Condvar variant usable with ReentrantMutex

[gdesmott]

Condvar is not usable with ReentrantMutex because of Condvar::wait() takes a MutexGuard.

Any reason to not have a variant of the API handling ReentrantMutex ?

[bjorn3]

Condvar::wait() has to unlock the mutex. For a reentrant mutex it would have to unlock all mutex guards for the mutex to prevent a deadlock. This would be unsound however as ReentrantMutexGuard is Sync and thus another thread may be accessing a ReentrantMutexGuard while it is unlocked if Condvar::wait() were to unlock all mutex guards rather than just the one that is passed in.