core/sched: add sched_change_priority()

[maribu]

Contribution description

This PR is a rebase of the sched_change_priority() function from #7445 (introduced in commit 976d17f) with some changes:

1. No module required to unlock this
   • The linker does a fine job at garbage collecting the function, if it is unused
2. The function works as expected in corner cases
   • If the modified thread is the running one, this will work
   • If the modified thread is pending and becomes a higher priority than the active one, it will now preempt the running one

Testing procedure

A test application was added that contains an automatic test. E.g.

$ make BOARD=nucleo-f767zi -C tests/sched_change_priority flash test
[...]
socat - open:/dev/ttyACM0,b115200,echo=0,raw 
main(): This is RIOT! (Version: 2022.01-devel-305-ga9249-core/change_prio)
[t3] Setting my priority to THREAD_PRIORITY_MAIN + 2 = 9
[main] Use shell command "nice" to increase prio of t3.
[main] If it works, it will run again. The "hint" cmd can be useful.
> main(): This is RIOT! (Version: 2022.01-devel-305-ga9249-core/change_prio)
[t3] Setting my priority to THREAD_PRIORITY_MAIN + 2 = 9
[main] Use shell command "nice" to increase prio of t3.
[main] If it works, it will run again. The "hint" cmd can be useful.
> hint

> 
> hint
Run "nice 3 6"
> nice 3 6
nice 3 6
[t3] Running again.
make: Leaving directory '/home/maribu/Repos/software/RIOT/tests/sched_change_priority'

$ echo $?
0

Issues/PRs references

#7445

[kaspar030]

LGTM, let's get some experience for this.
Please uncrustify and squash!

[fjmolinas]

This might need a rebase to pass static checks when #17104 is in...

[maribu]

This might need a rebase to pass static checks when #17104 is in...

Did so just in case. Also added a Makefile.ci and squashed it right in.

[benpicco]

If @kaspar030 is OK with it on a conceptual level, the change looks goodⁿᶦᶜᵉ to me.

[kaspar030]

There's a slight performance drop (bench_thread_flags_pingpong on nrf52840dk):

main(): This is RIOT! (Version: 2022.01-devel-330-gea1f4-HEAD)
main starting
{ "result" : 112675, "ticks" : 568 }
Help: Press s to start test, r to print it is ready
START
main(): This is RIOT! (Version: 2022.01-devel-333-g034bdf-pr17093)
main starting
{ "result" : 111304, "ticks" : 575 }

(HEAD is the master fork point).

It's ~1%. So room for getting some of that back in the future. :)

[kaspar030]

ACK.

[kaspar030]

Let me suggest a rebase to get a current CI run. triggering CI.

[kfessel]

there seems to be a slight problem with that Python f-strings (introduced in Python 3.6)

The only test user in master of that python feature in master is the test gnrc_dhcpv6_client, but that is a test with config and therefore not run by murdock

[fjmolinas]

Let's not stall this one because the python version in rpi is old...

[maribu]

I squashed the suggested fix right in to save a CI cycle.

[benpicco]

Only the usual run_test/tests/pkg_mbedtls/samr21-xpro:gnu is failing.