Merge #12151: rpc: Remove cs_main lock from blockToJSON and blockheaderToJSON

b9f226b41f rpc: Remove cs_main lock from blockToJSON and blockHeaderToJSON (João Barbosa)
343b98cbcd rpc: Specify chain tip instead of chain in GetDifficulty (João Barbosa)
54dc13b6a2 rpc: Fix SoftForkMajorityDesc and SoftForkDesc signatures (João Barbosa)

Pull request description:

  Motivated by https://github.com/bitcoin/bitcoin/pull/11913#discussion_r157798157, this pull makes `blockToJSON` and `blockheaderToJSON` free of `cs_main` locks.

  Locking `cs_main` was required to access `chainActive` in order to check if the block was in the chain and to retrieve the next block index.

  With the this approach, `CBlockIndex::GetAncestor()` is used in a way to check if the block belongs to the specified chain tip and, at the same time, get the next block index.

Tree-SHA512: a6720ace0182c19033bbed1a404f729d793574db8ab16e0966ffe412145611e32c30aaab02975d225df6d439d7b9ef2070e732b16137a902b0293c8cddfeb85f

1 files changed, 7 insertions, 10 deletions

diff --git a/src/rest.cpp b/src/rest.cpp
index 4988e6ed26..4f26e3afb5 100644
--- a/src/rest.cpp
+++ b/src/rest.cpp
@@ -136,10 +136,12 @@ static bool rest_headers(HTTPRequest* req,
     if (!ParseHashStr(hashStr, hash))
         return RESTERR(req, HTTP_BAD_REQUEST, "Invalid hash: " + hashStr);
 
+    const CBlockIndex* tip = nullptr;
     std::vector<const CBlockIndex *> headers;
     headers.reserve(count);
     {
         LOCK(cs_main);
+        tip = chainActive.Tip();
         const CBlockIndex* pindex = LookupBlockIndex(hash);
         while (pindex != nullptr && chainActive.Contains(pindex)) {
             headers.push_back(pindex);
@@ -175,11 +177,8 @@ static bool rest_headers(HTTPRequest* req,
     }
     case RetFormat::JSON: {
         UniValue jsonHeaders(UniValue::VARR);
-        {
-            LOCK(cs_main);
-            for (const CBlockIndex *pindex : headers) {
-                jsonHeaders.push_back(blockheaderToJSON(pindex));
-            }
+        for (const CBlockIndex *pindex : headers) {
+            jsonHeaders.push_back(blockheaderToJSON(tip, pindex));
         }
         std::string strJSON = jsonHeaders.write() + "\n";
         req->WriteHeader("Content-Type", "application/json");
@@ -207,8 +206,10 @@ static bool rest_block(HTTPRequest* req,
 
     CBlock block;
     CBlockIndex* pblockindex = nullptr;
+    CBlockIndex* tip = nullptr;
     {
         LOCK(cs_main);
+        tip = chainActive.Tip();
         pblockindex = LookupBlockIndex(hash);
         if (!pblockindex) {
             return RESTERR(req, HTTP_NOT_FOUND, hashStr + " not found");
@@ -241,11 +242,7 @@ static bool rest_block(HTTPRequest* req,
     }
 
     case RetFormat::JSON: {
-        UniValue objBlock;
-        {
-            LOCK(cs_main);
-            objBlock = blockToJSON(block, pblockindex, showTxDetails);
-        }
+        UniValue objBlock = blockToJSON(block, tip, pblockindex, showTxDetails);
         std::string strJSON = objBlock.write() + "\n";
         req->WriteHeader("Content-Type", "application/json");
         req->WriteReply(HTTP_OK, strJSON);