# fatal error: sync: RUnlock of unlocked RWMutex

- **ID:** `go/sync-rwmutex-unlock-of-unlocked`
- **Domain:** go
- **Category:** runtime_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

RWMutex.RUnlock() is called without a matching RLock(). Often due to mismatched Lock/RLock in different code paths.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 1.x | active | — | — |

## Workarounds

1. **** (95% success)
   ```
   func (s *Store) Get(k string) (int, bool) {
    s.mu.RLock()
    defer s.mu.RUnlock()
    v, ok := s.m[k]
    return v, ok
}
   ```
2. **** (90% success)
   ```
   func (s *Store) read(fn func()) {
    s.mu.RLock()
    defer s.mu.RUnlock()
    fn()
}
   ```

## Dead Ends

- **** — Loses read concurrency and does not fix the mismatch if the bug is elsewhere. (65% fail)
- **** — Fatal error; not recoverable. (100% fail)