标签：style color io os ar sp on c ad
A semaphore initialized to one, and which is used such that it only has at most one permit available, can serve as a mutual exclusion
lock. This is more commonly known as a binary semaphore, because it only has two states: one permit available, or zero permits
available. When used in this way, the binary semaphore has the property (unlike many Lock implementations), that the "lock" can be
released by a thread other than the owner (as semaphores have no notion of ownership). This can be useful in some specialized
contexts, such as deadlock recovery.
标签：style color io os ar sp on c ad
原文地址：http://www.cnblogs.com/yuyutianxia/p/3983507.html
