Merge bitcoin/bitcoin#24079: refactor: replace RecursiveMutex cs_SubVer with Mutex (and rename)

30927cb refactor: replace RecursiveMutex `m_subver_mutex` with Mutex (Sebastian Falbesoner)
0639aba scripted-diff: rename `cs_SubVer` -> `m_subver_mutex` (Sebastian Falbesoner)

Pull request description:

  This PR is related to #19303 and gets rid of the RecursiveMutex `cs_SubVer`. Both of the critical sections only directly access the guarded variable, i.e. it is not possible that within one section another one is called, and we can use a regular Mutex.

ACKs for top commit:
  hebasto:
    ACK 30927cb, I have reviewed the code and it looks OK, I agree it can be merged.

Tree-SHA512: 2faead792ea0b2f79f9f7fe99acde5cf2bfcd2f15c51fbb6cb1099d4f81276001a492f7d46a5139055f4366c2d58a36a8ba19f21d56df20e0ed93af3141dbe11

Author: MarcoFalke

src/net.cpp

@@ -595,7 +595,7 @@ void CNode::CopyStats(CNodeStats& stats)
     X(m_addr_name);
     X(nVersion);
     {
-        LOCK(cs_SubVer);
+        LOCK(m_subver_mutex);
         X(cleanSubVer);
     }
     stats.fInbound = IsInboundConn();

src/net.h

@@ -434,12 +434,12 @@ class CNode
     //! Whether this peer is an inbound onion, i.e. connected via our Tor onion service.
     const bool m_inbound_onion;
     std::atomic<int> nVersion{0};
-    RecursiveMutex cs_SubVer;
+    Mutex m_subver_mutex;
     /**
      * cleanSubVer is a sanitized string of the user agent byte array we read
      * from the wire. This cleaned string can safely be logged or displayed.
      */
-    std::string cleanSubVer GUARDED_BY(cs_SubVer){};
+    std::string cleanSubVer GUARDED_BY(m_subver_mutex){};
     bool m_prefer_evict{false}; // This peer is preferred for eviction.
     bool HasPermission(NetPermissionFlags permission) const {
         return NetPermissions::HasFlag(m_permissionFlags, permission);

src/net_processing.cpp

@@ -2636,7 +2636,7 @@ void PeerManagerImpl::ProcessMessage(CNode& pfrom, const std::string& msg_type,
         pfrom.nServices = nServices;
         pfrom.SetAddrLocal(addrMe);
         {
-            LOCK(pfrom.cs_SubVer);
+            LOCK(pfrom.m_subver_mutex);
             pfrom.cleanSubVer = cleanSubVer;
         }
         peer->m_starting_height = starting_height;