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

David Howells dhowells at redhat.com
Thu Mar 9 04:19:41 EST 2006

Matthew Wilcox <matthew at 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

> 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.


More information about the Linuxppc64-dev mailing list