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

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Message-ID: <3855e3a4-769b-5162-0747-cf72b94f7089@huawei.com>
Date: Thu, 1 Aug 2024 09:26:58 +0800
From: Jinjie Ruan <ruanjinjie@...wei.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
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 2024/7/31 18:14, Russell King (Oracle) wrote:
> 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.)

Thank you for helping me with my question.

>