Linux in mixed-criticality systems [LWN.net]

Linux in mixed-criticality systems

Posted Dec 14, 2018 15:11 UTC (Fri) by marcH (subscriber, #57642)
In reply to: Linux in mixed-criticality systems by nhippi
Parent article: Linux in mixed-criticality systems

> OTOH having a separate microcontroller for everything means a lot more wires and connectors,

Not for everything; for safety-critical systems. Cars used to be certified and pretty safe before micro controllers so there can't be that many safety-critical micro controllers in a car today.

Reducing the number of micro controllers and wires is great and all and sure you also want to add some partitioning and "soft real-time" there but that's different.

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Linux in mixed-criticality systems

Posted Dec 14, 2018 15:24 UTC (Fri) by marcH (subscriber, #57642) [Link] (1 responses)

By the way safety critical ethernet already exists and is already in use in planes for instance. Reducing the number of wires doesn't require reducing the number of microcontrollers, those are two different problems with several orders of magnitude difference in complexity.

Linux in mixed-criticality systems

Posted Dec 14, 2018 17:01 UTC (Fri) by ibukanov (subscriber, #3942) [Link]

Older planes still use ARINC 429 protocol which is one way serial link where one source can talk to multiple clients. But since it is used only in aviation, the boards are really expensive. It is cheaper just to use Ethernet and require special verified routers where software is formally verified.

Linux in mixed-criticality systems

Posted Dec 14, 2018 16:54 UTC (Fri) by smurf (subscriber, #17840) [Link] (3 responses)

> Cars used to be certified and pretty safe before micro controllers

Yeah, but that was before brake assistants and airbags and automatic transmissions and mandatory seatbelt warnings and central locks and theft protection and whatnot. All of these, and more, either require µCs outright or are more expensive if you build them without one.

Today? No way. Even less way if you want a car that doesn't burn gasoline.

Linux in mixed-criticality systems

Posted Dec 14, 2018 17:33 UTC (Fri) by marcH (subscriber, #57642) [Link] (2 responses)

mandatory != safety critical

Central locks and rear cameras are "real-time" (for some definition of it) but really not safety critical.

Linux in mixed-criticality systems

Posted Dec 20, 2018 6:26 UTC (Thu) by JdGordy (subscriber, #70103) [Link] (1 responses)

pretty sure there is a requirement for rear cameras to turn on within ~2s of power, and quite likely there is actual safety critical requirements on central locking (if fitted obviously) around how they work in accidents

Linux in mixed-criticality systems

Posted Dec 20, 2018 6:39 UTC (Thu) by marcH (subscriber, #57642) [Link]

My car doesn't have a rear camera, so it must be critically unsafe.

Check what it takes to open a damaged car door.

ABS when fitted is a good example considering its job is to ... release the brakes. Cruise control and any other sort of self driving feature are other obvious ones. Can't wait for the fun of seeing these interact with security holes and other bugs in the media player. As usual the only winners will be the lawyers.

Linux in mixed-criticality systems

Posted Dec 14, 2018 17:38 UTC (Fri) by mpr22 (subscriber, #60784) [Link]

Safety-critical microcontrollers in production automobiles have (with initially narrow market penetration) been with us for nearly fifty years, in the form of anti-lock braking systems.