fix: concurrency conflict in MemPool.TryRemoveUnVerified

src/Neo/Ledger/MemoryPool.cs

@@ -445,12 +445,20 @@
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         internal bool TryRemoveUnVerified(UInt256 hash, [MaybeNullWhen(false)] out PoolItem? item)
         {
-            if (!_unverifiedTransactions.TryGetValue(hash, out item))
-                return false;
-
-            _unverifiedTransactions.Remove(hash);
-            _unverifiedSortedTransactions.Remove(item);
-            return true;
+            _txRwLock.EnterWriteLock();
+            try
+            {
+                if (!_unverifiedTransactions.TryGetValue(hash, out item))
+                    return false;
+
+                _unverifiedTransactions.Remove(hash);
+                _unverifiedSortedTransactions.Remove(item);
+                return true;
+            }
+            finally
+            {
+                _txRwLock.ExitWriteLock();
+            }
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -481,7 +489,7 @@
                 // No need to modify VerificationContext as it will be reset afterwards.
                 foreach (Transaction tx in block.Transactions)
                 {
-                    if (!TryRemoveVerified(tx.Hash, out _)) TryRemoveUnVerified(tx.Hash, out _);
+                    if (!TryRemoveVerified(tx.Hash, out _)) TryRemoveUnVerifiedLocked(tx.Hash, out _);
                     var conflictingSigners = tx.Signers.Select(s => s.Account);
                     foreach (var h in tx.GetAttributes<Conflicts>().Select(a => a.Hash))
                     {
@@ -509,7 +517,7 @@
                 }
                 foreach (var h in stale)
                 {
-                    if (!TryRemoveVerified(h, out _)) TryRemoveUnVerified(h, out _);
+                    if (!TryRemoveVerified(h, out _)) TryRemoveUnVerifiedLocked(h, out _);
                 }
 
                 // Add all the previously verified transactions back to the unverified transactions and clear mempool conflicts list.

tests/Neo.UnitTests/Ledger/UT_MemoryPool.cs

@@ -747,6 +747,25 @@ public void TestUpdatePoolForBlockPersisted()
             _unit.VerifiedCount.Should().Be(0);
         }
 
+        [TestMethod]
+        public void TestTryRemoveUnVerified()
+        {
+            AddTransactions(32);
+            _unit.SortedTxCount.Should().Be(32);
+
+            var txs = _unit.GetSortedVerifiedTransactions().ToArray();
+            _unit.InvalidateVerifiedTransactions();
+
+            _unit.SortedTxCount.Should().Be(0);
+
+            foreach (var tx in txs)
+            {
+                _unit.TryRemoveUnVerified(tx.Hash, out _);
+            }
+
+            _unit.UnVerifiedCount.Should().Be(0);
+        }
+
         public static StorageKey CreateStorageKey(int id, byte prefix, byte[] key = null)
         {
             byte[] buffer = GC.AllocateUninitializedArray<byte>(sizeof(byte) + (key?.Length ?? 0));