[net processin] Don't take cs_main in FindTxForGetData

Taking cs_main is no longer necessary since we moved
`m_recently_announced_invs` to `Peer` and `mapRelay` is actually only
accessed from the message processing thread.

Author: dergoegge

src/net_processing.cpp

@@ -909,7 +909,7 @@ class PeerManagerImpl final : public PeerManager
 
     /** Determine whether or not a peer can request a transaction, and return it (or nullptr if not found or not allowed). */
     CTransactionRef FindTxForGetData(const Peer& peer, const GenTxid& gtxid, const std::chrono::seconds mempool_req, const std::chrono::seconds now)
-        LOCKS_EXCLUDED(cs_main) EXCLUSIVE_LOCKS_REQUIRED(NetEventsInterface::g_msgproc_mutex);
+        EXCLUSIVE_LOCKS_REQUIRED(NetEventsInterface::g_msgproc_mutex);
 
     void ProcessGetData(CNode& pfrom, Peer& peer, const std::atomic<bool>& interruptMsgProc)
         EXCLUSIVE_LOCKS_REQUIRED(!m_most_recent_block_mutex, peer.m_getdata_requests_mutex, NetEventsInterface::g_msgproc_mutex)
@@ -920,9 +920,9 @@ class PeerManagerImpl final : public PeerManager
 
     /** Relay map (txid or wtxid -> CTransactionRef) */
     typedef std::map<uint256, CTransactionRef> MapRelay;
-    MapRelay mapRelay GUARDED_BY(cs_main);
+    MapRelay mapRelay GUARDED_BY(NetEventsInterface::g_msgproc_mutex);
     /** Expiration-time ordered list of (expire time, relay map entry) pairs. */
-    std::deque<std::pair<std::chrono::microseconds, MapRelay::iterator>> g_relay_expiration GUARDED_BY(cs_main);
+    std::deque<std::pair<std::chrono::microseconds, MapRelay::iterator>> g_relay_expiration GUARDED_BY(NetEventsInterface::g_msgproc_mutex);
 
     /**
      * When a peer sends us a valid block, instruct it to announce blocks to us
@@ -2270,16 +2270,13 @@ CTransactionRef PeerManagerImpl::FindTxForGetData(const Peer& peer, const GenTxi
         }
     }
 
-    {
-        LOCK(cs_main);
-        // Otherwise, the transaction must have been announced recently.
-        if (Assume(peer.GetTxRelay())->m_recently_announced_invs.contains(gtxid.GetHash())) {
-            // If it was, it can be relayed from either the mempool...
-            if (txinfo.tx) return std::move(txinfo.tx);
-            // ... or the relay pool.
-            auto mi = mapRelay.find(gtxid.GetHash());
-            if (mi != mapRelay.end()) return mi->second;
-        }
+    // Otherwise, the transaction must have been announced recently.
+    if (Assume(peer.GetTxRelay())->m_recently_announced_invs.contains(gtxid.GetHash())) {
+        // If it was, it can be relayed from either the mempool...
+        if (txinfo.tx) return std::move(txinfo.tx);
+        // ... or the relay pool.
+        auto mi = mapRelay.find(gtxid.GetHash());
+        if (mi != mapRelay.end()) return mi->second;
     }
 
     return {};