asmlinkage void __init start_kernel(void)

{

char * command_line;

extern const struct kernel_param __start___param[], __stop___param[];

smp_setup_processor_id();//返回启动的CPU的ID号，如为单核则什么也不做

/*

* Need to run as early as possible, to initialize the

* lockdep hash:

*/

lockdep_init();

debug_objects_early_init();

/*

* Set up the the initial canary ASAP:

*/

boot_init_stack_canary();

cgroup_init_early();

local_irq_disable();//关闭当前CPU的中断

early_boot_irqs_disabled = true;

/*

* Interrupts are still disabled. Do necessary setups, then

* enable them

*/

tick_init();

boot_cpu_init();

page_address_init();//初始化页地址，使用链表将其链接起来

printk(KERN_NOTICE "%s", linux_banner);//打印内核版本信息

setup_arch(&command_line);//设置体系结构，由内核根目录的Makefile决定

mm_init_owner(&init_mm, &init_task);

mm_init_cpumask(&init_mm);

setup_command_line(command_line);

setup_nr_cpu_ids();

setup_per_cpu_areas();

smp_prepare_boot_cpu();      /* arch-specific boot-cpu hooks */

build_all_zonelists(NULL);

page_alloc_init();

printk(KERN_NOTICE "Kernel command line: %s\n", boot_command_line);//打印命令行信息

parse_early_param();//解析内核选项

parse_args("Booting kernel", static_command_line, __start___param,

__stop___param - __start___param,

&unknown_bootoption);

/*

* These use large bootmem allocations and must precede

* kmem_cache_init()

*/

setup_log_buf(0);

pidhash_init();

vfs_caches_init_early();

sort_main_extable();

trap_init();

mm_init();

/*

* Set up the scheduler prior starting any interrupts (such as the

* timer interrupt). Full topology setup happens at smp_init()

* time - but meanwhile we still have a functioning scheduler.

*/

sched_init();//进程调度器初始化

/*

* Disable preemption - early bootup scheduling is extremely

* fragile until we cpu_idle() for the first time.

*/

preempt_disable();//禁止内核抢占

if (!irqs_disabled()) {//检查中断是否已经打开，如果已经打开，则关闭中断

printk(KERN_WARNING "start_kernel(): bug: interrupts were "

"enabled *very* early, fixing it\n");

local_irq_disable();

}

idr_init_cache();

perf_event_init();

rcu_init();//初始化RCU(Read-Copy Update)机制

radix_tree_init();

/* init some links before init_ISA_irqs() */

early_irq_init();

init_IRQ();//中断向量初始化

prio_tree_init();

init_timers();//初始化定时器相关的数据结构

hrtimers_init();//对高精度时钟进行初始化

softirq_init();//初始化tasklet_softirq和hi_softirq

timekeeping_init();

time_init();//初始化系统时钟源

profile_init();//对内核的profile(一个内核性能调式工具)功能进行初始化

call_function_init();

if (!irqs_disabled())

printk(KERN_CRIT "start_kernel(): bug: interrupts were "

"enabled early\n");

early_boot_irqs_disabled = false;

local_irq_enable();

/* Interrupts are enabled now so all GFP allocations are safe. */

gfp_allowed_mask = __GFP_BITS_MASK;

kmem_cache_init_late();

/*

* HACK ALERT! This is early. We're enabling the console before

* we've done PCI setups etc, and console_init() must be aware of

* this. But we do want output early, in case something goes wrong.

*/

console_init();// 初始化控制台以显示printk的内容，在此之前调用的printk只是把数据存到缓冲区里

if (panic_later)

panic(panic_later, panic_param);

lockdep_info();

/*

* Need to run this when irqs are enabled, because it wants

* to self-test [hard/soft]-irqs on/off lock inversion bugs

* too:

*/

locking_selftest();

#ifdef CONFIG_BLK_DEV_INITRD

if (initrd_start && !initrd_below_start_ok &&

page_to_pfn(virt_to_page((void *)initrd_start)) < min_low_pfn) {

printk(KERN_CRIT "initrd overwritten (0x%08lx < 0x%08lx) - "

"disabling it.\n",

page_to_pfn(virt_to_page((void *)initrd_start)),

min_low_pfn);

initrd_start = 0;

}

#endif

page_cgroup_init();

enable_debug_pagealloc();

debug_objects_mem_init();

kmemleak_init();

setup_per_cpu_pageset();

numa_policy_init();

if (late_time_init)

late_time_init();

sched_clock_init();

calibrate_delay();

pidmap_init();

anon_vma_init();

#ifdef CONFIG_X86

if (efi_enabled)

efi_enter_virtual_mode();

#endif

thread_info_cache_init();

cred_init();

fork_init(totalram_pages);

proc_caches_init();

buffer_init();

key_init();

security_init();

dbg_late_init();

vfs_caches_init(totalram_pages);//虚拟文件系统的初始化

signals_init();

/* rootfs populating might need page-writeback */

page_writeback_init();

#ifdef CONFIG_PROC_FS

proc_root_init();

#endif

cgroup_init();

cpuset_init();

taskstats_init_early();

delayacct_init();

check_bugs();

acpi_early_init(); /* before LAPIC and SMP init */

sfi_init_late();

ftrace_init();

/* Do the rest non-__init'ed, we're now alive */

rest_init();

}