Merge bk-internal.mysql.com:/home/bk/mysql-5.1

into  bodhi.(none):/opt/local/work/mysql-5.1-runtime

1 files changed, 109 insertions, 16 deletions

diff --git a/sql/lock.cc b/sql/lock.cc
index 63d0807b975..08ff90ce983 100644
--- a/sql/lock.cc
+++ b/sql/lock.cc
@@ -116,16 +116,90 @@ static void print_lock_error(int error, const char *);
 static int thr_lock_errno_to_mysql[]=
 { 0, 1, ER_LOCK_WAIT_TIMEOUT, ER_LOCK_DEADLOCK };
 
+/**
+  Perform semantic checks for mysql_lock_tables.
+  @param thd The current thread
+  @param tables The tables to lock
+  @param count The number of tables to lock
+  @param flags Lock flags
+  @return 0 if all the check passed, non zero if a check failed.
+*/
+int mysql_lock_tables_check(THD *thd, TABLE **tables, uint count, uint flags)
+{
+  bool log_table_write_query;
+  uint system_count;
+  uint i;
+
+  DBUG_ENTER("mysql_lock_tables_check");
+
+  system_count= 0;
+  log_table_write_query= (is_log_table_write_query(thd->lex->sql_command)
+                         || ((flags & MYSQL_LOCK_PERF_SCHEMA) != 0));
+
+  for (i=0 ; i<count; i++)
+  {
+    TABLE *t= tables[i];
+
+    /* Protect against 'fake' partially initialized TABLE_SHARE */
+    DBUG_ASSERT(t->s->table_category != TABLE_UNKNOWN_CATEGORY);
+
+    /*
+      Table I/O to performance schema tables is performed
+      only internally by the server implementation.
+      When a user is requesting a lock, the following
+      constraints are enforced:
+    */
+    if (t->s->require_write_privileges() &&
+        ! log_table_write_query)
+    {
+      /*
+        A user should not be able to prevent writes,
+        or hold any type of lock in a session,
+        since this would be a DOS attack.
+      */
+      if ((t->reginfo.lock_type >= TL_READ_NO_INSERT)
+          || (thd->lex->sql_command == SQLCOM_LOCK_TABLES))
+      {
+        my_error(ER_CANT_LOCK_LOG_TABLE, MYF(0));
+        DBUG_RETURN(1);
+      }
+    }
+
+    if ((t->s->table_category == TABLE_CATEGORY_SYSTEM) &&
+        (t->reginfo.lock_type >= TL_WRITE_ALLOW_WRITE))
+    {
+      system_count++;
+    }
+  }
+
+  /*
+    Locking of system tables is restricted:
+    locking a mix of system and non-system tables in the same lock
+    is prohibited, to prevent contention.
+  */
+  if ((system_count > 0) && (system_count < count))
+  {
+    my_error(ER_WRONG_LOCK_OF_SYSTEM_TABLE, MYF(0));
+    DBUG_RETURN(1);
+  }
+
+  DBUG_RETURN(0);
+}
+
 MYSQL_LOCK *mysql_lock_tables(THD *thd, TABLE **tables, uint count,
                               uint flags, bool *need_reopen)
 {
   MYSQL_LOCK *sql_lock;
   TABLE *write_lock_used;
   int rc;
+
   DBUG_ENTER("mysql_lock_tables");
 
   *need_reopen= FALSE;
 
+  if (mysql_lock_tables_check(thd, tables, count, flags))
+    DBUG_RETURN (NULL);
+
   for (;;)
   {
     if (! (sql_lock= get_lock_data(thd, tables, count, GET_LOCK_STORE_LOCKS,
@@ -175,7 +249,8 @@ MYSQL_LOCK *mysql_lock_tables(THD *thd, TABLE **tables, uint count,
 
     thd->proc_info="System lock";
     DBUG_PRINT("info", ("thd->proc_info %s", thd->proc_info));
-    if (lock_external(thd, tables, count))
+    if (sql_lock->table_count && lock_external(thd, sql_lock->table,
+                                               sql_lock->table_count))
     {
       /* Clear the lock type of all lock data to avoid reusage. */
       reset_lock_data(sql_lock);
@@ -271,6 +346,7 @@ static int lock_external(THD *thd, TABLE **tables, uint count)
 	((*tables)->reginfo.lock_type >= TL_READ &&
 	 (*tables)->reginfo.lock_type <= TL_READ_NO_INSERT))
       lock_type=F_RDLCK;
+
     if ((error=(*tables)->file->ha_external_lock(thd,lock_type)))
     {
       print_lock_error(error, (*tables)->file->table_type());
@@ -379,10 +455,28 @@ void mysql_unlock_read_tables(THD *thd, MYSQL_LOCK *sql_lock)
 }
 
 
+/**
+  Try to find the table in the list of locked tables.
+  In case of success, unlock the table and remove it from this list.
+
+  @note This function has a legacy side effect: the table is
+  unlocked even if it is not found in the locked list.
+  It's not clear if this side effect is intentional or still
+  desirable. It might lead to unmatched calls to
+  unlock_external(). Moreover, a discrepancy can be left
+  unnoticed by the storage engine, because in
+  unlock_external() we call handler::external_lock(F_UNLCK) only
+  if table->current_lock is not F_UNLCK.
+
+  @param  always_unlock   specify explicitly if the legacy side
+                          effect is desired.
+*/
 
-void mysql_lock_remove(THD *thd, MYSQL_LOCK *locked,TABLE *table)
+void mysql_lock_remove(THD *thd, MYSQL_LOCK *locked,TABLE *table,
+                       bool always_unlock)
 {
-  mysql_unlock_some_tables(thd, &table,1);
+  if (always_unlock == TRUE)
+    mysql_unlock_some_tables(thd, &table, /* table count */ 1);
   if (locked)
   {
     reg1 uint i;
@@ -396,6 +490,10 @@ void mysql_lock_remove(THD *thd, MYSQL_LOCK *locked,TABLE *table)
 
         DBUG_ASSERT(table->lock_position == i);
 
+        /* Unlock if not yet unlocked */
+        if (always_unlock == FALSE)
+          mysql_unlock_some_tables(thd, &table, /* table count */ 1);
+
         /* Decrement table_count in advance, making below expressions easier */
         old_tables= --locked->table_count;
 
@@ -445,7 +543,8 @@ void mysql_lock_downgrade_write(THD *thd, TABLE *table,
 {
   MYSQL_LOCK *locked;
   TABLE *write_lock_used;
-  if ((locked = get_lock_data(thd,&table,1,1,&write_lock_used)))
+  if ((locked = get_lock_data(thd, &table, 1, GET_LOCK_UNLOCK,
+                              &write_lock_used)))
   {
     for (uint i=0; i < locked->lock_count; i++)
       thr_downgrade_write_lock(locked->locks[i], new_lock_type);
@@ -704,25 +803,19 @@ static MYSQL_LOCK *get_lock_data(THD *thd, TABLE **table_ptr, uint count,
   TABLE **to, **table_buf;
   DBUG_ENTER("get_lock_data");
 
+  DBUG_ASSERT((flags == GET_LOCK_UNLOCK) || (flags == GET_LOCK_STORE_LOCKS));
+
   DBUG_PRINT("info", ("count %d", count));
   *write_lock_used=0;
-  uint system_count= 0;
   for (i=tables=lock_count=0 ; i < count ; i++)
   {
-    if (table_ptr[i]->s->tmp_table != NON_TRANSACTIONAL_TMP_TABLE)
+    TABLE *t= table_ptr[i];
+
+    if (t->s->tmp_table != NON_TRANSACTIONAL_TMP_TABLE)
     {
-      tables+=table_ptr[i]->file->lock_count();
+      tables+= t->file->lock_count();
       lock_count++;
     }
-    /*
-      Check if we can lock the table. For some tables we cannot do that
-      beacause of handler-specific locking issues.
-    */
-    if (!table_ptr[i]-> file->
-          check_if_locking_is_allowed(thd->lex->sql_command, thd->lex->type,
-                                      table_ptr[i], count, i, &system_count,
-                                      logger.is_privileged_thread(thd)))
-      DBUG_RETURN(0);
   }
 
   /*