linux-kernel - Re: [PATCH] RISC-V: Enable the IPI before workqueue_online

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Message-ID: <CAKddAkB7r59sazmksi491Ubn0A-2C=Qhg=00thOSN=ZWzoVqjQ@mail.gmail.com>
Date: Wed, 17 Jul 2024 09:20:01 +0800
From: Nick Hu <nick.hu@...ive.com>
To: Anup Patel <anup@...infault.org>
Cc: paul.walmsley@...ive.com, palmer@...belt.com, aou@...s.berkeley.edu, 
	tglx@...utronix.de, peterz@...radead.org, samuel.holland@...ive.com, 
	tj@...nel.org, linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	greentime.hu@...ive.com, zong.li@...ive.com
Subject: Re: [PATCH] RISC-V: Enable the IPI before workqueue_online_cpu()

Hi Anup

On Tue, Jul 16, 2024 at 6:51 PM Anup Patel <anup@...infault.org> wrote:
>
> On Tue, Jul 16, 2024 at 2:35 PM Nick Hu <nick.hu@...ive.com> wrote:
> >
> > Sometimes the hotplug cpu stalls at the arch_cpu_idle() for a while after
> > workqueue_online_cpu(). When cpu stalls at the idle loop, the reschedule
> > IPI is pending. However the enable bit is not enabled yet so the cpu stalls
> > at WFI until watchdog timeout. Therefore enable the IPI before the
> > workqueue_online_cpu() to fix the issue.
> >
> > Fixes: 63c5484e7495 ("workqueue: Add multiple affinity scopes and interface to select them")
> > Signed-off-by: Nick Hu <nick.hu@...ive.com>
> > ---
> >  arch/riscv/kernel/sbi-ipi.c | 2 +-
> >  include/linux/cpuhotplug.h  | 1 +
> >  2 files changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/riscv/kernel/sbi-ipi.c b/arch/riscv/kernel/sbi-ipi.c
> > index 1026e22955cc..e05e68de8871 100644
> > --- a/arch/riscv/kernel/sbi-ipi.c
> > +++ b/arch/riscv/kernel/sbi-ipi.c
> > @@ -71,7 +71,7 @@ void __init sbi_ipi_init(void)
> >          * the masking/unmasking of virtual IPIs is done
> >          * via generic IPI-Mux
> >          */
> > -       cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
> > +       cpuhp_setup_state(CPUHP_AP_IRQ_RISCV_SWINT_STARTING,
> >                           "irqchip/sbi-ipi:starting",
> >                           sbi_ipi_starting_cpu, NULL);
> >
> > diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> > index 7a5785f405b6..57dcf1229b27 100644
> > --- a/include/linux/cpuhotplug.h
> > +++ b/include/linux/cpuhotplug.h
> > @@ -147,6 +147,7 @@ enum cpuhp_state {
> >         CPUHP_AP_IRQ_LOONGARCH_STARTING,
> >         CPUHP_AP_IRQ_SIFIVE_PLIC_STARTING,
> >         CPUHP_AP_IRQ_RISCV_IMSIC_STARTING,
> > +       CPUHP_AP_IRQ_RISCV_SWINT_STARTING,
>
> This is a misleading name.
>
> I suggest s/_RISCV_SWINT_/_RISCV_SBI_IPI_/ .
>
Good point.
I'll update it in the next version.
Thank you for the feedback.

> >        CPUHP_AP_ARM_MVEBU_COHERENCY,
> >         CPUHP_AP_PERF_X86_AMD_UNCORE_STARTING,
> >         CPUHP_AP_PERF_X86_STARTING,
> > --
> > 2.34.1
> >
>
> Regards,
> Anup

Regards,
Nick