versionbits: Use dedicated lock instead of cs_main

Author: ajtowns

src/rpc/blockchain.cpp

@@ -1361,7 +1361,7 @@ static void BuriedForkDescPushBack(UniValue& softforks, const std::string &name,
     softforks.pushKV(name, rv);
 }
 
-static void BIP9SoftForkDescPushBack(const CBlockIndex* active_chain_tip, UniValue& softforks, const std::string &name, const Consensus::Params& consensusParams, Consensus::DeploymentPos id) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
+static void BIP9SoftForkDescPushBack(const CBlockIndex* active_chain_tip, UniValue& softforks, const std::string &name, const Consensus::Params& consensusParams, Consensus::DeploymentPos id)
 {
     // For BIP9 deployments.
     // Deployments that are never active are hidden.

src/validation.cpp

@@ -1606,11 +1606,10 @@ void StopScriptCheckWorkerThreads()
     scriptcheckqueue.StopWorkerThreads();
 }
 
-VersionBitsCache versionbitscache GUARDED_BY(cs_main);
+VersionBitsCache versionbitscache;
 
 int32_t ComputeBlockVersion(const CBlockIndex* pindexPrev, const Consensus::Params& params)
 {
-    LOCK(cs_main);
     int32_t nVersion = VERSIONBITS_TOP_BITS;
 
     for (int i = 0; i < (int)Consensus::MAX_VERSION_BITS_DEPLOYMENTS; i++) {
@@ -1659,9 +1658,8 @@ static bool IsScriptWitnessEnabled(const Consensus::Params& params)
     return params.SegwitHeight != std::numeric_limits<int>::max();
 }
 
-static unsigned int GetBlockScriptFlags(const CBlockIndex* pindex, const Consensus::Params& consensusparams) EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
-    AssertLockHeld(cs_main);
-
+static unsigned int GetBlockScriptFlags(const CBlockIndex* pindex, const Consensus::Params& consensusparams)
+{
     unsigned int flags = SCRIPT_VERIFY_NONE;
 
     // BIP16 didn't become active until Apr 1 2012 (on mainnet, and

src/versionbits.cpp

@@ -192,6 +192,7 @@ class VersionBitsConditionChecker : public AbstractThresholdConditionChecker {
 
 ThresholdState VersionBitsState(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos, VersionBitsCache& cache)
 {
+    LOCK(cache.mutex);
     return VersionBitsConditionChecker(pos).GetStateFor(pindexPrev, params, cache.caches[pos]);
 }
 
@@ -202,6 +203,7 @@ BIP9Stats VersionBitsStatistics(const CBlockIndex* pindexPrev, const Consensus::
 
 int VersionBitsStateSinceHeight(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos, VersionBitsCache& cache)
 {
+    LOCK(cache.mutex);
     return VersionBitsConditionChecker(pos).GetStateSinceHeightFor(pindexPrev, params, cache.caches[pos]);
 }
 
@@ -212,6 +214,7 @@ uint32_t VersionBitsMask(const Consensus::Params& params, Consensus::DeploymentP
 
 void VersionBitsCache::Clear()
 {
+    LOCK(mutex);
     for (unsigned int d = 0; d < Consensus::MAX_VERSION_BITS_DEPLOYMENTS; d++) {
         caches[d].clear();
     }

src/versionbits.h

@@ -6,6 +6,8 @@
 #define BITCOIN_VERSIONBITS_H
 
 #include <chain.h>
+#include <sync.h>
+
 #include <map>
 
 /** What block version to use for new blocks (pre versionbits) */
@@ -75,7 +77,8 @@ class AbstractThresholdConditionChecker {
  *  keyed by the bit position used to signal support. */
 struct VersionBitsCache
 {
-    ThresholdConditionCache caches[Consensus::MAX_VERSION_BITS_DEPLOYMENTS];
+    Mutex mutex;
+    ThresholdConditionCache caches[Consensus::MAX_VERSION_BITS_DEPLOYMENTS] GUARDED_BY(mutex);
 
     void Clear();
 };