hujun260 opened a new pull request, #18228:
URL: https://github.com/apache/nuttx/pull/18228
## Summary
Refactor the semaphore post slow path handler to consolidate multiple return
statements into a single exit point. The implementation introduces a result
variable, wraps core semaphore operations in an error-check condition, and
reorganizes code logic for improved maintainability and MISRA HIS standards
compliance.
## Motivation and Problem
The original nxsem_post_slow() function had multiple return statements
scattered throughout the code, including an early return for overflow
conditions. This violates MISRA HIS coding standards which require single exit
point patterns for improved code predictability, verifiability, and
maintainability in safety-critical contexts.
### Safety Standard Compliance
- **MISRA HIS Standard**: Enforces single-exit-point pattern for functions
- **Coverity Defect**: HIS_metric_violation (RETURN) - Multiple return
points detected
- **Pattern**: Introduce result variable with early error detection via flag
- **Benefit**: Enhanced code verifiability, improved static analysis
compatibility
## Changes Made
1. **Result Variable**: Added `int ret = OK;` initialization for unified
return value management
- Provides consistent return value across all code paths
- Replaces scattered return statements throughout function
2. **Error Path Restructuring**: Replaced early return for overflow with
break statement
- Changed `return -EOVERFLOW;` to `ret = -EOVERFLOW; break;`
- Error flag breaks from loop without immediate return
3. **Conditional Wrapping**: Wrapped all semaphore operations in `if (ret ==
OK)` block
- Consolidates all success-path operations
- Preserves early return semantics within condition
- Improves code structure and readability
4. **Comment Reorganization**: Moved detailed comments inside condition block
- Maintains documentation proximity to affected code
- Improves code clarity and structure
5. **Single Exit Point**: All code paths converge to single return statement
- `return ret;` at function end
- Uniform cleanup and resource release
### File Statistics
- **File Modified**: `sched/semaphore/sem_post.c`
- **Lines Changed**: 184 (94 insertions, 90 deletions)
- **Type**: Major code restructuring for compliance improvement
## Impact Analysis
✅ **Backward Compatibility**: MAINTAINED - Function behavior unchanged
✅ **Code Quality**: SIGNIFICANTLY IMPROVED - Single exit point, better
structure
✅ **Error Handling**: IMPROVED - Consistent error value management
✅ **Performance**: NO IMPACT - Same logic flow, improved organization
✅ **Semaphore Operations**: PRESERVED - All post semantics unchanged
✅ **Priority Handling**: MAINTAINED - Priority inheritance/protection logic
intact
## Verification Checklist
- [x] Compilation successful with all warning flags enabled
- [x] Semaphore post operation behavior unchanged for normal cases
- [x] Overflow condition properly detected and returns -EOVERFLOW
- [x] Task blocking and unblocking logic preserved
- [x] Priority inheritance semantics maintained
- [x] Critical section protection unchanged
- [x] Mutex-specific handling preserved
- [x] Wait list management unchanged
- [x] Context switching logic intact
- [x] Coverity HIS_metric_violation (RETURN) defect resolved
- [x] Code review completed - all logic paths tested
## Testing Scenarios
1. **Normal Post**: Semaphore count incremented correctly
2. **Overflow Condition**: Verify -EOVERFLOW returned and sem count unchanged
3. **Task Wakeup**: Blocked tasks correctly woken on semaphore post
4. **Mutex Semantics**: Mutex holder correctly transferred
5. **Priority Inheritance**: Priority restoration works with new structure
6. **Critical Section**: Proper interrupt protection maintained
7. **Concurrent Posts**: Multiple concurrent posts handled correctly
8. **Edge Cases**: Boundary conditions with maximum semaphore values
## Technical Notes
- Result variable initialized to OK at function start
- Overflow condition sets ret value and breaks from atomic operation loop
- All semaphore operations (holder release, task wakeup, priority
management) within ret==OK block
- Critical section protection timing unchanged
- Comment preservation improves code documentation
- Indentation adjusted to reflect new conditional structure
- All priority inheritance and protection protocol handling preserved
## Related Issues
- **Category**: Code Quality & Safety Standard Compliance
## Diff Summary
- Initialize return variable with OK at function start
- Replace early overflow return with conditional error flag and break
- Wrap all semaphore post operations in success-path condition block
- Move detailed comments inside conditional block
- Maintain all semaphore semantics and priority handling
- Single return statement at end of function
- Improved code structure and MISRA HIS compliance achieved
- **Standard**: MISRA HIS - Single Exit Point Pattern
- **Defect**: Coverity HIS_metric_violation (RETURN)
- **Subsystem**: Kernel semaphore management - post operation
(sched/semaphore/)
## Build Information
- **Compiler**: ARM GCC 10.x (primary test environment)
- **Architectures**: ARMv7-A, ARMv7-R, x86_64
- **Target**: NuttX kernel - semaphore subsystem
- **Build Flags**: `-Wall -Wextra -Werror`
- **Features**: CONFIG_PRIORITY_INHERITANCE, CONFIG_PRIORITY_PROTECT
configurable
## Files Changed
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