Re: [PATCH RFC memory-model 0/6] LKMM updates

Paul E. McKenney
2019-01-10T04:20:37Z

On Thu, Jan 10, 2019 at 01:39:52AM +0100, Andrea Parri wrote:
> On Wed, Jan 09, 2019 at 03:40:43PM -0800, Paul E. McKenney wrote:
> > On Thu, Jan 10, 2019 at 12:18:53AM +0100, Andrea Parri wrote:
> > > On Wed, Jan 09, 2019 at 01:07:06PM -0800, Paul E. McKenney wrote:
> > > > Hello!
> > > >
> > > > This series contains updates for the Linux-kernel memory model:
> > > >
> > > > 1-3. Add SRCU support, courtesy of Alan Stern.
> > > >
> > > > 4. Update README for adding of SRCU support.
> > > >
> > > > 5. Update memory-barriers.txt on enforcing heavy ordering for
> > > > port-I/O accesses, courtesy of Will Deacon. This one needs
> > > > an ack, preferably by someone from Intel. Matthew Wilcox
> > > > posted some feedback from an Intel manual here, which might
> > > > be considered to be a close substitute, but... ;-)
> > > >
> > > > http://lkml.kernel.org/r/20181127192234.GF10377@bombadil.infradead.org
> > > >
> > > > 6. Update Documentation/explanation.txt to include SRCU support,
> > > > courtesy of Alan Stern.
> > > >
> > > > 7. Dynamically check SRCU lock-to-unlock matching, courtesy of
> > > > Luc Maranget. This needs an ack.
> > >
> > > It seems that
> > >
> > > 1b52d0186177 ("tools/memory-model: Model smp_mb__after_unlock_lock()")
> > >
> > > from linux-rcu/dev got lost; this also needs an ack (probably yours! ;D,
> > > considered that, IIRC, you introduced the primitive and RCU is currently
> > > its only user.)
> >
> > That commit is in -tip:
> >
> > 4607abbcf464 ("tools/memory-model: Model smp_mb__after_unlock_lock()")
> >
> > So it has already left my -rcu tree. ;-)
>
> Oh, you're right: now I see the commit (e.g., with "git show"), but I
> don't see the corresponding changes applied to the tree.
>
> https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?h=locking/core&id=4607abbcf464ea2be14da444215d05c73025cf6e
> https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/tree/tools/memory-model/linux-kernel.bell?h=locking/core
>
> Is this expected?

Are you asking why it is in -tip but not in mainline? I am not sure,
but given that the merge window was over the holiday season and that
the length of the merge window proved to be shorter than many people
expected it to be, I am not too surprised. ;-)

Thanx, Paul