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

[Steven Rostedt]

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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/