[PATCH v8 3/3] ARM: Check if a CPU has gone offline

[Anup Patel]

Hi Ashwin,

On 26 April 2014 01:18, Ashwin Chaugule <ashwin.chaugule at linaro.org> wrote:
> PSCIv0.2 adds a new function called AFFINITY_INFO, which
> can be used to query if a specified CPU has actually gone
> offline. Calling this function via cpu_kill ensures that
> a CPU has quiesced after a call to cpu_die.
>
> Signed-off-by: Ashwin Chaugule <ashwin.chaugule at linaro.org>
> Reviewed-by: Rob Herring <robh at kernel.org>
> ---
>  arch/arm/kernel/psci_smp.c | 32 ++++++++++++++++++++++++++++++++
>  include/uapi/linux/psci.h  |  5 +++++
>  2 files changed, 37 insertions(+)
>
> diff --git a/arch/arm/kernel/psci_smp.c b/arch/arm/kernel/psci_smp.c
> index 570a48c..94e230c 100644
> --- a/arch/arm/kernel/psci_smp.c
> +++ b/arch/arm/kernel/psci_smp.c
> @@ -16,6 +16,8 @@
>  #include <linux/init.h>
>  #include <linux/smp.h>
>  #include <linux/of.h>
> +#include <linux/delay.h>
> +#include <uapi/linux/psci.h>
>
>  #include <asm/psci.h>
>  #include <asm/smp_plat.h>
> @@ -66,6 +68,35 @@ void __ref psci_cpu_die(unsigned int cpu)
>         /* We should never return */
>         panic("psci: cpu %d failed to shutdown\n", cpu);
>  }
> +
> +int __ref psci_cpu_kill(unsigned int cpu)
> +{
> +       int err, i;
> +
> +       if (!psci_ops.affinity_info)
> +               return 1;
> +       /*
> +        * cpu_kill could race with cpu_die and we can
> +        * potentially end up declaring this cpu undead
> +        * while it is dying. So, try again a few times.
> +        */
> +
> +       for (i=0; i<10; i++) {
> +               err = psci_ops.affinity_info(cpu_logical_map(cpu), 0);
> +
> +               if (err == PSCI_AFFINITY_INFO_RET_OFF)
> +                       return 1;
> +
> +               msleep(10);
> +               pr_info("Retrying again to check for CPU kill\n");
> +       }
> +
> +       pr_err("psci: Cannot kill CPU:%d, psci ret val: %d\n",
> +                       cpu, err);
> +       /* Make platform_cpu_kill() fail. */
> +       return 0;
> +}
> +
>  #endif
>
>  bool __init psci_smp_available(void)
> @@ -78,5 +109,6 @@ struct smp_operations __initdata psci_smp_ops = {
>         .smp_boot_secondary     = psci_boot_secondary,
>  #ifdef CONFIG_HOTPLUG_CPU
>         .cpu_die                = psci_cpu_die,
> +       .cpu_kill               = psci_cpu_kill,
>  #endif
>  };
> diff --git a/include/uapi/linux/psci.h b/include/uapi/linux/psci.h
> index a4136c3..857209b 100644
> --- a/include/uapi/linux/psci.h
> +++ b/include/uapi/linux/psci.h
> @@ -74,4 +74,9 @@
>  #define PSCI_RET_NOT_PRESENT                   -7
>  #define PSCI_RET_DISABLED                      -8
>
> +/* Return values from the PSCI_ID_AFFINITY_INFO Function. */
> +#define PSCI_AFFINITY_INFO_RET_ON                      0
> +#define PSCI_AFFINITY_INFO_RET_OFF                     1
> +#define PSCI_AFFINITY_INFO_RET_ON_PENDING      2

I have already added this return values in v10 patchset for PSCI v0.2
emulation for KVM ARM/ARM64.
(http://www.spinics.net/lists/kvm-arm/msg09062.html)

Please rebase your patch against that.

> +
>  #endif /* _UAPI_LINUX_PSCI_H */
> --
> 1.8.3.2
>

Regards,
Anup