On Sun, Sep 07, 2008 at 04:57:22PM +0200, Manfred Spraul wrote:
quoted text
> Right now, there is no notifier that is called on a new cpu, before the new
> cpu begins processing interrupts/softirqs.
> Various kernel function would need that notification, e.g. kvm works around
> by calling smp_call_function_single(), rcu polls cpu_online_map.
> 
> The patch adds a CPU_STARTING notification. It also adds a helper function
> that sends the message to all cpu_chain handlers.
> 
> Tested on x86-64.
> All other archs are untested. Especially on sparc, I'm not sure if I got
> it right.

Very cool!!!  I will see if using this and your earlier patch allows me
to dump my code that checks cpu_online_map.

							Thanx, Paul

quoted text
> Signed-Off-By: Manfred Spraul <manfred@colorfullife.com>
> ---
>  arch/alpha/kernel/smp.c             |    3 +++
>  arch/arm/kernel/smp.c               |    1 +
>  arch/cris/arch-v32/kernel/smp.c     |    1 +
>  arch/ia64/kernel/smpboot.c          |    1 +
>  arch/m32r/kernel/smpboot.c          |    2 ++
>  arch/mips/kernel/smp.c              |    2 ++
>  arch/powerpc/kernel/smp.c           |    1 +
>  arch/s390/kernel/smp.c              |    2 ++
>  arch/sh/kernel/smp.c                |    2 ++
>  arch/sparc/kernel/sun4d_smp.c       |    1 +
>  arch/sparc/kernel/sun4m_smp.c       |    2 ++
>  arch/um/kernel/smp.c                |    1 +
>  arch/x86/kernel/smpboot.c           |    1 +
>  arch/x86/mach-voyager/voyager_smp.c |    2 ++
>  include/linux/cpu.h                 |    1 +
>  include/linux/notifier.h            |   10 +++++++++-
>  kernel/cpu.c                        |   20 +++++++++++++++++++-
>  17 files changed, 51 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/alpha/kernel/smp.c b/arch/alpha/kernel/smp.c
> index 83df541..06b6fda 100644
> --- a/arch/alpha/kernel/smp.c
> +++ b/arch/alpha/kernel/smp.c
> @@ -149,6 +149,9 @@ smp_callin(void)
>  	atomic_inc(&init_mm.mm_count);
>  	current->active_mm = &init_mm;
> 
> +	/* inform the notifiers about the new cpu */
> +	notify_cpu_starting(cpuid);
> +
>  	/* Must have completely accurate bogos.  */
>  	local_irq_enable();
> 
> diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
> index e9842f6..e42a749 100644
> --- a/arch/arm/kernel/smp.c
> +++ b/arch/arm/kernel/smp.c
> @@ -277,6 +277,7 @@ asmlinkage void __cpuinit secondary_start_kernel(void)
>  	/*
>  	 * Enable local interrupts.
>  	 */
> +	notify_cpu_starting(cpu);
>  	local_irq_enable();
>  	local_fiq_enable();
> 
> diff --git a/arch/cris/arch-v32/kernel/smp.c b/arch/cris/arch-v32/kernel/smp.c
> index 952a24b..52e16c6 100644
> --- a/arch/cris/arch-v32/kernel/smp.c
> +++ b/arch/cris/arch-v32/kernel/smp.c
> @@ -178,6 +178,7 @@ void __init smp_callin(void)
>  	unmask_irq(IPI_INTR_VECT);
>  	unmask_irq(TIMER0_INTR_VECT);
>  	preempt_disable();
> +	notify_cpu_starting(cpu);
>  	local_irq_enable();
> 
>  	cpu_set(cpu, cpu_online_map);
> diff --git a/arch/ia64/kernel/smpboot.c b/arch/ia64/kernel/smpboot.c
> index bcea81e..333b58f 100644
> --- a/arch/ia64/kernel/smpboot.c
> +++ b/arch/ia64/kernel/smpboot.c
> @@ -401,6 +401,7 @@ smp_callin (void)
>  	spin_lock(&vector_lock);
>  	/* Setup the per cpu irq handling data structures */
>  	__setup_vector_irq(cpuid);
> +	notify_cpu_starting(cpuid);
>  	cpu_set(cpuid, cpu_online_map);
>  	per_cpu(cpu_state, cpuid) = CPU_ONLINE;
>  	spin_unlock(&vector_lock);
> diff --git a/arch/m32r/kernel/smpboot.c b/arch/m32r/kernel/smpboot.c
> index 2c03ac1..fc29948 100644
> --- a/arch/m32r/kernel/smpboot.c
> +++ b/arch/m32r/kernel/smpboot.c
> @@ -498,6 +498,8 @@ static void __init smp_online(void)
>  {
>  	int cpu_id = smp_processor_id();
> 
> +	notify_cpu_starting(cpu_id);
> +
>  	local_irq_enable();
> 
>  	/* Get our bogomips. */
> diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c
> index 4410f17..7b59cfb 100644
> --- a/arch/mips/kernel/smp.c
> +++ b/arch/mips/kernel/smp.c
> @@ -121,6 +121,8 @@ asmlinkage __cpuinit void start_secondary(void)
>  	cpu = smp_processor_id();
>  	cpu_data[cpu].udelay_val = loops_per_jiffy;
> 
> +	notify_cpu_starting(cpu);
> +
>  	mp_ops->smp_finish();
>  	set_cpu_sibling_map(cpu);
> 
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index 5337ca7..c27b10a 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -453,6 +453,7 @@ int __devinit start_secondary(void *unused)
>  	secondary_cpu_time_init();
> 
>  	ipi_call_lock();
> +	notify_cpu_starting(cpu);
>  	cpu_set(cpu, cpu_online_map);
>  	/* Update sibling maps */
>  	base = cpu_first_thread_in_core(cpu);
> diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
> index 00b9b4d..9e8b1f9 100644
> --- a/arch/s390/kernel/smp.c
> +++ b/arch/s390/kernel/smp.c
> @@ -585,6 +585,8 @@ int __cpuinit start_secondary(void *cpuvoid)
>  	/* Enable pfault pseudo page faults on this cpu. */
>  	pfault_init();
> 
> +	/* call cpu notifiers */
> +	notify_cpu_starting(smp_processor_id());
>  	/* Mark this cpu as online */
>  	spin_lock(&call_lock);
>  	cpu_set(smp_processor_id(), cpu_online_map);
> diff --git a/arch/sh/kernel/smp.c b/arch/sh/kernel/smp.c
> index 60c5084..001778f 100644
> --- a/arch/sh/kernel/smp.c
> +++ b/arch/sh/kernel/smp.c
> @@ -82,6 +82,8 @@ asmlinkage void __cpuinit start_secondary(void)
> 
>  	preempt_disable();
> 
> +	notify_cpu_starting(smp_processor_id());
> +
>  	local_irq_enable();
> 
>  	calibrate_delay();
> diff --git a/arch/sparc/kernel/sun4d_smp.c b/arch/sparc/kernel/sun4d_smp.c
> index 6959640..446767e 100644
> --- a/arch/sparc/kernel/sun4d_smp.c
> +++ b/arch/sparc/kernel/sun4d_smp.c
> @@ -88,6 +88,7 @@ void __init smp4d_callin(void)
>  	local_flush_cache_all();
>  	local_flush_tlb_all();
> 
> +	notify_cpu_starting(cpuid);
>  	/*
>  	 * Unblock the master CPU _only_ when the scheduler state
>  	 * of all secondary CPUs will be up-to-date, so after
> diff --git a/arch/sparc/kernel/sun4m_smp.c b/arch/sparc/kernel/sun4m_smp.c
> index a14a76a..9964890 100644
> --- a/arch/sparc/kernel/sun4m_smp.c
> +++ b/arch/sparc/kernel/sun4m_smp.c
> @@ -71,6 +71,8 @@ void __cpuinit smp4m_callin(void)
>  	local_flush_cache_all();
>  	local_flush_tlb_all();
> 
> +	notify_cpu_starting(cpuid);
> +
>  	/* Get our local ticker going. */
>  	smp_setup_percpu_timer();
> 
> diff --git a/arch/um/kernel/smp.c b/arch/um/kernel/smp.c
> index be2d50c..0457721 100644
> --- a/arch/um/kernel/smp.c
> +++ b/arch/um/kernel/smp.c
> @@ -85,6 +85,7 @@ static int idle_proc(void *cpup)
>  	while (!cpu_isset(cpu, smp_commenced_mask))
>  		cpu_relax();
> 
> +	notify_cpu_starting(cpu);
>  	cpu_set(cpu, cpu_online_map);
>  	default_idle();
>  	return 0;
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index 7985c5b..0b8261c 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -257,6 +257,7 @@ static void __cpuinit smp_callin(void)
>  	end_local_APIC_setup();
>  	map_cpu_to_logical_apicid();
> 
> +	notify_cpu_starting(cpuid);
>  	/*
>  	 * Get our bogomips.
>  	 *
> diff --git a/arch/x86/mach-voyager/voyager_smp.c b/arch/x86/mach-voyager/voyager_smp.c
> index ee0fba0..199a5f4 100644
> --- a/arch/x86/mach-voyager/voyager_smp.c
> +++ b/arch/x86/mach-voyager/voyager_smp.c
> @@ -448,6 +448,8 @@ static void __init start_secondary(void *unused)
> 
>  	VDEBUG(("VOYAGER SMP: CPU%d, stack at about %p\n", cpuid, &cpuid));
> 
> +	notify_cpu_starting(cpuid);
> +
>  	/* enable interrupts */
>  	local_irq_enable();
> 
> diff --git a/include/linux/cpu.h b/include/linux/cpu.h
> index d7faf88..c2747ac 100644
> --- a/include/linux/cpu.h
> +++ b/include/linux/cpu.h
> @@ -69,6 +69,7 @@ static inline void unregister_cpu_notifier(struct notifier_block *nb)
>  #endif
> 
>  int cpu_up(unsigned int cpu);
> +void notify_cpu_starting(unsigned int cpu);
>  extern void cpu_hotplug_init(void);
>  extern void cpu_maps_update_begin(void);
>  extern void cpu_maps_update_done(void);
> diff --git a/include/linux/notifier.h b/include/linux/notifier.h
> index da2698b..8e47661 100644
> --- a/include/linux/notifier.h
> +++ b/include/linux/notifier.h
> @@ -213,9 +213,16 @@ static inline int notifier_to_errno(int ret)
>  #define CPU_DOWN_FAILED		0x0006 /* CPU (unsigned)v NOT going down */
>  #define CPU_DEAD		0x0007 /* CPU (unsigned)v dead */
>  #define CPU_DYING		0x0008 /* CPU (unsigned)v not running any task,
> -				        * not handling interrupts, soon dead */
> +				        * not handling interrupts, soon dead.
> +				        * Called on the dying cpu, interrupts
> +				        * are already disabled. Must not
> +				        * sleep, must not fail */
>  #define CPU_POST_DEAD		0x0009 /* CPU (unsigned)v dead, cpu_hotplug
>  					* lock is dropped */
> +#define CPU_STARTING		0x000A /* CPU (unsigned)v soon running.
> +					* Called on the new cpu, just before
> +					* enabling interrupts. Must not sleep,
> +					* must not fail */
> 
>  /* Used for CPU hotplug events occuring while tasks are frozen due to a suspend
>   * operation in progress
> @@ -229,6 +236,7 @@ static inline int notifier_to_errno(int ret)
>  #define CPU_DOWN_FAILED_FROZEN	(CPU_DOWN_FAILED | CPU_TASKS_FROZEN)
>  #define CPU_DEAD_FROZEN		(CPU_DEAD | CPU_TASKS_FROZEN)
>  #define CPU_DYING_FROZEN	(CPU_DYING | CPU_TASKS_FROZEN)
> +#define CPU_STARTING_FROZEN	(CPU_STARTING | CPU_TASKS_FROZEN)
> 
>  /* Hibernation and suspend events */
>  #define PM_HIBERNATION_PREPARE	0x0001 /* Going to hibernate */
> diff --git a/kernel/cpu.c b/kernel/cpu.c
> index f17e985..46a8bbd 100644
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -453,6 +453,25 @@ out:
>  }
>  #endif /* CONFIG_PM_SLEEP_SMP */
> 
> +/**
> + * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
> + * @cpu: cpu that just started
> + *
> + * This function calls the cpu_chain notifiers with CPU_STARTING.
> + * It must be called by the arch code on the new cpu, before the new cpu
> + * enables interrupts and before the "boot" cpu returns from __cpu_up().
> + */
> +void notify_cpu_starting(unsigned int cpu)
> +{
> +	unsigned long val = CPU_STARTING;
> +
> +#ifdef CONFIG_PM_SLEEP_SMP
> +	if (cpu_isset(cpu, frozen_cpus))
> +		val = CPU_STARTING_FROZEN;
> +#endif /* CONFIG_PM_SLEEP_SMP */
> +	raw_notifier_call_chain(&cpu_chain, val, (void*)(long)cpu);
> +}
> +
>  #endif /* CONFIG_SMP */
> 
>  /*
> -- 
> 1.5.5.1
--
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