*: add a reference count for StmtCtx

[XuHuaiyu]

What problem does this PR solve?

Issue Number: close #27725

Problem Summary:

What is changed and how it works?

Check List

Tests

• Manual test (add detailed scripts or steps below)
  Using commit: 17e6297
  run

select 1;
select sleep(3);
select 1;
select 1;

Before this commit, tidb-server will panic.
After this commit, tidb-server run successfully.

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• windtalker
• wshwsh12

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[windtalker]

Don't need to update info here?

[windtalker]

So other threads can only access StmtCtx by this method?

[XuHuaiyu]

I'm not sure. But it seems we only encounter problems here.😅

[hawkingrei]

@XuHuaiyu PTAL

panic: runtime error: invalid memory address or nil pointer dereference [recovered]
	panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x4aa405]

goroutine 130 [running]:
testing.tRunner.func1.2({0x1ac2d80, 0x3047a00})
	GOROOT/src/testing/testing.go:1396 +0x372
testing.tRunner.func1()
	GOROOT/src/testing/testing.go:1399 +0x5f0
panic({0x1ac2d80, 0x3047a00})
	GOROOT/src/runtime/panic.go:890 +0x262
sync/atomic.LoadInt32()
	src/runtime/race_amd64.s:202 +0xc
github.com/pingcap/tidb/sessionctx/stmtctx.(*ReferenceCount).TryIncrease(0x0?)
	sessionctx/stmtctx/stmtctx.go:118 +0x45
github.com/pingcap/tidb/util.GenLogFields(0x0, 0xc0001a37a0, 0x0)
	util/util.go:109 +0xa5
github.com/pingcap/tidb/util/memoryusagealarm.(*memoryUsageAlarm).getTop10SqlInfo(0xc000611cd0, 0x0?, {0xc00059a798?, 0x3, 0x3})
	util/memoryusagealarm/memoryusagealarm.go:274 +0x2d4
github.com/pingcap/tidb/util/memoryusagealarm.(*memoryUsageAlarm).getTop10SqlInfoByMemoryUsage(0xc00080bb70?, {0xc00059a798, 0x3, 0x3})
	util/memoryusagealarm/memoryusagealarm.go:304 +0x67
github.com/pingcap/tidb/util/memoryusagealarm.TestGetTop10Sql(0x0?)
	util/memoryusagealarm/memoryusagealarm_test.go:87 +0x205
testing.tRunner(0xc000603040, 0x1d17040)
	GOROOT/src/testing/testing.go:1446 +0x217
created by testing.(*T).Run
	GOROOT/src/testing/testing.go:1493 +0x75e

[XuHuaiyu]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: b9f9e37

[qw4990]

/merge

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #39424.

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #39425.

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #39426.

[sre-bot]

TiDB MergeCI notify

✅ Well Done! New fixed [1] after this pr merged.

CI Name	Result	Duration	Compare with Parent commit
idc-jenkins-ci-tidb/integration-ddl-test	✅ all 6 tests passed	5 min 10 sec	Fixed
idc-jenkins-ci-tidb/integration-common-test	🟢 all 17 tests passed	26 min	Existing passed
idc-jenkins-ci/integration-cdc-test	🟢 all 40 tests passed	23 min	Existing passed
idc-jenkins-ci-tidb/common-test	🟢 all 11 tests passed	9 min 22 sec	Existing passed
idc-jenkins-ci-tidb/tics-test	🟢 all 1 tests passed	6 min 12 sec	Existing passed
idc-jenkins-ci-tidb/mybatis-test	🟢 all 1 tests passed	5 min 50 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-2	🟢 all 28 tests passed	5 min 20 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-1	🟢 all 26 tests passed	4 min 22 sec	Existing passed
idc-jenkins-ci-tidb/integration-compatibility-test	🟢 all 1 tests passed	2 min 50 sec	Existing passed
idc-jenkins-ci-tidb/plugin-test	🟢 build success, plugin test success	4min	Existing passed