Carlo Andrea Orrico SSSA orrico@ocera.sourceforge.org Giuseppe Lipari SSSA lipari@sssup.it 2003 OCERA Consortium Linux RTLinux Real-Time, Linux, RTLinux, Scheduling The aim of this component is to make two different patches to the Linux kernel, the Preemption Patch [PRK] and the RTLinux patch, work together. The RTLinux patch is necessary to make RTLinux work. The Preemption Patch, based upon Robert Love's Preemptible Kernel work, reduces the latency of Linux by allowing preemption to occur inside Linux. By using the Preemption Patch and the Low Latency Patch [LLP], the latency of many Linux operations is significantly reduced. Therefore, both patches are very important for soft real-time scheduling at the Linux user level. In the mixed OCERA configuration, both hard real-time with RTLinux and soft real-time with Linux are required at the same time. Therefore, we need to apply all three patches. However, while the Low Latency Patch does not interfere with the RTLinux patch, both the Preemption Patch and the RTLinux patch modify the interrupt handling code. If the two patches are applied at the same time, Linux crashes. Thus this component is yet another patch that combines the two patches, RTLinux patch and Preemption Patch, while retaining -to a reasonable extent- the advantages of both.