Re: thread safe functions

[Andy Wingo <wingo@pobox.com>]

Hi Ken,

On Sat 21 Aug 2010 17:57, Ken Raeburn <raeburn@raeburn.org> writes:

> On Aug 18, 2010, at 11:56, Andy Wingo wrote (quoting the manual):
>> Thus, you need to put in additional synchronizations when multiple
>> threads want to use a single hashtable, or any other mutable Scheme
>>    object.
>
> Unfortunately this applies to some internals of the implementation too.
> For example, "set-object-property!" and friends use a hash table and
> assoc lists internally.

Fixed, thanks.

> scm_c_issue_deprecation_warning and scm_c_register_extension don't look
> thread-safe to me (in the sense described above).

Fixed also.

> That's just from a spot check; I'm not even trying to be thorough.

I await your more thorough check :)

> And don't get me going on memory ordering models....

I'm interested!

> To be honest, I wouldn't trust libguile in a multithreaded application
> without much more careful analysis, not just of the code, but of the
> assumptions being made and whether they're actually valid for various
> processors (not just the relatively friendly x86) and compilers.
> Without that sort of analysis, I think "use mutexes everywhere" is the
> only safe approach, and libguile certainly isn't doing that.

I think we agree, but I prefer to paint this in a more optimistic
light -- that things are mostly there, but bugs are possible. Bug fixes
are also possible :)

Cheers,

Andy
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