linux-kernel - Re: [PATCH v3] kernel/exit: do panic earlier to get coredump if global init task exit

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Date:   Fri, 20 Dec 2019 20:38:00 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     qiwuchen55@...il.com
Cc:     christian.brauner@...ntu.com, peterz@...radead.org,
        mingo@...nel.org, prsood@...eaurora.org, kernel-team@...roid.com,
        linux-kernel@...r.kernel.org, chenqiwu@...omi.com
Subject: Re: [PATCH v3] kernel/exit: do panic earlier to get coredump if
 global init task exit

On 12/19, qiwuchen55@...il.com wrote:
>
> @@ -517,10 +517,6 @@ static struct task_struct *find_child_reaper(struct task_struct *father,
>  	}
>  
>  	write_unlock_irq(&tasklist_lock);
> -	if (unlikely(pid_ns == &init_pid_ns)) {
> -		panic("Attempted to kill init! exitcode=0x%08x\n",
> -			father->signal->group_exit_code ?: father->exit_code);
> -	}
>  
>  	list_for_each_entry_safe(p, n, dead, ptrace_entry) {
>  		list_del_init(&p->ptrace_entry);
> @@ -766,6 +762,15 @@ void __noreturn do_exit(long code)
>  	acct_update_integrals(tsk);
>  	group_dead = atomic_dec_and_test(&tsk->signal->live);
>  	if (group_dead) {
> +		/*
> +		 * If the last thread of global init exit, do panic
> +		 * immeddiately to get the coredump to find any clue
> +		 * for init task in userspace.
> +		 */
> +		if (unlikely(is_global_init(tsk)))
> +			panic("Attempted to kill init! exitcode=0x%08x\n",
> +				tsk->signal->group_exit_code ?: (int)code);
> +

Acked-by: Oleg Nesterov <oleg@...hat.com>