[cpp-threads] Failed compare-and-swap

[Herb Sutter]

Is Nick Stoughton on this list, seeing this thread? Cc'ing him FHI, he's our main POSIX connection.

BTW, Nick, if we want to look at 9945, am I correct that http://www.unix.org/version3/iso_std.html which has an HTML-ized 9945-2003 is authoritative for the most recent published version? And is there anything yet-unpublished but more recent (like a working draft or a CD) we should look at if we're interested in this?


Summarizing this subthread:

I wrote:
> > > Sorry if the answer is obvious: What are some cases where a failed
> trylock
> > > needs ordering semantics?

Alexander wrote:
> > Nothing portable under ISO/IEC 9945.
> >
> > "Unless explicitly stated otherwise, if one of the above functions
> > returns an error, it is unspecified whether the invocation causes
> > memory to be synchronized."
> >
> > pthread_mutex_trylock() doesn't fall under "explicitly stated
> otherwise".

Paul wrote:
> Sounds like we need to make sure that we should either define CAS to
> have two modes of "success", or to get CAS to explicitly state
> otherwise
> should it ever be added to ISO/IEC 9945.  Might be nice to get the
> pthread_mutex_trylock() primitive to be added to the list of
> "explicitly
> stated otherwise" primitives, but that doesn't sound like a short-term
> project.  ;-)