[gdal-dev] GDALDataset blocks in different thread

[Even Rouault]

Le jeudi 16 septembre 2010 22:54:16, James Meyer a écrit :
> Oh okay. Thanks!
> 
> All the while I thought I was doing something wrong.
> I'm assuming the fix won't be reflected in the version that is available
> from the Ubuntu repositories, right?

It's up to the Ubuntu packagers. You'll probably get the fix when they'll 
update to the next versions that will be released by the project (1.8.0 or 
1.7.3).

> In other words I will need to build GDAL from source then?

Yes, for now, that's the way to go if you want to get the fix quickly.

> 
> Regards
> 
> James
> 
> On 16/09/2010 21:29, Even Rouault wrote:
> > 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
> >>>> _______________________________________________
> >>>> gdal-dev mailing list
> >>>> gdal-dev at lists.osgeo.org
> >>>> http://lists.osgeo.org/mailman/listinfo/gdal-dev