add: t = thread_get_current_thread();
context: thread_atkernel_entry(void){	cpu_status state;	struct thread *t;	bigtime_t now;//	dprintf("thread_atkernel_entry: entry thread 0x%x\n", t->id);	t = thread_get_current_thread();	state = disable_interrupts();	// track user time	now = system_time();	t->user_time += now - t->last_time;	t->last_time = now;	t->last_time_type = KERNEL_TIME;	t->in_kernel = true;	restore_interrupts(state);}