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Filename Latest commit message Latest commit date
Masahiro Yamada ca2fc0dc1c ARC: build: move symlink creation to arch/arc/Makefile to avoid race
[ Upstream commit c5e6ae563c802c4d828d42e134af64004db2e58c ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-01-19 18:26:14 +01:00
arch ARC: build: move symlink creation to arch/arc/Makefile to avoid race 2021-01-19 18:26:14 +01:00
block block: fix use-after-free in disk_part_iter_next 2021-01-17 14:05:38 +01:00
certs
crypto crypto: asym_tpm: correct zero out potential secrets 2021-01-12 20:16:17 +01:00
Documentation
drivers dm integrity: fix flush with external metadata device 2021-01-19 18:26:13 +01:00
fs cifs: fix interrupted close commands 2021-01-19 18:26:13 +01:00
include dm integrity: fix flush with external metadata device 2021-01-19 18:26:13 +01:00
init
ipc
kernel tracing/kprobes: Do the notrace functions check without kprobes on ftrace 2021-01-19 18:26:12 +01:00
lib lib/genalloc: fix the overflow when size is too big 2021-01-12 20:16:10 +01:00
LICENSES
mm mm/hugetlb: fix potential missing huge page size info 2021-01-19 18:26:12 +01:00
net net: drop bogus skb with CHECKSUM_PARTIAL and offset beyond end of trimmed packet 2021-01-17 14:05:38 +01:00
samples
scripts depmod: handle the case of /sbin/depmod without /sbin in PATH 2021-01-12 20:16:10 +01:00
security
sound ASoC: dapm: remove widget from dirty list on free 2021-01-19 18:26:11 +01:00
tools bpftool: Fix compilation failure for net.o with older glibc 2021-01-17 14:05:37 +01:00
usr
virt kvm: check tlbs_dirty directly 2021-01-12 20:16:22 +01:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS
Makefile kbuild: enforce -Werror=return-type 2021-01-19 18:26:11 +01:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.