hujun260 opened a new pull request, #18219:
URL: https://github.com/apache/nuttx/pull/18219
## Summary
This series contains three related improvements to the reader-writer
semaphore
implementation for MISRA HIS compliance:
1. Consolidate return statements in `down_read_trylock()` with single exit
point
2. Eliminate goto statements in `down_read()` with structured control flow
3. Consolidate return statements in `init_rwsem()` with inverted conditions
## Motivation and Problem
### Part 1: down_read_trylock() RETURN Consolidation
Multiple return statements violate MISRA HIS rules. This change consolidates
returns and replaces goto with if-else blocks for better code clarity.
### Part 2: down_read() HIS_GOTO Elimination
Goto statements violate MISRA HIS safety standards. Structured if-else blocks
improve verifiability and maintain better code flow.
### Part 3: init_rwsem() RETURN Consolidation
Multiple error handling paths with early returns violate MISRA HIS standards.
Inverting conditions improves code structure and compliance.
## Changes
### Commit 1: down_read_trylock()
- Introduce result variable `ret` initialized to 1 (success)
- Replace goto with if-else-else structure
- Replace early return with `ret = 0` assignment
- Single exit point with centralized return
### Commit 2: down_read()
- Replace goto label with if-else structure
- Move writer wait loop into else block
- Move reader increment into nested structure
- Eliminate out: label and goto statements
### Commit 3: init_rwsem()
- Invert error conditions (ret < 0 becomes ret >= 0)
- Consolidate nested initialization into nested if blocks
- Replace multiple early returns with single exit
- Introduce result variable for proper error propagation
## Impact
- **MISRA Compliance**: Achieves HIS_RETURN and HIS_GOTO compliance metrics
- **Code Quality**: Reduced cyclomatic complexity and improved readability
- **Verifiability**: Single exit points improve static analysis capabilities
- **Maintainability**: Structured control flow easier to understand and
modify
- **Backward Compatibility**: No functional changes; identical runtime
behavior
- **Performance**: No performance impact; compiler optimizations identical
## Verification
- [x] Code compiles without warnings on ARM GCC 10.x
- [x] Verified on QEMU ARMv7-A simulator
- [x] Reader-writer semaphore operations verified:
- Read lock acquisition (try and blocking)
- Write lock acquisition and holder detection
- Semaphore initialization with error handling
- [x] All control flow paths verified
- [x] Static analysis shows improved compliance metrics
## Testing
Tested with:
- ARM GCC 10.x compiler
- QEMU ARMv7-A simulation
- Reader-writer semaphore scenarios:
- down_read_trylock() with holder self-detection
- down_read_trylock() with existing writer
- down_read() blocking on writer
- init_rwsem() successful initialization
- init_rwsem() error handling paths
## Related Issues
Addresses Coverity static analysis HIS_metric_violation findings:
- HIS_metric_violation(RETURN) in multiple functions
- HIS_metric_violation(HIS_GOTO) in control flow
## Files Changed
- `sched/semaphore/sem_rw.c` (85 lines total across 3 commits)
- Commit 1: 25 lines (12 insertions, 13 deletions)
- Commit 2: 28 lines (14 insertions, 14 deletions)
- Commit 3: 32 lines (16 insertions, 16 deletions)
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