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Merge bitcoin/bitcoin#22824: refactor: remove RecursiveMutex cs_nBlockSequenceId

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0bd882b7405414b5355e69a9fdcd7a533e504b6b refactor: remove RecursiveMutex cs_nBlockSequenceId (Sebastian Falbesoner)

Pull request description:

  The RecursiveMutex `cs_nBlockSequenceId` is only used at one place in `CChainState::ReceivedBlockTransactions()` to atomically read-and-increment the nBlockSequenceId member:

  83daf47898/src/validation.cpp (L2973-L2976)

  ~~For this simple use-case, we can make the member `std::atomic` instead to achieve the same result (see https://en.cppreference.com/w/cpp/atomic/atomic/operator_arith).~~

  ~~This is related to #19303. As suggested in the issue, I first planned to change the `RecursiveMutex` to `Mutex` (still possible if the change doesn't get Concept ACKs), but using a Mutex for this simple operation seems to be overkill. Note that at the time when this mutex was introduced (PR #3370, commit 75f51f2a63) `std::atomic` were not used in the codebase yet -- according to `git log -S std::atomic` they have first appeared in 2016 (commit 7e908c7b82), probably also because the compilers didn't support them properly earlier.~~

  At this point, the cs_main lock is set, hence we can use a plain int for the member and mark it as guarded by cs_main.

ACKs for top commit:
  Zero-1729:
    ACK 0bd882b
  promag:
    Code review ACK 0bd882b7405414b5355e69a9fdcd7a533e504b6b.
  hebasto:
    ACK 0bd882b7405414b5355e69a9fdcd7a533e504b6b

Tree-SHA512: 435271ac8f877074099ddb31436665b500e555f7cab899e5c8414af299b154d1249996be500e8fdeff64e4639bcaf7386e12510b738ec6f20e415e7e35afaea9
This commit is contained in:
MarcoFalke 2021-08-30 10:07:28 +02:00 committed by pasta
parent a9b1575fe8
commit 51630d2e5e
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GPG Key ID: 52527BEDABE87984
2 changed files with 3 additions and 7 deletions
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5
src/validation.cpp
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@ -3688,10 +3688,7 @@ void CChainState::ReceivedBlockTransactions(const CBlock& block, CBlockIndex* pi
CBlockIndex *pindex = queue.front();
queue.pop_front();
pindex->nChainTx = (pindex->pprev ? pindex->pprev->nChainTx : 0) + pindex->nTx;
{
LOCK(cs_nBlockSequenceId);
pindex->nSequenceId = nBlockSequenceId++;
}
pindex->nSequenceId = nBlockSequenceId++;
if (m_chain.Tip() == nullptr || !setBlockIndexCandidates.value_comp()(pindex, m_chain.Tip())) {
if (!(pindex->nStatus & BLOCK_CONFLICT_CHAINLOCK)) {
setBlockIndexCandidates.insert(pindex);

5
src/validation.h
View File

@ -629,9 +629,8 @@ protected:
* Every received block is assigned a unique and increasing identifier, so we
* know which one to give priority in case of a fork.
*/
RecursiveMutex cs_nBlockSequenceId;
/** Blocks loaded from disk are assigned id 0, so start the counter at 1. */
int32_t nBlockSequenceId = 1;
int32_t nBlockSequenceId GUARDED_BY(::cs_main) = 1;
/** Decreasing counter (used by subsequent preciousblock calls). */
int32_t nBlockReverseSequenceId = -1;
/** chainwork for the last block that preciousblock has been applied to. */
@ -828,7 +827,7 @@ public:
void PruneBlockIndexCandidates();
void UnloadBlockIndex();
void UnloadBlockIndex() EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
/** Check whether we are doing an initial block download (synchronizing from disk or network) */
bool IsInitialBlockDownload() const;