[Gdal-dev] Motion to Adopt RFC 16: OGR Thread Safety

[Simon Perkins]

> What about methods that modify a layer? i.e. we have two threads, A and 
> B accessing the same layer via layer clones, so they each have their own 
> read state. What if thread A checks to see if a feature with FID 42 
> exists, then B invokes a method to delete feature 42, before thread B 
> attempts to get the geometry for that feature? Even if those calls are 
> serialized, it is likely that thread A will get very confused.
>   

Doh! Managed to screw up my example... This should read:

"What about methods that modify a layer? i.e. we have two threads, A and 
B accessing the same layer via layer clones, so they each have their own 
read state. What if thread A checks to see if a feature with FID 42 
exists, then B invokes a method to delete feature 42, before thread *A* 
attempts to get the geometry for that feature? Even if those calls are 
serialized, it is likely that thread A will get very confused."


Cheers,

Sy


> I think in general, guaranteeing thread safety when you have threads 
> modifying data is in general extremely hard at the library level, and 
> really requires some kind of thread coordination at the application 
> program level. Maybe the datasource mutex could be exposed with a couple 
> of handy Lock/Unlock methods to make this kind of high level 
> coordination easier? In any case, shouldn't the RFC mention something 
> about reading vs writing?
>
> Cheers,
>
> Simon
>
>
> Frank Warmerdam wrote:
>   
>> Motion: To adopt RFC 16: OGR Thread Safety
>>
>> http://trac.osgeo.org/gdal/wiki/rfc16_ogr_reentrancy
>>
>> ---
>>
>> There wasn't to much discussion on this as far as I recall, which I take
>> to mean no one has a problem with it.  So moving to formal vote so I can
>> implement this coming week.
>>
>> +1 from me.
>>
>> Best regards,
>>     
>
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>   

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