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@sifive.com>
---
Changes in v2: Rename the cpuhp_state of sbi ipi

 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..0cc5559c08d8 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_SBI_IPI_STARTING,
 			  "irqchip/sbi-ipi:starting",
 			  sbi_ipi_starting_cpu, NULL);
 
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 7a5785f405b6..0a8fd4a3d04c 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_SBI_IPI_STARTING,
 	CPUHP_AP_ARM_MVEBU_COHERENCY,
 	CPUHP_AP_PERF_X86_AMD_UNCORE_STARTING,
 	CPUHP_AP_PERF_X86_STARTING,
-- 
2.34.1

On Wed, Jul 17, 2024 at 8:47 AM Nick Hu <nick.hu@sifive.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@sifive.com>

LGTM.

Reviewed-by: Anup Patel <anup@brainfault.org>

Regards,
Anup

> ---
> Changes in v2: Rename the cpuhp_state of sbi ipi
>
>  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..0cc5559c08d8 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_SBI_IPI_STARTING,
>                           "irqchip/sbi-ipi:starting",
>                           sbi_ipi_starting_cpu, NULL);
>
> diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> index 7a5785f405b6..0a8fd4a3d04c 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_SBI_IPI_STARTING,
>         CPUHP_AP_ARM_MVEBU_COHERENCY,
>         CPUHP_AP_PERF_X86_AMD_UNCORE_STARTING,
>         CPUHP_AP_PERF_X86_STARTING,
> --
> 2.34.1
>