Re: [Xen-devel] [PATCH v2] xen/smp: Use die_complete completion when taking CPU down

[David Vrabel <david.vrabel@citrix.com>]

On 16/10/14 17:47, Boris Ostrovsky wrote:
> Commit 2ed53c0d6cc9 ("x86/smpboot: Speed up suspend/resume by avoiding
> 100ms sleep for CPU offline during S3") introduced completions to CPU
> offlining process. These completions are not initialized on Xen kernels
> causing a panic in play_dead_common().
> 
> Move handling of die_complete into common routines to make them
> available to Xen guests.
> 
> (Also, while at it, move these routines as well as die_complete under
> ifdef CONFIG_HOTPLUG_CPU)

Reviewed-by: David Vrabel <david.vrabel@citrix.com>

I can merge this via the Xen tree if that is preferred.

David

> --- a/arch/x86/include/asm/smp.h
> +++ b/arch/x86/include/asm/smp.h
> @@ -149,7 +149,11 @@ static inline void arch_send_call_function_ipi_mask(const struct cpumask *mask)
>  	smp_ops.send_call_func_ipi(mask);
>  }
>  
> +#ifdef CONFIG_HOTPLUG_CPU
>  void cpu_disable_common(void);
> +void cpu_die_common(unsigned int cpu);
> +void play_dead_common(void);
> +#endif
>  void native_smp_prepare_boot_cpu(void);
>  void native_smp_prepare_cpus(unsigned int max_cpus);
>  void native_smp_cpus_done(unsigned int max_cpus);
> @@ -157,7 +161,6 @@ int native_cpu_up(unsigned int cpunum, struct task_struct *tidle);
>  int native_cpu_disable(void);
>  void native_cpu_die(unsigned int cpu);
>  void native_play_dead(void);
> -void play_dead_common(void);
>  void wbinvd_on_cpu(int cpu);
>  int wbinvd_on_all_cpus(void);
>  
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index 2d5200e..6fe0fc1 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -102,7 +102,9 @@ DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_llc_shared_map);
>  DEFINE_PER_CPU_SHARED_ALIGNED(struct cpuinfo_x86, cpu_info);
>  EXPORT_PER_CPU_SYMBOL(cpu_info);
>  
> +#ifdef CONFIG_HOTPLUG_CPU
>  static DEFINE_PER_CPU(struct completion, die_complete);
> +#endif
>  
>  atomic_t init_deasserted;
>  
> @@ -1309,6 +1311,8 @@ void cpu_disable_common(void)
>  {
>  	int cpu = smp_processor_id();
>  
> +	init_completion(&per_cpu(die_complete, smp_processor_id()));
> +
>  	remove_siblinginfo(cpu);
>  
>  	/* It's now safe to remove this processor from the online map */
> @@ -1327,16 +1331,21 @@ int native_cpu_disable(void)
>  		return ret;
>  
>  	clear_local_APIC();
> -	init_completion(&per_cpu(die_complete, smp_processor_id()));
>  	cpu_disable_common();
>  
>  	return 0;
>  }
>  
> +void cpu_die_common(unsigned int cpu)
> +{
> +	wait_for_completion_timeout(&per_cpu(die_complete, cpu), HZ);
> +}
> +
>  void native_cpu_die(unsigned int cpu)
>  {
>  	/* We don't do anything here: idle task is faking death itself. */
> -	wait_for_completion_timeout(&per_cpu(die_complete, cpu), HZ);
> +
> +	cpu_die_common(cpu);
>  
>  	/* They ack this in play_dead() by setting CPU_DEAD */
>  	if (per_cpu(cpu_state, cpu) == CPU_DEAD) {
> diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
> index 8650cdb..4c071ae 100644
> --- a/arch/x86/xen/smp.c
> +++ b/arch/x86/xen/smp.c
> @@ -510,6 +510,9 @@ static void xen_cpu_die(unsigned int cpu)
>  		current->state = TASK_UNINTERRUPTIBLE;
>  		schedule_timeout(HZ/10);
>  	}
> +
> +	cpu_die_common(cpu);
> +
>  	xen_smp_intr_free(cpu);
>  	xen_uninit_lock_cpu(cpu);
>  	xen_teardown_timer(cpu);
>