handle the multi-threaded init's exit() properly
With or without this patch, multi-threaded init's are not fully supported,
but do_exit() is completely wrong. This becomes a real problem when we
support pid namespaces.
1. do_exit() panics when the main thread of /sbin/init exits. It should not
until the whole thread group exits. Move the code below, under the
"if (group_dead)" check.
Note: this means that forget_original_parent() can use an already dead
child_reaper()'s task_struct. This is OK for /sbin/init because
- do_wait() from alive sub-thread still can reap a zombie, we iterate
over all sub-thread's ->children lists
- do_notify_parent() will wakeup some alive sub-thread because it sends
the group-wide signal
However, we should remove choose_new_parent()->BUG_ON(reaper->exit_state)
for this.
2. We are playing games with ->nsproxy->pid_ns. This code is bogus today, and
it has to be changed anyway when we really support pid namespaces, just
remove it.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Roland McGrath <roland@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Cc: Serge Hallyn <serue@us.ibm.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/exit.c b/kernel/exit.c
index 3b8dfff..8b64c03 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -592,17 +592,6 @@
mmput(mm);
}
-static inline void
-choose_new_parent(struct task_struct *p, struct task_struct *reaper)
-{
- /*
- * Make sure we're not reparenting to ourselves and that
- * the parent is not a zombie.
- */
- BUG_ON(p == reaper || reaper->exit_state);
- p->real_parent = reaper;
-}
-
static void
reparent_thread(struct task_struct *p, struct task_struct *father, int traced)
{
@@ -710,7 +699,7 @@
if (father == p->real_parent) {
/* reparent with a reaper, real father it's us */
- choose_new_parent(p, reaper);
+ p->real_parent = reaper;
reparent_thread(p, father, 0);
} else {
/* reparent ptraced task to its real parent */
@@ -731,7 +720,7 @@
}
list_for_each_safe(_p, _n, &father->ptrace_children) {
p = list_entry(_p, struct task_struct, ptrace_list);
- choose_new_parent(p, reaper);
+ p->real_parent = reaper;
reparent_thread(p, father, 1);
}
}
@@ -882,6 +871,14 @@
static inline void check_stack_usage(void) {}
#endif
+static inline void exit_child_reaper(struct task_struct *tsk)
+{
+ if (likely(tsk->group_leader != child_reaper(tsk)))
+ return;
+
+ panic("Attempted to kill init!");
+}
+
fastcall NORET_TYPE void do_exit(long code)
{
struct task_struct *tsk = current;
@@ -895,13 +892,6 @@
panic("Aiee, killing interrupt handler!");
if (unlikely(!tsk->pid))
panic("Attempted to kill the idle task!");
- if (unlikely(tsk == child_reaper(tsk))) {
- if (tsk->nsproxy->pid_ns != &init_pid_ns)
- tsk->nsproxy->pid_ns->child_reaper = init_pid_ns.child_reaper;
- else
- panic("Attempted to kill init!");
- }
-
if (unlikely(current->ptrace & PT_TRACE_EXIT)) {
current->ptrace_message = code;
@@ -951,6 +941,7 @@
}
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);
}
