linux-kernel - Re: [PATCH v2 2/6] genirq: Allow an interrupt to be marked as 'raw'

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Date:   Thu, 3 Dec 2020 14:03:20 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Valentin Schneider <valentin.schneider@....com>
Cc:     Marc Zyngier <maz@...nel.org>,
        LAK <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@....linux.org.uk>,
        Android Kernel Team <kernel-team@...roid.com>
Subject: Re: [PATCH v2 2/6] genirq: Allow an interrupt to be marked as 'raw'

On Thu, Nov 26, 2020 at 06:18:33PM +0000, Valentin Schneider wrote:
> If I got the RCU bits right from what Thomas mentioned in
> 
>   https://lore.kernel.org/r/87ft5q18qs.fsf@nanos.tec.linutronix.de
>   https://lore.kernel.org/r/87lfewnmdz.fsf@nanos.tec.linutronix.de
> 
> then we're still missing something to notify RCU in the case the IRQ hits
> the idle task. All I see on our entry path is
> 
>   trace_hardirqs_off();
>   ...
>   irq_handler()
>     handle_domain_irq();
>   ...
>   trace_hardirqs_on();
> 
> so we do currently rely on handle_domain_irq()'s irq_enter() + irq_exit()
> for that. rcu_irq_enter() says CONFIG_RCU_EQS_DEBUG=y can detect missing
> bits, but I don't get any warnings with your series on my Juno.

The scheduler IPI really doesn't need RCU either ;-)