Re: [patch 26/37] riscv: Switch to hotplug core state synchronization

[Palmer Dabbelt <palmer@xxxxxxxxxxx>]

On Fri, 14 Apr 2023 16:44:55 PDT (-0700), tglx@xxxxxxxxxxxxx wrote:
> Switch to the CPU hotplug core state tracking and synchronization
> mechanim. No functional change intended.
>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx>
> Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx>
> Cc: linux-riscv@xxxxxxxxxxxxxxxxxxx
> ---
>  arch/riscv/Kconfig              |    1 +
>  arch/riscv/include/asm/smp.h    |    2 +-
>  arch/riscv/kernel/cpu-hotplug.c |   14 +++++++-------
>  3 files changed, 9 insertions(+), 8 deletions(-)
>
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -116,6 +116,7 @@ config RISCV
>         select HAVE_RSEQ
>         select HAVE_STACKPROTECTOR
>         select HAVE_SYSCALL_TRACEPOINTS
> +       select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU
>         select IRQ_DOMAIN
>         select IRQ_FORCED_THREADING
>         select MODULES_USE_ELF_RELA if MODULES
> --- a/arch/riscv/include/asm/smp.h
> +++ b/arch/riscv/include/asm/smp.h
> @@ -64,7 +64,7 @@ asmlinkage void smp_callin(void);
>
>  #if defined CONFIG_HOTPLUG_CPU
>  int __cpu_disable(void);
> -void __cpu_die(unsigned int cpu);
> +static inline void __cpu_die(unsigned int cpu) { }
>  #endif /* CONFIG_HOTPLUG_CPU */
>
>  #else
> --- a/arch/riscv/kernel/cpu-hotplug.c
> +++ b/arch/riscv/kernel/cpu-hotplug.c
> @@ -8,6 +8,7 @@
>  #include <linux/sched.h>
>  #include <linux/err.h>
>  #include <linux/irq.h>
> +#include <linux/cpuhotplug.h>
>  #include <linux/cpu.h>
>  #include <linux/sched/hotplug.h>
>  #include <asm/irq.h>
> @@ -48,17 +49,15 @@ int __cpu_disable(void)
>         return ret;
>  }
>
> +#ifdef CONFIG_HOTPLUG_CPU
>  /*
> - * Called on the thread which is asking for a CPU to be shutdown.
> + * Called on the thread which is asking for a CPU to be shutdown, if the
> + * CPU reported dead to the hotplug core.
>   */
> -void __cpu_die(unsigned int cpu)
> +void arch_cpuhp_cleanup_dead_cpu(unsigned int cpu)
>  {
>         int ret = 0;
>
> -       if (!cpu_wait_death(cpu, 5)) {
> -               pr_err("CPU %u: didn't die\n", cpu);
> -               return;
> -       }
>         pr_notice("CPU%u: off\n", cpu);
>
>         /* Verify from the firmware if the cpu is really stopped*/
> @@ -75,9 +74,10 @@ void arch_cpu_idle_dead(void)
>  {
>         idle_task_exit();
>
> -       (void)cpu_report_death();
> +       cpuhp_ap_report_dead();
>
>         cpu_ops[smp_processor_id()]->cpu_stop();
>         /* It should never reach here */
>         BUG();
>  }
> +#endif
Acked-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>