The global allocator panics when out of memory rather than returning an
errors. In addition there are plenty of other places where we don't
handle allocation failure anyway. At some point in the future we should
systematically handle out of memory conditions, but until then let's not
pretend we do and get rid of the usage of the unstable allocator_api
feature that is unlikely to get stabilized any time soon.
This avoids the need to explicitly set a logger early during boot, which
reduces the amount of moving parts that could go wrong slightly. And it
cuts the kernel image size by 13kb.
Previously the deallocation would be rounded to the next power of two
preventing partial deallocation. But more importantly previously trying
to free phys_contiguous frames while another processes still borrows
them. Now this should just cause the deallocation to be delayed.
Before it was first add_ref'ed by `borrow_frame_enforce_rw_allocated`,
manually and then by `allocated_shared_one_page`.
Now it is only done by `borrow_frame_enforce_rw_allocated` and does not
get unref-ed as take() is called on the returned `RaiiFrame`.
Now the page is manually mapped and an `Allocated` type grant is
constructed (synonymous to `MAP_PRIVATE`). Before by using `allocated_shared_one_page`
an `AllocatedShared` provided grant was constructed (synonymous to
`MAP_SHARED`), which was wrong as the TCB would've not got CoW-ed
after fork(), making the Tcb malformed.
Signed-off-by: Anhad Singh <andypython@protonmail.com>
* Add documentation and more code comments to `src/context/switch.rs`
* Eliminate a `context.wake.expect(...)` where `context.wake.is_some()`
* Eliminate a TODO item about updating contexts' timestamps in `switch_to`
* Eliminate a dangling `else { continue }` at the end of the loop that iterates
on contexts
Jeremy Soller