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Date: Mon, 23 Nov 2020 20:56:03 +0100
From: Frederic Weisbecker <frederic@kernel.org>
Subject: Re: [patch 14/19] softirq: Make softirq control and processing RT
 aware
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To: Thomas Gleixner <tglx@linutronix.de>
Cc: Rich Felker <dalias@libc.org>, Catalin Marinas <catalin.marinas@arm.com>, Paul McKenney <paulmck@kernel.org>, Arnd Bergmann <arnd@arndb.de>, linux-sh@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>, Richard Weinberger <richard@nod.at>, Sebastian Andrzej Siewior <bigeasy@linutronix.de>, Valentin Schneider <valentin.schneider@arm.com>, Jeff Dike <jdike@addtoit.com>, LKML <linux-kernel@vger.kernel.org>, Yoshinori Sato <ysato@users.sourceforge.jp>, "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>, linux-parisc@vger.kernel.org, Marc Zyngier <maz@kernel.org>, Russell King <linux@armlinux.org.uk>, linux-um@lists.infradead.org, Will Deacon <will@kernel.org>, Helge Deller <deller@gmx.de>, linux-arm-kernel@lists.infradead.org, Anton Ivanov <anton.ivanov@cambridgegreys.com>

On Mon, Nov 23, 2020 at 08:27:33PM +0100, Thomas Gleixner wrote:
> On Mon, Nov 23 2020 at 14:44, Frederic Weisbecker wrote:
> > On Fri, Nov 13, 2020 at 03:02:21PM +0100, Thomas Gleixner wrote:
> >> +	/*
> >> +	 * Adjust softirq count to SOFTIRQ_OFFSET which makes
> >> +	 * in_serving_softirq() become true.
> >> +	 */
> >> +	cnt = SOFTIRQ_OFFSET;
> >> +	__local_bh_enable(cnt, false);
> >
> > But then you enter __do_softirq() with softirq_count() == SOFTIRQ_OFFSET.
> > __do_softirq() calls softirq_handle_begin() which then sets it back to
> > SOFTIRQ_DISABLE_OFFSET...
> 
> The RT variant of it added in this very same patch
> > +static inline void softirq_handle_begin(void) { }
> > +static inline void softirq_handle_end(void) { }

Oh missed that indeed, sorry!

> 
> Thanks,
> 
>         tglx

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