On Thu, Nov 16, 2017 at 06:34:17PM +0100, Peter Zijlstra wrote:

On Thu, Nov 16, 2017 at 09:16:49AM -0800, Nick Desaulniers wrote:

quoted

On Thu, Nov 16, 2017 at 8:59 AM, Peter Zijlstra [off-list ref] wrote:

quoted

On Thu, Nov 16, 2017 at 08:50:41AM -0800, Nick Desaulniers wrote:

quoted

On Thu, Nov 16, 2017 at 8:30 AM, Peter Zijlstra [off-list ref] wrote:

quoted

Ideally we'd get the toolchain people to commit to supporting the kernel
memory model along side the C11 one. That would help a ton.

Does anyone from the kernel side participate in the C standardization process?

Yes, Paul McKenney and Will Deacon. Doesn't mean these two can still be
reconciled though. From what I understand C11 (and onwards) are
incompatible with the kernel model on a number of subtle points.

It would be good to have these incompatibilities written down, then
for the sake of argument, they can be cited both for discussions on
LKML and in the C standardization process.  For example, a running
list in Documentation/ or something would make it so that anyone could
understand and cite current issues with the latest C standard.

Will should be able to produce this list; I know he's done before, I
just can't find it -- my Google-foo isn't strong today.

Here you go:

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0124r4.html

quoted

I don't understand why we'd block patches for enabling experimental
features.  We've been running this patch-set on actual devices for
months and would love to provide them to the community for further
testing.  If bugs are found, then there's more evidence to bring to
the C standards committee.  Otherwise we're shutting down feature
development for the sake of potential bugs in a C standard we're not
even using.

So the problem is that its very very hard (and painful) to find these
bugs. Getting the tools people to comment on these specific
optimizations would really help lots.

It would be good to get something similar to LKMM into KTSAN, for
example.  There would probably be a few differences due to efficiency
concerns, but closer is better than less close.  ;-)

							Thanx, Paul