[PATCH v2] ARM: Don't use complete() during __cpu_die

Mark Rutland
2015-02-13T15:52:08Z

[...]

> > Aside: For that last row we really should be setting cpu->hotpluggable
> > in struct cpu based on what cpu_ops::cpu_disable returns (from what I
> > can tell we use that op to indicate if a CPU can be hotplugged).
> >
>
> There's a patch for that (tm).
>
> ----8<----
>
> From: Stephen Boyd <sboyd@codeaurora.org>
> Subject: [PATCH] ARM: smp: Only expose /sys/.../cpuX/online if hotpluggable
>
> Writes to /sys/.../cpuX/online fail if we determine the platform
> doesn't support hotplug for that CPU. Let's figure this out
> befoer we make the sysfs nodes so that the online file doesn't
> even exist if it's not possible to hotplug the CPU.
>
> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
> ---
> arch/arm/include/asm/smp.h | 6 ++++++
> arch/arm/kernel/setup.c | 2 +-
> arch/arm/kernel/smp.c | 11 ++++-------
> 3 files changed, 11 insertions(+), 8 deletions(-)
>
> diff --git a/arch/arm/include/asm/smp.h b/arch/arm/include/asm/smp.h
> index 18f5a554134f..9f82430efd59 100644
> --- a/arch/arm/include/asm/smp.h
> +++ b/arch/arm/include/asm/smp.h
> @@ -123,4 +123,10 @@ struct of_cpu_method {
> */
> extern void smp_set_ops(struct smp_operations *);
>
> +#ifdef CONFIG_HOTPLUG_CPU
> +extern int platform_can_hotplug_cpu(unsigned int cpu);
> +#else
> +static inline int platform_can_hotplug_cpu(unsigned int cpu) { return 0; }
> +#endif
> +
> #endif /* ifndef __ASM_ARM_SMP_H */
> diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
> index 715ae19bc7c8..c61c09defc78 100644
> --- a/arch/arm/kernel/setup.c
> +++ b/arch/arm/kernel/setup.c
> @@ -974,7 +974,7 @@ static int __init topology_init(void)
>
> for_each_possible_cpu(cpu) {
> struct cpuinfo_arm *cpuinfo = &per_cpu(cpu_data, cpu);
> - cpuinfo->cpu.hotpluggable = 1;
> + cpuinfo->cpu.hotpluggable = platform_can_hotplug_cpu(cpu);
> register_cpu(&cpuinfo->cpu, cpu);
> }
>
> diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
> index fe0386c751b2..4d213b24db60 100644
> --- a/arch/arm/kernel/smp.c
> +++ b/arch/arm/kernel/smp.c
> @@ -174,18 +174,19 @@ static int platform_cpu_kill(unsigned int cpu)
> return 1;
> }
>
> -static int platform_cpu_disable(unsigned int cpu)
> +int platform_can_hotplug_cpu(unsigned int cpu)
> {
> if (smp_ops.cpu_disable)
> - return smp_ops.cpu_disable(cpu);
> + return smp_ops.cpu_disable(cpu) ? 0 : 1;
>
> /*
> * By default, allow disabling all CPUs except the first one,
> * since this is special on a lot of platforms, e.g. because
> * of clock tick interrupts.
> */
> - return cpu == 0 ? -EPERM : 0;
> + return cpu == 0 ? 0 : 1;
> }
> +
> /*
> * __cpu_disable runs on the processor to be shutdown.
> */
> @@ -194,10 +195,6 @@ int __cpu_disable(void)
> unsigned int cpu = smp_processor_id();
> int ret;
>
> - ret = platform_cpu_disable(cpu);
> - if (ret)
> - return ret;

For PSCI 0.2+ I was hoping to hook the MIGRATE logic in here. The secure
side may reject hotplugging of a CPU, but it's a dynamic property of the
system and so can't be probed once at boot time.

I guess when I manage to get around to that I can restore a hook here.

Thanks,
Mark.