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

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Message-ID: <CAAhSdy1pjg=etzNNu-E+-VDmU5gLkS2jYhdO29pPN23OQ5=NiA@mail.gmail.com>
Date: Tue, 16 Jul 2024 16:21:02 +0530
From: Anup Patel <anup@...infault.org>
To: Nick Hu <nick.hu@...ive.com>
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()

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_/ .

>         CPUHP_AP_ARM_MVEBU_COHERENCY,
>         CPUHP_AP_PERF_X86_AMD_UNCORE_STARTING,
>         CPUHP_AP_PERF_X86_STARTING,
> --
> 2.34.1
>

Regards,
Anup