On Fri, Jan 15, 2016 at 10:29:12PM +0100, Peter Zijlstra wrote:

On Fri, Jan 15, 2016 at 09:39:12AM -0800, Paul E. McKenney wrote:

quoted

Should we start putting litmus tests for the various examples
somewhere, perhaps in a litmus-tests directory within each participating
architecture?  I have a pile of powerpc-related litmus tests on my laptop,
but they probably aren't doing all that much good there.

Yeah, or a version of them in C that we can 'compile'?

That would be good as well.  I am guessing that architecture-specific
litmus tests will also be needed, but you are right that
architecture-independent versions are higher priority.

quoted

commit 2cb4e83a1b5c89c8e39b8a64bd89269d05913e41
Author: Paul E. McKenney [off-list ref]
Date:   Fri Jan 15 09:30:42 2016 -0800

    documentation: Distinguish between local and global transitivity
    
    The introduction of smp_load_acquire() and smp_store_release() had
    the side effect of introducing a weaker notion of transitivity:
    The transitivity of full smp_mb() barriers is global, but that
    of smp_store_release()/smp_load_acquire() chains is local.  This
    commit therefore introduces the notion of local transitivity and
    gives an example.
    
    Reported-by: Peter Zijlstra [off-list ref]
    Reported-by: Will Deacon [off-list ref]
    Signed-off-by: Paul E. McKenney [off-list ref]

I think it fails to mention smp_mb__after_release_acquire(), although I
suspect we didn't actually introduce the primitive yet, which raises the
point, do we want to?

Well, it is not in v4.4.  I believe that we need good use cases before
we add it.

							Thanx, Paul