anydbm: use gdbm "u" flag for concurrent writers

This will fix bug #53607.

diff --git a/pym/portage/cache/anydbm.py b/pym/portage/cache/anydbm.py
index 1cf3775eba012e113b4a342db7783687769beab0..1d56b1458a9cae4523ae0ac020ed0b5a24dc5842 100644 (file)
--- a/pym/portage/cache/anydbm.py
+++ b/pym/portage/cache/anydbm.py
@@ -9,6 +9,20 @@ try:
 except ImportError:
        # python 3.x
        import dbm as anydbm_module
+
+try:
+       import dbm.gnu as gdbm
+except ImportError:
+       try:
+               import gdbm
+       except ImportError:
+               gdbm = None
+
+try:
+       from dbm import whichdb
+except ImportError:
+       from whichdb import whichdb
+
 try:
        import cPickle as pickle
 except ImportError:
@@ -35,11 +49,15 @@ class database(fs_template.FsBased):
 
                self._db_path = os.path.join(self.location, fs_template.gen_label(self.location, self.label)+default_db)
                self.__db = None
+               mode = "w"
+               if whichdb(self._db_path) in ("dbm.gnu", "gdbm"):
+                       # Allow multiple concurrent writers (see bug #53607).
+                       mode += "u"
                try:
                        # dbm.open() will not work with bytes in python-3.1:
                        #   TypeError: can't concat bytes to str
                        self.__db = anydbm_module.open(self._db_path,
-                               'w', self._perms)
+                               mode, self._perms)
                except anydbm_module.error:
                        # XXX handle this at some point
                        try:
@@ -53,14 +71,22 @@ class database(fs_template.FsBased):
                                if self.__db == None:
                                        # dbm.open() will not work with bytes in python-3.1:
                                        #   TypeError: can't concat bytes to str
-                                       self.__db = anydbm_module.open(self._db_path,
-                                               'c', self._perms)
+                                       if gdbm is None:
+                                               self.__db = anydbm_module.open(self._db_path,
+                                                       "c", self._perms)
+                                       else:
+                                               # Prefer gdbm type if available, since it allows
+                                               # multiple concurrent writers (see bug #53607).
+                                               self.__db = gdbm.open(self._db_path,
+                                                       "cu", self._perms)
                        except anydbm_module.error as e:
                                raise cache_errors.InitializationError(self.__class__, e)
                self._ensure_access(self._db_path)
 
        def iteritems(self):
-               return iter(self.__db.items())
+               # dbm doesn't implement items()
+               for k in self.__db.keys():
+                       yield (k, self[k])
 
        def _getitem(self, cpv):
                # we override getitem because it's just a cpickling of the data handed in.