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Release cs_main during RewindBlockIndex operation
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@sipa
sipa committed Feb 25, 2019
1 parent 1d34287 commit 436f7d7
Showing 1 changed file with 57 additions and 45 deletions.
102 changes: 57 additions & 45 deletions src/validation.cpp
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Expand Up @@ -4208,77 +4208,89 @@ void CChainState::EraseBlockData(CBlockIndex* index)

bool CChainState::RewindBlockIndex(const CChainParams& params)
{
LOCK(cs_main);
// Note that during -reindex-chainstate we are called with an empty chainActive!

// First erase all post-segwit blocks without witness not in the main chain,
// as this can we done without costly DisconnectTip calls. Active
// blocks will be dealt with below.
for (const auto& entry : mapBlockIndex) {
if (IsWitnessEnabled(entry.second->pprev, params.GetConsensus()) && !(entry.second->nStatus & BLOCK_OPT_WITNESS) && !chainActive.Contains(entry.second)) {
EraseBlockData(entry.second);
// blocks will be dealt with below (releasing cs_main in between).
{
LOCK(cs_main);
for (const auto& entry : mapBlockIndex) {
if (IsWitnessEnabled(entry.second->pprev, params.GetConsensus()) && !(entry.second->nStatus & BLOCK_OPT_WITNESS) && !chainActive.Contains(entry.second)) {
EraseBlockData(entry.second);
}
}
}

// Find what height we need to reorganize to.
CBlockIndex *tip;
int nHeight = 1;
while (nHeight <= chainActive.Height()) {
// Although SCRIPT_VERIFY_WITNESS is now generally enforced on all
// blocks in ConnectBlock, we don't need to go back and
// re-download/re-verify blocks from before segwit actually activated.
if (IsWitnessEnabled(chainActive[nHeight - 1], params.GetConsensus()) && !(chainActive[nHeight]->nStatus & BLOCK_OPT_WITNESS)) {
break;
{
LOCK(cs_main);
while (nHeight <= chainActive.Height()) {
// Although SCRIPT_VERIFY_WITNESS is now generally enforced on all
// blocks in ConnectBlock, we don't need to go back and
// re-download/re-verify blocks from before segwit actually activated.
if (IsWitnessEnabled(chainActive[nHeight - 1], params.GetConsensus()) && !(chainActive[nHeight]->nStatus & BLOCK_OPT_WITNESS)) {
break;
}
nHeight++;
}
nHeight++;
}

tip = chainActive.Tip();
}
// nHeight is now the height of the first insufficiently-validated block, or tipheight + 1

CValidationState state;
CBlockIndex* tip = chainActive.Tip();
// Loop until the tip is below nHeight, or we reach a pruned block.
while (true) {
// Make sure nothing changed from under us (this won't happen because RewindBlockIndex runs before importing/network are active)
assert(tip == chainActive.Tip());
if (tip == nullptr || tip->nHeight < nHeight) break;
if (fPruneMode && !(tip->nStatus & BLOCK_HAVE_DATA)) {
// If pruning, don't try rewinding past the HAVE_DATA point;
// since older blocks can't be served anyway, there's
// no need to walk further, and trying to DisconnectTip()
// will fail (and require a needless reindex/redownload
// of the blockchain).
break;
}

// Disconnect block
if (!DisconnectTip(state, params, nullptr)) {
return error("RewindBlockIndex: unable to disconnect block at height %i (%s)", tip->nHeight, FormatStateMessage(state));
}
{
LOCK(cs_main);
// Make sure nothing changed from under us (this won't happen because RewindBlockIndex runs before importing/network are active)
assert(tip == chainActive.Tip());
if (tip == nullptr || tip->nHeight < nHeight) break;
if (fPruneMode && !(tip->nStatus & BLOCK_HAVE_DATA)) {
// If pruning, don't try rewinding past the HAVE_DATA point;
// since older blocks can't be served anyway, there's
// no need to walk further, and trying to DisconnectTip()
// will fail (and require a needless reindex/redownload
// of the blockchain).
break;
}

// Reduce validity flag and have-data flags.
// We do this after actual disconnecting, otherwise we'll end up writing the lack of data
// to disk before writing the chainstate, resulting in a failure to continue if interrupted.
// Note: If we encounter an insufficiently validated block that
// is on chainActive, it must be because we are a pruning node, and
// this block or some successor doesn't HAVE_DATA, so we were unable to
// rewind all the way. Blocks remaining on chainActive at this point
// must not have their validity reduced.
EraseBlockData(tip);
// Disconnect block
if (!DisconnectTip(state, params, nullptr)) {
return error("RewindBlockIndex: unable to disconnect block at height %i (%s)", tip->nHeight, FormatStateMessage(state));
}

tip = tip->pprev;
// Reduce validity flag and have-data flags.
// We do this after actual disconnecting, otherwise we'll end up writing the lack of data
// to disk before writing the chainstate, resulting in a failure to continue if interrupted.
// Note: If we encounter an insufficiently validated block that
// is on chainActive, it must be because we are a pruning node, and
// this block or some successor doesn't HAVE_DATA, so we were unable to
// rewind all the way. Blocks remaining on chainActive at this point
// must not have their validity reduced.
EraseBlockData(tip);

tip = tip->pprev;
}
// Occasionally flush state to disk.
if (!FlushStateToDisk(params, state, FlushStateMode::PERIODIC)) {
LogPrintf("RewindBlockIndex: unable to flush state to disk (%s)\n", FormatStateMessage(state));
return false;
}
}

if (chainActive.Tip() != nullptr) {
// We can't prune block index candidates based on our tip if we have
// no tip due to chainActive being empty!
PruneBlockIndexCandidates();
{
LOCK(cs_main);
if (chainActive.Tip() != nullptr) {
// We can't prune block index candidates based on our tip if we have
// no tip due to chainActive being empty!
PruneBlockIndexCandidates();

CheckBlockIndex(params.GetConsensus());
CheckBlockIndex(params.GetConsensus());
}
}

return true;
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