From b354251f1aa2e98585de0942d1fb4f1ec599a39b Mon Sep 17 00:00:00 2001
From: Luke Dashjr <luke-jr+git@utopios.org>
Date: Wed, 9 May 2012 17:02:07 +0000
Subject: [PATCH] Bugfix: getwork: NULL pindexPrev across CreateNewBlock, in
 case it fails

---
 rpc.cpp | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/rpc.cpp b/rpc.cpp
index 113de85a9..a579a5d90 100644
--- a/rpc.cpp
+++ b/rpc.cpp
@@ -967,8 +967,13 @@ Value getwork(const Array& params, bool fHelp)
                     delete pblock;
                 vNewBlock.clear();
             }
+
+            // Clear pindexPrev so future getworks make a new block, despite any failures from here on
+            pindexPrev = NULL;
+
+            // Store the pindexBest used before CreateNewBlock, to avoid races
             nTransactionsUpdatedLast = nTransactionsUpdated;
-            pindexPrev = pindexBest;
+            CBlockIndex* pindexPrevNew = pindexBest;
             nStart = GetTime();
 
             // Create new block
@@ -976,6 +981,9 @@ Value getwork(const Array& params, bool fHelp)
             if (!pblock)
                 throw JSONRPCError(-7, "Out of memory");
             vNewBlock.push_back(pblock);
+
+            // Need to update only after we know CreateNewBlock succeeded
+            pindexPrev = pindexPrevNew;
         }
 
         // Update nTime