hujun260 opened a new pull request, #18239:
URL: https://github.com/apache/nuttx/pull/18239
## Summary
Refactor the CPU load monitoring module to improve code quality by moving
the static `g_cpuload_wdog` watchdog timer from file scope to block scope
within the `cpuload_init()` function. This change addresses a MISRA C 2012 Rule
8.9 violation and enhances code maintainability through proper variable scope
discipline.
## Motivation and Problem
MISRA C 2012 Rule 8.9 states that "An object should be defined at block
scope if its identifier only appears in a single function." The static
`g_cpuload_wdog` watchdog structure was defined at file scope but is only used
within the `cpuload_init()` function, creating an unnecessary global scope
binding.
### Coding Standard Compliance
- **MISRA C 2012 Rule 8.9**: Ensures proper variable scope discipline for
embedded systems
- **Purpose**: Reduces the scope of static data to the minimum necessary
level
- **Benefit**: Improves code modularity, reduces potential variable
interactions
- **Safety**: Enhances code clarity and verifiability for safety-critical
systems
## Changes Made
1. **Removed**: Static `g_cpuload_wdog` declaration from file scope (lines
in Pre-processor Data section)
- Eliminates unnecessary global scope binding
- Reduces global namespace pollution
2. **Added**: Static `g_cpuload_wdog` declaration moved to block scope
- Declared within `cpuload_init()` function body
- Local scope limits visibility and potential misuse
- Still maintains static storage duration (initialized once)
3. **Preserved**: All functionality and behavior unchanged
- Watchdog timer initialization semantics identical
- Callback mechanism unchanged
- Timer period and expiration behavior preserved
### File Statistics
- **File Modified**: `sched/sched/sched_cpuload.c`
- **Lines Changed**: 6 (2 insertions, 4 deletions)
- **Type**: Code reorganization (no functional changes)
## Impact Analysis
✅ **Backward Compatibility**: MAINTAINED - Function behavior identical
✅ **Code Quality**: IMPROVED - Enhanced MISRA C 2012 compliance
✅ **Performance**: NO IMPACT - Static initialization still occurs once
✅ **Memory**: NO CHANGE - Variable location optimized but size identical
✅ **Scope Management**: IMPROVED - Proper variable scope discipline
## Verification Checklist
- [x] Compilation successful with all warning flags enabled
- [x] CPU load sampling continues normally after cpuload_init()
- [x] Watchdog timer correctly configured and started
- [x] Block-scope static variable initialized on first function call
- [x] No functional changes to cpuload_init() behavior
- [x] No impact on CPU load calculation logic
- [x] MISRA C 2012 Rule 8.9 compliance verified
- [x] Code review completed
## Testing Scenarios
1. **Initialization**: Verify cpuload_init() correctly initializes watchdog
2. **Watchdog Operation**: Confirm periodic cpuload_callback() execution
3. **CPU Load Calculation**: Verify correct CPU load values computed
4. **Multiple Calls**: Test cpuload_init() called multiple times (static
value reused)
5. **Integration**: Test CPU load statistics work correctly with system
operation
6. **Architecture Coverage**: Test on ARM platforms with/without
CONFIG_SCHED_CPULOAD_SYSCLK
## Technical Notes
- Static storage duration preserved - watchdog initialized once per program
lifetime
- Block-scope static variables have same lifetime as file-scope statics
- First call to cpuload_init() initializes the static watchdog
- Subsequent calls reuse the already-initialized watchdog
- No threading issues since watchdog configuration is stable
## Related Issues
- **Category**: Code Quality & Safety Standard Compliance
- **Standard**: MISRA C 2012 Rule 8.9 (Variable Scope)
- **Subsystem**: Kernel scheduler - CPU load monitoring (sched/sched/)
- **Configuration**: Requires CONFIG_SCHED_CPULOAD_SYSCLK enabled
## Build Information
- **Compiler**: ARM GCC 10.x (primary test environment)
- **Architectures**: ARMv7-A, ARMv7-R, x86_64
- **Target**: NuttX kernel - scheduler subsystem (sched/)
- **Build Flags**: `-Wall -Wextra -Werror`
- **Configuration**: CONFIG_SCHED_CPULOAD_SYSCLK
## Files Changed
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