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4.x: Fix long sequence ObserveOn StackOverflowException upon Dispose #738

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Merged
danielcweber merged 1 commit into from
Jul 3, 2018
Merged

4.x: Fix long sequence ObserveOn StackOverflowException upon Dispose #738

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5 changes: 4 additions & 1 deletion Rx.NET/Source/src/System.Reactive/Internal/ScheduledObserver.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -536,7 +536,10 @@ private IDisposable DrainShortRunning(IScheduler recursiveScheduler)

if (Interlocked.Decrement(ref _wip) != 0)
{
return recursiveScheduler.Schedule(this, DRAIN_SHORT_RUNNING);
// Don't return the disposable of Schedule() because that may chain together
// a long string of ScheduledItems causing StackOverflowException upon Dispose()
var d = recursiveScheduler.Schedule(this, DRAIN_SHORT_RUNNING);
Disposable.TrySetMultiple(ref _task, d);
}
return Disposable.Empty;
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@danielcweber danielcweber Jul 3, 2018

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Shouldn't it at least return this here?

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@akarnokd akarnokd Jul 3, 2018

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That would recurse upon calling Dispose() for no practical purpose. The public void Dispose() takes care of the cleanup when the downstream disposes, including the outstanding tasks.

}
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13 changes: 13 additions & 0 deletions Rx.NET/Source/tests/Tests.System.Reactive/Tests/Linq/Observable/ObserveOnTest.cs
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Expand Up @@ -645,6 +645,19 @@ public void ObserveOn_SynchronizationContext_Simple()
);
}

[Fact]
public void ObserveOn_EventLoop_Long()
{
var _scheduler1 = new EventLoopScheduler();
var N = 1_000_000;

var cde = new CountdownEvent(1);

Observable.Range(1, N).ObserveOn(_scheduler1)
.Subscribe(v => { }, () => cde.Signal());

Assert.True(cde.Wait(5000), "Timeout!");
}
}

internal class MyCtx : SynchronizationContext
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