From 96291e7a0f9a363b8d55aa613898af0615b1d0e5 Mon Sep 17 00:00:00 2001
From: Alexander Block <ablock84@gmail.com>
Date: Fri, 1 Mar 2019 06:45:11 +0100
Subject: [PATCH] Cheaper/Faster bailout from TrySignChainTip when already
 signed before

---
 src/llmq/quorums_chainlocks.cpp | 26 +++++++++++++++++---------
 1 file changed, 17 insertions(+), 9 deletions(-)

diff --git a/src/llmq/quorums_chainlocks.cpp b/src/llmq/quorums_chainlocks.cpp
index eed337bfd861d..eb016ed045795 100644
--- a/src/llmq/quorums_chainlocks.cpp
+++ b/src/llmq/quorums_chainlocks.cpp
@@ -227,9 +227,6 @@ void CChainLocksHandler::TrySignChainTip()
     // This will fail when multiple blocks compete, but we accept this for the initial implementation.
     // Later, we'll add the multiple attempts process.
 
-    uint256 requestId = ::SerializeHash(std::make_pair(CLSIG_REQUESTID_PREFIX, pindex->nHeight));
-    uint256 msgHash = pindex->GetBlockHash();
-
     {
         LOCK(cs);
 
@@ -244,6 +241,16 @@ void CChainLocksHandler::TrySignChainTip()
             return;
         }
 
+        if (pindex->nHeight == lastSignedHeight) {
+            // already signed this one
+            return;
+        }
+
+        if (bestChainLock.nHeight >= pindex->nHeight) {
+            // already got the same CLSIG or a better one
+            return;
+        }
+
         if (InternalHasConflictingChainLock(pindex->nHeight, pindex->GetBlockHash())) {
             if (!inEnforceBestChainLock) {
                 // we accepted this block when there was no lock yet, but now a conflicting lock appeared. Invalidate it.
@@ -253,14 +260,15 @@ void CChainLocksHandler::TrySignChainTip()
             }
             return;
         }
+    }
 
-        if (bestChainLock.nHeight >= pindex->nHeight) {
-            // already got the same CLSIG or a better one
-            return;
-        }
+    uint256 requestId = ::SerializeHash(std::make_pair(CLSIG_REQUESTID_PREFIX, pindex->nHeight));
+    uint256 msgHash = pindex->GetBlockHash();
 
-        if (pindex->nHeight == lastSignedHeight) {
-            // already signed this one
+    {
+        LOCK(cs);
+        if (bestChainLock.nHeight >= pindex->nHeight) {
+            // might have happened while we didn't hold cs
             return;
         }
         lastSignedHeight = pindex->nHeight;