1 files changed, 22 insertions, 3 deletions
diff --git a/sql/rpl_parallel.cc b/sql/rpl_parallel.cc
index 35cddee6d4d..8fef2d66635 100644
--- a/sql/rpl_parallel.cc
+++ b/sql/rpl_parallel.cc
@@ -1617,13 +1617,32 @@ int rpl_parallel_resize_pool_if_no_slaves(void)
 }
 
 
+/**
+  Pool activation is preceeded by taking a "lock" of pool_mark_busy
+  which guarantees the number of running slaves drops to zero atomicly
+  with the number of pool workers.
+  This resolves race between the function caller thread and one
+  that may be attempting to deactivate the pool.
+*/
 int
 rpl_parallel_activate_pool(rpl_parallel_thread_pool *pool)
 {
+  int rc= 0;
+
+  if ((rc= pool_mark_busy(pool, current_thd)))
+    return rc;   // killed
+
   if (!pool->count)
-    return rpl_parallel_change_thread_count(pool, opt_slave_parallel_threads,
-                                            0);
-  return 0;
+  {
+    pool_mark_not_busy(pool);
+    rc= rpl_parallel_change_thread_count(pool, opt_slave_parallel_threads,
+                                         0);
+  }
+  else
+  {
+    pool_mark_not_busy(pool);
+  }
+  return rc;
 }