Function spinlock_smp_string_test

tests/system_test/spinlock_test.cpp:204–346

std::atomic<int> str_test_start_barrier = 0;

auto spinlock_smp_string_test() -> bool {
  size_t core_id = cpu_io::GetCurrentCoreId();
  size_t core_count = BasicInfoSingleton::instance().core_count;

  if (core_count < 2) {
    if (core_id == 0) {
      klog::Info("Skipping SMP string test: need more than 1 core.");
    }
    return true;
  }

  int arrived = str_test_start_barrier.fetch_add(1) + 1;

  constexpr int kBarrierSpinLimit = 100000000;
  int spins = 0;
  while (str_test_start_barrier.load(std::memory_order_acquire) <
         (int)core_count) {
    cpu_io::Pause();
    if (++spins > kBarrierSpinLimit) {
      if (core_id == 0) {
        klog::Err(
            "SMP string test barrier timeout: {}/{} cores arrived, skipping",
            str_test_start_barrier.load(), (int)core_count);
      }
      return false;
    }
  }

  int writes_per_core = 500;
  char local_buf[128];

  for (int i = 0; i < writes_per_core; ++i) {
    // 2. 先写入可区分的字符串到本地缓冲区
    // 增加数据长度以增加临界区持续时间
    auto* end = etl::format_to_n(local_buf, sizeof(local_buf) - 1,
                                 "[C:{}-{}|LongStringPaddingForContention]",
                                 (int)core_id, i);
    *end = '\0';
    int len = static_cast<int>(end - local_buf);

    (void)str_lock.Lock();
    if (str_buffer_offset + len < STR_BUFFER_SIZE - 1) {
      for (int k = 0; k < len; ++k) {
        shared_str_buffer[str_buffer_offset + k] = local_buf[k];
      }
      str_buffer_offset += len;
      shared_str_buffer[str_buffer_offset] = '\0';
    }
    (void)str_lock.UnLock();
  }

  int finished = str_test_finished_cores.fetch_add(1) + 1;
  if (finished == (int)core_count) {
    // 3. 验证
    klog::Info(
        "All cores finished string writes. Verifying string integrity...");
    bool failed = false;
    int current_idx = 0;