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Move all kill mutex protection to LOCK_thd_kill

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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

65
sql/sql_show.cc
View File

@ -2578,23 +2578,28 @@ static const char *thread_state_info(THD *tmp)
{
if (tmp->net.reading_or_writing == 2)
return "Writing to net";
else if (tmp->get_command() == COM_SLEEP)
if (tmp->get_command() == COM_SLEEP)
return "";
else
return "Reading from net";
return "Reading from net";
}
else
#endif
if (tmp->proc_info)
return tmp->proc_info;
/* Check if we are waiting on a condition */
if (!trylock_short(&tmp->LOCK_thd_kill))
{
if (tmp->proc_info)
return tmp->proc_info;
else if (tmp->mysys_var && tmp->mysys_var->current_cond)
/* mysys_var is protected by above mutex */
bool cond= tmp->mysys_var && tmp->mysys_var->current_cond;
mysql_mutex_unlock(&tmp->LOCK_thd_kill);
if (cond)
return "Waiting on cond";
else
return NULL;
}
return NULL;
}
void mysqld_list_processes(THD *thd,const char *user, bool verbose)
{
Item *field;
@ -2657,8 +2662,7 @@ void mysqld_list_processes(THD *thd,const char *user, bool verbose)
while ((tmp=it++))
{
Security_context *tmp_sctx= tmp->security_ctx;
struct st_my_thread_var *mysys_var= 0;
bool got_thd_data, got_mysys_lock= 0;
bool got_thd_data;
if ((tmp->vio_ok() || tmp->system_thread) &&
(!user || (!tmp->system_thread &&
tmp_sctx->user && !strcmp(tmp_sctx->user, user))))
@ -2684,17 +2688,10 @@ void mysqld_list_processes(THD *thd,const char *user, bool verbose)
thd_info->command=(int) tmp->get_command();
if ((got_thd_data= !trylock_short(&tmp->LOCK_thd_data)))
if ((mysys_var= tmp->mysys_var))
got_mysys_lock= !trylock_short(&mysys_var->mutex);
if (got_thd_data)
{
/* This is correct under mysys_lock, otherwise an approximation */
/* This is an approximation */
thd_info->proc_info= (char*) (tmp->killed >= KILL_QUERY ?
"Killed" : 0);
if (got_mysys_lock)
mysql_mutex_unlock(&mysys_var->mutex);
/*
The following variables are only safe to access under a lock
*/
@ -2952,13 +2949,13 @@ int fill_show_explain(THD *thd, TABLE_LIST *table, COND *cond)
tmp_sctx->user)))
{
my_error(ER_SPECIFIC_ACCESS_DENIED_ERROR, MYF(0), "PROCESS");
mysql_mutex_unlock(&tmp->LOCK_thd_data);
mysql_mutex_unlock(&tmp->LOCK_thd_kill);
DBUG_RETURN(1);
}
if (tmp == thd)
{
mysql_mutex_unlock(&tmp->LOCK_thd_data);
mysql_mutex_unlock(&tmp->LOCK_thd_kill);
my_error(ER_TARGET_NOT_EXPLAINABLE, MYF(0));
DBUG_RETURN(1);
}
@ -2966,7 +2963,7 @@ int fill_show_explain(THD *thd, TABLE_LIST *table, COND *cond)
bool bres;
/*
Ok we've found the thread of interest and it won't go away because
we're holding its LOCK_thd data. Post it a SHOW EXPLAIN request.
we're holding its LOCK_thd_kill. Post it a SHOW EXPLAIN request.
*/
bool timed_out;
int timeout_sec= 30;
@ -3059,10 +3056,9 @@ int fill_schema_processlist(THD* thd, TABLE_LIST* tables, COND* cond)
while ((tmp= it++))
{
Security_context *tmp_sctx= tmp->security_ctx;
struct st_my_thread_var *mysys_var= 0;
const char *val, *db;
ulonglong max_counter;
bool got_thd_data, got_mysys_lock= 0;
bool got_thd_data;
if ((!tmp->vio_ok() && !tmp->system_thread) ||
(user && (tmp->system_thread || !tmp_sctx->user ||
@ -3090,10 +3086,6 @@ int fill_schema_processlist(THD* thd, TABLE_LIST* tables, COND* cond)
strlen(tmp_sctx->host_or_ip), cs);
if ((got_thd_data= !trylock_short(&tmp->LOCK_thd_data)))
if ((mysys_var= tmp->mysys_var))
got_mysys_lock= !trylock_short(&mysys_var->mutex);
if (got_thd_data)
{
/* DB */
if ((db= tmp->db))
@ -3112,9 +3104,6 @@ int fill_schema_processlist(THD* thd, TABLE_LIST* tables, COND* cond)
table->field[4]->store(command_name[tmp->get_command()].str,
command_name[tmp->get_command()].length, cs);
if (got_mysys_lock)
mysql_mutex_unlock(&mysys_var->mutex);
/* MYSQL_TIME */
ulonglong utime= tmp->start_utime;
ulonglong utime_after_query_snapshot= tmp->utime_after_query;
@ -3124,13 +3113,6 @@ int fill_schema_processlist(THD* thd, TABLE_LIST* tables, COND* cond)
table->field[5]->store(utime / HRTIME_RESOLUTION, TRUE);
/* STATE */
if ((val= thread_state_info(tmp)))
{
table->field[6]->store(val, strlen(val), cs);
table->field[6]->set_notnull();
}
if (got_thd_data)
{
if (tmp->query())
@ -3162,6 +3144,13 @@ int fill_schema_processlist(THD* thd, TABLE_LIST* tables, COND* cond)
mysql_mutex_unlock(&tmp->LOCK_thd_data);
}
/* STATE */
if ((val= thread_state_info(tmp)))
{
table->field[6]->store(val, strlen(val), cs);
table->field[6]->set_notnull();
}
/* TIME_MS */
table->field[8]->store((double)(utime / (HRTIME_RESOLUTION / 1000.0)));