Core Image: what are thread safety and optimal strategies for concurrency?

I have a few questions on Core Image, in relation to the new implementation in OS X 10.11.

Can CIImages be considered thread-safe?

In other words, can an identical or different CIContexts, on different threads, be accessing the same CIImage without running into problems?

Are CIContexts themselves thread-safe? Even if they are, what would be the best strategy for higher performance: sharing a single CIContexts among threads that will concurrently use the context, or giving each thread its own CIContext to play with?

Core Image: what are thread safety and optimal strategies for concurrency?
 
 
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