From: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
To: Miguel Ojeda <ojeda@kernel.org>
Cc: "Wedson Almeida Filho" <wedsonaf@gmail.com>,
"Alex Gaynor" <alex.gaynor@gmail.com>,
"Boqun Feng" <boqun.feng@gmail.com>,
"Gary Guo" <gary@garyguo.net>,
"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
"Benno Lossin" <benno.lossin@proton.me>,
"Andreas Hindborg" <a.hindborg@samsung.com>,
"Alice Ryhl" <aliceryhl@google.com>,
"Masahiro Yamada" <masahiroy@kernel.org>,
linux-kbuild@vger.kernel.org, rust-for-linux@vger.kernel.org,
linux-kernel@vger.kernel.org, patches@lists.linux.dev
Subject: Re: [PATCH 1/2] kbuild: mark `rustc` (and others) invocations as recursive
Date: Thu, 29 Feb 2024 22:33:18 +0100 [thread overview]
Message-ID: <CANiq72nPiVDV2WY_jCuONz_arWRVyMMiRT5iVb=2xqoXnZYW+g@mail.gmail.com> (raw)
In-Reply-To: <20240217002638.57373-1-ojeda@kernel.org>
On Sat, Feb 17, 2024 at 1:26 AM Miguel Ojeda <ojeda@kernel.org> wrote:
>
> `rustc` (like Cargo) may take advantage of the jobserver at any time
> (e.g. for backend parallelism, or eventually frontend too). In the kernel,
> we call `rustc` with `-Ccodegen-units=1` (and `-Zthreads` is 1 so far),
> so we do not expect parallelism. However, in the upcoming Rust 1.76.0, a
> warning is emitted by `rustc` when it cannot connect to the jobserver it
> was passed (in many cases, but not all: compiling and `--print sysroot`
> do, but `--version` does not). And given GNU Make always passes
> the jobserver in the environment variable (even when a line is deemed
> non-recursive), `rustc` will end up complaining about it (in particular
> in Make 4.3 where there is only the simple pipe jobserver style).
>
> One solution is to remove the jobserver from `MAKEFLAGS`. However, we
> can mark the lines with calls to `rustc` (and Cargo) as recursive, which
> looks simpler. This is what is now documented and recommended by `rustc`
> and allows us to be ready for the time we may use parallelism inside
> `rustc` (potentially now, if a user passes `-Zthreads`). Thus do so.
>
> Similarly, do the same for `rustdoc` and `cargo` calls.
>
> Finally, there is one case that the solution does not cover, which is the
> `$(shell ...)` call we have. Thus, for that one, set an empty `MAKEFLAGS`
> environment variable.
>
> Link: https://github.com/rust-lang/rust/issues/120515
> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Applied (i.e. including the upgrade to 1.76.0) to `rust-next` --
thanks everyone!
[ Reworded to add link to PR documenting the recommendation. ]
Cheers,
Miguel
prev parent reply other threads:[~2024-02-29 21:33 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-17 0:26 [PATCH 1/2] kbuild: mark `rustc` (and others) invocations as recursive Miguel Ojeda
2024-02-17 0:26 ` [PATCH 2/2] rust: upgrade to Rust 1.76.0 Miguel Ojeda
2024-02-17 5:57 ` Boqun Feng
2024-02-19 9:09 ` Alice Ryhl
2024-02-19 9:52 ` [PATCH 1/2] kbuild: mark `rustc` (and others) invocations as recursive Masahiro Yamada
2024-02-29 21:33 ` Miguel Ojeda [this message]
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