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References: <20210706041820.1536502-1-chenhuacai@loongson.cn>
 <20210706041820.1536502-8-chenhuacai@loongson.cn> <CAK8P3a3FJSX6U9i0KYDKGVgPxi=OnrJJg73d74=KOkbEBoVa+g@mail.gmail.com>
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From:   Arnd Bergmann <arnd@kernel.org>
Date:   Tue, 6 Jul 2021 12:57:16 +0200
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Subject: Re: [PATCH 07/19] LoongArch: Add process management
To:     Huacai Chen <chenhuacai@loongson.cn>
Cc:     Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        David Airlie <airlied@linux.ie>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        Xuefeng Li <lixuefeng@loongson.cn>,
        Huacai Chen <chenhuacai@gmail.com>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>
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On Tue, Jul 6, 2021 at 6:18 AM Huacai Chen <chenhuacai@loongson.cn> wrote:

> +void arch_cpu_idle(void)
> +{
> +       local_irq_enable();
> +       __arch_cpu_idle();
> +}

This looks racy: What happens if an interrupt is pending and hits before
entering __arch_cpu_idle()?

Usually CPU idle instructions are designed to be called with interrupts disabled
and wait until an interrupt happens, including one that was already pending.

           Arnd