This has KString, KBuffer, DoubleBuffer, KBufferBuilder, IOWindow,
UserOrKernelBuffer and ScopedCritical classes being moved to the
Kernel/Library subdirectory.
Also, move the panic and assertions handling code to that directory.
These were stored in a bunch of places. The main one that's a bit iffy
is the Mutex::m_holder one, which I'm going to simplify in a subsequent
commit.
In Plan9FS and WorkQueue, we can't make the NNRPs const due to
initialization order problems. That's probably doable with further
cleanup, but left as an exercise for our future selves.
Before starting this, I expected the thread blockers to be a problem,
but as it turns out they were super straightforward (for once!) as they
don't mutate the thread after initiating a block, so they can just use
simple const-ified NNRPs.
There was only one permanent storage location for these: as a member
in the Mount class.
That member is never modified after Mount initialization, so we don't
need to worry about races there.
This step would ideally not have been necessary (increases amount of
refactoring and templates necessary, which in turn increases build
times), but it gives us a couple of nice properties:
- SpinlockProtected inside Singleton (a very common combination) can now
obtain any lock rank just via the template parameter. It was not
previously possible to do this with SingletonInstanceCreator magic.
- SpinlockProtected's lock rank is now mandatory; this is the majority
of cases and allows us to see where we're still missing proper ranks.
- The type already informs us what lock rank a lock has, which aids code
readability and (possibly, if gdb cooperates) lock mismatch debugging.
- The rank of a lock can no longer be dynamic, which is not something we
wanted in the first place (or made use of). Locks randomly changing
their rank sounds like a disaster waiting to happen.
- In some places, we might be able to statically check that locks are
taken in the right order (with the right lock rank checking
implementation) as rank information is fully statically known.
This refactoring even more exposes the fact that Mutex has no lock rank
capabilites, which is not fixed here.
