InitializeCriticalSectionAndSpinCount

The InitializeCriticalSectionAndSpinCount function initializes a critical section object and sets the spin count for the critical section.

BOOL InitializeCriticalSectionAndSpinCount(
LPCRITICAL_SECTION lpCriticalSection,
// pointer to critical section
  DWORD dwSpinCount   // spin count for critical section
);

SetCriticalSectionSpinCount

The SetCriticalSectionSpinCount function sets the spin count for the specified critical section.

DWORD SetCriticalSectionSpinCount(
LPCRITICAL_SECTION lpCriticalSection,
// pointer to critical section
  DWORD dwSpinCount   // spin count for critical section
);

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当线程试图进入另一个线程拥有的关键代码段时，调用线程就立即被置于等待状态。这意
味着该线程必须从用户方式转入内核方式（大约1 0 0 0个C P U周期）。这种转换是要付出很大代价的。因此， InitializeCriticalSectionAndSpinCount 的作用不同于InitializeCriticalSection 之处就在于设置了一个循环锁，不至于使线程立刻被置于等待状态而耗费大量的CPU周期，而在dwSpinCount后才转为内核方式进入等待状态。通常dwSpinCount设为4000较为合适 。