Fix potential data race in DynamicThreadPool

[fuzhe1989]

Signed-off-by: fuzhe1989 [email protected]

What problem does this PR solve?

Issue Number: close #4595

Problem Summary:

DynamicThreadPool relies on a counter to detect if all dynamic threads end, until when it can safely destruct.

Previously the last instruction of DynamicThreadPool::dynamicWork is exactly the counter's decrement. This is an implicit contract.

However after #4169 for recording thread-related metrics, UPDATE_CUR_AND_MAX_METRIC was added. It contains a SCOPE_EXIT which will run after the counter's decrement and break the implicit contract.

This introduces a risk that the main thread may find the counter is 0 and exit (and destruct all static variables like TiFlashMetric), however the dynamic threads do not really exit and try to visit TiFlashMetric.

What is changed and how it works?

Wrap the body of DynamicThreadPool::dynamicWork into a code block to ensure the decrement of counter is the last instruction.

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

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• SeaRise
• bestwoody

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[fuzhe1989]

/check-issue-triage-complete

[fuzhe1989]

/run-sanitizer-test tsan

[fuzhe1989]

/run-all-tests

[bestwoody]

lgtm

[fuzhe1989]

/merge

[ti-chi-bot]

@fuzhe1989: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

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[ti-chi-bot]

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

Commit hash: 6604173

[sre-bot]

Coverage for changed files

Filename                                                                                             Regions    Missed Regions     Cover   Functions  Missed Functions  Executed       Lines      Missed Lines     Cover    Branches   Missed Branches     Cover
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
/home/jenkins/agent/workspace/tiflash-build-common/tiflash/dbms/src/Common/DynamicThreadPool.cpp          79                 1    98.73%          10                 0   100.00%          98                 1    98.98%          24                 1    95.83%
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                                                                                                     79                 1    98.73%          10                 0   100.00%          98                 1    98.98%          24                 1    95.83%

Coverage summary

Functions  MissedFunctions  Executed  Lines   MissedLines  Cover
17024      9512             44.13%    191878  96457        49.73%

full coverage report (for internal network access only)

[sre-bot]

Coverage for changed files

Filename                                                                                             Regions    Missed Regions     Cover   Functions  Missed Functions  Executed       Lines      Missed Lines     Cover    Branches   Missed Branches     Cover
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
/home/jenkins/agent/workspace/tiflash-build-common/tiflash/dbms/src/Common/DynamicThreadPool.cpp          79                 1    98.73%          10                 0   100.00%          98                 1    98.98%          24                 1    95.83%
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                                                                                                     79                 1    98.73%          10                 0   100.00%          98                 1    98.98%          24                 1    95.83%

Coverage summary

Functions  MissedFunctions  Executed  Lines   MissedLines  Cover
17024      9512             44.13%    191878  96459        49.73%

full coverage report (for internal network access only)

[Benjamin2037]

/run-sanitizer-test tsan