The first half of the 6.6 merge window [LWN.net]

The first half of the 6.6 merge window

Posted Sep 11, 2023 18:06 UTC (Mon) by ojeda (subscriber, #143370)
In reply to: The first half of the 6.6 merge window by milesrout
Parent article: The first half of the 6.6 merge window

> That doesn't answer the question. It says "It remains to be decided how often the Rust version upgrades will land. Ideally we would track the latest Rust release, but it remains to be seen how other kernel developers feel about it." What is the actual policy?

It does answer the questions that gray_-_wolf posed.

As the webpage mentions, we are currently trying out upgrading to the latest Rust release as they land. So far, it has not been a problem for the kernel developers using Rust.

But, to be clear, as the webpage also says, this is just the policy before we can establish a minimum version. Being in the latest one will make it much easier to establish so when it happens, it makes development easier and allows us to give feedback to the Rust teams on the unstable features we need.

> Putting a language into the kernel that is so unstable that the "ideal" solution is to track the *latest release* is so insane I can't believe it's being seriously considered.

The Rust language is stable. Some features we need are not. I will add a note to the webpage to make it clear that Rust promises backwards compatibility (for the stable language).

And it is not an ideal solution: the webpage makes it clear that in the end we want to establish a policy similar to GCC, Clang or other tools used in the kernel.

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The first half of the 6.6 merge window

Posted Sep 11, 2023 18:34 UTC (Mon) by pizza (subscriber, #46) [Link] (4 responses)

> The Rust language is stable. Some features we need are not.

That strikes me as a distinction without a difference.

The first half of the 6.6 merge window

Posted Sep 11, 2023 19:25 UTC (Mon) by mb (subscriber, #50428) [Link] (3 responses)

Do you want to wait for all the gcc extensions used by the kernel to land in an official C standard before you can use such a kernel?
It's the same thing.

The first half of the 6.6 merge window

Posted Sep 11, 2023 20:32 UTC (Mon) by pizza (subscriber, #46) [Link] (2 responses)

> Do you want to wait for all the gcc extensions used by the kernel to land in an official C standard before you can use such a kernel? It's the same thing.

It's only the same thing if each kernel release required you to use the latest release of GCC because "C is stable but the features we need are not."

(Meanwhile, the kernel only requires GCC 5.1, which was released over eight years ago. So.. yeah, not the same thing at all)

The first half of the 6.6 merge window

Posted Sep 12, 2023 6:03 UTC (Tue) by Cyberax (✭ supporter ✭, #52523) [Link] (1 responses)

Some kernel features like control flow integrity checking or shadow stacks (just merged) require a much newer GCC.

Yes, Rust is even newer than that. But that's a distinction without a difference: some kernel features require very new toolchains.

The first half of the 6.6 merge window

Posted Sep 12, 2023 6:17 UTC (Tue) by mb (subscriber, #50428) [Link]

Correct.
Some Distributions even used to ship a special gcc compiler just for compiling the kernel.
The kernel has very special requirements. That's true for C and Rust alike.
And I really don't see why that would be a problem.