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| author | Masahiro Yamada <masahiroy@kernel.org> | 2023-10-19 00:19:48 +0900 |
|---|---|---|
| committer | Masahiro Yamada <masahiroy@kernel.org> | 2023-10-28 21:10:08 +0900 |
| commit | 72d091846de935e0942a8a0f1fe24ff739d85d76 (patch) | |
| tree | 2b5a31b1ed6279d40ffae00e0bea85898bd46373 /scripts/Makefile.btf | |
| parent | 7f6d8f7e43fb516f060cf71672a922031aa5faa9 (diff) | |
| download | linux-72d091846de935e0942a8a0f1fe24ff739d85d76.tar.gz linux-72d091846de935e0942a8a0f1fe24ff739d85d76.tar.bz2 linux-72d091846de935e0942a8a0f1fe24ff739d85d76.zip | |
kbuild: avoid too many execution of scripts/pahole-flags.sh
scripts/pahole-flags.sh is executed so many times.
You can confirm it, as follows:
$ cat <<EOF >> scripts/pahole-flags.sh
> echo "scripts/pahole-flags.sh was executed" >&2
> EOF
$ make -s
scripts/pahole-flags.sh was executed
scripts/pahole-flags.sh was executed
scripts/pahole-flags.sh was executed
scripts/pahole-flags.sh was executed
scripts/pahole-flags.sh was executed
[ lots of repeated lines... ]
This scripts is executed more than 20 times during the kernel build
because PAHOLE_FLAGS is a recursively expanded variable and exported
to sub-processes.
With GNU Make >= 4.4, it is executed more than 60 times because
exported variables are also passed to other $(shell ) invocations.
Without careful coding, it is known to cause an exponential fork
explosion. [1]
The use of $(shell ) in an exported recursive variable is likely wrong
because $(shell ) is always evaluated due to the 'export' keyword, and
the evaluation can occur multiple times by the nature of recursive
variables.
Convert the shell script to a Makefile, which is included only when
CONFIG_DEBUG_INFO_BTF=y.
[1]: https://savannah.gnu.org/bugs/index.php?64746
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
Tested-by: Alan Maguire <alan.maguire@oracle.com>
Reviewed-by: Nicolas Schier <n.schier@avm.de>
Tested-by: Miguel Ojeda <ojeda@kernel.org>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Diffstat (limited to 'scripts/Makefile.btf')
| -rw-r--r-- | scripts/Makefile.btf | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/scripts/Makefile.btf b/scripts/Makefile.btf new file mode 100644 index 000000000000..82377e470aed --- /dev/null +++ b/scripts/Makefile.btf @@ -0,0 +1,19 @@ +# SPDX-License-Identifier: GPL-2.0 + +pahole-ver := $(CONFIG_PAHOLE_VERSION) +pahole-flags-y := + +# pahole 1.18 through 1.21 can't handle zero-sized per-CPU vars +ifeq ($(call test-le, $(pahole-ver), 121),y) +pahole-flags-$(call test-ge, $(pahole-ver), 118) += --skip_encoding_btf_vars +endif + +pahole-flags-$(call test-ge, $(pahole-ver), 121) += --btf_gen_floats + +pahole-flags-$(call test-ge, $(pahole-ver), 122) += -j + +pahole-flags-$(CONFIG_PAHOLE_HAS_LANG_EXCLUDE) += --lang_exclude=rust + +pahole-flags-$(call test-ge, $(pahole-ver), 125) += --skip_encoding_btf_inconsistent_proto --btf_gen_optimized + +export PAHOLE_FLAGS := $(pahole-flags-y) |