Re: [PATCH RFC tip/core/rcu 12/15] lib/assoc_array: Remove smp_read_barrier_depends()

From: Paul E. McKenney
Date: Wed Oct 11 2017 - 13:06:42 EST


On Wed, Oct 11, 2017 at 06:54:05PM +0200, Peter Zijlstra wrote:
> On Wed, Oct 11, 2017 at 09:47:48AM -0700, Paul E. McKenney wrote:
> > Interesting. Do we currently have any dependencies headed by
> > this_cpu_read()?
>
> Nope, but almost, look for: cpufreq_update_util_data.

This, you mean?

data = rcu_dereference_sched(*this_cpu_ptr(&cpufreq_update_util_data));

True, a non-RCU dependency use case would want to use ACCESS_ONCE()
in the new regime.

Thanx, Paul