v3.1.4: race condition in DeferredScalarSubscription about rxjava

[akarnokd]

Hi. Could you share more details on the race condition you are experiencing?

There is indeed a small race when a cancel happens while poll() is in progress, which can result in either a null or normal value. null will be treated by flatMap as being an empty source and bail out. Non null might be passed along and probably eventually stopped by some other operator's cancellation check.

[nolaviz]

The race condition is: - Thread 1 reaches DeferredScalarSubscription::complete() line 113, sees the state as FUSED_EMPTY, proceeds to line 114 - Thread 1 sets value to the supplied "v" - Thread 2 reaches DeferredScalarSubscription::cancel() line 185, sets the state to CANCELLED - Thread 2 sets value to null - Thread 1 sets the state to FUSED_READY The subscription is now in state FUSED_READY, but has a null value.

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On Mon, Oct 2, 2023 at 10:49 AM David Karnok ***@***.***> wrote: Hi. Could you share more details on the race condition you are experiencing? There is indeed a small race when a cancel happens while poll() is in progress, which can result in either a null or normal value. null will be treated by flatMap as being an empty source and bail out. Non null might be passed along and probably eventually stopped by some other operator's cancellation check. — Reply to this email directly, view it on GitHub <#7604 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAR6VA5VH72S4DMP7PMEDPDX5JWW3ANCNFSM6AAAAAA5O76UDQ> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[akarnokd]

I see. Should have no practical effect because the poll() can return null indicating emptiness.

Do you have code that misbehaves due to this race?

[nolaviz]

Our automated race-detection tooling is triggering on this. If this is a non-issue - I'll find a way to tell the automated tool to ignore it.

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On Mon, Oct 2, 2023 at 11:43 AM David Karnok ***@***.***> wrote: I see. Should have no practical effect because the poll() can return null indicating emptiness. Do you have code that misbehaves due to this race? — Reply to this email directly, view it on GitHub <#7604 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAR6VA6D4BHKA4YIMOMMTEDX5J5BRANCNFSM6AAAAAA5O76UDQ> . You are receiving this because you authored the thread.Message ID: ***@***.***>