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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Thu, 14 Jul 2022 13:32:30 +0200
Message-ID: <CAK8P3a2kgVikkKBZLa31XUopEFa9ykLS=qxiH=qiFD8HtUvw=A@mail.gmail.com>
Subject: Re: [PATCH v1 1/2] arm64: run softirqs on the per-CPU IRQ stack
To:     Qi Zheng <zhengqi.arch@bytedance.com>
Cc:     Arnd Bergmann <arnd@arndb.de>,
        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>
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On Fri, Jul 8, 2022 at 11:49 AM Qi Zheng <zhengqi.arch@bytedance.com> wrote:
>
> Currently arm64 supports per-CPU IRQ stack, but softirqs
> are still handled in the task context.
>
> Since any call to local_bh_enable() at any level in the task's
> call stack may trigger a softirq processing run, which could
> potentially cause a task stack overflow if the combined stack
> footprints exceed the stack's size, let's run these softirqs
> on the IRQ stack as well.
>
> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>

This seems like a nice improvement, and this version addresses
my concern I raised on the RFC version.

Reviewed-by: Arnd Bergmann <arnd@arndb.de>