Re: [RFC patch 08/18] cnt32_to_63 should use smp_rmb()

Steven Rostedt
2008-11-07T20:08:26Z

On Fri, 7 Nov 2008, Mathieu Desnoyers wrote:
>
> I want to make sure
>
> __m_cnt_hi
> is read before
> mmio cnt_lo read

Hmm, let me make sure I understand why there is no wmb.

Paul, can you verify this?

Mathieu, you do the following:

read a
smp_rmb
reab b
if (test b)
write a

So the idea is that you must read b to test it. And since we must read a
before reading b we can see that we write a before either?

The question remains, can the write happen before either of the reads?

But since the read b is reading the hw clock, perhaps that just implies a
wmb on the hardware side?

-- Steve