Pessimistic locks are left after the session gets killed

[zyguan]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

• start a transaction and lock a key

  create table t (id int primary key, c int);
  insert into t values (1, 1), (2, 2), (3, 3);
  begin;
  select * from t where id = 1 for update;

• kill the above session by kill <id>
• query the mvcc info of the key

  curl 127.0.0.1:10080/mvcc/key/test/t/1

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

the pessimistic lock should be rollbacked.

3. What did you see instead (Required)

the pessimistic lock was left because rollbackPessimisticLocks failed due to the kill flag.

$ curl 127.0.0.1:10080/mvcc/key/test/t/1
{
 "key": "7480000000000000705F728000000000000001",
 "region_id": 22,
 "value": {
  "info": {
   "lock": {
    "type": 5,
    "start_ts": 458469322054434817,
    "primary": "dIAAAAAAAABwX3KAAAAAAAAAAQ==",
    "last_change_ts": 458469321360015362,
    "versions_to_last_change": 1
   },
   "writes": [
    {
     "start_ts": 458469321360015361,
     "commit_ts": 458469321360015362,
     "short_value": "gAABAAAAAgEACg=="
    }
   ]
  }
 }
}

4. What is your TiDB version? (Required)

master

[jebter]

@cfzjywxk PTAL

[cfzjywxk]

It is possbly a historical issue of KiLL statement feature, @zyguan please label the affected versions, the severity could be moderate I think.