add 3.6

Signed-off-by: Alex Chi Z <iskyzh@gmail.com>

mini-lsm-starter/src/mvcc.rs

@@ -25,6 +25,7 @@ pub(crate) struct CommittedTxnData {
 
 pub(crate) struct LsmMvccInner {
     pub(crate) write_lock: Mutex<()>,
+    pub(crate) commit_lock: Mutex<()>,
     pub(crate) ts: Arc<Mutex<(u64, Watermark)>>,
     pub(crate) committed_txns: Arc<Mutex<BTreeMap<u64, CommittedTxnData>>>,
 }
@@ -33,6 +34,7 @@ impl LsmMvccInner {
     pub fn new(initial_ts: u64) -> Self {
         Self {
             write_lock: Mutex::new(()),
+            commit_lock: Mutex::new(()),
             ts: Arc::new(Mutex::new((initial_ts, Watermark::new()))),
             committed_txns: Arc::new(Mutex::new(BTreeMap::new())),
         }