isolate-check-environment: check SMT and improve scaling_governor check

[pobrn]

Please see the commit messages.

[gollux]

Overall, I like the changes, but I would prefer the if not to fail when cat returns a string with spaces. Please add a pair of quotes.

[pobrn]

Sorry, can you specify where?

[gollux]

Eh, shell rules have bitten me again :)

I meant this:

if val=$(cat /sys/devices/system/cpu/smt/active 2>/dev/null) ; then

But surprisingly enough, even though word splitting is done in echo $(cat something), it is not done in a=$(cat something), so your code is actually safe. This is actually documented in man bash:

A variable may be assigned to by a statement [...] All values undergo tilde expansion, parameter and variable expansion, command substitution, arithmetic expansion, and quote removal [...] Word splitting and pathname expansion are not performed.

Still, I think that adding explicit quotes makes the code more obvious.

[pobrn]

Still, I think that adding explicit quotes makes the code more obvious.

Added " around both assignments; but note that there are other checks that have no ".