1 files changed, 10 insertions, 1 deletions
diff --git a/sql/rpl_parallel.cc b/sql/rpl_parallel.cc
index 973b9d899c1..34f9113f7fe 100644
--- a/sql/rpl_parallel.cc
+++ b/sql/rpl_parallel.cc
@@ -1623,10 +1623,19 @@ int rpl_parallel_resize_pool_if_no_slaves(void)
 }
 
 
+/**
+   Resize pool if not active or busy (in which case we may be in
+   resize to 0
+*/
+
 int
 rpl_parallel_activate_pool(rpl_parallel_thread_pool *pool)
 {
-  if (!pool->count)
+  bool resize;
+  mysql_mutex_lock(&pool->LOCK_rpl_thread_pool);
+  resize= !pool->count || pool->busy;
+  mysql_mutex_unlock(&pool->LOCK_rpl_thread_pool);
+  if (resize)
     return rpl_parallel_change_thread_count(pool, opt_slave_parallel_threads,
                                             0);
   return 0;