[bitbake-devel] [PATCH 1/1] gitsm: Add need_update method to determine when we are going to a new SRCREV

[William Kennington]

I think this looks good in terms of fixing the issue. It might be
overly pessimistic in triggering need_update since it doesn't re-use
git metadata, so it isn't just looking at the tree for each download.

Out of curiosity, since git does its own locking, is there any harm in
not taking the download locks but reading the metadata of the bare git
repos? No downloader should ever be purging commits from the tree, so
needs_update would never return a false negative.

On Wed, Mar 27, 2019 at 10:41 AM Mark Hatle <mark.hatle at windriver.com> wrote:
>
> If the system had previously fetched a source repository for use by gitsm,
> and then the SRCREV was updated and the new commit already existed, the system
> would not re-evaluate the submodules and update them accordingly.
>
> The cause of this issue was that need_update was being used, unmodified, from
> the base git fetcher.  It did not have any knowledge, nor did it care if we
> were moving commits and needed to re-evaluate what was happening due to this
> switch.
>
> To fix the issue, during the download process we add all processed (by
> gitsm) srcrevs to the git config file, as bitbake.srcrev.  This allows us to
> use a new need_update function that not only checks if the git commit is
> present, but if we have previously processed this commit to ensure all of the
> submodule components are also present.
>
> This approach is used, instead of iterating over the submodules in need_update
> to avoid a potential race condition that has affected us in the past.  The
> need_update is called only with the parent locking.  Any time we need to dive
> into the submodules, we need to lock, and unlock them, at each stage.  This
> opens the possibility of errors in either the code, or unintended race
> conditions with rm_work.
>
> This issue was discovered by William A. Kennington III <wak at google.com>.  The
> included test case was also written by him, and included unmodified.
>
> Signed-off-by: Mark Hatle <mark.hatle at windriver.com>
> ---
>  lib/bb/fetch2/gitsm.py | 20 ++++++++++++++++++++
>  lib/bb/tests/fetch.py  | 19 +++++++++++++++++++
>  2 files changed, 39 insertions(+)
>
> diff --git a/lib/bb/fetch2/gitsm.py b/lib/bb/fetch2/gitsm.py
> index b21fed26..32389130 100644
> --- a/lib/bb/fetch2/gitsm.py
> +++ b/lib/bb/fetch2/gitsm.py
> @@ -147,6 +147,23 @@ class GitSM(Git):
>
>          return submodules != []
>
> +    def need_update(self, ud, d):
> +        if Git.need_update(self, ud, d):
> +            return True
> +
> +        try:
> +            # Check for the nugget dropped by the download operation
> +            known_srcrevs = runfetchcmd("%s config --get-all bitbake.srcrev" % \
> +                            (ud.basecmd), d, workdir=ud.clonedir)
> +
> +            if ud.revisions[ud.names[0]] not in known_srcrevs.split():
> +                return True
> +        except bb.fetch2.FetchError:
> +            # No srcrev nuggets, so this is new and needs to be updated
> +            return True
> +
> +        return False
> +
>      def download(self, ud, d):
>          def download_submodule(ud, url, module, modpath, d):
>              url += ";bareclone=1;nobranch=1"
> @@ -157,6 +174,9 @@ class GitSM(Git):
>              try:
>                  newfetch = Fetch([url], d, cache=False)
>                  newfetch.download()
> +                # Drop a nugget to add each of the srcrevs we've fetched (used by need_update)
> +                runfetchcmd("%s config --add bitbake.srcrev %s" % \
> +                            (ud.basecmd, ud.revisions[ud.names[0]]), d, workdir=ud.clonedir)
>              except Exception as e:
>                  logger.error('gitsm: submodule download failed: %s %s' % (type(e).__name__, str(e)))
>                  raise
> diff --git a/lib/bb/tests/fetch.py b/lib/bb/tests/fetch.py
> index 25732627..429998b3 100644
> --- a/lib/bb/tests/fetch.py
> +++ b/lib/bb/tests/fetch.py
> @@ -942,6 +942,25 @@ class FetcherNetworkTest(FetcherTest):
>          self.assertTrue(os.path.exists(os.path.join(repo_path, '.git/modules/extern/json/config')), msg='Missing submodule config "extern/json"')
>          self.assertTrue(os.path.exists(os.path.join(repo_path, '.git/modules/extern/sanitizers/config')), msg='Missing submodule config "extern/sanitizers"')
>
> +    def test_git_submodule_update_CLI11(self):
> +        """ Prevent regression on update detection not finding missing submodule, or modules without needed commits """
> +        url = "gitsm://github.com/CLIUtils/CLI11;protocol=git;rev=cf6a99fa69aaefe477cc52e3ef4a7d2d7fa40714"
> +        fetcher = bb.fetch.Fetch([url], self.d)
> +        fetcher.download()
> +
> +        # CLI11 that pulls in a newer nlohmann-json
> +        url = "gitsm://github.com/CLIUtils/CLI11;protocol=git;rev=49ac989a9527ee9bb496de9ded7b4872c2e0e5ca"
> +        fetcher = bb.fetch.Fetch([url], self.d)
> +        fetcher.download()
> +        # Previous cwd has been deleted
> +        os.chdir(os.path.dirname(self.unpackdir))
> +        fetcher.unpack(self.unpackdir)
> +
> +        repo_path = os.path.join(self.tempdir, 'unpacked', 'git')
> +        self.assertTrue(os.path.exists(os.path.join(repo_path, '.git/modules/extern/googletest/config')), msg='Missing submodule config "extern/googletest"')
> +        self.assertTrue(os.path.exists(os.path.join(repo_path, '.git/modules/extern/json/config')), msg='Missing submodule config "extern/json"')
> +        self.assertTrue(os.path.exists(os.path.join(repo_path, '.git/modules/extern/sanitizers/config')), msg='Missing submodule config "extern/sanitizers"')
> +
>      def test_git_submodule_aktualizr(self):
>          url = "gitsm://github.com/advancedtelematic/aktualizr;branch=master;protocol=git;rev=d00d1a04cc2366d1a5f143b84b9f507f8bd32c44"
>          fetcher = bb.fetch.Fetch([url], self.d)
> --
> 2.16.0.rc2
>