Subject: Re: CVS commit: src/sys/arch/xen/xen
To: Lennart Augustsson <>
From: Manuel Bouyer <>
List: source-changes
Date: 03/27/2005 01:02:17
On Sun, Mar 27, 2005 at 12:54:48AM +0100, Lennart Augustsson wrote:
> >This would probablt be a good idea, but isn't __insn_barrier() a
> >gcc builtin ?
> Would that really be correct?  I thought __insn_barries() was there
> to stop gcc from reordering instructions, whereas x86_lfence() is
> there to stop the processor from reordering loads and stores.

I think we want a MI function to stop the processor from reordering
instructions too. There is potentially a similar problem in the esiop(4)
driver than the one I had with xen. I could abuse bus_space_barrier()
for this but it's not quite right either.

If we don't want the compiler to reorder instructions, I don't think we want
to CPU to do it.

Manuel Bouyer <>
     NetBSD: 26 ans d'experience feront toujours la difference