linux-kernel - Re: [patch 14/19] softirq: Make softirq control and processing RT aware

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Message-ID: <87r1ojli2v.fsf@nanos.tec.linutronix.de>
Date:   Tue, 24 Nov 2020 01:22:16 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Paul McKenney <paulmck@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Arnd Bergmann <arnd@...db.de>,
        "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
        Helge Deller <deller@....de>, linux-parisc@...r.kernel.org,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>, linux-sh@...r.kernel.org,
        Jeff Dike <jdike@...toit.com>,
        Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        linux-um@...ts.infradead.org, Russell King <linux@...linux.org.uk>,
        Marc Zyngier <maz@...nel.org>,
        Valentin Schneider <valentin.schneider@....com>,
        linux-arm-kernel@...ts.infradead.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
Subject: Re: [patch 14/19] softirq: Make softirq control and processing RT aware

Frederic,

On Tue, Nov 24 2020 at 01:13, Frederic Weisbecker wrote:
> On Tue, Nov 24, 2020 at 01:06:15AM +0100, Thomas Gleixner wrote:
>> Good point. Haven't thought about that. Let me have a look again.
>
> But I'm cooking a patchset which moves account_irq_enter_time() after
> HARDIRQ_OFFSET or SOFTIRQ_OFFSET is incremented. This will allow us to move
> tick_irq_enter() under this layout:
>
> 		 preempt_count_add(HARDIRQ_OFFSET)
> 		 lockdep_hardirq_enter()
> 		 tick_irq_enter()
> 		 account_irq_enter_time()
>
> This way tick_irq_enter() can be correctly handled by lockdep and we can remove
> the nasty hack which temporarily disables softirqs around it.
>
> And as a side effect it should also fix your issue.
>
> I should have that ready soonish.

Sounds to good to be true :)

Looking forward to it!

Thanks for taking care of that!

       tglx