9d2e4290ff
Shared locking routines explicitly read the value and test it. If the change attempt fails, they fall back to a regular function which would retry in a loop. The problem is that with many concurrent readers the risk of failure is pretty high and even the value returned by fcmpset is very likely going to be stale by the time the loop in the fallback routine is reached. Uninline said primitives. It gives a throughput increase when doing concurrent slocks/sunlocks with 80 hardware threads from ~50 mln/s to ~56 mln/s. Interestingly, rwlock primitives are already not inlined.
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