[PATCH 23/24] powerpc/mm: Cleanup check for stack expansion

[LEROY Christophe]

Michael Ellerman <mpe at ellerman.id.au> a écrit :

> LEROY Christophe <christophe.leroy at c-s.fr> writes:
>
>> Benjamin Herrenschmidt <benh at kernel.crashing.org> a écrit :
>>
>>> When hitting below a VM_GROWSDOWN vma (typically growing the stack),
>>> we check whether it's a valid stack-growing instruction and we
>>> check the distance to GPR1. This is largely open coded with lots
>>> of comments, so move it out to a helper.
>>
>> Did you have a look at the following patch ? It's been waiting for
>> application for some weeks now.
>> https://patchwork.ozlabs.org/patch/771869
>
> I actually merged it last merge window, but found I had no good way to
> test it, so I took it out again until I can write a test case for it.
>
> The way I realised it wasn't being tested was by removing all the
> store_updates_sp logic entirely and having my system run happily for
> several days :}

Which demonstrates how unlikely this is, hence doing that get_user()  
at every fault is waste of time.

How do you plan to handle that in parralele to ben's serie ?

I'll be back from vacation next week and may help finding a way to  
test that. (A test program using alloca() ?)

Christophe

>
> cheers