validation: avoid potential deadlocks in ValidationInterface #15205
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See discussions here: - bitcoin#11722 (review) - bitcoin#13168 (comment)
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Restarted appveyor, unrelated error. |
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Pushed an update futureproofing all calls to |
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Since ActivateBestChain will in certain cases block in order to allow the ValidationInterface queue to drain, it cannot safely be called from within ValidationInterface callbacks. This patch adds assertions preventing that when DEBUG_LOCKORDER. We slightly rework the ValidationInterface class, adding an `AddToProcessQueue()` method that handles scheduling a callback. When the scheduling queue is initiated, we make the thread aware it's managed by ValidationInterface.
Also adds default constructor and destructor to CMainSignals to avoid build errors due to the forward declaration of MainSignalsInstance.
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I've taken @practicalswift's advice on declaration conditional on |
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We discussed a better approach today on IRC (http://www.erisian.com.au/bitcoin-core-dev/log-2019-01-22.html), which is to conditionally move all |
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Currently, the potential for a deadlock exists if
ActivateBestChain()is called from within theValidationInterfacescheduler thread. This is because ABC itself avoids overrunning the VI queue by waiting for it to drain once it has passed a certain depth.To avoid this (or at least disallow it during CI runs), this change introduces thread_local state that gets set to indicate execution on ValidationInterface threads. If we've compiled with
DEBUG_LOCKORDER, calling ABC from within a VI thread throws an exception. A small,necessaryrefactoring onCMainSignalsis included.This changeset also includes a commit from #13168 that limits the platforms where we can rely on the use of thread_local.