Add lock argument to server_service::background_rollback()

This is to allow implementation to temporarily release the
lock if needed.

Author: temeo

dbsim/db_server_service.cpp

@@ -86,7 +86,8 @@ int db::server_service::start_sst(
     return 0;
 }
 
-void db::server_service::background_rollback(wsrep::client_state&)
+void db::server_service::background_rollback(wsrep::unique_lock<wsrep::mutex>&,
+                                             wsrep::client_state&)
 {
 }
 

dbsim/db_server_service.hpp

@@ -41,7 +41,8 @@ namespace db
         bool sst_before_init() const override;
         int start_sst(const std::string&, const wsrep::gtid&, bool) override;
         std::string sst_request() override;
-        void background_rollback(wsrep::client_state&) override;
+        void background_rollback(wsrep::unique_lock<wsrep::mutex>&,
+                                 wsrep::client_state&) override;
         void bootstrap() override;
         void log_message(enum wsrep::log::level, const char* message) override;
         void log_dummy_write_set(wsrep::client_state&, const wsrep::ws_meta&)

include/wsrep/server_service.hpp

@@ -85,8 +85,14 @@ namespace wsrep
 
         /**
          * Perform a background rollback for a transaction.
+         *
+         * @param lock Lock protecting client state.
+         * @param client_state Client session to do background rollback
+         *        for.
          */
-        virtual void background_rollback(wsrep::client_state&) = 0;
+        virtual void background_rollback(wsrep::unique_lock<wsrep::mutex>& lock,
+                                         wsrep::client_state& client_state)
+            = 0;
 
         /**
          * Bootstrap a DBMS state for a new cluster.

src/transaction.cpp

@@ -1073,7 +1073,7 @@ bool wsrep::transaction::bf_abort(
                 }
             }
 
-            server_service_.background_rollback(client_state_);
+            server_service_.background_rollback(lock, client_state_);
         }
     }
     return ret;

test/mock_client_state.hpp

@@ -49,6 +49,8 @@ namespace wsrep
                 (void)client_service().bf_rollback();
             }
         }
+      void lock() { mutex_.lock(); }
+      void unlock() { mutex_.unlock(); }
     private:
         wsrep::default_mutex mutex_;
         wsrep::default_condition_variable cond_;

test/mock_server_state.hpp

@@ -184,10 +184,13 @@ namespace wsrep
         }
 
         void
-        background_rollback(wsrep::client_state& client_state) WSREP_OVERRIDE
+        background_rollback(wsrep::unique_lock<wsrep::mutex>& lock,
+                            wsrep::client_state& client_state) WSREP_OVERRIDE
         {
+            lock.unlock();
             client_state.before_rollback();
             client_state.after_rollback();
+            lock.lock();
         }
 
         int wait_committing_transactions(int) WSREP_OVERRIDE { return 0; }