*: fix data race in the ReuseChunkPool

[hawkingrei]

What problem does this PR solve?

Issue Number: close #46282

Problem Summary:

What is changed and how it works?

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

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

[codecov]

Codecov Report

Merging #46283 (771e042) into master (94cfa8b) will decrease coverage by 0.6692%.
Report is 1 commits behind head on master.
The diff coverage is 100.0000%.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #46283        +/-   ##
================================================
- Coverage   73.3694%   72.7002%   -0.6692%     
================================================
  Files          1285       1306        +21     
  Lines        394832     401026      +6194     
================================================
+ Hits         289686     291547      +1861     
- Misses        86684      90957      +4273     
- Partials      18462      18522        +60     

Flag	Coverage Δ
integration	25.5638% <100.0000%> (?)
unit	73.3809% <100.0000%> (+0.0115%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	54.0444% <ø> (ø)
parser	85.0667% <ø> (ø)
br	47.8811% <ø> (-4.3469%)	⬇️

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[tiancaiamao]

From the calling stack, you can infer that the same session is used by different goroutine, that's the root cause of the data race.
So a real fix should fix the test case to avoid that misusage, rather than add a mutex blindly.

[easonn7]

/approve

there is no variable change in this PR, LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cfzjywxk, easonn7, qw4990

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• sessionctx/variable/OWNERS [easonn7]

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[tiancaiamao]

tidb/ddl/ingest/integration_test.go

Lines 44 to 48 in 9411e82

	ingest.LitBackCtxMgr = ingest.NewMockBackendCtxMgr(func() sessionctx.Context {
	tk.MustExec("rollback;")
	tk.MustExec("begin;")
	return tk.Session()
	})

Return this session for several goroutines to use is unsafe.

[tiancaiamao]

/hold

[hawkingrei]

/hold