Return to original stage after mysql_lock_tables

Stage "Filling schema table" is now properly shown in 'show processlist'


mysys/mf_keycache.c:
  Simple cleanup with more comments
sql/lock.cc:
  Return to original stage after mysql_lock_tables
  Made 'Table lock' as a true stage
sql/sql_show.cc:
  Restore original stage after get_schema_tables_result

mysys/mf_keycache.c

@@ -1023,8 +1023,8 @@ static void link_into_queue(KEYCACHE_WQUEUE *wqueue,
                             struct st_my_thread_var *thread)
 {
   struct st_my_thread_var *last;
-
   DBUG_ASSERT(!thread->next && !thread->prev);
+
   if (! (last= wqueue->last_thread))
   {
     /* Queue is empty */
@@ -1033,9 +1033,14 @@ static void link_into_queue(KEYCACHE_WQUEUE *wqueue,
   }
   else
   {
+    DBUG_ASSERT(last->next->prev == &last->next);
+    /* Add backlink to previous element */
     thread->prev=      last->next->prev;
+    /* Fix first in list to point backwords to current */
     last->next->prev=  &thread->next;
+    /* Next should point to the first element in list */
     thread->next=      last->next;
+    /* Fix old element to point to new one */
     last->next=        thread;
   }
   wqueue->last_thread= thread;
@@ -1061,13 +1066,18 @@ static void unlink_from_queue(KEYCACHE_WQUEUE *wqueue,
 {
   KEYCACHE_DBUG_PRINT("unlink_from_queue", ("thread %ld", thread->id));
   DBUG_ASSERT(thread->next && thread->prev);
+
   if (thread->next == thread)
+  {
     /* The queue contains only one member */
     wqueue->last_thread= NULL;
+  }
   else
   {
+    /* Remove current element from list */
     thread->next->prev= thread->prev;
-    *thread->prev=thread->next;
+    *thread->prev=      thread->next;
+    /* If first element, change list pointer to point to previous element */
     if (wqueue->last_thread == thread)
       wqueue->last_thread= STRUCT_PTR(struct st_my_thread_var, next,
                                       thread->prev);
@@ -1111,10 +1121,10 @@ static void wait_on_queue(KEYCACHE_WQUEUE *wqueue,
 {
   struct st_my_thread_var *last;
   struct st_my_thread_var *thread= my_thread_var;
-
-  /* Add to queue. */
   DBUG_ASSERT(!thread->next);
   DBUG_ASSERT(!thread->prev); /* Not required, but must be true anyway. */
+
+  /* Add to queue. */
   if (! (last= wqueue->last_thread))
     thread->next= thread;
   else
@@ -1125,7 +1135,7 @@ static void wait_on_queue(KEYCACHE_WQUEUE *wqueue,
   wqueue->last_thread= thread;
 
   /*
-    Wait until thread is removed from queue by the signalling thread.
+    Wait until thread is removed from queue by the signaling thread.
     The loop protects against stray signals.
   */
   do
@@ -1163,10 +1173,11 @@ static void release_whole_queue(KEYCACHE_WQUEUE *wqueue)
   if (!(last= wqueue->last_thread))
     return;
 
-  next= last->next;
+  next= last->next;                             /* First (oldest) element */
   do
   {
     thread=next;
+    DBUG_ASSERT(thread);
     KEYCACHE_DBUG_PRINT("release_whole_queue: signal",
                         ("thread %ld", thread->id));
     /* Signal the thread. */

sql/lock.cc

@@ -301,15 +301,16 @@ bool mysql_lock_tables(THD *thd, MYSQL_LOCK *sql_lock, uint flags)
   int rc= 1;
   ulong timeout= (flags & MYSQL_LOCK_IGNORE_TIMEOUT) ?
     LONG_TIMEOUT : thd->variables.lock_wait_timeout;
-
+  PSI_stage_info org_stage;
   DBUG_ENTER("mysql_lock_tables(sql_lock)");
 
-  THD_STAGE_INFO(thd, stage_system_lock);
+  thd->enter_stage(&stage_system_lock, &org_stage, __func__, __FILE__,
+                   __LINE__);
   if (sql_lock->table_count && lock_external(thd, sql_lock->table,
                                              sql_lock->table_count))
     goto end;
 
-  thd_proc_info(thd, "Table lock");
+  THD_STAGE_INFO(thd, stage_table_lock);
 
   /* Copy the lock data array. thr_multi_lock() reorders its contents. */
   memmove(sql_lock->locks + sql_lock->lock_count, sql_lock->locks,
@@ -323,7 +324,7 @@ bool mysql_lock_tables(THD *thd, MYSQL_LOCK *sql_lock, uint flags)
     (void) unlock_external(thd, sql_lock->table, sql_lock->table_count);
 
 end:
-  THD_STAGE_INFO(thd, stage_after_table_lock);
+  THD_STAGE_INFO(thd, org_stage);
 
   if (thd->killed)
   {

sql/mysqld.cc

@@ -9458,6 +9458,8 @@ PSI_stage_info stage_sql_thd_waiting_until_delay= { 0, "Waiting until MASTER_DEL
 PSI_stage_info stage_storing_result_in_query_cache= { 0, "storing result in query cache", 0};
 PSI_stage_info stage_storing_row_into_queue= { 0, "storing row into queue", 0};
 PSI_stage_info stage_system_lock= { 0, "System lock", 0};
+PSI_stage_info stage_table_lock= { 0, "Table lock", 0};
+PSI_stage_info stage_filling_schema_table= { 0, "Filling schema table", 0};
 PSI_stage_info stage_update= { 0, "update", 0};
 PSI_stage_info stage_updating= { 0, "updating", 0};
 PSI_stage_info stage_updating_main_table= { 0, "updating main table", 0};
@@ -9591,6 +9593,8 @@ PSI_stage_info *all_server_stages[]=
   & stage_storing_result_in_query_cache,
   & stage_storing_row_into_queue,
   & stage_system_lock,
+  & stage_table_lock,
+  & stage_filling_schema_table,
   & stage_update,
   & stage_updating,
   & stage_updating_main_table,

sql/mysqld.h

@@ -413,6 +413,8 @@ extern PSI_stage_info stage_statistics;
 extern PSI_stage_info stage_storing_result_in_query_cache;
 extern PSI_stage_info stage_storing_row_into_queue;
 extern PSI_stage_info stage_system_lock;
+extern PSI_stage_info stage_table_lock;
+extern PSI_stage_info stage_filling_schema_table;
 extern PSI_stage_info stage_update;
 extern PSI_stage_info stage_updating;
 extern PSI_stage_info stage_updating_main_table;

sql/sql_show.cc

@@ -8081,12 +8081,13 @@ bool get_schema_tables_result(JOIN *join,
   THD *thd= join->thd;
   LEX *lex= thd->lex;
   bool result= 0;
-  const char *old_proc_info;
+  PSI_stage_info org_stage;
   DBUG_ENTER("get_schema_tables_result");
 
   Warnings_only_error_handler err_handler;
   thd->push_internal_handler(&err_handler);
-  old_proc_info= thd_proc_info(thd, "Filling schema table");
+  thd->enter_stage(&stage_filling_schema_table, &org_stage, __func__, __FILE__,
+                   __LINE__);
   
   JOIN_TAB *tab;
   for (tab= first_linear_tab(join, WITHOUT_BUSH_ROOTS, WITH_CONST_TABLES);
@@ -8190,7 +8191,7 @@ bool get_schema_tables_result(JOIN *join,
   }
   else if (result)
     my_error(ER_UNKNOWN_ERROR, MYF(0));
-  thd_proc_info(thd, old_proc_info);
+  THD_STAGE_INFO(thd, org_stage);
   DBUG_RETURN(result);
 }