MDEV-23328 Server hang due to Galera lock conflict resolution

Cherry-pick the sql_kill and sql_user_kill from ef2dbb8d

Changed ER_CANNOT_USER to ER_KILL_DENIED_ERROR to match
other kill denied user messages.

Cherry-pick by Daniel Black.
Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>

sql/sql_parse.cc

@@ -9203,6 +9203,7 @@ THD *find_thread_by_id(longlong id, bool query_id)
   return arg.thd;
 }
 
+
 /**
   kill one thread.
 
@@ -9246,7 +9247,8 @@ kill_one_thread(THD *thd, longlong id, killed_state kill_signal, killed_type typ
       faster and do a harder kill than KILL_SYSTEM_THREAD;
     */
 
-    mysql_mutex_lock(&tmp->LOCK_thd_data); // for various wsrep* checks below
+    mysql_mutex_lock(&tmp->LOCK_thd_data); // Lock from concurrent usage
+
 #ifdef WITH_WSREP
     if (((thd->security_ctx->master_access & PRIV_KILL_OTHER_USER_PROCESS) ||
         thd->security_ctx->user_matches(tmp->security_ctx)) &&
@@ -9261,23 +9263,23 @@ kill_one_thread(THD *thd, longlong id, killed_state kill_signal, killed_type typ
       if (tmp->wsrep_aborter && tmp->wsrep_aborter != thd->thread_id)
       {
         /* victim is in hit list already, bail out */
-	WSREP_DEBUG("victim has wsrep aborter: %lu, skipping awake()",
-                    tmp->wsrep_aborter);
+	WSREP_DEBUG("victim %lld has wsrep aborter: %lu, skipping awake()",
+		    id, tmp->wsrep_aborter);
         error= 0;
       }
       else
 #endif /* WITH_WSREP */
       {
-        WSREP_DEBUG("kill_one_thread %llu, victim: %llu wsrep_aborter %llu by signal %d",
-                    thd->thread_id, id, tmp->wsrep_aborter, kill_signal);
+        WSREP_DEBUG("kill_one_thread victim: %lld wsrep_aborter %lu by signal %d",
+                    id, tmp->wsrep_aborter, kill_signal);
         tmp->awake_no_mutex(kill_signal);
-        WSREP_DEBUG("victim: %llu taken care of", id);
         error= 0;
       }
     }
     else
       error= (type == KILL_TYPE_QUERY ? ER_KILL_QUERY_DENIED_ERROR :
                                         ER_KILL_DENIED_ERROR);
+
     mysql_mutex_unlock(&tmp->LOCK_thd_data);
   }
   mysql_mutex_unlock(&tmp->LOCK_thd_kill);
@@ -9392,6 +9394,18 @@ static
 void sql_kill(THD *thd, longlong id, killed_state state, killed_type type)
 {
   uint error;
+#ifdef WITH_WSREP
+  if (WSREP(thd))
+  {
+    WSREP_DEBUG("sql_kill called");
+    if (thd->wsrep_applier)
+    {
+      WSREP_DEBUG("KILL in applying, bailing out here");
+      return;
+    }
+    WSREP_TO_ISOLATION_BEGIN(WSREP_MYSQL_DB, NULL, NULL)
+  }
+#endif /* WITH_WSREP */
   if (likely(!(error= kill_one_thread(thd, id, state, type))))
   {
     if (!thd->killed)
@@ -9401,6 +9415,11 @@ void sql_kill(THD *thd, longlong id, killed_state state, killed_type type)
   }
   else
     my_error(error, MYF(0), id);
+#ifdef WITH_WSREP
+  return;
+ wsrep_error_label:
+  my_error(ER_KILL_DENIED_ERROR, MYF(0), (long long) thd->thread_id);
+#endif /* WITH_WSREP */
 }
 
 
@@ -9409,6 +9428,18 @@ sql_kill_user(THD *thd, LEX_USER *user, killed_state state)
 {
   uint error;
   ha_rows rows;
+#ifdef WITH_WSREP
+  if (WSREP(thd))
+  {
+    WSREP_DEBUG("sql_kill_user called");
+    if (thd->wsrep_applier)
+    {
+      WSREP_DEBUG("KILL in applying, bailing out here");
+      return;
+    }
+    WSREP_TO_ISOLATION_BEGIN(WSREP_MYSQL_DB, NULL, NULL)
+  }
+#endif /* WITH_WSREP */
   switch (error= kill_threads_for_user(thd, user, state, &rows))
   {
   case 0:
@@ -9421,6 +9452,11 @@ sql_kill_user(THD *thd, LEX_USER *user, killed_state state)
   default:
     my_error(error, MYF(0));
   }
+#ifdef WITH_WSREP
+  return;
+ wsrep_error_label:
+  my_error(ER_KILL_DENIED_ERROR, MYF(0), (long long) thd->thread_id);
+#endif /* WITH_WSREP */
 }