linux-kernel - Re: [PATCH RFC] x86/entry: Ask RCU if it needs rcu_irq

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Date:   Fri, 12 Jun 2020 11:27:21 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     paulmck@...nel.org, linux-kernel@...r.kernel.org,
        rcu@...r.kernel.org
Cc:     luto@...nel.org, x86@...nel.org, frederic@...nel.org,
        rostedt@...dmis.org, joel@...lfernandes.org,
        mathieu.desnoyers@...icios.com, will@...nel.org,
        peterz@...radead.org
Subject: Re: [PATCH RFC] x86/entry: Ask RCU if it needs rcu_irq_{enter,exit}()

"Paul E. McKenney" <paulmck@...nel.org> writes:
> +static __always_inline bool rcu_needs_irq_enter(void)
> +{
> +	return !IS_ENABLED(CONFIG_TINY_RCU) &&
> +               (context_tracking_enabled_cpu(smp_processor_id()) || is_idle_task(current));

This reintroduces the #PF problem which started the whole conditional
RCU entry discussion:

   https://lore.kernel.org/lkml/20200515235125.628629605@linutronix.de/

and which made us all come to the conclusion that we can do it always
conditional. No biscuit for you. :)

Thanks,

        tglx