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From: =?utf-8?Q?Cl=C3=A9ment?= Lassieur <clement@lassieur.org>
Subject: Re: packaging Bootstrap for Cuirass' web interface
Date: Fri, 27 Jul 2018 12:18:55 +0200
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To: Ludovic =?utf-8?Q?Court=C3=A8s?= <ludo@gnu.org>
Cc: Guix-devel <guix-devel@gnu.org>, Tatiana Sholokhova <tanja201396@gmail.com>

Ludovic Court=C3=A8s <ludo@gnu.org> writes:

> Or maybe like this:
>
> (define (make-critical-section . args)
>   "Return a channel used to implement a critical section.  That channel c=
an
> then be passed to 'join-critical-section', which will ensure sequential
> ordering.  ARGS are the arguments of the critical section.
>
> Critical sections are implemented by passing the procedure to execute to a
> dedicated fiber."
>   (let ((channel (make-channel)))
>     (spawn-fiber
>      (lambda ()
>        (let loop ()
>          (match (get-message channel)
>            (((? channel? reply) . (? procedure? proc))
>             (put-message reply (apply proc args))))
>          (loop))))
>     channel))
>
> (define (call-with-critical-section channel proc)
>   "Call PROC in the critical section corresponding to CHANNEL.  Return the
> result of PROC."
>   (let ((reply (make-channel)))
>     (put-message channel (cons reply proc))
>     (get-message reply)))
>
> That makes it clear that the reply channel is used only by the calling
> fiber.

I like it, but in that case MAKE-CHANNEL is called every time
CALL-WITH-CRITICAL-SECTION is called.  Do you think it is a significant
overhead?

Cl=C3=A9ment