ha_innodb.h, ha_innodb.cc, handler.h, handler.cc, sql_class.cc:

  Fix a hang on the adaptive hash S-latch if an application program uses mysql_use_result() and performs queries on two connections at the same time


sql/sql_class.cc:
  Fix a hang on the adaptive hash S-latch if an application program uses mysql_use_result() and performs queries on two connections at the same time
sql/handler.cc:
  Fix a hang on the adaptive hash S-latch if an application program uses mysql_use_result() and performs queries on two connections at the same time
sql/handler.h:
  Fix a hang on the adaptive hash S-latch if an application program uses mysql_use_result() and performs queries on two connections at the same time
sql/ha_innodb.cc:
  Fix a hang on the adaptive hash S-latch if an application program uses mysql_use_result() and performs queries on two connections at the same time
sql/ha_innodb.h:
  Fix a hang on the adaptive hash S-latch if an application program uses mysql_use_result() and performs queries on two connections at the same time

1 files changed, 30 insertions, 0 deletions

diff --git a/sql/handler.cc b/sql/handler.cc
index fb33888e91e..3fae7c3bd72 100644
--- a/sql/handler.cc
+++ b/sql/handler.cc
@@ -238,8 +238,10 @@ int ha_autocommit_or_rollback(THD *thd, int error)
   handler must be the same as in the binlog.
 
   arguments:
+  thd:           the thread handle of the current connection
   log_file_name: latest binlog file name
   end_offset:	 the offset in the binlog file up to which we wrote
+  return value:  0 if success, 1 if error
 */
 
 int ha_report_binlog_offset_and_commit(THD *thd,
@@ -266,6 +268,34 @@ int ha_report_binlog_offset_and_commit(THD *thd,
   return error;
 }
 
+/*
+  This function should be called when MySQL sends rows of a SELECT result set
+  or the EOF mark to the client. It releases a possible adaptive hash index
+  S-latch held by thd in InnoDB and also releases a possible InnoDB query
+  FIFO ticket to enter InnoDB. To save CPU time, InnoDB allows a thd to
+  keep them over several calls of the InnoDB handler interface when a join
+  is executed. But when we let the control to pass to the client they have
+  to be released because if the application program uses mysql_use_result(),
+  it may deadlock on the S-latch if the application on another connection
+  performs another SQL query. In MySQL-4.1 this is even more important because
+  there a connection can have several SELECT queries open at the same time.
+
+  arguments:
+  thd:           the thread handle of the current connection
+  return value:  always 0
+*/
+
+int ha_release_temporary_latches(THD *thd)
+{
+#ifdef HAVE_INNOBASE_DB
+  THD_TRANS *trans;
+  trans = &thd->transaction.all;
+  if (trans->innobase_tid)
+    innobase_release_temporary_latches(trans->innobase_tid);
+#endif
+  return 0;
+}
+
 int ha_commit_trans(THD *thd, THD_TRANS* trans)
 {
   int error=0;