From: qianli zhao <zhaoqianligood@gmail.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: christian@brauner.io, axboe@kernel.dk,
"Eric W. Biederman" <ebiederm@xmission.com>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Collingbourne <pcc@google.com>,
linux-kernel@vger.kernel.org, Qianli Zhao <zhaoqianli@xiaomi.com>
Subject: Re: [PATCH V3] exit: trigger panic when global init has exited
Date: Fri, 19 Mar 2021 13:08:55 +0800 [thread overview]
Message-ID: <CAPx_LQENxx0y5mFJjwRT2qMSLt7pbAmF30=eE-QduEwRVJEJ0Q@mail.gmail.com> (raw)
In-Reply-To: <20210318180450.GA9977@redhat.com>
Hi,Oleg
> But then I don't understand the SIGNAL_GROUP_EXIT check added by your
> patch. Do we really need it if we want to avoid zap_pid_ns_processes()
> when the global init exits?
I think check SIGNAL_GROUP_EXIT is necessary,or panic() will happen
after all init sub-threads do_exit(),so the following two situations
will happen:
1.According to the timing in the changelog,
zap_pid_ns_processes()->BUG() maybe happened.
2.The key variables of each init sub-threads will be in the exit
state(such task->mm=NULL,task->flags=PF_EXITING,task->nsproxy=NULL),resulting
in the failure to parse coredump from fulldump.
So i think check SIGNAL_GROUP_EXIT is a simple and effective way to
prevent these
> Does this connect to SIGNAL_GROUP_EXIT check? Do you mean that you want
> to panic earlier, before other init's sub-threads exit?
Yes, my patch just want panic earlier before other init's sub-threads exit
Oleg Nesterov <oleg@redhat.com> 于2021年3月19日周五 上午2:05写道:
>
> On 03/18, qianli zhao wrote:
> >
> > Hi,Oleg
> >
> > Thank you for your reply.
> >
> > >> When init sub-threads running on different CPUs exit at the same time,
> > >> zap_pid_ns_processe()->BUG() may be happened.
> >
> > > and why do you think your patch can't prevent this?
> >
> > > Sorry, I must have missed something. But it seems to me that you are trying
> > > to fix the wrong problem. Yes, zap_pid_ns_processes() must not be called in
> > > the root namespace, and this has nothing to do with CONFIG_PID_NS.
> >
> > Yes, i try to fix this exception by test SIGNAL_GROUP_EXIT and call
> > panic before setting PF_EXITING to prevent zap_pid_ns_processes()
> > being called when init do_exit().
>
> Ah, I didn't notice your patch does atomic_dec_and_test(signal->live)
> before exit_signals() which sets PF_EXITING. Thanks for correcting me.
>
> So yes, I was wrong, your patch can prevent this. Although I'd like to
> recheck if every do-something-if-group-dead action is correct in the
> case we have a non-PF_EXITING thread...
>
> But then I don't understand the SIGNAL_GROUP_EXIT check added by your
> patch. Do we really need it if we want to avoid zap_pid_ns_processes()
> when the global init exits?
>
> > In addition, the patch also protects the init process state to
> > successfully get usable init coredump.
>
> Could you spell please?
>
> Does this connect to SIGNAL_GROUP_EXIT check? Do you mean that you want
> to panic earlier, before other init's sub-threads exit?
>
> Thanks,
>
> Oleg.
>
next prev parent reply other threads:[~2021-03-19 5:10 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-17 12:51 [PATCH V3] exit: trigger panic when global init has exited Qianli Zhao
2021-03-17 14:38 ` Oleg Nesterov
2021-03-18 2:47 ` qianli zhao
2021-03-18 18:04 ` Oleg Nesterov
2021-03-18 19:08 ` Eric W. Biederman
2021-03-19 6:33 ` qianli zhao
2021-03-19 16:34 ` Oleg Nesterov
2021-03-19 16:26 ` Oleg Nesterov
2021-03-21 16:00 ` qianli zhao
2021-03-22 17:07 ` Oleg Nesterov
2021-03-22 17:09 ` Oleg Nesterov
2021-03-19 5:08 ` qianli zhao [this message]
2021-03-19 16:32 ` Oleg Nesterov
2021-03-21 13:04 ` qianli zhao
2021-03-22 16:37 ` Oleg Nesterov
2021-03-23 3:14 ` qianli zhao
2021-03-23 9:00 ` Oleg Nesterov
2021-03-23 11:23 ` qianli zhao
2021-03-24 18:12 ` Oleg Nesterov
2021-03-25 3:00 ` qianli zhao
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