In order to achieve maximum responsiveness, much of the QNX Neutrino microkernel is fully preemptible. In some cases, this means that when a thread is interrupted in a kernel call, it won't be able to restart exactly where it began. Instead, the kernel call will be restarted—it “rewinds” itself. The SAT tries to hide the spurious calls but may not succeed in suppressing them all. As a result, it's possible to see several events generated from a specific thread that has been preempted. If this occurs, the last event is the actual one.