linux-kernel - Re: [PATCH V3] exit: trigger panic when global init has exited

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Date:   Wed, 24 Mar 2021 19:12:10 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     qianli zhao <zhaoqianligood@...il.com>
Cc:     christian@...uner.io, axboe@...nel.dk,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Collingbourne <pcc@...gle.com>,
        linux-kernel@...r.kernel.org, Qianli Zhao <zhaoqianli@...omi.com>
Subject: Re: [PATCH V3] exit: trigger panic when global init has exited

Hi,

On 03/23, qianli zhao wrote:
>
> Hi,Oleg
>
> > You certainly don't understand me :/
>
> > Please read my email you quoted below. I didn't mean the current logic.
> > I meant the logic after your patch which moves atomic_dec_and_test() and
> > panic() before exit_signals().
>
> Sorry, I think I see what you mean now.
>
> You mean that after apply my patch,SIGNAL_GROUP_EXIT no longer needs
> to be tested or avoid zap_pid_ns_processes()->BUG().
> Yes,your consideration is correct.

OK, great

> But,my patch has another purpose,protect some key variables(such
> as:task->mm,task->nsproxy,etc) to recover init coredump from
> fulldump,if sub-threads finish do_exit(),

Yes I know.

But the purpose of this SIGNAL_GROUP_EXIT check is not clear and not
documented. That is why I said it should be documented at least in the
changelog.

Oleg.