Re: [PATCH] Add a text_poke syscall v2

H. Peter Anvin
2013-11-29T21:24:57Z

On 11/29/2013 12:35 PM, Oleg Nesterov wrote:
> On 11/29, H. Peter Anvin wrote:
>>
>> On 11/29/2013 12:05 PM, Oleg Nesterov wrote:
>>>
>>> Can't we invalidate pte (so that any user will stuck in page fault),
>>> update the page(s), restore the pte and drop the locks?
>>
>> That would require a global TLB shootdown
>
> Well, it is not really global, it is for mm_cpumask() and for good
> reason?
>
> And is it really worse than on_each_cpu(do_sync_core) and the usage
> of text_mutex?
>

Probably not, but one would have to consider the total amount of
synchronization needed.

>> (and wouldn't help
>> shared-memory code segments, if we care about that at all.)
>
> Well, I think this should only support the private mappings.
>

Well, what do you do if someone tries this on a MAP_SHARED mapping?
Error out?

-hpa