Re: crashes with Fibers

[Clément Lassieur]

Hi Amirouche,

Amirouche Boubekki <address@hidden> writes:

>> You test5 code should definitly work. Otherwise, it requires to pre-allocate
>> as many thread as you need before you know you will them. May be we can look
>> at it backward and say, that allocating a pool of threads in advance is more
>> interesting performance wise.

But the cost of allocating a thread pool is very small compared to the
cost of a doing git clone, which may take a minute or so.

>>> Anyway, try to spawn the thread and/or create the channel before you
>>> run fibers. I can't try that myself because of my slow connection which
>>> takes ages to install guile-fibers.

I can't do that because in the program I'm working on (Cuirass), the
first calls to RUN-FIBERS and SPAWN-FIBER happen very early[1].  They
are kind of the entry point of the program.  At that time I don't know
how many repositories I will need to fetch simultaneously.  Thus test3
and test6 don't meet my needs.

[1]: 
https://git.savannah.gnu.org/cgit/guix/guix-cuirass.git/tree/bin/cuirass.in#n144

>>> Something like:
>>
>> (use-modules (fibers))
>> (use-modules (fibers channels))
>>
>>> (define (test6)
>>>   (let ((channel (make-channel)))
>>>     (call-with-new-thread
>>>      (lambda ()
>>>        (put-message channel "hello world")))
>>>     (run-fibers
>>>      (lambda ()
>>>        (spawn-fiber
>>>         (lambda ()
>>>           (format #t "~a~%" (get-message channel)))))
>>>     #:drain? #t)))
>>
>> It works on my side.
>
> FWIW, the following code doesn't crash, but apparently does nothing:
>
> (define (test7)
>   (let ((channel (make-channel)))
>     (run-fibers
>      (lambda ()
>        (spawn-fiber
>         (lambda ()
>           (call-with-new-thread
>            (lambda ()
>              (put-message channel "hello world")))
>           (format #t "~a~%" (get-message channel)))))
>     #:drain? #t)))

This crashes the same way test5 does, you need to run it more :-)