Messages in this thread | | | Date | Sun, 22 Oct 2023 21:33:58 -0300 | Subject | Re: [bpf-next PATCH v2 2/4] kbuild: avoid too many execution of scripts/pahole-flags.sh | From | Martin Rodriguez Reboredo <> |
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On 10/18/23 12:19, Masahiro Yamada wrote: > scripts/pahole-flags.sh is executed so many times. > > You can check how many times it is invoked during the build, 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 suppressed... ] > > 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 the 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> > --- > [...] > @@ -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
Would've used a tab, for legibility sake.
> include-$(CONFIG_KASAN) += scripts/Makefile.kasan > include-$(CONFIG_KCSAN) += scripts/Makefile.kcsan > include-$(CONFIG_KMSAN) += scripts/Makefile.kmsan > [...] Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
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