Fix race condition in connection termination#772
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seanmonstar merged 1 commit intohyperium:masterfrom May 2, 2024
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See hyperium/hyper#3652. What I have found is the final reference to a stream being dropped after the `maybe_close_connection_if_no_streams` but before the `inner.poll()` completes can lead to the connection dangling forever without any forward progress. No streams/references are alive, but the connection is not complete and never wakes up again. This seems like a classic TOCTOU race condition. In this fix, I check again at the end of poll and if this state is detected, wake up the task again. Wth the test in hyperium/hyper#3655, on my machine, it fails about 5% of the time: ``` 1876 runs so far, 100 failures (94.94% pass rate). 95.197349ms avg, 1.097347435s max, 5.398457ms min ``` With that PR, this test is 100% reliable ``` 64010 runs so far, 0 failures (100.00% pass rate). 44.484057ms avg, 121.454709ms max, 1.872657ms min ``` Note: we also have reproduced this using `h2` directly outside of `hyper`, which is what gives me confidence this issue lies in `h2` and not `hyper`.
This was referenced May 1, 2024
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Pulls in hyperium/h2#772. We might want to wait on this, not sure how fast it will go
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Pulls in hyperium/h2#772. We might want to wait on this, not sure how fast it will go
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Pulls in hyperium/h2#772. We might want to wait on this, not sure how fast it will go
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Excellent detective work, thanks!
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Pulls in hyperium/h2#772. We might want to wait on this, not sure how fast it will go Co-authored-by: John Howard <john.howard@solo.io>
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See hyperium/hyper#3652.
What I have found is the final reference to a stream being dropped after the
maybe_close_connection_if_no_streamsbut before theinner.poll()completes can lead to the connection dangling forever without any forward progress. No streams/references are alive, but the connection is not complete and never wakes up again. This seems like a classic TOCTOU race condition.In this fix, I check again at the end of poll and if this state is detected, wake up the task again.
Wth the test in hyperium/hyper#3655, on my machine, it fails about 5% of the time:
With that PR, this test is 100% reliable
Note: we also have reproduced this using
h2directly outside ofhyper, which is what gives me confidence this issue lies inh2and nothyper.