store: unistore will hang over in some case.

[AilinKid]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

https://github.com/pingcap/automated-tests/pull/658/files

start local tidb
cd ticase/column_type_change
go build
./column_type_change run -i suite.jsonnet TICASE-4941

The related goroutine
tidb_debug_20210506140729.zip

I've tested it with a real tikv, it works.

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

Test success.

3. What did you see instead (Required)

The test hangs over, do did the TiDB

4. What is your TiDB version? (Required)

master <commit 207ce34 >

[tiancaiamao]

That's weird... from the goroutine stack, the code seems blocked in bager engine... it might happen when the runFlushMemTable goroutine exit exceptionally.

Can it reproduce?

[zyguan]

No update for a long time, feel free to reopen it if the issue still exists.

[github-actions]

Please check whether the issue should be labeled with 'affects-x.y' or 'fixes-x.y.z', and then remove 'needs-more-info' label.

[tiancaiamao]

The data race might be a possible reason... concurrent write breaks unistore and make it hang #26832