Make cpuload correct and more efficient for all configurations of NuttX

[FreddieChopin]

Currently cpuload assumes there are only 2 static threads - idle and init, this
is true only for "basic" config of NuttX, as there can be 3 more static threads:
paging, work0 and work1 - depending on config. In such cases cpuload
would mistake one of them for init (which in fact is always last), giving
incorrect results to "top"

Signed-off-by: Freddie Chopin [email protected]

[LorenzMeier]

This will be merged on the next merge window, which likely is in 9 days. The contribution is highly appreciated.

[px4dev]

I think this is actually the wrong way to go about it.

Instead of statically configuring the 'magic' tasks, the sched_note_switch implementation should just create them lazily as and when it sees a task it doesn't recognise. This would insulate the code from changes in NuttX that might otherwise be confusing later.

[FreddieChopin]

It's better than current code anyway - so an improvement (;

[LorenzMeier]

Hi Freddie,

Sorry that it took forever. We were looking into fixing this more generic, but since we never got around to it we just should have applied the patch, and worked from there.

Thanks!