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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 /Makefile | |
| parent | 7f6d8f7e43fb516f060cf71672a922031aa5faa9 (diff) | |
| download | linux-stable-72d091846de935e0942a8a0f1fe24ff739d85d76.tar.gz linux-stable-72d091846de935e0942a8a0f1fe24ff739d85d76.tar.bz2 linux-stable-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 'Makefile')
| -rw-r--r-- | Makefile | 4 |
1 files changed, 1 insertions, 3 deletions
@@ -513,8 +513,6 @@ LZ4 = lz4c XZ = xz ZSTD = zstd -PAHOLE_FLAGS = $(shell PAHOLE=$(PAHOLE) $(srctree)/scripts/pahole-flags.sh) - CHECKFLAGS := -D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__ \ -Wbitwise -Wno-return-void -Wno-unknown-attribute $(CF) NOSTDINC_FLAGS := @@ -605,7 +603,6 @@ export KBUILD_RUSTFLAGS RUSTFLAGS_KERNEL RUSTFLAGS_MODULE export KBUILD_AFLAGS AFLAGS_KERNEL AFLAGS_MODULE export KBUILD_AFLAGS_MODULE KBUILD_CFLAGS_MODULE KBUILD_RUSTFLAGS_MODULE KBUILD_LDFLAGS_MODULE export KBUILD_AFLAGS_KERNEL KBUILD_CFLAGS_KERNEL KBUILD_RUSTFLAGS_KERNEL -export PAHOLE_FLAGS # Files to ignore in find ... statements @@ -1002,6 +999,7 @@ KBUILD_CPPFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=) # include additional Makefiles when needed include-y := scripts/Makefile.extrawarn include-$(CONFIG_DEBUG_INFO) += scripts/Makefile.debug +include-$(CONFIG_DEBUG_INFO_BTF)+= scripts/Makefile.btf include-$(CONFIG_KASAN) += scripts/Makefile.kasan include-$(CONFIG_KCSAN) += scripts/Makefile.kcsan include-$(CONFIG_KMSAN) += scripts/Makefile.kmsan |