Re: MMIO and gcc re-ordering issue

Linus Torvalds
2008-05-27T22:02:44Z

On Tue, 27 May 2008, Matthew Wilcox wrote:

> On Tue, May 27, 2008 at 10:38:22PM +0100, Alan Cox wrote:
> > > re-ordering, even though I doubt it will be visible in practice. So if you
> > > use the "__" versions, you'd better have barriers even on x86!
> >
> > Are we also going to have __ioread*/__iowrite* ?
>
> Didn't we already define ioread*() to have loose semantics?

They are supposed to have the same semantics as readl/writel.

And yes, it's "loose", but only when compared to inb/outb (which are
really very strict, if you want to emulate x86 - an "outb" basically is
not only ordered, it doesn't even post the write, and waits until it has
hit the bus!)

Linus