Re: [PATCH 17/19] locking/barriers: Kill lockless_dereference

[Ingo Molnar]

* Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> wrote:

> From: Will Deacon <will.deacon@xxxxxxx>
> 
> lockless_dereference is a nice idea, but its gained little traction in
> kernel code since it's introduction three years ago. This is partly

s/its/it
s/it's/its

> because it's a pain to type, but also because using READ_ONCE instead
> will work correctly on all architectures apart from Alpha, which is a
> fully supported but somewhat niche architecture these days.
> 
> This patch moves smp_read_barrier_depends() (a NOP on all architectures
> other than Alpha) from lockless_dereference into READ_ONCE, converts
> the few actual users over to READ_ONCE and then finally removes
> lockless_dereference altogether.

Nit: if we refer to smp_read_barrier_depends() with parentheses (which is the nice 
thing to do for function-alike symbols), then we should do the same with 
READ_ONCE() and lockless_dereference() as well.

Also, could we please split this into three patches:

 #1: Add smp_read_barrier_depends() to READ_ONCE()
 #2: Convert all lockless_dereference() users to READ_ONCE()
 #3: Remove the now unused lockless_dereference() API

to make it easier to analyze if bisected to, should any problems arise?

Thanks,

	Ingo