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

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Message-ID: <ZqoOoUPDIeJX5M0e@shell.armlinux.org.uk>
Date: Wed, 31 Jul 2024 11:14:57 +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 06:03:11PM +0800, Jinjie Ruan wrote:
> On 2024/7/31 16:24, Russell King (Oracle) wrote:
> > On Wed, Jul 31, 2024 at 10:07:53AM +0800, Jinjie Ruan wrote:
> >>>  #ifdef CONFIG_PREEMPTION
> >>> +#ifdef CONFIG_PREEMPT_DYNAMIC
> >>> +	bl	need_irq_preemption
> >>> +	cmp	r0, #0
> >>> +	beq	2f
> >>> +#endif
> > 
> > Depending on the interrupt rate, this can be regarded as a fast path,
> > it would be nice if we could find a way to use static branches in
> > assembly code.
> It seems to be hard to use static keys in assembly code.
> 
> By the way, currently, most architectures have simplified assembly code
> and implemented its most functions in C functions. Does arm32 have this
> plan?

arm32 is effectively in maintenance mode; very little active development
is occuring. So, there are no plans to change the code without good
reason (as code changes without reason will needlessly affect its
stability.)

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