> its (C's) lack of any intrinsic support for concurrency
If you are writing the operating system kernel, who is going to give you concurrency support? Does rust running on the bare metal still have "spawn" and the other concurrency primitives?
They aren't language primitives; they're just part of the library. So presumably you'd implement them yourself using a little bit of inline assembler, and they'd then be on equal footing with the versions in the Rust standard library.
If you are writing the operating system kernel, who is going to give you concurrency support? Does rust running on the bare metal still have "spawn" and the other concurrency primitives?