a dirty to recreate bitcoin#29767, dace race in my local machine iwit…

…h a probability of around 10%.

src/index/base.cpp

@@ -162,9 +162,10 @@ void BaseIndex::Sync()
             const CBlockIndex* pindex_next = WITH_LOCK(cs_main, return NextSyncBlock(pindex, m_chainstate->m_chain));
             if (!pindex_next) {
                 SetBestBlockIndex(pindex);
+                m_synced = true;
+                m_syned_ = true;
                 // No need to handle errors in Commit. See rationale above.
                 Commit();
-                m_synced = true;
                 break;
             }
             if (pindex_next->pprev != pindex && !Rewind(pindex, pindex_next->pprev)) {

src/index/base.h

@@ -60,6 +60,10 @@ class BaseIndex : public CValidationInterface
         void WriteBestBlock(CDBBatch& batch, const CBlockLocator& locator);
     };
 
+    // Use this variable to make only thread basic block filter index pause, and only pause once
+    // As scheduler may also call Commit(), if pause every call, it will not make race window bigger
+    std::atomic<bool> m_syned_{false};
+
 private:
     /// Whether the index has been initialized or not.
     std::atomic<bool> m_init{false};

src/index/blockfilterindex.cpp

@@ -145,6 +145,12 @@ bool BlockFilterIndex::CustomCommit(CDBBatch& batch)
 {
     const FlatFilePos& pos = m_next_filter_pos;
 
+    if (m_syned_) {
+        // Set it to false, as i only want it to pause once
+        m_syned_ = false;
+        std::this_thread::sleep_for(std::chrono::seconds(5));
+    }
+
     // Flush current filter file to disk.
     AutoFile file{m_filter_fileseq->Open(pos)};
     if (file.IsNull()) {