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exit.c

/*
 *  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/mnt_namespace.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/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/freezer.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/compat.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 <asm/uaccess.h>
#include <asm/unistd.h>
#include <asm/pgtable.h>
#include <asm/mmu_context.h>

extern void sem_exit (void);

static void exit_mm(struct task_struct * tsk);

static void __unhash_process(struct task_struct *p)
{
      nr_threads--;
      detach_pid(p, PIDTYPE_PID);
      if (thread_group_leader(p)) {
            detach_pid(p, PIDTYPE_PGID);
            detach_pid(p, PIDTYPE_SID);

            list_del_rcu(&p->tasks);
            __get_cpu_var(process_counts)--;
      }
      list_del_rcu(&p->thread_group);
      remove_parent(p);
}

/*
 * This function expects the tasklist_lock write-locked.
 */
static void __exit_signal(struct task_struct *tsk)
{
      struct signal_struct *sig = tsk->signal;
      struct sighand_struct *sighand;

      BUG_ON(!sig);
      BUG_ON(!atomic_read(&sig->count));

      rcu_read_lock();
      sighand = rcu_dereference(tsk->sighand);
      spin_lock(&sighand->siglock);

      posix_cpu_timers_exit(tsk);
      if (atomic_dec_and_test(&sig->count))
            posix_cpu_timers_exit_group(tsk);
      else {
            /*
             * If there is any task waiting for the group exit
             * then notify it:
             */
            if (sig->group_exit_task && atomic_read(&sig->count) == 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 but the
             * group leader as they die, so they can be added into
             * the process-wide totals when those are taken.
             * The group leader stays around as a zombie as long
             * as there are other threads.  When it gets reaped,
             * the exit.c code will add its counts into these totals.
             * We won't ever get here for the group leader, since it
             * will have been the last reference on the signal_struct.
             */
            sig->utime = cputime_add(sig->utime, tsk->utime);
            sig->stime = cputime_add(sig->stime, tsk->stime);
            sig->gtime = cputime_add(sig->gtime, tsk->gtime);
            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);
            sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
            sig = NULL; /* Marker for below. */
      }

      __unhash_process(tsk);

      tsk->signal = NULL;
      tsk->sighand = NULL;
      spin_unlock(&sighand->siglock);
      rcu_read_unlock();

      __cleanup_sighand(sighand);
      clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
      flush_sigqueue(&tsk->pending);
      if (sig) {
            flush_sigqueue(&sig->shared_pending);
            taskstats_tgid_free(sig);
            __cleanup_signal(sig);
      }
}

static void delayed_put_task_struct(struct rcu_head *rhp)
{
      put_task_struct(container_of(rhp, struct task_struct, rcu));
}

void release_task(struct task_struct * p)
{
      struct task_struct *leader;
      int zap_leader;
repeat:
      atomic_dec(&p->user->processes);
      proc_flush_task(p);
      write_lock_irq(&tasklist_lock);
      ptrace_unlink(p);
      BUG_ON(!list_empty(&p->ptrace_list) || !list_empty(&p->ptrace_children));
      __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) {
            BUG_ON(leader->exit_signal == -1);
            do_notify_parent(leader, leader->exit_signal);
            /*
             * 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.
             *
             * do_notify_parent() will have marked it self-reaping in
             * that case.
             */
            zap_leader = (leader->exit_signal == -1);
      }

      write_unlock_irq(&tasklist_lock);
      release_thread(p);
      call_rcu(&p->rcu, delayed_put_task_struct);

      p = leader;
      if (unlikely(zap_leader))
            goto repeat;
}

/*
 * This checks not only the pgrp, but falls back on the pid if no
 * satisfactory pgrp is found. I dunno - gdb doesn't work correctly
 * without this...
 *
 * The caller must hold rcu lock or the tasklist lock.
 */
struct pid *session_of_pgrp(struct pid *pgrp)
{
      struct task_struct *p;
      struct pid *sid = NULL;

      p = pid_task(pgrp, PIDTYPE_PGID);
      if (p == NULL)
            p = pid_task(pgrp, PIDTYPE_PID);
      if (p != NULL)
            sid = task_session(p);

      return sid;
}

/*
 * 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;
      int ret = 1;

      do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
            if (p == ignored_task
                        || p->exit_state
                        || is_global_init(p->real_parent))
                  continue;
            if (task_pgrp(p->real_parent) != pgrp &&
                task_session(p->real_parent) == task_session(p)) {
                  ret = 0;
                  break;
            }
      } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
      return ret; /* (sighing) "Often!" */
}

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 int has_stopped_jobs(struct pid *pgrp)
{
      int retval = 0;
      struct task_struct *p;

      do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
            if (p->state != TASK_STOPPED)
                  continue;
            retval = 1;
            break;
      } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
      return retval;
}

/**
 * reparent_to_kthreadd - Reparent the calling kernel thread to kthreadd
 *
 * If a kernel thread is launched as a result of a system call, or if
 * it ever exits, it should generally reparent itself to kthreadd so it
 * isn't in the way of other processes and is correctly cleaned up on exit.
 *
 * The various task state such as scheduling policy and priority may have
 * been inherited from a user process, so we reset them to sane values here.
 *
 * NOTE that reparent_to_kthreadd() gives the caller full capabilities.
 */
static void reparent_to_kthreadd(void)
{
      write_lock_irq(&tasklist_lock);

      ptrace_unlink(current);
      /* Reparent to init */
      remove_parent(current);
      current->real_parent = current->parent = kthreadd_task;
      add_parent(current);

      /* Set the exit signal to SIGCHLD so we signal init on exit */
      current->exit_signal = SIGCHLD;

      if (task_nice(current) < 0)
            set_user_nice(current, 0);
      /* cpus_allowed? */
      /* rt_priority? */
      /* signals? */
      security_task_reparent_to_init(current);
      memcpy(current->signal->rlim, init_task.signal->rlim,
             sizeof(current->signal->rlim));
      atomic_inc(&(INIT_USER->__count));
      write_unlock_irq(&tasklist_lock);
      switch_uid(INIT_USER);
}

void __set_special_pids(pid_t session, pid_t pgrp)
{
      struct task_struct *curr = current->group_leader;

      if (task_session_nr(curr) != session) {
            detach_pid(curr, PIDTYPE_SID);
            set_task_session(curr, session);
            attach_pid(curr, PIDTYPE_SID, find_pid(session));
      }
      if (task_pgrp_nr(curr) != pgrp) {
            detach_pid(curr, PIDTYPE_PGID);
            set_task_pgrp(curr, pgrp);
            attach_pid(curr, PIDTYPE_PGID, find_pid(pgrp));
      }
}

static void set_special_pids(pid_t session, pid_t pgrp)
{
      write_lock_irq(&tasklist_lock);
      __set_special_pids(session, pgrp);
      write_unlock_irq(&tasklist_lock);
}

/*
 * Let kernel threads use this to say that they
 * allow a certain signal (since daemonize() will
 * have disabled all of them by default).
 */
int allow_signal(int sig)
{
      if (!valid_signal(sig) || sig < 1)
            return -EINVAL;

      spin_lock_irq(&current->sighand->siglock);
      sigdelset(&current->blocked, sig);
      if (!current->mm) {
            /* Kernel threads handle their own signals.
               Let the signal code know it'll be handled, so
               that they don't get converted to SIGKILL or
               just silently dropped */
            current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2;
      }
      recalc_sigpending();
      spin_unlock_irq(&current->sighand->siglock);
      return 0;
}

EXPORT_SYMBOL(allow_signal);

int disallow_signal(int sig)
{
      if (!valid_signal(sig) || sig < 1)
            return -EINVAL;

      spin_lock_irq(&current->sighand->siglock);
      current->sighand->action[(sig)-1].sa.sa_handler = SIG_IGN;
      recalc_sigpending();
      spin_unlock_irq(&current->sighand->siglock);
      return 0;
}

EXPORT_SYMBOL(disallow_signal);

/*
 *    Put all the gunge required to become a kernel thread without
 *    attached user resources in one place where it belongs.
 */

void daemonize(const char *name, ...)
{
      va_list args;
      struct fs_struct *fs;
      sigset_t blocked;

      va_start(args, name);
      vsnprintf(current->comm, sizeof(current->comm), name, args);
      va_end(args);

      /*
       * If we were started as result of loading a module, close all of the
       * user space pages.  We don't need them, and if we didn't close them
       * they would be locked into memory.
       */
      exit_mm(current);
      /*
       * We don't want to have TIF_FREEZE set if the system-wide hibernation
       * or suspend transition begins right now.
       */
      current->flags |= PF_NOFREEZE;

      set_special_pids(1, 1);
      proc_clear_tty(current);

      /* Block and flush all signals */
      sigfillset(&blocked);
      sigprocmask(SIG_BLOCK, &blocked, NULL);
      flush_signals(current);

      /* Become as one with the init task */

      exit_fs(current); /* current->fs->count--; */
      fs = init_task.fs;
      current->fs = fs;
      atomic_inc(&fs->count);

      if (current->nsproxy != init_task.nsproxy) {
            get_nsproxy(init_task.nsproxy);
            switch_task_namespaces(current, init_task.nsproxy);
      }

      exit_files(current);
      current->files = init_task.files;
      atomic_inc(&current->files->count);

      reparent_to_kthreadd();
}

EXPORT_SYMBOL(daemonize);

static void close_files(struct files_struct * files)
{
      int i, j;
      struct fdtable *fdt;

      j = 0;

      /*
       * It is safe to dereference the fd table without RCU or
       * ->file_lock because this is the last reference to the
       * files structure.
       */
      fdt = files_fdtable(files);
      for (;;) {
            unsigned long set;
            i = j * __NFDBITS;
            if (i >= fdt->max_fds)
                  break;
            set = fdt->open_fds->fds_bits[j++];
            while (set) {
                  if (set & 1) {
                        struct file * file = xchg(&fdt->fd[i], NULL);
                        if (file) {
                              filp_close(file, files);
                              cond_resched();
                        }
                  }
                  i++;
                  set >>= 1;
            }
      }
}

struct files_struct *get_files_struct(struct task_struct *task)
{
      struct files_struct *files;

      task_lock(task);
      files = task->files;
      if (files)
            atomic_inc(&files->count);
      task_unlock(task);

      return files;
}

void fastcall put_files_struct(struct files_struct *files)
{
      struct fdtable *fdt;

      if (atomic_dec_and_test(&files->count)) {
            close_files(files);
            /*
             * Free the fd and fdset arrays if we expanded them.
             * If the fdtable was embedded, pass files for freeing
             * at the end of the RCU grace period. Otherwise,
             * you can free files immediately.
             */
            fdt = files_fdtable(files);
            if (fdt != &files->fdtab)
                  kmem_cache_free(files_cachep, files);
            free_fdtable(fdt);
      }
}

EXPORT_SYMBOL(put_files_struct);

void reset_files_struct(struct task_struct *tsk, struct files_struct *files)
{
      struct files_struct *old;

      old = tsk->files;
      task_lock(tsk);
      tsk->files = files;
      task_unlock(tsk);
      put_files_struct(old);
}
EXPORT_SYMBOL(reset_files_struct);

static void __exit_files(struct task_struct *tsk)
{
      struct files_struct * files = tsk->files;

      if (files) {
            task_lock(tsk);
            tsk->files = NULL;
            task_unlock(tsk);
            put_files_struct(files);
      }
}

void exit_files(struct task_struct *tsk)
{
      __exit_files(tsk);
}

static void __put_fs_struct(struct fs_struct *fs)
{
      /* No need to hold fs->lock if we are killing it */
      if (atomic_dec_and_test(&fs->count)) {
            dput(fs->root);
            mntput(fs->rootmnt);
            dput(fs->pwd);
            mntput(fs->pwdmnt);
            if (fs->altroot) {
                  dput(fs->altroot);
                  mntput(fs->altrootmnt);
            }
            kmem_cache_free(fs_cachep, fs);
      }
}

void put_fs_struct(struct fs_struct *fs)
{
      __put_fs_struct(fs);
}

static void __exit_fs(struct task_struct *tsk)
{
      struct fs_struct * fs = tsk->fs;

      if (fs) {
            task_lock(tsk);
            tsk->fs = NULL;
            task_unlock(tsk);
            __put_fs_struct(fs);
      }
}

void exit_fs(struct task_struct *tsk)
{
      __exit_fs(tsk);
}

EXPORT_SYMBOL_GPL(exit_fs);

/*
 * 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;

      mm_release(tsk, mm);
      if (!mm)
            return;
      /*
       * Serialize with any possible pending coredump.
       * We must hold mmap_sem around checking core_waiters
       * and clearing tsk->mm.  The core-inducing thread
       * will increment core_waiters for each thread in the
       * group with ->mm != NULL.
       */
      down_read(&mm->mmap_sem);
      if (mm->core_waiters) {
            up_read(&mm->mmap_sem);
            down_write(&mm->mmap_sem);
            if (!--mm->core_waiters)
                  complete(mm->core_startup_done);
            up_write(&mm->mmap_sem);

            wait_for_completion(&mm->core_done);
            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);
      /* We don't want this task to be frozen prematurely */
      clear_freeze_flag(tsk);
      task_unlock(tsk);
      mmput(mm);
}

static void
reparent_thread(struct task_struct *p, struct task_struct *father, int traced)
{
      if (p->pdeath_signal)
            /* We already hold the tasklist_lock here.  */
            group_send_sig_info(p->pdeath_signal, SEND_SIG_NOINFO, p);

      /* Move the child from its dying parent to the new one.  */
      if (unlikely(traced)) {
            /* Preserve ptrace links if someone else is tracing this child.  */
            list_del_init(&p->ptrace_list);
            if (p->parent != p->real_parent)
                  list_add(&p->ptrace_list, &p->real_parent->ptrace_children);
      } else {
            /* If this child is being traced, then we're the one tracing it
             * anyway, so let go of it.
             */
            p->ptrace = 0;
            remove_parent(p);
            p->parent = p->real_parent;
            add_parent(p);

            if (p->state == TASK_TRACED) {
                  /*
                   * If it was at a trace stop, turn it into
                   * a normal stop since it's no longer being
                   * traced.
                   */
                  ptrace_untrace(p);
            }
      }

      /* If this is a threaded reparent there is no need to
       * notify anyone anything has happened.
       */
      if (p->real_parent->group_leader == father->group_leader)
            return;

      /* We don't want people slaying init.  */
      if (p->exit_signal != -1)
            p->exit_signal = SIGCHLD;

      /* If we'd notified the old parent about this child's death,
       * also notify the new parent.
       */
      if (!traced && p->exit_state == EXIT_ZOMBIE &&
          p->exit_signal != -1 && thread_group_empty(p))
            do_notify_parent(p, p->exit_signal);

      /*
       * process group orphan check
       * Case ii: Our child is in a different pgrp
       * than we are, and it was the only connection
       * outside, so the child pgrp is now orphaned.
       */
      if ((task_pgrp(p) != task_pgrp(father)) &&
          (task_session(p) == task_session(father))) {
            struct pid *pgrp = task_pgrp(p);

            if (will_become_orphaned_pgrp(pgrp, NULL) &&
                has_stopped_jobs(pgrp)) {
                  __kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
                  __kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
            }
      }
}

/*
 * When we die, we re-parent all our children.
 * Try to give them to another thread in our thread
 * group, and if no such member exists, give it to
 * the child reaper process (ie "init") in our pid
 * space.
 */
static void forget_original_parent(struct task_struct *father)
{
      struct task_struct *p, *n, *reaper = father;
      struct list_head ptrace_dead;

      INIT_LIST_HEAD(&ptrace_dead);

      write_lock_irq(&tasklist_lock);

      do {
            reaper = next_thread(reaper);
            if (reaper == father) {
                  reaper = task_child_reaper(father);
                  break;
            }
      } while (reaper->flags & PF_EXITING);

      /*
       * There are only two places where our children can be:
       *
       * - in our child list
       * - in our ptraced child list
       *
       * Search them and reparent children.
       */
      list_for_each_entry_safe(p, n, &father->children, sibling) {
            int ptrace;

            ptrace = p->ptrace;

            /* if father isn't the real parent, then ptrace must be enabled */
            BUG_ON(father != p->real_parent && !ptrace);

            if (father == p->real_parent) {
                  /* reparent with a reaper, real father it's us */
                  p->real_parent = reaper;
                  reparent_thread(p, father, 0);
            } else {
                  /* reparent ptraced task to its real parent */
                  __ptrace_unlink (p);
                  if (p->exit_state == EXIT_ZOMBIE && p->exit_signal != -1 &&
                      thread_group_empty(p))
                        do_notify_parent(p, p->exit_signal);
            }

            /*
             * if the ptraced child is a zombie with exit_signal == -1
             * we must collect it before we exit, or it will remain
             * zombie forever since we prevented it from self-reap itself
             * while it was being traced by us, to be able to see it in wait4.
             */
            if (unlikely(ptrace && p->exit_state == EXIT_ZOMBIE && p->exit_signal == -1))
                  list_add(&p->ptrace_list, &ptrace_dead);
      }

      list_for_each_entry_safe(p, n, &father->ptrace_children, ptrace_list) {
            p->real_parent = reaper;
            reparent_thread(p, father, 1);
      }

      write_unlock_irq(&tasklist_lock);
      BUG_ON(!list_empty(&father->children));
      BUG_ON(!list_empty(&father->ptrace_children));

      list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_list) {
            list_del_init(&p->ptrace_list);
            release_task(p);
      }

}

/*
 * Send signals to all our closest relatives so that they know
 * to properly mourn us..
 */
static void exit_notify(struct task_struct *tsk)
{
      int state;
      struct task_struct *t;
      struct pid *pgrp;

      if (signal_pending(tsk) && !(tsk->signal->flags & SIGNAL_GROUP_EXIT)
          && !thread_group_empty(tsk)) {
            /*
             * This occurs when there was a race between our exit
             * syscall and a group signal choosing us as the one to
             * wake up.  It could be that we are the only thread
             * alerted to check for pending signals, but another thread
             * should be woken now to take the signal since we will not.
             * Now we'll wake all the threads in the group just to make
             * sure someone gets all the pending signals.
             */
            spin_lock_irq(&tsk->sighand->siglock);
            for (t = next_thread(tsk); t != tsk; t = next_thread(t))
                  if (!signal_pending(t) && !(t->flags & PF_EXITING))
                        recalc_sigpending_and_wake(t);
            spin_unlock_irq(&tsk->sighand->siglock);
      }

      /*
       * 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)
       */
      forget_original_parent(tsk);
      exit_task_namespaces(tsk);

      write_lock_irq(&tasklist_lock);
      /*
       * 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)
       *
       * Case i: Our father is in a different pgrp than we are
       * and we were the only connection outside, so our pgrp
       * is about to become orphaned.
       */
      t = tsk->real_parent;

      pgrp = task_pgrp(tsk);
      if ((task_pgrp(t) != pgrp) &&
          (task_session(t) == task_session(tsk)) &&
          will_become_orphaned_pgrp(pgrp, tsk) &&
          has_stopped_jobs(pgrp)) {
            __kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
            __kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
      }

      /* Let father know we died
       *
       * Thread signals are configurable, but you aren't going to use
       * that to send signals to arbitary processes.
       * That stops right now.
       *
       * If the parent exec id doesn't match the exec id we saved
       * when we started then we know the parent has changed security
       * domain.
       *
       * If our self_exec id doesn't match our parent_exec_id then
       * we have changed execution domain as these two values started
       * the same after a fork.
       */
      if (tsk->exit_signal != SIGCHLD && tsk->exit_signal != -1 &&
          ( tsk->parent_exec_id != t->self_exec_id  ||
            tsk->self_exec_id != tsk->parent_exec_id)
          && !capable(CAP_KILL))
            tsk->exit_signal = SIGCHLD;


      /* If something other than our normal parent is ptracing us, then
       * send it a SIGCHLD instead of honoring exit_signal.  exit_signal
       * only has special meaning to our real parent.
       */
      if (tsk->exit_signal != -1 && thread_group_empty(tsk)) {
            int signal = tsk->parent == tsk->real_parent ? tsk->exit_signal : SIGCHLD;
            do_notify_parent(tsk, signal);
      } else if (tsk->ptrace) {
            do_notify_parent(tsk, SIGCHLD);
      }

      state = EXIT_ZOMBIE;
      if (tsk->exit_signal == -1 && likely(!tsk->ptrace))
            state = EXIT_DEAD;
      tsk->exit_state = state;

      if (thread_group_leader(tsk) &&
          tsk->signal->notify_count < 0 &&
          tsk->signal->group_exit_task)
            wake_up_process(tsk->signal->group_exit_task);

      write_unlock_irq(&tasklist_lock);

      /* If the process is dead, release it - nobody will wait for it */
      if (state == EXIT_DEAD)
            release_task(tsk);
}

#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 *n = end_of_stack(current);
      unsigned long free;

      while (*n == 0)
            n++;
      free = (unsigned long)n - (unsigned long)end_of_stack(current);

      if (free >= lowest_to_date)
            return;

      spin_lock(&low_water_lock);
      if (free < lowest_to_date) {
            printk(KERN_WARNING "%s used greatest stack depth: %lu bytes "
                        "left\n",
                        current->comm, free);
            lowest_to_date = free;
      }
      spin_unlock(&low_water_lock);
}
#else
static inline void check_stack_usage(void) {}
#endif

static inline void exit_child_reaper(struct task_struct *tsk)
{
      if (likely(tsk->group_leader != task_child_reaper(tsk)))
            return;

      if (tsk->nsproxy->pid_ns == &init_pid_ns)
            panic("Attempted to kill init!");

      /*
       * @tsk is the last thread in the 'cgroup-init' and is exiting.
       * Terminate all remaining processes in the namespace and reap them
       * before exiting @tsk.
       *
       * Note that @tsk (last thread of cgroup-init) may not necessarily
       * be the child-reaper (i.e main thread of cgroup-init) of the
       * namespace i.e the child_reaper may have already exited.
       *
       * Even after a child_reaper exits, we let it inherit orphaned children,
       * because, pid_ns->child_reaper remains valid as long as there is
       * at least one living sub-thread in the cgroup init.

       * This living sub-thread of the cgroup-init will be notified when
       * a child inherited by the 'child-reaper' exits (do_notify_parent()
       * uses __group_send_sig_info()). Further, when reaping child processes,
       * do_wait() iterates over children of all living sub threads.

       * i.e even though 'child_reaper' thread is listed as the parent of the
       * orphaned children, any living sub-thread in the cgroup-init can
       * perform the role of the child_reaper.
       */
      zap_pid_ns_processes(tsk->nsproxy->pid_ns);
}

fastcall NORET_TYPE void do_exit(long code)
{
      struct task_struct *tsk = current;
      int group_dead;

      profile_task_exit(tsk);

      WARN_ON(atomic_read(&tsk->fs_excl));

      if (unlikely(in_interrupt()))
            panic("Aiee, killing interrupt handler!");
      if (unlikely(!tsk->pid))
            panic("Attempted to kill the idle task!");

      if (unlikely(current->ptrace & PT_TRACE_EXIT)) {
            current->ptrace_message = code;
            ptrace_notify((PTRACE_EVENT_EXIT << 8) | SIGTRAP);
      }

      /*
       * 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)) {
            printk(KERN_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;
            if (tsk->io_context)
                  exit_io_context();
            set_current_state(TASK_UNINTERRUPTIBLE);
            schedule();
      }

      tsk->flags |= PF_EXITING;
      /*
       * tsk->flags are checked in the futex code to protect against
       * an exiting task cleaning up the robust pi futexes.
       */
      smp_mb();
      spin_unlock_wait(&tsk->pi_lock);

      if (unlikely(in_atomic()))
            printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
                        current->comm, task_pid_nr(current),
                        preempt_count());

      acct_update_integrals(tsk);
      if (tsk->mm) {
            update_hiwater_rss(tsk->mm);
            update_hiwater_vm(tsk->mm);
      }
      group_dead = atomic_dec_and_test(&tsk->signal->live);
      if (group_dead) {
            exit_child_reaper(tsk);
            hrtimer_cancel(&tsk->signal->real_timer);
            exit_itimers(tsk->signal);
      }
      acct_collect(code, group_dead);
#ifdef CONFIG_FUTEX
      if (unlikely(tsk->robust_list))
            exit_robust_list(tsk);
#ifdef CONFIG_COMPAT
      if (unlikely(tsk->compat_robust_list))
            compat_exit_robust_list(tsk);
#endif
#endif
      if (group_dead)
            tty_audit_exit();
      if (unlikely(tsk->audit_context))
            audit_free(tsk);

      tsk->exit_code = code;
      taskstats_exit(tsk, group_dead);

      exit_mm(tsk);

      if (group_dead)
            acct_process();
      exit_sem(tsk);
      __exit_files(tsk);
      __exit_fs(tsk);
      check_stack_usage();
      exit_thread();
      cgroup_exit(tsk, 1);
      exit_keys(tsk);

      if (group_dead && tsk->signal->leader)
            disassociate_ctty(1);

      module_put(task_thread_info(tsk)->exec_domain->module);
      if (tsk->binfmt)
            module_put(tsk->binfmt->module);

      proc_exit_connector(tsk);
      exit_notify(tsk);
#ifdef CONFIG_NUMA
      mpol_free(tsk->mempolicy);
      tsk->mempolicy = NULL;
#endif
#ifdef CONFIG_FUTEX
      /*
       * This must happen late, after the PID is not
       * hashed anymore:
       */
      if (unlikely(!list_empty(&tsk->pi_state_list)))
            exit_pi_state_list(tsk);
      if (unlikely(current->pi_state_cache))
            kfree(current->pi_state_cache);
#endif
      /*
       * Make sure we are holding no locks:
       */
      debug_check_no_locks_held(tsk);
      /*
       * 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();

      if (tsk->splice_pipe)
            __free_pipe_info(tsk->splice_pipe);

      preempt_disable();
      /* causes final put_task_struct in finish_task_switch(). */
      tsk->state = TASK_DEAD;

      schedule();
      BUG();
      /* Avoid "noreturn function does return".  */
      for (;;)
            cpu_relax();      /* For when BUG is null */
}

EXPORT_SYMBOL_GPL(do_exit);

NORET_TYPE void complete_and_exit(struct completion *comp, long code)
{
      if (comp)
            complete(comp);

      do_exit(code);
}

EXPORT_SYMBOL(complete_and_exit);

asmlinkage long sys_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).
 */
NORET_TYPE void
do_group_exit(int exit_code)
{
      BUG_ON(exit_code & 0x80); /* core dumps don't get here */

      if (current->signal->flags & SIGNAL_GROUP_EXIT)
            exit_code = current->signal->group_exit_code;
      else if (!thread_group_empty(current)) {
            struct signal_struct *const sig = current->signal;
            struct sighand_struct *const sighand = current->sighand;
            spin_lock_irq(&sighand->siglock);
            if (sig->flags & SIGNAL_GROUP_EXIT)
                  /* Another thread got here before we took the lock.  */
                  exit_code = sig->group_exit_code;
            else {
                  sig->group_exit_code = exit_code;
                  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.
 */
asmlinkage void sys_exit_group(int error_code)
{
      do_group_exit((error_code & 0xff) << 8);
}

static int eligible_child(pid_t pid, int options, struct task_struct *p)
{
      int err;
      struct pid_namespace *ns;

      ns = current->nsproxy->pid_ns;
      if (pid > 0) {
            if (task_pid_nr_ns(p, ns) != pid)
                  return 0;
      } else if (!pid) {
            if (task_pgrp_nr_ns(p, ns) != task_pgrp_vnr(current))
                  return 0;
      } else if (pid != -1) {
            if (task_pgrp_nr_ns(p, ns) != -pid)
                  return 0;
      }

      /*
       * Do not consider detached threads that are
       * not ptraced:
       */
      if (p->exit_signal == -1 && !p->ptrace)
            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) ^ ((options & __WCLONE) != 0))
          && !(options & __WALL))
            return 0;
      /*
       * Do not consider thread group leaders that are
       * in a non-empty thread group:
       */
      if (delay_group_leader(p))
            return 2;

      err = security_task_wait(p);
      if (err)
            return err;

      return 1;
}

static int wait_noreap_copyout(struct task_struct *p, pid_t pid, uid_t uid,
                         int why, int status,
                         struct siginfo __user *infop,
                         struct rusage __user *rusagep)
{
      int retval = rusagep ? getrusage(p, RUSAGE_BOTH, rusagep) : 0;

      put_task_struct(p);
      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 task_struct *p, int noreap,
                      struct siginfo __user *infop,
                      int __user *stat_addr, struct rusage __user *ru)
{
      unsigned long state;
      int retval, status, traced;
      struct pid_namespace *ns;

      ns = current->nsproxy->pid_ns;

      if (unlikely(noreap)) {
            pid_t pid = task_pid_nr_ns(p, ns);
            uid_t uid = p->uid;
            int exit_code = p->exit_code;
            int why, status;

            if (unlikely(p->exit_state != EXIT_ZOMBIE))
                  return 0;
            if (unlikely(p->exit_signal == -1 && p->ptrace == 0))
                  return 0;
            get_task_struct(p);
            read_unlock(&tasklist_lock);
            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(p, pid, uid, why,
                                 status, infop, ru);
      }

      /*
       * Try to move the task's state to DEAD
       * only one thread is allowed to do this:
       */
      state = xchg(&p->exit_state, EXIT_DEAD);
      if (state != EXIT_ZOMBIE) {
            BUG_ON(state != EXIT_DEAD);
            return 0;
      }

      /* traced means p->ptrace, but not vice versa */
      traced = (p->real_parent != p->parent);

      if (likely(!traced)) {
            struct signal_struct *psig;
            struct signal_struct *sig;

            /*
             * 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 they are only touched by
             * __exit_signal, which runs with tasklist_lock
             * write-locked anyway, and so is excluded here.  We do
             * need to protect the access to p->parent->signal fields,
             * as other threads in the parent group can be right
             * here reaping other children at the same time.
             */
            spin_lock_irq(&p->parent->sighand->siglock);
            psig = p->parent->signal;
            sig = p->signal;
            psig->cutime =
                  cputime_add(psig->cutime,
                  cputime_add(p->utime,
                  cputime_add(sig->utime,
                            sig->cutime)));
            psig->cstime =
                  cputime_add(psig->cstime,
                  cputime_add(p->stime,
                  cputime_add(sig->stime,
                            sig->cstime)));
            psig->cgtime =
                  cputime_add(psig->cgtime,
                  cputime_add(p->gtime,
                  cputime_add(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;
            spin_unlock_irq(&p->parent->sighand->siglock);
      }

      /*
       * Now we are sure this task is interesting, and no other
       * thread can reap it because we set its state to EXIT_DEAD.
       */
      read_unlock(&tasklist_lock);

      retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
      status = (p->signal->flags & SIGNAL_GROUP_EXIT)
            ? p->signal->group_exit_code : p->exit_code;
      if (!retval && stat_addr)
            retval = put_user(status, stat_addr);
      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(task_pid_nr_ns(p, ns), &infop->si_pid);
      if (!retval && infop)
            retval = put_user(p->uid, &infop->si_uid);
      if (!retval)
            retval = task_pid_nr_ns(p, ns);

      if (traced) {
            write_lock_irq(&tasklist_lock);
            /* We dropped tasklist, ptracer could die and untrace */
            ptrace_unlink(p);
            /*
             * If this is not a detached task, notify the parent.
             * If it's still not detached after that, don't release
             * it now.
             */
            if (p->exit_signal != -1) {
                  do_notify_parent(p, p->exit_signal);
                  if (p->exit_signal != -1) {
                        p->exit_state = EXIT_ZOMBIE;
                        p = NULL;
                  }
            }
            write_unlock_irq(&tasklist_lock);
      }
      if (p != NULL)
            release_task(p);

      return retval;
}

/*
 * Handle sys_wait4 work for one task in state TASK_STOPPED.  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_stopped(struct task_struct *p, int delayed_group_leader,
                       int noreap, struct siginfo __user *infop,
                       int __user *stat_addr, struct rusage __user *ru)
{
      int retval, exit_code;
      pid_t pid;

      if (!p->exit_code)
            return 0;
      if (delayed_group_leader && !(p->ptrace & PT_PTRACED) &&
          p->signal->group_stop_count > 0)
            /*
             * A group stop is in progress and this is the group leader.
             * We won't report until all threads have stopped.
             */
            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.
       */
      pid = task_pid_nr_ns(p, current->nsproxy->pid_ns);
      get_task_struct(p);
      read_unlock(&tasklist_lock);

      if (unlikely(noreap)) {
            uid_t uid = p->uid;
            int why = (p->ptrace & PT_PTRACED) ? CLD_TRAPPED : CLD_STOPPED;

            exit_code = p->exit_code;
            if (unlikely(!exit_code) || unlikely(p->exit_state))
                  goto bail_ref;
            return wait_noreap_copyout(p, pid, uid,
                                 why, exit_code,
                                 infop, ru);
      }

      write_lock_irq(&tasklist_lock);

      /*
       * This uses xchg to be atomic with the thread resuming and setting
       * it.  It must also be done with the write lock held to prevent a
       * race with the EXIT_ZOMBIE case.
       */
      exit_code = xchg(&p->exit_code, 0);
      if (unlikely(p->exit_state)) {
            /*
             * The task resumed and then died.  Let the next iteration
             * catch it in EXIT_ZOMBIE.  Note that exit_code might
             * already be zero here if it resumed and did _exit(0).
             * The task itself is dead and won't touch exit_code again;
             * other processors in this function are locked out.
             */
            p->exit_code = exit_code;
            exit_code = 0;
      }
      if (unlikely(exit_code == 0)) {
            /*
             * Another thread in this function got to it first, or it
             * resumed, or it resumed and then died.
             */
            write_unlock_irq(&tasklist_lock);
bail_ref:
            put_task_struct(p);
            /*
             * We are returning to the wait loop without having successfully
             * removed the process and having released the lock. We cannot
             * continue, since the "p" task pointer is potentially stale.
             *
             * Return -EAGAIN, and do_wait() will restart the loop from the
             * beginning. Do _not_ re-acquire the lock.
             */
            return -EAGAIN;
      }

      /* move to end of parent's list to avoid starvation */
      remove_parent(p);
      add_parent(p);

      write_unlock_irq(&tasklist_lock);

      retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
      if (!retval && stat_addr)
            retval = put_user((exit_code << 8) | 0x7f, stat_addr);
      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)((p->ptrace & PT_PTRACED)
                                ? CLD_TRAPPED : CLD_STOPPED),
                          &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(p->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 task_struct *p, int noreap,
                         struct siginfo __user *infop,
                         int __user *stat_addr, struct rusage __user *ru)
{
      int retval;
      pid_t pid;
      uid_t uid;
      struct pid_namespace *ns;

      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 (!noreap)
            p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
      spin_unlock_irq(&p->sighand->siglock);

      ns = current->nsproxy->pid_ns;
      pid = task_pid_nr_ns(p, ns);
      uid = p->uid;
      get_task_struct(p);
      read_unlock(&tasklist_lock);

      if (!infop) {
            retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
            put_task_struct(p);
            if (!retval && stat_addr)
                  retval = put_user(0xffff, stat_addr);
            if (!retval)
                  retval = task_pid_nr_ns(p, ns);
      } else {
            retval = wait_noreap_copyout(p, pid, uid,
                                   CLD_CONTINUED, SIGCONT,
                                   infop, ru);
            BUG_ON(retval == 0);
      }

      return retval;
}


static inline int my_ptrace_child(struct task_struct *p)
{
      if (!(p->ptrace & PT_PTRACED))
            return 0;
      if (!(p->ptrace & PT_ATTACHED))
            return 1;
      /*
       * This child was PTRACE_ATTACH'd.  We should be seeing it only if
       * we are the attacher.  If we are the real parent, this is a race
       * inside ptrace_attach.  It is waiting for the tasklist_lock,
       * which we have to switch the parent links, but has already set
       * the flags in p->ptrace.
       */
      return (p->parent != p->real_parent);
}

static long do_wait(pid_t pid, int options, struct siginfo __user *infop,
                int __user *stat_addr, struct rusage __user *ru)
{
      DECLARE_WAITQUEUE(wait, current);
      struct task_struct *tsk;
      int flag, retval;
      int allowed, denied;

      add_wait_queue(&current->signal->wait_chldexit,&wait);
repeat:
      /*
       * We will set this flag if we see any child that might later
       * match our criteria, even if we are not able to reap it yet.
       */
      flag = 0;
      allowed = denied = 0;
      current->state = TASK_INTERRUPTIBLE;
      read_lock(&tasklist_lock);
      tsk = current;
      do {
            struct task_struct *p;
            int ret;

            list_for_each_entry(p, &tsk->children, sibling) {
                  ret = eligible_child(pid, options, p);
                  if (!ret)
                        continue;

                  if (unlikely(ret < 0)) {
                        denied = ret;
                        continue;
                  }
                  allowed = 1;

                  switch (p->state) {
                  case TASK_TRACED:
                        /*
                         * When we hit the race with PTRACE_ATTACH,
                         * we will not report this child.  But the
                         * race means it has not yet been moved to
                         * our ptrace_children list, so we need to
                         * set the flag here to avoid a spurious ECHILD
                         * when the race happens with the only child.
                         */
                        flag = 1;
                        if (!my_ptrace_child(p))
                              continue;
                        /*FALLTHROUGH*/
                  case TASK_STOPPED:
                        /*
                         * It's stopped now, so it might later
                         * continue, exit, or stop again.
                         */
                        flag = 1;
                        if (!(options & WUNTRACED) &&
                            !my_ptrace_child(p))
                              continue;
                        retval = wait_task_stopped(p, ret == 2,
                                             (options & WNOWAIT),
                                             infop,
                                             stat_addr, ru);
                        if (retval == -EAGAIN)
                              goto repeat;
                        if (retval != 0) /* He released the lock.  */
                              goto end;
                        break;
                  default:
                  // case EXIT_DEAD:
                        if (p->exit_state == EXIT_DEAD)
                              continue;
                  // case EXIT_ZOMBIE:
                        if (p->exit_state == EXIT_ZOMBIE) {
                              /*
                               * Eligible but we cannot release
                               * it yet:
                               */
                              if (ret == 2)
                                    goto check_continued;
                              if (!likely(options & WEXITED))
                                    continue;
                              retval = wait_task_zombie(
                                    p, (options & WNOWAIT),
                                    infop, stat_addr, ru);
                              /* He released the lock.  */
                              if (retval != 0)
                                    goto end;
                              break;
                        }
check_continued:
                        /*
                         * It's running now, so it might later
                         * exit, stop, or stop and then continue.
                         */
                        flag = 1;
                        if (!unlikely(options & WCONTINUED))
                              continue;
                        retval = wait_task_continued(
                              p, (options & WNOWAIT),
                              infop, stat_addr, ru);
                        if (retval != 0) /* He released the lock.  */
                              goto end;
                        break;
                  }
            }
            if (!flag) {
                  list_for_each_entry(p, &tsk->ptrace_children,
                                  ptrace_list) {
                        if (!eligible_child(pid, options, p))
                              continue;
                        flag = 1;
                        break;
                  }
            }
            if (options & __WNOTHREAD)
                  break;
            tsk = next_thread(tsk);
            BUG_ON(tsk->signal != current->signal);
      } while (tsk != current);

      read_unlock(&tasklist_lock);
      if (flag) {
            retval = 0;
            if (options & WNOHANG)
                  goto end;
            retval = -ERESTARTSYS;
            if (signal_pending(current))
                  goto end;
            schedule();
            goto repeat;
      }
      retval = -ECHILD;
      if (unlikely(denied) && !allowed)
            retval = denied;
end:
      current->state = TASK_RUNNING;
      remove_wait_queue(&current->signal->wait_chldexit,&wait);
      if (infop) {
            if (retval > 0)
            retval = 0;
            else {
                  /*
                   * For a WNOHANG return, clear out all the fields
                   * we would set so the user can easily tell the
                   * difference.
                   */
                  if (!retval)
                        retval = put_user(0, &infop->si_signo);
                  if (!retval)
                        retval = put_user(0, &infop->si_errno);
                  if (!retval)
                        retval = put_user(0, &infop->si_code);
                  if (!retval)
                        retval = put_user(0, &infop->si_pid);
                  if (!retval)
                        retval = put_user(0, &infop->si_uid);
                  if (!retval)
                        retval = put_user(0, &infop->si_status);
            }
      }
      return retval;
}

asmlinkage long sys_waitid(int which, pid_t pid,
                     struct siginfo __user *infop, int options,
                     struct rusage __user *ru)
{
      long ret;

      if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED))
            return -EINVAL;
      if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
            return -EINVAL;

      switch (which) {
      case P_ALL:
            pid = -1;
            break;
      case P_PID:
            if (pid <= 0)
                  return -EINVAL;
            break;
      case P_PGID:
            if (pid <= 0)
                  return -EINVAL;
            pid = -pid;
            break;
      default:
            return -EINVAL;
      }

      ret = do_wait(pid, options, infop, NULL, ru);

      /* avoid REGPARM breakage on x86: */
      prevent_tail_call(ret);
      return ret;
}

asmlinkage long sys_wait4(pid_t pid, int __user *stat_addr,
                    int options, struct rusage __user *ru)
{
      long ret;

      if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
                  __WNOTHREAD|__WCLONE|__WALL))
            return -EINVAL;
      ret = do_wait(pid, options | WEXITED, NULL, stat_addr, ru);

      /* avoid REGPARM breakage on x86: */
      prevent_tail_call(ret);
      return ret;
}

#ifdef __ARCH_WANT_SYS_WAITPID

/*
 * sys_waitpid() remains for compatibility. waitpid() should be
 * implemented by calling sys_wait4() from libc.a.
 */
asmlinkage long sys_waitpid(pid_t pid, int __user *stat_addr, int options)
{
      return sys_wait4(pid, stat_addr, options, NULL);
}

#endif

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