linux-kernel - Re: [PATCH] ARM: support PREEMPT

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Message-ID: <ZqzGp14u/XTST8v1@shell.armlinux.org.uk>
Date: Fri, 2 Aug 2024 12:44:39 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Jinjie Ruan <ruanjinjie@...wei.com>
Cc: arnd@...db.de, afd@...com, akpm@...ux-foundation.org,
	linus.walleij@...aro.org, eric.devolder@...cle.com, robh@...nel.org,
	vincent.whitchurch@...s.com, bhe@...hat.com, nico@...xnic.net,
	ardb@...nel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH] ARM: support PREEMPT_DYNAMIC

On Wed, Jul 31, 2024 at 10:07:53AM +0800, Jinjie Ruan wrote:
> On 2024/6/20 17:00, Jinjie Ruan wrote:
> > Enable support for PREEMPT_DYNAMIC on arm32, allowing the preemption model
> > to be chosen at boot time.
> > 
> > Similar to arm64, arm32 does not yet use the generic entry code, we must
> > define our own `sk_dynamic_irqentry_exit_cond_resched`, which will be
> > enabled/disabled by the common code in kernel/sched/core.c.
> > 
> > And arm32 use generic preempt.h, so declare
> > `sk_dynamic_irqentry_exit_cond_resched` if the arch do not use generic
> > entry. Other architectures which use generic preempt.h but not use generic
> > entry can benefit from it.
> > 
> > Test ok with the below cmdline parameters on Qemu versatilepb board:
> > 	`preempt=none`
> > 	`preempt=voluntary`
> > 	`preempt=full`
> > 
> > Update preempt mode with debugfs interface on above Qemu board is also
> > tested ok:
> > 	# cd /sys/kernel/debug/sched
> > 	# echo none > preempt
> > 	# echo voluntary > preempt
> > 	# echo full > preempt

Do you have a use case for this feature?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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