l4_thread_ex_regs and suspending thread

hi, l4-hackers.

I am now using l4v2 API with L4/Fiasco. I know that on L4 v.2 API, the 
thread is created if set eip/esp/pager/preempter to real values. And it 
seems that likewise, thread can be suspended if setting these values to 
invalid ones. But as I tried it, setting the running thread eip/esp to 
-1 causes double page fault in that thread. Setting them to 0 does not 
change these values (though, in headers' comments, documented value is 
~0). Setting pager/preempter to L4_INVALID_ID also causes double page 
fault. This is strange, as docs/comments state the converse.

So, is it possible anyhow to suspend/resume the running thread from 
another thread? I know, that the thread can be suspended if entering 
unconditional l4_ipc_wait(), but this is from the inside that thread. 
How could it be done from an outside thread?

Thanks in advance,
valery