Re: [libdbi-devel] Thread Safety question

[Andreas E. <ae...@op...>]

Markus Hoenicka wrote:
> Quoting Artyom <art...@ya...>:
> 
>> I'm mostly interested in accessing different dbi_conn objects
>> from same thread in safe way.
>>
>> So, it is quite reasonable to call dbi_initialize from single thread
>> and call dbi_shutdown from single thread.
>>
> 
> This is perfectly reasonable. However, if we advertise libdbi as  
> thread-safe, we must also accommodate programmers who use one instance  
> per thread, for whatever reason.
> 

Not necessarily. You can advertise certain interfaces as thread-safe
while making no such statement of other interfaces. For example, it
doesn't make sense to have certain init functions thread-safe, because
they might be designed to run once and once only during the apps'
lifetime.

> 
>> It would be great, at least it is possible to know what
>> backends are not safe.
>>
>> For the record I had seen in sqlite (not sqlite3) backend
>> usage of strtok. So it should be thread unsafe.
>>
>> What happens with others?
>>
> 
> I'll start reviewing the drivers as soon as time permits. We may end  
> up labelling individual drivers as thread-safe if we can't get all of  
> them fixed. We may also end up claiming thread-safety only for a  
> subset of platforms (i.e. those which implement reentrant versions of  
> functions which we cannot do without).
> 

In all likelihood, those platforms will be the ones with decent thread-
support to begin with, so it should be a reasonably safe bet that apps
on such platforms will either not be multi-threaded anyway, or that it's
relatively straightforward to use reentrant functions in libdbi there.

-- 
Andreas Ericsson                   and...@op...
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