thread safe functions

thread safe functions

[Cedric Cellier]

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.

And in general I think this info would be good to have for every
functions.

Re: thread safe functions

[Andy Wingo]

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
-- 
http://wingolog.org/

Re: thread safe functions

[rixed]

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

Well, apparently for format this was already known, see the last sentence of this old msg from Marius Vollmer :

http://www.mail-archive.com/bug-guile@gnu.org/msg01949.html

But if you want an entry in the bug tracker I can add one :-)

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Re: thread safe functions

[Ludovic Courtès]

Hi,

rixed@happyleptic.org writes:

>> The same goes for Scheme code. If you have found something in `format'
>> that is not thread-safe, do let us know.
>
> Well, apparently for format this was already known, see the last sentence of this old msg from Marius Vollmer :
>
> http://www.mail-archive.com/bug-guile@gnu.org/msg01949.html
>
> But if you want an entry in the bug tracker I can add one :-)

Yes, please do!

Thanks,
Ludo’.

Re: thread safe functions

[Andy Wingo]

Greets,

On Sat 21 Aug 2010 03:35, rixed@happyleptic.org writes:

>> If you have found something in `format' that is not thread-safe, do
>> let us know.
>
> Well, apparently for format this was already known, see the last
> sentence of this old msg from Marius Vollmer :
>
> http://www.mail-archive.com/bug-guile@gnu.org/msg01949.html

I think this was fixed actually, in 

    commit 093d2ca9afb2cb71317fea221466fe0946c94062
    Author: Marius Vollmer <mvo@zagadka.de>
    Date:   Mon Sep 15 13:37:50 2003 +0000

        (format): Rewritten as a big letrec to make it reentrant.  No mutex is
        necessary.  Thanks to Clinton Ebadi!

I have poked format a bit because it was offensive to the eye; but I
don't know of any threadsafety issues there.

Cheers,

Andy
-- 
http://wingolog.org/