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IsInitialBlockDownload: usually avoid locking

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Optimistically test the latch bool before taking the lock.
For all IsInitialBlockDownload calls after the first to return false,
this avoids the need to lock cs_main.
This commit is contained in:
Kaz Wesley 2016-04-26 17:21:22 -07:00
parent 3b9a0bf41f
commit f0fdda0181
1 changed files with 11 additions and 4 deletions
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15
src/main.cpp
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@ -37,6 +37,7 @@
#include "validationinterface.h"
#include "versionbits.h"
#include <atomic>
#include <sstream>
#include <boost/algorithm/string/replace.hpp>
@ -1574,18 +1575,24 @@ CAmount GetBlockSubsidy(int nHeight, const Consensus::Params& consensusParams)
bool IsInitialBlockDownload()
{
const CChainParams& chainParams = Params();
// Once this function has returned false, it must remain false.
static std::atomic<bool> latchToFalse{false};
// Optimization: pre-test latch before taking the lock.
if (latchToFalse.load(std::memory_order_relaxed))
return false;
LOCK(cs_main);
if (latchToFalse.load(std::memory_order_relaxed))
return false;
if (fImporting || fReindex)
return true;
if (fCheckpointsEnabled && chainActive.Height() < Checkpoints::GetTotalBlocksEstimate(chainParams.Checkpoints()))
return true;
static bool lockIBDState = false;
if (lockIBDState)
return false;
bool state = (chainActive.Height() < pindexBestHeader->nHeight - 24 * 6 ||
std::max(chainActive.Tip()->GetBlockTime(), pindexBestHeader->GetBlockTime()) < GetTime() - nMaxTipAge);
if (!state)
lockIBDState = true;
latchToFalse.store(true, std::memory_order_relaxed);
return state;
}