How can I write a lock free structure?

Question

In my multithreaded application and I see heavy lock contention in it, preventing good scalability across multiple cores. I have decided to use lock free programming to solv

Answer 1

The basic principle for lock-free synchronisation is this:

• whenever you are reading the structure, you follow the read with a test to see if the structure was mutated since you started the read, and retry until you succeed in reading without something else coming along and mutating while you are doing so;

• whenever you are mutating the structure, you arrange your algorithm and data so that there is a single atomic step which, if taken, causes the entire change to become visible to the other threads, and arrange things so that none of the change is visible unless that step is taken. You use whatever lockfree atomic mechanism exists on your platform for that step (e.g. compare-and-set, load-linked+store-conditional, etc.). In that step you must then check to see if any other thread has mutated the object since the mutation operation began, commit if it has not and start over if it has.

There are plenty of examples of lock-free structures on the web; without knowing more about what you are implementing and on what platform it is hard to be more specific.