Re: [PATCH] kernel/cpu.c: create a CPU_STARTING cpu_chain notifier

From: Paul E. McKenney
Date: Mon Sep 08 2008 - 14:51:07 EST

On Sun, Sep 07, 2008 at 04:57:22PM +0200, Manfred Spraul wrote:
> 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

> Signed-Off-By: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
> ---
> 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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