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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
Download Patch File Download Diff File Expand all files Collapse all files

6
sql/threadpool_common.cc
View File

@ -250,7 +250,7 @@ static THD* threadpool_add_connection(CONNECT *connect, void *scheduler_data)
}
delete connect;
add_to_active_threads(thd);
thd->mysys_var= mysys_var;
thd->set_mysys_var(mysys_var);
thd->event_scheduler.data= scheduler_data;
/* Create new PSI thread for use with the THD. */
@ -477,11 +477,11 @@ void tp_timeout_handler(TP_connection *c)
if (c->state != TP_STATE_IDLE)
return;
THD *thd=c->thd;
mysql_mutex_lock(&thd->LOCK_thd_data);
mysql_mutex_lock(&thd->LOCK_thd_kill);
thd->set_killed(KILL_WAIT_TIMEOUT);
c->priority= TP_PRIORITY_HIGH;
post_kill_notification(thd);
mysql_mutex_unlock(&thd->LOCK_thd_data);
mysql_mutex_unlock(&thd->LOCK_thd_kill);
}