linux-kernel - Re: [PATCH v2 33/35] osnoise: handle quiescent states for PREEMPT

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Message-ID: <cfaabce3-752b-4f38-9e32-06326e646b5e@kernel.org>
Date: Tue, 28 May 2024 15:12:52 +0200
From: Daniel Bristot de Oliveira <bristot@...nel.org>
To: Ankur Arora <ankur.a.arora@...cle.com>, linux-kernel@...r.kernel.org
Cc: tglx@...utronix.de, peterz@...radead.org, torvalds@...ux-foundation.org,
 paulmck@...nel.org, rostedt@...dmis.org, mark.rutland@....com,
 juri.lelli@...hat.com, joel@...lfernandes.org, raghavendra.kt@....com,
 sshegde@...ux.ibm.com, boris.ostrovsky@...cle.com, konrad.wilk@...cle.com
Subject: Re: [PATCH v2 33/35] osnoise: handle quiescent states for
 PREEMPT_RCU=n, PREEMPTION=y

On 5/28/24 02:35, Ankur Arora wrote:
> To reduce RCU noise for nohz_full configurations, osnoise depends
> on cond_resched() providing quiescent states for PREEMPT_RCU=n
> configurations. And, for PREEMPT_RCU=y configurations does this
> by directly calling rcu_momentary_dyntick_idle().
> 
> With PREEMPT_AUTO=y, however, we can have configurations with
> (PREEMPTION=y, PREEMPT_RCU=n), which means neither of the above can
> help.
> 
> Handle that by fallback to the explicit quiescent states via
> rcu_momentary_dyntick_idle().
> 
> Cc: Paul E. McKenney <paulmck@...nel.org>
> Cc: Daniel Bristot de Oliveira <bristot@...nel.org>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Suggested-by: Paul E. McKenney <paulmck@...nel.org>
> Signed-off-by: Ankur Arora <ankur.a.arora@...cle.com>

Acked-by: Daniel Bristot de Oliveira <bristot@...nel.org>

Thanks
-- Daniel