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MDEV-3917 multiple use locks (GET_LOCK) in one connection.

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The patch contributed by Konstantin Osipov applied.
    Native comments:
      Implement multiple user-level locks per connection.

      GET_LOCK() function in MySQL allows a connection  to hold at most
      one user level lock. Taking a new lock automatically releases the
      old lock, if any.

      The limit of one lock per session existed since  early versions
      of MySQL didn't have a deadlock detector for SQL locks.
      MDL patches in MySQL 5.5 added a deadlock detector,
      so starting from 5.5 it became possible to take multiple locks
      in any order -- a deadlock, should it occur, would be detected
      and an error returned to the client which closed the wait chain.

      This is exactly what is done in this patch: ULLs are moved
      to use MDL subsystem.
This commit is contained in:
Alexey Botchkov
2013-04-12 18:06:51 +05:00
parent ff3407a111
commit 1a600125ff
14 changed files with 869 additions and 353 deletions
Download Patch File Download Diff File Expand all files Collapse all files

25
sql/sql_class.cc
View File

@@ -827,6 +827,7 @@ THD::THD()
col_access=0;
is_slave_error= thread_specific_used= FALSE;
my_hash_clear(&handler_tables_hash);
my_hash_clear(&ull_hash);
tmp_table=0;
cuted_fields= 0L;
sent_row_count= 0L;
@@ -866,7 +867,6 @@ THD::THD()
net.vio=0;
net.buff= 0;
client_capabilities= 0; // minimalistic client
ull=0;
system_thread= NON_SYSTEM_THREAD;
cleanup_done= abort_on_warning= 0;
peer_port= 0; // For SHOW PROCESSLIST
@@ -1400,8 +1400,6 @@ void THD::cleanup(void)
if (global_read_lock.is_acquired())
global_read_lock.unlock_global_read_lock(this);
/* All metadata locks must have been released by now. */
DBUG_ASSERT(!mdl_context.has_locks());
if (user_connect)
{
decrease_user_connections(user_connect);
@@ -1419,13 +1417,9 @@ void THD::cleanup(void)
sp_cache_clear(&sp_proc_cache);
sp_cache_clear(&sp_func_cache);
if (ull)
{
mysql_mutex_lock(&LOCK_user_locks);
item_user_lock_release(ull);
mysql_mutex_unlock(&LOCK_user_locks);
ull= NULL;
}
mysql_ull_cleanup(this);
/* All metadata locks must have been released by now. */
DBUG_ASSERT(!mdl_context.has_locks());
apc_target.destroy();
cleanup_done=1;
@@ -4001,6 +3995,15 @@ extern "C" unsigned long thd_get_thread_id(const MYSQL_THD thd)
}
/**
Check if THD socket is still connected.
*/
extern "C" int thd_is_connected(MYSQL_THD thd)
{
return thd->is_connected();
}
#ifdef INNODB_COMPATIBILITY_HOOKS
extern "C" const struct charset_info_st *thd_charset(MYSQL_THD thd)
{
@@ -4321,6 +4324,8 @@ void THD::leave_locked_tables_mode()
/* Also ensure that we don't release metadata locks for open HANDLERs. */
if (handler_tables_hash.records)
mysql_ha_set_explicit_lock_duration(this);
if (ull_hash.records)
mysql_ull_set_explicit_lock_duration(this);
}
locked_tables_mode= LTM_NONE;
}