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SubjectRe: [PATCH v7 04/12] Don't offline CPU0 if any PIC irq can not be migrated out of it.
On Thu, Aug 23, 2012 at 05:56:03PM -0700, Fenghua Yu wrote:
> From: Fenghua Yu <fenghua.yu@intel.com>
>
> Change smp_store_cpu_info() to store cpu info for a CPU when it's brought up.
> This includes bringing up CPU0 or AP after it's offline. But don't store cpu
> info when BSP first boots during boot time.
>
> Continue to online CPU0 in native_cpu_up().
>
> Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
> ---
> arch/x86/include/asm/smp.h | 2 +-
> arch/x86/kernel/smpboot.c | 32 +++++++++++---------------------
> 2 files changed, 12 insertions(+), 22 deletions(-)
>
> diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
> index 4f19a15..0be0b29 100644
> --- a/arch/x86/include/asm/smp.h
> +++ b/arch/x86/include/asm/smp.h
> @@ -166,7 +166,7 @@ void native_send_call_func_ipi(const struct cpumask *mask);
> void native_send_call_func_single_ipi(int cpu);
> void x86_idle_thread_init(unsigned int cpu, struct task_struct *idle);
>
> -void smp_store_cpu_info(int id);
> +void smp_store_cpu_info(int id, int store);
> #define cpu_physical_id(cpu) per_cpu(x86_cpu_to_apicid, cpu)
>
> #else /* !CONFIG_SMP */
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index c80a33b..8d0b4ff 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -125,8 +125,8 @@ EXPORT_PER_CPU_SYMBOL(cpu_info);
> atomic_t init_deasserted;
>
> /*
> - * Report back to the Boot Processor.
> - * Running on AP.
> + * Report back to the Boot Processor during boot time or to the caller processor
> + * during CPU online.
> */
> static void __cpuinit smp_callin(void)
> {
> @@ -201,7 +201,7 @@ static void __cpuinit smp_callin(void)
> * Save our processor parameters. Note: this information
> * is needed for clock calibration.
> */
> - smp_store_cpu_info(cpuid);
> + smp_store_cpu_info(cpuid, 1);
>
> /*
> * Get our bogomips.
> @@ -283,14 +283,17 @@ notrace static void __cpuinit start_secondary(void *unused)
> * The bootstrap kernel entry code has set these up. Save them for
> * a given CPU
> */
> -
> -void __cpuinit smp_store_cpu_info(int id)
> +void __cpuinit smp_store_cpu_info(int id, int store)

This usage begs for "bool store".

> {
> struct cpuinfo_x86 *c = &cpu_data(id);
>
> *c = boot_cpu_data;
> c usage->cpu_index = id;
> - if (id != 0)
> + /*
> + * During boot time, CPU0 has this setup already. Save the info when
> + * bringing up AP or offlined CPU0.
> + */
> + if (store)
> identify_secondary_cpu(c);
> }
>
> @@ -795,7 +798,7 @@ int __cpuinit native_cpu_up(unsigned int cpu, struct task_struct *tidle)
>
> pr_debug("++++++++++++++++++++=_---CPU UP %u\n", cpu);
>
> - if (apicid == BAD_APICID || apicid == boot_cpu_physical_apicid ||
> + if (apicid == BAD_APICID ||
> !physid_isset(apicid, phys_cpu_present_map) ||
> !apic->apic_id_valid(apicid)) {

Nothing in the commit message explains this change...

> pr_err("%s: bad cpu %d\n", __func__, cpu);
> @@ -990,7 +993,7 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus)
> /*
> * Setup boot CPU information
> */
> - smp_store_cpu_info(0); /* Final full version of the data */
> + smp_store_cpu_info(0, 0); /* Final full version of the data */
> cpumask_copy(cpu_callin_mask, cpumask_of(0));
> mb();
>
> @@ -1214,19 +1217,6 @@ void cpu_disable_common(void)
>
> int native_cpu_disable(void)
> {
> - int cpu = smp_processor_id();
> -
> - /*
> - * Perhaps use cpufreq to drop frequency, but that could go
> - * into generic code.
> - *
> - * We won't take down the boot processor on i386 due to some
> - * interrupts only being able to be serviced by the BSP.
> - * Especially so if we're not using an IOAPIC -zwane
> - */
> - if (cpu == 0)
> - return -EBUSY;
> -
> clear_local_APIC();
>
> cpu_disable_common();
> --
> 1.7.2
>
> --
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--
Regards/Gruss,
Boris.


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