kbuild: fix parallel build race caused by u-boot.cfg regeneration
Multiple people have reported intermittent build failure in parallel
building.
Kever Yang reported this issue some time ago [1], but I could not
get enough clue at that time.
This time, Richard Purdie provided a full build log [2], which was
very helpful for me to root-cause it.
The cause of the problem is commit 0d982c585330 ("Makefile: add
dependencies to regenerate u-boot.cfg when lost").
That commit added the 'cfg' as the prerequisite of the 'all' target,
so the parallel build tries to run it simultaneously, then regenerates
a symlink while building objects.
When u-boot.cfg is accidentally lost, let's rebuild it before
descending into any subdirectories.
Also, what is annoying is u-boot.cfg is currently regenerated every
time since it depends on FORCE. We can get rid of all the prerequisites
of u-boot.cfg because u-boot.cfg is rebuilt anyway as the byproduct of
auto.conf when a user updates the .config file.
[1] https://lists.denx.de/pipermail/u-boot/2018-June/330341.html
[2] https://autobuilder.yoctoproject.org/typhoon/#/builders/65/builds/160/steps/7/logs/step1b
Fixes: 0d982c585330 ("Makefile: add dependencies to regenerate u-boot.cfg when lost")
Reported-by: Kever Yang <kever.yang@rock-chips.com>
Reported-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/Makefile b/Makefile
index 6aa0896..47bf90b 100644
--- a/Makefile
+++ b/Makefile
@@ -534,7 +534,7 @@
@# Otherwise, 'make silentoldconfig' would be invoked twice.
$(Q)touch include/config/auto.conf
-u-boot.cfg spl/u-boot.cfg tpl/u-boot.cfg: include/config.h FORCE
+u-boot.cfg spl/u-boot.cfg tpl/u-boot.cfg:
$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.autoconf $(@)
-include include/autoconf.mk
@@ -910,7 +910,7 @@
cmd_cfgcheck = $(srctree)/scripts/check-config.sh $2 \
$(srctree)/scripts/config_whitelist.txt $(srctree)
-all: $(ALL-y) cfg
+all: $(ALL-y)
ifeq ($(CONFIG_DM_I2C_COMPAT)$(CONFIG_SANDBOX),y)
@echo >&2 "===================== WARNING ======================"
@echo >&2 "This board uses CONFIG_DM_I2C_COMPAT. Please remove"
@@ -1555,7 +1555,7 @@
endif
# prepare2 creates a makefile if using a separate output directory
-prepare2: prepare3 outputmakefile
+prepare2: prepare3 outputmakefile cfg
prepare1: prepare2 $(version_h) $(timestamp_h) \
include/config/auto.conf