Howard Hinnant wrote: [...]
So I believe you could design code at least partly the way you've proposed with my current proposal. Although I'm sure I'm not fully understanding the write_lock.upgrade_pending() functionality. The way I currently have my rw_mutex implemented, this information is not known.
I know that.
Actually my current implementation is based on your suggested "single entry gate" design. So when the mutex is write locked, it has no idea who or if anyone is waiting outside the gate.
You'd need a semaphore, not a mutex for "entry gate". (first upgrader/writer would lock it and the last one would unlock it).
I liked the idea that the scheduler, not the mutex, decides if a reader or writer gets priority.
Yes, but this scheme has a drawback. "Serial wakes across context switching" (in addition to locking across context switching). For alternative, see (for example) http://groups.google.com/groups?selm=3D9196B2.9BC29299%40web.de (Subject: Re: rwlock using pthread_cond) regards, alexander.