From ecab4115c44cc50fc7320bef9c19ac01ad43c785 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Sat, 17 Feb 2024 01:26:37 +0100 Subject: 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 `$(shell ...)` call we have. Thus, for that one, set an empty `MAKEFLAGS` environment variable. Link: https://github.com/rust-lang/rust/issues/120515 [1] Acked-by: Masahiro Yamada Link: https://github.com/rust-lang/rust/pull/121564 [2] Link: https://lore.kernel.org/r/20240217002638.57373-1-ojeda@kernel.org [ Reworded to add link to PR documenting the recommendation. ] Signed-off-by: Miguel Ojeda --- rust/Makefile | 48 ++++++++++++++++++++++++------------------------ 1 file changed, 24 insertions(+), 24 deletions(-) (limited to 'rust') diff --git a/rust/Makefile b/rust/Makefile index 9d2a16cc91cb4..a78fcf4004b02 100644 --- a/rust/Makefile +++ b/rust/Makefile @@ -40,7 +40,7 @@ obj-$(CONFIG_RUST_KERNEL_DOCTESTS) += doctests_kernel_generated_kunit.o ifdef CONFIG_RUST # `$(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) 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 \ --extern proc_macro 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: $(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 - $(call if_changed,rustdoc) + +$(call if_changed,rustdoc) # We need to allow `rustdoc::broken_intra_doc_links` because some # `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) \ -Arustdoc::broken_intra_doc_links 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 \ --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-compiler_builtins rustdoc-alloc $(obj)/libmacros.so \ $(obj)/bindings.o FORCE - $(call if_changed,rustdoc) + +$(call if_changed,rustdoc) quiet_cmd_rustc_test_library = RUSTC TL $< cmd_rustc_test_library = \ @@ -146,18 +146,18 @@ quiet_cmd_rustc_test_library = RUSTC TL $< --crate-name $(subst rusttest-,,$(subst rusttestlib-,,$@)) $< 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_test_library_proc = yes 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 - $(call if_changed,rustc_test_library) + +$(call if_changed,rustc_test_library) 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 $< cmd_rustdoc_test = \ @@ -189,7 +189,7 @@ quiet_cmd_rustdoc_test_kernel = RUSTDOC TK $< $(src)/kernel/lib.rs $(obj)/kernel.o \ $(objtree)/scripts/rustdoc_test_builder \ $(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, # 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 rusttest-prepare: FORCE - $(call if_changed,rustsysroot) + +$(call if_changed,rustsysroot) rusttest-macros: private rustc_target_flags = --extern proc_macro rusttest-macros: private rustdoc_test_target_flags = --crate-type proc-macro rusttest-macros: $(src)/macros/lib.rs rusttest-prepare FORCE - $(call if_changed,rustc_test) - $(call if_changed,rustdoc_test) + +$(call if_changed,rustc_test) + +$(call if_changed,rustdoc_test) rusttest-kernel: private rustc_target_flags = --extern alloc \ --extern build_error --extern macros --extern bindings --extern uapi rusttest-kernel: $(src)/kernel/lib.rs rusttest-prepare \ rusttestlib-build_error rusttestlib-macros rusttestlib-bindings \ rusttestlib-uapi FORCE - $(call if_changed,rustc_test) - $(call if_changed,rustc_test_library) + +$(call if_changed,rustc_test) + +$(call if_changed,rustc_test_library) ifdef CONFIG_CC_IS_CLANG 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 # 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 - $(call if_changed_dep,rustc_procmacro) + +$(call if_changed_dep,rustc_procmacro) quiet_cmd_rustc_library = $(if $(skip_clippy),RUSTC,$(RUSTC_OR_CLIPPY_QUIET)) L $@ 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_target_flags = $(core-cfgs) $(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: $(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_flags = -Dunreachable_pub $(obj)/alloc.o: private rustc_target_flags = $(alloc-cfgs) $(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 - $(call if_changed_dep,rustc_library) + +$(call if_changed_dep,rustc_library) $(obj)/bindings.o: $(src)/bindings/lib.rs \ $(obj)/compiler_builtins.o \ $(obj)/bindings/bindings_generated.rs \ $(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)/compiler_builtins.o \ $(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 \ --extern build_error --extern macros --extern bindings --extern uapi $(obj)/kernel.o: $(src)/kernel/lib.rs $(obj)/alloc.o $(obj)/build_error.o \ $(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 -- cgit 1.2.3-korg