SpinLock.cs System::Threading::TicketType System::Threading::SpinLock System System::Threading System::Runtime::ConstrainedExecution //SpinLock.cs // //Copyright(c)2008Jérémie"Garuma"Laval //Copyright2011XamarinInc(http://www.xamarin.com). // //Permissionisherebygranted,freeofcharge,toanypersonobtainingacopy //ofthissoftwareandassociateddocumentationfiles(the"Software"),todeal //intheSoftwarewithoutrestriction,includingwithoutlimitationtherights //touse,copy,modify,merge,publish,distribute,sublicense,and/orsell //copiesoftheSoftware,andtopermitpersonstowhomtheSoftwareis //furnishedtodoso,subjecttothefollowingconditions: // //Theabovecopyrightnoticeandthispermissionnoticeshallbeincludedin //allcopiesorsubstantialportionsoftheSoftware. // //THESOFTWAREISPROVIDED"ASIS",WITHOUTWARRANTYOFANYKIND,EXPRESSOR //IMPLIED,INCLUDINGBUTNOTLIMITEDTOTHEWARRANTIESOFMERCHANTABILITY, //FITNESSFORAPARTICULARPURPOSEANDNONINFRINGEMENT.INNOEVENTSHALLTHE //AUTHORSORCOPYRIGHTHOLDERSBELIABLEFORANYCLAIM,DAMAGESOROTHER //LIABILITY,WHETHERINANACTIONOFCONTRACT,TORTOROTHERWISE,ARISINGFROM, //OUTOFORINCONNECTIONWITHTHESOFTWAREORTHEUSEOROTHERDEALINGSIN //THESOFTWARE. // // #ifNET_4_0||UNITY_5_3_OR_NEWER usingSystem; usingSystem.Collections.Concurrent; usingSystem.Runtime.ConstrainedExecution; usingSystem.Runtime.InteropServices; usingSystem.Runtime.CompilerServices; namespaceSystem.Threading { [StructLayout(LayoutKind.Explicit)] internalstructTicketType{ [FieldOffset(0)] publiclongTotalValue; [FieldOffset(0)] publicintValue; [FieldOffset(4)] publicintUsers; } /*ImplementtheticketSpinLockalgorithmdescribedonhttp://locklessinc.com/articles/locks/ *Thislockisusableonbothendianness. *Allthetry/finallypatternsinthisclassandvariousextragimmickscomparedtotheoriginal *algorithmareheretoavoidproblemscausedbyasynchronousexceptions. */ [System.Diagnostics.DebuggerDisplay("IsHeld={IsHeld}")] [System.Diagnostics.DebuggerTypeProxy("System.Threading.SpinLock+SystemThreading_SpinLockDebugView")] publicstructSpinLock { TicketTypeticket; intthreadWhoTookLock; readonlyboolisThreadOwnerTrackingEnabled; staticreadonlyWatchsw=Watch.StartNew(); ConcurrentOrderedList<int>stallTickets; publicboolIsThreadOwnerTrackingEnabled{ get{ returnisThreadOwnerTrackingEnabled; } } publicboolIsHeld{ get{ //Noneedforbarrierhere longtotalValue=ticket.TotalValue; return(totalValue>>32)!=(totalValue&0xFFFFFFFF); } } publicboolIsHeldByCurrentThread{ get{ if(isThreadOwnerTrackingEnabled) returnIsHeld&&Thread.CurrentThread.ManagedThreadId==threadWhoTookLock; else returnIsHeld; } } publicSpinLock(boolenableThreadOwnerTracking) { this.isThreadOwnerTrackingEnabled=enableThreadOwnerTracking; this.threadWhoTookLock=0; this.ticket=newTicketType(); //this.stallTickets=null; //SpicyPixel:Interlocked.CompareExchangewithreferencetypes //triestoJITonoldMonoAOT.Theonlysafeplacethento //initializestallTicketsisintheconstructor.Itdoesn't //makesensetousealockbecausethelockobjectwouldhave //tobeinitializedanyway(andthat'sthepointofthisclass). // //ThesolutionchosenistoalwaysinitializestallTicketshere. //Thismeans: //1.Slightperformancehitbecausenowwedoaheapallocwhen //itisnotalwaysnecessary. //2.AOThastousethisconstructor.Thedefaultone(whichwe //can'tdefineonastruct)doesnotinitializethecollection //andwecan'tdoitinEnterwithoutaworkingCompareExchange. this.stallTickets=newConcurrentOrderedList<int>(); } [MonoTODO("Notsafeagainstasyncexceptions")] publicvoidEnter(refboollockTaken) { if(lockTaken) thrownewArgumentException("lockTaken","lockTakenmustbeinitializedtofalse"); if(isThreadOwnerTrackingEnabled&&IsHeldByCurrentThread) thrownewLockRecursionException(); intslot=-1; RuntimeHelpers.PrepareConstrainedRegions(); try{ slot=Interlocked.Increment(refticket.Users)-1; SpinWaitwait=newSpinWait(); while(slot!=ticket.Value){ wait.SpinOnce(); while(stallTickets!=null&&stallTickets.TryRemove(ticket.Value)) ++ticket.Value; } }finally{ if(slot==ticket.Value){ lockTaken=true; threadWhoTookLock=Thread.CurrentThread.ManagedThreadId; }elseif(slot!=-1){ //Wehavebeeninterrupted,initializestallTickets if(stallTickets==null) Interlocked.CompareExchange(refstallTickets,newConcurrentOrderedList<int>(),null); stallTickets.TryAdd(slot); } } } publicvoidTryEnter(refboollockTaken) { TryEnter(0,reflockTaken); } publicvoidTryEnter(TimeSpantimeout,refboollockTaken) { TryEnter((int)timeout.TotalMilliseconds,reflockTaken); } publicvoidTryEnter(intmillisecondsTimeout,refboollockTaken) { if(millisecondsTimeout<-1) thrownewArgumentOutOfRangeException("milliSeconds","millisecondsTimeoutisanegativenumberotherthan-1"); if(lockTaken) thrownewArgumentException("lockTaken","lockTakenmustbeinitializedtofalse"); if(isThreadOwnerTrackingEnabled&&IsHeldByCurrentThread) thrownewLockRecursionException(); longstart=millisecondsTimeout==-1?0:sw.ElapsedMilliseconds; boolstop=false; do{ while(stallTickets!=null&&stallTickets.TryRemove(ticket.Value)) ++ticket.Value; longu=ticket.Users; longtotalValue=(u<<32)|u; longnewTotalValue =BitConverter.IsLittleEndian?(u<<32)|(u+1):((u+1)<<32)|u; RuntimeHelpers.PrepareConstrainedRegions(); try{} finally{ lockTaken=Interlocked.CompareExchange(refticket.TotalValue,newTotalValue,totalValue)==totalValue; if(lockTaken){ threadWhoTookLock=Thread.CurrentThread.ManagedThreadId; stop=true; } } }while(!stop&&(millisecondsTimeout==-1||(sw.ElapsedMilliseconds-start)<millisecondsTimeout)); } [ReliabilityContract(Consistency.WillNotCorruptState,Cer.Success)] publicvoidExit() { Exit(false); } [ReliabilityContract(Consistency.WillNotCorruptState,Cer.Success)] publicvoidExit(booluseMemoryBarrier) { RuntimeHelpers.PrepareConstrainedRegions(); try{} finally{ if(isThreadOwnerTrackingEnabled&&!IsHeldByCurrentThread) thrownewSynchronizationLockException("Currentthreadisnottheownerofthislock"); threadWhoTookLock=int.MinValue; do{ if(useMemoryBarrier) Interlocked.Increment(refticket.Value); else ticket.Value++; }while(stallTickets!=null&&stallTickets.TryRemove(ticket.Value)); } } } } #endif