A practically feasible modification to fixed-priority schedulers allows to avoid timing channels despite threads having access to precise clocks. This modification is rather simple: we compute at admission time a static predicate that states whether a thread may possibly leak information; if such a thread blocks we switch to the idle thread instead. We describe the modified scheduler, provide a mechanical PVS-based proof of noninterference and show how common admission algorithms can be reused to give real-time guarantees for this modified scheduler. While providing similar isolation guarantees, our approach outperforms timepartitioning schedulers in terms of achieved real-time guarantees.
Völp et al. REF presented modifications to fixed-priority scheduling, altering thread blocks that potentially leak information with the idle thread to avoid the exploitation of timing channels.
Avoiding timing channels in fixed-priority schedulers
ASIACCS '08
Computer Science