Kinda a strawman there. That's got to account for, what, 0.0001% of all use of computers, and probably they would never ever use Linux for these applications (I know medical devices DO NOT use Linux).
> including e.g. the monitor attached to the PC used for displaying
> X-ray images
It's even worse on things like car dashboards: some warning lights on dashboards need to be ASIL-D conformant, which is quite strict. However, developing the whole dashboard software stack to that standard is too expensive. So the common solution these days is to have a safe, ASIL-D compliant compositor and a small renderer for the warning lights section of the display while the rendering for all the flashy graphics runs in an isolated VM on standard software with lower safety requirements. It's all done on the same CPU and GPU.
Mind you, that experience also severely soured me on the quality of medical software systems, due to poor quality of the software that ran in that distribution. Linux itself was a golden god in comparison to the crap that was layered on top of it.
Let's not be too pedantic. You, as an experienced medical device engineer, probably knew what I meant was that they would never use Linux in the critical parts of a medical device as the OP had originally argued. Any device would definitely do all of it's functionality without the part with Linux on it.
The OP was still a major strawman, regardless of my arguments, because the Linux kernel will never be in the critical path of a medical device without a TON of work to harden it from errors and such. Just the fact that Linus' stance is as said would mean that it's not an appropriate kernel for a medical device, because they should always fail with an error and stop under unknown conditions rather than just doing some random crap.
I don't suppose monitors report calibration data back to display adapters do they?
https://smile.amazon.com/EVanlak-Passthrough-Generrtion-Elim...
Edit: I should also add (probably earlier too) that all my examples are specific to the USA FDA process. I'm sure some other place might not have the same rules.
I hope it's rare, but I think a persistent nag window ("Your display isn't calibrated and may not be accurate") is probably a better answer than refusing to work altogether, because it will be clear about the source of the problem and less likely to get nailed down.
I'm mostly familiar with EU rules, but as far as I know the FDA regulations follow the same idea of tiered requirements based on potential harm done.
https://www.fda.gov/medical-devices/human-factors-and-medica...
Honestly, the FDA regulations go too far vs the EU regs. The company I worked for was based in the EU and the products there were so advanced compared to our versions. Ours were all based on an original design from Europe that was approved and then basically didn’t charge for 30 years. The European device was fucking cool and had so many features, it was also capable of being carried around rather than rolled. The manufacturing was almost all automated, too, but in the USA it was not at all automated, it was humans assembling parts then recording it in a computer terminal.
The first priority is safety, absolutely and without question. And then the immediate second priority is the fact that time is money. For every minute that the system is not operating, x amount of product is not being produced.
Generally, having the software fully halt on error is both dangerous and time-consuming.
Instead you want to switch to an ERROR and/or EMERGENCY_STOP state, where things like lasers or plasma torches get turned off, motors are stopped, brakes are applied, doors get locked/unlocked (as appropriate/safe), etc. And then you want to report that to the user, and give them tools to diagnose and correct the source of the error and to restart the machine/line [safely!] as quickly as possible.
In short, error handling and recovery is its own entire thing, and tends to be something that gets tested for separately during commissioning.
[1] PLC's do have the ability to <not stop> and execute code in a real time manner, but I haven't encountered a lot of PLC programmers who actually exploit these abilities effectively. Basically for more complex situations you're quickly going to be better off with more general purpose tools [2], at most handing off critical tasks to PLCs, micro-controllers, or motor controllers etc.
[2] except for that stupid propensity to give-up-and-halt at exactly that moment where it'll cause the most damage.
Felt kinda bad until I thought about how well a "Linux literally killed me" headline would do on HN, but then I realized I wouldn't be able to post the article if I actually died. Such is life. Or death? One or the other.