trx_rollback_recovered(): Add a clarification

1 files changed, 12 insertions, 0 deletions

diff --git a/storage/innobase/trx/trx0roll.cc b/storage/innobase/trx/trx0roll.cc
index 2a2d2c3a315..80f1e76a6c2 100644
--- a/storage/innobase/trx/trx0roll.cc
+++ b/storage/innobase/trx/trx0roll.cc
@@ -828,6 +828,18 @@ void trx_rollback_recovered(bool all)
         ut_ad(!srv_undo_sources);
         ut_ad(srv_fast_shutdown);
 discard:
+        /* Note: before kill_server() invoked innobase_end() via
+        unireg_end(), it invoked close_connections(), which should initiate
+        the rollback of any user transactions via THD::cleanup() in the
+        connection threads, and wait for all THD::cleanup() to complete.
+        So, no active user transactions should exist at this point.
+
+        srv_undo_sources=false was cleared early in innobase_end().
+
+        Because there is no possible race condition with any
+        concurrent user transaction, we do not have to invoke
+        trx->commit_state() or wait for !trx->is_referenced()
+        before trx_sys.deregister_rw(trx). */
         trx_sys.deregister_rw(trx);
         trx_free_at_shutdown(trx);
       }