[gdal-dev] write tif error

[weixj2003ld]

 I use the following code to read data from a geotiff file and do some computing and write it into
 a new one.the bands number is 6; ...
 GDALDataset *poSrcDS,*poDstDS;//poSrcDs:the source file,poDstDS:the goal
 source GDALRasterBand *poSrcBand,*poDstBand;//poSrcBand:the source
 band,poDstBand:the goal band GDALDriver *poDstDriver;
 double *m_AdGeoTransform=new double[6];

 ...
 poDstDriver=GetGDALDriverManager()->GetDriverByName(poSrcDS->GetDriver()->G
etDescrition());
 poDstDS=poDstDriver->create(DstFilename,nX,nY,6,GDT_Float32,NULL);
 poSrcDS->GetGeoTransform(m_AdGeoTransform)
 poDstDS->SetGeoTransform(m_AdGeoTransform);
 poDstDS->SetProjection(poSrcDS->GetProjectionRef());

 for(int iBand=0;iBand<6;iBand++)
{
    poSrcBand=poSrcDS->GetRaserBand(iBand+1);
   poDstBand=poDstDS->GetRaserBand(iBand+1);
   float *pafScanline;
   pafScanline=(float *)CPLMalloc(sizeof(float)*nX;
   for(int i=0;i<nY;i++)
  {   
poSrcBand->RasterIO(GF_Read,0,0,nX,i,pafScanline,nX,1,GDT_Float32,0,0);
 poDstBand->RasterIO(GF_Write,0,0,nX,i,pafScanline,nX,1,GDT_Float32,0,0);//If I comment this code,the program will be ok. }
 }
GDALClose((GDALDatasetH)poDstDS);

When I run my program,CPU is very alway busy,and the program is
 blocked,why?
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