Bug#25721

  "Concurrent ALTER/CREATE SERVER can lead to deadlock"
  Deadlock caused by inconsistant use of mutexes in sql_server.cc
  One mutex has been removed to resolve deadlock.
  Many functions were made private which should not be exported.
  Unused variables and function removed.


mysql-test/r/federated_server.result:
  Bug 25721 "Concurrent ALTER/CREATE SERVER can lead to deadlock"
  
  New test results
mysql-test/t/federated_server.test:
  Bug 25721 "Concurrent ALTER/CREATE SERVER can lead to deadlock"
  
  Test for bug by using stored procedure. Unpatched server would deadlock frequently.
sql/sql_parse.cc:
  Bug 25721 "Concurrent ALTER/CREATE SERVER can lead to deadlock"
  
  check for correct error code when dropping server
sql/sql_servers.cc:
  Bug 25721 "Concurrent ALTER/CREATE SERVER can lead to deadlock"
  
  Removed unneccessary mutex, only need THR_LOCK_servers rwlock to
  guard data structures against race conditions. Misuse of other mutex
  caused deadlock by inconsistant ordering of mutex lock operations.
  Alter order of some operations to hit memory before disk.
  Removed unused function.
  Removed servers_version and servers_cache_initialised variables.
  Made many internal functions static.
sql/sql_servers.h:
  Bug 25721 "Concurrent ALTER/CREATE SERVER can lead to deadlock"
  
  remove internal functions from being exported.

1 files changed, 158 insertions, 197 deletions

diff --git a/sql/sql_servers.cc b/sql/sql_servers.cc
index 9a5176d9fe3..9b01a1b6889 100644
--- a/sql/sql_servers.cc
+++ b/sql/sql_servers.cc
@@ -25,14 +25,43 @@
 #include "sp_head.h"
 #include "sp.h"
 
-HASH servers_cache;
-pthread_mutex_t servers_cache_mutex;                // To init the hash
-uint servers_cache_initialised=FALSE;
-/* Version of server table. incremented by servers_load */
-static uint servers_version=0;
+/*
+  We only use 1 mutex to guard the data structures - THR_LOCK_servers.
+  Read locked when only reading data and write-locked for all other access.
+*/
+
+static HASH servers_cache;
 static MEM_ROOT mem;
 static rw_lock_t THR_LOCK_servers;
 
+static bool get_server_from_table_to_cache(TABLE *table);
+
+/* insert functions */
+static int insert_server(THD *thd, FOREIGN_SERVER *server_options);
+static int insert_server_record(TABLE *table, FOREIGN_SERVER *server);
+static int insert_server_record_into_cache(FOREIGN_SERVER *server);
+static void prepare_server_struct_for_insert(LEX_SERVER_OPTIONS *server_options,
+                                             FOREIGN_SERVER *server);
+/* drop functions */ 
+static int delete_server_record(TABLE *table,
+                                char *server_name,
+                                int server_name_length);
+static int delete_server_record_in_cache(LEX_SERVER_OPTIONS *server_options);
+
+/* update functions */
+static void prepare_server_struct_for_update(LEX_SERVER_OPTIONS *server_options,
+                                             FOREIGN_SERVER *existing,
+                                             FOREIGN_SERVER *altered);
+static int update_server(THD *thd, FOREIGN_SERVER *existing, 
+					     FOREIGN_SERVER *altered);
+static int update_server_record(TABLE *table, FOREIGN_SERVER *server);
+static int update_server_record_in_cache(FOREIGN_SERVER *existing,
+                                         FOREIGN_SERVER *altered);
+/* utility functions */
+static void merge_server_struct(FOREIGN_SERVER *from, FOREIGN_SERVER *to);
+
+
+
 static byte *servers_cache_get_key(FOREIGN_SERVER *server, uint *length,
 			       my_bool not_used __attribute__((unused)))
 {
@@ -45,6 +74,7 @@ static byte *servers_cache_get_key(FOREIGN_SERVER *server, uint *length,
   DBUG_RETURN((byte*) server->server_name);
 }
 
+
 /*
   Initialize structures responsible for servers used in federated
   server scheme information for them from the server
@@ -64,35 +94,27 @@ static byte *servers_cache_get_key(FOREIGN_SERVER *server, uint *length,
     1	Could not initialize servers
 */
 
-my_bool servers_init(bool dont_read_servers_table)
+bool servers_init(bool dont_read_servers_table)
 {
   THD  *thd;
-  my_bool return_val= 0;
+  bool return_val= FALSE;
   DBUG_ENTER("servers_init");
 
   /* init the mutex */
-  if (pthread_mutex_init(&servers_cache_mutex, MY_MUTEX_INIT_FAST))
-    DBUG_RETURN(1);
-
   if (my_rwlock_init(&THR_LOCK_servers, NULL))
-    DBUG_RETURN(1);
+    DBUG_RETURN(TRUE);
 
   /* initialise our servers cache */
   if (hash_init(&servers_cache, system_charset_info, 32, 0, 0,
                 (hash_get_key) servers_cache_get_key, 0, 0))
   {
-    return_val= 1; /* we failed, out of memory? */
+    return_val= TRUE; /* we failed, out of memory? */
     goto end;
   }
 
   /* Initialize the mem root for data */
   init_alloc_root(&mem, ACL_ALLOC_BLOCK_SIZE, 0);
 
-  /*
-    at this point, the cache is initialised, let it be known
-  */
-  servers_cache_initialised= TRUE;
-
   if (dont_read_servers_table)
     goto end;
 
@@ -100,7 +122,7 @@ my_bool servers_init(bool dont_read_servers_table)
     To be able to run this from boot, we allocate a temporary THD
   */
   if (!(thd=new THD))
-    DBUG_RETURN(1);
+    DBUG_RETURN(TRUE);
   thd->thread_stack= (char*) &thd;
   thd->store_globals();
   /*
@@ -130,19 +152,13 @@ end:
     TRUE   Error
 */
 
-static my_bool servers_load(THD *thd, TABLE_LIST *tables)
+static bool servers_load(THD *thd, TABLE_LIST *tables)
 {
   TABLE *table;
   READ_RECORD read_record_info;
-  my_bool return_val= TRUE;
+  bool return_val= TRUE;
   DBUG_ENTER("servers_load");
 
-  if (!servers_cache_initialised)
-    DBUG_RETURN(0);
-
-  /* need to figure out how to utilise this variable */
-  servers_version++; /* servers updated */
-
   /* first, send all cached rows to sleep with the fishes, oblivion!
      I expect this crappy comment replaced */
   free_root(&mem, MYF(MY_MARK_BLOCKS_FREE));
@@ -156,7 +172,7 @@ static my_bool servers_load(THD *thd, TABLE_LIST *tables)
       goto end;
   }
 
-  return_val=0;
+  return_val= FALSE;
 
 end:
   end_read_record(&read_record_info);
@@ -183,10 +199,10 @@ end:
     TRUE   Failure
 */
 
-my_bool servers_reload(THD *thd)
+bool servers_reload(THD *thd)
 {
   TABLE_LIST tables[1];
-  my_bool return_val= 1;
+  bool return_val= TRUE;
   DBUG_ENTER("servers_reload");
 
   if (thd->locked_tables)
@@ -196,10 +212,9 @@ my_bool servers_reload(THD *thd)
     close_thread_tables(thd);
   }
 
-  /*
-    To avoid deadlocks we should obtain table locks before
-    obtaining servers_cache->lock mutex.
-  */
+  DBUG_PRINT("info", ("locking servers_cache"));
+  rw_wrlock(&THR_LOCK_servers);
+
   bzero((char*) tables, sizeof(tables));
   tables[0].alias= tables[0].table_name= (char*) "servers";
   tables[0].db= (char*) "mysql";
@@ -212,12 +227,6 @@ my_bool servers_reload(THD *thd)
     goto end;
   }
 
-  DBUG_PRINT("info", ("locking servers_cache"));
-  VOID(pthread_mutex_lock(&servers_cache_mutex));
-
-  //old_servers_cache= servers_cache;
-  //old_mem=mem;
-
   if ((return_val= servers_load(thd, tables)))
   {					// Error. Revert to old list
     /* blast, for now, we have no servers, discuss later way to preserve */
@@ -226,14 +235,14 @@ my_bool servers_reload(THD *thd)
     servers_free();
   }
 
-  DBUG_PRINT("info", ("unlocking servers_cache"));
-  VOID(pthread_mutex_unlock(&servers_cache_mutex));
-
 end:
   close_thread_tables(thd);
+  DBUG_PRINT("info", ("unlocking servers_cache"));
+  rw_unlock(&THR_LOCK_servers);
   DBUG_RETURN(return_val);
 }
 
+
 /*
   Initialize structures responsible for servers used in federated
   server scheme information for them from the server
@@ -260,7 +269,8 @@ end:
     1	could not insert server struct into global servers cache
 */
 
-my_bool get_server_from_table_to_cache(TABLE *table)
+static bool 
+get_server_from_table_to_cache(TABLE *table)
 {
   /* alloc a server struct */
   char *ptr;
@@ -308,69 +318,6 @@ my_bool get_server_from_table_to_cache(TABLE *table)
   DBUG_RETURN(FALSE);
 }
 
-/*
-  SYNOPSIS
-    server_exists_in_table()
-      THD   *thd - thread pointer
-      LEX_SERVER_OPTIONS *server_options - pointer to Lex->server_options
-
-  NOTES
-    This function takes a LEX_SERVER_OPTIONS struct, which is very much the
-    same type of structure as a FOREIGN_SERVER, it contains the values parsed
-    in any one of the [CREATE|DELETE|DROP] SERVER statements. Using the
-    member "server_name", index_read_idx either founds the record and returns
-    1, or doesn't find the record, and returns 0
-
-  RETURN VALUES
-    0   record not found
-    1	record found
-*/
-
-my_bool server_exists_in_table(THD *thd, LEX_SERVER_OPTIONS *server_options)
-{
-  int result= 1;
-  int error= 0;
-  TABLE_LIST tables;
-  TABLE *table;
-  DBUG_ENTER("server_exists");
-
-  bzero((char*) &tables, sizeof(tables));
-  tables.db= (char*) "mysql";
-  tables.alias= tables.table_name= (char*) "servers";
-
-  /* need to open before acquiring THR_LOCK_plugin or it will deadlock */
-  if (! (table= open_ltable(thd, &tables, TL_WRITE)))
-    DBUG_RETURN(TRUE);
-
-  table->use_all_columns();
-
-  rw_wrlock(&THR_LOCK_servers);
-  VOID(pthread_mutex_lock(&servers_cache_mutex));
-
-  /* set the field that's the PK to the value we're looking for */
-  table->field[0]->store(server_options->server_name,
-                         server_options->server_name_length,
-                         system_charset_info);
-
-  if ((error= table->file->index_read_idx(table->record[0], 0,
-                                   (byte *)table->field[0]->ptr,
-                                   table->key_info[0].key_length,
-                                   HA_READ_KEY_EXACT)))
-  {
-    if (error != HA_ERR_KEY_NOT_FOUND && error != HA_ERR_END_OF_FILE)
-    {
-      table->file->print_error(error, MYF(0));
-      result= -1;
-    }
-    result= 0;
-    DBUG_PRINT("info",("record for server '%s' not found!",
-                       server_options->server_name));
-  }
-
-  VOID(pthread_mutex_unlock(&servers_cache_mutex));
-  rw_unlock(&THR_LOCK_servers);
-  DBUG_RETURN(result);
-}
 
 /*
   SYNOPSIS
@@ -382,15 +329,18 @@ my_bool server_exists_in_table(THD *thd, LEX_SERVER_OPTIONS *server_options)
     This function takes a server object that is has all members properly
     prepared, ready to be inserted both into the mysql.servers table and
     the servers cache.
+	
+    THR_LOCK_servers must be write locked.
 
   RETURN VALUES
     0  - no error
     other - error code
 */
 
-int insert_server(THD *thd, FOREIGN_SERVER *server)
+static int 
+insert_server(THD *thd, FOREIGN_SERVER *server)
 {
-  int error= 0;
+  int error= -1;
   TABLE_LIST tables;
   TABLE *table;
 
@@ -402,13 +352,7 @@ int insert_server(THD *thd, FOREIGN_SERVER *server)
 
   /* need to open before acquiring THR_LOCK_plugin or it will deadlock */
   if (! (table= open_ltable(thd, &tables, TL_WRITE)))
-    DBUG_RETURN(TRUE);
-
-  /* lock mutex to make sure no changes happen */
-  VOID(pthread_mutex_lock(&servers_cache_mutex));
-
-  /* lock table */
-  rw_wrlock(&THR_LOCK_servers);
+    goto end;
 
   /* insert the server into the table */
   if ((error= insert_server_record(table, server)))
@@ -419,12 +363,10 @@ int insert_server(THD *thd, FOREIGN_SERVER *server)
     goto end;
 
 end:
-  /* unlock the table */
-  rw_unlock(&THR_LOCK_servers);
-  VOID(pthread_mutex_unlock(&servers_cache_mutex));
   DBUG_RETURN(error);
 }
 
+
 /*
   SYNOPSIS
     int insert_server_record_into_cache()
@@ -434,13 +376,16 @@ end:
     This function takes a FOREIGN_SERVER pointer to an allocated (root mem)
     and inserts it into the global servers cache
 
+    THR_LOCK_servers must be write locked.
+
   RETURN VALUE
     0   - no error
     >0  - error code
 
 */
 
-int insert_server_record_into_cache(FOREIGN_SERVER *server)
+static int 
+insert_server_record_into_cache(FOREIGN_SERVER *server)
 {
   int error=0;
   DBUG_ENTER("insert_server_record_into_cache");
@@ -461,6 +406,7 @@ int insert_server_record_into_cache(FOREIGN_SERVER *server)
   DBUG_RETURN(error);
 }
 
+
 /*
   SYNOPSIS
     store_server_fields()
@@ -478,7 +424,8 @@ int insert_server_record_into_cache(FOREIGN_SERVER *server)
 
 */
 
-void store_server_fields(TABLE *table, FOREIGN_SERVER *server)
+static void 
+store_server_fields(TABLE *table, FOREIGN_SERVER *server)
 {
 
   table->use_all_columns();
@@ -539,6 +486,7 @@ void store_server_fields(TABLE *table, FOREIGN_SERVER *server)
 
   */
 
+static
 int insert_server_record(TABLE *table, FOREIGN_SERVER *server)
 {
   int error;
@@ -606,7 +554,7 @@ int insert_server_record(TABLE *table, FOREIGN_SERVER *server)
 
 int drop_server(THD *thd, LEX_SERVER_OPTIONS *server_options)
 {
-  int error= 0;
+  int error;
   TABLE_LIST tables;
   TABLE *table;
 
@@ -618,28 +566,33 @@ int drop_server(THD *thd, LEX_SERVER_OPTIONS *server_options)
   tables.db= (char*) "mysql";
   tables.alias= tables.table_name= (char*) "servers";
 
-  /* need to open before acquiring THR_LOCK_plugin or it will deadlock */
-  if (! (table= open_ltable(thd, &tables, TL_WRITE)))
-    DBUG_RETURN(TRUE);
-
   rw_wrlock(&THR_LOCK_servers);
-  VOID(pthread_mutex_lock(&servers_cache_mutex));
 
+  /* hit the memory hit first */
+  if ((error= delete_server_record_in_cache(server_options)))
+    goto end;
 
-  if ((error= delete_server_record(table,
-                                   server_options->server_name,
-                                   server_options->server_name_length)))
+  if (! (table= open_ltable(thd, &tables, TL_WRITE)))
+  {
+    error= my_errno;
     goto end;
+  }
 
+  error= delete_server_record(table,
+                              server_options->server_name,
+                              server_options->server_name_length);
 
-  if ((error= delete_server_record_in_cache(server_options)))
-    goto end;
+  /*
+	Perform a reload so we don't have a 'hole' in our mem_root
+  */
+  servers_load(thd, &tables);
 
 end:
-  VOID(pthread_mutex_unlock(&servers_cache_mutex));
   rw_unlock(&THR_LOCK_servers);
   DBUG_RETURN(error);
 }
+
+
 /*
 
   SYNOPSIS
@@ -658,10 +611,10 @@ end:
 
 */
 
-int delete_server_record_in_cache(LEX_SERVER_OPTIONS *server_options)
+static int 
+delete_server_record_in_cache(LEX_SERVER_OPTIONS *server_options)
 {
-
-  int error= 0;
+  int error= ER_FOREIGN_SERVER_DOESNT_EXIST;
   FOREIGN_SERVER *server;
   DBUG_ENTER("delete_server_record_in_cache");
 
@@ -677,7 +630,7 @@ int delete_server_record_in_cache(LEX_SERVER_OPTIONS *server_options)
     DBUG_PRINT("info", ("server_name %s length %d not found!",
                         server_options->server_name,
                         server_options->server_name_length));
-    // what should be done if not found in the cache?
+    goto end;
   }
   /*
     We succeded in deletion of the server to the table, now delete
@@ -687,14 +640,15 @@ int delete_server_record_in_cache(LEX_SERVER_OPTIONS *server_options)
                      server->server_name,
                      server->server_name_length));
 
-  if (server)
-    VOID(hash_delete(&servers_cache, (byte*) server));
-
-  servers_version++; /* servers updated */
+  VOID(hash_delete(&servers_cache, (byte*) server));
+  
+  error= 0;
 
+end:
   DBUG_RETURN(error);
 }
 
+
 /*
 
   SYNOPSIS
@@ -714,6 +668,8 @@ int delete_server_record_in_cache(LEX_SERVER_OPTIONS *server_options)
     table for the particular server via the call to update_server_record,
     and in the servers_cache via update_server_record_in_cache. 
 
+    THR_LOCK_servers must be write locked.
+
   RETURN VALUE
     0 - no error
     >0 - error code
@@ -722,7 +678,7 @@ int delete_server_record_in_cache(LEX_SERVER_OPTIONS *server_options)
 
 int update_server(THD *thd, FOREIGN_SERVER *existing, FOREIGN_SERVER *altered)
 {
-  int error= 0;
+  int error;
   TABLE *table;
   TABLE_LIST tables;
   DBUG_ENTER("update_server");
@@ -732,19 +688,26 @@ int update_server(THD *thd, FOREIGN_SERVER *existing, FOREIGN_SERVER *altered)
   tables.alias= tables.table_name= (char*)"servers";
 
   if (!(table= open_ltable(thd, &tables, TL_WRITE)))
-    DBUG_RETURN(1);
+  {
+    error= my_errno;
+    goto end;
+  }
 
-  rw_wrlock(&THR_LOCK_servers);
   if ((error= update_server_record(table, altered)))
     goto end;
 
-  update_server_record_in_cache(existing, altered);
+  error= update_server_record_in_cache(existing, altered);
+
+  /*
+	Perform a reload so we don't have a 'hole' in our mem_root
+  */
+  servers_load(thd, &tables);
 
 end:
-  rw_unlock(&THR_LOCK_servers);
   DBUG_RETURN(error);
 }
 
+
 /*
 
   SYNOPSIS
@@ -761,6 +724,8 @@ end:
     HASH, then the updated record inserted, in essence replacing the old
     record.
 
+    THR_LOCK_servers must be write locked.
+
   RETURN VALUE
     0 - no error
     1 - error
@@ -791,13 +756,13 @@ int update_server_record_in_cache(FOREIGN_SERVER *existing,
   {
     DBUG_PRINT("info", ("had a problem inserting server %s at %lx",
                         altered->server_name, (long unsigned int) altered));
-    error= 1;
+    error= ER_OUT_OF_RESOURCES;
   }
 
-  servers_version++; /* servers updated */
   DBUG_RETURN(error);
 }
 
+
 /*
 
   SYNOPSIS
@@ -830,9 +795,9 @@ void merge_server_struct(FOREIGN_SERVER *from, FOREIGN_SERVER *to)
     to->password= strdup_root(&mem, from->password);
   if (to->port == -1)
     to->port= from->port;
-  if (!to->socket)
+  if (!to->socket && from->socket)
     to->socket= strdup_root(&mem, from->socket);
-  if (!to->scheme)
+  if (!to->scheme && from->scheme)
     to->scheme= strdup_root(&mem, from->scheme);
   if (!to->owner)
     to->owner= strdup_root(&mem, from->owner);
@@ -840,6 +805,7 @@ void merge_server_struct(FOREIGN_SERVER *from, FOREIGN_SERVER *to)
   DBUG_VOID_RETURN;
 }
 
+
 /*
 
   SYNOPSIS
@@ -862,7 +828,9 @@ void merge_server_struct(FOREIGN_SERVER *from, FOREIGN_SERVER *to)
 
 */
 
-int update_server_record(TABLE *table, FOREIGN_SERVER *server)
+
+static int 
+update_server_record(TABLE *table, FOREIGN_SERVER *server)
 {
   int error=0;
   DBUG_ENTER("update_server_record");
@@ -878,10 +846,7 @@ int update_server_record(TABLE *table, FOREIGN_SERVER *server)
                                    HA_READ_KEY_EXACT)))
   {
     if (error != HA_ERR_KEY_NOT_FOUND && error != HA_ERR_END_OF_FILE)
-    {
       table->file->print_error(error, MYF(0));
-      error= 1;
-    }
     DBUG_PRINT("info",("server not found!"));
     error= ER_FOREIGN_SERVER_DOESNT_EXIST;
   }
@@ -901,6 +866,7 @@ end:
   DBUG_RETURN(error);
 }
 
+
 /*
 
   SYNOPSIS
@@ -916,11 +882,11 @@ end:
 
 */
 
-int delete_server_record(TABLE *table,
-                         char *server_name,
-                         int server_name_length)
+static int 
+delete_server_record(TABLE *table,
+                     char *server_name, int server_name_length)
 {
-  int error= 0;
+  int error;
   DBUG_ENTER("delete_server_record");
   table->use_all_columns();
 
@@ -933,10 +899,7 @@ int delete_server_record(TABLE *table,
                                    HA_READ_KEY_EXACT)))
   {
     if (error != HA_ERR_KEY_NOT_FOUND && error != HA_ERR_END_OF_FILE)
-    {
       table->file->print_error(error, MYF(0));
-      error= 1;
-    }
     DBUG_PRINT("info",("server not found!"));
     error= ER_FOREIGN_SERVER_DOESNT_EXIST;
   }
@@ -965,28 +928,35 @@ int delete_server_record(TABLE *table,
 
 int create_server(THD *thd, LEX_SERVER_OPTIONS *server_options)
 {
-  int error;
+  int error= ER_FOREIGN_SERVER_EXISTS;
   FOREIGN_SERVER *server;
 
   DBUG_ENTER("create_server");
   DBUG_PRINT("info", ("server_options->server_name %s",
                       server_options->server_name));
 
+  rw_wrlock(&THR_LOCK_servers);
+
+  /* hit the memory first */
+  if (hash_search(&servers_cache, (byte*) server_options->server_name,
+				   server_options->server_name_length))
+    goto end;
+
   server= (FOREIGN_SERVER *)alloc_root(&mem,
                                        sizeof(FOREIGN_SERVER));
 
-  if ((error= prepare_server_struct_for_insert(server_options, server)))
-    goto end;
+  prepare_server_struct_for_insert(server_options, server);
 
-  if ((error= insert_server(thd, server)))
-    goto end;
+  error= insert_server(thd, server);
 
   DBUG_PRINT("info", ("error returned %d", error));
 
 end:
+  rw_unlock(&THR_LOCK_servers);
   DBUG_RETURN(error);
 }
 
+
 /*
 
   SYNOPSIS
@@ -1003,37 +973,33 @@ end:
 
 int alter_server(THD *thd, LEX_SERVER_OPTIONS *server_options)
 {
-  int error= 0;
+  int error= ER_FOREIGN_SERVER_DOESNT_EXIST;
   FOREIGN_SERVER *altered, *existing;
   DBUG_ENTER("alter_server");
   DBUG_PRINT("info", ("server_options->server_name %s",
                       server_options->server_name));
 
-  altered= (FOREIGN_SERVER *)alloc_root(&mem,
-                                        sizeof(FOREIGN_SERVER));
-
-  VOID(pthread_mutex_lock(&servers_cache_mutex));
+  rw_wrlock(&THR_LOCK_servers);
 
   if (!(existing= (FOREIGN_SERVER *) hash_search(&servers_cache,
                                                  (byte*) server_options->server_name,
                                                server_options->server_name_length)))
-  {
-    error= ER_FOREIGN_SERVER_DOESNT_EXIST;
     goto end;
-  }
 
-  if ((error= prepare_server_struct_for_update(server_options, existing, altered)))
-    goto end;
+  altered= (FOREIGN_SERVER *)alloc_root(&mem,
+                                        sizeof(FOREIGN_SERVER));
 
-  if ((error= update_server(thd, existing, altered)))
-    goto end;
+  prepare_server_struct_for_update(server_options, existing, altered);
+
+  error= update_server(thd, existing, altered);
 
 end:
   DBUG_PRINT("info", ("error returned %d", error));
-  VOID(pthread_mutex_unlock(&servers_cache_mutex));
+  rw_unlock(&THR_LOCK_servers);
   DBUG_RETURN(error);
 }
 
+
 /*
 
   SYNOPSIS
@@ -1044,19 +1010,17 @@ end:
   NOTES
 
   RETURN VALUE
-    0 - no error
+    none
 
 */
 
-int prepare_server_struct_for_insert(LEX_SERVER_OPTIONS *server_options,
-                                     FOREIGN_SERVER *server)
+static void
+prepare_server_struct_for_insert(LEX_SERVER_OPTIONS *server_options,
+                                 FOREIGN_SERVER *server)
 {
-  int error;
   char *unset_ptr= (char*)"";
   DBUG_ENTER("prepare_server_struct");
 
-  error= 0;
-
   /* these two MUST be set */
   server->server_name= strdup_root(&mem, server_options->server_name);
   server->server_name_length= server_options->server_name_length;
@@ -1086,7 +1050,7 @@ int prepare_server_struct_for_insert(LEX_SERVER_OPTIONS *server_options,
   server->owner= server_options->owner ?
     strdup_root(&mem, server_options->owner) : unset_ptr;
 
-  DBUG_RETURN(error);
+  DBUG_VOID_RETURN;
 }
 
 /*
@@ -1102,13 +1066,12 @@ int prepare_server_struct_for_insert(LEX_SERVER_OPTIONS *server_options,
 
 */
 
-int prepare_server_struct_for_update(LEX_SERVER_OPTIONS *server_options,
-                                     FOREIGN_SERVER *existing,
-                                     FOREIGN_SERVER *altered)
+static void
+prepare_server_struct_for_update(LEX_SERVER_OPTIONS *server_options,
+                                 FOREIGN_SERVER *existing,
+                                 FOREIGN_SERVER *altered)
 {
-  int error;
   DBUG_ENTER("prepare_server_struct_for_update");
-  error= 0;
 
   altered->server_name= strdup_root(&mem, server_options->server_name);
   altered->server_name_length= server_options->server_name_length;
@@ -1159,7 +1122,7 @@ int prepare_server_struct_for_update(LEX_SERVER_OPTIONS *server_options,
     (strcmp(server_options->owner, existing->owner))) ?
       strdup_root(&mem, server_options->owner) : 0;
 
-  DBUG_RETURN(error);
+  DBUG_VOID_RETURN;
 }
 
 /*
@@ -1178,17 +1141,15 @@ int prepare_server_struct_for_update(LEX_SERVER_OPTIONS *server_options,
 void servers_free(bool end)
 {
   DBUG_ENTER("servers_free");
-  if (!servers_cache_initialised)
+  if (!hash_inited(&servers_cache))
     DBUG_VOID_RETURN;
-  VOID(pthread_mutex_destroy(&servers_cache_mutex));
-  servers_cache_initialised=0;
+  rwlock_destroy(&THR_LOCK_servers);
   free_root(&mem,MYF(0));
   hash_free(&servers_cache);
   DBUG_VOID_RETURN;
 }
 
 
-
 /*
 
   SYNOPSIS
@@ -1220,7 +1181,7 @@ FOREIGN_SERVER *get_server_by_name(const char *server_name)
   }
 
   DBUG_PRINT("info", ("locking servers_cache"));
-  VOID(pthread_mutex_lock(&servers_cache_mutex));
+  rw_rdlock(&THR_LOCK_servers);
   if (!(server= (FOREIGN_SERVER *) hash_search(&servers_cache,
                                                (byte*) server_name,
                                                server_name_length)))
@@ -1230,7 +1191,7 @@ FOREIGN_SERVER *get_server_by_name(const char *server_name)
     server= (FOREIGN_SERVER *) NULL;
   }
   DBUG_PRINT("info", ("unlocking servers_cache"));
-  VOID(pthread_mutex_unlock(&servers_cache_mutex));
+  rw_unlock(&THR_LOCK_servers);
   DBUG_RETURN(server);
 
 }