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<div class="moz-cite-prefix">Hello everyone,<br>
<br>
on 02/10/2017 02:58 AM, Jasmin J. wrote:<br>
</div>
<blockquote cite="mid:94340f25-35d9-ee80-298d-d8a6c8795d78@anw.at"
type="cite">Hi!
<br>
<br>
<blockquote type="cite">
<blockquote type="cite">
<blockquote type="cite">When running a kind of system test
(detach/attach loop in high system load),
<br>
</blockquote>
</blockquote>
<br>
"Don't do that, then." :-)
<br>
[wonders what real-world scenario that test is supposed to
excercise]
<br>
</blockquote>
He does a TEST to find hidden bugs!
<br>
In my practice as a Kernel developer for safety critical systems,
I did such tests a lot for my drivers. You should be happy that
someone does such kind of stress testing and don't make him look
like a fool.
<br>
</blockquote>
Granted, anything that could - and even if rather in theory than in
practice - bring down a system, is a design or implementation error.
However, I guess what all of this boils down to, is that there are
tons of such rather theoretical bugs all over the place in the Linux
kernel (and actually most if not all general purpose operating
systems), design- and implementation-wise. So many of them, that the
important bugs - the ones that cause severe enough problems for a
large enough number of people - get fixed, and the less important
ones don't, simply because there isn't enough workforce available to
do that.<br>
<br>
Or, as Lars said it:<br>
<blockquote type="cite">
<pre wrap="">We have to prioritize somehow, though.
And spending time on debugging something in a path which can easily be
avoided (by simply not doing it; d'oh) won't get the high score.</pre>
</blockquote>
<br>
That's why safety critical systems normally don't run COTS hard- and
software. The mere possibility of there being bugs in a driver,
despite the application of the strictest quality standards to reduce
the risk of introducing bugs, is the reason why safety critical
systems are normally designed to even run their drivers outside of
the kernel space (most of the aerospace, medical, nuclear, military,
etc. systems run microkernel operating systems that isolate driver
crashes and can normally recover from them).<br>
<br>
Anyway, for general purpose systems, people prefer having lots of
features, faster development cycles, lots of drivers for new
hardware, doing more with less and doing it in the cheapest way
possible over safe, robust and secure design and implementation,
otherwise virtually all general purpose OSs would have gone extinct
a very long time ago.<br>
That's the tradeoff that we have to deal with today.<br>
<br>
So, to summarize:<br>
- we still care about fixing bugs<br>
- we do believe that correct implementation is important<br>
- however, we'll have to postpone fixing some rarely occuring bugs
due to (human) resource constraints<br>
- nonetheless, our goal is still building software with
above-average robustness (aka "high availability")<br>
- but we are still in the ball park of general purpose systems here<br>
- for really safety critical tasks, please use systems specifically
designed for the required level of safety<br>
<br>
<blockquote cite="mid:94340f25-35d9-ee80-298d-d8a6c8795d78@anw.at"
type="cite">BR,
<br>
Jasmin
<br>
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<br>
</blockquote>
<br>
Best regards,<br>
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