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.tif
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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