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 /scripts/Makefile.build | |
| parent | rust: add `container_of!` macro (diff) | |
| download | linux-ecab4115c44cc50fc7320bef9c19ac01ad43c785.tar.xz linux-ecab4115c44cc50fc7320bef9c19ac01ad43c785.zip | |
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 'scripts/Makefile.build')
| -rw-r--r-- | scripts/Makefile.build | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/scripts/Makefile.build b/scripts/Makefile.build index dae447a1ad30..0fb7a785594c 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -290,7 +290,7 @@ quiet_cmd_rustc_o_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@ cmd_rustc_o_rs = $(rust_common_cmd) --emit=obj=$@ $< $(obj)/%.o: $(src)/%.rs FORCE - $(call if_changed_dep,rustc_o_rs) + +$(call if_changed_dep,rustc_o_rs) quiet_cmd_rustc_rsi_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@ cmd_rustc_rsi_rs = \ @@ -298,19 +298,19 @@ quiet_cmd_rustc_rsi_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@ command -v $(RUSTFMT) >/dev/null && $(RUSTFMT) $@ $(obj)/%.rsi: $(src)/%.rs FORCE - $(call if_changed_dep,rustc_rsi_rs) + +$(call if_changed_dep,rustc_rsi_rs) quiet_cmd_rustc_s_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@ cmd_rustc_s_rs = $(rust_common_cmd) --emit=asm=$@ $< $(obj)/%.s: $(src)/%.rs FORCE - $(call if_changed_dep,rustc_s_rs) + +$(call if_changed_dep,rustc_s_rs) quiet_cmd_rustc_ll_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@ cmd_rustc_ll_rs = $(rust_common_cmd) --emit=llvm-ir=$@ $< $(obj)/%.ll: $(src)/%.rs FORCE - $(call if_changed_dep,rustc_ll_rs) + +$(call if_changed_dep,rustc_ll_rs) # Compile assembler sources (.S) # --------------------------------------------------------------------------- |