xref: /openbmc/linux/kernel/exit.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
1 /*
2  *  linux/kernel/exit.c
3  *
4  *  Copyright (C) 1991, 1992  Linus Torvalds
5  */
6 
7 #include <linux/config.h>
8 #include <linux/mm.h>
9 #include <linux/slab.h>
10 #include <linux/interrupt.h>
11 #include <linux/smp_lock.h>
12 #include <linux/module.h>
13 #include <linux/completion.h>
14 #include <linux/personality.h>
15 #include <linux/tty.h>
16 #include <linux/namespace.h>
17 #include <linux/key.h>
18 #include <linux/security.h>
19 #include <linux/cpu.h>
20 #include <linux/acct.h>
21 #include <linux/file.h>
22 #include <linux/binfmts.h>
23 #include <linux/ptrace.h>
24 #include <linux/profile.h>
25 #include <linux/mount.h>
26 #include <linux/proc_fs.h>
27 #include <linux/mempolicy.h>
28 #include <linux/cpuset.h>
29 #include <linux/syscalls.h>
30 #include <linux/signal.h>
31 
32 #include <asm/uaccess.h>
33 #include <asm/unistd.h>
34 #include <asm/pgtable.h>
35 #include <asm/mmu_context.h>
36 
37 extern void sem_exit (void);
38 extern struct task_struct *child_reaper;
39 
40 int getrusage(struct task_struct *, int, struct rusage __user *);
41 
42 static void exit_mm(struct task_struct * tsk);
43 
44 static void __unhash_process(struct task_struct *p)
45 {
46 	nr_threads--;
47 	detach_pid(p, PIDTYPE_PID);
48 	detach_pid(p, PIDTYPE_TGID);
49 	if (thread_group_leader(p)) {
50 		detach_pid(p, PIDTYPE_PGID);
51 		detach_pid(p, PIDTYPE_SID);
52 		if (p->pid)
53 			__get_cpu_var(process_counts)--;
54 	}
55 
56 	REMOVE_LINKS(p);
57 }
58 
59 void release_task(struct task_struct * p)
60 {
61 	int zap_leader;
62 	task_t *leader;
63 	struct dentry *proc_dentry;
64 
65 repeat:
66 	atomic_dec(&p->user->processes);
67 	spin_lock(&p->proc_lock);
68 	proc_dentry = proc_pid_unhash(p);
69 	write_lock_irq(&tasklist_lock);
70 	if (unlikely(p->ptrace))
71 		__ptrace_unlink(p);
72 	BUG_ON(!list_empty(&p->ptrace_list) || !list_empty(&p->ptrace_children));
73 	__exit_signal(p);
74 	__exit_sighand(p);
75 	/*
76 	 * Note that the fastpath in sys_times depends on __exit_signal having
77 	 * updated the counters before a task is removed from the tasklist of
78 	 * the process by __unhash_process.
79 	 */
80 	__unhash_process(p);
81 
82 	/*
83 	 * If we are the last non-leader member of the thread
84 	 * group, and the leader is zombie, then notify the
85 	 * group leader's parent process. (if it wants notification.)
86 	 */
87 	zap_leader = 0;
88 	leader = p->group_leader;
89 	if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
90 		BUG_ON(leader->exit_signal == -1);
91 		do_notify_parent(leader, leader->exit_signal);
92 		/*
93 		 * If we were the last child thread and the leader has
94 		 * exited already, and the leader's parent ignores SIGCHLD,
95 		 * then we are the one who should release the leader.
96 		 *
97 		 * do_notify_parent() will have marked it self-reaping in
98 		 * that case.
99 		 */
100 		zap_leader = (leader->exit_signal == -1);
101 	}
102 
103 	sched_exit(p);
104 	write_unlock_irq(&tasklist_lock);
105 	spin_unlock(&p->proc_lock);
106 	proc_pid_flush(proc_dentry);
107 	release_thread(p);
108 	put_task_struct(p);
109 
110 	p = leader;
111 	if (unlikely(zap_leader))
112 		goto repeat;
113 }
114 
115 /* we are using it only for SMP init */
116 
117 void unhash_process(struct task_struct *p)
118 {
119 	struct dentry *proc_dentry;
120 
121 	spin_lock(&p->proc_lock);
122 	proc_dentry = proc_pid_unhash(p);
123 	write_lock_irq(&tasklist_lock);
124 	__unhash_process(p);
125 	write_unlock_irq(&tasklist_lock);
126 	spin_unlock(&p->proc_lock);
127 	proc_pid_flush(proc_dentry);
128 }
129 
130 /*
131  * This checks not only the pgrp, but falls back on the pid if no
132  * satisfactory pgrp is found. I dunno - gdb doesn't work correctly
133  * without this...
134  */
135 int session_of_pgrp(int pgrp)
136 {
137 	struct task_struct *p;
138 	int sid = -1;
139 
140 	read_lock(&tasklist_lock);
141 	do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
142 		if (p->signal->session > 0) {
143 			sid = p->signal->session;
144 			goto out;
145 		}
146 	} while_each_task_pid(pgrp, PIDTYPE_PGID, p);
147 	p = find_task_by_pid(pgrp);
148 	if (p)
149 		sid = p->signal->session;
150 out:
151 	read_unlock(&tasklist_lock);
152 
153 	return sid;
154 }
155 
156 /*
157  * Determine if a process group is "orphaned", according to the POSIX
158  * definition in 2.2.2.52.  Orphaned process groups are not to be affected
159  * by terminal-generated stop signals.  Newly orphaned process groups are
160  * to receive a SIGHUP and a SIGCONT.
161  *
162  * "I ask you, have you ever known what it is to be an orphan?"
163  */
164 static int will_become_orphaned_pgrp(int pgrp, task_t *ignored_task)
165 {
166 	struct task_struct *p;
167 	int ret = 1;
168 
169 	do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
170 		if (p == ignored_task
171 				|| p->exit_state
172 				|| p->real_parent->pid == 1)
173 			continue;
174 		if (process_group(p->real_parent) != pgrp
175 			    && p->real_parent->signal->session == p->signal->session) {
176 			ret = 0;
177 			break;
178 		}
179 	} while_each_task_pid(pgrp, PIDTYPE_PGID, p);
180 	return ret;	/* (sighing) "Often!" */
181 }
182 
183 int is_orphaned_pgrp(int pgrp)
184 {
185 	int retval;
186 
187 	read_lock(&tasklist_lock);
188 	retval = will_become_orphaned_pgrp(pgrp, NULL);
189 	read_unlock(&tasklist_lock);
190 
191 	return retval;
192 }
193 
194 static inline int has_stopped_jobs(int pgrp)
195 {
196 	int retval = 0;
197 	struct task_struct *p;
198 
199 	do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
200 		if (p->state != TASK_STOPPED)
201 			continue;
202 
203 		/* If p is stopped by a debugger on a signal that won't
204 		   stop it, then don't count p as stopped.  This isn't
205 		   perfect but it's a good approximation.  */
206 		if (unlikely (p->ptrace)
207 		    && p->exit_code != SIGSTOP
208 		    && p->exit_code != SIGTSTP
209 		    && p->exit_code != SIGTTOU
210 		    && p->exit_code != SIGTTIN)
211 			continue;
212 
213 		retval = 1;
214 		break;
215 	} while_each_task_pid(pgrp, PIDTYPE_PGID, p);
216 	return retval;
217 }
218 
219 /**
220  * reparent_to_init - Reparent the calling kernel thread to the init task.
221  *
222  * If a kernel thread is launched as a result of a system call, or if
223  * it ever exits, it should generally reparent itself to init so that
224  * it is correctly cleaned up on exit.
225  *
226  * The various task state such as scheduling policy and priority may have
227  * been inherited from a user process, so we reset them to sane values here.
228  *
229  * NOTE that reparent_to_init() gives the caller full capabilities.
230  */
231 static inline void reparent_to_init(void)
232 {
233 	write_lock_irq(&tasklist_lock);
234 
235 	ptrace_unlink(current);
236 	/* Reparent to init */
237 	REMOVE_LINKS(current);
238 	current->parent = child_reaper;
239 	current->real_parent = child_reaper;
240 	SET_LINKS(current);
241 
242 	/* Set the exit signal to SIGCHLD so we signal init on exit */
243 	current->exit_signal = SIGCHLD;
244 
245 	if ((current->policy == SCHED_NORMAL) && (task_nice(current) < 0))
246 		set_user_nice(current, 0);
247 	/* cpus_allowed? */
248 	/* rt_priority? */
249 	/* signals? */
250 	security_task_reparent_to_init(current);
251 	memcpy(current->signal->rlim, init_task.signal->rlim,
252 	       sizeof(current->signal->rlim));
253 	atomic_inc(&(INIT_USER->__count));
254 	write_unlock_irq(&tasklist_lock);
255 	switch_uid(INIT_USER);
256 }
257 
258 void __set_special_pids(pid_t session, pid_t pgrp)
259 {
260 	struct task_struct *curr = current;
261 
262 	if (curr->signal->session != session) {
263 		detach_pid(curr, PIDTYPE_SID);
264 		curr->signal->session = session;
265 		attach_pid(curr, PIDTYPE_SID, session);
266 	}
267 	if (process_group(curr) != pgrp) {
268 		detach_pid(curr, PIDTYPE_PGID);
269 		curr->signal->pgrp = pgrp;
270 		attach_pid(curr, PIDTYPE_PGID, pgrp);
271 	}
272 }
273 
274 void set_special_pids(pid_t session, pid_t pgrp)
275 {
276 	write_lock_irq(&tasklist_lock);
277 	__set_special_pids(session, pgrp);
278 	write_unlock_irq(&tasklist_lock);
279 }
280 
281 /*
282  * Let kernel threads use this to say that they
283  * allow a certain signal (since daemonize() will
284  * have disabled all of them by default).
285  */
286 int allow_signal(int sig)
287 {
288 	if (!valid_signal(sig) || sig < 1)
289 		return -EINVAL;
290 
291 	spin_lock_irq(&current->sighand->siglock);
292 	sigdelset(&current->blocked, sig);
293 	if (!current->mm) {
294 		/* Kernel threads handle their own signals.
295 		   Let the signal code know it'll be handled, so
296 		   that they don't get converted to SIGKILL or
297 		   just silently dropped */
298 		current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2;
299 	}
300 	recalc_sigpending();
301 	spin_unlock_irq(&current->sighand->siglock);
302 	return 0;
303 }
304 
305 EXPORT_SYMBOL(allow_signal);
306 
307 int disallow_signal(int sig)
308 {
309 	if (!valid_signal(sig) || sig < 1)
310 		return -EINVAL;
311 
312 	spin_lock_irq(&current->sighand->siglock);
313 	sigaddset(&current->blocked, sig);
314 	recalc_sigpending();
315 	spin_unlock_irq(&current->sighand->siglock);
316 	return 0;
317 }
318 
319 EXPORT_SYMBOL(disallow_signal);
320 
321 /*
322  *	Put all the gunge required to become a kernel thread without
323  *	attached user resources in one place where it belongs.
324  */
325 
326 void daemonize(const char *name, ...)
327 {
328 	va_list args;
329 	struct fs_struct *fs;
330 	sigset_t blocked;
331 
332 	va_start(args, name);
333 	vsnprintf(current->comm, sizeof(current->comm), name, args);
334 	va_end(args);
335 
336 	/*
337 	 * If we were started as result of loading a module, close all of the
338 	 * user space pages.  We don't need them, and if we didn't close them
339 	 * they would be locked into memory.
340 	 */
341 	exit_mm(current);
342 
343 	set_special_pids(1, 1);
344 	down(&tty_sem);
345 	current->signal->tty = NULL;
346 	up(&tty_sem);
347 
348 	/* Block and flush all signals */
349 	sigfillset(&blocked);
350 	sigprocmask(SIG_BLOCK, &blocked, NULL);
351 	flush_signals(current);
352 
353 	/* Become as one with the init task */
354 
355 	exit_fs(current);	/* current->fs->count--; */
356 	fs = init_task.fs;
357 	current->fs = fs;
358 	atomic_inc(&fs->count);
359  	exit_files(current);
360 	current->files = init_task.files;
361 	atomic_inc(&current->files->count);
362 
363 	reparent_to_init();
364 }
365 
366 EXPORT_SYMBOL(daemonize);
367 
368 static inline void close_files(struct files_struct * files)
369 {
370 	int i, j;
371 	struct fdtable *fdt;
372 
373 	j = 0;
374 
375 	/*
376 	 * It is safe to dereference the fd table without RCU or
377 	 * ->file_lock because this is the last reference to the
378 	 * files structure.
379 	 */
380 	fdt = files_fdtable(files);
381 	for (;;) {
382 		unsigned long set;
383 		i = j * __NFDBITS;
384 		if (i >= fdt->max_fdset || i >= fdt->max_fds)
385 			break;
386 		set = fdt->open_fds->fds_bits[j++];
387 		while (set) {
388 			if (set & 1) {
389 				struct file * file = xchg(&fdt->fd[i], NULL);
390 				if (file)
391 					filp_close(file, files);
392 			}
393 			i++;
394 			set >>= 1;
395 		}
396 	}
397 }
398 
399 struct files_struct *get_files_struct(struct task_struct *task)
400 {
401 	struct files_struct *files;
402 
403 	task_lock(task);
404 	files = task->files;
405 	if (files)
406 		atomic_inc(&files->count);
407 	task_unlock(task);
408 
409 	return files;
410 }
411 
412 void fastcall put_files_struct(struct files_struct *files)
413 {
414 	struct fdtable *fdt;
415 
416 	if (atomic_dec_and_test(&files->count)) {
417 		close_files(files);
418 		/*
419 		 * Free the fd and fdset arrays if we expanded them.
420 		 * If the fdtable was embedded, pass files for freeing
421 		 * at the end of the RCU grace period. Otherwise,
422 		 * you can free files immediately.
423 		 */
424 		fdt = files_fdtable(files);
425 		if (fdt == &files->fdtab)
426 			fdt->free_files = files;
427 		else
428 			kmem_cache_free(files_cachep, files);
429 		free_fdtable(fdt);
430 	}
431 }
432 
433 EXPORT_SYMBOL(put_files_struct);
434 
435 static inline void __exit_files(struct task_struct *tsk)
436 {
437 	struct files_struct * files = tsk->files;
438 
439 	if (files) {
440 		task_lock(tsk);
441 		tsk->files = NULL;
442 		task_unlock(tsk);
443 		put_files_struct(files);
444 	}
445 }
446 
447 void exit_files(struct task_struct *tsk)
448 {
449 	__exit_files(tsk);
450 }
451 
452 static inline void __put_fs_struct(struct fs_struct *fs)
453 {
454 	/* No need to hold fs->lock if we are killing it */
455 	if (atomic_dec_and_test(&fs->count)) {
456 		dput(fs->root);
457 		mntput(fs->rootmnt);
458 		dput(fs->pwd);
459 		mntput(fs->pwdmnt);
460 		if (fs->altroot) {
461 			dput(fs->altroot);
462 			mntput(fs->altrootmnt);
463 		}
464 		kmem_cache_free(fs_cachep, fs);
465 	}
466 }
467 
468 void put_fs_struct(struct fs_struct *fs)
469 {
470 	__put_fs_struct(fs);
471 }
472 
473 static inline void __exit_fs(struct task_struct *tsk)
474 {
475 	struct fs_struct * fs = tsk->fs;
476 
477 	if (fs) {
478 		task_lock(tsk);
479 		tsk->fs = NULL;
480 		task_unlock(tsk);
481 		__put_fs_struct(fs);
482 	}
483 }
484 
485 void exit_fs(struct task_struct *tsk)
486 {
487 	__exit_fs(tsk);
488 }
489 
490 EXPORT_SYMBOL_GPL(exit_fs);
491 
492 /*
493  * Turn us into a lazy TLB process if we
494  * aren't already..
495  */
496 static void exit_mm(struct task_struct * tsk)
497 {
498 	struct mm_struct *mm = tsk->mm;
499 
500 	mm_release(tsk, mm);
501 	if (!mm)
502 		return;
503 	/*
504 	 * Serialize with any possible pending coredump.
505 	 * We must hold mmap_sem around checking core_waiters
506 	 * and clearing tsk->mm.  The core-inducing thread
507 	 * will increment core_waiters for each thread in the
508 	 * group with ->mm != NULL.
509 	 */
510 	down_read(&mm->mmap_sem);
511 	if (mm->core_waiters) {
512 		up_read(&mm->mmap_sem);
513 		down_write(&mm->mmap_sem);
514 		if (!--mm->core_waiters)
515 			complete(mm->core_startup_done);
516 		up_write(&mm->mmap_sem);
517 
518 		wait_for_completion(&mm->core_done);
519 		down_read(&mm->mmap_sem);
520 	}
521 	atomic_inc(&mm->mm_count);
522 	if (mm != tsk->active_mm) BUG();
523 	/* more a memory barrier than a real lock */
524 	task_lock(tsk);
525 	tsk->mm = NULL;
526 	up_read(&mm->mmap_sem);
527 	enter_lazy_tlb(mm, current);
528 	task_unlock(tsk);
529 	mmput(mm);
530 }
531 
532 static inline void choose_new_parent(task_t *p, task_t *reaper, task_t *child_reaper)
533 {
534 	/*
535 	 * Make sure we're not reparenting to ourselves and that
536 	 * the parent is not a zombie.
537 	 */
538 	BUG_ON(p == reaper || reaper->exit_state >= EXIT_ZOMBIE);
539 	p->real_parent = reaper;
540 }
541 
542 static inline void reparent_thread(task_t *p, task_t *father, int traced)
543 {
544 	/* We don't want people slaying init.  */
545 	if (p->exit_signal != -1)
546 		p->exit_signal = SIGCHLD;
547 
548 	if (p->pdeath_signal)
549 		/* We already hold the tasklist_lock here.  */
550 		group_send_sig_info(p->pdeath_signal, SEND_SIG_NOINFO, p);
551 
552 	/* Move the child from its dying parent to the new one.  */
553 	if (unlikely(traced)) {
554 		/* Preserve ptrace links if someone else is tracing this child.  */
555 		list_del_init(&p->ptrace_list);
556 		if (p->parent != p->real_parent)
557 			list_add(&p->ptrace_list, &p->real_parent->ptrace_children);
558 	} else {
559 		/* If this child is being traced, then we're the one tracing it
560 		 * anyway, so let go of it.
561 		 */
562 		p->ptrace = 0;
563 		list_del_init(&p->sibling);
564 		p->parent = p->real_parent;
565 		list_add_tail(&p->sibling, &p->parent->children);
566 
567 		/* If we'd notified the old parent about this child's death,
568 		 * also notify the new parent.
569 		 */
570 		if (p->exit_state == EXIT_ZOMBIE && p->exit_signal != -1 &&
571 		    thread_group_empty(p))
572 			do_notify_parent(p, p->exit_signal);
573 		else if (p->state == TASK_TRACED) {
574 			/*
575 			 * If it was at a trace stop, turn it into
576 			 * a normal stop since it's no longer being
577 			 * traced.
578 			 */
579 			ptrace_untrace(p);
580 		}
581 	}
582 
583 	/*
584 	 * process group orphan check
585 	 * Case ii: Our child is in a different pgrp
586 	 * than we are, and it was the only connection
587 	 * outside, so the child pgrp is now orphaned.
588 	 */
589 	if ((process_group(p) != process_group(father)) &&
590 	    (p->signal->session == father->signal->session)) {
591 		int pgrp = process_group(p);
592 
593 		if (will_become_orphaned_pgrp(pgrp, NULL) && has_stopped_jobs(pgrp)) {
594 			__kill_pg_info(SIGHUP, SEND_SIG_PRIV, pgrp);
595 			__kill_pg_info(SIGCONT, SEND_SIG_PRIV, pgrp);
596 		}
597 	}
598 }
599 
600 /*
601  * When we die, we re-parent all our children.
602  * Try to give them to another thread in our thread
603  * group, and if no such member exists, give it to
604  * the global child reaper process (ie "init")
605  */
606 static inline void forget_original_parent(struct task_struct * father,
607 					  struct list_head *to_release)
608 {
609 	struct task_struct *p, *reaper = father;
610 	struct list_head *_p, *_n;
611 
612 	do {
613 		reaper = next_thread(reaper);
614 		if (reaper == father) {
615 			reaper = child_reaper;
616 			break;
617 		}
618 	} while (reaper->exit_state);
619 
620 	/*
621 	 * There are only two places where our children can be:
622 	 *
623 	 * - in our child list
624 	 * - in our ptraced child list
625 	 *
626 	 * Search them and reparent children.
627 	 */
628 	list_for_each_safe(_p, _n, &father->children) {
629 		int ptrace;
630 		p = list_entry(_p,struct task_struct,sibling);
631 
632 		ptrace = p->ptrace;
633 
634 		/* if father isn't the real parent, then ptrace must be enabled */
635 		BUG_ON(father != p->real_parent && !ptrace);
636 
637 		if (father == p->real_parent) {
638 			/* reparent with a reaper, real father it's us */
639 			choose_new_parent(p, reaper, child_reaper);
640 			reparent_thread(p, father, 0);
641 		} else {
642 			/* reparent ptraced task to its real parent */
643 			__ptrace_unlink (p);
644 			if (p->exit_state == EXIT_ZOMBIE && p->exit_signal != -1 &&
645 			    thread_group_empty(p))
646 				do_notify_parent(p, p->exit_signal);
647 		}
648 
649 		/*
650 		 * if the ptraced child is a zombie with exit_signal == -1
651 		 * we must collect it before we exit, or it will remain
652 		 * zombie forever since we prevented it from self-reap itself
653 		 * while it was being traced by us, to be able to see it in wait4.
654 		 */
655 		if (unlikely(ptrace && p->exit_state == EXIT_ZOMBIE && p->exit_signal == -1))
656 			list_add(&p->ptrace_list, to_release);
657 	}
658 	list_for_each_safe(_p, _n, &father->ptrace_children) {
659 		p = list_entry(_p,struct task_struct,ptrace_list);
660 		choose_new_parent(p, reaper, child_reaper);
661 		reparent_thread(p, father, 1);
662 	}
663 }
664 
665 /*
666  * Send signals to all our closest relatives so that they know
667  * to properly mourn us..
668  */
669 static void exit_notify(struct task_struct *tsk)
670 {
671 	int state;
672 	struct task_struct *t;
673 	struct list_head ptrace_dead, *_p, *_n;
674 
675 	if (signal_pending(tsk) && !(tsk->signal->flags & SIGNAL_GROUP_EXIT)
676 	    && !thread_group_empty(tsk)) {
677 		/*
678 		 * This occurs when there was a race between our exit
679 		 * syscall and a group signal choosing us as the one to
680 		 * wake up.  It could be that we are the only thread
681 		 * alerted to check for pending signals, but another thread
682 		 * should be woken now to take the signal since we will not.
683 		 * Now we'll wake all the threads in the group just to make
684 		 * sure someone gets all the pending signals.
685 		 */
686 		read_lock(&tasklist_lock);
687 		spin_lock_irq(&tsk->sighand->siglock);
688 		for (t = next_thread(tsk); t != tsk; t = next_thread(t))
689 			if (!signal_pending(t) && !(t->flags & PF_EXITING)) {
690 				recalc_sigpending_tsk(t);
691 				if (signal_pending(t))
692 					signal_wake_up(t, 0);
693 			}
694 		spin_unlock_irq(&tsk->sighand->siglock);
695 		read_unlock(&tasklist_lock);
696 	}
697 
698 	write_lock_irq(&tasklist_lock);
699 
700 	/*
701 	 * This does two things:
702 	 *
703   	 * A.  Make init inherit all the child processes
704 	 * B.  Check to see if any process groups have become orphaned
705 	 *	as a result of our exiting, and if they have any stopped
706 	 *	jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
707 	 */
708 
709 	INIT_LIST_HEAD(&ptrace_dead);
710 	forget_original_parent(tsk, &ptrace_dead);
711 	BUG_ON(!list_empty(&tsk->children));
712 	BUG_ON(!list_empty(&tsk->ptrace_children));
713 
714 	/*
715 	 * Check to see if any process groups have become orphaned
716 	 * as a result of our exiting, and if they have any stopped
717 	 * jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
718 	 *
719 	 * Case i: Our father is in a different pgrp than we are
720 	 * and we were the only connection outside, so our pgrp
721 	 * is about to become orphaned.
722 	 */
723 
724 	t = tsk->real_parent;
725 
726 	if ((process_group(t) != process_group(tsk)) &&
727 	    (t->signal->session == tsk->signal->session) &&
728 	    will_become_orphaned_pgrp(process_group(tsk), tsk) &&
729 	    has_stopped_jobs(process_group(tsk))) {
730 		__kill_pg_info(SIGHUP, SEND_SIG_PRIV, process_group(tsk));
731 		__kill_pg_info(SIGCONT, SEND_SIG_PRIV, process_group(tsk));
732 	}
733 
734 	/* Let father know we died
735 	 *
736 	 * Thread signals are configurable, but you aren't going to use
737 	 * that to send signals to arbitary processes.
738 	 * That stops right now.
739 	 *
740 	 * If the parent exec id doesn't match the exec id we saved
741 	 * when we started then we know the parent has changed security
742 	 * domain.
743 	 *
744 	 * If our self_exec id doesn't match our parent_exec_id then
745 	 * we have changed execution domain as these two values started
746 	 * the same after a fork.
747 	 *
748 	 */
749 
750 	if (tsk->exit_signal != SIGCHLD && tsk->exit_signal != -1 &&
751 	    ( tsk->parent_exec_id != t->self_exec_id  ||
752 	      tsk->self_exec_id != tsk->parent_exec_id)
753 	    && !capable(CAP_KILL))
754 		tsk->exit_signal = SIGCHLD;
755 
756 
757 	/* If something other than our normal parent is ptracing us, then
758 	 * send it a SIGCHLD instead of honoring exit_signal.  exit_signal
759 	 * only has special meaning to our real parent.
760 	 */
761 	if (tsk->exit_signal != -1 && thread_group_empty(tsk)) {
762 		int signal = tsk->parent == tsk->real_parent ? tsk->exit_signal : SIGCHLD;
763 		do_notify_parent(tsk, signal);
764 	} else if (tsk->ptrace) {
765 		do_notify_parent(tsk, SIGCHLD);
766 	}
767 
768 	state = EXIT_ZOMBIE;
769 	if (tsk->exit_signal == -1 &&
770 	    (likely(tsk->ptrace == 0) ||
771 	     unlikely(tsk->parent->signal->flags & SIGNAL_GROUP_EXIT)))
772 		state = EXIT_DEAD;
773 	tsk->exit_state = state;
774 
775 	write_unlock_irq(&tasklist_lock);
776 
777 	list_for_each_safe(_p, _n, &ptrace_dead) {
778 		list_del_init(_p);
779 		t = list_entry(_p,struct task_struct,ptrace_list);
780 		release_task(t);
781 	}
782 
783 	/* If the process is dead, release it - nobody will wait for it */
784 	if (state == EXIT_DEAD)
785 		release_task(tsk);
786 }
787 
788 fastcall NORET_TYPE void do_exit(long code)
789 {
790 	struct task_struct *tsk = current;
791 	int group_dead;
792 
793 	profile_task_exit(tsk);
794 
795 	WARN_ON(atomic_read(&tsk->fs_excl));
796 
797 	if (unlikely(in_interrupt()))
798 		panic("Aiee, killing interrupt handler!");
799 	if (unlikely(!tsk->pid))
800 		panic("Attempted to kill the idle task!");
801 	if (unlikely(tsk->pid == 1))
802 		panic("Attempted to kill init!");
803 	if (tsk->io_context)
804 		exit_io_context();
805 
806 	if (unlikely(current->ptrace & PT_TRACE_EXIT)) {
807 		current->ptrace_message = code;
808 		ptrace_notify((PTRACE_EVENT_EXIT << 8) | SIGTRAP);
809 	}
810 
811 	/*
812 	 * We're taking recursive faults here in do_exit. Safest is to just
813 	 * leave this task alone and wait for reboot.
814 	 */
815 	if (unlikely(tsk->flags & PF_EXITING)) {
816 		printk(KERN_ALERT
817 			"Fixing recursive fault but reboot is needed!\n");
818 		set_current_state(TASK_UNINTERRUPTIBLE);
819 		schedule();
820 	}
821 
822 	tsk->flags |= PF_EXITING;
823 
824 	/*
825 	 * Make sure we don't try to process any timer firings
826 	 * while we are already exiting.
827 	 */
828  	tsk->it_virt_expires = cputime_zero;
829  	tsk->it_prof_expires = cputime_zero;
830 	tsk->it_sched_expires = 0;
831 
832 	if (unlikely(in_atomic()))
833 		printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
834 				current->comm, current->pid,
835 				preempt_count());
836 
837 	acct_update_integrals(tsk);
838 	if (tsk->mm) {
839 		update_hiwater_rss(tsk->mm);
840 		update_hiwater_vm(tsk->mm);
841 	}
842 	group_dead = atomic_dec_and_test(&tsk->signal->live);
843 	if (group_dead) {
844  		del_timer_sync(&tsk->signal->real_timer);
845 		exit_itimers(tsk->signal);
846 		acct_process(code);
847 	}
848 	exit_mm(tsk);
849 
850 	exit_sem(tsk);
851 	__exit_files(tsk);
852 	__exit_fs(tsk);
853 	exit_namespace(tsk);
854 	exit_thread();
855 	cpuset_exit(tsk);
856 	exit_keys(tsk);
857 
858 	if (group_dead && tsk->signal->leader)
859 		disassociate_ctty(1);
860 
861 	module_put(tsk->thread_info->exec_domain->module);
862 	if (tsk->binfmt)
863 		module_put(tsk->binfmt->module);
864 
865 	tsk->exit_code = code;
866 	exit_notify(tsk);
867 #ifdef CONFIG_NUMA
868 	mpol_free(tsk->mempolicy);
869 	tsk->mempolicy = NULL;
870 #endif
871 
872 	/* PF_DEAD causes final put_task_struct after we schedule. */
873 	preempt_disable();
874 	BUG_ON(tsk->flags & PF_DEAD);
875 	tsk->flags |= PF_DEAD;
876 
877 	schedule();
878 	BUG();
879 	/* Avoid "noreturn function does return".  */
880 	for (;;) ;
881 }
882 
883 EXPORT_SYMBOL_GPL(do_exit);
884 
885 NORET_TYPE void complete_and_exit(struct completion *comp, long code)
886 {
887 	if (comp)
888 		complete(comp);
889 
890 	do_exit(code);
891 }
892 
893 EXPORT_SYMBOL(complete_and_exit);
894 
895 asmlinkage long sys_exit(int error_code)
896 {
897 	do_exit((error_code&0xff)<<8);
898 }
899 
900 task_t fastcall *next_thread(const task_t *p)
901 {
902 	return pid_task(p->pids[PIDTYPE_TGID].pid_list.next, PIDTYPE_TGID);
903 }
904 
905 EXPORT_SYMBOL(next_thread);
906 
907 /*
908  * Take down every thread in the group.  This is called by fatal signals
909  * as well as by sys_exit_group (below).
910  */
911 NORET_TYPE void
912 do_group_exit(int exit_code)
913 {
914 	BUG_ON(exit_code & 0x80); /* core dumps don't get here */
915 
916 	if (current->signal->flags & SIGNAL_GROUP_EXIT)
917 		exit_code = current->signal->group_exit_code;
918 	else if (!thread_group_empty(current)) {
919 		struct signal_struct *const sig = current->signal;
920 		struct sighand_struct *const sighand = current->sighand;
921 		read_lock(&tasklist_lock);
922 		spin_lock_irq(&sighand->siglock);
923 		if (sig->flags & SIGNAL_GROUP_EXIT)
924 			/* Another thread got here before we took the lock.  */
925 			exit_code = sig->group_exit_code;
926 		else {
927 			sig->flags = SIGNAL_GROUP_EXIT;
928 			sig->group_exit_code = exit_code;
929 			zap_other_threads(current);
930 		}
931 		spin_unlock_irq(&sighand->siglock);
932 		read_unlock(&tasklist_lock);
933 	}
934 
935 	do_exit(exit_code);
936 	/* NOTREACHED */
937 }
938 
939 /*
940  * this kills every thread in the thread group. Note that any externally
941  * wait4()-ing process will get the correct exit code - even if this
942  * thread is not the thread group leader.
943  */
944 asmlinkage void sys_exit_group(int error_code)
945 {
946 	do_group_exit((error_code & 0xff) << 8);
947 }
948 
949 static int eligible_child(pid_t pid, int options, task_t *p)
950 {
951 	if (pid > 0) {
952 		if (p->pid != pid)
953 			return 0;
954 	} else if (!pid) {
955 		if (process_group(p) != process_group(current))
956 			return 0;
957 	} else if (pid != -1) {
958 		if (process_group(p) != -pid)
959 			return 0;
960 	}
961 
962 	/*
963 	 * Do not consider detached threads that are
964 	 * not ptraced:
965 	 */
966 	if (p->exit_signal == -1 && !p->ptrace)
967 		return 0;
968 
969 	/* Wait for all children (clone and not) if __WALL is set;
970 	 * otherwise, wait for clone children *only* if __WCLONE is
971 	 * set; otherwise, wait for non-clone children *only*.  (Note:
972 	 * A "clone" child here is one that reports to its parent
973 	 * using a signal other than SIGCHLD.) */
974 	if (((p->exit_signal != SIGCHLD) ^ ((options & __WCLONE) != 0))
975 	    && !(options & __WALL))
976 		return 0;
977 	/*
978 	 * Do not consider thread group leaders that are
979 	 * in a non-empty thread group:
980 	 */
981 	if (current->tgid != p->tgid && delay_group_leader(p))
982 		return 2;
983 
984 	if (security_task_wait(p))
985 		return 0;
986 
987 	return 1;
988 }
989 
990 static int wait_noreap_copyout(task_t *p, pid_t pid, uid_t uid,
991 			       int why, int status,
992 			       struct siginfo __user *infop,
993 			       struct rusage __user *rusagep)
994 {
995 	int retval = rusagep ? getrusage(p, RUSAGE_BOTH, rusagep) : 0;
996 	put_task_struct(p);
997 	if (!retval)
998 		retval = put_user(SIGCHLD, &infop->si_signo);
999 	if (!retval)
1000 		retval = put_user(0, &infop->si_errno);
1001 	if (!retval)
1002 		retval = put_user((short)why, &infop->si_code);
1003 	if (!retval)
1004 		retval = put_user(pid, &infop->si_pid);
1005 	if (!retval)
1006 		retval = put_user(uid, &infop->si_uid);
1007 	if (!retval)
1008 		retval = put_user(status, &infop->si_status);
1009 	if (!retval)
1010 		retval = pid;
1011 	return retval;
1012 }
1013 
1014 /*
1015  * Handle sys_wait4 work for one task in state EXIT_ZOMBIE.  We hold
1016  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1017  * the lock and this task is uninteresting.  If we return nonzero, we have
1018  * released the lock and the system call should return.
1019  */
1020 static int wait_task_zombie(task_t *p, int noreap,
1021 			    struct siginfo __user *infop,
1022 			    int __user *stat_addr, struct rusage __user *ru)
1023 {
1024 	unsigned long state;
1025 	int retval;
1026 	int status;
1027 
1028 	if (unlikely(noreap)) {
1029 		pid_t pid = p->pid;
1030 		uid_t uid = p->uid;
1031 		int exit_code = p->exit_code;
1032 		int why, status;
1033 
1034 		if (unlikely(p->exit_state != EXIT_ZOMBIE))
1035 			return 0;
1036 		if (unlikely(p->exit_signal == -1 && p->ptrace == 0))
1037 			return 0;
1038 		get_task_struct(p);
1039 		read_unlock(&tasklist_lock);
1040 		if ((exit_code & 0x7f) == 0) {
1041 			why = CLD_EXITED;
1042 			status = exit_code >> 8;
1043 		} else {
1044 			why = (exit_code & 0x80) ? CLD_DUMPED : CLD_KILLED;
1045 			status = exit_code & 0x7f;
1046 		}
1047 		return wait_noreap_copyout(p, pid, uid, why,
1048 					   status, infop, ru);
1049 	}
1050 
1051 	/*
1052 	 * Try to move the task's state to DEAD
1053 	 * only one thread is allowed to do this:
1054 	 */
1055 	state = xchg(&p->exit_state, EXIT_DEAD);
1056 	if (state != EXIT_ZOMBIE) {
1057 		BUG_ON(state != EXIT_DEAD);
1058 		return 0;
1059 	}
1060 	if (unlikely(p->exit_signal == -1 && p->ptrace == 0)) {
1061 		/*
1062 		 * This can only happen in a race with a ptraced thread
1063 		 * dying on another processor.
1064 		 */
1065 		return 0;
1066 	}
1067 
1068 	if (likely(p->real_parent == p->parent) && likely(p->signal)) {
1069 		/*
1070 		 * The resource counters for the group leader are in its
1071 		 * own task_struct.  Those for dead threads in the group
1072 		 * are in its signal_struct, as are those for the child
1073 		 * processes it has previously reaped.  All these
1074 		 * accumulate in the parent's signal_struct c* fields.
1075 		 *
1076 		 * We don't bother to take a lock here to protect these
1077 		 * p->signal fields, because they are only touched by
1078 		 * __exit_signal, which runs with tasklist_lock
1079 		 * write-locked anyway, and so is excluded here.  We do
1080 		 * need to protect the access to p->parent->signal fields,
1081 		 * as other threads in the parent group can be right
1082 		 * here reaping other children at the same time.
1083 		 */
1084 		spin_lock_irq(&p->parent->sighand->siglock);
1085 		p->parent->signal->cutime =
1086 			cputime_add(p->parent->signal->cutime,
1087 			cputime_add(p->utime,
1088 			cputime_add(p->signal->utime,
1089 				    p->signal->cutime)));
1090 		p->parent->signal->cstime =
1091 			cputime_add(p->parent->signal->cstime,
1092 			cputime_add(p->stime,
1093 			cputime_add(p->signal->stime,
1094 				    p->signal->cstime)));
1095 		p->parent->signal->cmin_flt +=
1096 			p->min_flt + p->signal->min_flt + p->signal->cmin_flt;
1097 		p->parent->signal->cmaj_flt +=
1098 			p->maj_flt + p->signal->maj_flt + p->signal->cmaj_flt;
1099 		p->parent->signal->cnvcsw +=
1100 			p->nvcsw + p->signal->nvcsw + p->signal->cnvcsw;
1101 		p->parent->signal->cnivcsw +=
1102 			p->nivcsw + p->signal->nivcsw + p->signal->cnivcsw;
1103 		spin_unlock_irq(&p->parent->sighand->siglock);
1104 	}
1105 
1106 	/*
1107 	 * Now we are sure this task is interesting, and no other
1108 	 * thread can reap it because we set its state to EXIT_DEAD.
1109 	 */
1110 	read_unlock(&tasklist_lock);
1111 
1112 	retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
1113 	status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1114 		? p->signal->group_exit_code : p->exit_code;
1115 	if (!retval && stat_addr)
1116 		retval = put_user(status, stat_addr);
1117 	if (!retval && infop)
1118 		retval = put_user(SIGCHLD, &infop->si_signo);
1119 	if (!retval && infop)
1120 		retval = put_user(0, &infop->si_errno);
1121 	if (!retval && infop) {
1122 		int why;
1123 
1124 		if ((status & 0x7f) == 0) {
1125 			why = CLD_EXITED;
1126 			status >>= 8;
1127 		} else {
1128 			why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
1129 			status &= 0x7f;
1130 		}
1131 		retval = put_user((short)why, &infop->si_code);
1132 		if (!retval)
1133 			retval = put_user(status, &infop->si_status);
1134 	}
1135 	if (!retval && infop)
1136 		retval = put_user(p->pid, &infop->si_pid);
1137 	if (!retval && infop)
1138 		retval = put_user(p->uid, &infop->si_uid);
1139 	if (retval) {
1140 		// TODO: is this safe?
1141 		p->exit_state = EXIT_ZOMBIE;
1142 		return retval;
1143 	}
1144 	retval = p->pid;
1145 	if (p->real_parent != p->parent) {
1146 		write_lock_irq(&tasklist_lock);
1147 		/* Double-check with lock held.  */
1148 		if (p->real_parent != p->parent) {
1149 			__ptrace_unlink(p);
1150 			// TODO: is this safe?
1151 			p->exit_state = EXIT_ZOMBIE;
1152 			/*
1153 			 * If this is not a detached task, notify the parent.
1154 			 * If it's still not detached after that, don't release
1155 			 * it now.
1156 			 */
1157 			if (p->exit_signal != -1) {
1158 				do_notify_parent(p, p->exit_signal);
1159 				if (p->exit_signal != -1)
1160 					p = NULL;
1161 			}
1162 		}
1163 		write_unlock_irq(&tasklist_lock);
1164 	}
1165 	if (p != NULL)
1166 		release_task(p);
1167 	BUG_ON(!retval);
1168 	return retval;
1169 }
1170 
1171 /*
1172  * Handle sys_wait4 work for one task in state TASK_STOPPED.  We hold
1173  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1174  * the lock and this task is uninteresting.  If we return nonzero, we have
1175  * released the lock and the system call should return.
1176  */
1177 static int wait_task_stopped(task_t *p, int delayed_group_leader, int noreap,
1178 			     struct siginfo __user *infop,
1179 			     int __user *stat_addr, struct rusage __user *ru)
1180 {
1181 	int retval, exit_code;
1182 
1183 	if (!p->exit_code)
1184 		return 0;
1185 	if (delayed_group_leader && !(p->ptrace & PT_PTRACED) &&
1186 	    p->signal && p->signal->group_stop_count > 0)
1187 		/*
1188 		 * A group stop is in progress and this is the group leader.
1189 		 * We won't report until all threads have stopped.
1190 		 */
1191 		return 0;
1192 
1193 	/*
1194 	 * Now we are pretty sure this task is interesting.
1195 	 * Make sure it doesn't get reaped out from under us while we
1196 	 * give up the lock and then examine it below.  We don't want to
1197 	 * keep holding onto the tasklist_lock while we call getrusage and
1198 	 * possibly take page faults for user memory.
1199 	 */
1200 	get_task_struct(p);
1201 	read_unlock(&tasklist_lock);
1202 
1203 	if (unlikely(noreap)) {
1204 		pid_t pid = p->pid;
1205 		uid_t uid = p->uid;
1206 		int why = (p->ptrace & PT_PTRACED) ? CLD_TRAPPED : CLD_STOPPED;
1207 
1208 		exit_code = p->exit_code;
1209 		if (unlikely(!exit_code) ||
1210 		    unlikely(p->state & TASK_TRACED))
1211 			goto bail_ref;
1212 		return wait_noreap_copyout(p, pid, uid,
1213 					   why, (exit_code << 8) | 0x7f,
1214 					   infop, ru);
1215 	}
1216 
1217 	write_lock_irq(&tasklist_lock);
1218 
1219 	/*
1220 	 * This uses xchg to be atomic with the thread resuming and setting
1221 	 * it.  It must also be done with the write lock held to prevent a
1222 	 * race with the EXIT_ZOMBIE case.
1223 	 */
1224 	exit_code = xchg(&p->exit_code, 0);
1225 	if (unlikely(p->exit_state)) {
1226 		/*
1227 		 * The task resumed and then died.  Let the next iteration
1228 		 * catch it in EXIT_ZOMBIE.  Note that exit_code might
1229 		 * already be zero here if it resumed and did _exit(0).
1230 		 * The task itself is dead and won't touch exit_code again;
1231 		 * other processors in this function are locked out.
1232 		 */
1233 		p->exit_code = exit_code;
1234 		exit_code = 0;
1235 	}
1236 	if (unlikely(exit_code == 0)) {
1237 		/*
1238 		 * Another thread in this function got to it first, or it
1239 		 * resumed, or it resumed and then died.
1240 		 */
1241 		write_unlock_irq(&tasklist_lock);
1242 bail_ref:
1243 		put_task_struct(p);
1244 		/*
1245 		 * We are returning to the wait loop without having successfully
1246 		 * removed the process and having released the lock. We cannot
1247 		 * continue, since the "p" task pointer is potentially stale.
1248 		 *
1249 		 * Return -EAGAIN, and do_wait() will restart the loop from the
1250 		 * beginning. Do _not_ re-acquire the lock.
1251 		 */
1252 		return -EAGAIN;
1253 	}
1254 
1255 	/* move to end of parent's list to avoid starvation */
1256 	remove_parent(p);
1257 	add_parent(p, p->parent);
1258 
1259 	write_unlock_irq(&tasklist_lock);
1260 
1261 	retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
1262 	if (!retval && stat_addr)
1263 		retval = put_user((exit_code << 8) | 0x7f, stat_addr);
1264 	if (!retval && infop)
1265 		retval = put_user(SIGCHLD, &infop->si_signo);
1266 	if (!retval && infop)
1267 		retval = put_user(0, &infop->si_errno);
1268 	if (!retval && infop)
1269 		retval = put_user((short)((p->ptrace & PT_PTRACED)
1270 					  ? CLD_TRAPPED : CLD_STOPPED),
1271 				  &infop->si_code);
1272 	if (!retval && infop)
1273 		retval = put_user(exit_code, &infop->si_status);
1274 	if (!retval && infop)
1275 		retval = put_user(p->pid, &infop->si_pid);
1276 	if (!retval && infop)
1277 		retval = put_user(p->uid, &infop->si_uid);
1278 	if (!retval)
1279 		retval = p->pid;
1280 	put_task_struct(p);
1281 
1282 	BUG_ON(!retval);
1283 	return retval;
1284 }
1285 
1286 /*
1287  * Handle do_wait work for one task in a live, non-stopped state.
1288  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1289  * the lock and this task is uninteresting.  If we return nonzero, we have
1290  * released the lock and the system call should return.
1291  */
1292 static int wait_task_continued(task_t *p, int noreap,
1293 			       struct siginfo __user *infop,
1294 			       int __user *stat_addr, struct rusage __user *ru)
1295 {
1296 	int retval;
1297 	pid_t pid;
1298 	uid_t uid;
1299 
1300 	if (unlikely(!p->signal))
1301 		return 0;
1302 
1303 	if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
1304 		return 0;
1305 
1306 	spin_lock_irq(&p->sighand->siglock);
1307 	/* Re-check with the lock held.  */
1308 	if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
1309 		spin_unlock_irq(&p->sighand->siglock);
1310 		return 0;
1311 	}
1312 	if (!noreap)
1313 		p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1314 	spin_unlock_irq(&p->sighand->siglock);
1315 
1316 	pid = p->pid;
1317 	uid = p->uid;
1318 	get_task_struct(p);
1319 	read_unlock(&tasklist_lock);
1320 
1321 	if (!infop) {
1322 		retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
1323 		put_task_struct(p);
1324 		if (!retval && stat_addr)
1325 			retval = put_user(0xffff, stat_addr);
1326 		if (!retval)
1327 			retval = p->pid;
1328 	} else {
1329 		retval = wait_noreap_copyout(p, pid, uid,
1330 					     CLD_CONTINUED, SIGCONT,
1331 					     infop, ru);
1332 		BUG_ON(retval == 0);
1333 	}
1334 
1335 	return retval;
1336 }
1337 
1338 
1339 static inline int my_ptrace_child(struct task_struct *p)
1340 {
1341 	if (!(p->ptrace & PT_PTRACED))
1342 		return 0;
1343 	if (!(p->ptrace & PT_ATTACHED))
1344 		return 1;
1345 	/*
1346 	 * This child was PTRACE_ATTACH'd.  We should be seeing it only if
1347 	 * we are the attacher.  If we are the real parent, this is a race
1348 	 * inside ptrace_attach.  It is waiting for the tasklist_lock,
1349 	 * which we have to switch the parent links, but has already set
1350 	 * the flags in p->ptrace.
1351 	 */
1352 	return (p->parent != p->real_parent);
1353 }
1354 
1355 static long do_wait(pid_t pid, int options, struct siginfo __user *infop,
1356 		    int __user *stat_addr, struct rusage __user *ru)
1357 {
1358 	DECLARE_WAITQUEUE(wait, current);
1359 	struct task_struct *tsk;
1360 	int flag, retval;
1361 
1362 	add_wait_queue(&current->signal->wait_chldexit,&wait);
1363 repeat:
1364 	/*
1365 	 * We will set this flag if we see any child that might later
1366 	 * match our criteria, even if we are not able to reap it yet.
1367 	 */
1368 	flag = 0;
1369 	current->state = TASK_INTERRUPTIBLE;
1370 	read_lock(&tasklist_lock);
1371 	tsk = current;
1372 	do {
1373 		struct task_struct *p;
1374 		struct list_head *_p;
1375 		int ret;
1376 
1377 		list_for_each(_p,&tsk->children) {
1378 			p = list_entry(_p,struct task_struct,sibling);
1379 
1380 			ret = eligible_child(pid, options, p);
1381 			if (!ret)
1382 				continue;
1383 
1384 			switch (p->state) {
1385 			case TASK_TRACED:
1386 				/*
1387 				 * When we hit the race with PTRACE_ATTACH,
1388 				 * we will not report this child.  But the
1389 				 * race means it has not yet been moved to
1390 				 * our ptrace_children list, so we need to
1391 				 * set the flag here to avoid a spurious ECHILD
1392 				 * when the race happens with the only child.
1393 				 */
1394 				flag = 1;
1395 				if (!my_ptrace_child(p))
1396 					continue;
1397 				/*FALLTHROUGH*/
1398 			case TASK_STOPPED:
1399 				/*
1400 				 * It's stopped now, so it might later
1401 				 * continue, exit, or stop again.
1402 				 */
1403 				flag = 1;
1404 				if (!(options & WUNTRACED) &&
1405 				    !my_ptrace_child(p))
1406 					continue;
1407 				retval = wait_task_stopped(p, ret == 2,
1408 							   (options & WNOWAIT),
1409 							   infop,
1410 							   stat_addr, ru);
1411 				if (retval == -EAGAIN)
1412 					goto repeat;
1413 				if (retval != 0) /* He released the lock.  */
1414 					goto end;
1415 				break;
1416 			default:
1417 			// case EXIT_DEAD:
1418 				if (p->exit_state == EXIT_DEAD)
1419 					continue;
1420 			// case EXIT_ZOMBIE:
1421 				if (p->exit_state == EXIT_ZOMBIE) {
1422 					/*
1423 					 * Eligible but we cannot release
1424 					 * it yet:
1425 					 */
1426 					if (ret == 2)
1427 						goto check_continued;
1428 					if (!likely(options & WEXITED))
1429 						continue;
1430 					retval = wait_task_zombie(
1431 						p, (options & WNOWAIT),
1432 						infop, stat_addr, ru);
1433 					/* He released the lock.  */
1434 					if (retval != 0)
1435 						goto end;
1436 					break;
1437 				}
1438 check_continued:
1439 				/*
1440 				 * It's running now, so it might later
1441 				 * exit, stop, or stop and then continue.
1442 				 */
1443 				flag = 1;
1444 				if (!unlikely(options & WCONTINUED))
1445 					continue;
1446 				retval = wait_task_continued(
1447 					p, (options & WNOWAIT),
1448 					infop, stat_addr, ru);
1449 				if (retval != 0) /* He released the lock.  */
1450 					goto end;
1451 				break;
1452 			}
1453 		}
1454 		if (!flag) {
1455 			list_for_each(_p, &tsk->ptrace_children) {
1456 				p = list_entry(_p, struct task_struct,
1457 						ptrace_list);
1458 				if (!eligible_child(pid, options, p))
1459 					continue;
1460 				flag = 1;
1461 				break;
1462 			}
1463 		}
1464 		if (options & __WNOTHREAD)
1465 			break;
1466 		tsk = next_thread(tsk);
1467 		if (tsk->signal != current->signal)
1468 			BUG();
1469 	} while (tsk != current);
1470 
1471 	read_unlock(&tasklist_lock);
1472 	if (flag) {
1473 		retval = 0;
1474 		if (options & WNOHANG)
1475 			goto end;
1476 		retval = -ERESTARTSYS;
1477 		if (signal_pending(current))
1478 			goto end;
1479 		schedule();
1480 		goto repeat;
1481 	}
1482 	retval = -ECHILD;
1483 end:
1484 	current->state = TASK_RUNNING;
1485 	remove_wait_queue(&current->signal->wait_chldexit,&wait);
1486 	if (infop) {
1487 		if (retval > 0)
1488 		retval = 0;
1489 		else {
1490 			/*
1491 			 * For a WNOHANG return, clear out all the fields
1492 			 * we would set so the user can easily tell the
1493 			 * difference.
1494 			 */
1495 			if (!retval)
1496 				retval = put_user(0, &infop->si_signo);
1497 			if (!retval)
1498 				retval = put_user(0, &infop->si_errno);
1499 			if (!retval)
1500 				retval = put_user(0, &infop->si_code);
1501 			if (!retval)
1502 				retval = put_user(0, &infop->si_pid);
1503 			if (!retval)
1504 				retval = put_user(0, &infop->si_uid);
1505 			if (!retval)
1506 				retval = put_user(0, &infop->si_status);
1507 		}
1508 	}
1509 	return retval;
1510 }
1511 
1512 asmlinkage long sys_waitid(int which, pid_t pid,
1513 			   struct siginfo __user *infop, int options,
1514 			   struct rusage __user *ru)
1515 {
1516 	long ret;
1517 
1518 	if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED))
1519 		return -EINVAL;
1520 	if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
1521 		return -EINVAL;
1522 
1523 	switch (which) {
1524 	case P_ALL:
1525 		pid = -1;
1526 		break;
1527 	case P_PID:
1528 		if (pid <= 0)
1529 			return -EINVAL;
1530 		break;
1531 	case P_PGID:
1532 		if (pid <= 0)
1533 			return -EINVAL;
1534 		pid = -pid;
1535 		break;
1536 	default:
1537 		return -EINVAL;
1538 	}
1539 
1540 	ret = do_wait(pid, options, infop, NULL, ru);
1541 
1542 	/* avoid REGPARM breakage on x86: */
1543 	prevent_tail_call(ret);
1544 	return ret;
1545 }
1546 
1547 asmlinkage long sys_wait4(pid_t pid, int __user *stat_addr,
1548 			  int options, struct rusage __user *ru)
1549 {
1550 	long ret;
1551 
1552 	if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
1553 			__WNOTHREAD|__WCLONE|__WALL))
1554 		return -EINVAL;
1555 	ret = do_wait(pid, options | WEXITED, NULL, stat_addr, ru);
1556 
1557 	/* avoid REGPARM breakage on x86: */
1558 	prevent_tail_call(ret);
1559 	return ret;
1560 }
1561 
1562 #ifdef __ARCH_WANT_SYS_WAITPID
1563 
1564 /*
1565  * sys_waitpid() remains for compatibility. waitpid() should be
1566  * implemented by calling sys_wait4() from libc.a.
1567  */
1568 asmlinkage long sys_waitpid(pid_t pid, int __user *stat_addr, int options)
1569 {
1570 	return sys_wait4(pid, stat_addr, options, NULL);
1571 }
1572 
1573 #endif
1574