Init and swapper tasks in Linux

I'm confused about init and swapper tasks in the Linux kernel. My understanding is that the swapper task is like an idle task - it runs when no other processes are runnable. The init task stays asleep, and wakes up to reap processes when required.

I've added another element to the task control block, which I want to initialize to zero for ALL tasks (开发者_如何转开发including init and swapper)

There is a very confusingly named macro, INIT_TASK, in linux/init_task.h, which, seemingly sets the initial values for the task control block of the swapper task.

Where do I set the initial values for the task control block of init? I'm able to set the initial values for all other tasks in the copy_process function in kernel/fork.c when they fork.

INIT_TASK macro is used to initialise the idle task (p->comm="swapper", so called swapper) structure which will linked into vmlinuz.

the 'init' task with pid = 1 in the system, is forked in the rest_init() in end of the start_kernel().

/kernel-3.0.36/init/main.c

347static noinline void __init_refok rest_init(void)
348{
349 int pid;
350
351 rcu_scheduler_starting();
352 /*
353  * We need to spawn init first so that it obtains pid 1, however
354  * the init task will end up wanting to create kthreads, which, if
355  * we schedule it before we create kthreadd, will OOPS.
356  */
357 kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND);

so you can set the initial values for the task control block of init as normal.