Bug#16986 - Deadlock condition with MyISAM tables

Addendum fixes after changing the condition variable
for the global read lock.

The stress test suite revealed some deadlocks. Some were
related to the new condition variable (COND_global_read_lock)
and some were general problems with the global read lock.

It is now necessary to signal COND_global_read_lock whenever 
COND_refresh is signalled.

We need to wait for the release of a global read lock if one 
is set before every operation that requires a write lock.
But we must not wait if we have locked tables by LOCK TABLES.
After setting a global read lock a thread waits until all
write locks are released.

1 files changed, 2 insertions, 24 deletions

diff --git a/sql/sql_insert.cc b/sql/sql_insert.cc
index 8ffc6f53a43..15c7f91ba83 100644
--- a/sql/sql_insert.cc
+++ b/sql/sql_insert.cc
@@ -1349,18 +1349,6 @@ static TABLE *delayed_get_table(THD *thd,TABLE_LIST *table_list)
     */
     if (! (tmp= find_handler(thd, table_list)))
     {
-      /*
-        Avoid that a global read lock steps in while we are creating the
-        new thread. It would block trying to open the table. Hence, the
-        DI thread and this thread would wait until after the global
-        readlock is gone. Since the insert thread needs to wait for a
-        global read lock anyway, we do it right now. Note that
-        wait_if_global_read_lock() sets a protection against a new
-        global read lock when it succeeds. This needs to be released by
-        start_waiting_global_read_lock().
-      */
-      if (wait_if_global_read_lock(thd, 0, 1))
-        goto err;
       if (!(tmp=new delayed_insert()))
       {
 	my_error(ER_OUTOFMEMORY,MYF(0),sizeof(delayed_insert));
@@ -1401,11 +1389,6 @@ static TABLE *delayed_get_table(THD *thd,TABLE_LIST *table_list)
 	pthread_cond_wait(&tmp->cond_client,&tmp->mutex);
       }
       pthread_mutex_unlock(&tmp->mutex);
-      /*
-        Release the protection against the global read lock and wake
-        everyone, who might want to set a global read lock.
-      */
-      start_waiting_global_read_lock(thd);
       thd->proc_info="got old table";
       if (tmp->thd.killed)
       {
@@ -1441,11 +1424,6 @@ static TABLE *delayed_get_table(THD *thd,TABLE_LIST *table_list)
 
  err1:
   thd->fatal_error();
-  /*
-    Release the protection against the global read lock and wake
-    everyone, who might want to set a global read lock.
-  */
-  start_waiting_global_read_lock(thd);
  err:
   pthread_mutex_unlock(&LOCK_delayed_create);
   DBUG_RETURN(0); // Continue with normal insert
@@ -2676,7 +2654,7 @@ bool select_create::send_eof()
       hash_delete(&open_cache,(byte*) table);
       /* Tell threads waiting for refresh that something has happened */
       if (version != refresh_version)
-        VOID(pthread_cond_broadcast(&COND_refresh));
+        broadcast_refresh();
     }
     lock=0;
     table=0;
@@ -2705,7 +2683,7 @@ void select_create::abort()
         quick_rm_table(table_type, create_table->db, create_table->table_name);
       /* Tell threads waiting for refresh that something has happened */
       if (version != refresh_version)
-        VOID(pthread_cond_broadcast(&COND_refresh));
+        broadcast_refresh();
     }
     else if (!create_info->table_existed)
       close_temporary_table(thd, create_table->db, create_table->table_name);