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// 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
{
using Super = cIsThread;
public:
cDeadlockDetect();
virtual ~cDeadlockDetect() override;
/** Starts the detection. Hides cIsThread's Start, because we need some initialization */
void Start(int a_IntervalSec);
/** Adds the critical section for tracking.
Tracked CSs are listed, together with ownership details, when a deadlock is detected.
A tracked CS must be untracked before it is destroyed.
a_Name is an arbitrary name that is listed along with the CS in the output. */
void TrackCriticalSection(cCriticalSection & a_CS, const AString & a_Name);
/** Removes the CS from the tracking. */
void UntrackCriticalSection(cCriticalSection & a_CS);
protected:
struct sWorldAge
{
/** Last m_WorldAge that has been detected in this world */
cTickTimeLong 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;
/** Protects m_TrackedCriticalSections from multithreaded access. */
cCriticalSection m_CS;
/** CriticalSections that are tracked (their status output on deadlock).
Protected against multithreaded access by m_CS. */
std::vector<std::pair<cCriticalSection *, AString>> m_TrackedCriticalSections;
WorldAges m_WorldAges;
/** Number of secods for which the ages must be the same for the detection to trigger */
int m_IntervalSec;
// cIsThread overrides:
virtual void Execute(void) override;
/** Sets the initial world age. */
void SetWorldAge(const AString & a_WorldName, cTickTimeLong 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, cTickTimeLong a_Age);
/** Called when a deadlock is detected in a world. Aborts the server.
a_WorldName is the name of the world whose age has triggered the detection.
a_WorldAge is the age (in ticks) in which the world is stuck. */
[[noreturn]] void DeadlockDetected(const AString & a_WorldName, cTickTimeLong a_WorldAge);
/** Outputs a listing of the tracked CSs, together with their name and state. */
void ListTrackedCSs();
};
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