Hi Taylan, On Thu 12 Nov 2015 16:29, taylanbayi...@gmail.com (Taylan Ulrich "Bayırlı/Kammer") writes:
> It seems that the 'monitor' form is currently a no-op. The form > > (par-for-each (lambda (x) > (monitor > (foo))) > xs) > > should be functionally equivalent to > > (let ((mutex (make-mutex))) > (par-for-each (lambda (x) > (with-mutex mutex > (foo))) > xs)) > > but currently becomes > > (par-for-each (lambda (x) > (let ((mutex (make-mutex))) > (with-mutex mutex > (foo)))) > xs) > > which is ineffective. > > I don't know what's the best way to fix this. The simplest thing that > comes to my mind is something along the lines of: > > (define-syntax monitor > (lambda (stx) > (syntax-case stx () > ((_ body body* ...) > (let ((uuid (generate-uuid))) > #`(with-mutex (mutex-with-uuid #,uuid) > body body* ...)))))) > > where mutex-with-uuid looks it up from a hash table at run-time and > instantiates it when it doesn't exist, this operation also being > synchronized across threads, like: > > (define mutex-table (make-hash-table)) > > (define mutex-table-mutex (make-mutex)) > > (define (mutex-with-uuid uuid) > (with-mutex mutex-table-mutex > (or (hash-ref mutex-table uuid) > (let ((mutex (make-mutex))) > (hash-set! mutex-table uuid mutex) > mutex)))) > > If that looks OK, I can try to make a proper patch from it. I'm not > sure what I'd use in place of `generate-uuid' though. Would `gensym' be > good enough? You're totally right on all points. Please do prepare a patch :) I wish we could do something faster for the "embedded" mutex but correctness should come first. Cheers, Andy
