PERFORCE change 33663 for review

[John Baldwin]

On 12-Jul-2003 Eric Anholt wrote:
> On Thu, 2003-06-26 at 10:57, John Baldwin wrote:
>> On 25-Jun-2003 Peter Wemm wrote:
>> > http://perforce.freebsd.org/chv.cgi?CH=33663
>> > 
>> > Change 33663 by peter at peter_hammer on 2003/06/25 15:05:09
>> > 
>> >       Port sym to amd64
>> 
>> This is possibly not correct.  Do all hammer's support the P3+
>> SFENCE and related instructions?  Even i386 should probably be
>> using what bus_space_barrier() uses.  Heck, sym should probably
>> just be using bus_space_barrier anyways.
> 
> It would sure be nice to have an MI call for the bus_space_barrier()
> calls that don't need a bus_space_tag.  The DRM unfortunately doesn't
> (and won't ever, I think) do bus_space, so we have to have
> platform-specific ifdefs for read, write, and read/write barriers.

For simple memory barriers, you can probably get by with atomic(9)
operations coupled with appropriate membars.

-- 

John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/