mirror of https://gitee.com/openkylin/linux.git
arm64: make cpu number a percpu variable
In the absence of CONFIG_THREAD_INFO_IN_TASK, core code maintains thread_info::cpu, and low-level architecture code can access this to build raw_smp_processor_id(). With CONFIG_THREAD_INFO_IN_TASK, core code maintains task_struct::cpu, which for reasons of hte header soup is not accessible to low-level arch code. Instead, we can maintain a percpu variable containing the cpu number. For both the old and new implementation of raw_smp_processor_id(), we read a syreg into a GPR, add an offset, and load the result. As the offset is now larger, it may not be folded into the load, but otherwise the assembly shouldn't change much. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Tested-by: Laura Abbott <labbott@redhat.com> Cc: James Morse <james.morse@arm.com> Cc: Suzuki K Poulose <suzuki.poulose@arm.com> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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@ -29,11 +29,20 @@
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#ifndef __ASSEMBLY__
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#include <asm/percpu.h>
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#include <linux/threads.h>
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#include <linux/cpumask.h>
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#include <linux/thread_info.h>
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#define raw_smp_processor_id() (current_thread_info()->cpu)
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DECLARE_PER_CPU_READ_MOSTLY(int, cpu_number);
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/*
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* We don't use this_cpu_read(cpu_number) as that has implicit writes to
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* preempt_count, and associated (compiler) barriers, that we'd like to avoid
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* the expense of. If we're preemptible, the value can be stale at use anyway.
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*/
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#define raw_smp_processor_id() (*this_cpu_ptr(&cpu_number))
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struct seq_file;
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@ -58,6 +58,9 @@
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#define CREATE_TRACE_POINTS
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#include <trace/events/ipi.h>
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DEFINE_PER_CPU_READ_MOSTLY(int, cpu_number);
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EXPORT_PER_CPU_SYMBOL(cpu_number);
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/*
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* as from 2.5, kernels no longer have an init_tasks structure
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* so we need some other way of telling a new secondary core
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@ -719,6 +722,8 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
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*/
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for_each_possible_cpu(cpu) {
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per_cpu(cpu_number, cpu) = cpu;
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if (cpu == smp_processor_id())
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continue;
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