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

[Ingo Molnar <mingo@elte.hu>]

* 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.

( You brought up -rt but that example does not apply: it doesnt 'hide' the 
  lock instance in any way, it simply changes the preemption model. It goes to 
  great lengths to keep existing locking patterns and does not obfuscate 
  locking. )

	Ingo