Re: [PATCH] Document Linux's memory barriers [try #2]

David Howells
2006-03-08T17:20:00Z

Matthew Wilcox <matthew@wil.cx> wrote:

> > That might be worth an example with an if() because PPC will do this and
> > if its a read with a side effect (eg I/O space) you get singed..
>
> PPC does speculative memory accesses to IO? Are you *sure*?

Can you do speculative reads from frame buffers?

> # define smp_read_barrier_depends() do { } while(0)

What's this one meant to do?

> Port space is deprecated though. PCI 2.3 says:

That's sort of irrelevant for the here. I still need to document the
interaction.

> Since memory write transactions may be posted in bridges anywhere
> in the system, and I/O writes may be posted in the host bus bridge,

I'm not sure whether this is beyond the scope of this document. Maybe the
document's scope needs to be expanded.

David