Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1.Do a lot of querys.
2.Cancel that querys.
3.Repeat step1、2.

2. What did you expect to see? (Required)

Thread of Exchange task exit.

3. What did you see instead (Required)

Thread of Exchange task didn't exit.

4. What is your TiFlash version? (Required)

v6.0.0 alpha