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

David Howells
2008-11-07T10:56:17Z

Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:

> Assume the time source is a global clock which insures that time will never
> *ever* go backward. Use a smp_rmb() to make sure the cnt_lo value is read before
> __m_cnt_hi.

If you have an smp_rmb(), then don't you need an smp_wmb()/smp_mb() to match
it to make it work? And is your assumption valid that smp_rmb() will affect
memory vs the I/O access to read the clock? There's no requirement that
cnt_lo will have been read from an MMIO location at all.

David