linux-kernel - Re: [PATCH] MIPS: Remove noreturn attribute for die()

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Message-ID: <17bc8aca-6590-02ac-cb03-95d4b5af1d40@loongson.cn>
Date:   Mon, 14 Aug 2023 11:01:30 +0800
From:   Tiezhu Yang <yangtiezhu@...ngson.cn>
To:     "Maciej W. Rozycki" <macro@...am.me.uk>
Cc:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        loongson-kernel@...ts.loongnix.cn
Subject: Re: [PATCH] MIPS: Remove noreturn attribute for die()



On 08/14/2023 05:30 AM, Maciej W. Rozycki wrote:
> On Wed, 9 Aug 2023, Tiezhu Yang wrote:
>
>>>  So you want to keep a task alive that has caused a kernel oops in the
>>> process context in this case, right?  What purpose would it be for and
>>> what condition causes `notify_die' to return NOTIFY_STOP?  IOW why is
>>> there no need to call `make_task_dead' in this case?
>>
>> I did some research, hope it is useful.

...

>>
>>   This requires making die() and die_if_kernel() return a value,
>>   and their callers to honor this (and be prepared that it returns).
>
>  Thanks, that indeed helps, though indirectly.  I think the most relevant,
> though still terse explanation comes from commit 20c0d2d44029 ("[PATCH]
> i386: pass proper trap numbers to die chain handlers"), which I believe is
> the earliest of similar changes.  The patch was originally submitted here:
> <https://lore.kernel.org/r/43DDF02E.76F0.0078.0@novell.com/> and hardly
> any discussion emerged, but I think the key statement is:
>
> "[...] honor the return value from the handler chain invocation in die()
> as, through a debugger, the fault may have been fixed."
>
> Now it makes sense to me: even if ignoring the event will make the system
> unstable, by allowing access through a debugger it has been compromised
> already anyway.
>
>  So I think your change will be good if you update the change description
> to include the justification quoted above rather than just: "the others do
> it too, so it must be good" (though you can of course mention that your
> change also makes our port consistent with other ones).  I suggest linking
> to the original i386 submission too for future reference.

Thank you very much.

>
>  Also I note that you combine three independent changes into one, so
> please split it into individual patches as per our requirements.
>

Will do it in v2.

Thanks,
Tiezhu