Sink.Dispose should only call Dispose(true) once. #771
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danielcweber
commented
Jul 6, 2018
| @@ -25,12 +26,16 @@ protected Sink(IObserver<TTarget> observer) | |||
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| public void Dispose() | |||
| { | |||
| Dispose(true); | |||
| if (_observer != NopObserver<TTarget>.Instance && Interlocked.Exchange(ref _observer, NopObserver<TTarget>.Instance) != NopObserver<TTarget>.Instance) | |||
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@akarnokd Check first and then exchange is the more efficient way to go I guess?
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It has slightly more overhead when the method is called only once (mainly due to targeting the same address and causing a data dependency). Its benefits show when 3+ calls are typical. In our case, we'd expect typically 1 call, sometimes two so the Interlocked.Exchange should suffice and should be practically equivalent to the original volatile field store (they both are usually implemented as LOCK XCHG or MOV + LOCK XADD stack[0], 0).
… expected calls (< 3), the benefit will not show.
akarnokd
approved these changes
Jul 6, 2018
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This is part of a a two part fix for #768. Dispose.Create has been inlined in 6ecc899, which, for RefCount, will lead to garbage if Sink.Dispose is called multiple times. This PR makes Sink.Dispose a nop from the second call on.
Note: This is not enough to fix #768, although the expectation of the OP about the behaviour is incorrect, there is another bug that will be fixed in a following PR.