diff options
| author | Miguel Ojeda <ojeda@kernel.org> | 2024-02-17 01:26:37 +0100 |
|---|---|---|
| committer | Miguel Ojeda <ojeda@kernel.org> | 2024-02-29 22:16:38 +0100 |
| commit | ecab4115c44cc50fc7320bef9c19ac01ad43c785 (patch) | |
| tree | 0b66eb9e69599a4eb0b8ed60ef91f91fae2442d5 /Makefile | |
| parent | e944171070b65521c0513c01c56174ec8fd7d249 (diff) | |
kbuild: mark `rustc` (and others) invocations as recursive
`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` [1] 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 being documented as a recommendation in `rustc`
[2] 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 [1]
Acked-by: Masahiro Yamada <masahiroy@kernel.org>
Link: https://github.com/rust-lang/rust/pull/121564 [2]
Link: https://lore.kernel.org/r/20240217002638.57373-1-ojeda@kernel.org
[ Reworded to add link to PR documenting the recommendation. ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Diffstat (limited to 'Makefile')
| -rw-r--r-- | Makefile | 4 |
1 files changed, 2 insertions, 2 deletions
@@ -1197,7 +1197,7 @@ prepare0: archprepare # All the preparing.. prepare: prepare0 ifdef CONFIG_RUST - $(Q)$(CONFIG_SHELL) $(srctree)/scripts/rust_is_available.sh + +$(Q)$(CONFIG_SHELL) $(srctree)/scripts/rust_is_available.sh $(Q)$(MAKE) $(build)=rust endif @@ -1707,7 +1707,7 @@ $(DOC_TARGETS): # "Is Rust available?" target PHONY += rustavailable rustavailable: - $(Q)$(CONFIG_SHELL) $(srctree)/scripts/rust_is_available.sh && echo "Rust is available!" + +$(Q)$(CONFIG_SHELL) $(srctree)/scripts/rust_is_available.sh && echo "Rust is available!" # Documentation target # |