**Reported in Launchpad by Laurynas Biveinis last update 30-11-2017 13:44:09

Spotted over at MariaDB:

https://github.com/MariaDB/server/pull/413

diff --git a/sql/threadpool_unix.cc b/sql/threadpool_unix.cc
index 6075c758e405..0ffe08a80518 100644
— a/sql/threadpool_unix.cc
+++ b/sql/threadpool_unix.cc
@@ -979,24 +979,26 @@ static void thread_group_close(thread_group_t *thread_group)

if (pipe(thread_group->shutdown_pipe))
{

• DBUG_VOID_RETURN;
  + goto end;
  }

/* Wake listener */
if (io_poll_associate_fd(thread_group->pollfd,
thread_group->shutdown_pipe[0], NULL))
{

• DBUG_VOID_RETURN;
  + goto end;
  + }
  + {
  + char c= 0;
  + if (write(thread_group->shutdown_pipe[1], &c, 1) < 0)
  + goto end;
  }

• char c= 0;

• if (write(thread_group->shutdown_pipe[1], &c, 1) < 0)

• DBUG_VOID_RETURN;
  -
  /* Wake all workers. */
  while(wake_thread(thread_group) == 0)
  {
  }

+end:
mysql_mutex_unlock(&thread_group->mutex);

DBUG_VOID_RETURN;