Re: [PATCH RFC tip/core/rcu] SRCU rewrite

[Peter Zijlstra]

On Mon, Nov 14, 2016 at 10:36:36AM -0800, Paul E. McKenney wrote:
> SRCU uses two per-cpu counters: a nesting counter to count the number of
> active critical sections, and a sequence counter to ensure that the nesting
> counters don't change while they are being added together in
> srcu_readers_active_idx_check().
> 
> This patch instead uses per-cpu lock and unlock counters. Because the both
> counters only increase and srcu_readers_active_idx_check() reads the unlock
> counter before the lock counter, this achieves the same end without having
> to increment two different counters in srcu_read_lock(). This also saves a
> smp_mb() in srcu_readers_active_idx_check().

A very small improvement... I feel SRCU has much bigger issues :/