Use Interlocked* functions

Rob Shearman rob at
Mon Jan 10 08:40:49 CST 2005

Mike McCormack wrote:

> The most important reason in my mind to do this is so that people 
> implementing objects in the future copy code that uses the 
> Interlocked* functions.  There's no overhead to using those 
> functions... no penalty if we use them in code that doesn't need to be 
> thread safe, so we should just use them everywhere.

On uniprocessor machines this is true, but I don't think the same can be 
said for SMP/SMT machines. The "lock" prefix for the instructions causes 
the processor to emit a signal that tells all other processors to not 
access memory for a period of time. I haven't seen any benchmarks that 
say how much this costs, but it isn't "no overhead."


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