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Fix concurrency-related bugs in ActivateBestChain

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If multiple threads are invoking ActivateBestChain, it was possible to have
them working towards different tips, and we could arrive at a less work tip
than we should.  Fix this by introducing a ChainState lock which must
be held for the entire duration of ActivateBestChain to enforce
exclusion in ABC.

Github-Pull: #13023
Rebased-From: a3ae8e68739023e5dba9e5cb190e707ed4603316
This commit is contained in:
Jesse Cohen 2018-05-10 15:57:16 -04:00 committed by MarcoFalke
parent 0948153ea6
commit bb79aaf93a
1 changed files with 13 additions and 0 deletions
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13
src/validation.cpp
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@ -144,6 +144,12 @@ private:
*/
std::set<CBlockIndex*> g_failed_blocks;
/**
* the ChainState CriticalSection
* A lock that must be held when modifying this ChainState - held in ActivateBestChain()
*/
CCriticalSection m_cs_chainstate;
public:
CChain chainActive;
BlockMap mapBlockIndex;
@ -2451,6 +2457,7 @@ void CChainState::PruneBlockIndexCandidates() {
bool CChainState::ActivateBestChainStep(CValidationState& state, const CChainParams& chainparams, CBlockIndex* pindexMostWork, const std::shared_ptr<const CBlock>& pblock, bool& fInvalidFound, ConnectTrace& connectTrace)
{
AssertLockHeld(cs_main);
const CBlockIndex *pindexOldTip = chainActive.Tip();
const CBlockIndex *pindexFork = chainActive.FindFork(pindexMostWork);
@ -2562,6 +2569,12 @@ bool CChainState::ActivateBestChain(CValidationState &state, const CChainParams&
// sanely for performance or correctness!
AssertLockNotHeld(cs_main);
// ABC maintains a fair degree of expensive-to-calculate internal state
// because this function periodically releases cs_main so that it does not lock up other threads for too long
// during large connects - and to allow for e.g. the callback queue to drain
// we use m_cs_chainstate to enforce mutual exclusion so that only one caller may execute this function at a time
LOCK(m_cs_chainstate);
CBlockIndex *pindexMostWork = nullptr;
CBlockIndex *pindexNewTip = nullptr;
int nStopAtHeight = gArgs.GetArg("-stopatheight", DEFAULT_STOPATHEIGHT);