ca6a11b730231bd0d6d9ece041e1a2f537223582
[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/key.h>
17 #include <linux/security.h>
18 #include <linux/cpu.h>
19 #include <linux/acct.h>
20 #include <linux/tsacct_kern.h>
21 #include <linux/file.h>
22 #include <linux/binfmts.h>
23 #include <linux/nsproxy.h>
24 #include <linux/pid_namespace.h>
25 #include <linux/ptrace.h>
26 #include <linux/profile.h>
27 #include <linux/signalfd.h>
28 #include <linux/mount.h>
29 #include <linux/proc_fs.h>
30 #include <linux/kthread.h>
31 #include <linux/mempolicy.h>
32 #include <linux/taskstats_kern.h>
33 #include <linux/delayacct.h>
34 #include <linux/cpuset.h>
35 #include <linux/syscalls.h>
36 #include <linux/signal.h>
37 #include <linux/posix-timers.h>
38 #include <linux/cn_proc.h>
39 #include <linux/mutex.h>
40 #include <linux/futex.h>
41 #include <linux/compat.h>
42 #include <linux/pipe_fs_i.h>
43 #include <linux/audit.h> /* for audit_free() */
44 #include <linux/resource.h>
45 #include <linux/blkdev.h>
46 #include <linux/task_io_accounting_ops.h>
47
48 #include <asm/uaccess.h>
49 #include <asm/unistd.h>
50 #include <asm/pgtable.h>
51 #include <asm/mmu_context.h>
52
53 extern void sem_exit (void);
54
55 static void exit_mm(struct task_struct * tsk);
56
57 static void __unhash_process(struct task_struct *p)
58 {
59         nr_threads--;
60         detach_pid(p, PIDTYPE_PID);
61         if (thread_group_leader(p)) {
62                 detach_pid(p, PIDTYPE_PGID);
63                 detach_pid(p, PIDTYPE_SID);
64
65                 list_del_rcu(&p->tasks);
66                 __get_cpu_var(process_counts)--;
67         }
68         list_del_rcu(&p->thread_group);
69         remove_parent(p);
70 }
71
72 /*
73  * This function expects the tasklist_lock write-locked.
74  */
75 static void __exit_signal(struct task_struct *tsk)
76 {
77         struct signal_struct *sig = tsk->signal;
78         struct sighand_struct *sighand;
79
80         BUG_ON(!sig);
81         BUG_ON(!atomic_read(&sig->count));
82
83         rcu_read_lock();
84         sighand = rcu_dereference(tsk->sighand);
85         spin_lock(&sighand->siglock);
86
87         /*
88          * Notify that this sighand has been detached. This must
89          * be called with the tsk->sighand lock held. Also, this
90          * access tsk->sighand internally, so it must be called
91          * before tsk->sighand is reset.
92          */
93         signalfd_detach_locked(tsk);
94
95         posix_cpu_timers_exit(tsk);
96         if (atomic_dec_and_test(&sig->count))
97                 posix_cpu_timers_exit_group(tsk);
98         else {
99                 /*
100                  * If there is any task waiting for the group exit
101                  * then notify it:
102                  */
103                 if (sig->group_exit_task && atomic_read(&sig->count) == sig->notify_count) {
104                         wake_up_process(sig->group_exit_task);
105                         sig->group_exit_task = NULL;
106                 }
107                 if (tsk == sig->curr_target)
108                         sig->curr_target = next_thread(tsk);
109                 /*
110                  * Accumulate here the counters for all threads but the
111                  * group leader as they die, so they can be added into
112                  * the process-wide totals when those are taken.
113                  * The group leader stays around as a zombie as long
114                  * as there are other threads.  When it gets reaped,
115                  * the exit.c code will add its counts into these totals.
116                  * We won't ever get here for the group leader, since it
117                  * will have been the last reference on the signal_struct.
118                  */
119                 sig->utime = cputime_add(sig->utime, tsk->utime);
120                 sig->stime = cputime_add(sig->stime, tsk->stime);
121                 sig->min_flt += tsk->min_flt;
122                 sig->maj_flt += tsk->maj_flt;
123                 sig->nvcsw += tsk->nvcsw;
124                 sig->nivcsw += tsk->nivcsw;
125                 sig->inblock += task_io_get_inblock(tsk);
126                 sig->oublock += task_io_get_oublock(tsk);
127                 sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
128                 sig = NULL; /* Marker for below. */
129         }
130
131         __unhash_process(tsk);
132
133         tsk->signal = NULL;
134         tsk->sighand = NULL;
135         spin_unlock(&sighand->siglock);
136         rcu_read_unlock();
137
138         __cleanup_sighand(sighand);
139         clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
140         flush_sigqueue(&tsk->pending);
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         put_task_struct(container_of(rhp, struct task_struct, rcu));
151 }
152
153 void release_task(struct task_struct * p)
154 {
155         struct task_struct *leader;
156         int zap_leader;
157 repeat:
158         atomic_dec(&p->user->processes);
159         write_lock_irq(&tasklist_lock);
160         ptrace_unlink(p);
161         BUG_ON(!list_empty(&p->ptrace_list) || !list_empty(&p->ptrace_children));
162         __exit_signal(p);
163
164         /*
165          * If we are the last non-leader member of the thread
166          * group, and the leader is zombie, then notify the
167          * group leader's parent process. (if it wants notification.)
168          */
169         zap_leader = 0;
170         leader = p->group_leader;
171         if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
172                 BUG_ON(leader->exit_signal == -1);
173                 do_notify_parent(leader, leader->exit_signal);
174                 /*
175                  * If we were the last child thread and the leader has
176                  * exited already, and the leader's parent ignores SIGCHLD,
177                  * then we are the one who should release the leader.
178                  *
179                  * do_notify_parent() will have marked it self-reaping in
180                  * that case.
181                  */
182                 zap_leader = (leader->exit_signal == -1);
183         }
184
185         write_unlock_irq(&tasklist_lock);
186         proc_flush_task(p);
187         release_thread(p);
188         call_rcu(&p->rcu, delayed_put_task_struct);
189
190         p = leader;
191         if (unlikely(zap_leader))
192                 goto repeat;
193 }
194
195 /*
196  * This checks not only the pgrp, but falls back on the pid if no
197  * satisfactory pgrp is found. I dunno - gdb doesn't work correctly
198  * without this...
199  *
200  * The caller must hold rcu lock or the tasklist lock.
201  */
202 struct pid *session_of_pgrp(struct pid *pgrp)
203 {
204         struct task_struct *p;
205         struct pid *sid = NULL;
206
207         p = pid_task(pgrp, PIDTYPE_PGID);
208         if (p == NULL)
209                 p = pid_task(pgrp, PIDTYPE_PID);
210         if (p != NULL)
211                 sid = task_session(p);
212
213         return sid;
214 }
215
216 /*
217  * Determine if a process group is "orphaned", according to the POSIX
218  * definition in 2.2.2.52.  Orphaned process groups are not to be affected
219  * by terminal-generated stop signals.  Newly orphaned process groups are
220  * to receive a SIGHUP and a SIGCONT.
221  *
222  * "I ask you, have you ever known what it is to be an orphan?"
223  */
224 static int will_become_orphaned_pgrp(struct pid *pgrp, struct task_struct *ignored_task)
225 {
226         struct task_struct *p;
227         int ret = 1;
228
229         do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
230                 if (p == ignored_task
231                                 || p->exit_state
232                                 || is_init(p->real_parent))
233                         continue;
234                 if (task_pgrp(p->real_parent) != pgrp &&
235                     task_session(p->real_parent) == task_session(p)) {
236                         ret = 0;
237                         break;
238                 }
239         } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
240         return ret;     /* (sighing) "Often!" */
241 }
242
243 int is_current_pgrp_orphaned(void)
244 {
245         int retval;
246
247         read_lock(&tasklist_lock);
248         retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
249         read_unlock(&tasklist_lock);
250
251         return retval;
252 }
253
254 static int has_stopped_jobs(struct pid *pgrp)
255 {
256         int retval = 0;
257         struct task_struct *p;
258
259         do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
260                 if (p->state != TASK_STOPPED)
261                         continue;
262                 retval = 1;
263                 break;
264         } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
265         return retval;
266 }
267
268 /**
269  * reparent_to_kthreadd - Reparent the calling kernel thread to kthreadd
270  *
271  * If a kernel thread is launched as a result of a system call, or if
272  * it ever exits, it should generally reparent itself to kthreadd so it
273  * isn't in the way of other processes and is correctly cleaned up on exit.
274  *
275  * The various task state such as scheduling policy and priority may have
276  * been inherited from a user process, so we reset them to sane values here.
277  *
278  * NOTE that reparent_to_kthreadd() gives the caller full capabilities.
279  */
280 static void reparent_to_kthreadd(void)
281 {
282         write_lock_irq(&tasklist_lock);
283
284         ptrace_unlink(current);
285         /* Reparent to init */
286         remove_parent(current);
287         current->real_parent = current->parent = kthreadd_task;
288         add_parent(current);
289
290         /* Set the exit signal to SIGCHLD so we signal init on exit */
291         current->exit_signal = SIGCHLD;
292
293         if (task_nice(current) < 0)
294                 set_user_nice(current, 0);
295         /* cpus_allowed? */
296         /* rt_priority? */
297         /* signals? */
298         security_task_reparent_to_init(current);
299         memcpy(current->signal->rlim, init_task.signal->rlim,
300                sizeof(current->signal->rlim));
301         atomic_inc(&(INIT_USER->__count));
302         write_unlock_irq(&tasklist_lock);
303         switch_uid(INIT_USER);
304 }
305
306 void __set_special_pids(pid_t session, pid_t pgrp)
307 {
308         struct task_struct *curr = current->group_leader;
309
310         if (process_session(curr) != session) {
311                 detach_pid(curr, PIDTYPE_SID);
312                 set_signal_session(curr->signal, session);
313                 attach_pid(curr, PIDTYPE_SID, find_pid(session));
314         }
315         if (process_group(curr) != pgrp) {
316                 detach_pid(curr, PIDTYPE_PGID);
317                 curr->signal->pgrp = pgrp;
318                 attach_pid(curr, PIDTYPE_PGID, find_pid(pgrp));
319         }
320 }
321
322 static void set_special_pids(pid_t session, pid_t pgrp)
323 {
324         write_lock_irq(&tasklist_lock);
325         __set_special_pids(session, pgrp);
326         write_unlock_irq(&tasklist_lock);
327 }
328
329 /*
330  * Let kernel threads use this to say that they
331  * allow a certain signal (since daemonize() will
332  * have disabled all of them by default).
333  */
334 int allow_signal(int sig)
335 {
336         if (!valid_signal(sig) || sig < 1)
337                 return -EINVAL;
338
339         spin_lock_irq(&current->sighand->siglock);
340         sigdelset(&current->blocked, sig);
341         if (!current->mm) {
342                 /* Kernel threads handle their own signals.
343                    Let the signal code know it'll be handled, so
344                    that they don't get converted to SIGKILL or
345                    just silently dropped */
346                 current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2;
347         }
348         recalc_sigpending();
349         spin_unlock_irq(&current->sighand->siglock);
350         return 0;
351 }
352
353 EXPORT_SYMBOL(allow_signal);
354
355 int disallow_signal(int sig)
356 {
357         if (!valid_signal(sig) || sig < 1)
358                 return -EINVAL;
359
360         spin_lock_irq(&current->sighand->siglock);
361         current->sighand->action[(sig)-1].sa.sa_handler = SIG_IGN;
362         recalc_sigpending();
363         spin_unlock_irq(&current->sighand->siglock);
364         return 0;
365 }
366
367 EXPORT_SYMBOL(disallow_signal);
368
369 /*
370  *      Put all the gunge required to become a kernel thread without
371  *      attached user resources in one place where it belongs.
372  */
373
374 void daemonize(const char *name, ...)
375 {
376         va_list args;
377         struct fs_struct *fs;
378         sigset_t blocked;
379
380         va_start(args, name);
381         vsnprintf(current->comm, sizeof(current->comm), name, args);
382         va_end(args);
383
384         /*
385          * If we were started as result of loading a module, close all of the
386          * user space pages.  We don't need them, and if we didn't close them
387          * they would be locked into memory.
388          */
389         exit_mm(current);
390
391         set_special_pids(1, 1);
392         proc_clear_tty(current);
393
394         /* Block and flush all signals */
395         sigfillset(&blocked);
396         sigprocmask(SIG_BLOCK, &blocked, NULL);
397         flush_signals(current);
398
399         /* Become as one with the init task */
400
401         exit_fs(current);       /* current->fs->count--; */
402         fs = init_task.fs;
403         current->fs = fs;
404         atomic_inc(&fs->count);
405
406         exit_task_namespaces(current);
407         current->nsproxy = init_task.nsproxy;
408         get_task_namespaces(current);
409
410         exit_files(current);
411         current->files = init_task.files;
412         atomic_inc(&current->files->count);
413
414         reparent_to_kthreadd();
415 }
416
417 EXPORT_SYMBOL(daemonize);
418
419 static void close_files(struct files_struct * files)
420 {
421         int i, j;
422         struct fdtable *fdt;
423
424         j = 0;
425
426         /*
427          * It is safe to dereference the fd table without RCU or
428          * ->file_lock because this is the last reference to the
429          * files structure.
430          */
431         fdt = files_fdtable(files);
432         for (;;) {
433                 unsigned long set;
434                 i = j * __NFDBITS;
435                 if (i >= fdt->max_fds)
436                         break;
437                 set = fdt->open_fds->fds_bits[j++];
438                 while (set) {
439                         if (set & 1) {
440                                 struct file * file = xchg(&fdt->fd[i], NULL);
441                                 if (file) {
442                                         filp_close(file, files);
443                                         cond_resched();
444                                 }
445                         }
446                         i++;
447                         set >>= 1;
448                 }
449         }
450 }
451
452 struct files_struct *get_files_struct(struct task_struct *task)
453 {
454         struct files_struct *files;
455
456         task_lock(task);
457         files = task->files;
458         if (files)
459                 atomic_inc(&files->count);
460         task_unlock(task);
461
462         return files;
463 }
464
465 void fastcall put_files_struct(struct files_struct *files)
466 {
467         struct fdtable *fdt;
468
469         if (atomic_dec_and_test(&files->count)) {
470                 close_files(files);
471                 /*
472                  * Free the fd and fdset arrays if we expanded them.
473                  * If the fdtable was embedded, pass files for freeing
474                  * at the end of the RCU grace period. Otherwise,
475                  * you can free files immediately.
476                  */
477                 fdt = files_fdtable(files);
478                 if (fdt != &files->fdtab)
479                         kmem_cache_free(files_cachep, files);
480                 free_fdtable(fdt);
481         }
482 }
483
484 EXPORT_SYMBOL(put_files_struct);
485
486 void reset_files_struct(struct task_struct *tsk, struct files_struct *files)
487 {
488         struct files_struct *old;
489
490         old = tsk->files;
491         task_lock(tsk);
492         tsk->files = files;
493         task_unlock(tsk);
494         put_files_struct(old);
495 }
496 EXPORT_SYMBOL(reset_files_struct);
497
498 static inline void __exit_files(struct task_struct *tsk)
499 {
500         struct files_struct * files = tsk->files;
501
502         if (files) {
503                 task_lock(tsk);
504                 tsk->files = NULL;
505                 task_unlock(tsk);
506                 put_files_struct(files);
507         }
508 }
509
510 void exit_files(struct task_struct *tsk)
511 {
512         __exit_files(tsk);
513 }
514
515 static inline void __put_fs_struct(struct fs_struct *fs)
516 {
517         /* No need to hold fs->lock if we are killing it */
518         if (atomic_dec_and_test(&fs->count)) {
519                 dput(fs->root);
520                 mntput(fs->rootmnt);
521                 dput(fs->pwd);
522                 mntput(fs->pwdmnt);
523                 if (fs->altroot) {
524                         dput(fs->altroot);
525                         mntput(fs->altrootmnt);
526                 }
527                 kmem_cache_free(fs_cachep, fs);
528         }
529 }
530
531 void put_fs_struct(struct fs_struct *fs)
532 {
533         __put_fs_struct(fs);
534 }
535
536 static inline void __exit_fs(struct task_struct *tsk)
537 {
538         struct fs_struct * fs = tsk->fs;
539
540         if (fs) {
541                 task_lock(tsk);
542                 tsk->fs = NULL;
543                 task_unlock(tsk);
544                 __put_fs_struct(fs);
545         }
546 }
547
548 void exit_fs(struct task_struct *tsk)
549 {
550         __exit_fs(tsk);
551 }
552
553 EXPORT_SYMBOL_GPL(exit_fs);
554
555 /*
556  * Turn us into a lazy TLB process if we
557  * aren't already..
558  */
559 static void exit_mm(struct task_struct * tsk)
560 {
561         struct mm_struct *mm = tsk->mm;
562
563         mm_release(tsk, mm);
564         if (!mm)
565                 return;
566         /*
567          * Serialize with any possible pending coredump.
568          * We must hold mmap_sem around checking core_waiters
569          * and clearing tsk->mm.  The core-inducing thread
570          * will increment core_waiters for each thread in the
571          * group with ->mm != NULL.
572          */
573         down_read(&mm->mmap_sem);
574         if (mm->core_waiters) {
575                 up_read(&mm->mmap_sem);
576                 down_write(&mm->mmap_sem);
577                 if (!--mm->core_waiters)
578                         complete(mm->core_startup_done);
579                 up_write(&mm->mmap_sem);
580
581                 wait_for_completion(&mm->core_done);
582                 down_read(&mm->mmap_sem);
583         }
584         atomic_inc(&mm->mm_count);
585         BUG_ON(mm != tsk->active_mm);
586         /* more a memory barrier than a real lock */
587         task_lock(tsk);
588         tsk->mm = NULL;
589         up_read(&mm->mmap_sem);
590         enter_lazy_tlb(mm, current);
591         task_unlock(tsk);
592         mmput(mm);
593 }
594
595 static inline void
596 choose_new_parent(struct task_struct *p, struct task_struct *reaper)
597 {
598         /*
599          * Make sure we're not reparenting to ourselves and that
600          * the parent is not a zombie.
601          */
602         BUG_ON(p == reaper || reaper->exit_state);
603         p->real_parent = reaper;
604 }
605
606 static void
607 reparent_thread(struct task_struct *p, struct task_struct *father, int traced)
608 {
609         if (p->pdeath_signal)
610                 /* We already hold the tasklist_lock here.  */
611                 group_send_sig_info(p->pdeath_signal, SEND_SIG_NOINFO, p);
612
613         /* Move the child from its dying parent to the new one.  */
614         if (unlikely(traced)) {
615                 /* Preserve ptrace links if someone else is tracing this child.  */
616                 list_del_init(&p->ptrace_list);
617                 if (p->parent != p->real_parent)
618                         list_add(&p->ptrace_list, &p->real_parent->ptrace_children);
619         } else {
620                 /* If this child is being traced, then we're the one tracing it
621                  * anyway, so let go of it.
622                  */
623                 p->ptrace = 0;
624                 remove_parent(p);
625                 p->parent = p->real_parent;
626                 add_parent(p);
627
628                 if (p->state == TASK_TRACED) {
629                         /*
630                          * If it was at a trace stop, turn it into
631                          * a normal stop since it's no longer being
632                          * traced.
633                          */
634                         ptrace_untrace(p);
635                 }
636         }
637
638         /* If this is a threaded reparent there is no need to
639          * notify anyone anything has happened.
640          */
641         if (p->real_parent->group_leader == father->group_leader)
642                 return;
643
644         /* We don't want people slaying init.  */
645         if (p->exit_signal != -1)
646                 p->exit_signal = SIGCHLD;
647
648         /* If we'd notified the old parent about this child's death,
649          * also notify the new parent.
650          */
651         if (!traced && p->exit_state == EXIT_ZOMBIE &&
652             p->exit_signal != -1 && thread_group_empty(p))
653                 do_notify_parent(p, p->exit_signal);
654
655         /*
656          * process group orphan check
657          * Case ii: Our child is in a different pgrp
658          * than we are, and it was the only connection
659          * outside, so the child pgrp is now orphaned.
660          */
661         if ((task_pgrp(p) != task_pgrp(father)) &&
662             (task_session(p) == task_session(father))) {
663                 struct pid *pgrp = task_pgrp(p);
664
665                 if (will_become_orphaned_pgrp(pgrp, NULL) &&
666                     has_stopped_jobs(pgrp)) {
667                         __kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
668                         __kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
669                 }
670         }
671 }
672
673 /*
674  * When we die, we re-parent all our children.
675  * Try to give them to another thread in our thread
676  * group, and if no such member exists, give it to
677  * the child reaper process (ie "init") in our pid
678  * space.
679  */
680 static void
681 forget_original_parent(struct task_struct *father, struct list_head *to_release)
682 {
683         struct task_struct *p, *reaper = father;
684         struct list_head *_p, *_n;
685
686         do {
687                 reaper = next_thread(reaper);
688                 if (reaper == father) {
689                         reaper = child_reaper(father);
690                         break;
691                 }
692         } while (reaper->exit_state);
693
694         /*
695          * There are only two places where our children can be:
696          *
697          * - in our child list
698          * - in our ptraced child list
699          *
700          * Search them and reparent children.
701          */
702         list_for_each_safe(_p, _n, &father->children) {
703                 int ptrace;
704                 p = list_entry(_p, struct task_struct, sibling);
705
706                 ptrace = p->ptrace;
707
708                 /* if father isn't the real parent, then ptrace must be enabled */
709                 BUG_ON(father != p->real_parent && !ptrace);
710
711                 if (father == p->real_parent) {
712                         /* reparent with a reaper, real father it's us */
713                         choose_new_parent(p, reaper);
714                         reparent_thread(p, father, 0);
715                 } else {
716                         /* reparent ptraced task to its real parent */
717                         __ptrace_unlink (p);
718                         if (p->exit_state == EXIT_ZOMBIE && p->exit_signal != -1 &&
719                             thread_group_empty(p))
720                                 do_notify_parent(p, p->exit_signal);
721                 }
722
723                 /*
724                  * if the ptraced child is a zombie with exit_signal == -1
725                  * we must collect it before we exit, or it will remain
726                  * zombie forever since we prevented it from self-reap itself
727                  * while it was being traced by us, to be able to see it in wait4.
728                  */
729                 if (unlikely(ptrace && p->exit_state == EXIT_ZOMBIE && p->exit_signal == -1))
730                         list_add(&p->ptrace_list, to_release);
731         }
732         list_for_each_safe(_p, _n, &father->ptrace_children) {
733                 p = list_entry(_p, struct task_struct, ptrace_list);
734                 choose_new_parent(p, reaper);
735                 reparent_thread(p, father, 1);
736         }
737 }
738
739 /*
740  * Send signals to all our closest relatives so that they know
741  * to properly mourn us..
742  */
743 static void exit_notify(struct task_struct *tsk)
744 {
745         int state;
746         struct task_struct *t;
747         struct list_head ptrace_dead, *_p, *_n;
748         struct pid *pgrp;
749
750         if (signal_pending(tsk) && !(tsk->signal->flags & SIGNAL_GROUP_EXIT)
751             && !thread_group_empty(tsk)) {
752                 /*
753                  * This occurs when there was a race between our exit
754                  * syscall and a group signal choosing us as the one to
755                  * wake up.  It could be that we are the only thread
756                  * alerted to check for pending signals, but another thread
757                  * should be woken now to take the signal since we will not.
758                  * Now we'll wake all the threads in the group just to make
759                  * sure someone gets all the pending signals.
760                  */
761                 read_lock(&tasklist_lock);
762                 spin_lock_irq(&tsk->sighand->siglock);
763                 for (t = next_thread(tsk); t != tsk; t = next_thread(t))
764                         if (!signal_pending(t) && !(t->flags & PF_EXITING))
765                                 recalc_sigpending_and_wake(t);
766                 spin_unlock_irq(&tsk->sighand->siglock);
767                 read_unlock(&tasklist_lock);
768         }
769
770         write_lock_irq(&tasklist_lock);
771
772         /*
773          * This does two things:
774          *
775          * A.  Make init inherit all the child processes
776          * B.  Check to see if any process groups have become orphaned
777          *      as a result of our exiting, and if they have any stopped
778          *      jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
779          */
780
781         INIT_LIST_HEAD(&ptrace_dead);
782         forget_original_parent(tsk, &ptrace_dead);
783         BUG_ON(!list_empty(&tsk->children));
784         BUG_ON(!list_empty(&tsk->ptrace_children));
785
786         /*
787          * Check to see if any process groups have become orphaned
788          * as a result of our exiting, and if they have any stopped
789          * jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
790          *
791          * Case i: Our father is in a different pgrp than we are
792          * and we were the only connection outside, so our pgrp
793          * is about to become orphaned.
794          */
795          
796         t = tsk->real_parent;
797         
798         pgrp = task_pgrp(tsk);
799         if ((task_pgrp(t) != pgrp) &&
800             (task_session(t) == task_session(tsk)) &&
801             will_become_orphaned_pgrp(pgrp, tsk) &&
802             has_stopped_jobs(pgrp)) {
803                 __kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
804                 __kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
805         }
806
807         /* Let father know we died 
808          *
809          * Thread signals are configurable, but you aren't going to use
810          * that to send signals to arbitary processes. 
811          * That stops right now.
812          *
813          * If the parent exec id doesn't match the exec id we saved
814          * when we started then we know the parent has changed security
815          * domain.
816          *
817          * If our self_exec id doesn't match our parent_exec_id then
818          * we have changed execution domain as these two values started
819          * the same after a fork.
820          *      
821          */
822         
823         if (tsk->exit_signal != SIGCHLD && tsk->exit_signal != -1 &&
824             ( tsk->parent_exec_id != t->self_exec_id  ||
825               tsk->self_exec_id != tsk->parent_exec_id)
826             && !capable(CAP_KILL))
827                 tsk->exit_signal = SIGCHLD;
828
829
830         /* If something other than our normal parent is ptracing us, then
831          * send it a SIGCHLD instead of honoring exit_signal.  exit_signal
832          * only has special meaning to our real parent.
833          */
834         if (tsk->exit_signal != -1 && thread_group_empty(tsk)) {
835                 int signal = tsk->parent == tsk->real_parent ? tsk->exit_signal : SIGCHLD;
836                 do_notify_parent(tsk, signal);
837         } else if (tsk->ptrace) {
838                 do_notify_parent(tsk, SIGCHLD);
839         }
840
841         state = EXIT_ZOMBIE;
842         if (tsk->exit_signal == -1 &&
843             (likely(tsk->ptrace == 0) ||
844              unlikely(tsk->parent->signal->flags & SIGNAL_GROUP_EXIT)))
845                 state = EXIT_DEAD;
846         tsk->exit_state = state;
847
848         write_unlock_irq(&tasklist_lock);
849
850         list_for_each_safe(_p, _n, &ptrace_dead) {
851                 list_del_init(_p);
852                 t = list_entry(_p, struct task_struct, ptrace_list);
853                 release_task(t);
854         }
855
856         /* If the process is dead, release it - nobody will wait for it */
857         if (state == EXIT_DEAD)
858                 release_task(tsk);
859 }
860
861 fastcall NORET_TYPE void do_exit(long code)
862 {
863         struct task_struct *tsk = current;
864         int group_dead;
865
866         profile_task_exit(tsk);
867
868         WARN_ON(atomic_read(&tsk->fs_excl));
869
870         if (unlikely(in_interrupt()))
871                 panic("Aiee, killing interrupt handler!");
872         if (unlikely(!tsk->pid))
873                 panic("Attempted to kill the idle task!");
874         if (unlikely(tsk == child_reaper(tsk))) {
875                 if (tsk->nsproxy->pid_ns != &init_pid_ns)
876                         tsk->nsproxy->pid_ns->child_reaper = init_pid_ns.child_reaper;
877                 else
878                         panic("Attempted to kill init!");
879         }
880
881
882         if (unlikely(current->ptrace & PT_TRACE_EXIT)) {
883                 current->ptrace_message = code;
884                 ptrace_notify((PTRACE_EVENT_EXIT << 8) | SIGTRAP);
885         }
886
887         /*
888          * We're taking recursive faults here in do_exit. Safest is to just
889          * leave this task alone and wait for reboot.
890          */
891         if (unlikely(tsk->flags & PF_EXITING)) {
892                 printk(KERN_ALERT
893                         "Fixing recursive fault but reboot is needed!\n");
894                 /*
895                  * We can do this unlocked here. The futex code uses
896                  * this flag just to verify whether the pi state
897                  * cleanup has been done or not. In the worst case it
898                  * loops once more. We pretend that the cleanup was
899                  * done as there is no way to return. Either the
900                  * OWNER_DIED bit is set by now or we push the blocked
901                  * task into the wait for ever nirwana as well.
902                  */
903                 tsk->flags |= PF_EXITPIDONE;
904                 if (tsk->io_context)
905                         exit_io_context();
906                 set_current_state(TASK_UNINTERRUPTIBLE);
907                 schedule();
908         }
909
910         /*
911          * tsk->flags are checked in the futex code to protect against
912          * an exiting task cleaning up the robust pi futexes.
913          */
914         spin_lock_irq(&tsk->pi_lock);
915         tsk->flags |= PF_EXITING;
916         spin_unlock_irq(&tsk->pi_lock);
917
918         if (unlikely(in_atomic()))
919                 printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
920                                 current->comm, current->pid,
921                                 preempt_count());
922
923         acct_update_integrals(tsk);
924         if (tsk->mm) {
925                 update_hiwater_rss(tsk->mm);
926                 update_hiwater_vm(tsk->mm);
927         }
928         group_dead = atomic_dec_and_test(&tsk->signal->live);
929         if (group_dead) {
930                 hrtimer_cancel(&tsk->signal->real_timer);
931                 exit_itimers(tsk->signal);
932         }
933         acct_collect(code, group_dead);
934         if (unlikely(tsk->robust_list))
935                 exit_robust_list(tsk);
936 #if defined(CONFIG_FUTEX) && defined(CONFIG_COMPAT)
937         if (unlikely(tsk->compat_robust_list))
938                 compat_exit_robust_list(tsk);
939 #endif
940         if (unlikely(tsk->audit_context))
941                 audit_free(tsk);
942
943         taskstats_exit(tsk, group_dead);
944
945         exit_mm(tsk);
946
947         if (group_dead)
948                 acct_process();
949         exit_sem(tsk);
950         __exit_files(tsk);
951         __exit_fs(tsk);
952         exit_thread();
953         cpuset_exit(tsk);
954         exit_keys(tsk);
955
956         if (group_dead && tsk->signal->leader)
957                 disassociate_ctty(1);
958
959         module_put(task_thread_info(tsk)->exec_domain->module);
960         if (tsk->binfmt)
961                 module_put(tsk->binfmt->module);
962
963         tsk->exit_code = code;
964         proc_exit_connector(tsk);
965         exit_task_namespaces(tsk);
966         exit_notify(tsk);
967 #ifdef CONFIG_NUMA
968         mpol_free(tsk->mempolicy);
969         tsk->mempolicy = NULL;
970 #endif
971         /*
972          * This must happen late, after the PID is not
973          * hashed anymore:
974          */
975         if (unlikely(!list_empty(&tsk->pi_state_list)))
976                 exit_pi_state_list(tsk);
977         if (unlikely(current->pi_state_cache))
978                 kfree(current->pi_state_cache);
979         /*
980          * Make sure we are holding no locks:
981          */
982         debug_check_no_locks_held(tsk);
983         /*
984          * We can do this unlocked here. The futex code uses this flag
985          * just to verify whether the pi state cleanup has been done
986          * or not. In the worst case it loops once more.
987          */
988         tsk->flags |= PF_EXITPIDONE;
989
990         if (tsk->io_context)
991                 exit_io_context();
992
993         if (tsk->splice_pipe)
994                 __free_pipe_info(tsk->splice_pipe);
995
996         preempt_disable();
997         /* causes final put_task_struct in finish_task_switch(). */
998         tsk->state = TASK_DEAD;
999
1000         schedule();
1001         BUG();
1002         /* Avoid "noreturn function does return".  */
1003         for (;;)
1004                 cpu_relax();    /* For when BUG is null */
1005 }
1006
1007 EXPORT_SYMBOL_GPL(do_exit);
1008
1009 NORET_TYPE void complete_and_exit(struct completion *comp, long code)
1010 {
1011         if (comp)
1012                 complete(comp);
1013
1014         do_exit(code);
1015 }
1016
1017 EXPORT_SYMBOL(complete_and_exit);
1018
1019 asmlinkage long sys_exit(int error_code)
1020 {
1021         do_exit((error_code&0xff)<<8);
1022 }
1023
1024 /*
1025  * Take down every thread in the group.  This is called by fatal signals
1026  * as well as by sys_exit_group (below).
1027  */
1028 NORET_TYPE void
1029 do_group_exit(int exit_code)
1030 {
1031         BUG_ON(exit_code & 0x80); /* core dumps don't get here */
1032
1033         if (current->signal->flags & SIGNAL_GROUP_EXIT)
1034                 exit_code = current->signal->group_exit_code;
1035         else if (!thread_group_empty(current)) {
1036                 struct signal_struct *const sig = current->signal;
1037                 struct sighand_struct *const sighand = current->sighand;
1038                 spin_lock_irq(&sighand->siglock);
1039                 if (sig->flags & SIGNAL_GROUP_EXIT)
1040                         /* Another thread got here before we took the lock.  */
1041                         exit_code = sig->group_exit_code;
1042                 else {
1043                         sig->group_exit_code = exit_code;
1044                         zap_other_threads(current);
1045                 }
1046                 spin_unlock_irq(&sighand->siglock);
1047         }
1048
1049         do_exit(exit_code);
1050         /* NOTREACHED */
1051 }
1052
1053 /*
1054  * this kills every thread in the thread group. Note that any externally
1055  * wait4()-ing process will get the correct exit code - even if this
1056  * thread is not the thread group leader.
1057  */
1058 asmlinkage void sys_exit_group(int error_code)
1059 {
1060         do_group_exit((error_code & 0xff) << 8);
1061 }
1062
1063 static int eligible_child(pid_t pid, int options, struct task_struct *p)
1064 {
1065         int err;
1066
1067         if (pid > 0) {
1068                 if (p->pid != pid)
1069                         return 0;
1070         } else if (!pid) {
1071                 if (process_group(p) != process_group(current))
1072                         return 0;
1073         } else if (pid != -1) {
1074                 if (process_group(p) != -pid)
1075                         return 0;
1076         }
1077
1078         /*
1079          * Do not consider detached threads that are
1080          * not ptraced:
1081          */
1082         if (p->exit_signal == -1 && !p->ptrace)
1083                 return 0;
1084
1085         /* Wait for all children (clone and not) if __WALL is set;
1086          * otherwise, wait for clone children *only* if __WCLONE is
1087          * set; otherwise, wait for non-clone children *only*.  (Note:
1088          * A "clone" child here is one that reports to its parent
1089          * using a signal other than SIGCHLD.) */
1090         if (((p->exit_signal != SIGCHLD) ^ ((options & __WCLONE) != 0))
1091             && !(options & __WALL))
1092                 return 0;
1093         /*
1094          * Do not consider thread group leaders that are
1095          * in a non-empty thread group:
1096          */
1097         if (delay_group_leader(p))
1098                 return 2;
1099
1100         err = security_task_wait(p);
1101         if (err)
1102                 return err;
1103
1104         return 1;
1105 }
1106
1107 static int wait_noreap_copyout(struct task_struct *p, pid_t pid, uid_t uid,
1108                                int why, int status,
1109                                struct siginfo __user *infop,
1110                                struct rusage __user *rusagep)
1111 {
1112         int retval = rusagep ? getrusage(p, RUSAGE_BOTH, rusagep) : 0;
1113
1114         put_task_struct(p);
1115         if (!retval)
1116                 retval = put_user(SIGCHLD, &infop->si_signo);
1117         if (!retval)
1118                 retval = put_user(0, &infop->si_errno);
1119         if (!retval)
1120                 retval = put_user((short)why, &infop->si_code);
1121         if (!retval)
1122                 retval = put_user(pid, &infop->si_pid);
1123         if (!retval)
1124                 retval = put_user(uid, &infop->si_uid);
1125         if (!retval)
1126                 retval = put_user(status, &infop->si_status);
1127         if (!retval)
1128                 retval = pid;
1129         return retval;
1130 }
1131
1132 /*
1133  * Handle sys_wait4 work for one task in state EXIT_ZOMBIE.  We hold
1134  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1135  * the lock and this task is uninteresting.  If we return nonzero, we have
1136  * released the lock and the system call should return.
1137  */
1138 static int wait_task_zombie(struct task_struct *p, int noreap,
1139                             struct siginfo __user *infop,
1140                             int __user *stat_addr, struct rusage __user *ru)
1141 {
1142         unsigned long state;
1143         int retval;
1144         int status;
1145
1146         if (unlikely(noreap)) {
1147                 pid_t pid = p->pid;
1148                 uid_t uid = p->uid;
1149                 int exit_code = p->exit_code;
1150                 int why, status;
1151
1152                 if (unlikely(p->exit_state != EXIT_ZOMBIE))
1153                         return 0;
1154                 if (unlikely(p->exit_signal == -1 && p->ptrace == 0))
1155                         return 0;
1156                 get_task_struct(p);
1157                 read_unlock(&tasklist_lock);
1158                 if ((exit_code & 0x7f) == 0) {
1159                         why = CLD_EXITED;
1160                         status = exit_code >> 8;
1161                 } else {
1162                         why = (exit_code & 0x80) ? CLD_DUMPED : CLD_KILLED;
1163                         status = exit_code & 0x7f;
1164                 }
1165                 return wait_noreap_copyout(p, pid, uid, why,
1166                                            status, infop, ru);
1167         }
1168
1169         /*
1170          * Try to move the task's state to DEAD
1171          * only one thread is allowed to do this:
1172          */
1173         state = xchg(&p->exit_state, EXIT_DEAD);
1174         if (state != EXIT_ZOMBIE) {
1175                 BUG_ON(state != EXIT_DEAD);
1176                 return 0;
1177         }
1178         if (unlikely(p->exit_signal == -1 && p->ptrace == 0)) {
1179                 /*
1180                  * This can only happen in a race with a ptraced thread
1181                  * dying on another processor.
1182                  */
1183                 return 0;
1184         }
1185
1186         if (likely(p->real_parent == p->parent) && likely(p->signal)) {
1187                 struct signal_struct *psig;
1188                 struct signal_struct *sig;
1189
1190                 /*
1191                  * The resource counters for the group leader are in its
1192                  * own task_struct.  Those for dead threads in the group
1193                  * are in its signal_struct, as are those for the child
1194                  * processes it has previously reaped.  All these
1195                  * accumulate in the parent's signal_struct c* fields.
1196                  *
1197                  * We don't bother to take a lock here to protect these
1198                  * p->signal fields, because they are only touched by
1199                  * __exit_signal, which runs with tasklist_lock
1200                  * write-locked anyway, and so is excluded here.  We do
1201                  * need to protect the access to p->parent->signal fields,
1202                  * as other threads in the parent group can be right
1203                  * here reaping other children at the same time.
1204                  */
1205                 spin_lock_irq(&p->parent->sighand->siglock);
1206                 psig = p->parent->signal;
1207                 sig = p->signal;
1208                 psig->cutime =
1209                         cputime_add(psig->cutime,
1210                         cputime_add(p->utime,
1211                         cputime_add(sig->utime,
1212                                     sig->cutime)));
1213                 psig->cstime =
1214                         cputime_add(psig->cstime,
1215                         cputime_add(p->stime,
1216                         cputime_add(sig->stime,
1217                                     sig->cstime)));
1218                 psig->cmin_flt +=
1219                         p->min_flt + sig->min_flt + sig->cmin_flt;
1220                 psig->cmaj_flt +=
1221                         p->maj_flt + sig->maj_flt + sig->cmaj_flt;
1222                 psig->cnvcsw +=
1223                         p->nvcsw + sig->nvcsw + sig->cnvcsw;
1224                 psig->cnivcsw +=
1225                         p->nivcsw + sig->nivcsw + sig->cnivcsw;
1226                 psig->cinblock +=
1227                         task_io_get_inblock(p) +
1228                         sig->inblock + sig->cinblock;
1229                 psig->coublock +=
1230                         task_io_get_oublock(p) +
1231                         sig->oublock + sig->coublock;
1232                 spin_unlock_irq(&p->parent->sighand->siglock);
1233         }
1234
1235         /*
1236          * Now we are sure this task is interesting, and no other
1237          * thread can reap it because we set its state to EXIT_DEAD.
1238          */
1239         read_unlock(&tasklist_lock);
1240
1241         retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
1242         status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1243                 ? p->signal->group_exit_code : p->exit_code;
1244         if (!retval && stat_addr)
1245                 retval = put_user(status, stat_addr);
1246         if (!retval && infop)
1247                 retval = put_user(SIGCHLD, &infop->si_signo);
1248         if (!retval && infop)
1249                 retval = put_user(0, &infop->si_errno);
1250         if (!retval && infop) {
1251                 int why;
1252
1253                 if ((status & 0x7f) == 0) {
1254                         why = CLD_EXITED;
1255                         status >>= 8;
1256                 } else {
1257                         why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
1258                         status &= 0x7f;
1259                 }
1260                 retval = put_user((short)why, &infop->si_code);
1261                 if (!retval)
1262                         retval = put_user(status, &infop->si_status);
1263         }
1264         if (!retval && infop)
1265                 retval = put_user(p->pid, &infop->si_pid);
1266         if (!retval && infop)
1267                 retval = put_user(p->uid, &infop->si_uid);
1268         if (retval) {
1269                 // TODO: is this safe?
1270                 p->exit_state = EXIT_ZOMBIE;
1271                 return retval;
1272         }
1273         retval = p->pid;
1274         if (p->real_parent != p->parent) {
1275                 write_lock_irq(&tasklist_lock);
1276                 /* Double-check with lock held.  */
1277                 if (p->real_parent != p->parent) {
1278                         __ptrace_unlink(p);
1279                         // TODO: is this safe?
1280                         p->exit_state = EXIT_ZOMBIE;
1281                         /*
1282                          * If this is not a detached task, notify the parent.
1283                          * If it's still not detached after that, don't release
1284                          * it now.
1285                          */
1286                         if (p->exit_signal != -1) {
1287                                 do_notify_parent(p, p->exit_signal);
1288                                 if (p->exit_signal != -1)
1289                                         p = NULL;
1290                         }
1291                 }
1292                 write_unlock_irq(&tasklist_lock);
1293         }
1294         if (p != NULL)
1295                 release_task(p);
1296         BUG_ON(!retval);
1297         return retval;
1298 }
1299
1300 /*
1301  * Handle sys_wait4 work for one task in state TASK_STOPPED.  We hold
1302  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1303  * the lock and this task is uninteresting.  If we return nonzero, we have
1304  * released the lock and the system call should return.
1305  */
1306 static int wait_task_stopped(struct task_struct *p, int delayed_group_leader,
1307                              int noreap, struct siginfo __user *infop,
1308                              int __user *stat_addr, struct rusage __user *ru)
1309 {
1310         int retval, exit_code;
1311
1312         if (!p->exit_code)
1313                 return 0;
1314         if (delayed_group_leader && !(p->ptrace & PT_PTRACED) &&
1315             p->signal && p->signal->group_stop_count > 0)
1316                 /*
1317                  * A group stop is in progress and this is the group leader.
1318                  * We won't report until all threads have stopped.
1319                  */
1320                 return 0;
1321
1322         /*
1323          * Now we are pretty sure this task is interesting.
1324          * Make sure it doesn't get reaped out from under us while we
1325          * give up the lock and then examine it below.  We don't want to
1326          * keep holding onto the tasklist_lock while we call getrusage and
1327          * possibly take page faults for user memory.
1328          */
1329         get_task_struct(p);
1330         read_unlock(&tasklist_lock);
1331
1332         if (unlikely(noreap)) {
1333                 pid_t pid = p->pid;
1334                 uid_t uid = p->uid;
1335                 int why = (p->ptrace & PT_PTRACED) ? CLD_TRAPPED : CLD_STOPPED;
1336
1337                 exit_code = p->exit_code;
1338                 if (unlikely(!exit_code) ||
1339                     unlikely(p->state & TASK_TRACED))
1340                         goto bail_ref;
1341                 return wait_noreap_copyout(p, pid, uid,
1342                                            why, (exit_code << 8) | 0x7f,
1343                                            infop, ru);
1344         }
1345
1346         write_lock_irq(&tasklist_lock);
1347
1348         /*
1349          * This uses xchg to be atomic with the thread resuming and setting
1350          * it.  It must also be done with the write lock held to prevent a
1351          * race with the EXIT_ZOMBIE case.
1352          */
1353         exit_code = xchg(&p->exit_code, 0);
1354         if (unlikely(p->exit_state)) {
1355                 /*
1356                  * The task resumed and then died.  Let the next iteration
1357                  * catch it in EXIT_ZOMBIE.  Note that exit_code might
1358                  * already be zero here if it resumed and did _exit(0).
1359                  * The task itself is dead and won't touch exit_code again;
1360                  * other processors in this function are locked out.
1361                  */
1362                 p->exit_code = exit_code;
1363                 exit_code = 0;
1364         }
1365         if (unlikely(exit_code == 0)) {
1366                 /*
1367                  * Another thread in this function got to it first, or it
1368                  * resumed, or it resumed and then died.
1369                  */
1370                 write_unlock_irq(&tasklist_lock);
1371 bail_ref:
1372                 put_task_struct(p);
1373                 /*
1374                  * We are returning to the wait loop without having successfully
1375                  * removed the process and having released the lock. We cannot
1376                  * continue, since the "p" task pointer is potentially stale.
1377                  *
1378                  * Return -EAGAIN, and do_wait() will restart the loop from the
1379                  * beginning. Do _not_ re-acquire the lock.
1380                  */
1381                 return -EAGAIN;
1382         }
1383
1384         /* move to end of parent's list to avoid starvation */
1385         remove_parent(p);
1386         add_parent(p);
1387
1388         write_unlock_irq(&tasklist_lock);
1389
1390         retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
1391         if (!retval && stat_addr)
1392                 retval = put_user((exit_code << 8) | 0x7f, stat_addr);
1393         if (!retval && infop)
1394                 retval = put_user(SIGCHLD, &infop->si_signo);
1395         if (!retval && infop)
1396                 retval = put_user(0, &infop->si_errno);
1397         if (!retval && infop)
1398                 retval = put_user((short)((p->ptrace & PT_PTRACED)
1399                                           ? CLD_TRAPPED : CLD_STOPPED),
1400                                   &infop->si_code);
1401         if (!retval && infop)
1402                 retval = put_user(exit_code, &infop->si_status);
1403         if (!retval && infop)
1404                 retval = put_user(p->pid, &infop->si_pid);
1405         if (!retval && infop)
1406                 retval = put_user(p->uid, &infop->si_uid);
1407         if (!retval)
1408                 retval = p->pid;
1409         put_task_struct(p);
1410
1411         BUG_ON(!retval);
1412         return retval;
1413 }
1414
1415 /*
1416  * Handle do_wait work for one task in a live, non-stopped state.
1417  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1418  * the lock and this task is uninteresting.  If we return nonzero, we have
1419  * released the lock and the system call should return.
1420  */
1421 static int wait_task_continued(struct task_struct *p, int noreap,
1422                                struct siginfo __user *infop,
1423                                int __user *stat_addr, struct rusage __user *ru)
1424 {
1425         int retval;
1426         pid_t pid;
1427         uid_t uid;
1428
1429         if (unlikely(!p->signal))
1430                 return 0;
1431
1432         if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
1433                 return 0;
1434
1435         spin_lock_irq(&p->sighand->siglock);
1436         /* Re-check with the lock held.  */
1437         if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
1438                 spin_unlock_irq(&p->sighand->siglock);
1439                 return 0;
1440         }
1441         if (!noreap)
1442                 p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1443         spin_unlock_irq(&p->sighand->siglock);
1444
1445         pid = p->pid;
1446         uid = p->uid;
1447         get_task_struct(p);
1448         read_unlock(&tasklist_lock);
1449
1450         if (!infop) {
1451                 retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
1452                 put_task_struct(p);
1453                 if (!retval && stat_addr)
1454                         retval = put_user(0xffff, stat_addr);
1455                 if (!retval)
1456                         retval = p->pid;
1457         } else {
1458                 retval = wait_noreap_copyout(p, pid, uid,
1459                                              CLD_CONTINUED, SIGCONT,
1460                                              infop, ru);
1461                 BUG_ON(retval == 0);
1462         }
1463
1464         return retval;
1465 }
1466
1467
1468 static inline int my_ptrace_child(struct task_struct *p)
1469 {
1470         if (!(p->ptrace & PT_PTRACED))
1471                 return 0;
1472         if (!(p->ptrace & PT_ATTACHED))
1473                 return 1;
1474         /*
1475          * This child was PTRACE_ATTACH'd.  We should be seeing it only if
1476          * we are the attacher.  If we are the real parent, this is a race
1477          * inside ptrace_attach.  It is waiting for the tasklist_lock,
1478          * which we have to switch the parent links, but has already set
1479          * the flags in p->ptrace.
1480          */
1481         return (p->parent != p->real_parent);
1482 }
1483
1484 static long do_wait(pid_t pid, int options, struct siginfo __user *infop,
1485                     int __user *stat_addr, struct rusage __user *ru)
1486 {
1487         DECLARE_WAITQUEUE(wait, current);
1488         struct task_struct *tsk;
1489         int flag, retval;
1490         int allowed, denied;
1491
1492         add_wait_queue(&current->signal->wait_chldexit,&wait);
1493 repeat:
1494         /*
1495          * We will set this flag if we see any child that might later
1496          * match our criteria, even if we are not able to reap it yet.
1497          */
1498         flag = 0;
1499         allowed = denied = 0;
1500         current->state = TASK_INTERRUPTIBLE;
1501         read_lock(&tasklist_lock);
1502         tsk = current;
1503         do {
1504                 struct task_struct *p;
1505                 struct list_head *_p;
1506                 int ret;
1507
1508                 list_for_each(_p,&tsk->children) {
1509                         p = list_entry(_p, struct task_struct, sibling);
1510
1511                         ret = eligible_child(pid, options, p);
1512                         if (!ret)
1513                                 continue;
1514
1515                         if (unlikely(ret < 0)) {
1516                                 denied = ret;
1517                                 continue;
1518                         }
1519                         allowed = 1;
1520
1521                         switch (p->state) {
1522                         case TASK_TRACED:
1523                                 /*
1524                                  * When we hit the race with PTRACE_ATTACH,
1525                                  * we will not report this child.  But the
1526                                  * race means it has not yet been moved to
1527                                  * our ptrace_children list, so we need to
1528                                  * set the flag here to avoid a spurious ECHILD
1529                                  * when the race happens with the only child.
1530                                  */
1531                                 flag = 1;
1532                                 if (!my_ptrace_child(p))
1533                                         continue;
1534                                 /*FALLTHROUGH*/
1535                         case TASK_STOPPED:
1536                                 /*
1537                                  * It's stopped now, so it might later
1538                                  * continue, exit, or stop again.
1539                                  */
1540                                 flag = 1;
1541                                 if (!(options & WUNTRACED) &&
1542                                     !my_ptrace_child(p))
1543                                         continue;
1544                                 retval = wait_task_stopped(p, ret == 2,
1545                                                            (options & WNOWAIT),
1546                                                            infop,
1547                                                            stat_addr, ru);
1548                                 if (retval == -EAGAIN)
1549                                         goto repeat;
1550                                 if (retval != 0) /* He released the lock.  */
1551                                         goto end;
1552                                 break;
1553                         default:
1554                         // case EXIT_DEAD:
1555                                 if (p->exit_state == EXIT_DEAD)
1556                                         continue;
1557                         // case EXIT_ZOMBIE:
1558                                 if (p->exit_state == EXIT_ZOMBIE) {
1559                                         /*
1560                                          * Eligible but we cannot release
1561                                          * it yet:
1562                                          */
1563                                         if (ret == 2)
1564                                                 goto check_continued;
1565                                         if (!likely(options & WEXITED))
1566                                                 continue;
1567                                         retval = wait_task_zombie(
1568                                                 p, (options & WNOWAIT),
1569                                                 infop, stat_addr, ru);
1570                                         /* He released the lock.  */
1571                                         if (retval != 0)
1572                                                 goto end;
1573                                         break;
1574                                 }
1575 check_continued:
1576                                 /*
1577                                  * It's running now, so it might later
1578                                  * exit, stop, or stop and then continue.
1579                                  */
1580                                 flag = 1;
1581                                 if (!unlikely(options & WCONTINUED))
1582                                         continue;
1583                                 retval = wait_task_continued(
1584                                         p, (options & WNOWAIT),
1585                                         infop, stat_addr, ru);
1586                                 if (retval != 0) /* He released the lock.  */
1587                                         goto end;
1588                                 break;
1589                         }
1590                 }
1591                 if (!flag) {
1592                         list_for_each(_p, &tsk->ptrace_children) {
1593                                 p = list_entry(_p, struct task_struct,
1594                                                 ptrace_list);
1595                                 if (!eligible_child(pid, options, p))
1596                                         continue;
1597                                 flag = 1;
1598                                 break;
1599                         }
1600                 }
1601                 if (options & __WNOTHREAD)
1602                         break;
1603                 tsk = next_thread(tsk);
1604                 BUG_ON(tsk->signal != current->signal);
1605         } while (tsk != current);
1606
1607         read_unlock(&tasklist_lock);
1608         if (flag) {
1609                 retval = 0;
1610                 if (options & WNOHANG)
1611                         goto end;
1612                 retval = -ERESTARTSYS;
1613                 if (signal_pending(current))
1614                         goto end;
1615                 schedule();
1616                 goto repeat;
1617         }
1618         retval = -ECHILD;
1619         if (unlikely(denied) && !allowed)
1620                 retval = denied;
1621 end:
1622         current->state = TASK_RUNNING;
1623         remove_wait_queue(&current->signal->wait_chldexit,&wait);
1624         if (infop) {
1625                 if (retval > 0)
1626                 retval = 0;
1627                 else {
1628                         /*
1629                          * For a WNOHANG return, clear out all the fields
1630                          * we would set so the user can easily tell the
1631                          * difference.
1632                          */
1633                         if (!retval)
1634                                 retval = put_user(0, &infop->si_signo);
1635                         if (!retval)
1636                                 retval = put_user(0, &infop->si_errno);
1637                         if (!retval)
1638                                 retval = put_user(0, &infop->si_code);
1639                         if (!retval)
1640                                 retval = put_user(0, &infop->si_pid);
1641                         if (!retval)
1642                                 retval = put_user(0, &infop->si_uid);
1643                         if (!retval)
1644                                 retval = put_user(0, &infop->si_status);
1645                 }
1646         }
1647         return retval;
1648 }
1649
1650 asmlinkage long sys_waitid(int which, pid_t pid,
1651                            struct siginfo __user *infop, int options,
1652                            struct rusage __user *ru)
1653 {
1654         long ret;
1655
1656         if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED))
1657                 return -EINVAL;
1658         if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
1659                 return -EINVAL;
1660
1661         switch (which) {
1662         case P_ALL:
1663                 pid = -1;
1664                 break;
1665         case P_PID:
1666                 if (pid <= 0)
1667                         return -EINVAL;
1668                 break;
1669         case P_PGID:
1670                 if (pid <= 0)
1671                         return -EINVAL;
1672                 pid = -pid;
1673                 break;
1674         default:
1675                 return -EINVAL;
1676         }
1677
1678         ret = do_wait(pid, options, infop, NULL, ru);
1679
1680         /* avoid REGPARM breakage on x86: */
1681         prevent_tail_call(ret);
1682         return ret;
1683 }
1684
1685 asmlinkage long sys_wait4(pid_t pid, int __user *stat_addr,
1686                           int options, struct rusage __user *ru)
1687 {
1688         long ret;
1689
1690         if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
1691                         __WNOTHREAD|__WCLONE|__WALL))
1692                 return -EINVAL;
1693         ret = do_wait(pid, options | WEXITED, NULL, stat_addr, ru);
1694
1695         /* avoid REGPARM breakage on x86: */
1696         prevent_tail_call(ret);
1697         return ret;
1698 }
1699
1700 #ifdef __ARCH_WANT_SYS_WAITPID
1701
1702 /*
1703  * sys_waitpid() remains for compatibility. waitpid() should be
1704  * implemented by calling sys_wait4() from libc.a.
1705  */
1706 asmlinkage long sys_waitpid(pid_t pid, int __user *stat_addr, int options)
1707 {
1708         return sys_wait4(pid, stat_addr, options, NULL);
1709 }
1710
1711 #endif