refactor: enhance CSigSharesManager for single-member quorum handling

Added a new method, ProcessRecoveredSigUnlocked, to handle recovered signatures outside of the lock to improve thread safety. Updated TryRecoverSig to utilize this new method for single-member quorum cases, ensuring proper lock management during signature processing.

Author: PastaPastaPasta

src/llmq/signing_shares.cpp

@@ -780,6 +780,7 @@ void CSigSharesManager::TryRecoverSig(const CQuorum& quorum, const uint256& id,
 
     std::vector<CBLSSignature> sigSharesForRecovery;
     std::vector<CBLSId> idsForRecovery;
+    std::shared_ptr<CRecoveredSig> singleMemberRecoveredSig;
     {
         LOCK(cs);
 
@@ -802,10 +803,10 @@ void CSigSharesManager::TryRecoverSig(const CQuorum& quorum, const uint256& id,
             LogPrint(BCLog::LLMQ_SIGS, "CSigSharesManager::%s -- recover single-node signature. id=%s, msgHash=%s\n",
                      __func__, id.ToString(), msgHash.ToString());
 
-            auto rs = std::make_shared<CRecoveredSig>(quorum.params.type, quorum.qc->quorumHash, id, msgHash,
+            singleMemberRecoveredSig = std::make_shared<CRecoveredSig>(quorum.params.type, quorum.qc->quorumHash, id, msgHash,
                                                       recoveredSig);
-            sigman.ProcessRecoveredSig(rs, m_peerman);
-            return; // end of single-quorum processing
+            // Release lock before calling ProcessRecoveredSig to avoid double lock in HandleNewRecoveredSig
+            // ProcessRecoveredSig will synchronously call HandleNewRecoveredSig which requires the lock
         }
 
         sigSharesForRecovery.reserve((size_t) quorum.params.threshold);
@@ -822,6 +823,12 @@ void CSigSharesManager::TryRecoverSig(const CQuorum& quorum, const uint256& id,
         }
     }
 
+    // Handle single-member quorum case after releasing the lock
+    if (singleMemberRecoveredSig) {
+        ProcessRecoveredSigUnlocked(singleMemberRecoveredSig);
+        return; // end of single-quorum processing
+    }
+
     // now recover it
     cxxtimer::Timer t(true);
     CBLSSignature recoveredSig;
@@ -850,7 +857,12 @@ void CSigSharesManager::TryRecoverSig(const CQuorum& quorum, const uint256& id,
         }
     }
 
-    sigman.ProcessRecoveredSig(rs, m_peerman);
+    ProcessRecoveredSigUnlocked(rs);
+}
+
+void CSigSharesManager::ProcessRecoveredSigUnlocked(const std::shared_ptr<const CRecoveredSig>& recoveredSig)
+{
+    sigman.ProcessRecoveredSig(recoveredSig, m_peerman);
 }
 
 CDeterministicMNCPtr CSigSharesManager::SelectMemberForRecovery(const CQuorum& quorum, const uint256 &id, int attempt)

src/llmq/signing_shares.h

@@ -477,6 +477,9 @@ class CSigSharesManager : public CRecoveredSigsListener
     void ProcessSigShare(const CSigShare& sigShare, const CQuorumCPtr& quorum) EXCLUSIVE_LOCKS_REQUIRED(!cs);
     void TryRecoverSig(const CQuorum& quorum, const uint256& id, const uint256& msgHash) EXCLUSIVE_LOCKS_REQUIRED(!cs);
 
+private:
+    void ProcessRecoveredSigUnlocked(const std::shared_ptr<const CRecoveredSig>& recoveredSig) LOCKS_EXCLUDED(cs);
+
     bool GetSessionInfoByRecvId(NodeId nodeId, uint32_t sessionId, CSigSharesNodeState::SessionInfo& retInfo)
         EXCLUSIVE_LOCKS_REQUIRED(!cs);
     static CSigShare RebuildSigShare(const CSigSharesNodeState::SessionInfo& session, const std::pair<uint16_t, CBLSLazySignature>& in);