Allow ActivateBestChain to release its lock on cs_main

src/main.cpp

@@ -2079,18 +2079,11 @@ static CBlockIndex* FindMostWorkChain() {
     } while(true);
 }
 
-// Try to activate to the most-work chain (thereby connecting it).
-bool ActivateBestChain(CValidationState &state) {
-    LOCK(cs_main);
+// Try to make some progress towards making pindexMostWork the active block.
+static bool ActivateBestChainStep(CValidationState &state, CBlockIndex *pindexMostWork) {
+    AssertLockHeld(cs_main);
     CBlockIndex *pindexOldTip = chainActive.Tip();
-    bool fComplete = false;
-    while (!fComplete) {
-        CBlockIndex *pindexMostWork = FindMostWorkChain();
     CBlockIndex *pindexFork = chainActive.FindFork(pindexMostWork);
-        fComplete = true;
-
-        // Check whether we have something to do.
-        if (pindexMostWork == NULL) break;
 
     // Disconnect active blocks which are no longer in the best chain.
     while (chainActive.Tip() && chainActive.Tip() != pindexFork) {
@@ -2113,13 +2106,16 @@ bool ActivateBestChain(CValidationState &state) {
                 // The block violates a consensus rule.
                 if (!state.CorruptionPossible())
                     InvalidChainFound(vpindexToConnect.back());
-                    fComplete = false;
                 state = CValidationState();
                 break;
             } else {
                 // A system error occurred (disk space, database error, ...).
                 return false;
             }
+        } else {
+            if (!pindexOldTip || chainActive.Tip()->nChainWork > pindexOldTip->nChainWork) {
+                // We're in a better position than we were. Return temporarily to release the lock.
+                break;
             }
         }
     }
@@ -2136,6 +2132,28 @@ bool ActivateBestChain(CValidationState &state) {
     return true;
 }
 
+bool ActivateBestChain(CValidationState &state) {
+    do {
+        boost::this_thread::interruption_point();
+
+        LOCK(cs_main);
+
+        // Check whether we're done (this could be avoided after the first run,
+        // but that's not worth optimizing.
+        CBlockIndex *pindexMostWork = FindMostWorkChain();
+        if (pindexMostWork == NULL || pindexMostWork == chainActive.Tip())
+            return true;
+
+        if (!ActivateBestChainStep(state, pindexMostWork))
+            return false;
+
+        // Check whether we're done now.
+        if (pindexMostWork == chainActive.Tip())
+            return true;
+    } while(true);
+
+    return true;
+}
 
 CBlockIndex* AddToBlockIndex(CBlockHeader& block)
 {