| 摘要 |
Locks are used to protect variables. All variables protected by a lock are allocated on a page associated with a lock. When a thread (called the owner) acquires the lock, a local copy of the memory page containing the variable is created, the original memory page is protected, and all access of the variable in the owner thread is directed to the local copy. Upon releasing the lock, the changes from the local copy are carried over to the memory page and the memory page is unprotected. Any concurrent access of the variable by non-owner threads triggers an exception handler (due to the protection mechanism) and delays such an access until after the owner thread has finished accessing the variable.
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