1. 29 Nov, 2007 1 commit
    • davi@mysql.com/endora.local's avatar
      Bug#23713 LOCK TABLES + CREATE TRIGGER + FLUSH TABLES WITH READ LOCK = deadlock · d179bb64
      davi@mysql.com/endora.local authored
      This bug is actually two bugs in one, one of which is CREATE TRIGGER under
      LOCK TABLES and the other is CREATE TRIGGER under LOCK TABLES simultaneous
      to a FLUSH TABLES WITH READ LOCK (global read lock). Both situations could
      lead to a server crash or deadlock.
      
      The first problem arises from the fact that when under LOCK TABLES, if the
      table is in the set of locked tables, the table is already open and it doesn't
      need to be reopened (not a placeholder). Also in this case, if the table is
      not write locked, a exclusive lock can't be acquired because of a possible
      deadlock with another thread also holding a (read) lock on the table. The
      second issue arises from the fact that one should never wait for a global
      read lock if it's holding any locked tables, because the global read lock
      is waiting for these tables and this leads to a circular wait deadlock.
      
      The solution for the first case is to check if the table is write locked
      and upgraded the write lock to a exclusive lock and fail otherwise for non
      write locked tables. Grabbin the exclusive lock in this case also means
      to ensure that the table is opened only by the calling thread. The second
      issue is partly fixed by not waiting for the global read lock if the thread
      is holding any locked tables.
      
      The second issue is only partly addressed in this patch because it turned
      out to be much wider and also affects other DDL statements. Reported as
      Bug#32395
      d179bb64
  2. 28 Nov, 2007 13 commits
  3. 27 Nov, 2007 16 commits
  4. 26 Nov, 2007 10 commits