Initial import

1 files changed, 1632 insertions, 0 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
new file mode 100644
index 000000000..490a707c7
--- /dev/null
+++ b/kernel/exit.c
@@ -0,0 +1,1632 @@
+/*
+ *  linux/kernel/exit.c
+ *
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ */
+
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/capability.h>
+#include <linux/completion.h>
+#include <linux/personality.h>
+#include <linux/tty.h>
+#include <linux/iocontext.h>
+#include <linux/key.h>
+#include <linux/security.h>
+#include <linux/cpu.h>
+#include <linux/acct.h>
+#include <linux/tsacct_kern.h>
+#include <linux/file.h>
+#include <linux/fdtable.h>
+#include <linux/freezer.h>
+#include <linux/binfmts.h>
+#include <linux/nsproxy.h>
+#include <linux/pid_namespace.h>
+#include <linux/ptrace.h>
+#include <linux/profile.h>
+#include <linux/mount.h>
+#include <linux/proc_fs.h>
+#include <linux/kthread.h>
+#include <linux/mempolicy.h>
+#include <linux/taskstats_kern.h>
+#include <linux/delayacct.h>
+#include <linux/cgroup.h>
+#include <linux/syscalls.h>
+#include <linux/signal.h>
+#include <linux/posix-timers.h>
+#include <linux/cn_proc.h>
+#include <linux/mutex.h>
+#include <linux/futex.h>
+#include <linux/pipe_fs_i.h>
+#include <linux/audit.h> /* for audit_free() */
+#include <linux/resource.h>
+#include <linux/blkdev.h>
+#include <linux/task_io_accounting_ops.h>
+#include <linux/tracehook.h>
+#include <linux/fs_struct.h>
+#include <linux/init_task.h>
+#include <linux/perf_event.h>
+#include <trace/events/sched.h>
+#include <linux/hw_breakpoint.h>
+#include <linux/oom.h>
+#include <linux/writeback.h>
+#include <linux/shm.h>
+
+#include <asm/uaccess.h>
+#include <asm/unistd.h>
+#include <asm/pgtable.h>
+#include <asm/mmu_context.h>
+
+static void exit_mm(struct task_struct *tsk);
+
+static void __unhash_process(struct task_struct *p, bool group_dead)
+{
+	nr_threads--;
+	detach_pid(p, PIDTYPE_PID);
+	if (group_dead) {
+		detach_pid(p, PIDTYPE_PGID);
+		detach_pid(p, PIDTYPE_SID);
+
+		list_del_rcu(&p->tasks);
+		list_del_init(&p->sibling);
+		__this_cpu_dec(process_counts);
+	}
+	list_del_rcu(&p->thread_group);
+	list_del_rcu(&p->thread_node);
+}
+
+/*
+ * This function expects the tasklist_lock write-locked.
+ */
+static void __exit_signal(struct task_struct *tsk)
+{
+	struct signal_struct *sig = tsk->signal;
+	bool group_dead = thread_group_leader(tsk);
+	struct sighand_struct *sighand;
+	struct tty_struct *uninitialized_var(tty);
+	cputime_t utime, stime;
+
+	sighand = rcu_dereference_check(tsk->sighand,
+					lockdep_tasklist_lock_is_held());
+	spin_lock(&sighand->siglock);
+
+	posix_cpu_timers_exit(tsk);
+	if (group_dead) {
+		posix_cpu_timers_exit_group(tsk);
+		tty = sig->tty;
+		sig->tty = NULL;
+	} else {
+		/*
+		 * This can only happen if the caller is de_thread().
+		 * FIXME: this is the temporary hack, we should teach
+		 * posix-cpu-timers to handle this case correctly.
+		 */
+		if (unlikely(has_group_leader_pid(tsk)))
+			posix_cpu_timers_exit_group(tsk);
+
+		/*
+		 * If there is any task waiting for the group exit
+		 * then notify it:
+		 */
+		if (sig->notify_count > 0 && !--sig->notify_count)
+			wake_up_process(sig->group_exit_task);
+
+		if (tsk == sig->curr_target)
+			sig->curr_target = next_thread(tsk);
+	}
+
+	/*
+	 * Accumulate here the counters for all threads as they die. We could
+	 * skip the group leader because it is the last user of signal_struct,
+	 * but we want to avoid the race with thread_group_cputime() which can
+	 * see the empty ->thread_head list.
+	 */
+	task_cputime(tsk, &utime, &stime);
+	write_seqlock(&sig->stats_lock);
+	sig->utime += utime;
+	sig->stime += stime;
+	sig->gtime += task_gtime(tsk);
+	sig->min_flt += tsk->min_flt;
+	sig->maj_flt += tsk->maj_flt;
+	sig->nvcsw += tsk->nvcsw;
+	sig->nivcsw += tsk->nivcsw;
+	sig->inblock += task_io_get_inblock(tsk);
+	sig->oublock += task_io_get_oublock(tsk);
+	task_io_accounting_add(&sig->ioac, &tsk->ioac);
+	sig->sum_sched_runtime += tsk_seruntime(tsk);
+	sig->nr_threads--;
+	__unhash_process(tsk, group_dead);
+	write_sequnlock(&sig->stats_lock);
+
+	/*
+	 * Do this under ->siglock, we can race with another thread
+	 * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals.
+	 */
+	flush_sigqueue(&tsk->pending);
+	tsk->sighand = NULL;
+	spin_unlock(&sighand->siglock);
+
+	__cleanup_sighand(sighand);
+	clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
+	if (group_dead) {
+		flush_sigqueue(&sig->shared_pending);
+		tty_kref_put(tty);
+	}
+}
+
+static void delayed_put_task_struct(struct rcu_head *rhp)
+{
+	struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
+
+	perf_event_delayed_put(tsk);
+	trace_sched_process_free(tsk);
+	put_task_struct(tsk);
+}
+
+
+void release_task(struct task_struct *p)
+{
+	struct task_struct *leader;
+	int zap_leader;
+repeat:
+	/* don't need to get the RCU readlock here - the process is dead and
+	 * can't be modifying its own credentials. But shut RCU-lockdep up */
+	rcu_read_lock();
+	atomic_dec(&__task_cred(p)->user->processes);
+	rcu_read_unlock();
+
+	proc_flush_task(p);
+
+	write_lock_irq(&tasklist_lock);
+	ptrace_release_task(p);
+	__exit_signal(p);
+
+	/*
+	 * If we are the last non-leader member of the thread
+	 * group, and the leader is zombie, then notify the
+	 * group leader's parent process. (if it wants notification.)
+	 */
+	zap_leader = 0;
+	leader = p->group_leader;
+	if (leader != p && thread_group_empty(leader)
+			&& leader->exit_state == EXIT_ZOMBIE) {
+		/*
+		 * If we were the last child thread and the leader has
+		 * exited already, and the leader's parent ignores SIGCHLD,
+		 * then we are the one who should release the leader.
+		 */
+		zap_leader = do_notify_parent(leader, leader->exit_signal);
+		if (zap_leader)
+			leader->exit_state = EXIT_DEAD;
+	}
+
+	write_unlock_irq(&tasklist_lock);
+	release_thread(p);
+	call_rcu(&p->rcu, delayed_put_task_struct);
+
+	p = leader;
+	if (unlikely(zap_leader))
+		goto repeat;
+}
+
+/*
+ * Determine if a process group is "orphaned", according to the POSIX
+ * definition in 2.2.2.52.  Orphaned process groups are not to be affected
+ * by terminal-generated stop signals.  Newly orphaned process groups are
+ * to receive a SIGHUP and a SIGCONT.
+ *
+ * "I ask you, have you ever known what it is to be an orphan?"
+ */
+static int will_become_orphaned_pgrp(struct pid *pgrp,
+					struct task_struct *ignored_task)
+{
+	struct task_struct *p;
+
+	do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
+		if ((p == ignored_task) ||
+		    (p->exit_state && thread_group_empty(p)) ||
+		    is_global_init(p->real_parent))
+			continue;
+
+		if (task_pgrp(p->real_parent) != pgrp &&
+		    task_session(p->real_parent) == task_session(p))
+			return 0;
+	} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
+
+	return 1;
+}
+
+int is_current_pgrp_orphaned(void)
+{
+	int retval;
+
+	read_lock(&tasklist_lock);
+	retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
+	read_unlock(&tasklist_lock);
+
+	return retval;
+}
+
+static bool has_stopped_jobs(struct pid *pgrp)
+{
+	struct task_struct *p;
+
+	do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
+		if (p->signal->flags & SIGNAL_STOP_STOPPED)
+			return true;
+	} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
+
+	return false;
+}
+
+/*
+ * Check to see if any process groups have become orphaned as
+ * a result of our exiting, and if they have any stopped jobs,
+ * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
+ */
+static void
+kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent)
+{
+	struct pid *pgrp = task_pgrp(tsk);
+	struct task_struct *ignored_task = tsk;
+
+	if (!parent)
+		/* exit: our father is in a different pgrp than
+		 * we are and we were the only connection outside.
+		 */
+		parent = tsk->real_parent;
+	else
+		/* reparent: our child is in a different pgrp than
+		 * we are, and it was the only connection outside.
+		 */
+		ignored_task = NULL;
+
+	if (task_pgrp(parent) != pgrp &&
+	    task_session(parent) == task_session(tsk) &&
+	    will_become_orphaned_pgrp(pgrp, ignored_task) &&
+	    has_stopped_jobs(pgrp)) {
+		__kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
+		__kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
+	}
+}
+
+#ifdef CONFIG_MEMCG
+/*
+ * A task is exiting.   If it owned this mm, find a new owner for the mm.
+ */
+void mm_update_next_owner(struct mm_struct *mm)
+{
+	struct task_struct *c, *g, *p = current;
+
+retry:
+	/*
+	 * If the exiting or execing task is not the owner, it's
+	 * someone else's problem.
+	 */
+	if (mm->owner != p)
+		return;
+	/*
+	 * The current owner is exiting/execing and there are no other
+	 * candidates.  Do not leave the mm pointing to a possibly
+	 * freed task structure.
+	 */
+	if (atomic_read(&mm->mm_users) <= 1) {
+		mm->owner = NULL;
+		return;
+	}
+
+	read_lock(&tasklist_lock);
+	/*
+	 * Search in the children
+	 */
+	list_for_each_entry(c, &p->children, sibling) {
+		if (c->mm == mm)
+			goto assign_new_owner;
+	}
+
+	/*
+	 * Search in the siblings
+	 */
+	list_for_each_entry(c, &p->real_parent->children, sibling) {
+		if (c->mm == mm)
+			goto assign_new_owner;
+	}
+
+	/*
+	 * Search through everything else, we should not get here often.
+	 */
+	for_each_process(g) {
+		if (g->flags & PF_KTHREAD)
+			continue;
+		for_each_thread(g, c) {
+			if (c->mm == mm)
+				goto assign_new_owner;
+			if (c->mm)
+				break;
+		}
+	}
+	read_unlock(&tasklist_lock);
+	/*
+	 * We found no owner yet mm_users > 1: this implies that we are
+	 * most likely racing with swapoff (try_to_unuse()) or /proc or
+	 * ptrace or page migration (get_task_mm()).  Mark owner as NULL.
+	 */
+	mm->owner = NULL;
+	return;
+
+assign_new_owner:
+	BUG_ON(c == p);
+	get_task_struct(c);
+	/*
+	 * The task_lock protects c->mm from changing.
+	 * We always want mm->owner->mm == mm
+	 */
+	task_lock(c);
+	/*
+	 * Delay read_unlock() till we have the task_lock()
+	 * to ensure that c does not slip away underneath us
+	 */
+	read_unlock(&tasklist_lock);
+	if (c->mm != mm) {
+		task_unlock(c);
+		put_task_struct(c);
+		goto retry;
+	}
+	mm->owner = c;
+	task_unlock(c);
+	put_task_struct(c);
+}
+#endif /* CONFIG_MEMCG */
+
+/*
+ * Turn us into a lazy TLB process if we
+ * aren't already..
+ */
+static void exit_mm(struct task_struct *tsk)
+{
+	struct mm_struct *mm = tsk->mm;
+	struct core_state *core_state;
+
+	mm_release(tsk, mm);
+	if (!mm)
+		return;
+	sync_mm_rss(mm);
+	/*
+	 * Serialize with any possible pending coredump.
+	 * We must hold mmap_sem around checking core_state
+	 * and clearing tsk->mm.  The core-inducing thread
+	 * will increment ->nr_threads for each thread in the
+	 * group with ->mm != NULL.
+	 */
+	down_read(&mm->mmap_sem);
+	core_state = mm->core_state;
+	if (core_state) {
+		struct core_thread self;
+
+		up_read(&mm->mmap_sem);
+
+		self.task = tsk;
+		self.next = xchg(&core_state->dumper.next, &self);
+		/*
+		 * Implies mb(), the result of xchg() must be visible
+		 * to core_state->dumper.
+		 */
+		if (atomic_dec_and_test(&core_state->nr_threads))
+			complete(&core_state->startup);
+
+		for (;;) {
+			set_task_state(tsk, TASK_UNINTERRUPTIBLE);
+			if (!self.task) /* see coredump_finish() */
+				break;
+			freezable_schedule();
+		}
+		__set_task_state(tsk, TASK_RUNNING);
+		down_read(&mm->mmap_sem);
+	}
+	atomic_inc(&mm->mm_count);
+	BUG_ON(mm != tsk->active_mm);
+	/* more a memory barrier than a real lock */
+	task_lock(tsk);
+	tsk->mm = NULL;
+	up_read(&mm->mmap_sem);
+	enter_lazy_tlb(mm, current);
+	task_unlock(tsk);
+	mm_update_next_owner(mm);
+	mmput(mm);
+	if (test_thread_flag(TIF_MEMDIE))
+		unmark_oom_victim();
+}
+
+static struct task_struct *find_alive_thread(struct task_struct *p)
+{
+	struct task_struct *t;
+
+	for_each_thread(p, t) {
+		if (!(t->flags & PF_EXITING))
+			return t;
+	}
+	return NULL;
+}
+
+static struct task_struct *find_child_reaper(struct task_struct *father)
+	__releases(&tasklist_lock)
+	__acquires(&tasklist_lock)
+{
+	struct pid_namespace *pid_ns = task_active_pid_ns(father);
+	struct task_struct *reaper = pid_ns->child_reaper;
+
+	if (likely(reaper != father))
+		return reaper;
+
+	reaper = find_alive_thread(father);
+	if (reaper) {
+		pid_ns->child_reaper = reaper;
+		return reaper;
+	}
+
+	write_unlock_irq(&tasklist_lock);
+	if (unlikely(pid_ns == &init_pid_ns)) {
+		panic("Attempted to kill init! exitcode=0x%08x\n",
+			father->signal->group_exit_code ?: father->exit_code);
+	}
+	zap_pid_ns_processes(pid_ns);
+	write_lock_irq(&tasklist_lock);
+
+	return father;
+}
+
+/*
+ * When we die, we re-parent all our children, and try to:
+ * 1. give them to another thread in our thread group, if such a member exists
+ * 2. give it to the first ancestor process which prctl'd itself as a
+ *    child_subreaper for its children (like a service manager)
+ * 3. give it to the init process (PID 1) in our pid namespace
+ */
+static struct task_struct *find_new_reaper(struct task_struct *father,
+					   struct task_struct *child_reaper)
+{
+	struct task_struct *thread, *reaper;
+
+	thread = find_alive_thread(father);
+	if (thread)
+		return thread;
+
+	if (father->signal->has_child_subreaper) {
+		/*
+		 * Find the first ->is_child_subreaper ancestor in our pid_ns.
+		 * We start from father to ensure we can not look into another
+		 * namespace, this is safe because all its threads are dead.
+		 */
+		for (reaper = father;
+		     !same_thread_group(reaper, child_reaper);
+		     reaper = reaper->real_parent) {
+			/* call_usermodehelper() descendants need this check */
+			if (reaper == &init_task)
+				break;
+			if (!reaper->signal->is_child_subreaper)
+				continue;
+			thread = find_alive_thread(reaper);
+			if (thread)
+				return thread;
+		}
+	}
+
+	return child_reaper;
+}
+
+/*
+* Any that need to be release_task'd are put on the @dead list.
+ */
+static void reparent_leader(struct task_struct *father, struct task_struct *p,
+				struct list_head *dead)
+{
+	if (unlikely(p->exit_state == EXIT_DEAD))
+		return;
+
+	/* We don't want people slaying init. */
+	p->exit_signal = SIGCHLD;
+
+	/* If it has exited notify the new parent about this child's death. */
+	if (!p->ptrace &&
+	    p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
+		if (do_notify_parent(p, p->exit_signal)) {
+			p->exit_state = EXIT_DEAD;
+			list_add(&p->ptrace_entry, dead);
+		}
+	}
+
+	kill_orphaned_pgrp(p, father);
+}
+
+/*
+ * This does two things:
+ *
+ * A.  Make init inherit all the child processes
+ * B.  Check to see if any process groups have become orphaned
+ *	as a result of our exiting, and if they have any stopped
+ *	jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
+ */
+static void forget_original_parent(struct task_struct *father,
+					struct list_head *dead)
+{
+	struct task_struct *p, *t, *reaper;
+
+	if (unlikely(!list_empty(&father->ptraced)))
+		exit_ptrace(father, dead);
+
+	/* Can drop and reacquire tasklist_lock */
+	reaper = find_child_reaper(father);
+	if (list_empty(&father->children))
+		return;
+
+	reaper = find_new_reaper(father, reaper);
+	list_for_each_entry(p, &father->children, sibling) {
+		for_each_thread(p, t) {
+			t->real_parent = reaper;
+			BUG_ON((!t->ptrace) != (t->parent == father));
+			if (likely(!t->ptrace))
+				t->parent = t->real_parent;
+			if (t->pdeath_signal)
+				group_send_sig_info(t->pdeath_signal,
+						    SEND_SIG_NOINFO, t);
+		}
+		/*
+		 * If this is a threaded reparent there is no need to
+		 * notify anyone anything has happened.
+		 */
+		if (!same_thread_group(reaper, father))
+			reparent_leader(father, p, dead);
+	}
+	list_splice_tail_init(&father->children, &reaper->children);
+}
+
+/*
+ * Send signals to all our closest relatives so that they know
+ * to properly mourn us..
+ */
+static void exit_notify(struct task_struct *tsk, int group_dead)
+{
+	bool autoreap;
+	struct task_struct *p, *n;
+	LIST_HEAD(dead);
+
+	write_lock_irq(&tasklist_lock);
+	forget_original_parent(tsk, &dead);
+
+	if (group_dead)
+		kill_orphaned_pgrp(tsk->group_leader, NULL);
+
+	if (unlikely(tsk->ptrace)) {
+		int sig = thread_group_leader(tsk) &&
+				thread_group_empty(tsk) &&
+				!ptrace_reparented(tsk) ?
+			tsk->exit_signal : SIGCHLD;
+		autoreap = do_notify_parent(tsk, sig);
+	} else if (thread_group_leader(tsk)) {
+		autoreap = thread_group_empty(tsk) &&
+			do_notify_parent(tsk, tsk->exit_signal);
+	} else {
+		autoreap = true;
+	}
+
+	tsk->exit_state = autoreap ? EXIT_DEAD : EXIT_ZOMBIE;
+	if (tsk->exit_state == EXIT_DEAD)
+		list_add(&tsk->ptrace_entry, &dead);
+
+	/* mt-exec, de_thread() is waiting for group leader */
+	if (unlikely(tsk->signal->notify_count < 0))
+		wake_up_process(tsk->signal->group_exit_task);
+	write_unlock_irq(&tasklist_lock);
+
+	list_for_each_entry_safe(p, n, &dead, ptrace_entry) {
+		list_del_init(&p->ptrace_entry);
+		release_task(p);
+	}
+}
+
+#ifdef CONFIG_DEBUG_STACK_USAGE
+static void check_stack_usage(void)
+{
+	static DEFINE_SPINLOCK(low_water_lock);
+	static int lowest_to_date = THREAD_SIZE;
+	unsigned long free;
+
+	free = stack_not_used(current);
+
+	if (free >= lowest_to_date)
+		return;
+
+	spin_lock(&low_water_lock);
+	if (free < lowest_to_date) {
+		pr_warn("%s (%d) used greatest stack depth: %lu bytes left\n",
+			current->comm, task_pid_nr(current), free);
+		lowest_to_date = free;
+	}
+	spin_unlock(&low_water_lock);
+}
+#else
+static inline void check_stack_usage(void) {}
+#endif
+
+void do_exit(long code)
+{
+	struct task_struct *tsk = current;
+	int group_dead;
+	TASKS_RCU(int tasks_rcu_i);
+
+	profile_task_exit(tsk);
+
+	WARN_ON(blk_needs_flush_plug(tsk));
+
+	if (unlikely(in_interrupt()))
+		panic("Aiee, killing interrupt handler!");
+	if (unlikely(!tsk->pid))
+		panic("Attempted to kill the idle task!");
+
+	/*
+	 * If do_exit is called because this processes oopsed, it's possible
+	 * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before
+	 * continuing. Amongst other possible reasons, this is to prevent
+	 * mm_release()->clear_child_tid() from writing to a user-controlled
+	 * kernel address.
+	 */
+	set_fs(USER_DS);
+
+	ptrace_event(PTRACE_EVENT_EXIT, code);
+
+	validate_creds_for_do_exit(tsk);
+
+	/*
+	 * We're taking recursive faults here in do_exit. Safest is to just
+	 * leave this task alone and wait for reboot.
+	 */
+	if (unlikely(tsk->flags & PF_EXITING)) {
+		pr_alert("Fixing recursive fault but reboot is needed!\n");
+		/*
+		 * We can do this unlocked here. The futex code uses
+		 * this flag just to verify whether the pi state
+		 * cleanup has been done or not. In the worst case it
+		 * loops once more. We pretend that the cleanup was
+		 * done as there is no way to return. Either the
+		 * OWNER_DIED bit is set by now or we push the blocked
+		 * task into the wait for ever nirwana as well.
+		 */
+		tsk->flags |= PF_EXITPIDONE;
+		set_current_state(TASK_UNINTERRUPTIBLE);
+		schedule();
+	}
+
+	exit_signals(tsk);  /* sets PF_EXITING */
+	/*
+	 * tsk->flags are checked in the futex code to protect against
+	 * an exiting task cleaning up the robust pi futexes.
+	 */
+	smp_mb();
+	raw_spin_unlock_wait(&tsk->pi_lock);
+
+	if (unlikely(in_atomic()))
+		pr_info("note: %s[%d] exited with preempt_count %d\n",
+			current->comm, task_pid_nr(current),
+			preempt_count());
+
+	acct_update_integrals(tsk);
+	/* sync mm's RSS info before statistics gathering */
+	if (tsk->mm)
+		sync_mm_rss(tsk->mm);
+	group_dead = atomic_dec_and_test(&tsk->signal->live);
+	if (group_dead) {
+		hrtimer_cancel(&tsk->signal->real_timer);
+		exit_itimers(tsk->signal);
+		if (tsk->mm)
+			setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm);
+	}
+	acct_collect(code, group_dead);
+	if (group_dead)
+		tty_audit_exit();
+	audit_free(tsk);
+
+	tsk->exit_code = code;
+	taskstats_exit(tsk, group_dead);
+
+	exit_mm(tsk);
+
+	if (group_dead)
+		acct_process();
+	trace_sched_process_exit(tsk);
+
+	exit_sem(tsk);
+	exit_shm(tsk);
+	exit_files(tsk);
+	exit_fs(tsk);
+	if (group_dead)
+		disassociate_ctty(1);
+	exit_task_namespaces(tsk);
+	exit_task_work(tsk);
+	exit_thread();
+
+	/*
+	 * Flush inherited counters to the parent - before the parent
+	 * gets woken up by child-exit notifications.
+	 *
+	 * because of cgroup mode, must be called before cgroup_exit()
+	 */
+	perf_event_exit_task(tsk);
+
+	cgroup_exit(tsk);
+
+	/*
+	 * FIXME: do that only when needed, using sched_exit tracepoint
+	 */
+	flush_ptrace_hw_breakpoint(tsk);
+
+	TASKS_RCU(tasks_rcu_i = __srcu_read_lock(&tasks_rcu_exit_srcu));
+	exit_notify(tsk, group_dead);
+	proc_exit_connector(tsk);
+#ifdef CONFIG_NUMA
+	task_lock(tsk);
+	mpol_put(tsk->mempolicy);
+	tsk->mempolicy = NULL;
+	task_unlock(tsk);
+#endif
+#ifdef CONFIG_FUTEX
+	if (unlikely(current->pi_state_cache))
+		kfree(current->pi_state_cache);
+#endif
+	/*
+	 * Make sure we are holding no locks:
+	 */
+	debug_check_no_locks_held();
+	/*
+	 * We can do this unlocked here. The futex code uses this flag
+	 * just to verify whether the pi state cleanup has been done
+	 * or not. In the worst case it loops once more.
+	 */
+	tsk->flags |= PF_EXITPIDONE;
+
+	if (tsk->io_context)
+		exit_io_context(tsk);
+
+	if (tsk->splice_pipe)
+		free_pipe_info(tsk->splice_pipe);
+
+	if (tsk->task_frag.page)
+		put_page(tsk->task_frag.page);
+
+	validate_creds_for_do_exit(tsk);
+
+	check_stack_usage();
+	preempt_disable();
+	if (tsk->nr_dirtied)
+		__this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied);
+	exit_rcu();
+	TASKS_RCU(__srcu_read_unlock(&tasks_rcu_exit_srcu, tasks_rcu_i));
+
+	/*
+	 * The setting of TASK_RUNNING by try_to_wake_up() may be delayed
+	 * when the following two conditions become true.
+	 *   - There is race condition of mmap_sem (It is acquired by
+	 *     exit_mm()), and
+	 *   - SMI occurs before setting TASK_RUNINNG.
+	 *     (or hypervisor of virtual machine switches to other guest)
+	 *  As a result, we may become TASK_RUNNING after becoming TASK_DEAD
+	 *
+	 * To avoid it, we have to wait for releasing tsk->pi_lock which
+	 * is held by try_to_wake_up()
+	 */
+	smp_mb();
+	raw_spin_unlock_wait(&tsk->pi_lock);
+
+	/* causes final put_task_struct in finish_task_switch(). */
+	tsk->state = TASK_DEAD;
+	tsk->flags |= PF_NOFREEZE;	/* tell freezer to ignore us */
+	schedule();
+	BUG();
+	/* Avoid "noreturn function does return".  */
+	for (;;)
+		cpu_relax();	/* For when BUG is null */
+}
+EXPORT_SYMBOL_GPL(do_exit);
+
+void complete_and_exit(struct completion *comp, long code)
+{
+	if (comp)
+		complete(comp);
+
+	do_exit(code);
+}
+EXPORT_SYMBOL(complete_and_exit);
+
+SYSCALL_DEFINE1(exit, int, error_code)
+{
+	do_exit((error_code&0xff)<<8);
+}
+
+/*
+ * Take down every thread in the group.  This is called by fatal signals
+ * as well as by sys_exit_group (below).
+ */
+void
+do_group_exit(int exit_code)
+{
+	struct signal_struct *sig = current->signal;
+
+	BUG_ON(exit_code & 0x80); /* core dumps don't get here */
+
+	if (signal_group_exit(sig))
+		exit_code = sig->group_exit_code;
+	else if (!thread_group_empty(current)) {
+		struct sighand_struct *const sighand = current->sighand;
+
+		spin_lock_irq(&sighand->siglock);
+		if (signal_group_exit(sig))
+			/* Another thread got here before we took the lock.  */
+			exit_code = sig->group_exit_code;
+		else {
+			sig->group_exit_code = exit_code;
+			sig->flags = SIGNAL_GROUP_EXIT;
+			zap_other_threads(current);
+		}
+		spin_unlock_irq(&sighand->siglock);
+	}
+
+	do_exit(exit_code);
+	/* NOTREACHED */
+}
+
+/*
+ * this kills every thread in the thread group. Note that any externally
+ * wait4()-ing process will get the correct exit code - even if this
+ * thread is not the thread group leader.
+ */
+SYSCALL_DEFINE1(exit_group, int, error_code)
+{
+	do_group_exit((error_code & 0xff) << 8);
+	/* NOTREACHED */
+	return 0;
+}
+
+struct wait_opts {
+	enum pid_type		wo_type;
+	int			wo_flags;
+	struct pid		*wo_pid;
+
+	struct siginfo __user	*wo_info;
+	int __user		*wo_stat;
+	struct rusage __user	*wo_rusage;
+
+	wait_queue_t		child_wait;
+	int			notask_error;
+};
+
+static inline
+struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
+{
+	if (type != PIDTYPE_PID)
+		task = task->group_leader;
+	return task->pids[type].pid;
+}
+
+static int eligible_pid(struct wait_opts *wo, struct task_struct *p)
+{
+	return	wo->wo_type == PIDTYPE_MAX ||
+		task_pid_type(p, wo->wo_type) == wo->wo_pid;
+}
+
+static int eligible_child(struct wait_opts *wo, struct task_struct *p)
+{
+	if (!eligible_pid(wo, p))
+		return 0;
+	/* Wait for all children (clone and not) if __WALL is set;
+	 * otherwise, wait for clone children *only* if __WCLONE is
+	 * set; otherwise, wait for non-clone children *only*.  (Note:
+	 * A "clone" child here is one that reports to its parent
+	 * using a signal other than SIGCHLD.) */
+	if (((p->exit_signal != SIGCHLD) ^ !!(wo->wo_flags & __WCLONE))
+	    && !(wo->wo_flags & __WALL))
+		return 0;
+
+	return 1;
+}
+
+static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
+				pid_t pid, uid_t uid, int why, int status)
+{
+	struct siginfo __user *infop;
+	int retval = wo->wo_rusage
+		? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
+
+	put_task_struct(p);
+	infop = wo->wo_info;
+	if (infop) {
+		if (!retval)
+			retval = put_user(SIGCHLD, &infop->si_signo);
+		if (!retval)
+			retval = put_user(0, &infop->si_errno);
+		if (!retval)
+			retval = put_user((short)why, &infop->si_code);
+		if (!retval)
+			retval = put_user(pid, &infop->si_pid);
+		if (!retval)
+			retval = put_user(uid, &infop->si_uid);
+		if (!retval)
+			retval = put_user(status, &infop->si_status);
+	}
+	if (!retval)
+		retval = pid;
+	return retval;
+}
+
+/*
+ * Handle sys_wait4 work for one task in state EXIT_ZOMBIE.  We hold
+ * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
+ * the lock and this task is uninteresting.  If we return nonzero, we have
+ * released the lock and the system call should return.
+ */
+static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
+{
+	int state, retval, status;
+	pid_t pid = task_pid_vnr(p);
+	uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p));
+	struct siginfo __user *infop;
+
+	if (!likely(wo->wo_flags & WEXITED))
+		return 0;
+
+	if (unlikely(wo->wo_flags & WNOWAIT)) {
+		int exit_code = p->exit_code;
+		int why;
+
+		get_task_struct(p);
+		read_unlock(&tasklist_lock);
+		sched_annotate_sleep();
+
+		if ((exit_code & 0x7f) == 0) {
+			why = CLD_EXITED;
+			status = exit_code >> 8;
+		} else {
+			why = (exit_code & 0x80) ? CLD_DUMPED : CLD_KILLED;
+			status = exit_code & 0x7f;
+		}
+		return wait_noreap_copyout(wo, p, pid, uid, why, status);
+	}
+	/*
+	 * Move the task's state to DEAD/TRACE, only one thread can do this.
+	 */
+	state = (ptrace_reparented(p) && thread_group_leader(p)) ?
+		EXIT_TRACE : EXIT_DEAD;
+	if (cmpxchg(&p->exit_state, EXIT_ZOMBIE, state) != EXIT_ZOMBIE)
+		return 0;
+	/*
+	 * We own this thread, nobody else can reap it.
+	 */
+	read_unlock(&tasklist_lock);
+	sched_annotate_sleep();
+
+	/*
+	 * Check thread_group_leader() to exclude the traced sub-threads.
+	 */
+	if (state == EXIT_DEAD && thread_group_leader(p)) {
+		struct signal_struct *sig = p->signal;
+		struct signal_struct *psig = current->signal;
+		unsigned long maxrss;
+		cputime_t tgutime, tgstime;
+
+		/*
+		 * The resource counters for the group leader are in its
+		 * own task_struct.  Those for dead threads in the group
+		 * are in its signal_struct, as are those for the child
+		 * processes it has previously reaped.  All these
+		 * accumulate in the parent's signal_struct c* fields.
+		 *
+		 * We don't bother to take a lock here to protect these
+		 * p->signal fields because the whole thread group is dead
+		 * and nobody can change them.
+		 *
+		 * psig->stats_lock also protects us from our sub-theads
+		 * which can reap other children at the same time. Until
+		 * we change k_getrusage()-like users to rely on this lock
+		 * we have to take ->siglock as well.
+		 *
+		 * We use thread_group_cputime_adjusted() to get times for
+		 * the thread group, which consolidates times for all threads
+		 * in the group including the group leader.
+		 */
+		thread_group_cputime_adjusted(p, &tgutime, &tgstime);
+		spin_lock_irq(&current->sighand->siglock);
+		write_seqlock(&psig->stats_lock);
+		psig->cutime += tgutime + sig->cutime;
+		psig->cstime += tgstime + sig->cstime;
+		psig->cgtime += task_gtime(p) + sig->gtime + sig->cgtime;
+		psig->cmin_flt +=
+			p->min_flt + sig->min_flt + sig->cmin_flt;
+		psig->cmaj_flt +=
+			p->maj_flt + sig->maj_flt + sig->cmaj_flt;
+		psig->cnvcsw +=
+			p->nvcsw + sig->nvcsw + sig->cnvcsw;
+		psig->cnivcsw +=
+			p->nivcsw + sig->nivcsw + sig->cnivcsw;
+		psig->cinblock +=
+			task_io_get_inblock(p) +
+			sig->inblock + sig->cinblock;
+		psig->coublock +=
+			task_io_get_oublock(p) +
+			sig->oublock + sig->coublock;
+		maxrss = max(sig->maxrss, sig->cmaxrss);
+		if (psig->cmaxrss < maxrss)
+			psig->cmaxrss = maxrss;
+		task_io_accounting_add(&psig->ioac, &p->ioac);
+		task_io_accounting_add(&psig->ioac, &sig->ioac);
+		write_sequnlock(&psig->stats_lock);
+		spin_unlock_irq(&current->sighand->siglock);
+	}
+
+	retval = wo->wo_rusage
+		? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
+	status = (p->signal->flags & SIGNAL_GROUP_EXIT)
+		? p->signal->group_exit_code : p->exit_code;
+	if (!retval && wo->wo_stat)
+		retval = put_user(status, wo->wo_stat);
+
+	infop = wo->wo_info;
+	if (!retval && infop)
+		retval = put_user(SIGCHLD, &infop->si_signo);
+	if (!retval && infop)
+		retval = put_user(0, &infop->si_errno);
+	if (!retval && infop) {
+		int why;
+
+		if ((status & 0x7f) == 0) {
+			why = CLD_EXITED;
+			status >>= 8;
+		} else {
+			why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
+			status &= 0x7f;
+		}
+		retval = put_user((short)why, &infop->si_code);
+		if (!retval)
+			retval = put_user(status, &infop->si_status);
+	}
+	if (!retval && infop)
+		retval = put_user(pid, &infop->si_pid);
+	if (!retval && infop)
+		retval = put_user(uid, &infop->si_uid);
+	if (!retval)
+		retval = pid;
+
+	if (state == EXIT_TRACE) {
+		write_lock_irq(&tasklist_lock);
+		/* We dropped tasklist, ptracer could die and untrace */
+		ptrace_unlink(p);
+
+		/* If parent wants a zombie, don't release it now */
+		state = EXIT_ZOMBIE;
+		if (do_notify_parent(p, p->exit_signal))
+			state = EXIT_DEAD;
+		p->exit_state = state;
+		write_unlock_irq(&tasklist_lock);
+	}
+	if (state == EXIT_DEAD)
+		release_task(p);
+
+	return retval;
+}
+
+static int *task_stopped_code(struct task_struct *p, bool ptrace)
+{
+	if (ptrace) {
+		if (task_is_stopped_or_traced(p) &&
+		    !(p->jobctl & JOBCTL_LISTENING))
+			return &p->exit_code;
+	} else {
+		if (p->signal->flags & SIGNAL_STOP_STOPPED)
+			return &p->signal->group_exit_code;
+	}
+	return NULL;
+}
+
+/**
+ * wait_task_stopped - Wait for %TASK_STOPPED or %TASK_TRACED
+ * @wo: wait options
+ * @ptrace: is the wait for ptrace
+ * @p: task to wait for
+ *
+ * Handle sys_wait4() work for %p in state %TASK_STOPPED or %TASK_TRACED.
+ *
+ * CONTEXT:
+ * read_lock(&tasklist_lock), which is released if return value is
+ * non-zero.  Also, grabs and releases @p->sighand->siglock.
+ *
+ * RETURNS:
+ * 0 if wait condition didn't exist and search for other wait conditions
+ * should continue.  Non-zero return, -errno on failure and @p's pid on
+ * success, implies that tasklist_lock is released and wait condition
+ * search should terminate.
+ */
+static int wait_task_stopped(struct wait_opts *wo,
+				int ptrace, struct task_struct *p)
+{
+	struct siginfo __user *infop;
+	int retval, exit_code, *p_code, why;
+	uid_t uid = 0; /* unneeded, required by compiler */
+	pid_t pid;
+
+	/*
+	 * Traditionally we see ptrace'd stopped tasks regardless of options.
+	 */
+	if (!ptrace && !(wo->wo_flags & WUNTRACED))
+		return 0;
+
+	if (!task_stopped_code(p, ptrace))
+		return 0;
+
+	exit_code = 0;
+	spin_lock_irq(&p->sighand->siglock);
+
+	p_code = task_stopped_code(p, ptrace);
+	if (unlikely(!p_code))
+		goto unlock_sig;
+
+	exit_code = *p_code;
+	if (!exit_code)
+		goto unlock_sig;
+
+	if (!unlikely(wo->wo_flags & WNOWAIT))
+		*p_code = 0;
+
+	uid = from_kuid_munged(current_user_ns(), task_uid(p));
+unlock_sig:
+	spin_unlock_irq(&p->sighand->siglock);
+	if (!exit_code)
+		return 0;
+
+	/*
+	 * Now we are pretty sure this task is interesting.
+	 * Make sure it doesn't get reaped out from under us while we
+	 * give up the lock and then examine it below.  We don't want to
+	 * keep holding onto the tasklist_lock while we call getrusage and
+	 * possibly take page faults for user memory.
+	 */
+	get_task_struct(p);
+	pid = task_pid_vnr(p);
+	why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
+	read_unlock(&tasklist_lock);
+	sched_annotate_sleep();
+
+	if (unlikely(wo->wo_flags & WNOWAIT))
+		return wait_noreap_copyout(wo, p, pid, uid, why, exit_code);
+
+	retval = wo->wo_rusage
+		? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
+	if (!retval && wo->wo_stat)
+		retval = put_user((exit_code << 8) | 0x7f, wo->wo_stat);
+
+	infop = wo->wo_info;
+	if (!retval && infop)
+		retval = put_user(SIGCHLD, &infop->si_signo);
+	if (!retval && infop)
+		retval = put_user(0, &infop->si_errno);
+	if (!retval && infop)
+		retval = put_user((short)why, &infop->si_code);
+	if (!retval && infop)
+		retval = put_user(exit_code, &infop->si_status);
+	if (!retval && infop)
+		retval = put_user(pid, &infop->si_pid);
+	if (!retval && infop)
+		retval = put_user(uid, &infop->si_uid);
+	if (!retval)
+		retval = pid;
+	put_task_struct(p);
+
+	BUG_ON(!retval);
+	return retval;
+}
+
+/*
+ * Handle do_wait work for one task in a live, non-stopped state.
+ * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
+ * the lock and this task is uninteresting.  If we return nonzero, we have
+ * released the lock and the system call should return.
+ */
+static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
+{
+	int retval;
+	pid_t pid;
+	uid_t uid;
+
+	if (!unlikely(wo->wo_flags & WCONTINUED))
+		return 0;
+
+	if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
+		return 0;
+
+	spin_lock_irq(&p->sighand->siglock);
+	/* Re-check with the lock held.  */
+	if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
+		spin_unlock_irq(&p->sighand->siglock);
+		return 0;
+	}
+	if (!unlikely(wo->wo_flags & WNOWAIT))
+		p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
+	uid = from_kuid_munged(current_user_ns(), task_uid(p));
+	spin_unlock_irq(&p->sighand->siglock);
+
+	pid = task_pid_vnr(p);
+	get_task_struct(p);
+	read_unlock(&tasklist_lock);
+	sched_annotate_sleep();
+
+	if (!wo->wo_info) {
+		retval = wo->wo_rusage
+			? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
+		put_task_struct(p);
+		if (!retval && wo->wo_stat)
+			retval = put_user(0xffff, wo->wo_stat);
+		if (!retval)
+			retval = pid;
+	} else {
+		retval = wait_noreap_copyout(wo, p, pid, uid,
+					     CLD_CONTINUED, SIGCONT);
+		BUG_ON(retval == 0);
+	}
+
+	return retval;
+}
+
+/*
+ * Consider @p for a wait by @parent.
+ *
+ * -ECHILD should be in ->notask_error before the first call.
+ * Returns nonzero for a final return, when we have unlocked tasklist_lock.
+ * Returns zero if the search for a child should continue;
+ * then ->notask_error is 0 if @p is an eligible child,
+ * or another error from security_task_wait(), or still -ECHILD.
+ */
+static int wait_consider_task(struct wait_opts *wo, int ptrace,
+				struct task_struct *p)
+{
+	/*
+	 * We can race with wait_task_zombie() from another thread.
+	 * Ensure that EXIT_ZOMBIE -> EXIT_DEAD/EXIT_TRACE transition
+	 * can't confuse the checks below.
+	 */
+	int exit_state = ACCESS_ONCE(p->exit_state);
+	int ret;
+
+	if (unlikely(exit_state == EXIT_DEAD))
+		return 0;
+
+	ret = eligible_child(wo, p);
+	if (!ret)
+		return ret;
+
+	ret = security_task_wait(p);
+	if (unlikely(ret < 0)) {
+		/*
+		 * If we have not yet seen any eligible child,
+		 * then let this error code replace -ECHILD.
+		 * A permission error will give the user a clue
+		 * to look for security policy problems, rather
+		 * than for mysterious wait bugs.
+		 */
+		if (wo->notask_error)
+			wo->notask_error = ret;
+		return 0;
+	}
+
+	if (unlikely(exit_state == EXIT_TRACE)) {
+		/*
+		 * ptrace == 0 means we are the natural parent. In this case
+		 * we should clear notask_error, debugger will notify us.
+		 */
+		if (likely(!ptrace))
+			wo->notask_error = 0;
+		return 0;
+	}
+
+	if (likely(!ptrace) && unlikely(p->ptrace)) {
+		/*
+		 * If it is traced by its real parent's group, just pretend
+		 * the caller is ptrace_do_wait() and reap this child if it
+		 * is zombie.
+		 *
+		 * This also hides group stop state from real parent; otherwise
+		 * a single stop can be reported twice as group and ptrace stop.
+		 * If a ptracer wants to distinguish these two events for its
+		 * own children it should create a separate process which takes
+		 * the role of real parent.
+		 */
+		if (!ptrace_reparented(p))
+			ptrace = 1;
+	}
+
+	/* slay zombie? */
+	if (exit_state == EXIT_ZOMBIE) {
+		/* we don't reap group leaders with subthreads */
+		if (!delay_group_leader(p)) {
+			/*
+			 * A zombie ptracee is only visible to its ptracer.
+			 * Notification and reaping will be cascaded to the
+			 * real parent when the ptracer detaches.
+			 */
+			if (unlikely(ptrace) || likely(!p->ptrace))
+				return wait_task_zombie(wo, p);
+		}
+
+		/*
+		 * Allow access to stopped/continued state via zombie by
+		 * falling through.  Clearing of notask_error is complex.
+		 *
+		 * When !@ptrace:
+		 *
+		 * If WEXITED is set, notask_error should naturally be
+		 * cleared.  If not, subset of WSTOPPED|WCONTINUED is set,
+		 * so, if there are live subthreads, there are events to
+		 * wait for.  If all subthreads are dead, it's still safe
+		 * to clear - this function will be called again in finite
+		 * amount time once all the subthreads are released and
+		 * will then return without clearing.
+		 *
+		 * When @ptrace:
+		 *
+		 * Stopped state is per-task and thus can't change once the
+		 * target task dies.  Only continued and exited can happen.
+		 * Clear notask_error if WCONTINUED | WEXITED.
+		 */
+		if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED)))
+			wo->notask_error = 0;
+	} else {
+		/*
+		 * @p is alive and it's gonna stop, continue or exit, so
+		 * there always is something to wait for.
+		 */
+		wo->notask_error = 0;
+	}
+
+	/*
+	 * Wait for stopped.  Depending on @ptrace, different stopped state
+	 * is used and the two don't interact with each other.
+	 */
+	ret = wait_task_stopped(wo, ptrace, p);
+	if (ret)
+		return ret;
+
+	/*
+	 * Wait for continued.  There's only one continued state and the
+	 * ptracer can consume it which can confuse the real parent.  Don't
+	 * use WCONTINUED from ptracer.  You don't need or want it.
+	 */
+	return wait_task_continued(wo, p);
+}
+
+/*
+ * Do the work of do_wait() for one thread in the group, @tsk.
+ *
+ * -ECHILD should be in ->notask_error before the first call.
+ * Returns nonzero for a final return, when we have unlocked tasklist_lock.
+ * Returns zero if the search for a child should continue; then
+ * ->notask_error is 0 if there were any eligible children,
+ * or another error from security_task_wait(), or still -ECHILD.
+ */
+static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk)
+{
+	struct task_struct *p;
+
+	list_for_each_entry(p, &tsk->children, sibling) {
+		int ret = wait_consider_task(wo, 0, p);
+
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk)
+{
+	struct task_struct *p;
+
+	list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
+		int ret = wait_consider_task(wo, 1, p);
+
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int child_wait_callback(wait_queue_t *wait, unsigned mode,
+				int sync, void *key)
+{
+	struct wait_opts *wo = container_of(wait, struct wait_opts,
+						child_wait);
+	struct task_struct *p = key;
+
+	if (!eligible_pid(wo, p))
+		return 0;
+
+	if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent)
+		return 0;
+
+	return default_wake_function(wait, mode, sync, key);
+}
+
+void __wake_up_parent(struct task_struct *p, struct task_struct *parent)
+{
+	__wake_up_sync_key(&parent->signal->wait_chldexit,
+				TASK_INTERRUPTIBLE, 1, p);
+}
+
+static long do_wait(struct wait_opts *wo)
+{
+	struct task_struct *tsk;
+	int retval;
+
+	trace_sched_process_wait(wo->wo_pid);
+
+	init_waitqueue_func_entry(&wo->child_wait, child_wait_callback);
+	wo->child_wait.private = current;
+	add_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
+repeat:
+	/*
+	 * If there is nothing that can match our critiera just get out.
+	 * We will clear ->notask_error to zero if we see any child that
+	 * might later match our criteria, even if we are not able to reap
+	 * it yet.
+	 */
+	wo->notask_error = -ECHILD;
+	if ((wo->wo_type < PIDTYPE_MAX) &&
+	   (!wo->wo_pid || hlist_empty(&wo->wo_pid->tasks[wo->wo_type])))
+		goto notask;
+
+	set_current_state(TASK_INTERRUPTIBLE);
+	read_lock(&tasklist_lock);
+	tsk = current;
+	do {
+		retval = do_wait_thread(wo, tsk);
+		if (retval)
+			goto end;
+
+		retval = ptrace_do_wait(wo, tsk);
+		if (retval)
+			goto end;
+
+		if (wo->wo_flags & __WNOTHREAD)
+			break;
+	} while_each_thread(current, tsk);
+	read_unlock(&tasklist_lock);
+
+notask:
+	retval = wo->notask_error;
+	if (!retval && !(wo->wo_flags & WNOHANG)) {
+		retval = -ERESTARTSYS;
+		if (!signal_pending(current)) {
+			schedule();
+			goto repeat;
+		}
+	}
+end:
+	__set_current_state(TASK_RUNNING);
+	remove_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
+	return retval;
+}
+
+SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
+		infop, int, options, struct rusage __user *, ru)
+{
+	struct wait_opts wo;
+	struct pid *pid = NULL;
+	enum pid_type type;
+	long ret;
+
+	if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED))
+		return -EINVAL;
+	if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
+		return -EINVAL;
+
+	switch (which) {
+	case P_ALL:
+		type = PIDTYPE_MAX;
+		break;
+	case P_PID:
+		type = PIDTYPE_PID;
+		if (upid <= 0)
+			return -EINVAL;
+		break;
+	case P_PGID:
+		type = PIDTYPE_PGID;
+		if (upid <= 0)
+			return -EINVAL;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (type < PIDTYPE_MAX)
+		pid = find_get_pid(upid);
+
+	wo.wo_type	= type;
+	wo.wo_pid	= pid;
+	wo.wo_flags	= options;
+	wo.wo_info	= infop;
+	wo.wo_stat	= NULL;
+	wo.wo_rusage	= ru;
+	ret = do_wait(&wo);
+
+	if (ret > 0) {
+		ret = 0;
+	} else if (infop) {
+		/*
+		 * For a WNOHANG return, clear out all the fields
+		 * we would set so the user can easily tell the
+		 * difference.
+		 */
+		if (!ret)
+			ret = put_user(0, &infop->si_signo);
+		if (!ret)
+			ret = put_user(0, &infop->si_errno);
+		if (!ret)
+			ret = put_user(0, &infop->si_code);
+		if (!ret)
+			ret = put_user(0, &infop->si_pid);
+		if (!ret)
+			ret = put_user(0, &infop->si_uid);
+		if (!ret)
+			ret = put_user(0, &infop->si_status);
+	}
+
+	put_pid(pid);
+	return ret;
+}
+
+SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
+		int, options, struct rusage __user *, ru)
+{
+	struct wait_opts wo;
+	struct pid *pid = NULL;
+	enum pid_type type;
+	long ret;
+
+	if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
+			__WNOTHREAD|__WCLONE|__WALL))
+		return -EINVAL;
+
+	if (upid == -1)
+		type = PIDTYPE_MAX;
+	else if (upid < 0) {
+		type = PIDTYPE_PGID;
+		pid = find_get_pid(-upid);
+	} else if (upid == 0) {
+		type = PIDTYPE_PGID;
+		pid = get_task_pid(current, PIDTYPE_PGID);
+	} else /* upid > 0 */ {
+		type = PIDTYPE_PID;
+		pid = find_get_pid(upid);
+	}
+
+	wo.wo_type	= type;
+	wo.wo_pid	= pid;
+	wo.wo_flags	= options | WEXITED;
+	wo.wo_info	= NULL;
+	wo.wo_stat	= stat_addr;
+	wo.wo_rusage	= ru;
+	ret = do_wait(&wo);
+	put_pid(pid);
+
+	return ret;
+}
+
+#ifdef __ARCH_WANT_SYS_WAITPID
+
+/*
+ * sys_waitpid() remains for compatibility. waitpid() should be
+ * implemented by calling sys_wait4() from libc.a.
+ */
+SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options)
+{
+	return sys_wait4(pid, stat_addr, options, NULL);
+}
+
+#endif