Re: [PATCH 3/5] x86: Unify x86_32 and x86_64 play_dead into one function

[Jeremy Fitzhardinge <jeremy@goop.org>]

Alex Nixon wrote:
> Add the new play_dead into smpboot.c, as it fits more cleanly in there alongside other CONFIG_HOTPLUG functions.
> Separate out the common code into its own function.
>   

Unfortunately this breaks with !CONFIG_SMP.  The fix is a bit awkward,
because the right place to fix it is in asm-x86/smp.h, but that isn't
included by linux/smp.h when CONFIG_SMP isn't set.

    J
> Signed-off-by: Alex Nixon <alex.nixon@citrix.com>
> Cc: Jeremy Fitzhardinge <jeremy@goop.org>
> Cc: Ingo Molnar <mingo@elte.hu>
> ---
>  arch/x86/kernel/process_32.c |   32 --------------------------------
>  arch/x86/kernel/process_64.c |   23 -----------------------
>  arch/x86/kernel/smpboot.c    |   29 +++++++++++++++++++++++++++++
>  include/asm-x86/smp.h        |    1 +
>  4 files changed, 30 insertions(+), 55 deletions(-)
>
> diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
> index c4abfab..aff137c 100644
> --- a/arch/x86/kernel/process_32.c
> +++ b/arch/x86/kernel/process_32.c
> @@ -74,38 +74,6 @@ unsigned long thread_saved_pc(struct task_struct *tsk)
>  	return ((unsigned long *)tsk->thread.sp)[3];
>  }
>  
> -#ifdef CONFIG_HOTPLUG_CPU
> -#include <asm/nmi.h>
> -
> -/* We don't actually take CPU down, just spin without interrupts. */
> -void native_play_dead(void)
> -{
> -	int cpu = raw_smp_processor_id();
> -
> -	idle_task_exit();
> -
> -	reset_lazy_tlbstate();
> -
> -	irq_ctx_exit(cpu);
> -
> -	mb();
> -	/* Ack it */
> -	__get_cpu_var(cpu_state) = CPU_DEAD;
> -
> -	/*
> -	 * With physical CPU hotplug, we should halt the cpu
> -	 */
> -	local_irq_disable();
> -	/* mask all interrupts, flush any and all caches, and halt */
> -	wbinvd_halt();
> -}
> -#else
> -void native_play_dead(void)
> -{
> -	BUG();
> -}
> -#endif /* CONFIG_HOTPLUG_CPU */
> -
>  /*
>   * The idle thread. There's no useful work to be
>   * done, so just try to conserve power and have a
> diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
> index 1cca50c..b2bab8e 100644
> --- a/arch/x86/kernel/process_64.c
> +++ b/arch/x86/kernel/process_64.c
> @@ -87,29 +87,6 @@ void exit_idle(void)
>  	__exit_idle();
>  }
>  
> -#ifdef CONFIG_HOTPLUG_CPU
> -DECLARE_PER_CPU(int, cpu_state);
> -
> -#include <linux/nmi.h>
> -/* We halt the CPU with physical CPU hotplug */
> -void native_play_dead(void)
> -{
> -	idle_task_exit();
> -	mb();
> -	/* Ack it */
> -	__get_cpu_var(cpu_state) = CPU_DEAD;
> -
> -	local_irq_disable();
> -	/* mask all interrupts, flush any and all caches, and halt */
> -	wbinvd_halt();
> -}
> -#else
> -void native_play_dead(void)
> -{
> -	BUG();
> -}
> -#endif /* CONFIG_HOTPLUG_CPU */
> -
>  /*
>   * The idle thread. There's no useful work to be
>   * done, so just try to conserve power and have a
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index c6832ca..58d8c6c 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -1399,6 +1399,29 @@ void native_cpu_die(unsigned int cpu)
>  	}
>  	printk(KERN_ERR "CPU %u didn't die...\n", cpu);
>  }
> +
> +void play_dead_common(void)
> +{
> +	idle_task_exit();
> +	reset_lazy_tlbstate();
> +	irq_ctx_exit(raw_smp_processor_id());
> +
> +	mb();
> +	/* Ack it */
> +	__get_cpu_var(cpu_state) = CPU_DEAD;
> +
> +	/*
> +	 * With physical CPU hotplug, we should halt the cpu
> +	 */
> +	local_irq_disable();
> +}
> +
> +void native_play_dead(void)
> +{
> +	play_dead_common();
> +	wbinvd_halt();
> +}
> +
>  #else /* ... !CONFIG_HOTPLUG_CPU */
>  int native_cpu_disable(void)
>  {
> @@ -1410,4 +1433,10 @@ void native_cpu_die(unsigned int cpu)
>  	/* We said "no" in __cpu_disable */
>  	BUG();
>  }
> +
> +void native_play_dead(void)
> +{
> +	BUG();
> +}
> +
>  #endif
> diff --git a/include/asm-x86/smp.h b/include/asm-x86/smp.h
> index dba14d3..95b28c1 100644
> --- a/include/asm-x86/smp.h
> +++ b/include/asm-x86/smp.h
> @@ -135,6 +135,7 @@ int native_cpu_up(unsigned int cpunum);
>  int native_cpu_disable(void);
>  void native_cpu_die(unsigned int cpu);
>  void native_play_dead(void);
> +void play_dead_common(void);
>  
>  void native_send_call_func_ipi(cpumask_t mask);
>  void native_send_call_func_single_ipi(int cpu);
>