Re: [PATCH 1/2] kthread: add barriers to set_kthread_struct() and to_kthread()

[Peter Zijlstra]

On Thu, Mar 16, 2017 at 12:09:44PM -0400, Tejun Heo wrote:
> On Thu, Mar 16, 2017 at 04:55:34PM +0100, Peter Zijlstra wrote:
> > > Oops, as for adding lockless_assign_pointer(), wouldn't smp_wmb() be a
> > > better match for smp_read_barrier_depends()?  ISTR acquire/release
> > > pairs being more expensive on some archs.
> > 
> > 88c1863066cc ("rcu: Define rcu_assign_pointer() in terms of smp_store_release()")
> 
> Hmmm, nice, can we always prefer store_release over wmb from now on?

I would advocate using whichever barrier is most natural for the
occasion.

Only if there really is a very very compelling performance argument
should we look further.