Problem:
- Building with clang is broken because of the `struct` vs `class`
mismatch between the definition and declaration.
Solution:
- Change `class` to `struct` in the forward declaration.
When two processors send each others a SMP message at the same time
they need to process messages while waiting for delivery of the
message they just sent, or they will deadlock.
Problem:
- IPv4Address class cannot be used in a compile-time context.
- A union is used by initializing one of the members and reading the
non-active member. This is undefined behavior and not permitted in a
`constexpr` context.
Solution:
- Eliminate undefined behavior by changing to a simple `u32` for
storage instead of the union and performing mask/shift calculations
for obtaining the individual octets.
- Decorate functions with `constexpr` where possible. Currently string
formatting and optionals are not `constexpr`-capable so functions
using those are left out.
- Modify tests to validate functionality in a `constexpr` context in
addition to the run-time tests already being run. This ensures that
functionality is the same in both contexts.
Previously we would iterate over all the live HeapBlocks in order to
learn if an arbitrary pointer-sized value was a pointer into a live
HeapBlock. This was quite time-consuming.
Instead of that, just put all the live HeapBlock*'s in a HashTable
and identify pointers by doing a bit-masked lookup into the table.
This is making me question the usefulness of application-global
shortcuts, but for now let's just prevent them from triggering while
you're looking at a modal message box..
This makes most operations thread safe, especially so that they
can safely be used in the Kernel. This includes obtaining a strong
reference from a weak reference, which now requires an explicit
call to WeakPtr::strong_ref(). Another major change is that
Weakable::make_weak_ref() may require the explicit target type.
Previously we used reinterpret_cast in WeakPtr, assuming that it
can be properly converted. But WeakPtr does not necessarily have
the knowledge to be able to do this. Instead, we now ask the class
itself to deliver a WeakPtr to the type that we want.
Also, WeakLink is no longer specific to a target type. The reason
for this is that we want to be able to safely convert e.g. WeakPtr<T>
to WeakPtr<U>, and before this we just reinterpret_cast the internal
WeakLink<T> to WeakLink<U>, which is a bold assumption that it would
actually produce the correct code. Instead, WeakLink now operates
on just a raw pointer and we only make those constructors/operators
available if we can verify that it can be safely cast.
In order to guarantee thread safety, we now use the least significant
bit in the pointer for locking purposes. This also means that only
properly aligned pointers can be used.
With this, `ntpquery` can adjust the system time without
making it jump.
A fun activity with this in:
0. Boot
1. Run `su`
2. Run `ntpquery -a` to adjust the time offset after boot
(usually around a second)
3. Keep running `ntpquery ; adjtime` to see how the offset
behind NTP and the remaining adjtime both shrink.
adjtime adjustment is large enough to make the time offset
go down by a bit, but we currently lose time quickly enough
that by the time adjtime is done, we've only corrected the
clock about halfway, and not all the way to zero. Goto 2.
So this isn't all that great yet, but I think it's good enough
to think about turning this into a permanently running service next.
It's a thin userland wrapper around adjtime(2). It can be used
to view current pending time adjustments, and root can use it to
smoothly adjust the system time.
As far as I can tell, other systems don't have a userland utility
for this, but it seems useful. Useful enough that I'm adding it to
the lagom build so I can use it on my linux box too :)
Most systems (Linux, OpenBSD) adjust 0.5 ms per second, or 0.5 us per
1 ms tick. That is, the clock is sped up or slowed down by at most
0.05%. This means adjusting the clock by 1 s takes 2000 s, and the
clock an be adjusted by at most 1.8 s per hour.
FreeBSD adjusts 5 ms per second if the remaining time adjustment is
>= 1 s (0.5%) , else it adjusts by 0.5 ms as well. This allows adjusting
by (almost) 18 s per hour.
Since Serenity OS can lose more than 22 s per hour (#3429), this
picks an adjustment rate up to 1% for now. This allows us to
adjust up to 36s per hour, which should be sufficient to adjust
the clock fast enough to keep up with how much time the clock
currently loses. Once we have a fancier NTP implementation that can
adjust tick rate in addition to offset, we can think about reducing
this.
adjtime is a bit old-school and most current POSIX-y OSs instead
implement adjtimex/ntp_adjtime, but a) we have to start somewhere
b) ntp_adjtime() is a fairly gnarly API. OpenBSD's adjfreq looks
like it might provide similar functionality with a nicer API. But
before worrying about all this, it's probably a good idea to get
to a place where the kernel APIs are (barely) good enough so that
we can write an ntp service, and once we have that we should write
a way to automatically evaluate how well it keeps the time adjusted,
and only then should we add improvements ot the adjustment mechanism.
This makes the game less deterministic and more fun. The "physics"
definitely feel a little goofy, and I'm sure they can be greatly
improved, but still it's already better. :^)
Set the max height of the text_rect to be the height difference
between two icons. Calculate the number of text lines that can be
displayed in this height, and display only that many.
This addresses the issue first enountered in #3644. If a path is
first unveiled with "c" permissions, we should NOT return ENOENT
if the node does not exist on the disk, as the program will most
likely be creating it at a later time.
Problem:
- There is no direct unit testing of the IPv4Address functionality
which makes refactoring difficult.
Solution:
- Add unit tests to cover the current functionality of
IPv4Address. This will allow future refactorings with confidence.
