diff --git a/poky/bitbake/lib/bb/fetch2/clearcase.py b/poky/bitbake/lib/bb/fetch2/clearcase.py
index 3dd93ad..e2934ef 100644
--- a/poky/bitbake/lib/bb/fetch2/clearcase.py
+++ b/poky/bitbake/lib/bb/fetch2/clearcase.py
@@ -145,18 +145,18 @@
 
         basecmd = "%s %s" % (ud.basecmd, command)
 
-        if command is 'mkview':
+        if command == 'mkview':
             if not "rcleartool" in ud.basecmd:
                 # Cleartool needs a -snapshot view
                 options.append("-snapshot")
             options.append("-tag %s" % ud.viewname)
             options.append(ud.viewdir)
 
-        elif command is 'rmview':
+        elif command == 'rmview':
             options.append("-force")
             options.append("%s" % ud.viewdir)
 
-        elif command is 'setcs':
+        elif command == 'setcs':
             options.append("-overwrite")
             options.append(ud.configspecfile)
 
diff --git a/poky/bitbake/lib/bb/runqueue.py b/poky/bitbake/lib/bb/runqueue.py
index 8622738..26492e7 100644
--- a/poky/bitbake/lib/bb/runqueue.py
+++ b/poky/bitbake/lib/bb/runqueue.py
@@ -2303,16 +2303,22 @@
         for tid in changed:
             if tid not in self.rqdata.runq_setscene_tids:
                 continue
-            if tid in self.runq_running:
-                continue
-            if tid in self.scenequeue_covered:
-                # Potentially risky, should we report this hash as a match?
-                logger.info("Already covered setscene for %s so ignoring rehash" % (tid))
-                continue
             if tid not in self.pending_migrations:
                 self.pending_migrations.add(tid)
 
         for tid in self.pending_migrations.copy():
+            if tid in self.runq_running:
+                # Too late, task already running, not much we can do now
+                self.pending_migrations.remove(tid)
+                continue
+
+            if tid in self.scenequeue_covered or tid in self.sq_live:
+                # Already ran this setscene task or it running
+                # Potentially risky, should we report this hash as a match?
+                logger.info("Already covered setscene for %s so ignoring rehash" % (tid))
+                self.pending_migrations.remove(tid)
+                continue
+
             valid = True
             # Check no tasks this covers are running
             for dep in self.sqdata.sq_covered_tasks[tid]:
diff --git a/poky/bitbake/lib/bb/tests/utils.py b/poky/bitbake/lib/bb/tests/utils.py
index f4adf1d..5c910b4 100644
--- a/poky/bitbake/lib/bb/tests/utils.py
+++ b/poky/bitbake/lib/bb/tests/utils.py
@@ -103,6 +103,32 @@
             result = bb.utils._check_unsafe_delete_path(arg1)
             self.assertEqual(result, correctresult, '_check_unsafe_delete_path("%s") != %s' % (arg1, correctresult))
 
+class Checksum(unittest.TestCase):
+    filler = b"Shiver me timbers square-rigged spike Gold Road galleon bilge water boatswain wherry jack pirate. Mizzenmast rum lad Privateer jack salmagundi hang the jib piracy Pieces of Eight Corsair. Parrel marooned black spot yawl provost quarterdeck cable no prey, no pay spirits lateen sail."
+
+    def test_md5(self):
+        import hashlib
+        with tempfile.NamedTemporaryFile() as f:
+            f.write(self.filler)
+            f.flush()
+            checksum = bb.utils.md5_file(f.name)
+            self.assertEqual(checksum, "bd572cd5de30a785f4efcb6eaf5089e3")
+
+    def test_sha1(self):
+        import hashlib
+        with tempfile.NamedTemporaryFile() as f:
+            f.write(self.filler)
+            f.flush()
+            checksum = bb.utils.sha1_file(f.name)
+            self.assertEqual(checksum, "249eb8fd654732ea836d5e702d7aa567898eca71")
+
+    def test_sha256(self):
+        import hashlib
+        with tempfile.NamedTemporaryFile() as f:
+            f.write(self.filler)
+            f.flush()
+            checksum = bb.utils.sha256_file(f.name)
+            self.assertEqual(checksum, "fcfbae8bf6b721dbb9d2dc6a9334a58f2031a9a9b302999243f99da4d7f12d0f")
 
 class EditMetadataFile(unittest.TestCase):
     _origfile = """
diff --git a/poky/bitbake/lib/bb/utils.py b/poky/bitbake/lib/bb/utils.py
index d035949..8d40bcd 100644
--- a/poky/bitbake/lib/bb/utils.py
+++ b/poky/bitbake/lib/bb/utils.py
@@ -520,22 +520,26 @@
     fcntl.flock(lf.fileno(), fcntl.LOCK_UN)
     lf.close()
 
+def _hasher(method, filename):
+    import mmap
+
+    with open(filename, "rb") as f:
+        try:
+            with mmap.mmap(f.fileno(), 0, access=mmap.ACCESS_READ) as mm:
+                for chunk in iter(lambda: mm.read(8192), b''):
+                    method.update(chunk)
+        except ValueError:
+            # You can't mmap() an empty file so silence this exception
+            pass
+    return method.hexdigest()
+
+
 def md5_file(filename):
     """
     Return the hex string representation of the MD5 checksum of filename.
     """
-    import hashlib, mmap
-
-    with open(filename, "rb") as f:
-        m = hashlib.md5()
-        try:
-            with mmap.mmap(f.fileno(), 0, access=mmap.ACCESS_READ) as mm:
-                for chunk in iter(lambda: mm.read(8192), b''):
-                    m.update(chunk)
-        except ValueError:
-            # You can't mmap() an empty file so silence this exception
-            pass
-    return m.hexdigest()
+    import hashlib
+    return _hasher(hashlib.md5(), filename)
 
 def sha256_file(filename):
     """
@@ -543,24 +547,14 @@
     filename.
     """
     import hashlib
-
-    s = hashlib.sha256()
-    with open(filename, "rb") as f:
-        for line in f:
-            s.update(line)
-    return s.hexdigest()
+    return _hasher(hashlib.sha256(), filename)
 
 def sha1_file(filename):
     """
     Return the hex string representation of the SHA1 checksum of the filename
     """
     import hashlib
-
-    s = hashlib.sha1()
-    with open(filename, "rb") as f:
-        for line in f:
-            s.update(line)
-    return s.hexdigest()
+    return _hasher(hashlib.sha1(), filename)
 
 def preserved_envvars_exported():
     """Variables which are taken from the environment and placed in and exported