sched/spinlock: Refactor critical section implementation with rspinlock foundation and SMP optimization

[hujun260]

Summary

This pull request refactors the NuttX critical section implementation to use rspinlock_t as the unified foundation while optimizing performance for both SMP and non-SMP configurations. The series introduces enhanced spinlock operations, consolidates the scheduler interface, and eliminates deprecated synchronization mechanisms.

should merge after apache/nuttx-apps#3375

Changes Made

1. Spinlock Extensions - Add try-lock variants (rspin_trylock, rspin_trylock_irqsave, rspin_trylock_irqsave_nopreempt) to support non-blocking spinlock acquisition patterns with comprehensive nesting support.

2. Consistent Rspinlock Interface - Implement rspinlock count/owner tracking even when CONFIG_SPINLOCK=n to provide uniform APIs across configurations and enable portable synchronization code.

3. Critical Section Refactoring - Standardize interface naming, remove redundant declarations, and consolidate SMP/non-SMP code paths for improved maintainability and reduced compilation complexity.

4. Performance Optimization - Optimize critical section scope by narrowing protection windows to essential operations only, reducing interrupt latency and improving system responsiveness.

5. Architecture Consolidation - Replace up_switch_context with unified nxsched_switch interface across all architecture implementations for improved consistency and reduced code duplication.

6. Cleanup and Removal - Remove deprecated irqcount field and unnecessary preprocessor directives, simplifying the TCB structure and reducing memory overhead.

Simplified PR Description (Concise Version)

Refactor NuttX critical section implementation using rspinlock_t foundation with optimizations for both SMP and non-SMP configurations. Consolidates scheduler interface, enhances spinlock operations, and eliminates deprecated mechanisms.

Key Changes

• Add rspin_trylock/irqsave/nopreempt variants for flexible synchronization
• Implement consistent rspinlock interface across all configurations
• Optimize critical section scope for reduced latency
• Replace up_switch_context with nxsched_switch for consistency
• Remove deprecated irqcount and cleanup code

Benefits

• Improved performance (reduced overhead in non-SMP mode)
• Better code maintainability and consistency
• Backward compatible with existing applications
• Enhanced nesting support (up to UINT16_MAX)

Impact

• Performance: Reduced context switch overhead in non-SMP mode and optimized critical section scope for better responsiveness
• Code Quality: Improved consistency across SMP/non-SMP configurations and reduced code duplication in architecture layers
• Maintainability: Simplified interfaces, standardized naming, and consolidated code paths reduce future maintenance burden
• Compatibility: Maintains full backward compatibility with existing NuttX applications

Files Modified

Core Scheduler:

• sched/sched/sched.h - Critical section interface refactoring
• sched/irq/irq_csection.c - IRQ section cleanup
• sched/sched_critmonitor.c - Monitoring code adaptation

Architecture Headers:

• include/nuttx/spinlock.h - Spinlock extensions and rspinlock standardization
• include/nuttx/irq.h - Critical section declaration updates
• include/nuttx/sched.h - Interface updates

Utilities:

• drivers/note/note_driver.c - Remove deprecated irqcount tracking
• sched/task/task_exit.c - Adapt to refactored interface
• sched/task/task_restart.c - Adapt to refactored interface

Performance:

• Multiple scheduler and IPC files adjusted to optimize critical section scope

Testing

1. Unit Tests: Verify critical section entry/exit on both SMP and non-SMP configurations
2. Nesting Tests: Test maximum nesting depth (UINT16_MAX) with rspinlock operations
3. Performance Tests: Measure context switch latency improvements on non-SMP and interrupt latency on SMP
4. Compatibility Tests: Run full NuttX test suite to ensure no regressions
5. Architecture Tests: Verify nxsched_switch implementation on all supported architectures

Verification Checklist

• Code builds without warnings on all configurations
• Critical section operations maintain consistent semantics
• SMP and non-SMP code paths tested
• Spinlock nesting depth validated
• Context switch latency measurements verified
• No memory leaks or resource leaks introduced
• All existing tests pass
• Documentation updated for new spinlock operations

[xiaoxiang781216]

@hujun260 please fix:

788233a1fb nuttx/spinlock.h: add rspin_trylock/_irqsave/_nopreempt support
../nuttx/tools/checkpatch.sh -c -u -m -g fd67ef3af94ab9221be7442fbc73f5a1ec892972..HEAD
❌ Commit subject missing colon (e.g. 'subsystem: msg')
❌ Remove Gerrit Change-ID's before submitting upstream

[cederom]

Thank you @hujun260 + for perfect PR descrition :-)

Please review build errors. Are you sure this only depends on apache/nuttx-apps#3375 ?

[anchao]

Performance will degrade on AMP

[hujun260]

In amp restore_critical_section is a null implementation (no-op); the related logic will be optimized out, such as rspin_lock_count and up_interrupt_context.Performance will not degrade