Thanks for the report, I have entered into our JIRA issue tracker here:
https://jira.codehaus.org/browse/GEOT-4780
As with many open source projects we are short on volunteers - do you think
you could create a test case or small example of how to reproduce this
issue?
Jody Garnett
On Thu, Apr 17, 2014 at 2:14 AM, Stéphane WASSERHARDT <
stephane.wasserha...@magellium.fr> wrote:
> Hello,
>
>
>
> I’m using geotools in a threaded application, where I use the
> StreamingRenderer while performing other background process using Geotools.
>
> There’s a recurrent deadlock with some CRS transformations which I will
> try to explain with an example :
>
>
>
> The StreamingRenderer needs to reproject a raster
> (Resampler2D.reproject(…)), it uses the ReferencingFactoryFinder to find
> the transformation to perform.
>
> More precisely, it goes through ReferencingFactoryFinder.getFactory()
> which is synchronized.
>
>
>
> When another *simultaneous* process wants to transform an envelope
> (ReferencedEnvelope.transform(…)), it ends up searching for the transform
> using the BufferedCoordinateOperationFactory.
>
> In the BufferedCoordinateOperationFactory.createOperation(CRS, CRS)
> method, the “hints” are locked by a synchronized block.
>
> Then it continues (through the ThreadedHsqlEpsgFactory), and sometimes
> ends up with a transform that needs to use the ReferencingFactoryFinder in
> order to initialize itself.
>
> For instance, the NTv2Transform uses its “locateGrid” method which uses
> the ReferencingFactoryFinder.
>
> But the ReferencingFactoryFinder.getFactory() method cannot be called
> since it’s locked by the StreamingRenderer’s thread.
>
>
>
> The processing thread is locked, but the one using the StreamingRenderer
> can continue (and hopefully finish) its work so that it releases the lock
> on ReferencingFactoryFinder.
>
> In the ReferencingFactoryFinder.getFactory() method which is running in
> this thread, geotools iterates over all factories, and will find the
> BufferedCoordinateOperationFactory.
>
> The BufferedCoordinateOperationFactory.getImplementationHints() method is
> called, and waits for its “hints” in a synchronized block…
>
>
>
> Here is the deadlock :
>
> * The StreamingRenderer thread owns the lock on ReferencingFactoryFinder,
> and waits for the BufferedCoordinateOpertaionFactory’s hints lock to be
> released.
>
> * The processing thread owns the lock on the
> BufferedCoordinateOpertaionFactory’s hints, and waits for the
> ReferencingFactoryFinder to be released.
>
>
>
> I’m not familiar enough with the referencing and transform API to find
> where and how to fix this properly…
>
> Can someone help please ?
>
>
>
> Thanks in advance.
>
> Stephane
>
>
>
>
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