From 7cc3fb098df221f083da1d81d2327a0a5f22edf5 Mon Sep 17 00:00:00 2001
From: Mattes D <github@xoft.cz>
Date: Tue, 17 Jan 2017 22:38:04 +0100
Subject: DeadlockDetect now lists some tracked CS's stats.

---
 src/OSSupport/CriticalSection.cpp | 24 ++++++++----------------
 src/OSSupport/CriticalSection.h   | 39 ++++++++++++++++++++++++++-------------
 2 files changed, 34 insertions(+), 29 deletions(-)

(limited to 'src/OSSupport')

diff --git a/src/OSSupport/CriticalSection.cpp b/src/OSSupport/CriticalSection.cpp
index 2e533676d..27284acb0 100644
--- a/src/OSSupport/CriticalSection.cpp
+++ b/src/OSSupport/CriticalSection.cpp
@@ -9,12 +9,10 @@
 ////////////////////////////////////////////////////////////////////////////////
 // cCriticalSection:
 
-#ifdef _DEBUG
-cCriticalSection::cCriticalSection()
+cCriticalSection::cCriticalSection():
+	m_RecursionCount(0)
 {
-	m_IsLocked = 0;
 }
-#endif  // _DEBUG
 
 
 
@@ -24,10 +22,8 @@ void cCriticalSection::Lock()
 {
 	m_Mutex.lock();
 
-	#ifdef _DEBUG
-		m_IsLocked += 1;
-		m_OwningThreadID = std::this_thread::get_id();
-	#endif  // _DEBUG
+	m_RecursionCount += 1;
+	m_OwningThreadID = std::this_thread::get_id();
 }
 
 
@@ -36,10 +32,8 @@ void cCriticalSection::Lock()
 
 void cCriticalSection::Unlock()
 {
-	#ifdef _DEBUG
-		ASSERT(m_IsLocked > 0);
-		m_IsLocked -= 1;
-	#endif  // _DEBUG
+	ASSERT(IsLockedByCurrentThread());
+	m_RecursionCount -= 1;
 
 	m_Mutex.unlock();
 }
@@ -48,10 +42,9 @@ void cCriticalSection::Unlock()
 
 
 
-#ifdef _DEBUG
 bool cCriticalSection::IsLocked(void)
 {
-	return (m_IsLocked > 0);
+	return (m_RecursionCount > 0);
 }
 
 
@@ -60,9 +53,8 @@ bool cCriticalSection::IsLocked(void)
 
 bool cCriticalSection::IsLockedByCurrentThread(void)
 {
-	return ((m_IsLocked > 0) && (m_OwningThreadID == std::this_thread::get_id()));
+	return ((m_RecursionCount > 0) && (m_OwningThreadID == std::this_thread::get_id()));
 }
-#endif  // _DEBUG
 
 
 
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;
-- 
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