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<H2><A NAME="s4">4. Linux Startup</A></H2>
<P>We start the Linux kernel first from C code executed from ''startup_32:''
asm label:
<P>
<P>
<PRE>
|startup_32:
|start_kernel
|lock_kernel
|trap_init
|init_IRQ
|sched_init
|softirq_init
|time_init
|console_init
|#ifdef CONFIG_MODULES
|init_modules
|#endif
|kmem_cache_init
|sti
|calibrate_delay
|mem_init
|kmem_cache_sizes_init
|pgtable_cache_init
|fork_init
|proc_caches_init
|vfs_caches_init
|buffer_init
|page_cache_init
|signals_init
|#ifdef CONFIG_PROC_FS
|proc_root_init
|#endif
|#if defined(CONFIG_SYSVIPC)
|ipc_init
|#endif
|check_bugs
|smp_init
|rest_init
|kernel_thread
|unlock_kernel
|cpu_idle
</PRE>
<P>
<UL>
<LI>startup_32 [arch/i386/kernel/head.S]</LI>
<LI>start_kernel [init/main.c]</LI>
<LI>lock_kernel [include/asm/smplock.h]</LI>
<LI>trap_init [arch/i386/kernel/traps.c]</LI>
<LI>init_IRQ [arch/i386/kernel/i8259.c]</LI>
<LI>sched_init [kernel/sched.c]</LI>
<LI>softirq_init [kernel/softirq.c]</LI>
<LI>time_init [arch/i386/kernel/time.c]</LI>
<LI>console_init [drivers/char/tty_io.c]</LI>
<LI>init_modules [kernel/module.c]</LI>
<LI>kmem_cache_init [mm/slab.c]</LI>
<LI>sti [include/asm/system.h]</LI>
<LI>calibrate_delay [init/main.c]</LI>
<LI>mem_init [arch/i386/mm/init.c]</LI>
<LI>kmem_cache_sizes_init [mm/slab.c]</LI>
<LI>pgtable_cache_init [arch/i386/mm/init.c]</LI>
<LI>fork_init [kernel/fork.c]</LI>
<LI>proc_caches_init </LI>
<LI>vfs_caches_init [fs/dcache.c]</LI>
<LI>buffer_init [fs/buffer.c]</LI>
<LI>page_cache_init [mm/filemap.c]</LI>
<LI>signals_init [kernel/signal.c]</LI>
<LI>proc_root_init [fs/proc/root.c]</LI>
<LI>ipc_init [ipc/util.c]</LI>
<LI>check_bugs [include/asm/bugs.h]</LI>
<LI>smp_init [init/main.c]</LI>
<LI>rest_init</LI>
<LI>kernel_thread [arch/i386/kernel/process.c]</LI>
<LI>unlock_kernel [include/asm/smplock.h]</LI>
<LI>cpu_idle [arch/i386/kernel/process.c]
</LI>
</UL>
<P>The last function ''rest_init'' does the following:
<P>
<P>
<OL>
<LI>launches the kernel thread ''init''</LI>
<LI>calls unlock_kernel</LI>
<LI>makes the kernel run cpu_idle routine, that will be the idle
loop executing when nothing is scheduled
</LI>
</OL>
<P>In fact the start_kernel procedure never ends. It will execute
cpu_idle routine endlessly.
<P>
<P>Follows ''init'' description, which is the first Kernel Thread:
<P>
<P>
<PRE>
|init
|lock_kernel
|do_basic_setup
|mtrr_init
|sysctl_init
|pci_init
|sock_init
|start_context_thread
|do_init_calls
|(*call())-> kswapd_init
|prepare_namespace
|free_initmem
|unlock_kernel
|execve
</PRE>
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