main.c

Linux的初始化源代码

	for_each_present_cpu(i) {
		if (num_online_cpus() >= max_cpus)
			break;
		if (!cpu_online(i))
			cpu_up(i);
	}

	/* Any cleanup work */
	printk("Brought up %ld CPUs\n", (long)num_online_cpus());
	smp_cpus_done(max_cpus);
#if 0
	/* Get other processors into their bootup holding patterns. */

	smp_threads_ready=1;
	smp_commence();
#endif
}

#endif

/*
 * We need to finalize in a non-__init function or else race conditions
 * between the root thread and the init thread may cause start_kernel to
 * be reaped by free_initmem before the root thread has proceeded to
 * cpu_idle.
 *
 * gcc-3.4 accidentally inlines this function, so use noinline.
 */

static void noinline rest_init(void)
{
	kernel_thread(init, NULL, CLONE_FS | CLONE_SIGHAND);
	numa_default_policy();
	unlock_kernel();
 	cpu_idle();
} 

/* Check for early params. */
static int __init do_early_param(char *param, char *val)
{
	struct obs_kernel_param *p;
	extern struct obs_kernel_param __setup_start, __setup_end;

	for (p = &__setup_start; p < &__setup_end; p++) {
		if (p->early && strcmp(param, p->str) == 0) {
			if (p->setup_func(val) != 0)
				printk(KERN_WARNING
				       "Malformed early option '%s'\n", param);
		}
	}
	/* We accept everything at this stage. */
	return 0;
}

/* Arch code calls this early on, or if not, just before other parsing. */
void __init parse_early_param(void)
{
	static __initdata int done = 0;
	static __initdata char tmp_cmdline[COMMAND_LINE_SIZE];

	if (done)
		return;

	/* All fall through to do_early_param. */
	strlcpy(tmp_cmdline, saved_command_line, COMMAND_LINE_SIZE);
	parse_args("early options", tmp_cmdline, NULL, 0, do_early_param);
	done = 1;
}

/*
 *	Activate the first processor.
 */

asmlinkage void __init start_kernel(void)
{
	char * command_line;
	extern struct kernel_param __start___param[], __stop___param[];
/*
 * Interrupts are still disabled. Do necessary setups, then
 * enable them
 */

	lock_kernel();
	page_address_init();
	printk(linux_banner);
	setup_arch(&command_line);
	setup_per_cpu_areas();

	/*
	 * Mark the boot cpu "online" so that it can call console drivers in
	 * printk() and can access its per-cpu storage.
	 */
	smp_prepare_boot_cpu();

	/*
	 * 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();

	build_all_zonelists();
	page_alloc_init();
	printk("Kernel command line: %s\n", saved_command_line);
	parse_early_param();
	parse_args("Booting kernel", command_line, __start___param,
		   __stop___param - __start___param,
		   &unknown_bootoption);
	sort_main_extable();
	trap_init();
	rcu_init();
	init_IRQ();
	pidhash_init();
	init_timers();
	softirq_init();
	time_init();

	/*
	 * 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);
	profile_init();
	local_irq_enable();
#ifdef CONFIG_BLK_DEV_INITRD
	if (initrd_start && !initrd_below_start_ok &&
			initrd_start < min_low_pfn << PAGE_SHIFT) {
		printk(KERN_CRIT "initrd overwritten (0x%08lx < 0x%08lx) - "
		    "disabling it.\n",initrd_start,min_low_pfn << PAGE_SHIFT);
		initrd_start = 0;
	}
#endif
	vfs_caches_init_early();
	mem_init();
	kmem_cache_init();
	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
	fork_init(num_physpages);
	proc_caches_init();
	buffer_init();
	unnamed_dev_init();
	security_scaffolding_startup();
	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
	check_bugs();

	/* 
	 *	We count on the initial thread going ok 
	 *	Like idlers init is an unlocked kernel thread, which will
	 *	make syscalls (and thus be locked).
	 */
	init_idle(current, smp_processor_id());

	/* Do the rest non-__init'ed, we're now alive */
	rest_init();
}

static int __initdata initcall_debug;

static int __init initcall_debug_setup(char *str)
{
	initcall_debug = 1;
	return 1;
}
__setup("initcall_debug", initcall_debug_setup);

struct task_struct *child_reaper = &init_task;

extern initcall_t __initcall_start, __initcall_end;

static void __init do_initcalls(void)
{
	initcall_t *call;
	int count = preempt_count();

	for (call = &__initcall_start; call < &__initcall_end; call++) {
		char *msg;

		if (initcall_debug) {
			printk(KERN_DEBUG "Calling initcall 0x%p", *call);
			print_symbol(": %s()", (unsigned long) *call);
			printk("\n");
		}

		(*call)();

		msg = NULL;
		if (preempt_count() != count) {
			msg = "preemption imbalance";
			preempt_count() = count;
		}
		if (irqs_disabled()) {
			msg = "disabled interrupts";
			local_irq_enable();
		}
		if (msg) {
			printk("error in initcall at 0x%p: "
				"returned with %s\n", *call, msg);
		}
	}

	/* Make sure there is no pending stuff from the initcall sequence */
	flush_scheduled_work();
}

/*
 * Ok, the machine is now initialized. None of the devices
 * have been touched yet, but the CPU subsystem is up and
 * running, and memory and process management works.
 *
 * Now we can finally start doing some real work..
 */
static void __init do_basic_setup(void)
{
	driver_init();

#ifdef CONFIG_SYSCTL
	sysctl_init();
#endif

	/* Networking initialization needs a process context */ 
	sock_init();

	init_workqueues();
	do_initcalls();
}

static void do_pre_smp_initcalls(void)
{
	extern int spawn_ksoftirqd(void);
#ifdef CONFIG_SMP
	extern int migration_init(void);

	migration_init();
#endif
	spawn_ksoftirqd();
}

static void run_init_process(char *init_filename)
{
	argv_init[0] = init_filename;
	execve(init_filename, argv_init, envp_init);
}

static inline void fixup_cpu_present_map(void)
{
#ifdef CONFIG_SMP
	int i;

	/*
	 * If arch is not hotplug ready and did not populate
	 * cpu_present_map, just make cpu_present_map same as cpu_possible_map
	 * for other cpu bringup code to function as normal. e.g smp_init() etc.
	 */
	if (cpus_empty(cpu_present_map)) {
		for_each_cpu(i) {
			cpu_set(i, cpu_present_map);
		}
	}
#endif
}

static int init(void * unused)
{
	lock_kernel();
	/*
	 * 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.
	 */
	child_reaper = current;

	/* Sets up cpus_possible() */
	smp_prepare_cpus(max_cpus);

	do_pre_smp_initcalls();

	fixup_cpu_present_map();
	smp_init();
	sched_init_smp();

	/*
	 * Do this before initcalls, because some drivers want to access
	 * firmware files.
	 */
	populate_rootfs();

	do_basic_setup();

	/*
	 * check if there is an early userspace init.  If yes, let it do all
	 * the work
	 */
	if (sys_access((const char __user *) "/init", 0) == 0)
		execute_command = "/init";
	else
		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..
	 */
	free_initmem();
	unlock_kernel();
	system_state = SYSTEM_RUNNING;
	numa_default_policy();

	if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0)
		printk("Warning: unable to open an initial console.\n");

	(void) sys_dup(0);
	(void) sys_dup(0);
	
	/*
	 * 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);

	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.");
}

static int early_param_test(char *rest)
{
	printk("early_parm_test: %s\n", rest ?: "(null)");
	return rest ? 0 : -EINVAL;
}
early_param("testsetup", early_param_test);
static int early_setup_test(char *rest)
{
	printk("early_setup_test: %s\n", rest ?: "(null)");
	return 0;
}
__setup("testsetup_long", early_setup_test);