Debugger: Fix deadlock on Windows

[zaddach]

The debugger locks the breakpoint list before calling the breakpoint handler, and only releases the lock after the call has been issued. On Windows, this makes it impossible to add/delete breakpoints when the debugger broke at a breakpoint (see #1071). This PR fixes the issue by releasing the breakpoint list lock before calling the breakpoint handler.

Summary by CodeRabbit

• Refactor
  • Improved code readability in debugger context handling
  • Restructured internal logic for breakpoint checks

[coderabbitai]

Walkthrough

The pull request involves a refactoring of the handle method in the DebuggerContext struct within the debugger/src/lib.rs file. The primary change is a code restructuring that separates the mutex locking and rule presence check into distinct steps, improving code readability without altering the underlying functionality or behavior of the debugger's event handling mechanism.

Changes

File	Change Summary
debugger/src/lib.rs	Refactored handle method to separate mutex locking and breakpoint rule presence check into distinct code blocks

Poem

🐰 A Debugger's Dance of Code

With mutex unlocked and logic refined,
A rabbit's touch, the code redesigned
Clarity springs where complexity grew
Readability blooms, a programmer's view
Elegance hops through each careful line 🔍

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📜 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 24d0d9c and 758d9cc.

📒 Files selected for processing (1)

• debugger/src/lib.rs (1 hunks)

🔇 Additional comments (1)

debugger/src/lib.rs (1)

256-261: LGTM! The deadlock fix looks correct.

The changes properly scope the mutex lock to release it before sending the event and parking the thread, which fixes the deadlock issue when adding/removing breakpoints during debugging.

Consider documenting the thread safety considerations.

Adding a comment explaining why the lock is released before sending the event would help future maintainers understand the deadlock prevention mechanism.

     let contains_rule = {
+        // Release the breakpoints lock before sending the event to prevent deadlocks
+        // when adding/removing breakpoints while the debugger is paused
         let lock = breakpoints.lock().expect(POISONED_LOCK_PANIC);
         lock.contains(&rule)
     };

Verify thread safety of the implementation.

Let's verify that releasing the lock early doesn't introduce race conditions:

✅ Verification successful

Thread safety verification completed - Implementation is correct

The implementation is properly synchronized with consistent mutex locking patterns throughout the codebase. All breakpoint accesses are protected by locks, and the early lock release in the reviewed code is safe as it maintains the invariant that breakpoint modifications always occur under mutex protection.

🏁 Scripts executed

The following scripts were executed for the analysis:

Script:

#!/bin/bash
# Description: Check for potential race conditions in breakpoint handling
# Look for other places where breakpoints are accessed without proper synchronization

# Search for direct access to breakpoints
rg -n 'breakpoints\.' debugger/src/lib.rs

# Search for mutex operations on breakpoints
rg -n 'breakpoints.*lock\(\)' debugger/src/lib.rs

# Search for potential concurrent modifications
ast-grep --pattern 'breakpoints.lock()'

Length of output: 1880

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[tomtau]

lgtm, thanks!