Re: [PATCH rcu 06/11] osnoise: provide quiescent states

[Steven Rostedt]

On Mon, 24 Feb 2025 19:55:11 -0800
Boqun Feng <boqun.feng@xxxxxxxxx> wrote:

> From: Ankur Arora <ankur.a.arora@xxxxxxxxxx>
> 
> To reduce RCU noise for nohz_full configurations, osnoise depends
> on cond_resched() providing quiescent states for PREEMPT_RCU=n
> configurations. For PREEMPT_RCU=y configurations -- where
> cond_resched() is a stub -- we do this by directly calling
> rcu_momentary_eqs().
> 
> With (PREEMPT_LAZY=y, PREEMPT_DYNAMIC=n), however, we have a
> configuration with (PREEMPTION=y, PREEMPT_RCU=n) where neither
> of the above can help.
> 
> Handle that by providing an explicit quiescent state here for all
> configurations.
> 
> As mentioned above this is not needed for non-stubbed cond_resched(),
> but, providing a quiescent state here just pulls in one that a future
> cond_resched() would provide, so doesn't cause any extra work for
> this configuration.
> 
> Cc: Paul E. McKenney <paulmck@xxxxxxxxxx>
> Cc: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>

Acked-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>

-- Steve

> Suggested-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
> Acked-by: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
> Signed-off-by: Ankur Arora <ankur.a.arora@xxxxxxxxxx>
> Reviewed-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
> Signed-off-by: Boqun Feng <boqun.feng@xxxxxxxxx>
> ---