Re: thread safe functions

[Andy Wingo <wingo@pobox.com>]

Hi Cedric,

On Thu 05 Aug 2010 04:27, Cedric Cellier <rixed@happyleptic.org> writes:

> Is there somewhere a list of guile functions that are (/are not) thread
> safe ?
>
> I ask since this morning I was after a strange bug because I was using
> the format module in two different thread, then learnt that these
> functions are not reentrant. I'm also interrested in the thread-safeness
> of gc-stats function.

From "Multi-Threading" in the manual:

       All libguile functions are (intended to be) robust in the face of
    multiple threads using them concurrently.  This means that there is no
    risk of the internal data structures of libguile becoming corrupted in
    such a way that the process crashes.

       A program might still produce nonsensical results, though.  Taking
    hashtables as an example, Guile guarantees that you can use them from
    multiple threads concurrently and a hashtable will always remain a valid
    hashtable and Guile will not crash when you access it.  It does not
    guarantee, however, that inserting into it concurrently from two threads
    will give useful results: only one insertion might actually happen, none
    might happen, or the table might in general be modified in a totally
    arbitrary manner.  (It will still be a valid hashtable, but not the one
    that you might have expected.)  Guile might also signal an error when it
    detects a harmful race condition.

       Thus, you need to put in additional synchronizations when multiple
    threads want to use a single hashtable, or any other mutable Scheme
    object.

If you see any problem in libguile regarding threads, you should
certainly report it to bug-guile@gnu.org (no subscription required).

The same goes for Scheme code. If you have found something in `format'
that is not thread-safe, do let us know.

Thanks,

Andy
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