"Peter Dimov" <pdimov@mmltd.net> writes:
I have produced a read/write mutex implementation as a side effect, available at
http://www.pdimov.com/cpp/rw_mutex.cpp
that is lock-free when there is no contention (i.e. when a reader attempts a lock and no writers are active, or when a writer attempts a lock and the lock is free.)
It appears to work (famous last words.) If you see any subtle problems or can stress test it on a multiprocessor, please let me know.
This implementation either starves writers or starves readers. Running your test code lets the writers all do some work, then the readers take over until they're all finished, then the writers alternate until they're all done. Running my test harness against it (based on Howards sample at http://home.twcny.rr.com/hinnant/cpp_extensions/rw_perf.html), I get lots of writer work, followed by a little reader work, then more writer work, then a little more reader work, such that all the writer threads finish considerably before the reader threads. This is a single CPU machine. Anthony -- Anthony Williams Software Developer Just Software Solutions Ltd http://www.justsoftwaresolutions.co.uk