Re: [mm][RFC][PATCH 0/11] mm accessor updates.

KAMEZAWA Hiroyuki
2009-12-18T23:18:39Z

Ingo Molnar wrote:
>
> * Christoph Lameter <cl@linux-foundation.org> wrote:
>
>> > We've been through this many times in the past within the kernel: many
>> > times when we hid some locking primitive within some clever wrapping
>> > scheme the quality of locking started to deteriorate. In most of the
>> > important cases we got rid of the indirection and went with an
>> existing
>> > core kernel locking primitive which are all well known and have clear
>> > semantics and lead to more maintainable code.
>>
>> The existing locking APIs are all hiding lock details at various levels.
>> We
>> have various specific APIs for specialized locks already Page locking
>> etc.
>
> You need to loo at the patches. This is simply a step backwards:
>
> - up_read(&mm->mmap_sem);
> + mm_read_unlock(mm);
>
> because it hides the lock instance.
>
After rewriting speculative-page-fault patches, I feel I can do it
without mm_accessor, by just skipping mmap_sem in fault.c. Then, original
problem I tried to fix, false sharing at multithread page fault, can be
fixed without this.

Then, I myself stop this.

About range-locking of mm_struct, I don't find any good approach.

Sorry for annoying and thank you all.
-Kame