bk commit into 5.0 tree (davi:1.2498) BUG#25164

[Davi Arnaut]

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ChangeSet@stripped, 2007-08-20 23:11:08-03:00, davi@stripped +1 -0
  Bug#25164 create table `a` as select * from `A` hangs
  
  If the thr_multi_lock() detects a deadlock (or timeouts), the table handler (storage
engine) lock must be unlocked. As the function comment indicates: each call to
external_lock(F_[RD|WR]LOCK) is followed by a call to external_lock(F_UNLCK) and if it is
not, it is a bug in MySQL.

  sql/lock.cc@stripped, 2007-08-20 23:11:04-03:00, davi@stripped +2 -0
    Unlock the table handler if it fails to acquire the thread lock.

diff -Nrup a/sql/lock.cc b/sql/lock.cc
--- a/sql/lock.cc	2007-08-16 14:51:30 -03:00
+++ b/sql/lock.cc	2007-08-20 23:11:04 -03:00
@@ -172,6 +172,8 @@ MYSQL_LOCK *mysql_lock_tables(THD *thd, 
                                                      thd->lock_id)];
     if (rc > 1)                                 /* a timeout or a deadlock */
     {
+      if (sql_lock->table_count)
+        VOID(unlock_external(thd, sql_lock->table, sql_lock->table_count));
       my_error(rc, MYF(0));
       my_free((gptr) sql_lock,MYF(0));
       sql_lock= 0;