Re: [patch 2] mm: speculative get_page

Christoph Lameter
2005-06-28T22:19:26Z

On Tue, 28 Jun 2005, Jesse Barnes wrote:

> On ia64 at least, the unlock is only a one way barrier. The store to
> realease the lock uses release semantics (since the lock is declared
> volatile), which implies that prior stores are visible before the
> unlock occurs, but subsequent accesses can 'float up' above the unlock.
> See http://www.gelato.unsw.edu.au/linux-ia64/0304/5122.html for some
> more details.

The manual talks about "accesses" not stores. So this applies to loads and
stores. Subsequent accesses can float up but only accesses prior to the
instruction with release semantics (like an unlock) are guaranteed to be
visible.