Christoph Lameter wrote:
On Thu, 9 Aug 2007, Chris Snook wrote:
This patchset makes the behavior of atomic_read uniform by removing the
volatile keyword from all atomic_t and atomic64_t definitions that currently
have it, and instead explicitly casts the variable as volatile in
atomic_read(). This leaves little room for creative optimization by the
compiler, and is in keeping with the principles behind "volatile considered
harmful".
volatile is generally harmful even in atomic_read(). Barriers control
visibility and AFAICT things are fine.
But barriers force a flush of *everything* in scope, which we generally don't
want. On the other hand, we pretty much always want to flush atomic_*
operations. One way or another, we should be restricting the volatile behavior
to the thing that needs it. On most architectures, this patch set just moves
that from the declaration, where it is considered harmful, to the use, where it
is considered an occasional necessary evil.
See the resubmitted patchset, which also puts a cast in the atomic[64]_set
operations.
-- Chris
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