Bug #38816: kill + flush tables with read lock + stored

            procedures causes crashes!

The problem of that bugreport was mostly fixed by the
patch for bug 38691.
However, attached test case focused on another crash or
valgrind warning problem: SHOW PROCESSLIST query accesses
freed memory of SP instruction that run in a parallel
connection.

Changes of thd->query/thd->query_length in dangerous
places have been guarded with the per-thread
LOCK_thd_data mutex (the THD::LOCK_delete mutex has been
renamed to THD::LOCK_thd_data).


sql/ha_myisam.cc:
  Bug #38816: kill + flush tables with read lock + stored
              procedures causes crashes!
  
  Modification of THD::query/query_length has been guarded
  with the a THD::set_query() method call/LOCK_thd_data
  mutex.
  Unnecessary locking with the global LOCK_thread_count
  mutex has been removed.
sql/log_event.cc:
  Bug #38816: kill + flush tables with read lock + stored
              procedures causes crashes!
  
  Modification of THD::query/query_length has been guarded
  with the THD::set_query()) method call/LOCK_thd_data
  mutex.
sql/slave.cc:
  Bug #38816: kill + flush tables with read lock + stored
              procedures causes crashes!
  
  Modification of THD::query/query_length has been guarded
  with the THD::set_query() method call/LOCK_thd_data mutex.
  
  The THD::LOCK_delete mutex has been renamed to
  THD::LOCK_thd_data.
sql/sp_head.cc:
  Bug #38816: kill + flush tables with read lock + stored
              procedures causes crashes!
  
  Modification of THD::query/query_length has been guarded
  with the a THD::set_query() method call/LOCK_thd_data
  mutex.
sql/sql_class.cc:
  Bug #38816: kill + flush tables with read lock + stored
              procedures causes crashes!
  
  The new THD::LOCK_thd_data mutex and THD::set_query()
  method has been added to guard modifications of THD::query/
  THD::query_length fields, also the Statement::set_statement()
  method has been overloaded in the THD class.
  
  The THD::LOCK_delete mutex has been renamed to
  THD::LOCK_thd_data.
sql/sql_class.h:
  Bug #38816: kill + flush tables with read lock + stored
              procedures causes crashes!
  
  The new THD::LOCK_thd_data mutex and THD::set_query()
  method has been added to guard modifications of THD::query/
  THD::query_length fields, also the Statement::set_statement()
  method has been overloaded in the THD class.
  
  The THD::LOCK_delete mutex has been renamed to
  THD::LOCK_thd_data.
sql/sql_insert.cc:
  Bug #38816: kill + flush tables with read lock + stored
              procedures causes crashes!
  
  Modification of THD::query/query_length has been guarded
  with the a THD::set_query() method call/LOCK_thd_data
  mutex.
sql/sql_parse.cc:
  Bug #38816: kill + flush tables with read lock + stored
              procedures causes crashes!
  
  Modification of THD::query/query_length has been guarded
  with the a THD::set_query() method call/LOCK_thd_data mutex.
sql/sql_repl.cc:
  Bug #38816: kill + flush tables with read lock + stored
              procedures causes crashes!
  
  The THD::LOCK_delete mutex has been renamed to
  THD::LOCK_thd_data.
sql/sql_show.cc:
  Bug #38816: kill + flush tables with read lock + stored
              procedures causes crashes!
  
  Inter-thread read of THD::query/query_length field has
  been protected with a new per-thread LOCK_thd_data
  mutex in the mysqld_list_processes function.

1 files changed, 25 insertions, 6 deletions

diff --git a/sql/sql_class.cc b/sql/sql_class.cc
index 387e7022d71..7d26759cb16 100644
--- a/sql/sql_class.cc
+++ b/sql/sql_class.cc
@@ -259,7 +259,7 @@ THD::THD()
 #ifdef SIGNAL_WITH_VIO_CLOSE
   active_vio = 0;
 #endif
-  pthread_mutex_init(&LOCK_delete, MY_MUTEX_INIT_FAST);
+  pthread_mutex_init(&LOCK_thd_data, MY_MUTEX_INIT_FAST);
 
   /* Variables with default values */
   proc_info="login";
@@ -486,8 +486,8 @@ THD::~THD()
   THD_CHECK_SENTRY(this);
   DBUG_ENTER("~THD()");
   /* Ensure that no one is using THD */
-  pthread_mutex_lock(&LOCK_delete);
-  pthread_mutex_unlock(&LOCK_delete);
+  pthread_mutex_lock(&LOCK_thd_data);
+  pthread_mutex_unlock(&LOCK_thd_data);
   add_to_status(&global_status_var, &status_var);
 
   /* Close connection */
@@ -513,7 +513,7 @@ THD::~THD()
   free_root(&transaction.mem_root,MYF(0));
 #endif
   mysys_var=0;					// Safety (shouldn't be needed)
-  pthread_mutex_destroy(&LOCK_delete);
+  pthread_mutex_destroy(&LOCK_thd_data);
 #ifndef DBUG_OFF
   dbug_sentry= THD_SENTRY_GONE;
 #endif  
@@ -551,7 +551,7 @@ void add_to_status(STATUS_VAR *to_var, STATUS_VAR *from_var)
 void THD::awake(THD::killed_state state_to_set)
 {
   THD_CHECK_SENTRY(this);
-  safe_mutex_assert_owner(&LOCK_delete); 
+  safe_mutex_assert_owner(&LOCK_thd_data);
 
   killed= state_to_set;
   if (state_to_set != THD::KILL_QUERY)
@@ -895,7 +895,7 @@ int THD::send_explain_fields(select_result *result)
 void THD::close_active_vio()
 {
   DBUG_ENTER("close_active_vio");
-  safe_mutex_assert_owner(&LOCK_delete); 
+  safe_mutex_assert_owner(&LOCK_thd_data);
 #ifndef EMBEDDED_LIBRARY
   if (active_vio)
   {
@@ -2323,6 +2323,25 @@ void THD::restore_sub_statement_state(Sub_statement_state *backup)
 }
 
 
+void THD::set_statement(Statement *stmt)
+{
+  pthread_mutex_lock(&LOCK_thd_data);
+  Statement::set_statement(stmt);
+  pthread_mutex_unlock(&LOCK_thd_data);
+}
+
+
+/** Assign a new value to thd->query.  */
+
+void THD::set_query(char *query_arg, uint32 query_length_arg)
+{
+  pthread_mutex_lock(&LOCK_thd_data);
+  query= query_arg;
+  query_length= query_length_arg;
+  pthread_mutex_unlock(&LOCK_thd_data);
+}
+
+
 /**
   Mark transaction to rollback and mark error as fatal to a sub-statement.