blob: d2d7c72f1e81e10fe0bcd847c7d683ad4e4d4483 [file] [log] [blame]
/*
* linux/kernel/exit.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*/
#include <linux/config.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/smp_lock.h>
#include <linux/module.h>
#include <linux/completion.h>
#include <linux/personality.h>
#include <linux/tty.h>
#include <linux/namespace.h>
#include <linux/security.h>
#include <linux/acct.h>
#include <linux/file.h>
#include <linux/binfmts.h>
#include <linux/ptrace.h>
#include <linux/profile.h>
#include <linux/mount.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/mmu_context.h>
extern void sem_exit (void);
extern struct task_struct *child_reaper;
int getrusage(struct task_struct *, int, struct rusage *);
static struct dentry * __unhash_process(struct task_struct *p)
{
struct dentry *proc_dentry;
nr_threads--;
detach_pid(p, PIDTYPE_PID);
detach_pid(p, PIDTYPE_TGID);
if (thread_group_leader(p)) {
detach_pid(p, PIDTYPE_PGID);
detach_pid(p, PIDTYPE_SID);
if (p->pid)
per_cpu(process_counts, smp_processor_id())--;
}
REMOVE_LINKS(p);
proc_dentry = p->proc_dentry;
if (unlikely(proc_dentry != NULL)) {
spin_lock(&dcache_lock);
if (!d_unhashed(proc_dentry)) {
dget_locked(proc_dentry);
__d_drop(proc_dentry);
} else
proc_dentry = NULL;
spin_unlock(&dcache_lock);
}
return proc_dentry;
}
void release_task(struct task_struct * p)
{
struct dentry *proc_dentry;
task_t *leader;
BUG_ON(p->state < TASK_ZOMBIE);
if (p != current)
wait_task_inactive(p);
atomic_dec(&p->user->processes);
security_task_free(p);
free_uid(p->user);
write_lock_irq(&tasklist_lock);
if (unlikely(p->ptrace))
__ptrace_unlink(p);
BUG_ON(!list_empty(&p->ptrace_list) || !list_empty(&p->ptrace_children));
__exit_signal(p);
__exit_sighand(p);
proc_dentry = __unhash_process(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.)
*/
leader = p->group_leader;
if (leader != p && thread_group_empty(leader) &&
leader->state == TASK_ZOMBIE && leader->exit_signal != -1)
do_notify_parent(leader, leader->exit_signal);
p->parent->cutime += p->utime + p->cutime;
p->parent->cstime += p->stime + p->cstime;
p->parent->cmin_flt += p->min_flt + p->cmin_flt;
p->parent->cmaj_flt += p->maj_flt + p->cmaj_flt;
p->parent->cnswap += p->nswap + p->cnswap;
sched_exit(p);
write_unlock_irq(&tasklist_lock);
if (unlikely(proc_dentry != NULL)) {
shrink_dcache_parent(proc_dentry);
dput(proc_dentry);
}
release_thread(p);
put_task_struct(p);
}
/* we are using it only for SMP init */
void unhash_process(struct task_struct *p)
{
struct dentry *proc_dentry;
write_lock_irq(&tasklist_lock);
proc_dentry = __unhash_process(p);
write_unlock_irq(&tasklist_lock);
if (unlikely(proc_dentry != NULL)) {
shrink_dcache_parent(proc_dentry);
dput(proc_dentry);
}
}
/*
* 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...
*/
int session_of_pgrp(int pgrp)
{
struct task_struct *p;
struct list_head *l;
struct pid *pid;
int sid = -1;
read_lock(&tasklist_lock);
for_each_task_pid(pgrp, PIDTYPE_PGID, p, l, pid)
if (p->session > 0) {
sid = p->session;
goto out;
}
p = find_task_by_pid(pgrp);
if (p)
sid = p->session;
out:
read_unlock(&tasklist_lock);
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(int pgrp, task_t *ignored_task)
{
struct task_struct *p;
struct list_head *l;
struct pid *pid;
int ret = 1;
for_each_task_pid(pgrp, PIDTYPE_PGID, p, l, pid) {
if (p == ignored_task
|| p->state >= TASK_ZOMBIE
|| p->real_parent->pid == 1)
continue;
if (p->real_parent->pgrp != pgrp
&& p->real_parent->session == p->session) {
ret = 0;
break;
}
}
return ret; /* (sighing) "Often!" */
}
int is_orphaned_pgrp(int pgrp)
{
int retval;
read_lock(&tasklist_lock);
retval = will_become_orphaned_pgrp(pgrp, NULL);
read_unlock(&tasklist_lock);
return retval;
}
static inline int has_stopped_jobs(int pgrp)
{
int retval = 0;
struct task_struct *p;
struct list_head *l;
struct pid *pid;
for_each_task_pid(pgrp, PIDTYPE_PGID, p, l, pid) {
if (p->state != TASK_STOPPED)
continue;
/* If p is stopped by a debugger on a signal that won't
stop it, then don't count p as stopped. This isn't
perfect but it's a good approximation. */
if (unlikely (p->ptrace)
&& p->exit_code != SIGSTOP
&& p->exit_code != SIGTSTP
&& p->exit_code != SIGTTOU
&& p->exit_code != SIGTTIN)
continue;
retval = 1;
break;
}
return retval;
}
/**
* reparent_to_init() - Reparent the calling kernel thread to the init task.
*
* If a kernel thread is launched as a result of a system call, or if
* it ever exits, it should generally reparent itself to init so that
* it 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_init() gives the caller full capabilities.
*/
void reparent_to_init(void)
{
write_lock_irq(&tasklist_lock);
ptrace_unlink(current);
/* Reparent to init */
REMOVE_LINKS(current);
current->parent = child_reaper;
current->real_parent = child_reaper;
SET_LINKS(current);
/* Set the exit signal to SIGCHLD so we signal init on exit */
current->exit_signal = SIGCHLD;
if ((current->policy == SCHED_NORMAL) && (task_nice(current) < 0))
set_user_nice(current, 0);
/* cpus_allowed? */
/* rt_priority? */
/* signals? */
security_task_reparent_to_init(current);
memcpy(current->rlim, init_task.rlim, sizeof(*(current->rlim)));
switch_uid(INIT_USER);
write_unlock_irq(&tasklist_lock);
}
void __set_special_pids(pid_t session, pid_t pgrp)
{
struct task_struct *curr = current;
if (curr->session != session) {
detach_pid(curr, PIDTYPE_SID);
curr->session = session;
attach_pid(curr, PIDTYPE_SID, session);
}
if (curr->pgrp != pgrp) {
detach_pid(curr, PIDTYPE_PGID);
curr->pgrp = pgrp;
attach_pid(curr, PIDTYPE_PGID, pgrp);
}
}
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 (sig < 1 || sig > _NSIG)
return -EINVAL;
spin_lock_irq(&current->sighand->siglock);
sigdelset(&current->blocked, sig);
recalc_sigpending();
spin_unlock_irq(&current->sighand->siglock);
return 0;
}
EXPORT_SYMBOL(allow_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);
set_special_pids(1, 1);
current->tty = NULL;
/* 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);
exit_files(current);
current->files = init_task.files;
atomic_inc(&current->files->count);
reparent_to_init();
}
static inline void close_files(struct files_struct * files)
{
int i, j;
j = 0;
for (;;) {
unsigned long set;
i = j * __NFDBITS;
if (i >= files->max_fdset || i >= files->max_fds)
break;
set = files->open_fds->fds_bits[j++];
while (set) {
if (set & 1) {
struct file * file = xchg(&files->fd[i], NULL);
if (file)
filp_close(file, files);
}
i++;
set >>= 1;
}
}
}
void put_files_struct(struct files_struct *files)
{
if (atomic_dec_and_test(&files->count)) {
close_files(files);
/*
* Free the fd and fdset arrays if we expanded them.
*/
if (files->fd != &files->fd_array[0])
free_fd_array(files->fd, files->max_fds);
if (files->max_fdset > __FD_SETSIZE) {
free_fdset(files->open_fds, files->max_fdset);
free_fdset(files->close_on_exec, files->max_fdset);
}
kmem_cache_free(files_cachep, files);
}
}
static inline 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 inline 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 inline 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);
}
/*
* We can use these to temporarily drop into
* "lazy TLB" mode and back.
*/
struct mm_struct * start_lazy_tlb(void)
{
struct mm_struct *mm = current->mm;
current->mm = NULL;
/* active_mm is still 'mm' */
atomic_inc(&mm->mm_count);
enter_lazy_tlb(mm, current, smp_processor_id());
return mm;
}
void end_lazy_tlb(struct mm_struct *mm)
{
struct mm_struct *active_mm = current->active_mm;
current->mm = mm;
if (mm != active_mm) {
current->active_mm = mm;
activate_mm(active_mm, mm);
}
mmdrop(active_mm);
}
/*
* Turn us into a lazy TLB process if we
* aren't already..
*/
static inline 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:
*/
if (mm->core_waiters) {
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);
}
atomic_inc(&mm->mm_count);
if (mm != tsk->active_mm) BUG();
/* more a memory barrier than a real lock */
task_lock(tsk);
tsk->mm = NULL;
enter_lazy_tlb(mm, current, smp_processor_id());
task_unlock(tsk);
mmput(mm);
}
void exit_mm(struct task_struct *tsk)
{
__exit_mm(tsk);
}
static inline void choose_new_parent(task_t *p, task_t *reaper, task_t *child_reaper)
{
/*
* Make sure we're not reparenting to ourselves and that
* the parent is not a zombie.
*/
if (p == reaper || reaper->state >= TASK_ZOMBIE)
p->real_parent = child_reaper;
else
p->real_parent = reaper;
if (p->parent == p->real_parent)
BUG();
}
static inline void reparent_thread(task_t *p, task_t *father, int traced)
{
/* We dont want people slaying init. */
if (p->exit_signal != -1)
p->exit_signal = SIGCHLD;
p->self_exec_id++;
if (p->pdeath_signal)
send_sig(p->pdeath_signal, p, 0);
/* 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;
list_del_init(&p->sibling);
p->parent = p->real_parent;
list_add_tail(&p->sibling, &p->parent->children);
/* If we'd notified the old parent about this child's death,
* also notify the new parent.
*/
if (p->state == TASK_ZOMBIE && p->exit_signal != -1)
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 ((p->pgrp != father->pgrp) &&
(p->session == father->session)) {
int pgrp = p->pgrp;
if (will_become_orphaned_pgrp(pgrp, NULL) && has_stopped_jobs(pgrp)) {
__kill_pg_info(SIGHUP, (void *)1, pgrp);
__kill_pg_info(SIGCONT, (void *)1, 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 global child reaper process (ie "init")
*/
static inline void forget_original_parent(struct task_struct * father)
{
struct task_struct *p, *reaper = father;
struct list_head *_p, *_n;
reaper = father->group_leader;
if (reaper == father)
reaper = child_reaper;
/*
* 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_safe(_p, _n, &father->children) {
p = list_entry(_p,struct task_struct,sibling);
if (father == p->real_parent) {
choose_new_parent(p, reaper, child_reaper);
reparent_thread(p, father, 0);
} else {
ptrace_unlink (p);
if (p->state == TASK_ZOMBIE && p->exit_signal != -1)
do_notify_parent(p, p->exit_signal);
}
}
list_for_each_safe(_p, _n, &father->ptrace_children) {
p = list_entry(_p,struct task_struct,ptrace_list);
choose_new_parent(p, reaper, child_reaper);
reparent_thread(p, father, 1);
}
}
/*
* Send signals to all our closest relatives so that they know
* to properly mourn us..
*/
static void exit_notify(struct task_struct *tsk)
{
struct task_struct *t;
if (signal_pending(tsk) && !tsk->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.
*/
read_lock(&tasklist_lock);
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_tsk(t);
if (signal_pending(t))
signal_wake_up(t, 0);
}
spin_unlock_irq(&tsk->sighand->siglock);
read_unlock(&tasklist_lock);
}
write_lock_irq(&tasklist_lock);
/*
* 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);
BUG_ON(!list_empty(&tsk->children));
/*
* 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;
if ((t->pgrp != tsk->pgrp) &&
(t->session == tsk->session) &&
will_become_orphaned_pgrp(tsk->pgrp, tsk) &&
has_stopped_jobs(tsk->pgrp)) {
__kill_pg_info(SIGHUP, (void *)1, tsk->pgrp);
__kill_pg_info(SIGCONT, (void *)1, tsk->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) {
int signal = tsk->parent == tsk->real_parent ? tsk->exit_signal : SIGCHLD;
do_notify_parent(tsk, signal);
}
tsk->state = TASK_ZOMBIE;
/*
* No need to unlock IRQs, we'll schedule() immediately
* anyway. In the preemption case this also makes it
* impossible for the task to get runnable again (thus
* the "_raw_" unlock - to make sure we don't try to
* preempt here).
*/
_raw_write_unlock(&tasklist_lock);
}
NORET_TYPE void do_exit(long code)
{
struct task_struct *tsk = current;
if (unlikely(in_interrupt()))
panic("Aiee, killing interrupt handler!");
if (unlikely(!tsk->pid))
panic("Attempted to kill the idle task!");
if (unlikely(tsk->pid == 1))
panic("Attempted to kill init!");
tsk->flags |= PF_EXITING;
del_timer_sync(&tsk->real_timer);
if (unlikely(in_atomic()))
printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
current->comm, current->pid,
preempt_count());
profile_exit_task(tsk);
if (unlikely(current->ptrace & PT_TRACE_EXIT)) {
current->ptrace_message = code;
ptrace_notify((PTRACE_EVENT_EXIT << 8) | SIGTRAP);
}
acct_process(code);
__exit_mm(tsk);
sem_exit();
__exit_files(tsk);
__exit_fs(tsk);
exit_namespace(tsk);
exit_thread();
if (tsk->leader)
disassociate_ctty(1);
module_put(tsk->thread_info->exec_domain->module);
if (tsk->binfmt)
module_put(tsk->binfmt->module);
tsk->exit_code = code;
exit_notify(tsk);
preempt_disable();
if (tsk->exit_signal == -1)
release_task(tsk);
schedule();
BUG();
/* Avoid "noreturn function does return". */
for (;;) ;
}
NORET_TYPE void complete_and_exit(struct completion *comp, long code)
{
if (comp)
complete(comp);
do_exit(code);
}
asmlinkage long sys_exit(int error_code)
{
do_exit((error_code&0xff)<<8);
}
task_t *next_thread(task_t *p)
{
struct pid_link *link = p->pids + PIDTYPE_TGID;
struct list_head *tmp, *head = &link->pidptr->task_list;
#if CONFIG_SMP
if (!p->sighand)
BUG();
if (!spin_is_locked(&p->sighand->siglock) &&
!rwlock_is_locked(&tasklist_lock))
BUG();
#endif
tmp = link->pid_chain.next;
if (tmp == head)
tmp = head->next;
return pid_task(tmp, PIDTYPE_TGID);
}
/*
* 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->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;
read_lock(&tasklist_lock);
spin_lock_irq(&sighand->siglock);
if (sig->group_exit)
/* Another thread got here before we took the lock. */
exit_code = sig->group_exit_code;
else {
sig->group_exit = 1;
sig->group_exit_code = exit_code;
zap_other_threads(current);
}
spin_unlock_irq(&sighand->siglock);
read_unlock(&tasklist_lock);
}
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, task_t *p)
{
if (pid > 0) {
if (p->pid != pid)
return 0;
} else if (!pid) {
if (p->pgrp != current->pgrp)
return 0;
} else if (pid != -1) {
if (p->pgrp != -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 (current->tgid != p->tgid && delay_group_leader(p))
return 2;
if (security_task_wait(p))
return 0;
return 1;
}
/*
* Handle sys_wait4 work for one task in state TASK_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(task_t *p, unsigned int *stat_addr, struct rusage *ru)
{
unsigned long state;
int retval;
/*
* Try to move the task's state to DEAD
* only one thread is allowed to do this:
*/
state = xchg(&p->state, TASK_DEAD);
if (state != TASK_ZOMBIE) {
BUG_ON(state != TASK_DEAD);
return 0;
}
if (unlikely(p->exit_signal == -1))
/*
* This can only happen in a race with a ptraced thread
* dying on another processor.
*/
return 0;
/*
* Now we are sure this task is interesting, and no other
* thread can reap it because we set its state to TASK_DEAD.
*/
read_unlock(&tasklist_lock);
retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
if (!retval && stat_addr) {
if (p->signal->group_exit)
retval = put_user(p->signal->group_exit_code, stat_addr);
else
retval = put_user(p->exit_code, stat_addr);
}
if (retval) {
p->state = TASK_ZOMBIE;
return retval;
}
retval = p->pid;
if (p->real_parent != p->parent) {
write_lock_irq(&tasklist_lock);
/* Double-check with lock held. */
if (p->real_parent != p->parent) {
__ptrace_unlink(p);
do_notify_parent(p, p->exit_signal);
p->state = TASK_ZOMBIE;
p = NULL;
}
write_unlock_irq(&tasklist_lock);
}
if (p != NULL)
release_task(p);
BUG_ON(!retval);
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(task_t *p, int delayed_group_leader,
unsigned int *stat_addr, struct rusage *ru)
{
int retval, exit_code;
if (!p->exit_code)
return 0;
if (delayed_group_leader && !(p->ptrace & PT_PTRACED) &&
p->signal && 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.
*/
get_task_struct(p);
read_unlock(&tasklist_lock);
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 TASK_ZOMBIE case.
*/
exit_code = xchg(&p->exit_code, 0);
if (unlikely(p->state > TASK_STOPPED)) {
/*
* The task resumed and then died. Let the next iteration
* catch it in TASK_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);
put_task_struct(p);
read_lock(&tasklist_lock);
return 0;
}
/* move to end of parent's list to avoid starvation */
remove_parent(p);
add_parent(p, p->parent);
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)
retval = p->pid;
put_task_struct(p);
BUG_ON(!retval);
return retval;
}
asmlinkage long sys_wait4(pid_t pid,unsigned int * stat_addr, int options, struct rusage * ru)
{
DECLARE_WAITQUEUE(wait, current);
struct task_struct *tsk;
int flag, retval;
if (options & ~(WNOHANG|WUNTRACED|__WNOTHREAD|__WCLONE|__WALL))
return -EINVAL;
add_wait_queue(&current->wait_chldexit,&wait);
repeat:
flag = 0;
current->state = TASK_INTERRUPTIBLE;
read_lock(&tasklist_lock);
tsk = current;
do {
struct task_struct *p;
struct list_head *_p;
int ret;
list_for_each(_p,&tsk->children) {
p = list_entry(_p,struct task_struct,sibling);
ret = eligible_child(pid, options, p);
if (!ret)
continue;
flag = 1;
switch (p->state) {
case TASK_STOPPED:
if (!(options & WUNTRACED) &&
!(p->ptrace & PT_PTRACED))
continue;
retval = wait_task_stopped(p, ret == 2,
stat_addr, ru);
if (retval != 0) /* He released the lock. */
goto end_wait4;
break;
case TASK_ZOMBIE:
/*
* Eligible but we cannot release it yet:
*/
if (ret == 2)
continue;
retval = wait_task_zombie(p, stat_addr, ru);
if (retval != 0) /* He released the lock. */
goto end_wait4;
break;
}
}
if (!flag) {
list_for_each (_p,&tsk->ptrace_children) {
p = list_entry(_p,struct task_struct,ptrace_list);
if (!eligible_child(pid, options, p))
continue;
flag = 1;
break;
}
}
if (options & __WNOTHREAD)
break;
tsk = next_thread(tsk);
if (tsk->signal != current->signal)
BUG();
} while (tsk != current);
read_unlock(&tasklist_lock);
if (flag) {
retval = 0;
if (options & WNOHANG)
goto end_wait4;
retval = -ERESTARTSYS;
if (signal_pending(current))
goto end_wait4;
schedule();
goto repeat;
}
retval = -ECHILD;
end_wait4:
current->state = TASK_RUNNING;
remove_wait_queue(&current->wait_chldexit,&wait);
return retval;
}
#if !defined(__alpha__) && !defined(__ia64__) && !defined(__arm__)
/*
* sys_waitpid() remains for compatibility. waitpid() should be
* implemented by calling sys_wait4() from libc.a.
*/
asmlinkage long sys_waitpid(pid_t pid,unsigned int * stat_addr, int options)
{
return sys_wait4(pid, stat_addr, options, NULL);
}
#endif