diff options
Diffstat (limited to 'src/txmempool.h')
| -rw-r--r-- | src/txmempool.h | 53 |
1 files changed, 45 insertions, 8 deletions
diff --git a/src/txmempool.h b/src/txmempool.h index fadb554723..a8a0f7fa45 100644 --- a/src/txmempool.h +++ b/src/txmempool.h @@ -184,7 +184,7 @@ private: const LockPoints& lp; }; -// extracts a transaction hash from CTxMempoolEntry or CTransactionRef +// extracts a transaction hash from CTxMemPoolEntry or CTransactionRef struct mempoolentry_txid { typedef uint256 result_type; @@ -485,7 +485,43 @@ public: > > indexed_transaction_set; - mutable CCriticalSection cs; + /** + * This mutex needs to be locked when accessing `mapTx` or other members + * that are guarded by it. + * + * @par Consistency guarantees + * + * By design, it is guaranteed that: + * + * 1. Locking both `cs_main` and `mempool.cs` will give a view of mempool + * that is consistent with current chain tip (`chainActive` and + * `pcoinsTip`) and is fully populated. Fully populated means that if the + * current active chain is missing transactions that were present in a + * previously active chain, all the missing transactions will have been + * re-added to the mempool and should be present if they meet size and + * consistency constraints. + * + * 2. Locking `mempool.cs` without `cs_main` will give a view of a mempool + * consistent with some chain that was active since `cs_main` was last + * locked, and that is fully populated as described above. It is ok for + * code that only needs to query or remove transactions from the mempool + * to lock just `mempool.cs` without `cs_main`. + * + * To provide these guarantees, it is necessary to lock both `cs_main` and + * `mempool.cs` whenever adding transactions to the mempool and whenever + * changing the chain tip. It's necessary to keep both mutexes locked until + * the mempool is consistent with the new chain tip and fully populated. + * + * @par Consistency bug + * + * The second guarantee above is not currently enforced, but + * https://github.com/bitcoin/bitcoin/pull/14193 will fix it. No known code + * in bitcoin currently depends on second guarantee, but it is important to + * fix for third party code that needs be able to frequently poll the + * mempool without locking `cs_main` and without encountering missing + * transactions during reorgs. + */ + mutable RecursiveMutex cs; indexed_transaction_set mapTx GUARDED_BY(cs); using txiter = indexed_transaction_set::nth_index<0>::type::const_iterator; @@ -541,8 +577,8 @@ public: // Note that addUnchecked is ONLY called from ATMP outside of tests // and any other callers may break wallet's in-mempool tracking (due to // lack of CValidationInterface::TransactionAddedToMempool callbacks). - void addUnchecked(const CTxMemPoolEntry& entry, bool validFeeEstimate = true) EXCLUSIVE_LOCKS_REQUIRED(cs); - void addUnchecked(const CTxMemPoolEntry& entry, setEntries& setAncestors, bool validFeeEstimate = true) EXCLUSIVE_LOCKS_REQUIRED(cs); + void addUnchecked(const CTxMemPoolEntry& entry, bool validFeeEstimate = true) EXCLUSIVE_LOCKS_REQUIRED(cs, cs_main); + void addUnchecked(const CTxMemPoolEntry& entry, setEntries& setAncestors, bool validFeeEstimate = true) EXCLUSIVE_LOCKS_REQUIRED(cs, cs_main); void removeRecursive(const CTransaction &tx, MemPoolRemovalReason reason = MemPoolRemovalReason::UNKNOWN); void removeForReorg(const CCoinsViewCache *pcoins, unsigned int nMemPoolHeight, int flags) EXCLUSIVE_LOCKS_REQUIRED(cs_main); @@ -552,7 +588,7 @@ public: void clear(); void _clear() EXCLUSIVE_LOCKS_REQUIRED(cs); //lock free bool CompareDepthAndScore(const uint256& hasha, const uint256& hashb); - void queryHashes(std::vector<uint256>& vtxid); + void queryHashes(std::vector<uint256>& vtxid) const; bool isSpent(const COutPoint& outpoint) const; unsigned int GetTransactionsUpdated() const; void AddTransactionsUpdated(unsigned int n); @@ -594,7 +630,7 @@ public: * for). Note: vHashesToUpdate should be the set of transactions from the * disconnected block that have been accepted back into the mempool. */ - void UpdateTransactionsFromBlock(const std::vector<uint256> &vHashesToUpdate); + void UpdateTransactionsFromBlock(const std::vector<uint256>& vHashesToUpdate) EXCLUSIVE_LOCKS_REQUIRED(cs_main); /** Try to calculate all in-mempool ancestors of entry. * (these are all calculated including the tx itself) @@ -636,7 +672,7 @@ public: */ void GetTransactionAncestry(const uint256& txid, size_t& ancestors, size_t& descendants) const; - unsigned long size() + unsigned long size() const { LOCK(cs); return mapTx.size(); @@ -710,7 +746,8 @@ private: * This allows transaction replacement to work as expected, as you want to * have all inputs "available" to check signatures, and any cycles in the * dependency graph are checked directly in AcceptToMemoryPool. - * It also allows you to sign a double-spend directly in signrawtransaction, + * It also allows you to sign a double-spend directly in + * signrawtransactionwithkey and signrawtransactionwithwallet, * as long as the conflicting transaction is not yet confirmed. */ class CCoinsViewMemPool : public CCoinsViewBacked |