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a71c8bc5df
CONFIG_DEBUG_HOTPLUG_CPU0 is for debugging the CPU0 hotplug feature. The switch offlines CPU0 as soon as possible and boots userspace up with CPU0 offlined. User can online CPU0 back after boot time. The default value of the switch is off. To debug CPU0 hotplug, you need to enable CPU0 offline/online feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during compilation or giving cpu0_hotplug kernel parameter at boot. It's safe and early place to take down CPU0 after all hotplug notifiers are installed and SMP is booted. Please note that some applications or drivers, e.g. some versions of udevd, during boot time may put CPU0 online again in this CPU0 hotplug debug mode. In this debug mode, setup_local_APIC() may report a warning on max_loops<=0 when CPU0 is onlined back after boot time. This is because pending interrupt in IRR can not move to ISR. The warning is not CPU0 specfic and it can happen on other CPUs as well. It is harmless except the first CPU0 online takes a bit longer time. And so this debug mode is useful to expose this issue. I'll send a seperate patch to fix this generic warning issue. Signed-off-by: Fenghua Yu <fenghua.yu@intel.com> Link: http://lkml.kernel.org/r/1352835171-3958-15-git-send-email-fenghua.yu@intel.com Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
42 lines
857 B
C
42 lines
857 B
C
#ifndef _ASM_X86_CPU_H
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#define _ASM_X86_CPU_H
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#include <linux/device.h>
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#include <linux/cpu.h>
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#include <linux/topology.h>
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#include <linux/nodemask.h>
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#include <linux/percpu.h>
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#ifdef CONFIG_SMP
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extern void prefill_possible_map(void);
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#else /* CONFIG_SMP */
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static inline void prefill_possible_map(void) {}
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#define cpu_physical_id(cpu) boot_cpu_physical_apicid
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#define safe_smp_processor_id() 0
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#define stack_smp_processor_id() 0
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#endif /* CONFIG_SMP */
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struct x86_cpu {
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struct cpu cpu;
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};
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#ifdef CONFIG_HOTPLUG_CPU
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extern int arch_register_cpu(int num);
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extern void arch_unregister_cpu(int);
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extern void __cpuinit start_cpu0(void);
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#ifdef CONFIG_DEBUG_HOTPLUG_CPU0
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extern int _debug_hotplug_cpu(int cpu, int action);
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#endif
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#endif
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DECLARE_PER_CPU(int, cpu_state);
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int mwait_usable(const struct cpuinfo_x86 *);
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#endif /* _ASM_X86_CPU_H */
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