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In-Reply-To: <874ju59ftr.fsf@all.your.base.are.belong.to.us>
From:   Guo Ren <guoren@kernel.org>
Date:   Sat, 10 Dec 2022 18:21:10 +0800
Message-ID: <CAJF2gTTp+ruq+hadMTkkxW1XjSNjjv3VDrjRqnRnExntpCzD8A@mail.gmail.com>
Subject: Re: [PATCH -next V10 09/10] riscv: stack: Support HAVE_SOFTIRQ_ON_OWN_STACK
To:     =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn@kernel.org>
Cc:     arnd@arndb.de, palmer@rivosinc.com, tglx@linutronix.de,
        peterz@infradead.org, luto@kernel.org, conor.dooley@microchip.com,
        heiko@sntech.de, jszhang@kernel.org, lazyparser@gmail.com,
        falcon@tinylab.org, chenhuacai@kernel.org, apatel@ventanamicro.com,
        atishp@atishpatra.org, palmer@dabbelt.com,
        paul.walmsley@sifive.com, mark.rutland@arm.com,
        zouyipeng@huawei.com, bigeasy@linutronix.de,
        David.Laight@aculab.com, chenzhongjin@huawei.com,
        greentime.hu@sifive.com, andy.chiu@sifive.com, ben@decadent.org.uk,
        linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-riscv@lists.infradead.org, Guo Ren <guoren@linux.alibaba.com>
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On Fri, Dec 9, 2022 at 3:50 PM Bj=C3=B6rn T=C3=B6pel <bjorn@kernel.org> wro=
te:
>
> Guo Ren <guoren@kernel.org> writes:
>
> > On Thu, Dec 8, 2022 at 6:12 PM Bj=C3=B6rn T=C3=B6pel <bjorn@kernel.org>=
 wrote:
> >>
> >> guoren@kernel.org writes:
> >>
> >> > From: Guo Ren <guoren@linux.alibaba.com>
> >> >
> >> > Add the HAVE_SOFTIRQ_ON_OWN_STACK feature for the IRQ_STACKS config.=
 The
> >> > irq and softirq use the same independent irq_stack of percpu by time
> >> > division multiplexing.
> >> >
> >> > Tested-by: Jisheng Zhang <jszhang@kernel.org>
> >> > Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> >> > Signed-off-by: Guo Ren <guoren@kernel.org>
> >> > ---
> >> >  arch/riscv/Kconfig      |  7 ++++---
> >> >  arch/riscv/kernel/irq.c | 33 +++++++++++++++++++++++++++++++++
> >> >  2 files changed, 37 insertions(+), 3 deletions(-)
> >> >
> >> > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> >> > index 0a9d4bdc0338..bd4c4ae4cdc9 100644
> >> > --- a/arch/riscv/Kconfig
> >> > +++ b/arch/riscv/Kconfig
> >> > @@ -447,12 +447,13 @@ config FPU
> >> >         If you don't know what to do here, say Y.
> >> >
> >> >  config IRQ_STACKS
> >> > -     bool "Independent irq stacks" if EXPERT
> >> > +     bool "Independent irq & softirq stacks" if EXPERT
> >> >       default y
> >> >       select HAVE_IRQ_EXIT_ON_IRQ_STACK
> >> > +     select HAVE_SOFTIRQ_ON_OWN_STACK
> >>
> >> HAVE_IRQ_EXIT_ON_IRQ_STACK is used by softirq.c Shouldn't that be
> >> selected introduced in this patch, instead of the previous one?
> > This patch depends on the previous one. And the previous one could
> > work separately.
>
> Let me try to be more clear: IRQ_STACKS should be introduced in the
> previous patch, which adds per-cpu stacks to hardirq. This patch adds
> per-cpu stacks for softirq, and the softirq related selects:
>
>  select HAVE_IRQ_EXIT_ON_IRQ_STACK
>  select HAVE_SOFTIRQ_ON_OWN_STACK
>
> Hence, the "HAVE_IRQ_EXIT_ON_IRQ_STACK" select should be part of *this*
> patch, not the previous.
>
> Or am I missing something?
You are right, HAVE_IRQ_EXIT_ON_IRQ_STACK is belong to SOFTIRQ:
static inline void invoke_softirq(void)
{
...
        if (!force_irqthreads() || !__this_cpu_read(ksoftirqd)) {
#ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK
...
                __do_softirq();
#else
...
                do_softirq_own_stack();
#endif
...
}

I would fix that in the next version.

>
>
> Bj=C3=B6rn


--=20
Best Regards
 Guo Ren