snapshot(ticdc): fix ddl puller and ddl manager stuck caused by dead lock

[wlwilliamx]

What problem does this PR solve?

Issue Number: close #11884

What is changed and how it works?

Summary

This PR fixes a deadlock issue in the Snapshot implementation:

Deadlock in Recursive Read Locking: Although Go’s sync.RWMutex allows recursive read locks, they can result in deadlocks if a write lock is requested during the recursive read lock execution. This blocks the outer read lock from releasing, preventing the write lock from proceeding.

This PR refactors lock usage patterns to avoid recursive read locking.

---

Root Causes of the Deadlocks

Recursive Read Lock Issue

Recursive calls involving RWMutex.RLock() can result in deadlocks when a write lock is requested during the recursive read lock execution. This behavior arises because Go’s sync.RWMutex prioritizes write locks over read locks.

Here is an example that illustrates the problem:

func (s *Snapshot) Operation() {
    s.rwlock.RLock()
    defer s.rwlock.RUnlock()
    s.NestedOperation() // Second RLock
}

func (s *Snapshot) NestedOperation() {
    s.rwlock.RLock()
    defer s.rwlock.RUnlock()
    // Perform some operations
}

If a write lock is requested while NestedOperation is executing, the following chain of events occurs:

1. The write lock request blocks new readers, including the recursive RLock in NestedOperation.
2. NestedOperation cannot complete until its RLock is granted.
3. The first RLock in Operation cannot release until NestedOperation completes.
4. Deadlock occurs because the first RLock and the recursive RLock are mutually dependent.

Check List

Tests

• Unit test
• Integration test

Questions

Will it cause performance regression or break compatibility?

No.

Do you need to update user documentation, design documentation or monitoring documentation?

No.

Release note

None.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: 3AceShowHand, CharlesCheung96

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-12-16 10:33:56.033692121 +0000 UTC m=+866626.122494663: ☑️ agreed by 3AceShowHand.
• 2024-12-16 10:59:02.014033006 +0000 UTC m=+868132.102835545: ☑️ agreed by CharlesCheung96.

[wlwilliamx]

/test cdc-integration-pulsar-test

[wlwilliamx]

/retest

[fubinzh]

/cherry-pick release-8.5
/cherry-pick release-7.5

[ti-chi-bot]

@fubinzh: new pull request created to branch release-7.5: #11887.

In response to this:

/cherry-pick release-8.5
/cherry-pick release-7.5

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[ti-chi-bot]

@fubinzh: new pull request created to branch release-8.5: #11888.

In response to this:

/cherry-pick release-8.5
/cherry-pick release-7.5

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.

[fubinzh]

/cherry-pick release-8.1

[ti-chi-bot]

@fubinzh: new pull request created to branch release-8.1: #11889.

In response to this:

/cherry-pick release-8.1

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #11896.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #11897.

[ti-chi-bot]

@wlwilliamx: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-cdc-integration-kafka-test	d17865a	link	unknown	/test cdc-integration-kafka-test
pull-cdc-integration-pulsar-test	d17865a	link	true	/test cdc-integration-pulsar-test

Full PR test history. Your PR dashboard.

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