Commit 688931a5 authored by Masahiro Yamada's avatar Masahiro Yamada

kbuild: skip sub-make for in-tree build with GNU Make 4.x

Commit 2b50f7ab ("kbuild: add workaround for Debian make-kpkg")
annoyed people who want to wrap the top Makefile with GNUmakefile
to customize it for their use.

On second thought, we do not need to run the sub-make for in-tree
build with Make 4.x because the 'MAKEFLAGS += -rR' issue only happens
on GNU Make 3.x.

With this commit, people will get back their workflow, and the Debian
make-kpkg will still work.

Fixes: 2b50f7ab ("kbuild: add workaround for Debian make-kpkg")
Reported-by: 's avatarAndreas Schwab <>
Reported-by: 's avatarDavid Howells <>
Signed-off-by: 's avatarMasahiro Yamada <>
Tested-by: 's avatarAndreas Schwab <>
Tested-by: 's avatarDavid Howells <>
parent a75bb4eb
......@@ -31,26 +31,12 @@ _all:
# descending is started. They are now explicitly listed as the
# prepare rule.
# Ugly workaround for Debian make-kpkg:
# make-kpkg directly includes the top Makefile of Linux kernel. In such a case,
# skip sub-make to support debian_* targets in ruleset/, but
# displays warning to discourage such abusage.
ifneq ($(word 2, $(MAKEFILE_LIST)),)
$(warning Do not include top Makefile of Linux Kernel)
sub-make-done := 1
ifneq ($(sub-make-done),1)
# Do not use make's built-in rules and variables
# (this increases performance and avoids hard-to-debug behaviour)
# 'MAKEFLAGS += -rR' does not become immediately effective for old
# GNU Make versions. Cancel implicit rules for this Makefile.
$(lastword $(MAKEFILE_LIST)): ;
# Avoid funny character set dependencies
unexport LC_ALL
......@@ -153,6 +139,7 @@ $(if $(KBUILD_OUTPUT),, \
# 'sub-make' below.
MAKEFLAGS += --include-dir=$(CURDIR)
need-sub-make := 1
# Do not print "Entering directory ..." at all for in-tree build.
......@@ -160,6 +147,16 @@ MAKEFLAGS += --no-print-directory
endif # ifneq ($(KBUILD_OUTPUT),)
ifneq ($(filter 3.%,$(MAKE_VERSION)),)
# 'MAKEFLAGS += -rR' does not immediately become effective for GNU Make 3.x
# We need to invoke sub-make to avoid implicit rules in the top Makefile.
need-sub-make := 1
# Cancel implicit rules for this Makefile.
$(lastword $(MAKEFILE_LIST)): ;
ifeq ($(need-sub-make),1)
$(filter-out _all sub-make $(CURDIR)/Makefile, $(MAKECMDGOALS)) _all: sub-make
......@@ -171,8 +168,11 @@ sub-make:
-f $(CURDIR)/Makefile $(filter-out _all sub-make,$(MAKECMDGOALS))
else # sub-make-done
endif # need-sub-make
endif # sub-make-done
# We process the rest of the Makefile if this is the final invocation of make
ifeq ($(need-sub-make),)
# Do not print "Entering directory ...",
# but we want to display it when entering to the output directory
......@@ -1757,7 +1757,7 @@ existing-targets := $(wildcard $(sort $(targets)))
endif # ifeq ($(config-targets),1)
endif # ifeq ($(mixed-targets),1)
endif # sub-make-done
endif # need-sub-make
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