Backed out changeset 4e9cd1d537cc (bug 1384062) for flake8 failures

MozReview-Commit-ID: C2AVg8g3xpV

testing/mozbase/mozsystemmonitor/mozsystemmonitor/resourcemonitor.py

@@ -289,10 +289,7 @@ class SystemResourceMonitor(object):
         assert self._running
         assert not self._stopped
 
-        try:
-            self._pipe.send(('terminate',))
-        except Exception:
-            pass
+        self._pipe.send(('terminate',))
         self._running = False
         self._stopped = True
 
@@ -304,28 +301,9 @@ class SystemResourceMonitor(object):
         # as a separate data structure. When it has finished sending
         # samples, it sends a special "done" message to indicate it
         # is finished.
-
-        # multiprocessing.Pipe is not actually a pipe on at least Linux.  that
-        # has an effect on the expected outcome of reading from it when the
-        # other end of the pipe dies, leading to possibly hanging on revc()
-        # below. So we must poll().
-        def poll():
-            try:
-                return self._pipe.poll(0.1)
-            except Exception as e:
-                # Poll might throw an exception even though there's still
-                # data to read. That happens when the underlying system call
-                # returns both POLLERR and POLLIN, but python doesn't tell us
-                # about it. So assume there is something to read, and we'll
-                # get an exception when trying to read the data.
-                return True
-        while poll():
-            try:
-                start_time, end_time, io_diff, cpu_diff, cpu_percent, virt_mem, \
-                    swap_mem = self._pipe.recv()
-            except Exception as e:
-                # Let's assume we're done here
-                start_time = 'done'
+        while self._pipe.poll(1.0):
+            start_time, end_time, io_diff, cpu_diff, cpu_percent, virt_mem, \
+                swap_mem = self._pipe.recv()
 
             # There should be nothing after the "done" message so
             # terminate.
@@ -347,6 +325,11 @@ class SystemResourceMonitor(object):
         if self._process.is_alive():
             self._process.terminate()
             self._process.join(10)
+        else:
+            # We should have received a "done" message from the
+            # child indicating it shut down properly. This only
+            # happens if the child shuts down cleanly.
+            assert done
 
         if len(self.measurements):
             self.start_time = self.measurements[0].start