hujun260 opened a new pull request, #17956:
URL: https://github.com/apache/nuttx/pull/17956
## Summary
This PR optimizes the hostname operations by replacing global critical
section
locks with a lightweight spinlock. The hostname is a shared system property
that
needs synchronization, but using global critical sections causes unnecessary
interrupt latency throughout the system. A dedicated spinlock provides
better
performance and scalability.
## Changes
The optimization involves synchronization changes in two files:
1. **libs/libc/unistd/lib_gethostname.c** - Add spinlock for hostname
reading:
- Add `#include <nuttx/spinlock.h>` header
- Define static spinlock: `spinlock_t g_hostname_lock = SP_UNLOCKED`
- Replace `enter_critical_section()` with
`spin_lock_irqsave(&g_hostname_lock)`
- Replace `leave_critical_section()` with
`spin_unlock_irqrestore(&g_hostname_lock, flags)`
- Protects hostname reading during string copy
2. **libs/libc/unistd/lib_sethostname.c** - Add spinlock for hostname
writing:
- Add `#include <nuttx/spinlock.h>` header
- Declare external spinlock: `extern spinlock_t g_hostname_lock`
- Replace `enter_critical_section()` with
`spin_lock_irqsave(&g_hostname_lock)`
- Replace `leave_critical_section()` with
`spin_unlock_irqrestore(&g_hostname_lock, flags)`
- Protects hostname writing during string copy
## Benefits
- **Performance**: Reduces interrupt latency by using spinlock instead of
global critical section
- **Scalability**: Per-subsystem spinlock allows other code to proceed
without delay
- **Correctness**: Maintains proper synchronization for the shared hostname
resource
- **Efficiency**: Lightweight spinlock is appropriate for short critical
sections
## Technical Details
**Why spinlock instead of critical section?**
- Critical sections disable interrupts globally, blocking all interrupt
handlers
- Spinlock only protects access to the specific shared resource
- Reduces latency for unrelated operations
**Synchronization scope:**
- `gethostname()`: Protects reading g_hostname during copy to user buffer
- `sethostname()`: Protects writing g_hostname from user-provided buffer
## Testing
Tested on:
- **Platform**: NuttX with multi-core support
- **Configuration**: User-mode and kernel-mode builds
- **Test scenarios**:
- Concurrent reads from multiple tasks
- Concurrent writes with various hostname lengths
- Signal handling during hostname operations
- Network stack hostname access patterns
- Interrupt latency measurements
- **Result**:
- Hostname operations work correctly with spinlock
- Reduced interrupt latency vs. critical sections
- No data corruption or race conditions
- Improved system responsiveness
## Impact
- **Performance**: Improved system-wide interrupt latency
- **Stability**: Maintains correct hostname synchronization
- **Compatibility**: No API changes; internal optimization only
- **Code Quality**: Cleaner synchronization model
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