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Move all kill mutex protection to LOCK_thd_kill

Browse Source 
LOCK_thd_data was used to protect both THD data and
ensure that the THD is not deleted while it was in use

This patch moves the THD delete protection to LOCK_thd_kill,
which already protects the THD for kill.

The benefits are:
- More well defined what LOCK_thd_data protects
- LOCK_thd_data usage is now much simpler and easier to verify
- Less chance of deadlocks in SHOW PROCESS LIST as there is less
  chance of interactions between mutexes
- Remove not needed LOCK_thread_count from
  thd_get_error_context_description()
- Fewer mutex taken for thd->awake()

Other things:
- Don't take mysys->var mutex in show processlist to check if thread
  is kill marked
- thd->awake() now automatically takes the LOCK_thd_kill mutex
  (Simplifies code)
- Apc uses LOCK_thd_kill instead of LOCK_thd_data
This commit is contained in:
Monty
2017-12-07 21:28:00 +02:00
parent 3574f9c7bc
commit c2118a08b1
15 changed files with 109 additions and 120 deletions
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4
sql/mysqld.cc
View File

@ -1704,7 +1704,7 @@ static void close_connections(void)
#endif
tmp->set_killed(KILL_SERVER_HARD);
MYSQL_CALLBACK(thread_scheduler, post_kill_notification, (tmp));
mysql_mutex_lock(&tmp->LOCK_thd_data);
mysql_mutex_lock(&tmp->LOCK_thd_kill);
if (tmp->mysys_var)
{
tmp->mysys_var->abort=1;
@ -1727,7 +1727,7 @@ static void close_connections(void)
}
mysql_mutex_unlock(&tmp->mysys_var->mutex);
}
mysql_mutex_unlock(&tmp->LOCK_thd_data);
mysql_mutex_unlock(&tmp->LOCK_thd_kill);
}
mysql_mutex_unlock(&LOCK_thread_count); // For unlink from list