rem: void thread_atkernel_exit(void)
add: thread_atkernel_exit(void)
context: void thread_atkernel_exit(void){	int state;	struct thread *t;	bigtime_t now;//	dprintf("thread_atkernel_exit: entry\n");	t = thread_get_current_thread();	state = disable_interrupts();	GRAB_THREAD_LOCK();	_check_for_thread_sigs(t, state);	t->in_kernel = false;	RELEASE_THREAD_LOCK();	// track kernel time	now = system_time();	t->kernel_time += now - t->last_time;	t->last_time = now;	restore_interrupts(state);}