rt: fix threaded scheduler shutdown deadlock #2074
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Previously, if an IO event was received during the runtime shutdown process, it was possible to enter a deadlock. This was due to the scheduler shutdown logic not expecting tasks to get scheduled once the worker was in the shutdown process. This patch fixes the deadlock by checking the queues for new tasks after each call to park. If a new task is received, it is forcefully shutdown. Fixes #2061
carllerche
commented
Jan 8, 2020
| @@ -63,65 +63,6 @@ fn acquire_mutex_in_drop() { | |||
| drop(rt); | |||
| } | |||
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| #[test] | |||
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This test is moved into rt_common.rs so that it is run against both schedulers.
dfoxfranke
reviewed
Jan 8, 2020
| // First, drain all tasks from both the local & global queue. | ||
| while let Some(task) = self.owned().work_queue.pop_local_first() { | ||
| notify = true; | ||
| task.shutdown(); |
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Is it correct to be calling shutdown() both here and at line 534 above?
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Yes. The shutdown call above cannot do anything If the task is in a queue. Calling shutdown here candles those cases.
hawkw
reviewed
Jan 8, 2020
| task.shutdown(); | ||
| } | ||
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| if notify { |
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It could be good if there was a comment here explaining why we have to notify repeatedly?
hawkw
approved these changes
Jan 8, 2020
dfoxfranke
approved these changes
Jan 9, 2020
umanwizard
added a commit
to MaterializeInc/materialize
that referenced
this pull request
Jan 9, 2020
This reverts commit 7ce6cea. As it turns out, the flaky tests were due to a Tokio bug, which has been fixed in tokio-rs/tokio#2074 , which went out in v0.2.9.
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Previously, if an IO event was received during the runtime shutdown
process, it was possible to enter a deadlock. This was due to the
scheduler shutdown logic not expecting tasks to get scheduled once the
worker was in the shutdown process.
This patch fixes the deadlock by checking the queues for new tasks after
each call to park. If a new task is received, it is forcefully shutdown.
Fixes #2061