From 50205bc4df3c272b88a5edd81a35ac0aca8213d5 Mon Sep 17 00:00:00 2001
From: madmaxoft <github@xoft.cz>
Date: Wed, 14 Aug 2013 22:39:12 +0200
Subject: Added simple deadlock detection code.

This will assert and then deliberately crash the server once a deadlock is detected. For detection, only the world tick threads are considered, cWorld's m_WorldAge is checked periodically and if it doesn't increment for several seconds, a deadlock is reported.
---
 source/DeadlockDetect.h | 70 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100644 source/DeadlockDetect.h

(limited to 'source/DeadlockDetect.h')

diff --git a/source/DeadlockDetect.h b/source/DeadlockDetect.h
new file mode 100644
index 000000000..bbd76826a
--- /dev/null
+++ b/source/DeadlockDetect.h
@@ -0,0 +1,70 @@
+
+// DeadlockDetect.h
+
+// Declares the cDeadlockDetect class that tries to detect deadlocks and aborts the server when it detects one
+
+/*
+This class simply monitors each world's m_WorldAge, which is expected to grow on each tick.
+If the world age doesn't grow for several seconds, it's either because the server is super-overloaded,
+or because the world tick thread hangs in a deadlock. We presume the latter and therefore kill the server.
+Once we learn to write crashdumps programmatically, we should do so just before killing, to enable debugging.
+*/
+
+
+
+#pragma once
+
+#include "OSSupport/IsThread.h"
+
+
+
+
+
+class cDeadlockDetect :
+	public cIsThread
+{
+	typedef cIsThread super;
+	
+public:
+	cDeadlockDetect(void);
+	
+	/// Starts the detection. Hides cIsThread's Start, because we need some initialization
+	bool Start(void);
+	
+	/// Stops the detection. Hides cIsThread's Stop, because we need to signal m_EvtTerminate
+	void Stop(void);
+	
+protected:
+	struct sWorldAge
+	{
+		/// Last m_WorldAge that has been detected in this world
+		Int64 m_Age;
+		
+		/// Number of cycles for which the age has been the same
+		int m_NumCyclesSame;
+	} ;
+	
+	/// Maps world name -> sWorldAge
+	typedef std::map<AString, sWorldAge> WorldAges;
+	
+	WorldAges m_WorldAges;
+	
+	cEvent m_EvtTerminate;
+	
+	
+	// cIsThread overrides:
+	virtual void Execute(void) override;
+	
+	/// Sets the initial world age
+	void SetWorldAge(const AString & a_WorldName, Int64 a_Age);
+	
+	/// Checks if the world's age has changed, updates the world's stats; calls DeadlockDetected() if deadlock detected
+	void CheckWorldAge(const AString & a_WorldName, Int64 a_Age);
+	
+	/// Called when a deadlock is detected. Aborts the server.
+	void DeadlockDetected(void);
+} ;
+
+
+
+
-- 
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