MDEV-4506, parallel replication.

Some after-review fixes.

sql/log.h

@@ -540,7 +540,7 @@ class MYSQL_BIN_LOG: public TC_LOG, private MYSQL_LOG
   void do_checkpoint_request(ulong binlog_id);
   void purge();
   int write_transaction_or_stmt(group_commit_entry *entry, uint64 commit_id);
-  bool queue_for_group_commit(group_commit_entry *entry, wait_for_commit *wfc);
+  bool queue_for_group_commit(group_commit_entry *entry);
   bool write_transaction_to_binlog_events(group_commit_entry *entry);
   void trx_group_commit_leader(group_commit_entry *leader);
   bool is_xidlist_idle_nolock();

sql/log_event.h

@@ -1317,7 +1317,7 @@ class Log_event
 
      @see do_apply_event
    */
-  int apply_event(struct rpl_group_info *rgi)
+  int apply_event(rpl_group_info *rgi)
   {
     return do_apply_event(rgi);
   }
@@ -1331,7 +1331,7 @@ class Log_event
 
      @see do_update_pos
    */
-  int update_pos(struct rpl_group_info *rgi)
+  int update_pos(rpl_group_info *rgi)
   {
     return do_update_pos(rgi);
   }
@@ -1432,7 +1432,7 @@ class Log_event
     @retval 0     Event applied successfully
     @retval errno Error code if event application failed
   */
-  virtual int do_apply_event(struct rpl_group_info *rgi)
+  virtual int do_apply_event(rpl_group_info *rgi)
   {
     return 0;                /* Default implementation does nothing */
   }
@@ -1461,7 +1461,7 @@ class Log_event
                    1). Observe that handler errors are returned by the
                    do_apply_event() function, and not by this one.
    */
-  virtual int do_update_pos(struct rpl_group_info *rgi);
+  virtual int do_update_pos(rpl_group_info *rgi);
 
 
   /**
@@ -1986,10 +1986,10 @@ class Query_log_event: public Log_event
 public:        /* !!! Public in this patch to allow old usage */
 #if defined(MYSQL_SERVER) && defined(HAVE_REPLICATION)
   virtual enum_skip_reason do_shall_skip(Relay_log_info *rli);
-  virtual int do_apply_event(struct rpl_group_info *rgi);
-  virtual int do_update_pos(struct rpl_group_info *rgi);
+  virtual int do_apply_event(rpl_group_info *rgi);
+  virtual int do_update_pos(rpl_group_info *rgi);
 
-  int do_apply_event(struct rpl_group_info *rgi,
+  int do_apply_event(rpl_group_info *rgi,
                        const char *query_arg,
                        uint32 q_len_arg);
   static bool peek_is_commit_rollback(const char *event_start,
@@ -2103,7 +2103,7 @@ class Slave_log_event: public Log_event
 
 private:
 #if defined(MYSQL_SERVER) && defined(HAVE_REPLICATION)
-  virtual int do_apply_event(struct rpl_group_info *rgi);
+  virtual int do_apply_event(rpl_group_info *rgi);
 #endif
 };
 
@@ -2416,12 +2416,12 @@ class Load_log_event: public Log_event
 
 public:        /* !!! Public in this patch to allow old usage */
 #if defined(MYSQL_SERVER) && defined(HAVE_REPLICATION)
-  virtual int do_apply_event(struct rpl_group_info *rgi)
+  virtual int do_apply_event(rpl_group_info *rgi)
   {
     return do_apply_event(thd->slave_net,rgi,0);
   }
 
-  int do_apply_event(NET *net, struct rpl_group_info *rgi,
+  int do_apply_event(NET *net, rpl_group_info *rgi,
                      bool use_rli_only_for_errors);
 #endif
 };
@@ -2500,7 +2500,7 @@ class Start_log_event_v3: public Log_event
 
 protected:
 #if defined(MYSQL_SERVER) && defined(HAVE_REPLICATION)
-  virtual int do_apply_event(struct rpl_group_info *rgi);
+  virtual int do_apply_event(rpl_group_info *rgi);
   virtual enum_skip_reason do_shall_skip(Relay_log_info*)
   {
     /*
@@ -2596,8 +2596,8 @@ class Format_description_log_event: public Start_log_event_v3
   static bool is_version_before_checksum(const master_version_split *version_split);
 protected:
 #if defined(MYSQL_SERVER) && defined(HAVE_REPLICATION)
-  virtual int do_apply_event(struct rpl_group_info *rgi);
-  virtual int do_update_pos(struct rpl_group_info *rgi);
+  virtual int do_apply_event(rpl_group_info *rgi);
+  virtual int do_update_pos(rpl_group_info *rgi);
   virtual enum_skip_reason do_shall_skip(Relay_log_info *rli);
 #endif
 };
@@ -2675,8 +2675,8 @@ Intvar_log_event(THD* thd_arg,uchar type_arg, ulonglong val_arg,
 
 private:
 #if defined(MYSQL_SERVER) && defined(HAVE_REPLICATION)
-  virtual int do_apply_event(struct rpl_group_info *rgi);
-  virtual int do_update_pos(struct rpl_group_info *rgi);
+  virtual int do_apply_event(rpl_group_info *rgi);
+  virtual int do_update_pos(rpl_group_info *rgi);
   virtual enum_skip_reason do_shall_skip(Relay_log_info *rli);
 #endif
 };
@@ -2754,8 +2754,8 @@ class Rand_log_event: public Log_event
 
 private:
 #if defined(MYSQL_SERVER) && defined(HAVE_REPLICATION)
-  virtual int do_apply_event(struct rpl_group_info *rgi);
-  virtual int do_update_pos(struct rpl_group_info *rgi);
+  virtual int do_apply_event(rpl_group_info *rgi);
+  virtual int do_update_pos(rpl_group_info *rgi);
   virtual enum_skip_reason do_shall_skip(Relay_log_info *rli);
 #endif
 };
@@ -2803,7 +2803,7 @@ class Xid_log_event: public Log_event
 
 private:
 #if defined(MYSQL_SERVER) && defined(HAVE_REPLICATION)
-  virtual int do_apply_event(struct rpl_group_info *rgi);
+  virtual int do_apply_event(rpl_group_info *rgi);
   enum_skip_reason do_shall_skip(Relay_log_info *rli);
 #endif
 };
@@ -2870,8 +2870,8 @@ class User_var_log_event: public Log_event
 
 private:
 #if defined(MYSQL_SERVER) && defined(HAVE_REPLICATION)
-  virtual int do_apply_event(struct rpl_group_info *rgi);
-  virtual int do_update_pos(struct rpl_group_info *rgi);
+  virtual int do_apply_event(rpl_group_info *rgi);
+  virtual int do_update_pos(rpl_group_info *rgi);
   virtual enum_skip_reason do_shall_skip(Relay_log_info *rli);
 #endif
 };
@@ -2905,7 +2905,7 @@ class Stop_log_event: public Log_event
 
 private:
 #if defined(MYSQL_SERVER) && defined(HAVE_REPLICATION)
-  virtual int do_update_pos(struct rpl_group_info *rgi);
+  virtual int do_update_pos(rpl_group_info *rgi);
   virtual enum_skip_reason do_shall_skip(Relay_log_info *rli)
   {
     /*
@@ -3007,7 +3007,7 @@ class Rotate_log_event: public Log_event
 
 private:
 #if defined(MYSQL_SERVER) && defined(HAVE_REPLICATION)
-  virtual int do_update_pos(struct rpl_group_info *rgi);
+  virtual int do_update_pos(rpl_group_info *rgi);
   virtual enum_skip_reason do_shall_skip(Relay_log_info *rli);
 #endif
 };
@@ -3119,8 +3119,8 @@ class Gtid_log_event: public Log_event
                  uint16 flags, bool is_transactional, uint64 commit_id);
 #ifdef HAVE_REPLICATION
   void pack_info(THD *thd, Protocol *protocol);
-  virtual int do_apply_event(struct rpl_group_info *rgi);
-  virtual int do_update_pos(struct rpl_group_info *rgi);
+  virtual int do_apply_event(rpl_group_info *rgi);
+  virtual int do_update_pos(rpl_group_info *rgi);
   virtual enum_skip_reason do_shall_skip(Relay_log_info *rli);
 #endif
 #else
@@ -3249,7 +3249,7 @@ class Gtid_list_log_event: public Log_event
 #if defined(MYSQL_SERVER) && defined(HAVE_REPLICATION)
   bool to_packet(String *packet);
   bool write(IO_CACHE *file);
-  virtual int do_apply_event(struct rpl_group_info *rgi);
+  virtual int do_apply_event(rpl_group_info *rgi);
 #endif
   static bool peek(const char *event_start, uint32 event_len,
                    uint8 checksum_alg,
@@ -3328,7 +3328,7 @@ class Create_file_log_event: public Load_log_event
 
 private:
 #if defined(MYSQL_SERVER) && defined(HAVE_REPLICATION)
-  virtual int do_apply_event(struct rpl_group_info *rgi);
+  virtual int do_apply_event(rpl_group_info *rgi);
 #endif
 };
 
@@ -3383,7 +3383,7 @@ class Append_block_log_event: public Log_event
 
 private:
 #if defined(MYSQL_SERVER) && defined(HAVE_REPLICATION)
-  virtual int do_apply_event(struct rpl_group_info *rgi);
+  virtual int do_apply_event(rpl_group_info *rgi);
 #endif
 };
 
@@ -3424,7 +3424,7 @@ class Delete_file_log_event: public Log_event
 
 private:
 #if defined(MYSQL_SERVER) && defined(HAVE_REPLICATION)
-  virtual int do_apply_event(struct rpl_group_info *rgi);
+  virtual int do_apply_event(rpl_group_info *rgi);
 #endif
 };
 
@@ -3464,7 +3464,7 @@ class Execute_load_log_event: public Log_event
 
 private:
 #if defined(MYSQL_SERVER) && defined(HAVE_REPLICATION)
-  virtual int do_apply_event(struct rpl_group_info *rgi);
+  virtual int do_apply_event(rpl_group_info *rgi);
 #endif
 };
 
@@ -3563,7 +3563,7 @@ class Execute_load_query_log_event: public Query_log_event
 
 private:
 #if defined(MYSQL_SERVER) && defined(HAVE_REPLICATION)
-  virtual int do_apply_event(struct rpl_group_info *rgi);
+  virtual int do_apply_event(rpl_group_info *rgi);
 #endif
 };
 
@@ -3635,8 +3635,8 @@ class Annotate_rows_log_event: public Log_event
 
 #if !defined(MYSQL_CLIENT) && defined(HAVE_REPLICATION)
 private:
-  virtual int do_apply_event(struct rpl_group_info *rgi);
-  virtual int do_update_pos(struct rpl_group_info *rgi);
+  virtual int do_apply_event(rpl_group_info *rgi);
+  virtual int do_update_pos(rpl_group_info *rgi);
   virtual enum_skip_reason do_shall_skip(Relay_log_info*);
 #endif
 
@@ -4050,8 +4050,8 @@ class Table_map_log_event : public Log_event
 
 private:
 #if defined(MYSQL_SERVER) && defined(HAVE_REPLICATION)
-  virtual int do_apply_event(struct rpl_group_info *rgi);
-  virtual int do_update_pos(struct rpl_group_info *rgi);
+  virtual int do_apply_event(rpl_group_info *rgi);
+  virtual int do_update_pos(rpl_group_info *rgi);
   virtual enum_skip_reason do_shall_skip(Relay_log_info *rli);
 #endif
 
@@ -4278,8 +4278,8 @@ class Rows_log_event : public Log_event
 private:
 
 #if defined(MYSQL_SERVER) && defined(HAVE_REPLICATION)
-  virtual int do_apply_event(struct rpl_group_info *rgi);
-  virtual int do_update_pos(struct rpl_group_info *rgi);
+  virtual int do_apply_event(rpl_group_info *rgi);
+  virtual int do_update_pos(rpl_group_info *rgi);
   virtual enum_skip_reason do_shall_skip(Relay_log_info *rli);
 
   /*
@@ -4612,7 +4612,7 @@ class Incident_log_event : public Log_event {
 #endif
 
 #if defined(MYSQL_SERVER) && defined(HAVE_REPLICATION)
-  virtual int do_apply_event(struct rpl_group_info *rgi);
+  virtual int do_apply_event(rpl_group_info *rgi);
 #endif
 
   virtual bool write_data_header(IO_CACHE *file);

sql/log_event_old.cc

@@ -36,7 +36,7 @@
 
 // Old implementation of do_apply_event()
 int 
-Old_rows_log_event::do_apply_event(Old_rows_log_event *ev, struct rpl_group_info *rgi)
+Old_rows_log_event::do_apply_event(Old_rows_log_event *ev, rpl_group_info *rgi)
 {
   DBUG_ENTER("Old_rows_log_event::do_apply_event(st_relay_log_info*)");
   int error= 0;
@@ -1451,7 +1451,7 @@ int Old_rows_log_event::do_add_row_data(uchar *row_data, size_t length)
 
 
 #if !defined(MYSQL_CLIENT) && defined(HAVE_REPLICATION)
-int Old_rows_log_event::do_apply_event(struct rpl_group_info *rgi)
+int Old_rows_log_event::do_apply_event(rpl_group_info *rgi)
 {
   DBUG_ENTER("Old_rows_log_event::do_apply_event(Relay_log_info*)");
   int error= 0;
@@ -1834,7 +1834,7 @@ Old_rows_log_event::do_shall_skip(Relay_log_info *rli)
 }
 
 int
-Old_rows_log_event::do_update_pos(struct rpl_group_info *rgi)
+Old_rows_log_event::do_update_pos(rpl_group_info *rgi)
 {
   Relay_log_info *rli= rgi->rli;
   DBUG_ENTER("Old_rows_log_event::do_update_pos");

sql/log_event_old.h

@@ -214,8 +214,8 @@ class Old_rows_log_event : public Log_event
 private:
 
 #if !defined(MYSQL_CLIENT) && defined(HAVE_REPLICATION)
-  virtual int do_apply_event(struct rpl_group_info *rgi);
-  virtual int do_update_pos(struct rpl_group_info *rgi);
+  virtual int do_apply_event(rpl_group_info *rgi);
+  virtual int do_update_pos(rpl_group_info *rgi);
   virtual enum_skip_reason do_shall_skip(Relay_log_info *rli);
 
   /*
@@ -275,7 +275,7 @@ class Old_rows_log_event : public Log_event
   
 #if !defined(MYSQL_CLIENT) && defined(HAVE_REPLICATION)
 
-  int do_apply_event(Old_rows_log_event*, struct rpl_group_info *rgi);
+  int do_apply_event(Old_rows_log_event*, rpl_group_info *rgi);
 
   /*
     Primitive to prepare for a sequence of row executions.
@@ -403,7 +403,7 @@ class Write_rows_log_event_old : public Old_rows_log_event
 
 #if !defined(MYSQL_CLIENT) && defined(HAVE_REPLICATION)
   // use old definition of do_apply_event()
-  virtual int do_apply_event(struct rpl_group_info *rgi)
+  virtual int do_apply_event(rpl_group_info *rgi)
   { return Old_rows_log_event::do_apply_event(this, rgi); }
 
   // primitives for old version of do_apply_event()
@@ -481,7 +481,7 @@ class Update_rows_log_event_old : public Old_rows_log_event
 
 #if !defined(MYSQL_CLIENT) && defined(HAVE_REPLICATION)
   // use old definition of do_apply_event()
-  virtual int do_apply_event(struct rpl_group_info *rgi)
+  virtual int do_apply_event(rpl_group_info *rgi)
   { return Old_rows_log_event::do_apply_event(this, rgi); }
 
   // primitives for old version of do_apply_event()
@@ -556,7 +556,7 @@ class Delete_rows_log_event_old : public Old_rows_log_event
 
 #if !defined(MYSQL_CLIENT) && defined(HAVE_REPLICATION)
   // use old definition of do_apply_event()
-  virtual int do_apply_event(struct rpl_group_info *rgi)
+  virtual int do_apply_event(rpl_group_info *rgi)
   { return Old_rows_log_event::do_apply_event(this, rgi); }
 
   // primitives for old version of do_apply_event()

sql/rpl_gtid.cc

@@ -62,7 +62,7 @@ rpl_slave_state::update_state_hash(uint64 sub_id, rpl_gtid *gtid)
 
 
 int
-rpl_slave_state::record_and_update_gtid(THD *thd, struct rpl_group_info *rgi)
+rpl_slave_state::record_and_update_gtid(THD *thd, rpl_group_info *rgi)
 {
   uint64 sub_id;
 

sql/rpl_parallel.cc

@@ -62,7 +62,7 @@ rpt_handle_event(rpl_parallel_thread::queued_event *qev,
                  struct rpl_parallel_thread *rpt)
 {
   int err;
-  struct rpl_group_info *rgi= qev->rgi;
+  rpl_group_info *rgi= qev->rgi;
   Relay_log_info *rli= rgi->rli;
   THD *thd= rgi->thd;
 
@@ -128,8 +128,9 @@ handle_rpl_parallel_thread(void *arg)
     old_msg= thd->proc_info;
     thd->enter_cond(&rpt->COND_rpl_thread, &rpt->LOCK_rpl_thread,
                     "Waiting for work from SQL thread");
-    while (!rpt->stop && !thd->killed && !(events= rpt->event_queue))
+    while (!(events= rpt->event_queue) && !rpt->stop && !thd->killed)
       mysql_cond_wait(&rpt->COND_rpl_thread, &rpt->LOCK_rpl_thread);
+    /* Mark that this thread is now executing */
     rpt->free= false;
     rpt->event_queue= rpt->last_in_queue= NULL;
     thd->exit_cond(old_msg);
@@ -145,9 +146,15 @@ handle_rpl_parallel_thread(void *arg)
       uint64 wait_start_sub_id;
       bool end_of_group;
 
+      /* Handle a new event group, which will be initiated by a GTID event. */
       if (event_type == GTID_EVENT)
       {
         in_event_group= true;
+        /*
+          If the standalone flag is set, then this event group consists of a
+          single statement (possibly preceeded by some Intvar_log_event and
+          similar), without any terminating COMMIT/ROLLBACK/XID.
+        */
         group_standalone=
           (0 != (static_cast<Gtid_log_event *>(events->ev)->flags2 &
                  Gtid_log_event::FL_STANDALONE));
@@ -540,12 +547,12 @@ rpl_parallel::wait_for_done()
 
 
 bool
-rpl_parallel::do_event(struct rpl_group_info *serial_rgi, Log_event *ev)
+rpl_parallel::do_event(rpl_group_info *serial_rgi, Log_event *ev)
 {
   rpl_parallel_entry *e;
   rpl_parallel_thread *cur_thread;
   rpl_parallel_thread::queued_event *qev;
-  struct rpl_group_info *rgi;
+  rpl_group_info *rgi;
   Relay_log_info *rli= serial_rgi->rli;
   enum Log_event_type typ;
 

sql/rpl_parallel.h

@@ -23,7 +23,7 @@ struct rpl_parallel_thread {
   struct queued_event {
     queued_event *next;
     Log_event *ev;
-    struct rpl_group_info *rgi;
+    rpl_group_info *rgi;
   } *event_queue, *last_in_queue;
 };
 
@@ -59,7 +59,7 @@ struct rpl_parallel_entry {
   mysql_mutex_t LOCK_parallel_entry;
   mysql_cond_t COND_parallel_entry;
   uint64 current_sub_id;
-  struct rpl_group_info *current_group_info;
+  rpl_group_info *current_group_info;
   /*
     The sub_id of the last event group in the previous batch of group-committed
     transactions.
@@ -78,7 +78,7 @@ struct rpl_parallel {
   ~rpl_parallel();
   rpl_parallel_entry *find(uint32 domain_id);
   void wait_for_done();
-  bool do_event(struct rpl_group_info *serial_rgi, Log_event *ev);
+  bool do_event(rpl_group_info *serial_rgi, Log_event *ev);
 };
 
 

sql/rpl_rli.cc

@@ -1193,7 +1193,7 @@ bool Relay_log_info::cached_charset_compare(char *charset) const
 
 void Relay_log_info::stmt_done(my_off_t event_master_log_pos,
                                time_t event_creation_time, THD *thd,
-                               struct rpl_group_info *rgi)
+                               rpl_group_info *rgi)
 {
 #ifndef DBUG_OFF
   extern uint debug_not_change_ts_if_art_event;
@@ -1265,6 +1265,11 @@ void Relay_log_info::cleanup_context(THD *thd, bool error)
 {
   DBUG_ENTER("Relay_log_info::cleanup_context");
 
+  /*
+    In parallel replication, different THDs can be used from different
+    parallel threads. But in single-threaded mode, only the THD of the main
+    SQL thread is allowed.
+  */
   DBUG_ASSERT(opt_slave_parallel_threads > 0 || sql_thd == thd);
   /*
     1) Instances of Table_map_log_event, if ::do_apply_event() was called on them,
@@ -1552,6 +1557,7 @@ event_group_new_gtid(rpl_group_info *rgi, Gtid_log_event *gev)
   uint64 sub_id= rpl_global_gtid_slave_state.next_subid(gev->domain_id);
   if (!sub_id)
   {
+    /* Out of memory caused hash insertion to fail. */
     return 1;
   }
   rgi->gtid_sub_id= sub_id;

sql/rpl_rli.h

@@ -422,7 +422,7 @@ class Relay_log_info : public Slave_reporting_capability
   */
   void stmt_done(my_off_t event_log_pos,
                  time_t event_creation_time, THD *thd,
-                 struct rpl_group_info *rgi);
+                 rpl_group_info *rgi);
 
 
   /**
@@ -521,10 +521,14 @@ class Relay_log_info : public Slave_reporting_capability
 
 /*
   This is data for various state needed to be kept for the processing of
-  one event group in the SQL thread.
+  one event group (transaction) during replication.
 
-  For single-threaded replication it is linked from the RLI, for parallel
-  replication it is linked into each event group being executed in parallel.
+  In single-threaded replication, there will be one global rpl_group_info and
+  one global Relay_log_info per master connection. They will be linked
+  together.
+
+  In parallel replication, there will be one rpl_group_info object for
+  each running thd. All rpl_group_info will share the same Relay_log_info.
 */
 struct rpl_group_info
 {
@@ -555,7 +559,7 @@ struct rpl_group_info
     for the wrong commit).
   */
   uint64 wait_commit_sub_id;
-  struct rpl_group_info *wait_commit_group_info;
+  rpl_group_info *wait_commit_group_info;
   /*
     If non-zero, the event group must wait for this sub_id to be committed
     before the execution of the event group is allowed to start.

sql/rpl_utility.cc

@@ -1143,7 +1143,7 @@ bool Deferred_log_events::is_empty()
   return array.elements == 0;
 }
 
-bool Deferred_log_events::execute(struct rpl_group_info *rgi)
+bool Deferred_log_events::execute(rpl_group_info *rgi)
 {
   bool res= false;
 

sql/slave.cc

@@ -3019,7 +3019,7 @@ static int has_temporary_error(THD *thd)
   ev->update_pos().
 */
 int apply_event_and_update_pos(Log_event* ev, THD* thd,
-                               struct rpl_group_info *rgi,
+                               rpl_group_info *rgi,
                                rpl_parallel_thread *rpt)
 {
   int exec_res= 0;

sql/sql_binlog.cc

@@ -80,7 +80,7 @@ void mysql_client_binlog_statement(THD* thd)
   my_bool have_fd_event= TRUE;
   int err;
   Relay_log_info *rli;
-  struct rpl_group_info *rgi;
+  rpl_group_info *rgi;
 
   rli= thd->rli_fake;
   if (!rli)

sql/sql_class.cc

@@ -5666,6 +5666,10 @@ wait_for_commit::register_wait_for_prior_commit(wait_for_commit *waitee)
     waiting_for_commit= false;
   else
   {
+    /*
+      Put ourself at the head of the waitee's list of transactions that must
+      wait for it to commit first.
+     */
     this->next_subsequent_commit= waitee->subsequent_commits_list;
     waitee->subsequent_commits_list= this;
   }
@@ -5704,7 +5708,7 @@ wait_for_commit::wait_for_prior_commit2()
 
   The waiter needs to lock the waitee to delete itself from the list in
   unregister_wait_for_prior_commit(). Thus wakeup_subsequent_commits() can not
-  hold its own lock while locking waiters, lest we deadlock.
+  hold its own lock while locking waiters, as this could lead to deadlock.
 
   So we need to prevent unregister_wait_for_prior_commit() running while wakeup
   is in progress - otherwise the unregister could complete before the wakeup,
@@ -5727,6 +5731,7 @@ wait_for_commit::wait_for_prior_commit2()
   would not be woken up until next wakeup, which could be potentially much
   later than necessary.
 */
+
 void
 wait_for_commit::wakeup_subsequent_commits2()
 {

sql/sql_class.h

@@ -1615,7 +1615,7 @@ struct wait_for_commit
   */
   bool waiting_for_commit;
   /*
-    Flag set when wakeup_subsequent_commits_running() is active, see commonts
+    Flag set when wakeup_subsequent_commits_running() is active, see comments
     on that function for details.
   */
   bool wakeup_subsequent_commits_running;