Re: [patch] x86_*fence replaced by membar_ops(3)

[Andrew Doran <ad%netbsd.org@localhost>]

On Wed, Jan 14, 2009 at 07:55:09PM +0100, Jean-Yves Migeon wrote:

> These are the first steps to have MI Xen drivers (hi christoph!), by 
> replacing all the x86_*fence memory ops to their "equivalent" ones from 
> the membar_ops(3) API. See [1].

The x86 fence functions and generic memory barrier operations are not
equivalent.

membar_foo() are for memory barriers in a multiprocessor system.

The fence functions are used for memory barriers in respect of DMA even on a
uniprocessor system, or in a system like Xen where the NetBSD kernel is
uniprocessor but the monitor can be on a different CPU.

> [1] http://www.netbsd.org/~jym/membar_ops.diff

This should not be committed as is.

Thanks,
Andrew