linux的init/Main.c
{
char * command_line;
extern struct kernel_param __start___param[], __stop___param[];
smp_setup_processor_id();
/*
* Need to run as early as possible, to initialize the
* lockdep hash:
*/
unwind_init();
lockdep_init();
debug_objects_early_init();
cgroup_init_early();
local_irq_disable();
early_boot_irqs_off();
early_init_irq_lock_class();
/*
* Interrupts are still disabled. Do necessary setups, then
* enable them
*/
lock_kernel();
tick_init();
boot_cpu_init();
page_address_init();
printk(KERN_NOTICE);
printk(linux_banner);
setup_arch(&command_line);
mm_init_owner(&init_mm, &init_task);
setup_command_line(command_line);
unwind_setup();
setup_per_cpu_areas();
setup_nr_cpu_ids();
smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */
/*
* 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();
/*
* Disable preemption – early bootup scheduling is extremely
* fragile until we cpu_idle() for the first time.
*/
preempt_disable();
build_all_zonelists();
page_alloc_init();
printk(KERN_NOTICE “Kernel command line: %s\n”, boot_command_line);
parse_early_param();
parse_args(“Booting kernel”, static_command_line, __start___param,
__stop___param – __start___param,
&unknown_bootoption);
if (!irqs_disabled()) {
printk(KERN_WARNING “start_kernel(): bug: interrupts were ”
“enabled *very* early, fixing it\n”);
local_irq_disable();
}
sort_main_extable();
trap_init();
rcu_init();
init_IRQ();
pidhash_init();
init_timers();
hrtimers_init();
softirq_init();
timekeeping_init();
time_init();
sched_clock_init();
profile_init();
if (!irqs_disabled())
printk(“start_kernel(): bug: interrupts were enabled early\n”);
early_boot_irqs_on();
local_irq_enable();
/*
* 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();
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
vmalloc_init();
vfs_caches_init_early();
cpuset_init_early();
page_cgroup_init();
mem_init();
enable_debug_pagealloc();
cpu_hotplug_init();
kmem_cache_init();
debug_objects_mem_init();
idr_init_cache();
setup_per_cpu_pageset();
numa_policy_init();
if (late_time_init)
late_time_init();
calibrate_delay();
pidmap_init();
pgtable_cache_init();
prio_tree_init();
anon_vma_init();
#ifdef CONFIG_X86
if (efi_enabled)
efi_enter_virtual_mode();
#endif
thread_info_cache_init();
fork_init(num_physpages);
proc_caches_init();
buffer_init();
key_init();
security_init();
vfs_caches_init(num_physpages);
radix_tree_init();
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 */
ftrace_init();
/* Do the rest non-__init’ed, we’re now alive */
rest_init(); /*进入剩余初始化，就是初始化init进程*/
}
__releases(kernel_lock)
{
int pid;
kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND); /*启动init进程，入口为kernel_init()。*/
numa_default_policy();
pid = kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES); /*启动kthread进程，入口为kthreadd，定义在kthread.c。它将会对每个cpu建立很多设备的内核子进程*/
kthreadd_task = find_task_by_pid_ns(pid, &init_pid_ns);
unlock_kernel();
/*
* The boot idle thread must execute schedule()
* at least once to get things moving:
*/
init_idle_bootup_task(current);
preempt_enable_no_resched();
schedule();
preempt_disable();
/* Call into cpu_idle with preempt disabled */
cpu_idle(); /*调用cpu_idle，即调用pm_idle，最终调用cpuidle_idle_call。*/
}
{
lock_kernel();
/*
* init can run on any cpu.
*/
set_cpus_allowed_ptr(current, CPU_MASK_ALL_PTR);
/*
* Tell the world that we’re going to be the grim
* reaper of innocent orphaned children.
*
* We don’t want people to have to make incorrect
* assumptions about where in the task array this
* can be found.
*/
init_pid_ns.child_reaper = current;
cad_pid = task_pid(current);
smp_prepare_cpus(setup_max_cpus);
do_pre_smp_initcalls();
start_boot_trace();
smp_init();
sched_init_smp();
cpuset_init_smp();
do_basic_setup();
/*
* check if there is an early userspace init. If yes, let it do all
* the work
*/
if (!ramdisk_execute_command)
ramdisk_execute_command = “/init”;
if (sys_access((const char __user *) ramdisk_execute_command, 0) != 0) {
ramdisk_execute_command = NULL;
prepare_namespace();
}
/*
* Ok, we have completed the initial bootup, and
* we’re essentially up and running. Get rid of the
* initmem segments and start the user-mode stuff..
*/
stop_boot_trace();
init_post();
return 0;
}
{
free_initmem();
unlock_kernel();
mark_rodata_ro();
system_state = SYSTEM_RUNNING;
numa_default_policy();
if (sys_open((const char __user *) “/dev/console”, O_RDWR, 0) < 0)
printk(KERN_WARNING “Warning: unable to open an initial console.\n”);
(void) sys_dup(0);
(void) sys_dup(0);
current->signal->flags |= SIGNAL_UNKILLABLE;
if (ramdisk_execute_command) {
run_init_process(ramdisk_execute_command);
printk(KERN_WARNING “Failed to execute %s\n”,
ramdisk_execute_command);
}
/*
* We try each of these until one succeeds.
*
* The Bourne shell can be used instead of init if we are
* trying to recover a really broken machine.
*/
if (execute_command) {
run_init_process(execute_command);
printk(KERN_WARNING “Failed to execute %s. Attempting ”
“defaults…\n”, execute_command);
}
run_init_process(“/sbin/init”);
run_init_process(“/etc/init”);
run_init_process(“/bin/init”);
run_init_process(“/bin/sh”);
panic(“No init found. Try passing init= option to kernel.”);
}