CRED: Use RCU to access another task's creds and to release a task's own creds
[linux-2.6.git] / 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 #include <linux/tracehook.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
57 static void exit_mm(struct task_struct * tsk);
58
59 static inline int task_detached(struct task_struct *p)
60 {
61         return p->exit_signal == -1;
62 }
63
64 static void __unhash_process(struct task_struct *p)
65 {
66         nr_threads--;
67         detach_pid(p, PIDTYPE_PID);
68         if (thread_group_leader(p)) {
69                 detach_pid(p, PIDTYPE_PGID);
70                 detach_pid(p, PIDTYPE_SID);
71
72                 list_del_rcu(&p->tasks);
73                 __get_cpu_var(process_counts)--;
74         }
75         list_del_rcu(&p->thread_group);
76         list_del_init(&p->sibling);
77 }
78
79 /*
80  * This function expects the tasklist_lock write-locked.
81  */
82 static void __exit_signal(struct task_struct *tsk)
83 {
84         struct signal_struct *sig = tsk->signal;
85         struct sighand_struct *sighand;
86
87         BUG_ON(!sig);
88         BUG_ON(!atomic_read(&sig->count));
89
90         sighand = rcu_dereference(tsk->sighand);
91         spin_lock(&sighand->siglock);
92
93         posix_cpu_timers_exit(tsk);
94         if (atomic_dec_and_test(&sig->count))
95                 posix_cpu_timers_exit_group(tsk);
96         else {
97                 /*
98                  * If there is any task waiting for the group exit
99                  * then notify it:
100                  */
101                 if (sig->group_exit_task && atomic_read(&sig->count) == sig->notify_count)
102                         wake_up_process(sig->group_exit_task);
103
104                 if (tsk == sig->curr_target)
105                         sig->curr_target = next_thread(tsk);
106                 /*
107                  * Accumulate here the counters for all threads but the
108                  * group leader as they die, so they can be added into
109                  * the process-wide totals when those are taken.
110                  * The group leader stays around as a zombie as long
111                  * as there are other threads.  When it gets reaped,
112                  * the exit.c code will add its counts into these totals.
113                  * We won't ever get here for the group leader, since it
114                  * will have been the last reference on the signal_struct.
115                  */
116                 sig->gtime = cputime_add(sig->gtime, task_gtime(tsk));
117                 sig->min_flt += tsk->min_flt;
118                 sig->maj_flt += tsk->maj_flt;
119                 sig->nvcsw += tsk->nvcsw;
120                 sig->nivcsw += tsk->nivcsw;
121                 sig->inblock += task_io_get_inblock(tsk);
122                 sig->oublock += task_io_get_oublock(tsk);
123                 task_io_accounting_add(&sig->ioac, &tsk->ioac);
124                 sig = NULL; /* Marker for below. */
125         }
126
127         __unhash_process(tsk);
128
129         /*
130          * Do this under ->siglock, we can race with another thread
131          * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals.
132          */
133         flush_sigqueue(&tsk->pending);
134
135         tsk->signal = NULL;
136         tsk->sighand = NULL;
137         spin_unlock(&sighand->siglock);
138
139         __cleanup_sighand(sighand);
140         clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
141         if (sig) {
142                 flush_sigqueue(&sig->shared_pending);
143                 taskstats_tgid_free(sig);
144                 __cleanup_signal(sig);
145         }
146 }
147
148 static void delayed_put_task_struct(struct rcu_head *rhp)
149 {
150         struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
151
152         trace_sched_process_free(tsk);
153         put_task_struct(tsk);
154 }
155
156
157 void release_task(struct task_struct * p)
158 {
159         struct task_struct *leader;
160         int zap_leader;
161 repeat:
162         tracehook_prepare_release_task(p);
163         /* don't need to get the RCU readlock here - the process is dead and
164          * can't be modifying its own credentials */
165         atomic_dec(&__task_cred(p)->user->processes);
166
167         proc_flush_task(p);
168         write_lock_irq(&tasklist_lock);
169         tracehook_finish_release_task(p);
170         __exit_signal(p);
171
172         /*
173          * If we are the last non-leader member of the thread
174          * group, and the leader is zombie, then notify the
175          * group leader's parent process. (if it wants notification.)
176          */
177         zap_leader = 0;
178         leader = p->group_leader;
179         if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
180                 BUG_ON(task_detached(leader));
181                 do_notify_parent(leader, leader->exit_signal);
182                 /*
183                  * If we were the last child thread and the leader has
184                  * exited already, and the leader's parent ignores SIGCHLD,
185                  * then we are the one who should release the leader.
186                  *
187                  * do_notify_parent() will have marked it self-reaping in
188                  * that case.
189                  */
190                 zap_leader = task_detached(leader);
191
192                 /*
193                  * This maintains the invariant that release_task()
194                  * only runs on a task in EXIT_DEAD, just for sanity.
195                  */
196                 if (zap_leader)
197                         leader->exit_state = EXIT_DEAD;
198         }
199
200         write_unlock_irq(&tasklist_lock);
201         release_thread(p);
202         call_rcu(&p->rcu, delayed_put_task_struct);
203
204         p = leader;
205         if (unlikely(zap_leader))
206                 goto repeat;
207 }
208
209 /*
210  * This checks not only the pgrp, but falls back on the pid if no
211  * satisfactory pgrp is found. I dunno - gdb doesn't work correctly
212  * without this...
213  *
214  * The caller must hold rcu lock or the tasklist lock.
215  */
216 struct pid *session_of_pgrp(struct pid *pgrp)
217 {
218         struct task_struct *p;
219         struct pid *sid = NULL;
220
221         p = pid_task(pgrp, PIDTYPE_PGID);
222         if (p == NULL)
223                 p = pid_task(pgrp, PIDTYPE_PID);
224         if (p != NULL)
225                 sid = task_session(p);
226
227         return sid;
228 }
229
230 /*
231  * Determine if a process group is "orphaned", according to the POSIX
232  * definition in 2.2.2.52.  Orphaned process groups are not to be affected
233  * by terminal-generated stop signals.  Newly orphaned process groups are
234  * to receive a SIGHUP and a SIGCONT.
235  *
236  * "I ask you, have you ever known what it is to be an orphan?"
237  */
238 static int will_become_orphaned_pgrp(struct pid *pgrp, struct task_struct *ignored_task)
239 {
240         struct task_struct *p;
241
242         do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
243                 if ((p == ignored_task) ||
244                     (p->exit_state && thread_group_empty(p)) ||
245                     is_global_init(p->real_parent))
246                         continue;
247
248                 if (task_pgrp(p->real_parent) != pgrp &&
249                     task_session(p->real_parent) == task_session(p))
250                         return 0;
251         } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
252
253         return 1;
254 }
255
256 int is_current_pgrp_orphaned(void)
257 {
258         int retval;
259
260         read_lock(&tasklist_lock);
261         retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
262         read_unlock(&tasklist_lock);
263
264         return retval;
265 }
266
267 static int has_stopped_jobs(struct pid *pgrp)
268 {
269         int retval = 0;
270         struct task_struct *p;
271
272         do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
273                 if (!task_is_stopped(p))
274                         continue;
275                 retval = 1;
276                 break;
277         } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
278         return retval;
279 }
280
281 /*
282  * Check to see if any process groups have become orphaned as
283  * a result of our exiting, and if they have any stopped jobs,
284  * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
285  */
286 static void
287 kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent)
288 {
289         struct pid *pgrp = task_pgrp(tsk);
290         struct task_struct *ignored_task = tsk;
291
292         if (!parent)
293                  /* exit: our father is in a different pgrp than
294                   * we are and we were the only connection outside.
295                   */
296                 parent = tsk->real_parent;
297         else
298                 /* reparent: our child is in a different pgrp than
299                  * we are, and it was the only connection outside.
300                  */
301                 ignored_task = NULL;
302
303         if (task_pgrp(parent) != pgrp &&
304             task_session(parent) == task_session(tsk) &&
305             will_become_orphaned_pgrp(pgrp, ignored_task) &&
306             has_stopped_jobs(pgrp)) {
307                 __kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
308                 __kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
309         }
310 }
311
312 /**
313  * reparent_to_kthreadd - Reparent the calling kernel thread to kthreadd
314  *
315  * If a kernel thread is launched as a result of a system call, or if
316  * it ever exits, it should generally reparent itself to kthreadd so it
317  * isn't in the way of other processes and is correctly cleaned up on exit.
318  *
319  * The various task state such as scheduling policy and priority may have
320  * been inherited from a user process, so we reset them to sane values here.
321  *
322  * NOTE that reparent_to_kthreadd() gives the caller full capabilities.
323  */
324 static void reparent_to_kthreadd(void)
325 {
326         write_lock_irq(&tasklist_lock);
327
328         ptrace_unlink(current);
329         /* Reparent to init */
330         current->real_parent = current->parent = kthreadd_task;
331         list_move_tail(&current->sibling, &current->real_parent->children);
332
333         /* Set the exit signal to SIGCHLD so we signal init on exit */
334         current->exit_signal = SIGCHLD;
335
336         if (task_nice(current) < 0)
337                 set_user_nice(current, 0);
338         /* cpus_allowed? */
339         /* rt_priority? */
340         /* signals? */
341         security_task_reparent_to_init(current);
342         memcpy(current->signal->rlim, init_task.signal->rlim,
343                sizeof(current->signal->rlim));
344         atomic_inc(&(INIT_USER->__count));
345         write_unlock_irq(&tasklist_lock);
346         switch_uid(INIT_USER);
347 }
348
349 void __set_special_pids(struct pid *pid)
350 {
351         struct task_struct *curr = current->group_leader;
352         pid_t nr = pid_nr(pid);
353
354         if (task_session(curr) != pid) {
355                 change_pid(curr, PIDTYPE_SID, pid);
356                 set_task_session(curr, nr);
357         }
358         if (task_pgrp(curr) != pid) {
359                 change_pid(curr, PIDTYPE_PGID, pid);
360                 set_task_pgrp(curr, nr);
361         }
362 }
363
364 static void set_special_pids(struct pid *pid)
365 {
366         write_lock_irq(&tasklist_lock);
367         __set_special_pids(pid);
368         write_unlock_irq(&tasklist_lock);
369 }
370
371 /*
372  * Let kernel threads use this to say that they
373  * allow a certain signal (since daemonize() will
374  * have disabled all of them by default).
375  */
376 int allow_signal(int sig)
377 {
378         if (!valid_signal(sig) || sig < 1)
379                 return -EINVAL;
380
381         spin_lock_irq(&current->sighand->siglock);
382         sigdelset(&current->blocked, sig);
383         if (!current->mm) {
384                 /* Kernel threads handle their own signals.
385                    Let the signal code know it'll be handled, so
386                    that they don't get converted to SIGKILL or
387                    just silently dropped */
388                 current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2;
389         }
390         recalc_sigpending();
391         spin_unlock_irq(&current->sighand->siglock);
392         return 0;
393 }
394
395 EXPORT_SYMBOL(allow_signal);
396
397 int disallow_signal(int sig)
398 {
399         if (!valid_signal(sig) || sig < 1)
400                 return -EINVAL;
401
402         spin_lock_irq(&current->sighand->siglock);
403         current->sighand->action[(sig)-1].sa.sa_handler = SIG_IGN;
404         recalc_sigpending();
405         spin_unlock_irq(&current->sighand->siglock);
406         return 0;
407 }
408
409 EXPORT_SYMBOL(disallow_signal);
410
411 /*
412  *      Put all the gunge required to become a kernel thread without
413  *      attached user resources in one place where it belongs.
414  */
415
416 void daemonize(const char *name, ...)
417 {
418         va_list args;
419         struct fs_struct *fs;
420         sigset_t blocked;
421
422         va_start(args, name);
423         vsnprintf(current->comm, sizeof(current->comm), name, args);
424         va_end(args);
425
426         /*
427          * If we were started as result of loading a module, close all of the
428          * user space pages.  We don't need them, and if we didn't close them
429          * they would be locked into memory.
430          */
431         exit_mm(current);
432         /*
433          * We don't want to have TIF_FREEZE set if the system-wide hibernation
434          * or suspend transition begins right now.
435          */
436         current->flags |= (PF_NOFREEZE | PF_KTHREAD);
437
438         if (current->nsproxy != &init_nsproxy) {
439                 get_nsproxy(&init_nsproxy);
440                 switch_task_namespaces(current, &init_nsproxy);
441         }
442         set_special_pids(&init_struct_pid);
443         proc_clear_tty(current);
444
445         /* Block and flush all signals */
446         sigfillset(&blocked);
447         sigprocmask(SIG_BLOCK, &blocked, NULL);
448         flush_signals(current);
449
450         /* Become as one with the init task */
451
452         exit_fs(current);       /* current->fs->count--; */
453         fs = init_task.fs;
454         current->fs = fs;
455         atomic_inc(&fs->count);
456
457         exit_files(current);
458         current->files = init_task.files;
459         atomic_inc(&current->files->count);
460
461         reparent_to_kthreadd();
462 }
463
464 EXPORT_SYMBOL(daemonize);
465
466 static void close_files(struct files_struct * files)
467 {
468         int i, j;
469         struct fdtable *fdt;
470
471         j = 0;
472
473         /*
474          * It is safe to dereference the fd table without RCU or
475          * ->file_lock because this is the last reference to the
476          * files structure.
477          */
478         fdt = files_fdtable(files);
479         for (;;) {
480                 unsigned long set;
481                 i = j * __NFDBITS;
482                 if (i >= fdt->max_fds)
483                         break;
484                 set = fdt->open_fds->fds_bits[j++];
485                 while (set) {
486                         if (set & 1) {
487                                 struct file * file = xchg(&fdt->fd[i], NULL);
488                                 if (file) {
489                                         filp_close(file, files);
490                                         cond_resched();
491                                 }
492                         }
493                         i++;
494                         set >>= 1;
495                 }
496         }
497 }
498
499 struct files_struct *get_files_struct(struct task_struct *task)
500 {
501         struct files_struct *files;
502
503         task_lock(task);
504         files = task->files;
505         if (files)
506                 atomic_inc(&files->count);
507         task_unlock(task);
508
509         return files;
510 }
511
512 void put_files_struct(struct files_struct *files)
513 {
514         struct fdtable *fdt;
515
516         if (atomic_dec_and_test(&files->count)) {
517                 close_files(files);
518                 /*
519                  * Free the fd and fdset arrays if we expanded them.
520                  * If the fdtable was embedded, pass files for freeing
521                  * at the end of the RCU grace period. Otherwise,
522                  * you can free files immediately.
523                  */
524                 fdt = files_fdtable(files);
525                 if (fdt != &files->fdtab)
526                         kmem_cache_free(files_cachep, files);
527                 free_fdtable(fdt);
528         }
529 }
530
531 void reset_files_struct(struct files_struct *files)
532 {
533         struct task_struct *tsk = current;
534         struct files_struct *old;
535
536         old = tsk->files;
537         task_lock(tsk);
538         tsk->files = files;
539         task_unlock(tsk);
540         put_files_struct(old);
541 }
542
543 void exit_files(struct task_struct *tsk)
544 {
545         struct files_struct * files = tsk->files;
546
547         if (files) {
548                 task_lock(tsk);
549                 tsk->files = NULL;
550                 task_unlock(tsk);
551                 put_files_struct(files);
552         }
553 }
554
555 void put_fs_struct(struct fs_struct *fs)
556 {
557         /* No need to hold fs->lock if we are killing it */
558         if (atomic_dec_and_test(&fs->count)) {
559                 path_put(&fs->root);
560                 path_put(&fs->pwd);
561                 kmem_cache_free(fs_cachep, fs);
562         }
563 }
564
565 void exit_fs(struct task_struct *tsk)
566 {
567         struct fs_struct * fs = tsk->fs;
568
569         if (fs) {
570                 task_lock(tsk);
571                 tsk->fs = NULL;
572                 task_unlock(tsk);
573                 put_fs_struct(fs);
574         }
575 }
576
577 EXPORT_SYMBOL_GPL(exit_fs);
578
579 #ifdef CONFIG_MM_OWNER
580 /*
581  * Task p is exiting and it owned mm, lets find a new owner for it
582  */
583 static inline int
584 mm_need_new_owner(struct mm_struct *mm, struct task_struct *p)
585 {
586         /*
587          * If there are other users of the mm and the owner (us) is exiting
588          * we need to find a new owner to take on the responsibility.
589          */
590         if (atomic_read(&mm->mm_users) <= 1)
591                 return 0;
592         if (mm->owner != p)
593                 return 0;
594         return 1;
595 }
596
597 void mm_update_next_owner(struct mm_struct *mm)
598 {
599         struct task_struct *c, *g, *p = current;
600
601 retry:
602         if (!mm_need_new_owner(mm, p))
603                 return;
604
605         read_lock(&tasklist_lock);
606         /*
607          * Search in the children
608          */
609         list_for_each_entry(c, &p->children, sibling) {
610                 if (c->mm == mm)
611                         goto assign_new_owner;
612         }
613
614         /*
615          * Search in the siblings
616          */
617         list_for_each_entry(c, &p->parent->children, sibling) {
618                 if (c->mm == mm)
619                         goto assign_new_owner;
620         }
621
622         /*
623          * Search through everything else. We should not get
624          * here often
625          */
626         do_each_thread(g, c) {
627                 if (c->mm == mm)
628                         goto assign_new_owner;
629         } while_each_thread(g, c);
630
631         read_unlock(&tasklist_lock);
632         /*
633          * We found no owner yet mm_users > 1: this implies that we are
634          * most likely racing with swapoff (try_to_unuse()) or /proc or
635          * ptrace or page migration (get_task_mm()).  Mark owner as NULL,
636          * so that subsystems can understand the callback and take action.
637          */
638         down_write(&mm->mmap_sem);
639         cgroup_mm_owner_callbacks(mm->owner, NULL);
640         mm->owner = NULL;
641         up_write(&mm->mmap_sem);
642         return;
643
644 assign_new_owner:
645         BUG_ON(c == p);
646         get_task_struct(c);
647         read_unlock(&tasklist_lock);
648         down_write(&mm->mmap_sem);
649         /*
650          * The task_lock protects c->mm from changing.
651          * We always want mm->owner->mm == mm
652          */
653         task_lock(c);
654         if (c->mm != mm) {
655                 task_unlock(c);
656                 up_write(&mm->mmap_sem);
657                 put_task_struct(c);
658                 goto retry;
659         }
660         cgroup_mm_owner_callbacks(mm->owner, c);
661         mm->owner = c;
662         task_unlock(c);
663         up_write(&mm->mmap_sem);
664         put_task_struct(c);
665 }
666 #endif /* CONFIG_MM_OWNER */
667
668 /*
669  * Turn us into a lazy TLB process if we
670  * aren't already..
671  */
672 static void exit_mm(struct task_struct * tsk)
673 {
674         struct mm_struct *mm = tsk->mm;
675         struct core_state *core_state;
676
677         mm_release(tsk, mm);
678         if (!mm)
679                 return;
680         /*
681          * Serialize with any possible pending coredump.
682          * We must hold mmap_sem around checking core_state
683          * and clearing tsk->mm.  The core-inducing thread
684          * will increment ->nr_threads for each thread in the
685          * group with ->mm != NULL.
686          */
687         down_read(&mm->mmap_sem);
688         core_state = mm->core_state;
689         if (core_state) {
690                 struct core_thread self;
691                 up_read(&mm->mmap_sem);
692
693                 self.task = tsk;
694                 self.next = xchg(&core_state->dumper.next, &self);
695                 /*
696                  * Implies mb(), the result of xchg() must be visible
697                  * to core_state->dumper.
698                  */
699                 if (atomic_dec_and_test(&core_state->nr_threads))
700                         complete(&core_state->startup);
701
702                 for (;;) {
703                         set_task_state(tsk, TASK_UNINTERRUPTIBLE);
704                         if (!self.task) /* see coredump_finish() */
705                                 break;
706                         schedule();
707                 }
708                 __set_task_state(tsk, TASK_RUNNING);
709                 down_read(&mm->mmap_sem);
710         }
711         atomic_inc(&mm->mm_count);
712         BUG_ON(mm != tsk->active_mm);
713         /* more a memory barrier than a real lock */
714         task_lock(tsk);
715         tsk->mm = NULL;
716         up_read(&mm->mmap_sem);
717         enter_lazy_tlb(mm, current);
718         /* We don't want this task to be frozen prematurely */
719         clear_freeze_flag(tsk);
720         task_unlock(tsk);
721         mm_update_next_owner(mm);
722         mmput(mm);
723 }
724
725 /*
726  * Return nonzero if @parent's children should reap themselves.
727  *
728  * Called with write_lock_irq(&tasklist_lock) held.
729  */
730 static int ignoring_children(struct task_struct *parent)
731 {
732         int ret;
733         struct sighand_struct *psig = parent->sighand;
734         unsigned long flags;
735         spin_lock_irqsave(&psig->siglock, flags);
736         ret = (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN ||
737                (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT));
738         spin_unlock_irqrestore(&psig->siglock, flags);
739         return ret;
740 }
741
742 /*
743  * Detach all tasks we were using ptrace on.
744  * Any that need to be release_task'd are put on the @dead list.
745  *
746  * Called with write_lock(&tasklist_lock) held.
747  */
748 static void ptrace_exit(struct task_struct *parent, struct list_head *dead)
749 {
750         struct task_struct *p, *n;
751         int ign = -1;
752
753         list_for_each_entry_safe(p, n, &parent->ptraced, ptrace_entry) {
754                 __ptrace_unlink(p);
755
756                 if (p->exit_state != EXIT_ZOMBIE)
757                         continue;
758
759                 /*
760                  * If it's a zombie, our attachedness prevented normal
761                  * parent notification or self-reaping.  Do notification
762                  * now if it would have happened earlier.  If it should
763                  * reap itself, add it to the @dead list.  We can't call
764                  * release_task() here because we already hold tasklist_lock.
765                  *
766                  * If it's our own child, there is no notification to do.
767                  * But if our normal children self-reap, then this child
768                  * was prevented by ptrace and we must reap it now.
769                  */
770                 if (!task_detached(p) && thread_group_empty(p)) {
771                         if (!same_thread_group(p->real_parent, parent))
772                                 do_notify_parent(p, p->exit_signal);
773                         else {
774                                 if (ign < 0)
775                                         ign = ignoring_children(parent);
776                                 if (ign)
777                                         p->exit_signal = -1;
778                         }
779                 }
780
781                 if (task_detached(p)) {
782                         /*
783                          * Mark it as in the process of being reaped.
784                          */
785                         p->exit_state = EXIT_DEAD;
786                         list_add(&p->ptrace_entry, dead);
787                 }
788         }
789 }
790
791 /*
792  * Finish up exit-time ptrace cleanup.
793  *
794  * Called without locks.
795  */
796 static void ptrace_exit_finish(struct task_struct *parent,
797                                struct list_head *dead)
798 {
799         struct task_struct *p, *n;
800
801         BUG_ON(!list_empty(&parent->ptraced));
802
803         list_for_each_entry_safe(p, n, dead, ptrace_entry) {
804                 list_del_init(&p->ptrace_entry);
805                 release_task(p);
806         }
807 }
808
809 static void reparent_thread(struct task_struct *p, struct task_struct *father)
810 {
811         if (p->pdeath_signal)
812                 /* We already hold the tasklist_lock here.  */
813                 group_send_sig_info(p->pdeath_signal, SEND_SIG_NOINFO, p);
814
815         list_move_tail(&p->sibling, &p->real_parent->children);
816
817         /* If this is a threaded reparent there is no need to
818          * notify anyone anything has happened.
819          */
820         if (same_thread_group(p->real_parent, father))
821                 return;
822
823         /* We don't want people slaying init.  */
824         if (!task_detached(p))
825                 p->exit_signal = SIGCHLD;
826
827         /* If we'd notified the old parent about this child's death,
828          * also notify the new parent.
829          */
830         if (!ptrace_reparented(p) &&
831             p->exit_state == EXIT_ZOMBIE &&
832             !task_detached(p) && thread_group_empty(p))
833                 do_notify_parent(p, p->exit_signal);
834
835         kill_orphaned_pgrp(p, father);
836 }
837
838 /*
839  * When we die, we re-parent all our children.
840  * Try to give them to another thread in our thread
841  * group, and if no such member exists, give it to
842  * the child reaper process (ie "init") in our pid
843  * space.
844  */
845 static struct task_struct *find_new_reaper(struct task_struct *father)
846 {
847         struct pid_namespace *pid_ns = task_active_pid_ns(father);
848         struct task_struct *thread;
849
850         thread = father;
851         while_each_thread(father, thread) {
852                 if (thread->flags & PF_EXITING)
853                         continue;
854                 if (unlikely(pid_ns->child_reaper == father))
855                         pid_ns->child_reaper = thread;
856                 return thread;
857         }
858
859         if (unlikely(pid_ns->child_reaper == father)) {
860                 write_unlock_irq(&tasklist_lock);
861                 if (unlikely(pid_ns == &init_pid_ns))
862                         panic("Attempted to kill init!");
863
864                 zap_pid_ns_processes(pid_ns);
865                 write_lock_irq(&tasklist_lock);
866                 /*
867                  * We can not clear ->child_reaper or leave it alone.
868                  * There may by stealth EXIT_DEAD tasks on ->children,
869                  * forget_original_parent() must move them somewhere.
870                  */
871                 pid_ns->child_reaper = init_pid_ns.child_reaper;
872         }
873
874         return pid_ns->child_reaper;
875 }
876
877 static void forget_original_parent(struct task_struct *father)
878 {
879         struct task_struct *p, *n, *reaper;
880         LIST_HEAD(ptrace_dead);
881
882         write_lock_irq(&tasklist_lock);
883         reaper = find_new_reaper(father);
884         /*
885          * First clean up ptrace if we were using it.
886          */
887         ptrace_exit(father, &ptrace_dead);
888
889         list_for_each_entry_safe(p, n, &father->children, sibling) {
890                 p->real_parent = reaper;
891                 if (p->parent == father) {
892                         BUG_ON(p->ptrace);
893                         p->parent = p->real_parent;
894                 }
895                 reparent_thread(p, father);
896         }
897
898         write_unlock_irq(&tasklist_lock);
899         BUG_ON(!list_empty(&father->children));
900
901         ptrace_exit_finish(father, &ptrace_dead);
902 }
903
904 /*
905  * Send signals to all our closest relatives so that they know
906  * to properly mourn us..
907  */
908 static void exit_notify(struct task_struct *tsk, int group_dead)
909 {
910         int signal;
911         void *cookie;
912
913         /*
914          * This does two things:
915          *
916          * A.  Make init inherit all the child processes
917          * B.  Check to see if any process groups have become orphaned
918          *      as a result of our exiting, and if they have any stopped
919          *      jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
920          */
921         forget_original_parent(tsk);
922         exit_task_namespaces(tsk);
923
924         write_lock_irq(&tasklist_lock);
925         if (group_dead)
926                 kill_orphaned_pgrp(tsk->group_leader, NULL);
927
928         /* Let father know we died
929          *
930          * Thread signals are configurable, but you aren't going to use
931          * that to send signals to arbitary processes.
932          * That stops right now.
933          *
934          * If the parent exec id doesn't match the exec id we saved
935          * when we started then we know the parent has changed security
936          * domain.
937          *
938          * If our self_exec id doesn't match our parent_exec_id then
939          * we have changed execution domain as these two values started
940          * the same after a fork.
941          */
942         if (tsk->exit_signal != SIGCHLD && !task_detached(tsk) &&
943             (tsk->parent_exec_id != tsk->real_parent->self_exec_id ||
944              tsk->self_exec_id != tsk->parent_exec_id) &&
945             !capable(CAP_KILL))
946                 tsk->exit_signal = SIGCHLD;
947
948         signal = tracehook_notify_death(tsk, &cookie, group_dead);
949         if (signal >= 0)
950                 signal = do_notify_parent(tsk, signal);
951
952         tsk->exit_state = signal == DEATH_REAP ? EXIT_DEAD : EXIT_ZOMBIE;
953
954         /* mt-exec, de_thread() is waiting for us */
955         if (thread_group_leader(tsk) &&
956             tsk->signal->group_exit_task &&
957             tsk->signal->notify_count < 0)
958                 wake_up_process(tsk->signal->group_exit_task);
959
960         write_unlock_irq(&tasklist_lock);
961
962         tracehook_report_death(tsk, signal, cookie, group_dead);
963
964         /* If the process is dead, release it - nobody will wait for it */
965         if (signal == DEATH_REAP)
966                 release_task(tsk);
967 }
968
969 #ifdef CONFIG_DEBUG_STACK_USAGE
970 static void check_stack_usage(void)
971 {
972         static DEFINE_SPINLOCK(low_water_lock);
973         static int lowest_to_date = THREAD_SIZE;
974         unsigned long *n = end_of_stack(current);
975         unsigned long free;
976
977         while (*n == 0)
978                 n++;
979         free = (unsigned long)n - (unsigned long)end_of_stack(current);
980
981         if (free >= lowest_to_date)
982                 return;
983
984         spin_lock(&low_water_lock);
985         if (free < lowest_to_date) {
986                 printk(KERN_WARNING "%s used greatest stack depth: %lu bytes "
987                                 "left\n",
988                                 current->comm, free);
989                 lowest_to_date = free;
990         }
991         spin_unlock(&low_water_lock);
992 }
993 #else
994 static inline void check_stack_usage(void) {}
995 #endif
996
997 NORET_TYPE void do_exit(long code)
998 {
999         struct task_struct *tsk = current;
1000         int group_dead;
1001
1002         profile_task_exit(tsk);
1003
1004         WARN_ON(atomic_read(&tsk->fs_excl));
1005
1006         if (unlikely(in_interrupt()))
1007                 panic("Aiee, killing interrupt handler!");
1008         if (unlikely(!tsk->pid))
1009                 panic("Attempted to kill the idle task!");
1010
1011         tracehook_report_exit(&code);
1012
1013         /*
1014          * We're taking recursive faults here in do_exit. Safest is to just
1015          * leave this task alone and wait for reboot.
1016          */
1017         if (unlikely(tsk->flags & PF_EXITING)) {
1018                 printk(KERN_ALERT
1019                         "Fixing recursive fault but reboot is needed!\n");
1020                 /*
1021                  * We can do this unlocked here. The futex code uses
1022                  * this flag just to verify whether the pi state
1023                  * cleanup has been done or not. In the worst case it
1024                  * loops once more. We pretend that the cleanup was
1025                  * done as there is no way to return. Either the
1026                  * OWNER_DIED bit is set by now or we push the blocked
1027                  * task into the wait for ever nirwana as well.
1028                  */
1029                 tsk->flags |= PF_EXITPIDONE;
1030                 if (tsk->io_context)
1031                         exit_io_context();
1032                 set_current_state(TASK_UNINTERRUPTIBLE);
1033                 schedule();
1034         }
1035
1036         exit_signals(tsk);  /* sets PF_EXITING */
1037         /*
1038          * tsk->flags are checked in the futex code to protect against
1039          * an exiting task cleaning up the robust pi futexes.
1040          */
1041         smp_mb();
1042         spin_unlock_wait(&tsk->pi_lock);
1043
1044         if (unlikely(in_atomic()))
1045                 printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
1046                                 current->comm, task_pid_nr(current),
1047                                 preempt_count());
1048
1049         acct_update_integrals(tsk);
1050         if (tsk->mm) {
1051                 update_hiwater_rss(tsk->mm);
1052                 update_hiwater_vm(tsk->mm);
1053         }
1054         group_dead = atomic_dec_and_test(&tsk->signal->live);
1055         if (group_dead) {
1056                 hrtimer_cancel(&tsk->signal->real_timer);
1057                 exit_itimers(tsk->signal);
1058         }
1059         acct_collect(code, group_dead);
1060 #ifdef CONFIG_FUTEX
1061         if (unlikely(tsk->robust_list))
1062                 exit_robust_list(tsk);
1063 #ifdef CONFIG_COMPAT
1064         if (unlikely(tsk->compat_robust_list))
1065                 compat_exit_robust_list(tsk);
1066 #endif
1067 #endif
1068         if (group_dead)
1069                 tty_audit_exit();
1070         if (unlikely(tsk->audit_context))
1071                 audit_free(tsk);
1072
1073         tsk->exit_code = code;
1074         taskstats_exit(tsk, group_dead);
1075
1076         exit_mm(tsk);
1077
1078         if (group_dead)
1079                 acct_process();
1080         trace_sched_process_exit(tsk);
1081
1082         exit_sem(tsk);
1083         exit_files(tsk);
1084         exit_fs(tsk);
1085         check_stack_usage();
1086         exit_thread();
1087         cgroup_exit(tsk, 1);
1088         exit_keys(tsk);
1089
1090         if (group_dead && tsk->signal->leader)
1091                 disassociate_ctty(1);
1092
1093         module_put(task_thread_info(tsk)->exec_domain->module);
1094         if (tsk->binfmt)
1095                 module_put(tsk->binfmt->module);
1096
1097         proc_exit_connector(tsk);
1098         exit_notify(tsk, group_dead);
1099 #ifdef CONFIG_NUMA
1100         mpol_put(tsk->mempolicy);
1101         tsk->mempolicy = NULL;
1102 #endif
1103 #ifdef CONFIG_FUTEX
1104         /*
1105          * This must happen late, after the PID is not
1106          * hashed anymore:
1107          */
1108         if (unlikely(!list_empty(&tsk->pi_state_list)))
1109                 exit_pi_state_list(tsk);
1110         if (unlikely(current->pi_state_cache))
1111                 kfree(current->pi_state_cache);
1112 #endif
1113         /*
1114          * Make sure we are holding no locks:
1115          */
1116         debug_check_no_locks_held(tsk);
1117         /*
1118          * We can do this unlocked here. The futex code uses this flag
1119          * just to verify whether the pi state cleanup has been done
1120          * or not. In the worst case it loops once more.
1121          */
1122         tsk->flags |= PF_EXITPIDONE;
1123
1124         if (tsk->io_context)
1125                 exit_io_context();
1126
1127         if (tsk->splice_pipe)
1128                 __free_pipe_info(tsk->splice_pipe);
1129
1130         preempt_disable();
1131         /* causes final put_task_struct in finish_task_switch(). */
1132         tsk->state = TASK_DEAD;
1133
1134         schedule();
1135         BUG();
1136         /* Avoid "noreturn function does return".  */
1137         for (;;)
1138                 cpu_relax();    /* For when BUG is null */
1139 }
1140
1141 EXPORT_SYMBOL_GPL(do_exit);
1142
1143 NORET_TYPE void complete_and_exit(struct completion *comp, long code)
1144 {
1145         if (comp)
1146                 complete(comp);
1147
1148         do_exit(code);
1149 }
1150
1151 EXPORT_SYMBOL(complete_and_exit);
1152
1153 asmlinkage long sys_exit(int error_code)
1154 {
1155         do_exit((error_code&0xff)<<8);
1156 }
1157
1158 /*
1159  * Take down every thread in the group.  This is called by fatal signals
1160  * as well as by sys_exit_group (below).
1161  */
1162 NORET_TYPE void
1163 do_group_exit(int exit_code)
1164 {
1165         struct signal_struct *sig = current->signal;
1166
1167         BUG_ON(exit_code & 0x80); /* core dumps don't get here */
1168
1169         if (signal_group_exit(sig))
1170                 exit_code = sig->group_exit_code;
1171         else if (!thread_group_empty(current)) {
1172                 struct sighand_struct *const sighand = current->sighand;
1173                 spin_lock_irq(&sighand->siglock);
1174                 if (signal_group_exit(sig))
1175                         /* Another thread got here before we took the lock.  */
1176                         exit_code = sig->group_exit_code;
1177                 else {
1178                         sig->group_exit_code = exit_code;
1179                         sig->flags = SIGNAL_GROUP_EXIT;
1180                         zap_other_threads(current);
1181                 }
1182                 spin_unlock_irq(&sighand->siglock);
1183         }
1184
1185         do_exit(exit_code);
1186         /* NOTREACHED */
1187 }
1188
1189 /*
1190  * this kills every thread in the thread group. Note that any externally
1191  * wait4()-ing process will get the correct exit code - even if this
1192  * thread is not the thread group leader.
1193  */
1194 asmlinkage void sys_exit_group(int error_code)
1195 {
1196         do_group_exit((error_code & 0xff) << 8);
1197 }
1198
1199 static struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
1200 {
1201         struct pid *pid = NULL;
1202         if (type == PIDTYPE_PID)
1203                 pid = task->pids[type].pid;
1204         else if (type < PIDTYPE_MAX)
1205                 pid = task->group_leader->pids[type].pid;
1206         return pid;
1207 }
1208
1209 static int eligible_child(enum pid_type type, struct pid *pid, int options,
1210                           struct task_struct *p)
1211 {
1212         int err;
1213
1214         if (type < PIDTYPE_MAX) {
1215                 if (task_pid_type(p, type) != pid)
1216                         return 0;
1217         }
1218
1219         /* Wait for all children (clone and not) if __WALL is set;
1220          * otherwise, wait for clone children *only* if __WCLONE is
1221          * set; otherwise, wait for non-clone children *only*.  (Note:
1222          * A "clone" child here is one that reports to its parent
1223          * using a signal other than SIGCHLD.) */
1224         if (((p->exit_signal != SIGCHLD) ^ ((options & __WCLONE) != 0))
1225             && !(options & __WALL))
1226                 return 0;
1227
1228         err = security_task_wait(p);
1229         if (err)
1230                 return err;
1231
1232         return 1;
1233 }
1234
1235 static int wait_noreap_copyout(struct task_struct *p, pid_t pid, uid_t uid,
1236                                int why, int status,
1237                                struct siginfo __user *infop,
1238                                struct rusage __user *rusagep)
1239 {
1240         int retval = rusagep ? getrusage(p, RUSAGE_BOTH, rusagep) : 0;
1241
1242         put_task_struct(p);
1243         if (!retval)
1244                 retval = put_user(SIGCHLD, &infop->si_signo);
1245         if (!retval)
1246                 retval = put_user(0, &infop->si_errno);
1247         if (!retval)
1248                 retval = put_user((short)why, &infop->si_code);
1249         if (!retval)
1250                 retval = put_user(pid, &infop->si_pid);
1251         if (!retval)
1252                 retval = put_user(uid, &infop->si_uid);
1253         if (!retval)
1254                 retval = put_user(status, &infop->si_status);
1255         if (!retval)
1256                 retval = pid;
1257         return retval;
1258 }
1259
1260 /*
1261  * Handle sys_wait4 work for one task in state EXIT_ZOMBIE.  We hold
1262  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1263  * the lock and this task is uninteresting.  If we return nonzero, we have
1264  * released the lock and the system call should return.
1265  */
1266 static int wait_task_zombie(struct task_struct *p, int options,
1267                             struct siginfo __user *infop,
1268                             int __user *stat_addr, struct rusage __user *ru)
1269 {
1270         unsigned long state;
1271         int retval, status, traced;
1272         pid_t pid = task_pid_vnr(p);
1273         uid_t uid = __task_cred(p)->uid;
1274
1275         if (!likely(options & WEXITED))
1276                 return 0;
1277
1278         if (unlikely(options & WNOWAIT)) {
1279                 int exit_code = p->exit_code;
1280                 int why, status;
1281
1282                 get_task_struct(p);
1283                 read_unlock(&tasklist_lock);
1284                 if ((exit_code & 0x7f) == 0) {
1285                         why = CLD_EXITED;
1286                         status = exit_code >> 8;
1287                 } else {
1288                         why = (exit_code & 0x80) ? CLD_DUMPED : CLD_KILLED;
1289                         status = exit_code & 0x7f;
1290                 }
1291                 return wait_noreap_copyout(p, pid, uid, why,
1292                                            status, infop, ru);
1293         }
1294
1295         /*
1296          * Try to move the task's state to DEAD
1297          * only one thread is allowed to do this:
1298          */
1299         state = xchg(&p->exit_state, EXIT_DEAD);
1300         if (state != EXIT_ZOMBIE) {
1301                 BUG_ON(state != EXIT_DEAD);
1302                 return 0;
1303         }
1304
1305         traced = ptrace_reparented(p);
1306
1307         if (likely(!traced)) {
1308                 struct signal_struct *psig;
1309                 struct signal_struct *sig;
1310                 struct task_cputime cputime;
1311
1312                 /*
1313                  * The resource counters for the group leader are in its
1314                  * own task_struct.  Those for dead threads in the group
1315                  * are in its signal_struct, as are those for the child
1316                  * processes it has previously reaped.  All these
1317                  * accumulate in the parent's signal_struct c* fields.
1318                  *
1319                  * We don't bother to take a lock here to protect these
1320                  * p->signal fields, because they are only touched by
1321                  * __exit_signal, which runs with tasklist_lock
1322                  * write-locked anyway, and so is excluded here.  We do
1323                  * need to protect the access to p->parent->signal fields,
1324                  * as other threads in the parent group can be right
1325                  * here reaping other children at the same time.
1326                  *
1327                  * We use thread_group_cputime() to get times for the thread
1328                  * group, which consolidates times for all threads in the
1329                  * group including the group leader.
1330                  */
1331                 spin_lock_irq(&p->parent->sighand->siglock);
1332                 psig = p->parent->signal;
1333                 sig = p->signal;
1334                 thread_group_cputime(p, &cputime);
1335                 psig->cutime =
1336                         cputime_add(psig->cutime,
1337                         cputime_add(cputime.utime,
1338                                     sig->cutime));
1339                 psig->cstime =
1340                         cputime_add(psig->cstime,
1341                         cputime_add(cputime.stime,
1342                                     sig->cstime));
1343                 psig->cgtime =
1344                         cputime_add(psig->cgtime,
1345                         cputime_add(p->gtime,
1346                         cputime_add(sig->gtime,
1347                                     sig->cgtime)));
1348                 psig->cmin_flt +=
1349                         p->min_flt + sig->min_flt + sig->cmin_flt;
1350                 psig->cmaj_flt +=
1351                         p->maj_flt + sig->maj_flt + sig->cmaj_flt;
1352                 psig->cnvcsw +=
1353                         p->nvcsw + sig->nvcsw + sig->cnvcsw;
1354                 psig->cnivcsw +=
1355                         p->nivcsw + sig->nivcsw + sig->cnivcsw;
1356                 psig->cinblock +=
1357                         task_io_get_inblock(p) +
1358                         sig->inblock + sig->cinblock;
1359                 psig->coublock +=
1360                         task_io_get_oublock(p) +
1361                         sig->oublock + sig->coublock;
1362                 task_io_accounting_add(&psig->ioac, &p->ioac);
1363                 task_io_accounting_add(&psig->ioac, &sig->ioac);
1364                 spin_unlock_irq(&p->parent->sighand->siglock);
1365         }
1366
1367         /*
1368          * Now we are sure this task is interesting, and no other
1369          * thread can reap it because we set its state to EXIT_DEAD.
1370          */
1371         read_unlock(&tasklist_lock);
1372
1373         retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
1374         status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1375                 ? p->signal->group_exit_code : p->exit_code;
1376         if (!retval && stat_addr)
1377                 retval = put_user(status, stat_addr);
1378         if (!retval && infop)
1379                 retval = put_user(SIGCHLD, &infop->si_signo);
1380         if (!retval && infop)
1381                 retval = put_user(0, &infop->si_errno);
1382         if (!retval && infop) {
1383                 int why;
1384
1385                 if ((status & 0x7f) == 0) {
1386                         why = CLD_EXITED;
1387                         status >>= 8;
1388                 } else {
1389                         why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
1390                         status &= 0x7f;
1391                 }
1392                 retval = put_user((short)why, &infop->si_code);
1393                 if (!retval)
1394                         retval = put_user(status, &infop->si_status);
1395         }
1396         if (!retval && infop)
1397                 retval = put_user(pid, &infop->si_pid);
1398         if (!retval && infop)
1399                 retval = put_user(uid, &infop->si_uid);
1400         if (!retval)
1401                 retval = pid;
1402
1403         if (traced) {
1404                 write_lock_irq(&tasklist_lock);
1405                 /* We dropped tasklist, ptracer could die and untrace */
1406                 ptrace_unlink(p);
1407                 /*
1408                  * If this is not a detached task, notify the parent.
1409                  * If it's still not detached after that, don't release
1410                  * it now.
1411                  */
1412                 if (!task_detached(p)) {
1413                         do_notify_parent(p, p->exit_signal);
1414                         if (!task_detached(p)) {
1415                                 p->exit_state = EXIT_ZOMBIE;
1416                                 p = NULL;
1417                         }
1418                 }
1419                 write_unlock_irq(&tasklist_lock);
1420         }
1421         if (p != NULL)
1422                 release_task(p);
1423
1424         return retval;
1425 }
1426
1427 /*
1428  * Handle sys_wait4 work for one task in state TASK_STOPPED.  We hold
1429  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1430  * the lock and this task is uninteresting.  If we return nonzero, we have
1431  * released the lock and the system call should return.
1432  */
1433 static int wait_task_stopped(int ptrace, struct task_struct *p,
1434                              int options, struct siginfo __user *infop,
1435                              int __user *stat_addr, struct rusage __user *ru)
1436 {
1437         int retval, exit_code, why;
1438         uid_t uid = 0; /* unneeded, required by compiler */
1439         pid_t pid;
1440
1441         if (!(options & WUNTRACED))
1442                 return 0;
1443
1444         exit_code = 0;
1445         spin_lock_irq(&p->sighand->siglock);
1446
1447         if (unlikely(!task_is_stopped_or_traced(p)))
1448                 goto unlock_sig;
1449
1450         if (!ptrace && p->signal->group_stop_count > 0)
1451                 /*
1452                  * A group stop is in progress and this is the group leader.
1453                  * We won't report until all threads have stopped.
1454                  */
1455                 goto unlock_sig;
1456
1457         exit_code = p->exit_code;
1458         if (!exit_code)
1459                 goto unlock_sig;
1460
1461         if (!unlikely(options & WNOWAIT))
1462                 p->exit_code = 0;
1463
1464         /* don't need the RCU readlock here as we're holding a spinlock */
1465         uid = __task_cred(p)->uid;
1466 unlock_sig:
1467         spin_unlock_irq(&p->sighand->siglock);
1468         if (!exit_code)
1469                 return 0;
1470
1471         /*
1472          * Now we are pretty sure this task is interesting.
1473          * Make sure it doesn't get reaped out from under us while we
1474          * give up the lock and then examine it below.  We don't want to
1475          * keep holding onto the tasklist_lock while we call getrusage and
1476          * possibly take page faults for user memory.
1477          */
1478         get_task_struct(p);
1479         pid = task_pid_vnr(p);
1480         why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
1481         read_unlock(&tasklist_lock);
1482
1483         if (unlikely(options & WNOWAIT))
1484                 return wait_noreap_copyout(p, pid, uid,
1485                                            why, exit_code,
1486                                            infop, ru);
1487
1488         retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
1489         if (!retval && stat_addr)
1490                 retval = put_user((exit_code << 8) | 0x7f, stat_addr);
1491         if (!retval && infop)
1492                 retval = put_user(SIGCHLD, &infop->si_signo);
1493         if (!retval && infop)
1494                 retval = put_user(0, &infop->si_errno);
1495         if (!retval && infop)
1496                 retval = put_user((short)why, &infop->si_code);
1497         if (!retval && infop)
1498                 retval = put_user(exit_code, &infop->si_status);
1499         if (!retval && infop)
1500                 retval = put_user(pid, &infop->si_pid);
1501         if (!retval && infop)
1502                 retval = put_user(uid, &infop->si_uid);
1503         if (!retval)
1504                 retval = pid;
1505         put_task_struct(p);
1506
1507         BUG_ON(!retval);
1508         return retval;
1509 }
1510
1511 /*
1512  * Handle do_wait work for one task in a live, non-stopped state.
1513  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1514  * the lock and this task is uninteresting.  If we return nonzero, we have
1515  * released the lock and the system call should return.
1516  */
1517 static int wait_task_continued(struct task_struct *p, int options,
1518                                struct siginfo __user *infop,
1519                                int __user *stat_addr, struct rusage __user *ru)
1520 {
1521         int retval;
1522         pid_t pid;
1523         uid_t uid;
1524
1525         if (!unlikely(options & WCONTINUED))
1526                 return 0;
1527
1528         if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
1529                 return 0;
1530
1531         spin_lock_irq(&p->sighand->siglock);
1532         /* Re-check with the lock held.  */
1533         if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
1534                 spin_unlock_irq(&p->sighand->siglock);
1535                 return 0;
1536         }
1537         if (!unlikely(options & WNOWAIT))
1538                 p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1539         uid = __task_cred(p)->uid;
1540         spin_unlock_irq(&p->sighand->siglock);
1541
1542         pid = task_pid_vnr(p);
1543         get_task_struct(p);
1544         read_unlock(&tasklist_lock);
1545
1546         if (!infop) {
1547                 retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
1548                 put_task_struct(p);
1549                 if (!retval && stat_addr)
1550                         retval = put_user(0xffff, stat_addr);
1551                 if (!retval)
1552                         retval = pid;
1553         } else {
1554                 retval = wait_noreap_copyout(p, pid, uid,
1555                                              CLD_CONTINUED, SIGCONT,
1556                                              infop, ru);
1557                 BUG_ON(retval == 0);
1558         }
1559
1560         return retval;
1561 }
1562
1563 /*
1564  * Consider @p for a wait by @parent.
1565  *
1566  * -ECHILD should be in *@notask_error before the first call.
1567  * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1568  * Returns zero if the search for a child should continue;
1569  * then *@notask_error is 0 if @p is an eligible child,
1570  * or another error from security_task_wait(), or still -ECHILD.
1571  */
1572 static int wait_consider_task(struct task_struct *parent, int ptrace,
1573                               struct task_struct *p, int *notask_error,
1574                               enum pid_type type, struct pid *pid, int options,
1575                               struct siginfo __user *infop,
1576                               int __user *stat_addr, struct rusage __user *ru)
1577 {
1578         int ret = eligible_child(type, pid, options, p);
1579         if (!ret)
1580                 return ret;
1581
1582         if (unlikely(ret < 0)) {
1583                 /*
1584                  * If we have not yet seen any eligible child,
1585                  * then let this error code replace -ECHILD.
1586                  * A permission error will give the user a clue
1587                  * to look for security policy problems, rather
1588                  * than for mysterious wait bugs.
1589                  */
1590                 if (*notask_error)
1591                         *notask_error = ret;
1592         }
1593
1594         if (likely(!ptrace) && unlikely(p->ptrace)) {
1595                 /*
1596                  * This child is hidden by ptrace.
1597                  * We aren't allowed to see it now, but eventually we will.
1598                  */
1599                 *notask_error = 0;
1600                 return 0;
1601         }
1602
1603         if (p->exit_state == EXIT_DEAD)
1604                 return 0;
1605
1606         /*
1607          * We don't reap group leaders with subthreads.
1608          */
1609         if (p->exit_state == EXIT_ZOMBIE && !delay_group_leader(p))
1610                 return wait_task_zombie(p, options, infop, stat_addr, ru);
1611
1612         /*
1613          * It's stopped or running now, so it might
1614          * later continue, exit, or stop again.
1615          */
1616         *notask_error = 0;
1617
1618         if (task_is_stopped_or_traced(p))
1619                 return wait_task_stopped(ptrace, p, options,
1620                                          infop, stat_addr, ru);
1621
1622         return wait_task_continued(p, options, infop, stat_addr, ru);
1623 }
1624
1625 /*
1626  * Do the work of do_wait() for one thread in the group, @tsk.
1627  *
1628  * -ECHILD should be in *@notask_error before the first call.
1629  * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1630  * Returns zero if the search for a child should continue; then
1631  * *@notask_error is 0 if there were any eligible children,
1632  * or another error from security_task_wait(), or still -ECHILD.
1633  */
1634 static int do_wait_thread(struct task_struct *tsk, int *notask_error,
1635                           enum pid_type type, struct pid *pid, int options,
1636                           struct siginfo __user *infop, int __user *stat_addr,
1637                           struct rusage __user *ru)
1638 {
1639         struct task_struct *p;
1640
1641         list_for_each_entry(p, &tsk->children, sibling) {
1642                 /*
1643                  * Do not consider detached threads.
1644                  */
1645                 if (!task_detached(p)) {
1646                         int ret = wait_consider_task(tsk, 0, p, notask_error,
1647                                                      type, pid, options,
1648                                                      infop, stat_addr, ru);
1649                         if (ret)
1650                                 return ret;
1651                 }
1652         }
1653
1654         return 0;
1655 }
1656
1657 static int ptrace_do_wait(struct task_struct *tsk, int *notask_error,
1658                           enum pid_type type, struct pid *pid, int options,
1659                           struct siginfo __user *infop, int __user *stat_addr,
1660                           struct rusage __user *ru)
1661 {
1662         struct task_struct *p;
1663
1664         /*
1665          * Traditionally we see ptrace'd stopped tasks regardless of options.
1666          */
1667         options |= WUNTRACED;
1668
1669         list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
1670                 int ret = wait_consider_task(tsk, 1, p, notask_error,
1671                                              type, pid, options,
1672                                              infop, stat_addr, ru);
1673                 if (ret)
1674                         return ret;
1675         }
1676
1677         return 0;
1678 }
1679
1680 static long do_wait(enum pid_type type, struct pid *pid, int options,
1681                     struct siginfo __user *infop, int __user *stat_addr,
1682                     struct rusage __user *ru)
1683 {
1684         DECLARE_WAITQUEUE(wait, current);
1685         struct task_struct *tsk;
1686         int retval;
1687
1688         trace_sched_process_wait(pid);
1689
1690         add_wait_queue(&current->signal->wait_chldexit,&wait);
1691 repeat:
1692         /*
1693          * If there is nothing that can match our critiera just get out.
1694          * We will clear @retval to zero if we see any child that might later
1695          * match our criteria, even if we are not able to reap it yet.
1696          */
1697         retval = -ECHILD;
1698         if ((type < PIDTYPE_MAX) && (!pid || hlist_empty(&pid->tasks[type])))
1699                 goto end;
1700
1701         current->state = TASK_INTERRUPTIBLE;
1702         read_lock(&tasklist_lock);
1703         tsk = current;
1704         do {
1705                 int tsk_result = do_wait_thread(tsk, &retval,
1706                                                 type, pid, options,
1707                                                 infop, stat_addr, ru);
1708                 if (!tsk_result)
1709                         tsk_result = ptrace_do_wait(tsk, &retval,
1710                                                     type, pid, options,
1711                                                     infop, stat_addr, ru);
1712                 if (tsk_result) {
1713                         /*
1714                          * tasklist_lock is unlocked and we have a final result.
1715                          */
1716                         retval = tsk_result;
1717                         goto end;
1718                 }
1719
1720                 if (options & __WNOTHREAD)
1721                         break;
1722                 tsk = next_thread(tsk);
1723                 BUG_ON(tsk->signal != current->signal);
1724         } while (tsk != current);
1725         read_unlock(&tasklist_lock);
1726
1727         if (!retval && !(options & WNOHANG)) {
1728                 retval = -ERESTARTSYS;
1729                 if (!signal_pending(current)) {
1730                         schedule();
1731                         goto repeat;
1732                 }
1733         }
1734
1735 end:
1736         current->state = TASK_RUNNING;
1737         remove_wait_queue(&current->signal->wait_chldexit,&wait);
1738         if (infop) {
1739                 if (retval > 0)
1740                         retval = 0;
1741                 else {
1742                         /*
1743                          * For a WNOHANG return, clear out all the fields
1744                          * we would set so the user can easily tell the
1745                          * difference.
1746                          */
1747                         if (!retval)
1748                                 retval = put_user(0, &infop->si_signo);
1749                         if (!retval)
1750                                 retval = put_user(0, &infop->si_errno);
1751                         if (!retval)
1752                                 retval = put_user(0, &infop->si_code);
1753                         if (!retval)
1754                                 retval = put_user(0, &infop->si_pid);
1755                         if (!retval)
1756                                 retval = put_user(0, &infop->si_uid);
1757                         if (!retval)
1758                                 retval = put_user(0, &infop->si_status);
1759                 }
1760         }
1761         return retval;
1762 }
1763
1764 asmlinkage long sys_waitid(int which, pid_t upid,
1765                            struct siginfo __user *infop, int options,
1766                            struct rusage __user *ru)
1767 {
1768         struct pid *pid = NULL;
1769         enum pid_type type;
1770         long ret;
1771
1772         if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED))
1773                 return -EINVAL;
1774         if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
1775                 return -EINVAL;
1776
1777         switch (which) {
1778         case P_ALL:
1779                 type = PIDTYPE_MAX;
1780                 break;
1781         case P_PID:
1782                 type = PIDTYPE_PID;
1783                 if (upid <= 0)
1784                         return -EINVAL;
1785                 break;
1786         case P_PGID:
1787                 type = PIDTYPE_PGID;
1788                 if (upid <= 0)
1789                         return -EINVAL;
1790                 break;
1791         default:
1792                 return -EINVAL;
1793         }
1794
1795         if (type < PIDTYPE_MAX)
1796                 pid = find_get_pid(upid);
1797         ret = do_wait(type, pid, options, infop, NULL, ru);
1798         put_pid(pid);
1799
1800         /* avoid REGPARM breakage on x86: */
1801         asmlinkage_protect(5, ret, which, upid, infop, options, ru);
1802         return ret;
1803 }
1804
1805 asmlinkage long sys_wait4(pid_t upid, int __user *stat_addr,
1806                           int options, struct rusage __user *ru)
1807 {
1808         struct pid *pid = NULL;
1809         enum pid_type type;
1810         long ret;
1811
1812         if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
1813                         __WNOTHREAD|__WCLONE|__WALL))
1814                 return -EINVAL;
1815
1816         if (upid == -1)
1817                 type = PIDTYPE_MAX;
1818         else if (upid < 0) {
1819                 type = PIDTYPE_PGID;
1820                 pid = find_get_pid(-upid);
1821         } else if (upid == 0) {
1822                 type = PIDTYPE_PGID;
1823                 pid = get_pid(task_pgrp(current));
1824         } else /* upid > 0 */ {
1825                 type = PIDTYPE_PID;
1826                 pid = find_get_pid(upid);
1827         }
1828
1829         ret = do_wait(type, pid, options | WEXITED, NULL, stat_addr, ru);
1830         put_pid(pid);
1831
1832         /* avoid REGPARM breakage on x86: */
1833         asmlinkage_protect(4, ret, upid, stat_addr, options, ru);
1834         return ret;
1835 }
1836
1837 #ifdef __ARCH_WANT_SYS_WAITPID
1838
1839 /*
1840  * sys_waitpid() remains for compatibility. waitpid() should be
1841  * implemented by calling sys_wait4() from libc.a.
1842  */
1843 asmlinkage long sys_waitpid(pid_t pid, int __user *stat_addr, int options)
1844 {
1845         return sys_wait4(pid, stat_addr, options, NULL);
1846 }
1847
1848 #endif