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kbuild: mark rustc (and others) invocations as recursive

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`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>
This commit is contained in:
Miguel Ojeda 2024-02-17 01:26:37 +01:00
parent e944171070
commit ecab4115c4
4 changed files with 31 additions and 31 deletions
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4
Makefile
View File

@ -1197,7 +1197,7 @@ prepare0: archprepare
# All the preparing.. # All the preparing..
prepare: prepare0 prepare: prepare0
ifdef CONFIG_RUST 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 $(Q)$(MAKE) $(build)=rust
endif endif
@ -1707,7 +1707,7 @@ $(DOC_TARGETS):
# "Is Rust available?" target # "Is Rust available?" target
PHONY += rustavailable PHONY += rustavailable
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 # Documentation target
# #

48
rust/Makefile
View File

@ -40,7 +40,7 @@ obj-$(CONFIG_RUST_KERNEL_DOCTESTS) += doctests_kernel_generated_kunit.o
ifdef CONFIG_RUST ifdef CONFIG_RUST
# `$(rust_flags)` is passed in case the user added `--sysroot`. # `$(rust_flags)` is passed in case the user added `--sysroot`.
rustc_sysroot := $(shell $(RUSTC) $(rust_flags) --print sysroot) rustc_sysroot := $(shell MAKEFLAGS= $(RUSTC) $(rust_flags) --print sysroot)
rustc_host_target := $(shell $(RUSTC) --version --verbose | grep -F 'host: ' | cut -d' ' -f2) rustc_host_target := $(shell $(RUSTC) --version --verbose | grep -F 'host: ' | cut -d' ' -f2)
RUST_LIB_SRC ?= $(rustc_sysroot)/lib/rustlib/src/rust/library RUST_LIB_SRC ?= $(rustc_sysroot)/lib/rustlib/src/rust/library
@ -108,14 +108,14 @@ rustdoc-macros: private rustdoc_host = yes
rustdoc-macros: private rustc_target_flags = --crate-type proc-macro \ rustdoc-macros: private rustc_target_flags = --crate-type proc-macro \
--extern proc_macro --extern proc_macro
rustdoc-macros: $(src)/macros/lib.rs FORCE rustdoc-macros: $(src)/macros/lib.rs FORCE
$(call if_changed,rustdoc) +$(call if_changed,rustdoc)
rustdoc-core: private rustc_target_flags = $(core-cfgs) rustdoc-core: private rustc_target_flags = $(core-cfgs)
rustdoc-core: $(RUST_LIB_SRC)/core/src/lib.rs FORCE rustdoc-core: $(RUST_LIB_SRC)/core/src/lib.rs FORCE
$(call if_changed,rustdoc) +$(call if_changed,rustdoc)
rustdoc-compiler_builtins: $(src)/compiler_builtins.rs rustdoc-core FORCE rustdoc-compiler_builtins: $(src)/compiler_builtins.rs rustdoc-core FORCE
$(call if_changed,rustdoc) +$(call if_changed,rustdoc)
# We need to allow `rustdoc::broken_intra_doc_links` because some # We need to allow `rustdoc::broken_intra_doc_links` because some
# `no_global_oom_handling` functions refer to non-`no_global_oom_handling` # `no_global_oom_handling` functions refer to non-`no_global_oom_handling`
@ -124,7 +124,7 @@ rustdoc-compiler_builtins: $(src)/compiler_builtins.rs rustdoc-core FORCE
rustdoc-alloc: private rustc_target_flags = $(alloc-cfgs) \ rustdoc-alloc: private rustc_target_flags = $(alloc-cfgs) \
-Arustdoc::broken_intra_doc_links -Arustdoc::broken_intra_doc_links
rustdoc-alloc: $(src)/alloc/lib.rs rustdoc-core rustdoc-compiler_builtins FORCE rustdoc-alloc: $(src)/alloc/lib.rs rustdoc-core rustdoc-compiler_builtins FORCE
$(call if_changed,rustdoc) +$(call if_changed,rustdoc)
rustdoc-kernel: private rustc_target_flags = --extern alloc \ rustdoc-kernel: private rustc_target_flags = --extern alloc \
--extern build_error --extern macros=$(objtree)/$(obj)/libmacros.so \ --extern build_error --extern macros=$(objtree)/$(obj)/libmacros.so \
@ -132,7 +132,7 @@ rustdoc-kernel: private rustc_target_flags = --extern alloc \
rustdoc-kernel: $(src)/kernel/lib.rs rustdoc-core rustdoc-macros \ rustdoc-kernel: $(src)/kernel/lib.rs rustdoc-core rustdoc-macros \
rustdoc-compiler_builtins rustdoc-alloc $(obj)/libmacros.so \ rustdoc-compiler_builtins rustdoc-alloc $(obj)/libmacros.so \
$(obj)/bindings.o FORCE $(obj)/bindings.o FORCE
$(call if_changed,rustdoc) +$(call if_changed,rustdoc)
quiet_cmd_rustc_test_library = RUSTC TL $< quiet_cmd_rustc_test_library = RUSTC TL $<
cmd_rustc_test_library = \ cmd_rustc_test_library = \
@ -146,18 +146,18 @@ quiet_cmd_rustc_test_library = RUSTC TL $<
--crate-name $(subst rusttest-,,$(subst rusttestlib-,,$@)) $< --crate-name $(subst rusttest-,,$(subst rusttestlib-,,$@)) $<
rusttestlib-build_error: $(src)/build_error.rs rusttest-prepare FORCE rusttestlib-build_error: $(src)/build_error.rs rusttest-prepare FORCE
$(call if_changed,rustc_test_library) +$(call if_changed,rustc_test_library)
rusttestlib-macros: private rustc_target_flags = --extern proc_macro rusttestlib-macros: private rustc_target_flags = --extern proc_macro
rusttestlib-macros: private rustc_test_library_proc = yes rusttestlib-macros: private rustc_test_library_proc = yes
rusttestlib-macros: $(src)/macros/lib.rs rusttest-prepare FORCE rusttestlib-macros: $(src)/macros/lib.rs rusttest-prepare FORCE
$(call if_changed,rustc_test_library) +$(call if_changed,rustc_test_library)
rusttestlib-bindings: $(src)/bindings/lib.rs rusttest-prepare FORCE rusttestlib-bindings: $(src)/bindings/lib.rs rusttest-prepare FORCE
$(call if_changed,rustc_test_library) +$(call if_changed,rustc_test_library)
rusttestlib-uapi: $(src)/uapi/lib.rs rusttest-prepare FORCE rusttestlib-uapi: $(src)/uapi/lib.rs rusttest-prepare FORCE
$(call if_changed,rustc_test_library) +$(call if_changed,rustc_test_library)
quiet_cmd_rustdoc_test = RUSTDOC T $< quiet_cmd_rustdoc_test = RUSTDOC T $<
cmd_rustdoc_test = \ cmd_rustdoc_test = \
@ -189,7 +189,7 @@ quiet_cmd_rustdoc_test_kernel = RUSTDOC TK $<
$(src)/kernel/lib.rs $(obj)/kernel.o \ $(src)/kernel/lib.rs $(obj)/kernel.o \
$(objtree)/scripts/rustdoc_test_builder \ $(objtree)/scripts/rustdoc_test_builder \
$(objtree)/scripts/rustdoc_test_gen FORCE $(objtree)/scripts/rustdoc_test_gen FORCE
$(call if_changed,rustdoc_test_kernel) +$(call if_changed,rustdoc_test_kernel)
# We cannot use `-Zpanic-abort-tests` because some tests are dynamic, # We cannot use `-Zpanic-abort-tests` because some tests are dynamic,
# so for the moment we skip `-Cpanic=abort`. # so for the moment we skip `-Cpanic=abort`.
@ -254,21 +254,21 @@ quiet_cmd_rustsysroot = RUSTSYSROOT
$(objtree)/$(obj)/test/sysroot/lib/rustlib/$(rustc_host_target)/lib $(objtree)/$(obj)/test/sysroot/lib/rustlib/$(rustc_host_target)/lib
rusttest-prepare: FORCE rusttest-prepare: FORCE
$(call if_changed,rustsysroot) +$(call if_changed,rustsysroot)
rusttest-macros: private rustc_target_flags = --extern proc_macro rusttest-macros: private rustc_target_flags = --extern proc_macro
rusttest-macros: private rustdoc_test_target_flags = --crate-type proc-macro rusttest-macros: private rustdoc_test_target_flags = --crate-type proc-macro
rusttest-macros: $(src)/macros/lib.rs rusttest-prepare FORCE rusttest-macros: $(src)/macros/lib.rs rusttest-prepare FORCE
$(call if_changed,rustc_test) +$(call if_changed,rustc_test)
$(call if_changed,rustdoc_test) +$(call if_changed,rustdoc_test)
rusttest-kernel: private rustc_target_flags = --extern alloc \ rusttest-kernel: private rustc_target_flags = --extern alloc \
--extern build_error --extern macros --extern bindings --extern uapi --extern build_error --extern macros --extern bindings --extern uapi
rusttest-kernel: $(src)/kernel/lib.rs rusttest-prepare \ rusttest-kernel: $(src)/kernel/lib.rs rusttest-prepare \
rusttestlib-build_error rusttestlib-macros rusttestlib-bindings \ rusttestlib-build_error rusttestlib-macros rusttestlib-bindings \
rusttestlib-uapi FORCE rusttestlib-uapi FORCE
$(call if_changed,rustc_test) +$(call if_changed,rustc_test)
$(call if_changed,rustc_test_library) +$(call if_changed,rustc_test_library)
ifdef CONFIG_CC_IS_CLANG ifdef CONFIG_CC_IS_CLANG
bindgen_c_flags = $(c_flags) bindgen_c_flags = $(c_flags)
@ -396,7 +396,7 @@ quiet_cmd_rustc_procmacro = $(RUSTC_OR_CLIPPY_QUIET) P $@
# Therefore, to get `libmacros.so` automatically recompiled when the compiler # Therefore, to get `libmacros.so` automatically recompiled when the compiler
# version changes, we add `core.o` as a dependency (even if it is not needed). # version changes, we add `core.o` as a dependency (even if it is not needed).
$(obj)/libmacros.so: $(src)/macros/lib.rs $(obj)/core.o FORCE $(obj)/libmacros.so: $(src)/macros/lib.rs $(obj)/core.o FORCE
$(call if_changed_dep,rustc_procmacro) +$(call if_changed_dep,rustc_procmacro)
quiet_cmd_rustc_library = $(if $(skip_clippy),RUSTC,$(RUSTC_OR_CLIPPY_QUIET)) L $@ quiet_cmd_rustc_library = $(if $(skip_clippy),RUSTC,$(RUSTC_OR_CLIPPY_QUIET)) L $@
cmd_rustc_library = \ cmd_rustc_library = \
@ -435,36 +435,36 @@ $(obj)/core.o: private skip_flags = -Dunreachable_pub
$(obj)/core.o: private rustc_objcopy = $(foreach sym,$(redirect-intrinsics),--redefine-sym $(sym)=__rust$(sym)) $(obj)/core.o: private rustc_objcopy = $(foreach sym,$(redirect-intrinsics),--redefine-sym $(sym)=__rust$(sym))
$(obj)/core.o: private rustc_target_flags = $(core-cfgs) $(obj)/core.o: private rustc_target_flags = $(core-cfgs)
$(obj)/core.o: $(RUST_LIB_SRC)/core/src/lib.rs scripts/target.json FORCE $(obj)/core.o: $(RUST_LIB_SRC)/core/src/lib.rs scripts/target.json FORCE
$(call if_changed_dep,rustc_library) +$(call if_changed_dep,rustc_library)
$(obj)/compiler_builtins.o: private rustc_objcopy = -w -W '__*' $(obj)/compiler_builtins.o: private rustc_objcopy = -w -W '__*'
$(obj)/compiler_builtins.o: $(src)/compiler_builtins.rs $(obj)/core.o FORCE $(obj)/compiler_builtins.o: $(src)/compiler_builtins.rs $(obj)/core.o FORCE
$(call if_changed_dep,rustc_library) +$(call if_changed_dep,rustc_library)
$(obj)/alloc.o: private skip_clippy = 1 $(obj)/alloc.o: private skip_clippy = 1
$(obj)/alloc.o: private skip_flags = -Dunreachable_pub $(obj)/alloc.o: private skip_flags = -Dunreachable_pub
$(obj)/alloc.o: private rustc_target_flags = $(alloc-cfgs) $(obj)/alloc.o: private rustc_target_flags = $(alloc-cfgs)
$(obj)/alloc.o: $(src)/alloc/lib.rs $(obj)/compiler_builtins.o FORCE $(obj)/alloc.o: $(src)/alloc/lib.rs $(obj)/compiler_builtins.o FORCE
$(call if_changed_dep,rustc_library) +$(call if_changed_dep,rustc_library)
$(obj)/build_error.o: $(src)/build_error.rs $(obj)/compiler_builtins.o FORCE $(obj)/build_error.o: $(src)/build_error.rs $(obj)/compiler_builtins.o FORCE
$(call if_changed_dep,rustc_library) +$(call if_changed_dep,rustc_library)
$(obj)/bindings.o: $(src)/bindings/lib.rs \ $(obj)/bindings.o: $(src)/bindings/lib.rs \
$(obj)/compiler_builtins.o \ $(obj)/compiler_builtins.o \
$(obj)/bindings/bindings_generated.rs \ $(obj)/bindings/bindings_generated.rs \
$(obj)/bindings/bindings_helpers_generated.rs FORCE $(obj)/bindings/bindings_helpers_generated.rs FORCE
$(call if_changed_dep,rustc_library) +$(call if_changed_dep,rustc_library)
$(obj)/uapi.o: $(src)/uapi/lib.rs \ $(obj)/uapi.o: $(src)/uapi/lib.rs \
$(obj)/compiler_builtins.o \ $(obj)/compiler_builtins.o \
$(obj)/uapi/uapi_generated.rs FORCE $(obj)/uapi/uapi_generated.rs FORCE
$(call if_changed_dep,rustc_library) +$(call if_changed_dep,rustc_library)
$(obj)/kernel.o: private rustc_target_flags = --extern alloc \ $(obj)/kernel.o: private rustc_target_flags = --extern alloc \
--extern build_error --extern macros --extern bindings --extern uapi --extern build_error --extern macros --extern bindings --extern uapi
$(obj)/kernel.o: $(src)/kernel/lib.rs $(obj)/alloc.o $(obj)/build_error.o \ $(obj)/kernel.o: $(src)/kernel/lib.rs $(obj)/alloc.o $(obj)/build_error.o \
$(obj)/libmacros.so $(obj)/bindings.o $(obj)/uapi.o FORCE $(obj)/libmacros.so $(obj)/bindings.o $(obj)/uapi.o FORCE
$(call if_changed_dep,rustc_library) +$(call if_changed_dep,rustc_library)
endif # CONFIG_RUST endif # CONFIG_RUST

8
scripts/Makefile.build
View File

@ -290,7 +290,7 @@ quiet_cmd_rustc_o_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@
cmd_rustc_o_rs = $(rust_common_cmd) --emit=obj=$@ $< cmd_rustc_o_rs = $(rust_common_cmd) --emit=obj=$@ $<
$(obj)/%.o: $(src)/%.rs FORCE $(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) $@ quiet_cmd_rustc_rsi_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@
cmd_rustc_rsi_rs = \ 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) $@ command -v $(RUSTFMT) >/dev/null && $(RUSTFMT) $@
$(obj)/%.rsi: $(src)/%.rs FORCE $(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) $@ quiet_cmd_rustc_s_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@
cmd_rustc_s_rs = $(rust_common_cmd) --emit=asm=$@ $< cmd_rustc_s_rs = $(rust_common_cmd) --emit=asm=$@ $<
$(obj)/%.s: $(src)/%.rs FORCE $(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) $@ quiet_cmd_rustc_ll_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@
cmd_rustc_ll_rs = $(rust_common_cmd) --emit=llvm-ir=$@ $< cmd_rustc_ll_rs = $(rust_common_cmd) --emit=llvm-ir=$@ $<
$(obj)/%.ll: $(src)/%.rs FORCE $(obj)/%.ll: $(src)/%.rs FORCE
$(call if_changed_dep,rustc_ll_rs) +$(call if_changed_dep,rustc_ll_rs)
# Compile assembler sources (.S) # Compile assembler sources (.S)
# --------------------------------------------------------------------------- # ---------------------------------------------------------------------------

2
scripts/Makefile.host
View File

@ -156,7 +156,7 @@ quiet_cmd_host-rust = HOSTRUSTC $@
cmd_host-rust = \ cmd_host-rust = \
$(HOSTRUSTC) $(hostrust_flags) --emit=link=$@ $< $(HOSTRUSTC) $(hostrust_flags) --emit=link=$@ $<
$(host-rust): $(obj)/%: $(src)/%.rs FORCE $(host-rust): $(obj)/%: $(src)/%.rs FORCE
$(call if_changed_dep,host-rust) +$(call if_changed_dep,host-rust)
targets += $(host-csingle) $(host-cmulti) $(host-cobjs) \ targets += $(host-csingle) $(host-cmulti) $(host-cobjs) \
$(host-cxxmulti) $(host-cxxobjs) $(host-rust) $(host-cxxmulti) $(host-cxxobjs) $(host-rust)