aboutsummaryrefslogtreecommitdiff
path: root/src/validation.cpp
diff options
context:
space:
mode:
authorWladimir J. van der Laan <laanwj@gmail.com>2018-05-16 17:49:29 +0200
committerWladimir J. van der Laan <laanwj@gmail.com>2018-05-16 18:30:35 +0200
commit11e7bdfd903ef342c0ff2dcd062d6eab8dd25350 (patch)
treeb90f03f22cacde7fa3874b3224f9743a31a4e25f /src/validation.cpp
parent40c34a0a29f6314c01597a0b9d9e97e5869eaf23 (diff)
parentdd435ad40267f5c50ff17533c696f9302829a6a6 (diff)
Merge #13023: Fix some concurrency issues in ActivateBestChain()
dd435ad Add unit tests for signals generated by ProcessNewBlock() (Jesse Cohen) a3ae8e6 Fix concurrency-related bugs in ActivateBestChain (Jesse Cohen) ecc3c4a Do not unlock cs_main in ABC unless we've actually made progress. (Matt Corallo) Pull request description: Originally this PR was just to add tests around concurrency in block validation - those tests seem to have uncovered another bug in ActivateBestChain - this now fixes that bug and adds tests. ActivateBestChain (invoked after a new block is validated) proceeds in steps - acquiring and releasing cs_main while incrementally disconnecting and connecting blocks to sync to the most work chain known (FindMostWorkChain()). Every time cs_main is released the result of FindMostWorkChain() can change - but currently that value is cached across acquisitions of cs_main and only refreshed when an invalid chain is explored. It needs to be refreshed every time cs_main is reacquired. The test added in https://github.com/bitcoin/bitcoin/pull/13023/commits/6094ce73045fe0b4654ff94327c2059512af88fb will occasionally fail without the commit fixing this issue https://github.com/bitcoin/bitcoin/pull/13023/commits/26bfdbaddbb9f13864deb7241c6d513f22c5ab62 Original description below -- After a bug discovered where UpdatedBlockTip() notifications could be triggered out of order (#12978), these unit tests check certain invariants about these signals. The scheduler test asserts that a SingleThreadedSchedulerClient processes callbacks fully and sequentially. The block validation test generates a random chain and calls ProcessNewBlock from multiple threads at random and in parallel. ValidationInterface callbacks verify that the ordering of BlockConnected BlockDisconnected and UpdatedBlockTip events occur as expected. Tree-SHA512: 4102423a03d2ea28580c7a70add8a6bdb22ef9e33b107c3aadef80d5af02644cdfaae516c44933924717599c81701e0b96fbf9cf38696e9e41372401a5ee1f3c
Diffstat (limited to 'src/validation.cpp')
-rw-r--r--src/validation.cpp78
1 files changed, 50 insertions, 28 deletions
diff --git a/src/validation.cpp b/src/validation.cpp
index f22ae7f9be..3971906424 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -145,6 +145,12 @@ private:
*/
std::set<CBlockIndex*> m_failed_blocks;
+ /**
+ * the ChainState CriticalSection
+ * A lock that must be held when modifying this ChainState - held in ActivateBestChain()
+ */
+ CCriticalSection m_cs_chainstate;
+
public:
CChain chainActive;
BlockMap mapBlockIndex;
@@ -2519,6 +2525,7 @@ void CChainState::PruneBlockIndexCandidates() {
bool CChainState::ActivateBestChainStep(CValidationState& state, const CChainParams& chainparams, CBlockIndex* pindexMostWork, const std::shared_ptr<const CBlock>& pblock, bool& fInvalidFound, ConnectTrace& connectTrace)
{
AssertLockHeld(cs_main);
+
const CBlockIndex *pindexOldTip = chainActive.Tip();
const CBlockIndex *pindexFork = chainActive.FindFork(pindexMostWork);
@@ -2635,6 +2642,12 @@ bool CChainState::ActivateBestChain(CValidationState &state, const CChainParams&
// sanely for performance or correctness!
AssertLockNotHeld(cs_main);
+ // ABC maintains a fair degree of expensive-to-calculate internal state
+ // because this function periodically releases cs_main so that it does not lock up other threads for too long
+ // during large connects - and to allow for e.g. the callback queue to drain
+ // we use m_cs_chainstate to enforce mutual exclusion so that only one caller may execute this function at a time
+ LOCK(m_cs_chainstate);
+
CBlockIndex *pindexMostWork = nullptr;
CBlockIndex *pindexNewTip = nullptr;
int nStopAtHeight = gArgs.GetArg("-stopatheight", DEFAULT_STOPATHEIGHT);
@@ -2648,45 +2661,53 @@ bool CChainState::ActivateBestChain(CValidationState &state, const CChainParams&
SyncWithValidationInterfaceQueue();
}
- const CBlockIndex *pindexFork;
- bool fInitialDownload;
{
LOCK(cs_main);
- ConnectTrace connectTrace(mempool); // Destructed before cs_main is unlocked
+ CBlockIndex* starting_tip = chainActive.Tip();
+ bool blocks_connected = false;
+ do {
+ // We absolutely may not unlock cs_main until we've made forward progress
+ // (with the exception of shutdown due to hardware issues, low disk space, etc).
+ ConnectTrace connectTrace(mempool); // Destructed before cs_main is unlocked
+
+ if (pindexMostWork == nullptr) {
+ pindexMostWork = FindMostWorkChain();
+ }
- CBlockIndex *pindexOldTip = chainActive.Tip();
- if (pindexMostWork == nullptr) {
- pindexMostWork = FindMostWorkChain();
- }
+ // Whether we have anything to do at all.
+ if (pindexMostWork == nullptr || pindexMostWork == chainActive.Tip()) {
+ break;
+ }
- // Whether we have anything to do at all.
- if (pindexMostWork == nullptr || pindexMostWork == chainActive.Tip())
- return true;
+ bool fInvalidFound = false;
+ std::shared_ptr<const CBlock> nullBlockPtr;
+ if (!ActivateBestChainStep(state, chainparams, pindexMostWork, pblock && pblock->GetHash() == pindexMostWork->GetBlockHash() ? pblock : nullBlockPtr, fInvalidFound, connectTrace))
+ return false;
+ blocks_connected = true;
- bool fInvalidFound = false;
- std::shared_ptr<const CBlock> nullBlockPtr;
- if (!ActivateBestChainStep(state, chainparams, pindexMostWork, pblock && pblock->GetHash() == pindexMostWork->GetBlockHash() ? pblock : nullBlockPtr, fInvalidFound, connectTrace))
- return false;
+ if (fInvalidFound) {
+ // Wipe cache, we may need another branch now.
+ pindexMostWork = nullptr;
+ }
+ pindexNewTip = chainActive.Tip();
- if (fInvalidFound) {
- // Wipe cache, we may need another branch now.
- pindexMostWork = nullptr;
- }
- pindexNewTip = chainActive.Tip();
- pindexFork = chainActive.FindFork(pindexOldTip);
- fInitialDownload = IsInitialBlockDownload();
+ for (const PerBlockConnectTrace& trace : connectTrace.GetBlocksConnected()) {
+ assert(trace.pblock && trace.pindex);
+ GetMainSignals().BlockConnected(trace.pblock, trace.pindex, trace.conflictedTxs);
+ }
+ } while (!chainActive.Tip() || (starting_tip && CBlockIndexWorkComparator()(chainActive.Tip(), starting_tip)));
+ if (!blocks_connected) return true;
- for (const PerBlockConnectTrace& trace : connectTrace.GetBlocksConnected()) {
- assert(trace.pblock && trace.pindex);
- GetMainSignals().BlockConnected(trace.pblock, trace.pindex, trace.conflictedTxs);
- }
+ const CBlockIndex* pindexFork = chainActive.FindFork(starting_tip);
+ bool fInitialDownload = IsInitialBlockDownload();
// Notify external listeners about the new tip.
// Enqueue while holding cs_main to ensure that UpdatedBlockTip is called in the order in which blocks are connected
- GetMainSignals().UpdatedBlockTip(pindexNewTip, pindexFork, fInitialDownload);
-
- // Always notify the UI if a new block tip was connected
if (pindexFork != pindexNewTip) {
+ // Notify ValidationInterface subscribers
+ GetMainSignals().UpdatedBlockTip(pindexNewTip, pindexFork, fInitialDownload);
+
+ // Always notify the UI if a new block tip was connected
uiInterface.NotifyBlockTip(fInitialDownload, pindexNewTip);
}
}
@@ -2710,6 +2731,7 @@ bool CChainState::ActivateBestChain(CValidationState &state, const CChainParams&
return true;
}
+
bool ActivateBestChain(CValidationState &state, const CChainParams& chainparams, std::shared_ptr<const CBlock> pblock) {
return g_chainstate.ActivateBestChain(state, chainparams, std::move(pblock));
}