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