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John Garry d4ff926592 perf tools: Stop depending on .git files for building PERF-VERSION-FILE 
This essentially reverts commit c72e3f04b4 ("tools/perf/build:
Speed up git-version test on re-make") and commit 4e666cdb06
("perf tools: Fix dependency for version file creation")

In commit c72e3f04b4 ("tools/perf/build: Speed up git-version test
on re-make"), a makefile dependency on .git/HEAD was added. The
background is that running PERF-VERSION-FILE is relatively slow, and
commands like "git describe" are particularly slow.

In commit 4e666cdb06 ("perf tools: Fix dependency for version file
creation"), an additional dependency on .git/ORIG_HEAD was added, as
.git/HEAD may not change for "git reset --hard HEAD^" command. However,
depending on whether we're on a branch or not, a "git cherry-pick" may
not lead to the version being updated.

As discussed with the git community in [0], using git internal files for
dependencies is not reliable. Commit 4e666cdb06 also breaks some build
scenarios [1].

As mentioned, c72e3f04b4 ("tools/perf/build: Speed up git-version
test on re-make") was added to speed up the build. However in commit
7572733b84 ("perf tools: Fix version kernel tag") we removed the
call to "git describe", so just revert Makefile.perf back to same as pre
c72e3f04b4 ("tools/perf/build: Speed up git-version test on
re-make") and the build should not be so slow, as below:

Pre 7572733b84:

  $> time util/PERF-VERSION-GEN
    PERF_VERSION = 5.17.rc8.g4e666cdb06ee

  real    0m0.110s
  user    0m0.091s
  sys     0m0.019s

Post 7572733b84:

  $> time util/PERF-VERSION-GEN
    PERF_VERSION = 5.17.rc8.g7572733b8499

  real    0m0.039s
  user    0m0.036s
  sys     0m0.007s

[0] https://lore.kernel.org/git/87wngkpddp.fsf@igel.home/T/#m4a4dd6de52fdbe21179306cd57b3761eb07f45f8
[1] https://lore.kernel.org/linux-perf-users/20220329093120.4173283-1-matthieu.baerts@tessares.net/T/#u

Committer testing:

After a fresh rebuild using 'make -C tools/perf O=/tmp/build/perf install-bin':

  $ perf -v
  perf version 5.17.g162f9db407b6
  $ git log --oneline -1
  162f9db407b6a6e5 (HEAD -> perf/core) perf tools: Stop depending on .git files for building PERF-VERSION-FILE
  $

Now using a detached tarball, i.e. outside the kernel source tree:

  $ ls -la perf*tar
  ls: cannot access 'perf*tar': No such file or directory
  $ make perf-tar-src-pkg
    TAR
    PERF_VERSION = 5.17.g31d10b3ef133
  $ ls -la perf*tar
  -rw-r--r--. 1 acme acme 22241280 Mar 30 13:26 perf-5.17.0.tar
  $ mv perf-5.17.0.tar /tmp
  $ cd /tmp
  $ tar xf perf-5.17.0.tar
  $ cd perf-5.17.0/
  $ make -C tools/perf |& tail
    CC      util/pmu.o
    CC      util/pmu-flex.o
    CC      util/expr-flex.o
    CC      util/expr.o
    LD      util/scripting-engines/perf-in.o
    LD      util/intel-pt-decoder/perf-in.o
    LD      util/perf-in.o
    LD      perf-in.o
    LINK    perf
  make: Leaving directory '/tmp/perf-5.17.0/tools/perf'
  $ tools/perf/perf -v
  perf version 5.17.g31d10b3ef133
  $ pwd
  /tmp/perf-5.17.0
  $ cat PERF-VERSION-FILE
  #define PERF_VERSION "5.17.g31d10b3ef133"
  $

Fixes: 4e666cdb06 ("perf tools: Fix dependency for version file creation")
Reported-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: John Garry <john.garry@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.garry@huawei.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/1648635774-14581-1-git-send-email-john.garry@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2022-04-01 16:19:35 -03:00
arch This pull request contains the following changes for UML: 2022-03-31 16:16:58 -07:00
block ptrace: Cleanups for v5.18 2022-03-28 17:29:53 -07:00
certs Kbuild updates for v5.18 2022-03-31 11:59:03 -07:00
crypto for-5.18/64bit-pi-2022-03-25 2022-03-26 12:01:35 -07:00
Documentation Merge branch 'akpm' (patches from Andrew) 2022-04-01 12:08:34 -07:00
drivers gpio fixes for v5.18-rc1 2022-04-01 10:26:09 -07:00
fs nilfs2: get rid of nilfs_mapping_init() 2022-04-01 11:46:09 -07:00
include Merge branch 'akpm' (patches from Andrew) 2022-04-01 12:08:34 -07:00
init Kbuild updates for v5.18 2022-03-31 11:59:03 -07:00
ipc fs: allocate inode by using alloc_inode_sb() 2022-03-22 15:57:03 -07:00
kernel Networking fixes for 5.18-rc1 and rethook patches. 2022-03-31 11:23:31 -07:00
lib This pull request contains the following changes for UML: 2022-03-31 16:16:58 -07:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm mm/damon: prevent activated scheme from sleeping by deactivated schemes 2022-04-01 11:46:09 -07:00
net Networking fixes for 5.18-rc1 and rethook patches. 2022-03-31 11:23:31 -07:00
samples dma-mapping updates for Linux 5.18 2022-03-29 08:50:14 -07:00
scripts Some late-arriving documentation improvements. This is mostly build-system 2022-03-31 12:10:42 -07:00
security hardening updates for v5.18-rc1-fix1 2022-03-31 11:43:01 -07:00
sound sound fixes for 5.18-rc1 2022-04-01 10:32:46 -07:00
tools perf tools: Stop depending on .git files for building PERF-VERSION-FILE 2022-04-01 16:19:35 -03:00
usr Kbuild updates for v5.18 2022-03-31 11:59:03 -07:00
virt KVM: compat: riscv: Prevent KVM_COMPAT from being selected 2022-03-11 19:02:15 +05:30
.clang-format genirq/msi: Make interrupt allocation less convoluted 2021-12-16 22:22:20 +01:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: update Kirill's email 2022-04-01 11:46:09 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: replace a Microchip AT91 maintainer 2022-02-09 11:30:01 +01:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input 2022-04-01 10:14:32 -07:00
Makefile Kbuild updates for v5.18 2022-03-31 11:59:03 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.