Be careful with system pkgs + parallel-install.

This should prevent FEATURES=parallel-install from interfering with
the fixes from bug #256616 and bug #259954.

diff --git a/pym/_emerge/Scheduler.py b/pym/_emerge/Scheduler.py
index 6c21c711eaea369674289c22078c02b1f1604292..fbf2d2dc0de9f7ce779f65bb219d583c4ff82e82 100644 (file)
--- a/pym/_emerge/Scheduler.py
+++ b/pym/_emerge/Scheduler.py
@@ -3,6 +3,7 @@
 
 from __future__ import print_function
 
+from collections import deque
 import gc
 import gzip
 import logging
@@ -176,8 +177,9 @@ class Scheduler(PollScheduler):
 
                # Holds merges that will wait to be executed when no builds are
                # executing. This is useful for system packages since dependencies
-               # on system packages are frequently unspecified.
-               self._merge_wait_queue = []
+               # on system packages are frequently unspecified. For example, see
+               # bug #256616.
+               self._merge_wait_queue = deque()
                # Holds merges that have been transfered from the merge_wait_queue to
                # the actual merge queue. They are removed from this list upon
                # completion. Other packages can start building only when this list is
@@ -1644,14 +1646,19 @@ class Scheduler(PollScheduler):
 
                while True:
 
-                       # When the number of jobs drops to zero, process all waiting merges.
-                       if not self._jobs and self._merge_wait_queue:
-                               for task in self._merge_wait_queue:
-                                       task.addExitListener(self._merge_wait_exit_handler)
-                                       self._task_queues.merge.add(task)
+                       # When the number of jobs and merges drops to zero,
+                       # process a single merge from _merge_wait_queue if
+                       # it's not empty. We only process one since these are
+                       # special packages and we want to ensure that
+                       # parallel-install does not cause more than one of
+                       # them to install at the same time.
+                       if (self._merge_wait_queue and not self._jobs and
+                               not self._task_queues.merge):
+                               task = self._merge_wait_queue.popleft()
+                               task.addExitListener(self._merge_wait_exit_handler)
+                               self._task_queues.merge.add(task)
                                self._status_display.merges = len(self._task_queues.merge)
-                               self._merge_wait_scheduled.extend(self._merge_wait_queue)
-                               del self._merge_wait_queue[:]
+                               self._merge_wait_scheduled.append(task)
 
                        self._schedule_tasks_imp()
                        self._status_display.display()
@@ -1670,7 +1677,8 @@ class Scheduler(PollScheduler):
                                state_change += 1
 
                        if not (state_change or \
-                               (not self._jobs and self._merge_wait_queue)):
+                               (self._merge_wait_queue and not self._jobs and
+                               not self._task_queues.merge)):
                                break
 
                return self._keep_scheduling()