93 lines
2.9 KiB
C++
93 lines
2.9 KiB
C++
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#pragma once
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class cCriticalSection
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{
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friend class cDeadlockDetect; // Allow the DeadlockDetect to read the internals, so that it may output some statistics
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public:
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void Lock(void);
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void Unlock(void);
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cCriticalSection(void);
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/** Returns true if the CS is currently locked.
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Note that since it relies on the m_RecursionCount value, it is inherently thread-unsafe, prone to false positives.
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Also, due to multithreading, the state can change between this when function is evaluated and the returned value is used.
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To be used in ASSERT(IsLocked()) only. */
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bool IsLocked(void);
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/** Returns true if the CS is currently locked by the thread calling this function.
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Note that since it relies on the m_RecursionCount value, it is inherently thread-unsafe, prone to false positives.
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Also, due to multithreading, the state can change between this when function is evaluated and the returned value is used.
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To be used in ASSERT(IsLockedByCurrentThread()) only. */
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bool IsLockedByCurrentThread(void);
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private:
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/** Number of times that this CS is currently locked (levels of recursion). Zero if not locked.
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Note that this value should be considered true only when the CS is locked; without the lock, it is UndefinedBehavior to even read it,
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but making it std::atomic would impose too much of a runtime penalty.
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It is only ever read without the lock in the DeadlockDetect, where the server is terminating anyway. */
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int m_RecursionCount;
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/** ID of the thread that is currently holding the CS.
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Note that this value should be considered true only when the CS is locked; without the lock, it is UndefinedBehavior to even read it,
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but making it std::atomic would impose too much of a runtime penalty.
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When unlocked, the value stored here has no meaning, it may be an ID of a previous holder, or it could be any garbage.
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It is only ever read without the lock in the DeadlockDetect, where the server is terminating anyway. */
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std::thread::id m_OwningThreadID;
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std::recursive_mutex m_Mutex;
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};
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/** RAII for cCriticalSection - locks the CS on creation, unlocks on destruction */
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class cCSLock
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{
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cCriticalSection * m_CS;
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// Unlike a cCriticalSection, this object should be used from a single thread, therefore access to m_IsLocked is not threadsafe
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// In Windows, it is an error to call cCriticalSection::Unlock() multiple times if the lock is not held,
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// therefore we need to check this value whether we are locked or not.
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bool m_IsLocked;
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public:
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cCSLock(cCriticalSection * a_CS);
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cCSLock(cCriticalSection & a_CS);
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~cCSLock();
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// Temporarily unlock or re-lock:
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void Lock(void);
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void Unlock(void);
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private:
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DISALLOW_COPY_AND_ASSIGN(cCSLock);
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} ;
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/** Temporary RAII unlock for a cCSLock. Useful for unlock-wait-relock scenarios */
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class cCSUnlock
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{
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cCSLock & m_Lock;
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public:
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cCSUnlock(cCSLock & a_Lock);
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~cCSUnlock();
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private:
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DISALLOW_COPY_AND_ASSIGN(cCSUnlock);
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} ;
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