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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>
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@ -592,17 +592,6 @@ static void exit_mm(struct task_struct * tsk)
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mmput(mm);
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}
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static inline void
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choose_new_parent(struct task_struct *p, struct task_struct *reaper)
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{
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/*
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* Make sure we're not reparenting to ourselves and that
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* the parent is not a zombie.
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*/
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BUG_ON(p == reaper || reaper->exit_state);
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p->real_parent = reaper;
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}
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static void
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reparent_thread(struct task_struct *p, struct task_struct *father, int traced)
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{
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@ -710,7 +699,7 @@ forget_original_parent(struct task_struct *father, struct list_head *to_release)
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if (father == p->real_parent) {
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/* reparent with a reaper, real father it's us */
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choose_new_parent(p, reaper);
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p->real_parent = reaper;
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reparent_thread(p, father, 0);
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} else {
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/* reparent ptraced task to its real parent */
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@ -731,7 +720,7 @@ forget_original_parent(struct task_struct *father, struct list_head *to_release)
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}
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list_for_each_safe(_p, _n, &father->ptrace_children) {
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p = list_entry(_p, struct task_struct, ptrace_list);
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choose_new_parent(p, reaper);
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p->real_parent = reaper;
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reparent_thread(p, father, 1);
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}
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}
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@ -882,6 +871,14 @@ static void check_stack_usage(void)
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static inline void check_stack_usage(void) {}
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#endif
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static inline void exit_child_reaper(struct task_struct *tsk)
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{
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if (likely(tsk->group_leader != child_reaper(tsk)))
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return;
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panic("Attempted to kill init!");
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}
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fastcall NORET_TYPE void do_exit(long code)
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{
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struct task_struct *tsk = current;
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@ -895,13 +892,6 @@ fastcall NORET_TYPE void do_exit(long code)
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panic("Aiee, killing interrupt handler!");
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if (unlikely(!tsk->pid))
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panic("Attempted to kill the idle task!");
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if (unlikely(tsk == child_reaper(tsk))) {
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if (tsk->nsproxy->pid_ns != &init_pid_ns)
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tsk->nsproxy->pid_ns->child_reaper = init_pid_ns.child_reaper;
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else
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panic("Attempted to kill init!");
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}
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if (unlikely(current->ptrace & PT_TRACE_EXIT)) {
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current->ptrace_message = code;
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@ -951,6 +941,7 @@ fastcall NORET_TYPE void do_exit(long code)
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}
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group_dead = atomic_dec_and_test(&tsk->signal->live);
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if (group_dead) {
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exit_child_reaper(tsk);
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hrtimer_cancel(&tsk->signal->real_timer);
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exit_itimers(tsk->signal);
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}
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