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Date:   Wed, 18 Oct 2023 14:00:35 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     "Paul E. McKenney" <paulmck@kernel.org>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Peter Zijlstra <peterz@infradead.org>,
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        Frederic Weisbecker <fweisbec@gmail.com>,
        Daniel Bristot de Oliveira <bristot@kernel.org>
Subject: Re: [PATCH v2 7/9] sched: define TIF_ALLOW_RESCHED
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On Wed, 18 Oct 2023 10:55:02 -0700
"Paul E. McKenney" <paulmck@kernel.org> wrote:

> > If everything becomes PREEMPT_RCU, then the above should be able to be
> > turned into just:
> > 
> >                 if (!disable_irq)
> >                         local_irq_disable();
> > 
> >                 rcu_momentary_dyntick_idle();
> > 
> >                 if (!disable_irq)
> >                         local_irq_enable();
> > 
> > And no cond_resched() is needed.  
> 
> Even given that CONFIG_PREEMPT_RCU=n still exists, the fact that
> run_osnoise() is running in kthread context with preemption and everything
> else enabled (am I right?), then the change you suggest should work fine.

There's a user space option that lets you run that loop with preemption and/or
interrupts disabled.

> 
> > > Again. There is no non-preemtible RCU with this model, unless I'm
> > > missing something important here.  
> > 
> > Daniel?  
> 
> But very happy to defer to Daniel.  ;-)

But Daniel could also correct me ;-)

-- Steve