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ARC: build: move symlink creation to arch/arc/Makefile to avoid race

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If you run 'make uImage uImage.gz' with the parallel option, uImage.gz
will be created by two threads simultaneously.

This is because arch/arc/Makefile does not specify the dependency
between uImage and uImage.gz. Hence, GNU Make assumes they can be
built in parallel. One thread descends into arch/arc/boot/ to create
uImage, and another to create uImage.gz.

Please notice the same log is displayed twice in the following steps:

  $ export CROSS_COMPILE=<your-arc-compiler-prefix>
  $ make -s ARCH=arc defconfig
  $ make -j$(nproc) ARCH=arc uImage uImage.gz
  [ snip ]
    LD      vmlinux
    SORTTAB vmlinux
    SYSMAP  System.map
    OBJCOPY arch/arc/boot/vmlinux.bin
    OBJCOPY arch/arc/boot/vmlinux.bin
    GZIP    arch/arc/boot/vmlinux.bin.gz
    GZIP    arch/arc/boot/vmlinux.bin.gz
    UIMAGE  arch/arc/boot/uImage.gz
    UIMAGE  arch/arc/boot/uImage.gz
  Image Name:   Linux-5.10.0-rc4-00003-g62f23044
  Created:      Sun Nov 22 02:52:26 2020
  Image Type:   ARC Linux Kernel Image (gzip compressed)
  Data Size:    2109376 Bytes = 2059.94 KiB = 2.01 MiB
  Load Address: 80000000
  Entry Point:  80004000
    Image arch/arc/boot/uImage is ready
  Image Name:   Linux-5.10.0-rc4-00003-g62f23044
  Created:      Sun Nov 22 02:52:26 2020
  Image Type:   ARC Linux Kernel Image (gzip compressed)
  Data Size:    2815455 Bytes = 2749.47 KiB = 2.69 MiB
  Load Address: 80000000
  Entry Point:  80004000

This is a race between the two threads trying to write to the same file
arch/arc/boot/uImage.gz. This is a potential problem that can generate
a broken file.

I fixed a similar problem for ARM by commit 3939f33450 ("ARM: 8418/1:
add boot image dependencies to not generate invalid images").

I highly recommend to avoid such build rules that cause a race condition.

Move the uImage rule to arch/arc/Makefile.

Another strangeness is that arch/arc/boot/Makefile compares the
timestamps between $(obj)/uImage and $(obj)/uImage.*:

  $(obj)/uImage: $(obj)/uImage.$(suffix-y)
          @ln -sf $(notdir $<) $@
          @echo '  Image $@ is ready'

This does not work as expected since $(obj)/uImage is a symlink.
The symlink should be created in a phony target rule.

I used $(kecho) instead of echo to suppress the message
'Image arch/arc/boot/uImage is ready' when the -s option is given.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
This commit is contained in:
Masahiro Yamada 2020-11-22 04:36:55 +09:00 committed by Vineet Gupta
parent 0cfccb3c04
commit c5e6ae563c
2 changed files with 13 additions and 11 deletions
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13
arch/arc/Makefile
View File

@ -102,11 +102,22 @@ libs-y += arch/arc/lib/ $(LIBGCC)
boot := arch/arc/boot
boot_targets := uImage uImage.bin uImage.gz uImage.lzma
boot_targets := uImage.bin uImage.gz uImage.lzma
PHONY += $(boot_targets)
$(boot_targets): vmlinux
$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
uimage-default-y := uImage.bin
uimage-default-$(CONFIG_KERNEL_GZIP) := uImage.gz
uimage-default-$(CONFIG_KERNEL_LZMA) := uImage.lzma
PHONY += uImage
uImage: $(uimage-default-y)
@ln -sf $< $(boot)/uImage
@$(kecho) ' Image $(boot)/uImage is ready'
CLEAN_FILES += $(boot)/uImage
archclean:
$(Q)$(MAKE) $(clean)=$(boot)

11
arch/arc/boot/Makefile
View File

@ -1,5 +1,5 @@
# SPDX-License-Identifier: GPL-2.0
targets := vmlinux.bin vmlinux.bin.gz uImage
targets := vmlinux.bin vmlinux.bin.gz
# uImage build relies on mkimage being availble on your host for ARC target
# You will need to build u-boot for ARC, rename mkimage to arc-elf32-mkimage
@ -13,11 +13,6 @@ LINUX_START_TEXT = $$(readelf -h vmlinux | \
UIMAGE_LOADADDR = $(CONFIG_LINUX_LINK_BASE)
UIMAGE_ENTRYADDR = $(LINUX_START_TEXT)
suffix-y := bin
suffix-$(CONFIG_KERNEL_GZIP) := gz
suffix-$(CONFIG_KERNEL_LZMA) := lzma
targets += uImage
targets += uImage.bin
targets += uImage.gz
targets += uImage.lzma
@ -42,7 +37,3 @@ $(obj)/uImage.gz: $(obj)/vmlinux.bin.gz FORCE
$(obj)/uImage.lzma: $(obj)/vmlinux.bin.lzma FORCE
$(call if_changed,uimage,lzma)
$(obj)/uImage: $(obj)/uImage.$(suffix-y)
@ln -sf $(notdir $<) $@
@echo ' Image $@ is ready'