From: qianli zhao <zhaoqianligood@gmail.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@redhat.com>,
christian@brauner.io, axboe@kernel.dk,
Thomas Gleixner <tglx@linutronix.de>,
Peter Collingbourne <pcc@google.com>,
linux-kernel@vger.kernel.org, Qianli Zhao <zhaoqianli@xiaomi.com>
Subject: Re: [PATCH] exit: trigger panic when init process is set to SIGNAL_GROUP_EXIT
Date: Thu, 11 Mar 2021 12:40:49 +0800 [thread overview]
Message-ID: <CAPx_LQF90joRVLCjR9M44uZ0829Ktw3GAFStdOWEBANGLfDvdQ@mail.gmail.com> (raw)
In-Reply-To: <m1lfavufep.fsf@fess.ebiederm.org>
Hi, Eric
Thank you for your suggestion
> At the start of your changelog and your patch subject you describe what
> you are doing but not why. For the next revision of the patch please
> lead with the why it makes what you are trying to do much easier to
> understand.
got it.
>
> It does not work to use SIGNAL_UNKILLABLE for this. Normally init
> has SIGNAL_UNKILLABLE set. The only case that clears SIGNAL_UNKILLABLE
> is force_sig_info_to_task. If the init process exits with exit(2)
> SIGNAL_UNKILLABLE will already be set. Which means testing
> SIGNAL_UNKILLABLE as your patch does will prevent the panic.
>
Ok,using SIGNAL_UNKILLABLE is incorrect.
> Further simply calling panic is sufficient to guarantee that the other
> threads don't exit, and that whichever thread calls panic first
> will be the reporting thread. The rest of the threads will be caught
> in panic_smp_self_stop(), if they happen to be running on other cpus.
>
> So I would make the whole thing just be:
>
> /* If global init has exited,
> * panic immediately to get a useable coredump.
> */
> if (unlikely(is_global_init(tsk) &&
> (thread_group_empty(tsk) ||
> (tsk->signal->flags & SIGNAL_GROUP_EXIT)))) {
> panic("Attempted to kill init! exitcode=0x%08x\n",
> tsk->signal->group_exit_code ?: (int)code);
> }
>
> The thread_group_empty test is needed to handle single threaded
> inits.
>
> Do you think you can respin your patch as something like that?
>
Ok.it's a very good change,other CPUs calls to panic() will be caught
and execute panic_smp_self_stop(),
there is no need to deal with this situation separately when other CPUs exit().
prev parent reply other threads:[~2021-03-11 4:42 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-09 13:31 [PATCH] exit: trigger panic when init process is set to SIGNAL_GROUP_EXIT Qianli Zhao
2021-03-09 18:26 ` Oleg Nesterov
2021-03-10 3:59 ` qianli zhao
2021-03-10 16:44 ` Eric W. Biederman
2021-03-10 17:32 ` Oleg Nesterov
2021-03-10 19:07 ` Eric W. Biederman
2021-03-10 22:13 ` Eric W. Biederman
2021-03-11 4:40 ` qianli zhao [this message]
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