 psig->cinblock +=
1350                         task_io_get_inblock(p) +
1351                         sig->inblock + sig->cinblock;
1352                 psig->coublock +=
1353                         task_io_get_oublock(p) +
1354                         sig->oublock + sig->coublock;
1355                 task_io_accounting_add(&psig->ioac, &p->ioac);
1356                 task_io_accounting_add(&psig->ioac, &sig->ioac);
1357                 spin_unlock_irq(&p->parent->sighand->siglock);
1358         }
1359
1360         /*
1361          * Now we are sure this task is interesting, and no other
1362          * thread can reap it because we set its state to EXIT_DEAD.
1363          */
1364         read_unlock(&tasklist_lock);
1365
1366         retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
1367         status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1368                 ? p->signal->group_exit_code : p->exit_code;
1369         if (!retval && stat_addr)
1370                 retval = put_user(status, stat_addr);
1371         if (!retval && infop)
1372                 retval = put_user(SIGCHLD, &infop->si_signo);
1373         if (!retval && infop)
1374                 retval = put_user(0, &infop->si_errno);
1375         if (!retval && infop) {
1376                 int why;
1377
1378                 if ((status & 0x7f) == 0) {
1379                         why = CLD_EXITED;
1380                         status >>= 8;
1381                 } else {
1382                         why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
1383                         status &= 0x7f;
1384                 }
1385                 retval = put_user((short)why, &infop->si_code);
1386                 if (!retval)
1387                         retval = put_user(status, &infop->si_status);
1388         }
1389         if (!retval && infop)
1390                 retval = put_user(pid, &infop->si_pid);
1391         if (!retval && infop)
1392                 retval = put_user(uid, &infop->si_uid);
1393         if (!retval)
1394                 retval = pid;
1395
1396         if (traced) {
1397                 write_lock_irq(&tasklist_lock);
1398                 /* We dropped tasklist, ptracer could die and untrace */
1399                 ptrace_unlink(p);
1400                 /*
1401                  * If this is not a detached task, notify the parent.
1402                  * If it's still not detached after that, don't release
1403                  * it now.
1404                  */
1405                 if (!task_detached(p)) {
1406                         do_notify_parent(p, p->exit_signal);
1407                         if (!task_detached(p)) {
1408                                 p->exit_state = EXIT_ZOMBIE;
1409                                 p = NULL;
1410                         }
1411                 }
1412                 write_unlock_irq(&tasklist_lock);
1413         }
1414         if (p != NULL)
1415                 release_task(p);
1416
1417         return retval;
1418 }
1419
1420 /*
1421  * Handle sys_wait4 work for one task in state TASK_STOPPED.  We hold
1422  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1423  * the lock and this task is uninteresting.  If we return nonzero, we have
1424  * released the lock and the system call should return.
1425  */
1426 static int wait_task_stopped(int ptrace, struct task_struct *p,
1427                              int options, struct siginfo __user *infop,
1428                              int __user *stat_addr, struct rusage __user *ru)
1429 {
1430         int retval, exit_code, why;
1431         uid_t uid = 0; /* unneeded, required by compiler */
1432         pid_t pid;
1433
1434         if (!(options & WUNTRACED))
1435                 return 0;
1436
1437         exit_code = 0;
1438         spin_lock_irq(&p->sighand->siglock);
1439
1440         if (unlikely(!task_is_stopped_or_traced(p)))
1441                 goto unlock_sig;
1442
1443         if (!ptrace && p->signal->group_stop_count > 0)
1444                 /*
1445                  * A group stop is in progress and this is the group leader.
1446                  * We won't report until all threads have stopped.
1447                  */
1448                 goto unlock_sig;
1449
1450         exit_code = p->exit_code;
1451         if (!exit_code)
1452                 goto unlock_sig;
1453
1454         if (!unlikely(options & WNOWAIT))
1455                 p->exit_code = 0;
1456
1457         /* don't need the RCU readlock here as we're holding a spinlock */
1458         uid = __task_cred(p)->uid;
1459 unlock_sig:
1460         spin_unlock_irq(&p->sighand->siglock);
1461         if (!exit_code)
1462                 return 0;
1463
1464         /*
1465          * Now we are pretty sure this task is interesting.
1466          * Make sure it doesn't get reaped out from under us while we
1467          * give up the lock and then examine it below.  We don't want to
1468          * keep holding onto the tasklist_lock while we call getrusage and
1469          * possibly take page faults for user memory.
1470          */
1471         get_task_struct(p);
1472         pid = task_pid_vnr(p);
1473         why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
1474         read_unlock(&tasklist_lock);
1475
1476         if (unlikely(options & WNOWAIT))
1477                 return wait_noreap_copyout(p, pid, uid,
1478                                            why, exit_code,
1479                                            infop, ru);
1480
1481         retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
1482         if (!retval && stat_addr)
1483                 retval = put_user((exit_code << 8) | 0x7f, stat_addr);
1484         if (!retval && infop)
1485                 retval = put_user(SIGCHLD, &infop->si_signo);
1486         if (!retval && infop)
1487                 retval = put_user(0, &infop->si_errno);
1488         if (!retval && infop)
1489                 retval = put_user((short)why, &infop->si_code);
1490         if (!retval && infop)
1491                 retval = put_user(exit_code, &infop->si_status);
1492         if (!retval && infop)
1493                 retval = put_user(pid, &infop->si_pid);
1494         if (!retval && infop)
1495                 retval = put_user(uid, &infop->si_uid);
1496         if (!retval)
1497                 retval = pid;
1498         put_task_struct(p);
1499
1500         BUG_ON(!retval);
1501         return retval;
1502 }
1503
1504 /*
1505  * Handle do_wait work for one task in a live, non-stopped state.
1506  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1507  * the lock and this task is uninteresting.  If we return nonzero, we have
1508  * released the lock and the system call should return.
1509  */
1510 static int wait_task_continued(struct task_struct *p, int options,
1511                                struct siginfo __user *infop,
1512                                int __user *stat_addr, struct rusage __user *ru)
1513 {
1514         int retval;
1515         pid_t pid;
1516         uid_t uid;
1517
1518         if (!unlikely(options & WCONTINUED))
1519                 return 0;
1520
1521         if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
1522                 return 0;
1523
1524         spin_lock_irq(&p->sighand->siglock);
1525         /* Re-check with the lock held.  */
1526         if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
1527                 spin_unlock_irq(&p->sighand->siglock);
1528                 return 0;
1529         }
1530         if (!unlikely(options & WNOWAIT))
1531                 p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1532         uid = __task_cred(p)->uid;
1533         spin_unlock_irq(&p->sighand->siglock);
1534
1535         pid = task_pid_vnr(p);
1536         get_task_struct(p);
1537         read_unlock(&tasklist_lock);
1538
1539         if (!infop) {
1540                 retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
1541                 put_task_struct(p);
1542                 if (!retval && stat_addr)
1543                         retval = put_user(0xffff, stat_addr);
1544                 if (!retval)
1545                         retval = pid;
1546         } else {
1547                 retval = wait_noreap_copyout(p, pid, uid,
1548                                              CLD_CONTINUED, SIGCONT,
1549                                              infop, ru);
1550                 BUG_ON(retval == 0);
1551         }
1552
1553         return retval;
1554 }
1555
1556 /*
1557  * Consider @p for a wait by @parent.
1558  *
1559  * -ECHILD should be in *@notask_error before the first call.
1560  * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1561  * Returns zero if the search for a child should continue;
1562  * then *@notask_error is 0 if @p is an eligible child,
1563  * or another error from security_task_wait(), or still -ECHILD.
1564  */
1565 static int wait_consider_task(struct task_struct *parent, int ptrace,
1566                               struct task_struct *p, int *notask_error,
1567                               enum pid_type type, struct pid *pid, int options,
1568                               struct siginfo __user *infop,
1569                               int __user *stat_addr, struct rusage __user *ru)
1570 {
1571         int ret = eligible_child(type, pid, options, p);
1572         if (!ret)
1573                 return ret;
1574
1575         if (unlikely(ret < 0)) {
1576                 /*
1577                  * If we have not yet seen any eligible child,
1578                  * then let this error code replace -ECHILD.
1579                  * A permission error will give the user a clue
1580                  * to look for security policy problems, rather
1581                  * than for mysterious wait bugs.
1582                  */
1583                 if (*notask_error)
1584                         *notask_error = ret;
1585         }
1586
1587         if (likely(!ptrace) && unlikely(p->ptrace)) {
1588                 /*
1589                  * This child is hidden by ptrace.
1590                  * We aren't allowed to see it now, but eventually we will.
1591                  */
1592                 *notask_error = 0;
1593                 return 0;
1594         }
1595
1596         if (p->exit_state == EXIT_DEAD)
1597                 return 0;
1598
1599         /*
1600          * We don't reap group leaders with subthreads.
1601          */
1602         if (p->exit_state == EXIT_ZOMBIE && !delay_group_leader(p))
1603                 return wait_task_zombie(p, options, infop, stat_addr, ru);
1604
1605         /*
1606          * It's stopped or running now, so it might
1607          * later continue, exit, or stop again.
1608          */
1609         *notask_error = 0;
1610
1611         if (task_is_stopped_or_traced(p))
1612                 return wait_task_stopped(ptrace, p, options,
1613                                          infop, stat_addr, ru);
1614
1615         return wait_task_continued(p, options, infop, stat_addr, ru);
1616 }
1617
1618 /*
1619  * Do the work of do_wait() for one thread in the group, @tsk.
1620  *
1621  * -ECHILD should be in *@notask_error before the first call.
1622  * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1623  * Returns zero if the search for a child should continue; then
1624  * *@notask_error is 0 if there were any eligible children,
1625  * or another error from security_task_wait(), or still -ECHILD.
1626  */
1627 static int do_wait_thread(struct task_struct *tsk, int *notask_error,
1628                           enum pid_type type, struct pid *pid, int options,
1629                           struct siginfo __user *infop, int __user *stat_addr,
1630                           struct rusage __user *ru)
1631 {
1632         struct task_struct *p;
1633
1634         list_for_each_entry(p, &tsk->children, sibling) {
1635                 /*
1636                  * Do not consider detached threads.
1637                  */
1638                 if (!task_detached(p)) {
1639                         int ret = wait_consider_task(tsk, 0, p, notask_error,
1640                                                      type, pid, options,
1641                                                      infop, stat_addr, ru);
1642                         if (ret)
1643                                 return ret;
1644                 }
1645         }
1646
1647         return 0;
1648 }
1649
1650 static int ptrace_do_wait(struct task_struct *tsk, int *notask_error,
1651                           enum pid_type type, struct pid *pid, int options,
1652                           struct siginfo __user *infop, int __user *stat_addr,
1653                           struct rusage __user *ru)
1654 {
1655         struct task_struct *p;
1656
1657         /*
1658          * Traditionally we see ptrace'd stopped tasks regardless of options.
1659          */
1660         options |= WUNTRACED;
1661
1662         list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
1663                 int ret = wait_consider_task(tsk, 1, p, notask_error,
1664                                              type, pid, options,
1665                                              infop, stat_addr, ru);
1666                 if (ret)
1667                         return ret;
1668         }
1669
1670         return 0;
1671 }
1672
1673 static long do_wait(enum pid_type type, struct pid *pid, int options,
1674                     struct siginfo __user *infop, int __user *stat_addr,
1675                     struct rusage __user *ru)
1676 {
1677         DECLARE_WAITQUEUE(wait, current);
1678         struct task_struct *tsk;
1679         int retval;
1680
1681         trace_sched_process_wait(pid);
1682
1683         add_wait_queue(&current->signal->wait_chldexit,&wait);
1684 repeat:
1685         /*
1686          * If there is nothing that can match our critiera just get out.
1687          * We will clear @retval to zero if we see any child that might later
1688          * match our criteria, even if we are not able to reap it yet.
1689          */
1690         retval = -ECHILD;
1691         if ((type < PIDTYPE_MAX) && (!pid || hlist_empty(&pid->tasks[type])))
1692                 goto end;
1693
1694         current->state = TASK_INTERRUPTIBLE;
1695         read_lock(&tasklist_lock);
1696         tsk = current;
1697         do {
1698                 int tsk_result = do_wait_thread(tsk, &retval,
1699                                                 type, pid, options,
1700                                                 infop, stat_addr, ru);
1701                 if (!tsk_result)
1702                         tsk_result = ptrace_do_wait(tsk, &retval,
1703                                                     type, pid, options,
1704                                                     infop, stat_addr, ru);
1705                 if (tsk_result) {
1706                         /*
1707                          * tasklist_lock is unlocked and we have a final result.
1708                          */
1709                         retval = tsk_result;
1710                         goto end;
1711                 }
1712
1713                 if (options & __WNOTHREAD)
1714                         break;
1715                 tsk = next_thread(tsk);
1716                 BUG_ON(tsk->signal != current->signal);
1717         } while (tsk != current);
1718         read_unlock(&tasklist_lock);
1719
1720         if (!retval && !(options & WNOHANG)) {
1721                 retval = -ERESTARTSYS;
1722                 if (!signal_pending(current)) {
1723                         schedule();
1724                         goto repeat;
1725                 }
1726         }
1727
1728 end:
1729         current->state = TASK_RUNNING;
1730         remove_wait_queue(&current->signal->wait_chldexit,&wait);
1731         if (infop) {
1732                 if (retval > 0)
1733                         retval = 0;
1734                 else {
1735                         /*
1736                          * For a WNOHANG return, clear out all the fields
1737                          * we would set so the user can easily tell the
1738                          * difference.
1739                          */
1740                         if (!retval)
1741                                 retval = put_user(0, &infop->si_signo);
1742                         if (!retval)
1743                                 retval = put_user(0, &infop->si_errno);
1744                         if (!retval)
1745                                 retval = put_user(0, &infop->si_code);
1746                         if (!retval)
1747                                 retval = put_user(0, &infop->si_pid);
1748                         if (!retval)
1749                                 retval = put_user(0, &infop->si_uid);
1750                         if (!retval)
1751                                 retval = put_user(0, &infop->si_status);
1752                 }
1753         }
1754         return retval;
1755 }
1756
1757 SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
1758                 infop, int, options, struct rusage __user *, ru)
1759 {
1760         struct pid *pid = NULL;
1761         enum pid_type type;
1762         long ret;
1763
1764         if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED))
1765                 return -EINVAL;
1766         if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
1767                 return -EINVAL;
1768
1769         switch (which) {
1770         case P_ALL:
1771                 type = PIDTYPE_MAX;
1772                 break;
1773         case P_PID:
1774                 type = PIDTYPE_PID;
1775                 if (upid <= 0)
1776                         return -EINVAL;
1777                 break;
1778         case P_PGID:
1779                 type = PIDTYPE_PGID;
1780                 if (upid <= 0)
1781                         return -EINVAL;
1782                 break;
1783         default:
1784                 return -EINVAL;
1785         }
1786
1787         if (type < PIDTYPE_MAX)
1788                 pid = find_get_pid(upid);
1789         ret = do_wait(type, pid, options, infop, NULL, ru);
1790         put_pid(pid);
1791
1792         /* avoid REGPARM breakage on x86: */
1793         asmlinkage_protect(5, ret, which, upid, infop, options, ru);
1794         return ret;
1795 }
1796
1797 SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
1798                 int, options, struct rusage __user *, ru)
1799 {
1800         struct pid *pid = NULL;
1801         enum pid_type type;
1802         long ret;
1803
1804         if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
1805                         __WNOTHREAD|__WCLONE|__WALL))
1806                 return -EINVAL;
1807
1808         if (upid == -1)
1809                 type = PIDTYPE_MAX;
1810         else if (upid < 0) {
1811                 type = PIDTYPE_PGID;
1812                 pid = find_get_pid(-upid);
1813         } else if (upid == 0) {
1814                 type = PIDTYPE_PGID;
1815                 pid = get_pid(task_pgrp(current));
1816         } else /* upid > 0 */ {
1817                 type = PIDTYPE_PID;
1818                 pid = find_get_pid(upid);
1819         }
1820
1821         ret = do_wait(type, pid, options | WEXITED, NULL, stat_addr, ru);
1822         put_pid(pid);
1823
1824         /* avoid REGPARM breakage on x86: */
1825         asmlinkage_protect(4, ret, upid, stat_addr, options, ru);
1826         return ret;
1827 }
1828
1829 #ifdef __ARCH_WANT_SYS_WAITPID
1830
1831 /*
1832  * sys_waitpid() remains for compatibility. waitpid() should be
1833  * implemented by calling sys_wait4() from libc.a.
1834  */
1835 SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options)
1836 {
1837         return sys_wait4(pid, stat_addr, options, NULL);
1838 }
1839
1840 #endif