Re: [RFC 0/2] Reenable might_sleep() checks for might_fault() when atomic

[David Hildenbrand <dahi@linux.vnet.ibm.com>]

> OTOH, there is no reason why we need to disable preemption over that
> page_fault_disabled() region. There are code pathes which really do
> not require to disable preemption for that.
> 
> We have that seperated in preempt-rt for obvious reasons and IIRC
> Peter Zijlstra tried to distangle it in mainline some time ago. I
> forgot why that never got merged.
> 

Of course, we can completely separate that in our page fault code by doing
pagefault_disabled() checks instead of in_atomic() checks (even in add on
patches later).

> We tie way too much stuff on the preemption count already, which is a
> mightmare because we have no clear distinction of protection
> scopes. 

Although it might not be optimal, but keeping a separate counter for
pagefault_disable() as part of the preemption counter seems to be the only
doable thing right now. I am not sure if a completely separated counter is even
possible, increasing the size of thread_info.

I am working on a prototype right now.

Thanks!

> 
> Thanks,
> 
> 	tglx
>