I would hate user space locking if it weren't that sexy...

Linux has seen a lot of new features and developments in the last years in order to accommodate better scalability, interactivity, response time and POSIX compliance. With this changes, Telecom developers began to get serious about Linux and started porting their systems to it. By doing that they brought new usage models and needs; and among those needs was a single package that provided support for threads, mutual exclusion, priority inversion protection and robust synchronization for mission critical and fault-proof systems on both timesharing and soft real-time environments. This paper describes our experiences trying to meet this need, where are we standing and where are we headed. We will detail how originally we tried to modify the futex code, but later found we had to abandon that in favor of a very similar design based on a layered implementation. This implementation accomodates a kernel and user space locking and synchronization infrastructure that will hopefully satisfy the requirements of those needing to use and port complex multithreaded real-time code.