bitbake: gitsm: Add need_update method to determine when we are going to a new SRCREV

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@google.com>.  The
included test case was also written by him, and included unmodified.

(Bitbake rev: 4ce92f43eeac6a4bfd06e8567fa6891614b5b3b0)

Signed-off-by: Mark Hatle <mark.hatle@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 20 insertions, 0 deletions

diff --git a/bitbake/lib/bb/fetch2/gitsm.py b/bitbake/lib/bb/fetch2/gitsm.py
index 54f99b1036..a07eb7e7ee 100644
--- a/bitbake/lib/bb/fetch2/gitsm.py
+++ b/bitbake/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