Re: [Chicken-users] recursive mutex-lock!

[Tobia Conforto]

> (define-macro (my-lock . body)
>  `(let ([result #f])
>     (if (eq? (mutex-state my-mutex) (current-thread))

Well, the value returned by mutex-state can be either:

locked by this thread
        In this case there can be no race condition, as we own
        the mutex and nothing is going to take it away from us.

locked by another thread
abandoned
not-abandoned
        In these cases the mutex is not ours, therefore we don't care
        if it's locked or not, or if any other thread locks or unlocks
        it in a race condition, because we'll call mutex-lock! anyway.

not-owned
        This I can't tell, as I have no clue what not-owned means :-)

>         (set! result (begin ,@body))
>         ;;else
>         (begin
>           (mutex-lock! my-mutex)
>           (set! result (begin ,@body))
>           (mutex-unlock! my-mutex)))
>     result))

My ¢2 analysis says you can get away without a conditional lock, if  
you just ignore the existence of a not-owned state.


Tobia