fix: change logic to wait root node at waiting list for

project-tsurugi/tsurugi-issues#438

src/concurrency_control/ongoing_tx.cpp

@@ -16,18 +16,35 @@ bool ongoing_tx::exist_id(std::size_t id) {
 
 Status ongoing_tx::waiting_bypass(session* ti) {
     // @pre shared lock to tx_info_
+
+    auto exist_living_wait_for = [](session* target_ti) {
+        auto wait_for{target_ti->extract_wait_for()};
+        for (auto&& elem : tx_info_) {
+            auto the_tx_id = std::get<ongoing_tx::index_id>(elem);
+            auto f_itr = wait_for.find(the_tx_id);
+            if (f_itr != wait_for.end()) { return true; }
+        }
+        return false;
+    };
+
     /**
-     * 現時点で前置候補の LTX群。これらで走行中のものをバイパスする。
+     * 現時点で前置候補の LTX群。これらで走行中のものをルート以外バイパスする。
     */
     auto wait_for{ti->extract_wait_for()};
-
     std::set<std::tuple<std::size_t, session*>> bypass_target{};
     for (auto&& elem : tx_info_) {
         auto the_tx_id = std::get<ongoing_tx::index_id>(elem);
         auto f_itr = wait_for.find(the_tx_id);
         if (f_itr != wait_for.end()) {
             // found
             auto* token = std::get<ongoing_tx::index_session>(elem);
+
+            // check exist living wait for, for not to remove path to root.
+            if (!exist_living_wait_for(token)) {
+                // not bypass for tree root
+                continue;
+            }
+
             bypass_target.insert(std::make_tuple(the_tx_id, token));
             // set valid epoch if need
             if (ti->get_valid_epoch() > token->get_valid_epoch()) {
@@ -168,14 +185,18 @@ bool ongoing_tx::exist_wait_for(session* ti, Status& out_status) {
                         wait_for.end()) {
                         // wait_for hit.
                         /**
-                     * boundary wait 確定.
-                     * waiting by pass: 自分が（前置するかもしれなくて）待つ相手x1
-                     * に対する前置を確定するとともに、x1 が前置する相手に前置する。
-                     * これは待ち確認のたびにパスを一つ短絡化するため、
-                     * get_requested_commit() の確認を噛ませていない。
-                     * */
-                        out_status = waiting_bypass(ti);
-                        return out_status == Status::OK;
+                         * boundary wait 確定.
+                         * waiting by pass: 自分が（前置するかもしれなくて）待つ相手x1
+                         * に対する前置を確定するとともに、x1 が前置する相手に前置する。
+                         * これは待ち確認のたびにパスを一つ短絡化するため、
+                         * get_requested_commit() の確認を噛ませていない。
+                         * https://github.com/project-tsurugi/tsurugi-issues/issues/438#issuecomment-1839876140
+                         * ルートになるまでパスを縮めてはいけない。
+                         */
+                        if (wait_for.size() > 2) {
+                            out_status = waiting_bypass(ti);
+                        }
+                        return true;
                     }
                 } else {
                     // considering for only high priori ltx

test/concurrency_control/complicated/tsurugi_issue438_4_test.cpp

@@ -50,6 +50,8 @@ TEST_F(tsurugi_issue438_4_test, simple) {
     ASSERT_OK(tx_begin({t, transaction_type::SHORT}));
     ASSERT_OK(insert(t, current_batch, "1", "1"));
     ASSERT_OK(commit(t));
+
+    // tx2
     ASSERT_OK(tx_begin({t, transaction_type::LONG, {receipts}}));
     wait_epoch_update();
     ScanHandle shd{};
@@ -63,6 +65,7 @@ TEST_F(tsurugi_issue438_4_test, simple) {
     ASSERT_EQ(Status::WARN_SCAN_LIMIT, next(t, shd));
     ASSERT_OK(close_scan(t, shd));
 
+    // tx3
     Token t2;
     ASSERT_OK(enter(t2));
     ASSERT_OK(tx_begin({t2, transaction_type::SHORT}));
@@ -83,6 +86,7 @@ TEST_F(tsurugi_issue438_4_test, simple) {
     ASSERT_OK(close_scan(t2, shd2));
     ASSERT_OK(commit(t2));
 
+    // tx1
     Token t3;
     ASSERT_OK(enter(t3));
     ASSERT_OK(tx_begin({t3, transaction_type::LONG}));
@@ -93,7 +97,7 @@ TEST_F(tsurugi_issue438_4_test, simple) {
     ASSERT_OK(read_key_from_scan(t3, shd3, buf));
     ASSERT_EQ(buf, "1");
     ASSERT_OK(read_value_from_scan(t3, shd3, buf));
-    ASSERT_EQ(buf, "2");
+    ASSERT_EQ(buf, "2"); // read tx3
     ASSERT_EQ(Status::WARN_SCAN_LIMIT, next(t3, shd3));
     ASSERT_OK(close_scan(t3, shd3));
     ASSERT_EQ(Status::WARN_NOT_FOUND,
@@ -113,11 +117,17 @@ TEST_F(tsurugi_issue438_4_test, simple) {
      * expect waiting at once, but at becoming waiting, tx tries to waiting
      * bypass and bypass t1, and not wait
     */
-    ASSERT_TRUE(commit(t3, cb));
+    ASSERT_FALSE(commit(t3, cb));
+    /**
+     * This needs for t3 aborts but it didn't exist at
+     * https://github.com/project-tsurugi/tsurugi-issues/issues/438#issuecomment-1835644560
+    */
+    ASSERT_OK(insert(t, receipts, "2", "200"));
+    ASSERT_OK(commit(t)); // this needs to release waiting of t3
+    // note: this fits tsurugi issue 5 ex 3 but not fit for trace log
     while (!was_called) { _mm_pause(); }
     ASSERT_EQ(Status::ERR_CC, cb_rc); // expect error due to rub violation
     ASSERT_EQ(reason_code::CC_LTX_READ_UPPER_BOUND_VIOLATION, rc);
-    ASSERT_OK(abort(t));
 
     ASSERT_OK(leave(t));
     ASSERT_OK(leave(t2));