@@ -251,7 +251,16 @@ class TestParallelOps(iotests.QMPTestCase):
speed=1024)
self.assert_qmp(result, 'return', {})
- for job in pending_jobs:
+ # Do this in reverse: After unthrottling them, some jobs may finish
+ # before we have unthrottled all of them. This will drain their
+ # subgraph, and this will make jobs above them advance (despite those
+ # jobs on top being throttled). In the worst case, all jobs below the
+ # top one are finished before we can unthrottle it, and this makes it
+ # advance so far that it completes before we can unthrottle it - which
+ # results in an error.
+ # Starting from the top (i.e. in reverse) does not have this problem:
+ # When a job finishes, the ones below it are not advanced.
+ for job in reversed(pending_jobs):
result = self.vm.qmp('block-job-set-speed', device=job, speed=0)
self.assert_qmp(result, 'return', {})