Commit 0478ef18 authored by svoj@mysql.com/june.mysql.com's avatar svoj@mysql.com/june.mysql.com
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BUG#28574 - repair table causes queries to fail with various 

            corruption errors: 126,134,145

When one thread attempts to lock two (or more) tables and another
thread executes statement that aborts these locks (e.g. REPAIR
TABLE) we may get a table object with wrong lock type in a table
cache.

For example if SELECT FROM t1,t2 was aborted, subsequent INSERT
INTO t1 may be executed under read lock.

As a result we may get various table corruptions and even a server
crash.

This is fixed by resetting lock type in case lock was aborted by
another thread.

I failed to create reasonable test case for this bug.
parent a4ddc226

sql/lock.cc

+7 −0
Original line number Diff line number Diff line
@@ -155,6 +155,13 @@ MYSQL_LOCK *mysql_lock_tables(THD *thd, TABLE **tables, uint count, uint flags) 
    if (thr_multi_lock(sql_lock->locks + sql_lock->lock_count,

                       sql_lock->lock_count))

    {

      /*

        reset_lock_data is required here. If thr_multi_lock fails it

        resets lock type for tables, which were locked before (and

        including) one that caused error. Lock type for other tables

        preserved.

      */

      reset_lock_data(sql_lock);

      thd->some_tables_deleted=1;		// Try again

      sql_lock->lock_count=0;			// Locks are alread freed

    }