Merge bitcoin#21845: net processing: Don't require locking cs_main before calling RelayTransactions()

39e1971 [net processing] Add internal _RelayTransactions() (John Newbery)

Pull request description:

  As part of the general effort to reduce cs_main usage in net_processing, this removes the need to be holding `cs_main` when calling `RelayTransactions()` from outside net_processing. Internally, we lock `cs_main` and call an internal `_RelayTransactions()` function that _does_ require `cs_main`.

ACKs for top commit:
  MarcoFalke:
    re-unsigned-code-review ACK 39e1971
  promag:
    Code review ACK 39e1971, just included sync.h since last review.
  ajtowns:
    ACK 39e1971

Tree-SHA512: dc08441233adfb8eaac501cf497cb4bad029eb723bd3fa8a3d8b7e49cc984c98859b95780ad15f5701d62ac745a8223beb0df405e3d49d95a8c86c8be17c9543

Author: fanquake

src/net_processing.cpp

@@ -25,6 +25,7 @@
 #include <reverse_iterator.h>
 #include <scheduler.h>
 #include <streams.h>
+#include <sync.h>
 #include <tinyformat.h>
 #include <txmempool.h>
 #include <txorphanage.h>
@@ -256,6 +257,9 @@ class PeerManagerImpl final : public PeerManager
                         const std::chrono::microseconds time_received, const std::atomic<bool>& interruptMsgProc) override;
 
 private:
+    void _RelayTransaction(const uint256& txid, const uint256& wtxid)
+        EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+
     /** Consider evicting an outbound peer based on the amount of time they've been behind our tip */
     void ConsiderEviction(CNode& pto, int64_t time_in_seconds) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
@@ -1015,7 +1019,7 @@ void PeerManagerImpl::ReattemptInitialBroadcast(CScheduler& scheduler)
 
         if (tx != nullptr) {
             LOCK(cs_main);
-            RelayTransaction(txid, tx->GetWitnessHash());
+            _RelayTransaction(txid, tx->GetWitnessHash());
         } else {
             m_mempool.RemoveUnbroadcastTx(txid, true);
         }
@@ -1511,6 +1515,11 @@ void PeerManagerImpl::SendPings()
 }
 
 void PeerManagerImpl::RelayTransaction(const uint256& txid, const uint256& wtxid)
+{
+    WITH_LOCK(cs_main, _RelayTransaction(txid, wtxid););
+}
+
+void PeerManagerImpl::_RelayTransaction(const uint256& txid, const uint256& wtxid)
 {
     m_connman.ForEachNode([&txid, &wtxid](CNode* pnode) EXCLUSIVE_LOCKS_REQUIRED(::cs_main) {
         AssertLockHeld(::cs_main);
@@ -2087,7 +2096,7 @@ void PeerManagerImpl::ProcessOrphanTx(std::set<uint256>& orphan_work_set)
 
         if (result.m_result_type == MempoolAcceptResult::ResultType::VALID) {
             LogPrint(BCLog::MEMPOOL, "   accepted orphan tx %s\n", orphanHash.ToString());
-            RelayTransaction(orphanHash, porphanTx->GetWitnessHash());
+            _RelayTransaction(orphanHash, porphanTx->GetWitnessHash());
             m_orphanage.AddChildrenToWorkSet(*porphanTx, orphan_work_set);
             m_orphanage.EraseTx(orphanHash);
             for (const CTransactionRef& removedTx : result.m_replaced_transactions.value()) {
@@ -3055,7 +3064,7 @@ void PeerManagerImpl::ProcessMessage(CNode& pfrom, const std::string& msg_type,
                     LogPrintf("Not relaying non-mempool transaction %s from forcerelay peer=%d\n", tx.GetHash().ToString(), pfrom.GetId());
                 } else {
                     LogPrintf("Force relaying tx %s from peer=%d\n", tx.GetHash().ToString(), pfrom.GetId());
-                    RelayTransaction(tx.GetHash(), tx.GetWitnessHash());
+                    _RelayTransaction(tx.GetHash(), tx.GetWitnessHash());
                 }
             }
             return;
@@ -3070,7 +3079,7 @@ void PeerManagerImpl::ProcessMessage(CNode& pfrom, const std::string& msg_type,
             // requests for it.
             m_txrequest.ForgetTxHash(tx.GetHash());
             m_txrequest.ForgetTxHash(tx.GetWitnessHash());
-            RelayTransaction(tx.GetHash(), tx.GetWitnessHash());
+            _RelayTransaction(tx.GetHash(), tx.GetWitnessHash());
             m_orphanage.AddChildrenToWorkSet(tx, peer->m_orphan_work_set);
 
             pfrom.nLastTXTime = GetTime();

src/net_processing.h

@@ -7,16 +7,13 @@
 #define BITCOIN_NET_PROCESSING_H
 
 #include <net.h>
-#include <sync.h>
 #include <validationinterface.h>
 
 class CAddrMan;
 class CChainParams;
 class CTxMemPool;
 class ChainstateManager;
 
-extern RecursiveMutex cs_main;
-
 /** Default for -maxorphantx, maximum number of orphan transactions kept in memory */
 static const unsigned int DEFAULT_MAX_ORPHAN_TRANSACTIONS = 100;
 /** Default number of orphan+recently-replaced txn to keep around for block reconstruction */
@@ -49,8 +46,7 @@ class PeerManager : public CValidationInterface, public NetEventsInterface
     virtual bool IgnoresIncomingTxs() = 0;
 
     /** Relay transaction to all peers. */
-    virtual void RelayTransaction(const uint256& txid, const uint256& wtxid)
-        EXCLUSIVE_LOCKS_REQUIRED(cs_main) = 0;
+    virtual void RelayTransaction(const uint256& txid, const uint256& wtxid) = 0;
 
     /** Send ping message to all peers */
     virtual void SendPings() = 0;

src/node/transaction.cpp

@@ -100,8 +100,6 @@ TransactionError BroadcastTransaction(NodeContext& node, const CTransactionRef t
         // the mempool tracks locally submitted transactions to make a
         // best-effort of initial broadcast
         node.mempool->AddUnbroadcastTx(hashTx);
-
-        LOCK(cs_main);
         node.peerman->RelayTransaction(hashTx, tx->GetWitnessHash());
     }