Thank you so much Even. It is working like a charm!

-----Original Message-----
From: Even Rouault [mailto:[email protected]] 
Sent: 30 September, 2016 01:05
To: [email protected]
Cc: Francisco Javier Calzado <[email protected]>
Subject: Re: [gdal-dev] Multithread deadlock

> I don't think this comes from GDALPam, but rather from the lower level 
> machinery of GDALRasterBand & GDALRasterBlock. As I said before, 
> multi- threaded writing has never properly worked and I'm not sure if 
> the issue you see is just an implementation bug or a design bug.

OK, after investigation, it was just an implementation bug. A lack of mutex in
GetLockedBlock() that caused IReadBlock() & IWriteBlock() to be called from 2 
different threads on the same dataset.

Fixed per https://trac.osgeo.org/gdal/ticket/6665

I think the issue was mostly due to using the low level
GetLockedBlock()/MarkDirty()/DropLock() interfaces, and that people using
RasterIO(GF_Read/GF_Write) should be immune to that bug due to locks being 
already taken at that stage.

Anyway fixed now (with a new test case similar to yours). Thanks for the 
reproducers.

Even

--
Spatialys - Geospatial professional services http://www.spatialys.com
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