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Date:   Thu, 7 Jul 2022 23:05:21 +0800
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Subject: Re: [RFC PATCH 1/2] arm64: run softirqs on the per-CPU IRQ stack
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To:     Arnd Bergmann <arnd@arndb.de>
Cc:     Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>
References: <20220707110511.52129-1-zhengqi.arch@bytedance.com>
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 <CAK8P3a2D1KXY_a952Aw_7hH+yzYpqQaBA5LkmkfF6EwiLUgNSA@mail.gmail.com>
From:   Qi Zheng <zhengqi.arch@bytedance.com>
In-Reply-To: <CAK8P3a2D1KXY_a952Aw_7hH+yzYpqQaBA5LkmkfF6EwiLUgNSA@mail.gmail.com>
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On 2022/7/7 21:53, Arnd Bergmann wrote:
> On Thu, Jul 7, 2022 at 3:43 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote:
>> On 2022/7/7 20:58, Arnd Bergmann wrote:
>>> On Thu, Jul 7, 2022 at 1:05 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote:
>>> Are there any architectures left that use IRQ stacks but don't
>>> set HAVE_SOFTIRQ_ON_OWN_STACK? If not, we could
>>> also consider removing the Kconfig symbol and just requiring
>>> it to be done this way (for non-PREEMPT_RT).
>>
>> I haven't taken a close look at other architectures than x86 and arm,
>> but I think it's a good idea.
> 
> I had another look in the meantime, and I think it's only mips and loongarch
> now that don't use HAVE_SOFTIRQ_ON_OWN_STACK. Not sure about
> arch/um/, which is a bit different from the rest.

I just glanced at arch/um/, and it's really different from the rest:

  * Unlike i386, UML doesn't receive IRQs on the normal kernel stack
  * and switch over to the IRQ stack after some preparation.

> 
>         Arnd

-- 
Thanks,
Qi