[Gdal-dev] Failed to acquire IOMutex in WarpRegion()

[Frank Warmerdam]

matt wilkie wrote:
> Hi,
> 
> Does anyone know what this message means and what to do about it?
> 
>  gdalwarp -wm 512 -co bigtiff=yes -multi --optfile tiff-w144-list.txt
> warp-mosaic-orig-nvue_w144.tif
> 
> Creating output file that is 43221P x 54021L.
> Processing input file N60-W144_ur.tif.
> 0...10ERROR 1: Failed to acquire IOMutex in WarpRegion().
> 
> where tiff-w144list.txt is a list of 5 input rasters of 1.2gb each,
> projection wgs84,  21621 x 18021 pixels.
> 
> This is on WinXPsp2 64bit system with 4gb of ram and 150gb free disk space,
> and GDAL 1.5.0b1, FWTools 2.0.3, released 2007/12/10. 

Matt,

When you use -multi, the warper attempts to keep two threads working, one
doing read/write, and one doing resampling in memory.  For synchronization
purposes they use mutexes, and with a default timeout of 600 seconds.  If
one thread waits more than 600s you will get the above error, and a warp
failure.

Perhaps I ought to increase the timeouts quite a lot.  If you file a ticket,
I'll look into it.  But from your side you can reduce the chunk size so it
won't take so long to process.  Use -wm 100 instead of -wm 512 for instance.

Generally speaking the -multi option isn't well maintained.  I only introduced
it in the first place in a desperate attempt to squeeze extra performance
out of the warp to meet performance objectives of the contract for which it
was developed.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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and watch the world go round - Rush    | President OSGeo, http://osgeo.org