[Tinyos-devel] Will safe protect this kind of code?

[John Regehr]

Eric,

Sure, ensuring that a pointer never becomes NULL is an excellent use for 
Deputy.  However I don't think anyone has done Deputy annotations for the 
code that implements threads.  If you do this you may run into a few 
problems since things like dispatchers inherently perform operations that 
violate safety.  I'd be interested to see how it goes...

John Regehr



On Wed, 13 Aug 2008, Eric Decker wrote:

> In particular, current_thread comes from either remove or dequeue.  I've
> seen situations when we were messing with early thread code where
> current_thread actual got NULL and it wreck havoc.
>
> Will safe and deputy detect current_thread becoming NULL?
> 
Alternatively, I could do something like:
>
> if (!current_thread)
>    panic(...);
> else
>    current_thread->state = TOSTHREAD_STATE_ACTIVE;
>
> but that is ugly.
>
> eric
>
>
>  void scheduleNextThread() {
>    if(tos_thread->state == TOSTHREAD_STATE_READY)
>      current_thread = call ThreadQueue.remove(&ready_queue, tos_thread);
>    else
>      current_thread = call ThreadQueue.dequeue(&ready_queue);
>
>    current_thread->state = TOSTHREAD_STATE_ACTIVE;
>  }
>
>
> --
> Eric B. Decker
> Senior (over 50 :-) Researcher
> Autonomous Systems Lab
> Jack Baskin School of Engineering
> UCSC
>