> In Linux, when a real time process is executing and an interrupt comes, will > the RT process be preempted?
> Is RT process considered superior to interrupts? Generally, interrupts always intercept processes as long as interrupts are enabled, but ... > A missed IRQ is not considered fatal but where as missing the upper time > limit for an RT process will be considered fatal. Hence I think, as a simple > solution, the process should not be preempted. > Is it the case? … to deal with situations like this, two rather different approaches exist to mitigate the situation of missing deadlines on process level: 1) RT-Preempt: The RT-Preempt Patch makes Kernel Threads from ISRs that by default run at RT priority 50. Thus, only a minimal Kickoff ISR is needed to trigger the related thread, so that RT processes running at priorities bigger than 50 are only preempted for a minimal amount of time. 2) Xenomai: Xenomai features a Dual-Kernel approach (RT-Domain and Non-RT Domain), in which all interrupts are virtualized. Thus, RT processes (those running in the RT-Domain) are being executed with a higher priority than virtualized interrupts, more or less again imposing only a minimal amount of preemption delay due to some Kickoff ISR part. However, there is no such mechanism available for vanilla kernels.
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