[gdal-dev] GDALDataset blocks in different thread

[Even Rouault]

James,

ok, I confirm the bug. This was indeed specific to the new implementation of the 
PCIDSK driver that came in 1.7.0. 

See http://trac.osgeo.org/gdal/ticket/3755 for the fix

Le jeudi 16 septembre 2010 20:57:51, James Meyer a écrit :
> Hi Even
> 
> Thanks for the reply. I ran your code and it doesn't block with your
> sample tiff file.
> It blocks with any .pix files (driver: PCIDSK Database File) with the
> output being:
> 
> *********************
> in thread
> finished
> ********************/
> 
> /I am running Ubuntu 10.04 and have GDAL 1.7 on my system installed
> through the package manager.
> CPL_MULTIPROC_PTHREAD is 1.
> 
> When I debug the program with gdb and reach the line that blocks, gdb
> blocks along with the line. I also can't step into the call to
> GDALChecksumImage.
> Of course I might be debugging it wrong.
> 
> Any ideas?
> 
> On 16/09/2010 19:27, Even Rouault wrote:
> > James,
> > 
> > what you see is a bit surprising...
> > 
> > Do you build GDAL by yourself or use a packaged version ? If you build it
> > yourself, you explicitely need to specify --with-threads at ./configure
> > time (unless you use the latest trunk version where it is now the
> > default). In port/cpl_multiproc.h, you can see #define
> > CPL_MULTIPROC_PTHREAD 1 if everything works. If you have only the .so,
> > you can for example try using the CPLCreateThread() method. If it
> > returns -1, then you have the stub implementation.
> > 
> > Could you try compiling and running the following code that is an attempt
> > to have a minimum scenario that reproduces what you descrbe ?
> > 
> > ****************************************
> > 
> > #include<gdal.h>
> > #include<gdal_alg.h>
> > #include "cpl_multiproc.h"
> > 
> > void my_thread(void* pData)
> > {
> > 
> >      GDALDatasetH hDS;
> >      int checksum;
> >      hDS = (GDALDatasetH)pData;
> >      
> >      printf("in thread\n");
> >      checksum = GDALChecksumImage(GDALGetRasterBand(hDS, 1), 0, 0, 20,
> >      20); printf("checksum = %d\n", checksum);
> > 
> > }
> > 
> > int main(int argc, char* argv[])
> > {
> > 
> >      GDALDatasetH hDS;
> >      GDALAllRegister();
> >      hDS = GDALOpen("byte.tif", GA_ReadOnly);
> >      CPLCreateThread(my_thread, hDS);
> >      CPLSleep(2);
> >      printf("finished\n");
> >      return 0;
> > 
> > }
> > 
> > ****************************************
> > 
> > It works fine for me. The byte.tif is available at
> > http://trac.osgeo.org/gdal/export/20628/trunk/autotest/gcore/data/byte.ti
> > f
> > 
> > Otherwise, which OS are you using ?  which GDAL version ? Which GDAL
> > driver is used by your dataset ? etc etc ? If you run it under gdb, what
> > is the stack trace when it is blocked ?
> > 
> > Even
> > 
> > Le jeudi 16 septembre 2010 10:23:27, James Meyer a écrit :
> >> Hi
> >> 
> >> I am opening a GDALDataset in my main thread which I then pass to a
> >> second thread for processing. Only the second thread accesses the
> >> dataset.
> >> 
> >> As soon as the thread makes a call to GDALRasterBand::RasterIO() the
> >> thread blocks indefinitely.
> >> 
> >> Could you please explain to me why this is happening?
> >> 
> >> Also, how do I check whether my build of GDAL was built with the
> >> --with-threads option enabled?
> >> 
> >> Thanks
> >> 
> >> James
> >> _______________________________________________
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