I've been trying to solve the deadlock problem reported here: http://lists.boost.org/Archives/boost/2005/08/92307.php but I've simply run into more and more problems, and just about every operation I've tried will deadlock if you try hard enough. THIS IS NOT GOOD. Applying Roland Swartz's suggested fix everywhere that looked appropriate initially seemed to fix the issue, but once you move to more complex situations (both readers and writers) then the deadlocks simply come back again. At this point I've exhausted my understanding of the problem and the design of the lock. As an aside: it is *very* hard to implement something like this correctly: no amount of debugging will ever get you a reliable system, only a clearly understood design backed up by a solid theoretical understanding of the implementation method (formal methods anyone?). To be honest I have to question whether it's even a good idea for this to be in Boost (no slur intended towards the implementers of that class, it's the difficulty of the problem that's the issue). In case anyone wants to pursue this further I'm attaching my current test case, and the current patches I have to the implementation, however, please note that neither this test case, nor the current regression tests are anything like comprehensive, THEY WILL NOT CATCH ALL POSSIBLE PROBLEMS. Sorry about the capital letters folks, but I suspect we have a "Huston, we have a problem" moment here :-( Regards, John.