StorageLog: avoid UB for rwlock unlock due to unlock from another thread

src/Storages/StorageLog.cpp

@@ -357,6 +357,11 @@ void LogBlockOutputStream::writeSuffix()
 
     streams.clear();
     done = true;
+
+    /// unlock should be done from the same thread as lock, and dtor may be
+    /// called from different thread, so it should be done here (at least in
+    /// case of no exceptions occurred)
+    lock.unlock();
 }
 
 

tests/queries/0_stateless/01796_Log_rwlock_ub.sql

@@ -0,0 +1,5 @@
+DROP TABLE IF EXISTS underlying_01796;
+CREATE TABLE underlying_01796 (key UInt64) Engine=Log();
+INSERT INTO FUNCTION remote('127.1', currentDatabase(), underlying_01796) SELECT toUInt64(number) FROM system.numbers LIMIT 1;
+SELECT * FROM underlying_01796 FORMAT Null;
+DROP TABLE underlying_01796;