> Subject: kbuild: avoid too many execution of scripts/pahole-flags.sh executions? On Tue, Oct 17, 2023 at 07:37:40PM +0900, 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 exectuted more than 20 times during the kernel build executed > 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@xxxxxxxxxx> > --- Thanks, looks good to me! Reviewed-by: Nicolas Schier <n.schier@xxxxxx>
