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author | fanquake <fanquake@gmail.com> | 2022-10-10 14:15:18 +0800 |
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committer | fanquake <fanquake@gmail.com> | 2022-10-10 14:23:00 +0800 |
commit | 4175c332b9e7334ffdf659591ca31f750ebd173c (patch) | |
tree | e12e746a3897e7302a9c80d7fd8ed286be29e1cf /src | |
parent | cf3db7c256d241215480a198e5e302e9df877fc4 (diff) | |
parent | 8891949bdcb25093d3a6703ae8228c3c3687d3a4 (diff) | |
download | bitcoin-4175c332b9e7334ffdf659591ca31f750ebd173c.tar.xz |
Merge bitcoin/bitcoin#26215: index: Improve BaseIndex::BlockUntilSyncedToCurrentChain reliability
8891949bdcb25093d3a6703ae8228c3c3687d3a4 index: Improve BaseIndex::BlockUntilSyncedToCurrentChain reliability (Ryan Ofsky)
Pull request description:
Since commit f08c9fb0c6a799e3cb75ca5f763a746471625beb from PR https://github.com/bitcoin/bitcoin/pull/21726, index `BlockUntilSyncedToCurrentChain` behavior has been less reliable, and there has also been a race condition in the `coinstatsindex_initial_sync` unit test.
It seems better for `BlockUntilSyncedToCurrentChain` to actually wait for the last connected block to be fully processed, than to be able to return before prune locks are set, so this switches the order of `m_best_block_index = block;` and `UpdatePruneLock` statements in `SetBestBlockIndex` to make it more reliable.
Also since commit f08c9fb0c6a799e3cb75ca5f763a746471625beb, there has been a race condition in the `coinstatsindex_initial_sync` test. Before that commit, the atomic index best block pointer `m_best_block_index` was updated as the last step of `BaseIndex::BlockConnected`, so `BlockUntilSyncedToCurrentChain` could safely be used in tests to wait for the last `BlockConnected` notification to be finished before stopping and destroying the index. But after that commit, calling `BlockUntilSyncedToCurrentChain` is no longer sufficient, and there is a race between the test shutdown code which destroys the index object and the new code introduced in that commit calling `AllowPrune()` and `GetName()` on the index object. Reproducibility instructions for this are in https://github.com/bitcoin/bitcoin/issues/25365#issuecomment-1259744133
This commit fixes the `coinstatsindex_initial_sync` race condition, even though it will require an additional change to silence TSAN false positives, https://github.com/bitcoin/bitcoin/pull/26188, after it is fixed. So this partially addresses but does not resolve the bug reporting TSAN errors https://github.com/bitcoin/bitcoin/issues/25365.
There is no known race condition outside of test code currently, because the bitcoind `Shutdown` function calls `FlushBackgroundCallbacks` not `BlockUntilSyncedToCurrentChain` to safely shut down.
Co-authored-by: vasild
Co-authored-by: MarcoFalke
ACKs for top commit:
mzumsande:
re-ACK 8891949bdcb25093d3a6703ae8228c3c3687d3a4
Tree-SHA512: 52e29e3772a0c92873c54e5ffb31dd66a909b68a2031b7585713cd1d976811289c98bd9bb41679a8689062f03be4f97bb8368696e789caa4607c2fd8b1fe289b
Diffstat (limited to 'src')
-rw-r--r-- | src/index/base.cpp | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/src/index/base.cpp b/src/index/base.cpp index 88c2ce98fa..3eea09b17d 100644 --- a/src/index/base.cpp +++ b/src/index/base.cpp @@ -298,6 +298,10 @@ void BaseIndex::BlockConnected(const std::shared_ptr<const CBlock>& block, const } interfaces::BlockInfo block_info = kernel::MakeBlockInfo(pindex, block.get()); if (CustomAppend(block_info)) { + // Setting the best block index is intentionally the last step of this + // function, so BlockUntilSyncedToCurrentChain callers waiting for the + // best block index to be updated can rely on the block being fully + // processed, and the index object being safe to delete. SetBestBlockIndex(pindex); } else { FatalError("%s: Failed to write block %s to index", @@ -414,10 +418,17 @@ IndexSummary BaseIndex::GetSummary() const void BaseIndex::SetBestBlockIndex(const CBlockIndex* block) { assert(!node::fPruneMode || AllowPrune()); - m_best_block_index = block; if (AllowPrune() && block) { node::PruneLockInfo prune_lock; prune_lock.height_first = block->nHeight; WITH_LOCK(::cs_main, m_chainstate->m_blockman.UpdatePruneLock(GetName(), prune_lock)); } + + // Intentionally set m_best_block_index as the last step in this function, + // after updating prune locks above, and after making any other references + // to *this, so the BlockUntilSyncedToCurrentChain function (which checks + // m_best_block_index as an optimization) can be used to wait for the last + // BlockConnected notification and safely assume that prune locks are + // updated and that the index object is safe to delete. + m_best_block_index = block; } |