linux-kernel - Re: [PATCH v9 1/9] preempt: Introduce HARDIRQ_DISABLE

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Message-ID: <Z8ESVjynMytXObEp@Mac.home>
Date: Thu, 27 Feb 2025 17:33:10 -0800
From: Boqun Feng <boqun.feng@...il.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Lyude Paul <lyude@...hat.com>, rust-for-linux@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>,
	"open list:SCHEDULER" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 1/9] preempt: Introduce HARDIRQ_DISABLE_BITS

On Thu, Feb 27, 2025 at 06:09:16PM -0500, Steven Rostedt wrote:
> On Thu, 27 Feb 2025 17:10:12 -0500
> Lyude Paul <lyude@...hat.com> wrote:
> 
> > From: Boqun Feng <boqun.feng@...il.com>
> 
> -ENOCHANGLOG
> 

Yeah, sorry, I forget to add them or ask Lyude to add when handing over
patches.

Lyude, could you add below in the future version?

In order to support preempt_disable()-like interrupt disabling, that is,
using part of preempt_count() to track interrupt disabling nested level,  
change the preempt_count() layout to contain 8-bit HARDIRQ_DISABLE
count.

Note that HARDIRQ_BITS and NMI_BITS are reduced by 1 because of this,
and it changes the maximum of their (hardirq and nmi) nesting level.

(I will add patch #2's commit log shortly)

Regards,
Boqun

> Why is this patch needed?
> 
> -- Steve
> 
> > 
> > Signed-off-by: Boqun Feng <boqun.feng@...il.com>
> > Signed-off-by: Lyude Paul <lyude@...hat.com>