The Barrier class is used to create synchronization points for multi-phase operations.

Barrier类的作用是在多个阶段的操作之间创建同步点。

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LOCK-Based Critical Sections: Although a LOCK-UNLOCK pair does not act as a full memory barrier, these operations do affect memory ordering. Consider the following code.

锁保护的临界区：经lock - UNLOCK对不能实现完全的内存屏障的功能，但是，它们也的确会影响内存访问顺序，参考下面的示例代码。

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Many of the injuries were sustained when fans jumped onto the field from a barrier as high as 15 feet in places, said Michael Authement, director of operations for emergency medical provider LifeNet EMS. Others were stomped on in the push to get to the field, he said.

WSJ: Oklahoma State Football Melee Puts Security Under Scrutiny