diff options
Diffstat (limited to 'sql/sql_show.cc')
| -rw-r--r-- | sql/sql_show.cc | 45 |
1 files changed, 37 insertions, 8 deletions
diff --git a/sql/sql_show.cc b/sql/sql_show.cc index 18b7e92bca5..bbe217c44d3 100644 --- a/sql/sql_show.cc +++ b/sql/sql_show.cc @@ -2556,6 +2556,28 @@ public: double progress; }; +/** + Try to lock a mutex, but give up after a short while to not cause deadlocks + + The loop is short, as the mutex we are trying to lock are mutex the should + never be locked a long time, just over a few instructions. + + @return 0 ok + @return 1 error +*/ + +static bool trylock_short(mysql_mutex_t *mutex) +{ + uint i; + for (i= 0 ; i < 100 ; i++) + { + if (!mysql_mutex_trylock(mutex)) + return 0; + LF_BACKOFF(); + } + return 1; +} + static const char *thread_state_info(THD *tmp) { #ifndef EMBEDDED_LIBRARY @@ -2574,10 +2596,17 @@ static const char *thread_state_info(THD *tmp) #endif if (tmp->proc_info) return tmp->proc_info; - else if (tmp->mysys_var && tmp->mysys_var->current_cond) - return "Waiting on cond"; - else - return NULL; + + /* Check if we are waiting on a condition */ + if (!trylock_short(&tmp->LOCK_thd_kill)) + { + /* 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"; + } + return NULL; } void mysqld_list_processes(THD *thd,const char *user, bool verbose) @@ -2921,13 +2950,13 @@ 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); } @@ -2935,7 +2964,7 @@ 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; @@ -2949,7 +2978,7 @@ int fill_show_explain(THD *thd, TABLE_LIST *table, COND *cond) explain_req.request_thd= thd; explain_req.failed_to_produce= FALSE; - /* Ok, we have a lock on target->LOCK_thd_data, can call: */ + /* Ok, we have a lock on target->LOCK_thd_kill, can call: */ bres= tmp->apc_target.make_apc_call(thd, &explain_req, timeout_sec, &timed_out); if (bres || explain_req.failed_to_produce) |