linux-kernel - Re: [patch 12/19] softirq: Add RT specific softirq accounting

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Message-ID: <20201119121801.GA20115@lothringen>
Date:   Thu, 19 Nov 2020 13:18:01 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
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 12/19] softirq: Add RT specific softirq accounting

On Fri, Nov 13, 2020 at 03:02:19PM +0100, Thomas Gleixner wrote:
> RT requires the softirq to be preemptible and uses a per CPU local lock to
> protect BH disabled sections and softirq processing. Therefore RT cannot
> use the preempt counter to keep track of BH disabled/serving.
> 
> Add a RT only counter to task struct and adjust the relevant macros in
> preempt.h.

You may want to describe a bit the reason for this per task counter.
It's not intuitive at this stage.

Thanks.