On 9/12/2014 5:25 AM, Martin Buchholz wrote:
Webrev updated to remove the comparison with volatile loads and stores.
Thanks. More inline ...
On Sun, Dec 7, 2014 at 2:40 PM, David Holmes <david.hol...@oracle.com> wrote:
On 6/12/2014 7:49 AM, Martin Buchholz wrote:
On Thu, Dec 4, 2014 at 5:55 PM, David Holmes <david.hol...@oracle.com>
wrote:
In general phrasing like: " also known as a LoadLoad plus LoadStore
barrier
..." is misleading to me as these are not "aliases"- the loadFence (in
this
case) is being specified to have the same semantics as the
loadload|storeload. It should say "corresponds to a LoadLoad plus
LoadStore
barrier"
+ * Ensures that loads before the fence will not be reordered with
loads and
+ * stores after the fence; also known as a LoadLoad plus LoadStore
barrier,
I don't understand this. I believe they _are_ aliases. The first
clause perfectly describes a "LoadLoad plus LoadStore barrier".
I find the language use inappropriate - you are defining the first to be the
second.
Am I missing something? Is there something else that "LoadLoad plus
LoadStore barrier" (as used in hotspot sources and elsewhere) could
possibly mean?
I think we are getting our wires crossed here. My issue is with the wording:
"also known as a LoadLoad plus LoadStore barrier"
because we are explicitly choosing to specify the operation as being a
LoadLoad plus LoadStore barrier. Hence I would much prefer it to say
that this "corresponds to a LoadLoad plus LoadStore barrier".
- as per the "Corresponds to a C11 ...". And referring to things
like "load-acquire fence" is meaningless without some reference to a
definition - who defines a load-acquire fence? Is there a universal
definition? I would be okay with something looser eg:
Well, I'm defining "load-acquire fence" here in the javadoc - I'm
claiming that loadFence is also known via other terminology, including
"load-acquire fence". Although it's true that "load-acquire fence" is
also used to refer to the corresponding C11 fence, which has subtly
different semantics.
When you say "also known as XXX" it means that XXX is already defined
elsewhere. Unless there is a generally accepted definition of XXX then this
doesn't add much value.
Everything about this topic is confusing, but I continue to think that
"load-acquire fence" is a common industry term.
Then please point me to the common industry definition of it because I
couldn't find anything definitive. And as you state yourself above one
definition of it - the corresponding C11 fence - does not in fact have
the same semantics!
One of the reasons I
want to include them in the javadoc is precisely because these
different terms are generally used synonymously.
I would concede "sometimes referred to as ..." as that doesn't imply a
single standard agreed upon definition, while still making the link.
Though even then there is a danger of making false assumptions about the
equivalence of this fence and those going by the name "load-acquire fence".
David
