From 84eb646b6eabcd82ec563f30d2d9d40c2054a9c9 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 16 Oct 2007 23:26:49 -0700 Subject: [PATCH] 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 Roland McGrath Cc: "Eric W. Biederman" Cc: Sukadev Bhattiprolu Cc: Serge Hallyn Cc: Cedric Le Goater Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/exit.c | 31 +++++++++++-------------------- 1 file changed, 11 insertions(+), 20 deletions(-) diff --git a/kernel/exit.c b/kernel/exit.c index 3b8dfffd93..8b64c0371a 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -592,17 +592,6 @@ static void exit_mm(struct task_struct * tsk) 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 @@ forget_original_parent(struct task_struct *father, struct list_head *to_release) 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 @@ forget_original_parent(struct task_struct *father, struct list_head *to_release) } 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 void check_stack_usage(void) 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 @@ fastcall NORET_TYPE void do_exit(long code) 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 @@ fastcall NORET_TYPE void do_exit(long code) } 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); } -- 2.39.5