Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1. Create 100M table using sysbench.
2. Add index for the column c(char(120)).
3. Run admin cancel ddl jobs.
4. TiDB DDL hangs.

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

The adding index job should be able to cancel.

3. What did you see instead (Required)

TiDB keeps report "[ddl] run the cancelling DDL job" constantly.

4. What is your TiDB version? (Required)

d2ace99