Open Source Summit + ELC North America 2020

Safely sharing data between high priority real-time threads (or processes) and lower priority threads is a common problem in designing real-time applications. A common way to solve this bounded producer/consumer problem is by using conditional variables (condvars).

The glibc implementation of condvars prior to 2.25 requires a patch to fix a priority inversion with an internal lock. More recently, in glibc versions 2.25 and newer, the condvar code was refactored to address a POSIX compliance issue. This in turn broke that fix and modified the implementation in such a way as to prevent real-time usage of glibc condvars by introducing new type of priority inversion.

The librtpi project was formed to address this problem and provide a narrow real-time specific implementation of the condition variable mechanism in a way which can be readily used in lieu of the glibc implementation. It is designed to support priority inheritance on the associated mutex by default and more importantly always wake the waiters in priority FIFO order.

We will discuss the current state of the project, as well as the long term strategy with a goal to increase the awareness and participation in the project.