Re: [PATCH 37/41] rcu: New rcu_user_enter() and rcu_user_exit() APIs

[Frederic Weisbecker]

On Tue, May 22, 2012 at 11:23:06AM -0700, Paul E. McKenney wrote:
> On Tue, May 01, 2012 at 01:55:11AM +0200, Frederic Weisbecker wrote:
> > These two APIs are provided to help the implementation
> > of an adaptive tickless kernel (cf: nohz cpusets). We need
> > to run into RCU extended quiescent state when we are in
> > userland so that a tickless CPU is not involved in the
> > global RCU state machine and can shutdown its tick safely.
> > 
> > These APIs are called from syscall and exception entry/exit
> > points and can't be called from interrupt.
> > 
> > They are essentially the same than rcu_idle_enter() and
> > rcu_idle_exit() minus the checks that ensure the CPU is
> > running the idle task.
> 
> This looks reasonably sane.  There are a few nits like missing comment
> headers for functions and the need for tracing, but I can handle that
> when I pull it in.  I am happy to do that pretty much any time, but not
> before the API stabilizes.  ;-)
> 
> So let me know when it is ready for -rcu.

Ok. So would you be willing to host this specific part in -rcu? I don't
know if these APIs are welcome upstream if they have no upstream users
yet. OTOH it would be easier for me if I don't need to include these patches
in my endless rebases.

Another solution is to host that in some seperate tree. In yours or in -tip.
Ingo seemed to be willing to host this patchset.

What do you think?

I believe I need to rebase against your latest changes though.
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