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