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            http://www.boost.org/doc/libs/1_35_0/doc/html/thread/synchronization.html

            Mutex概念
            線程同步最基本的是mutex(mutual exclusion的縮寫)。一個互斥體一次只允許一個線程訪問共享區。當一個線程想要訪問共享區時,首先要做的就是鎖住(lock)互斥體。如果其他的 線程已經鎖住了互斥體,那么就必須先等那個線程將互斥體解鎖,這樣就保證了同一時刻只有一個線程能訪問共享區域。

            Boost.Thread supplies recursive and non-recursive mutexes with exclusive ownership(獨占) semantics, along with a shared ownership (共享) (multiple-reader / single-writer) mutex.
            Boost.Thread supports four basic concepts for lockable objects:

            Lockable,
            exclusive ownership
            TimedLockable,
            Lockable的基礎上加上了timeout
            SharedLockable,
            TimedLockable基礎上,允許shared ownership(同時也支持exclusive)
            This is the standard multiple-reader / single-write model:
            at most one thread can have exclusive ownership, and if any thread does have exclusive ownership, no other threads can have shared or exclusive ownership. Alternatively, many threads may have shared ownership.
            UpgradeLockable,
            SharedLockable基礎上,允許upgradable ownership(同時也支持shared、exclusive)
            This is an extension to the multiple-reader / single-write model provided by the SharedLockable concept:
            a single thread may have upgradable ownership at the same time as others have shared ownership. The thread with upgradable ownership may at any time attempt to upgrade that ownership to exclusive ownership. If no other threads have shared ownership, the upgrade is completed immediately, and the thread now has exclusive ownership, which must be relinquished by a call to unlock(), just as if it had been acquired by a call to lock().

            [注:除Lockable的mutex外,其余的各種復雜mutex還需要更多代碼實踐]

            Each mutex type implements one or more of these concepts, as do the various lock types.

            Lock Types
            boost定義的Lock types為class template,以合適的Lockable object作為模板參數
            lock_guard
            RAII-style的簡單lock,在ctor中lock,在dtor中unlock
            只支持簡單的Lockable object
            unique_lock
            lock_guard復雜在:不僅提供RAII-style的lock,還允許用戶指定是否在ctor中立即lock,意味著可以指定推遲lock(defer acquiring the lock,通過指定defer_lock_t參數),直到顯式調用其lock()方法
            還支持TimedLockable concept,前提是需要lock的Lockable object本身支持
            The member functions of boost::unique_lock are not thread-safe...[注:這句沒看懂。。。]

            shared_lock
            upgrade_lock
            upgrade_to_unique_lock

            [注:目前只用過unique_lock。后面幾種對應于不同需求的lock,從名字就可以直觀看出功能,還未試驗,直接參考api]
            Mutex Types
            Mutex types對應于之前的mutex concepts,目前有:
            Class mutex
            boost::mutex實現了Lockable concept,提供exclusive-ownership mutex.
            At most one thread can own the lock on a given instance of boost::mutex at any time.
            Multiple concurrent calls to lock(), try_lock() and unlock() shall be permitted.

            typedef unique_lock mutex::scoped_lock;

            Typedef try_mutex
            Class timed_mutex
            Class recursive_mutex
            Typedef recursive_try_mutex
            Class recursive_timed_mutex
            Class shared_mutex
            適用于不同需求


            Condition Variables
            The general usage pattern is that one thread locks a mutex and then calls wait on an instance of condition_variable or condition_variable_any. When the thread is woken from the wait, then it checks to see if the appropriate condition is now true, and continues if so. If the condition is not true, then the thread then calls wait again to resume waiting.(中文參考)

            lock is passed to wait()wait() will atomically add the thread to the set of threads waiting on the condition variable, and unlock the mutex. When the thread is woken, the mutex will be locked again before the call to wait returns. This allows other threads to acquire the mutex in order to update the shared data, and ensures that the data associated with the condition is correctly synchronized.

            In the mean time, another thread sets the condition to true, and then calls either notify_one() or notify_all() on the condition variable to wake one waiting thread or all the waiting threads respectively.


            condition_variable_any比condition_variable更通用;condition_variable要求傳給wait()的必須是boost::unique_lock<boost::mutex>類型;condition_variable一般更優化

            One-time Initialization
            僅運行一次的例程
            http://www.stlchina.org/twiki/bin/view.pl/Main/BoostThread#5%20%BD%F6%D4%CB%D0%D0%D2%BB%B4%CE%B5%C4%C0%FD%B3%CC
            [注:還未使用過]

            Barriers
            [注:還未使用過]



            posted on 2008-04-29 14:28 frank28_nfls 閱讀(655) 評論(0)  編輯 收藏 引用
             
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