[PATCH] powerpc/xmon: add debugfs entry for xmon

[Michael Ellerman]

Pan Xinhui <xinhui at linux.vnet.ibm.com> writes:
> 在 2017/2/14 10:35, Nicholas Piggin 写道:
>> On Mon, 13 Feb 2017 19:00:42 -0200
>> "Guilherme G. Piccoli" <gpiccoli at linux.vnet.ibm.com> wrote:
>>> * I had this patch partially done for some time, and after a discussion
>>> at the kernel slack channel latest week, I decided to rebase and fix
>>> some remaining bugs. I'd change 'x' option to always disable the debugger,
>>> since with this patch we can always re-enable xmon, but today I noticed
>>> Pan's patch on the mailing list, so perhaps his approach of adding a flag
>>> to 'x' option is preferable. I can change this in a V2, if requested.
>>> Thanks in advance!
>>
>> xmon state changing after the first sysrq+x violates principle of least
>> astonishment, so I think that should be fixed.
>
> Hi, Guilherme
> So in the end, my thought is that:
> 1) cmd x|X will exit xmon and keep xmon in the original state

Agreed.

> 2) Then add options to turn some features on/off. And debugfs maybe
> not fit for this. But I am also wondering at same time, are people
> needing this?

I think it's useful. Especially seeing as Guilherme has already written
the code.

And yeah I think debugfs is the right place to do it. It means you can
query and/or set the xmon state without crashing the box - which is what
entering xmon essentially does, even if you later recover.

cheers