fix: remove unnecessary lock in bad sources processing

[PastaPastaPasta]

Issue being fixed or feature implemented

What was done?

How Has This Been Tested?

Breaking Changes

Checklist:

Go over all the following points, and put an x in all the boxes that apply.

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional/e2e tests
• I have made corresponding changes to the documentation
• I have assigned this pull request to a milestone (for repository code-owners and collaborators only)

[github-actions]

⚠️ Potential Merge Conflicts Detected

This PR has potential conflicts with the following open PRs:

• refactor: separate network and consensus logic 1/N [instantsend] #6959 - refactor: separate network and consensus logic 1/N [instantsend]

Please coordinate with the authors of these PRs to avoid merge conflicts.

[coderabbitai]

Walkthrough

This change removes an explicit LOCK(::cs_main) acquisition from the ban-handling path in ProcessPendingInstantSendLocks. Previously, when processing bad sources during ISLOCK batch verification, the code explicitly acquired the cs_main lock before iterating through batchVerifier.badSources and flagging peers with MisbehavingError. This lock acquisition has been removed, reducing the critical section scope during ban operations while peer notification and bad source handling remain functionally unchanged.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~15 minutes

• Key area requiring attention: Verification that cs_main was not protecting critical state during the removed lock scope, or that the caller already holds the lock
• Concurrency implications should be validated to ensure no race conditions are introduced by narrowing the lock scope

Pre-merge checks and finishing touches

❌ Failed checks (1 inconclusive)

Check name	Status	Explanation	Resolution
Description check	❓ Inconclusive	The description contains only empty template sections with no actual content explaining the issue, implementation, testing approach, or breaking changes.	Provide concrete details about why the lock was unnecessary, how it was tested, and confirm there are no breaking changes or side effects from the lock removal.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: removing an unnecessary lock in bad sources processing during ISLOCK handling.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

---

📜 Recent review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between d3fa315 and cb1dfa3.

📒 Files selected for processing (1)

• src/instantsend/instantsend.cpp (0 hunks)

💤 Files with no reviewable changes (1)

• src/instantsend/instantsend.cpp

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (10)

• GitHub Check: linux64_nowallet-build / Build source
• GitHub Check: win64-build / Build source
• GitHub Check: mac-build / Build source
• GitHub Check: linux64_tsan-build / Build source
• GitHub Check: linux64_ubsan-build / Build source
• GitHub Check: linux64_sqlite-build / Build source
• GitHub Check: linux64_fuzz-build / Build source
• GitHub Check: linux64-build / Build source
• GitHub Check: arm-linux-build / Build source
• GitHub Check: Lint / Run linters

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[knst]

LGTM cb1dfa3

consider #6959 to get merged first