Re: [Linaro-acpi] [PATCH v8 3/3] ARM: Check if a CPU has gone offline

Hi Ashwin,

On 26 April 2014 01:18, Ashwin Chaugule ashwin.chaugule@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@linaro.org Reviewed-by: Rob Herring robh@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