From 25bc9615b7480e4ba2c482a6f0e7e3b33f50e6e0 Mon Sep 17 00:00:00 2001 From: Matt Corallo <git@bluematt.me> Date: Fri, 11 May 2018 16:56:19 -0400 Subject: [PATCH] Document validationinterace callback blocking deadlock potential. --- src/validation.cpp | 3 +++ src/validation.h | 19 +++++++++++++++---- 2 files changed, 18 insertions(+), 4 deletions(-) diff --git a/src/validation.cpp b/src/validation.cpp index 9791d6e2d..1a81cd17b 100644 --- a/src/validation.cpp +++ b/src/validation.cpp @@ -2704,6 +2704,9 @@ bool CChainState::ActivateBestChain(CValidationState &state, const CChainParams& // Block until the validation queue drains. This should largely // never happen in normal operation, however may happen during // reindex, causing memory blowup if we run too far ahead. + // Note that if a validationinterface callback ends up calling + // ActivateBestChain this may lead to a deadlock! We should + // probably have a DEBUG_LOCKORDER test for this in the future. SyncWithValidationInterfaceQueue(); } diff --git a/src/validation.h b/src/validation.h index b5ab10786..284ef75c3 100644 --- a/src/validation.h +++ b/src/validation.h @@ -233,7 +233,8 @@ static const uint64_t MIN_DISK_SPACE_FOR_BLOCK_FILES = 550 * 1024 * 1024; * Note that we guarantee that either the proof-of-work is valid on pblock, or * (and possibly also) BlockChecked will have been called. * - * Call without cs_main held. + * May not be called with cs_main held. May not be called in a + * validationinterface callback. * * @param[in] pblock The block we want to process. * @param[in] fForceProcessing Process this block even if unrequested; used for non-network block sources and whitelisted peers. @@ -245,7 +246,8 @@ bool ProcessNewBlock(const CChainParams& chainparams, const std::shared_ptr<cons /** * Process incoming block headers. * - * Call without cs_main held. + * May not be called with cs_main held. May not be called in a + * validationinterface callback. * * @param[in] block The block headers themselves * @param[out] state This may be set to an Error state if any error occurred processing them @@ -278,7 +280,12 @@ void ThreadScriptCheck(); bool IsInitialBlockDownload(); /** Retrieve a transaction (from memory pool, or from disk, if possible) */ bool GetTransaction(const uint256& hash, CTransactionRef& tx, const Consensus::Params& params, uint256& hashBlock, bool fAllowSlow = false, CBlockIndex* blockIndex = nullptr); -/** Find the best known block, and make it the tip of the block chain */ +/** + * Find the best known block, and make it the tip of the block chain + * + * May not be called with cs_main held. May not be called in a + * validationinterface callback. + */ bool ActivateBestChain(CValidationState& state, const CChainParams& chainparams, std::shared_ptr<const CBlock> pblock = std::shared_ptr<const CBlock>()); CAmount GetBlockSubsidy(int nHeight, const Consensus::Params& consensusParams); @@ -445,7 +452,11 @@ inline CBlockIndex* LookupBlockIndex(const uint256& hash) /** Find the last common block between the parameter chain and a locator. */ CBlockIndex* FindForkInGlobalIndex(const CChain& chain, const CBlockLocator& locator); -/** Mark a block as precious and reorganize. */ +/** Mark a block as precious and reorganize. + * + * May not be called with cs_main held. May not be called in a + * validationinterface callback. + */ bool PreciousBlock(CValidationState& state, const CChainParams& params, CBlockIndex *pindex); /** Mark a block as invalid. */