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authorMattes D <github@xoft.cz>2017-01-17 22:38:04 +0100
committerMattes D <github@xoft.cz>2017-01-18 09:03:05 +0100
commit7cc3fb098df221f083da1d81d2327a0a5f22edf5 (patch)
treede9232cbf239800ea1e7a71cf52086509a9472ea /src/OSSupport/CriticalSection.h
parentDebuggers: Added a deadlock simulation command. (diff)
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Diffstat (limited to 'src/OSSupport/CriticalSection.h')
-rw-r--r--src/OSSupport/CriticalSection.h39
1 files changed, 26 insertions, 13 deletions
diff --git a/src/OSSupport/CriticalSection.h b/src/OSSupport/CriticalSection.h
index 6ea18051a..917957aeb 100644
--- a/src/OSSupport/CriticalSection.h
+++ b/src/OSSupport/CriticalSection.h
@@ -9,27 +9,40 @@
class cCriticalSection
{
+ friend class cDeadlockDetect; // Allow the DeadlockDetect to read the internals, so that it may output some statistics
+
public:
void Lock(void);
void Unlock(void);
- // IsLocked / IsLockedByCurrentThread are only used in ASSERT statements, but because of the changes with ASSERT they must always be defined
- // The fake versions (in Release) will not effect the program in any way
- #ifdef _DEBUG
- cCriticalSection(void);
- bool IsLocked(void);
- bool IsLockedByCurrentThread(void);
- #else
- bool IsLocked(void) { return false; }
- bool IsLockedByCurrentThread(void) { return false; }
- #endif // _DEBUG
+ cCriticalSection(void);
+
+ /** Returns true if the CS is currently locked.
+ Note that since it relies on the m_RecursionCount value, it is inherently thread-unsafe, prone to false positives.
+ Also, due to multithreading, the state can change between this when function is evaluated and the returned value is used.
+ To be used in ASSERT(IsLocked()) only. */
+ bool IsLocked(void);
+
+ /** Returns true if the CS is currently locked by the thread calling this function.
+ Note that since it relies on the m_RecursionCount value, it is inherently thread-unsafe, prone to false positives.
+ Also, due to multithreading, the state can change between this when function is evaluated and the returned value is used.
+ To be used in ASSERT(IsLockedByCurrentThread()) only. */
+ bool IsLockedByCurrentThread(void);
private:
- #ifdef _DEBUG
- int m_IsLocked; // Number of times this CS is locked
+ /** Number of times that this CS is currently locked (levels of recursion). Zero if not locked.
+ Note that this value should be considered true only when the CS is locked; without the lock, it is UndefinedBehavior to even read it,
+ but making it std::atomic would impose too much of a runtime penalty.
+ It is only ever read without the lock in the DeadlockDetect, where the server is terminating anyway. */
+ int m_RecursionCount;
+
+ /** ID of the thread that is currently holding the CS.
+ Note that this value should be considered true only when the CS is locked; without the lock, it is UndefinedBehavior to even read it,
+ but making it std::atomic would impose too much of a runtime penalty.
+ When unlocked, the value stored here has no meaning, it may be an ID of a previous holder, or it could be any garbage.
+ It is only ever read without the lock in the DeadlockDetect, where the server is terminating anyway. */
std::thread::id m_OwningThreadID;
- #endif // _DEBUG
std::recursive_mutex m_Mutex;
} ALIGN_8;