Martin Dobias wrote:
Hi Frank
On Wed, Jun 23, 2010 at 4:58 PM, Frank Warmerdam <warmer...@pobox.com> wrote:
Martin,
Generally speaking it is not safe to have multiple threads making calls
into a single OGRLayer at the same time. At the very least you will
encounter the "messing up" effect on GetNextFeature(), even if you
serialize calls, and if you don't serialize the calls to the OGRLayer
you will also face potentially severe problems and crashes.
With regard to RFC 16, only a little work in the existing code with
locks was implemented. None of the TestCapability or GetLayerClone()
work was done. I still think that the approach in the RFC is reasonable
but I don't currently have funding to pursue the matter. There was
also some pushback at the time though I don't recall all the details.
My intent is to use two OGRLayer instances of the same layer: one
instance for handling various stuff in main thread, the other one in
worker thread for rendering. Can I expect the GetNextFeature calls to
be reentrant, i.e. can they be called from both threads simultaneously
using different instances of layers?
Martin,
Are the different OGRLayer instances coming from distinct OGRDataSource
instances? If so, yes, you could normally treat them as reentrant though
there might be a few special cases where that turns out not to be true.
Certainly this is only a good idea in read-only activities.
Best regards,
--
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up | Frank Warmerdam, warmer...@pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush | Geospatial Programmer for Rent
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