Removed race condition from global_queue_depth_multi_thread test #6936
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jofas
commented
Oct 25, 2024
| @@ -93,7 +93,7 @@ fn try_block_threaded(rt: &Runtime) -> Result<Vec<mpsc::Sender<()>>, mpsc::RecvT | |||
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| // Spawn a task per runtime worker to block it. | |||
| rt.spawn(async move { | |||
| tx.send(()).unwrap(); | |||
| tx.send(()).ok(); | |||
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I made this fail silently because I triggered a panic here when I ^Ced a test run, which I found needlessly confusing.
mox692
approved these changes
Oct 27, 2024
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Thanks for the heads up, didn't see that the CI failure was fixed. |
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@Darksonn and @mox692 discovered a race condition in the retry logic introduced in #6916 that this PR aims to fix.
In the
global_queue_depth_multi_threadtest, we try to block the two worker threads before spawning more tasks onto the global queue. This allows us to measure theRuntimeMetrics::global_queue_depthdeterministically, as the two worker threads are blocked and therefore unable to pull any tasks from the global queue. Blocking the two worker threads might fail, in which case one of the tasks from the previous try to block the runtime would remain in the global queue. If the task remains in the global queue after the second try to block the runtime succeeds, it would add an unexpected task to theglobal_queue_depth, making the test fail.The solution this PR provides is to just create a new runtime on each try to block it. So if the first try to block the runtime fails, we drop the runtime and create a new one (with an empty global queue) that we then try to block again. We proceed until we succeed in blocking one runtime or run out of tries.