_scheduler: don't pass whole queue to child jobaevri/smallerjobs2

Stop passing the scheduler's job queue's across to child jobs, via the
'action_cb' parameter. Instead pass a module-level function, which will
pickle nicely.

This isn't much of a problem while we are in the 'fork' multiprocessing
model. As we move towards supporting the 'spawn' model for win32, then
we need to consider what we will be pickling and unpickling, to cross
the process boundary.

1 files changed, 7 insertions, 4 deletions

diff --git a/src/buildstream/_scheduler/queues/sourcepushqueue.py b/src/buildstream/_scheduler/queues/sourcepushqueue.py
index c38460e6a..f0926654c 100644
--- a/src/buildstream/_scheduler/queues/sourcepushqueue.py
+++ b/src/buildstream/_scheduler/queues/sourcepushqueue.py
@@ -30,13 +30,16 @@ class SourcePushQueue(Queue):
     complete_name = "Sources pushed"
     resources = [ResourceType.UPLOAD]
 
-    def process(self, element):
-        # Returns whether a source was pushed or not
-        if not element._source_push():
-            raise SkipJob(self.action_name)
+    def get_process_func(self):
+        return SourcePushQueue._raise_skip_if_not_pushed
 
     def status(self, element):
         if element._skip_source_push():
             return QueueStatus.SKIP
 
         return QueueStatus.READY
+
+    @staticmethod
+    def _raise_skip_if_not_pushed(element):
+        if not element._source_push():
+            raise SkipJob(SourcePushQueue.action_name)