diff options
Diffstat (limited to 'sql/lock.cc')
| -rw-r--r-- | sql/lock.cc | 18 |
1 files changed, 14 insertions, 4 deletions
diff --git a/sql/lock.cc b/sql/lock.cc index f4c4a781e45..fe8dcb3aa5e 100644 --- a/sql/lock.cc +++ b/sql/lock.cc @@ -815,10 +815,13 @@ static void print_lock_error(int error, const char *table) access to them is protected with a mutex LOCK_global_read_lock - (XXX: one should never take LOCK_open if LOCK_global_read_lock is taken, - otherwise a deadlock may occur - see mysql_rm_table. Other mutexes could - be a problem too - grep the code for global_read_lock if you want to use - any other mutex here) + (XXX: one should never take LOCK_open if LOCK_global_read_lock is + taken, otherwise a deadlock may occur. Other mutexes could be a + problem too - grep the code for global_read_lock if you want to use + any other mutex here) Also one must not hold LOCK_open when calling + wait_if_global_read_lock(). When the thread with the global read lock + tries to close its tables, it needs to take LOCK_open in + close_thread_table(). How blocking of threads by global read lock is achieved: that's advisory. Any piece of code which should be blocked by global read lock must @@ -937,6 +940,13 @@ bool wait_if_global_read_lock(THD *thd, bool abort_on_refresh, DBUG_ENTER("wait_if_global_read_lock"); LINT_INIT(old_message); + /* + Assert that we do not own LOCK_open. If we would own it, other + threads could not close their tables. This would make a pretty + deadlock. + */ + safe_mutex_assert_not_owner(&LOCK_open); + (void) pthread_mutex_lock(&LOCK_global_read_lock); if ((need_exit_cond= must_wait)) { |