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Re: C level mutices and condition variables
From: |
Marius Vollmer |
Subject: |
Re: C level mutices and condition variables |
Date: |
27 Oct 2002 01:33:31 +0200 |
User-agent: |
Gnus/5.09 (Gnus v5.9.0) Emacs/21.2 |
Neil Jerram <address@hidden> writes:
> - Why would you want "to have SCM data in a scm_t_mutex"? - isn't the
> data that you are protecting access to normally a separate variable
> (or set of variables) from the mutex itself?
I was thinking about data that is needed to implement the mutex
itself. It would be nice to be able to use SCM values, I'd say, just
because a SCM string as the mutex name is nicer than a C string.
Concretely, I wanted to use SCM lists to implement the waiting queue
(to add fairness to POSIX mutices), mostly because SCM lists are
already there and why shouldn't I use them then?
> - What do you mean by not abstract enough?
You will declare scm_t_mutex variables and thus the size of the
scm_t_mutex structure can not change. When we want to select mutex
implementations at run-time, that might be a (small) problem. In any
case, I think it is better to hide mutices behind SCM values, just as
other data structures.
> - In "tell them to use the Scheme level mutices", who is "them", and
The people who use scm_t_mutex etc now.
> would it be possible for them to use Scheme mutexes from C code, or
> are you saying that people who need mutexes must code in Scheme?
They can code in C. Instead of
scm_t_mutex my_mutex;
scm_mutex_init (&my_mutex);
scm_mutex_lock (&my_mutex);
it would be
SCM my_mutex = scm_make_mutex ();
scm_lock_mutex (my_mutex);
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