问题
My multithreaded app in C# 2.0 using threadpool hangs every few weeks or so in prod.
I did a syncblk
!syncblk Index SyncBlock MonitorHeld Recursion Owning Thread Info SyncBlock Owner 201 05b9493c 979 1 05bc1040 bcc 45 022f3490 System.Collections.ArrayList 2875 05b4c914 1 1 17b99e10 1af8 290 024862d8 MyProg.MyChildClass 3045 05b4dbec 1 1 17ca7e98 1990 664 02392120 MyProg.MyChildClass 3046 05b4dc1c 1 1 17ca8668 1038 666 02394b00 MyProg.MyChildClass 3194 05b4f80c 3 1 05b5b638 1594 31 02537b88 MyProg.MyChildClass 3072 05b4e114 1 1 17d660f0 1120 848 023dd578 MyProg.MyChildClass 3073 05b4e144 1 1 17c45c30 1884 518 023dfc2c MyProg.MyChildClass 3390 05b51cfc 3 1 16cefcc0 1350 102 02768868 MyProg.MyChildClass 3072 05b4e114 1 1 17d660f0 1120 848 023dd578 MyProg.MyChildClass 3073 05b4e144 1 1 17c45c30 1884 518 023dfc2c MyProg.MyChildClass
I have deleted hundreds of lines that look like this:
3073 05b4e144 1 1 17c45c30 1884 518 023dfc2c MyProg.MyChildClass
The thread holding 979 monitors is locking an arraylist but all other threads who are waiting are trying to acquire a readerlock on a different object.
I do know which lock are all reader threads trying to acquire but I do not know who is holding that lock. How do I find that out??
All threads with MonitorHeld = 1 has the similar output of clrstack and dso. Here is the dso and clrstack output for the thread holding 979 locks (id = 45) and waiting reader threads (id = 290). Similarly, when I do ~* e !clrstack all threads with Monitor.Enter have the same stack as the clrstack on the following 2 threads
0:000> ~45e !clrstack OS Thread Id: 0xbcc (45) ESP EIP 17fbe590 77d2013d [GCFrame: 17fbe590] 17fbe6cc 77d2013d [HelperMethodFrame: 17fbe6cc] System.Threading.Monitor.Enter(System.Object) 17fbe720 00638427 MyProg.MyParentClass.ClockTimeElapsed(System.DateTime) 17fbe798 00637cf6 MyProg.MyEngine.ClockTimeElapsed(System.Object) 17fbe830 71df843f System.Threading._TimerCallback.TimerCallback_Context(System.Object) 17fbe838 71e302ff System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object) 17fbe850 71df83ab System.Threading._TimerCallback.PerformTimerCallback(System.Object) 17fbe9dc 74071b4c [GCFrame: 17fbe9dc]
0:000> ~45e!dso OS Thread Id: 0xbcc (45) ESP/REG Object Name 17fbe5a8 022a2ff4 System.Globalization.DaylightTime 17fbe5ac 022a2f3c System.Int32 17fbe5c8 02537b88 MyProg.MyChildClass 17fbe738 02537b88 MyProg.MyChildClass 17fbe740 02537b88 MyProg.MyChildClass 17fbe7ac 11572f28 System.Collections.ArrayList+ArrayListEnumeratorSimple 17fbe7b0 022f3490 System.Collections.ArrayList 17fbe7b4 0231860c System.String Error loading MyConfig.txt 17fbe7c0 022f3014 MyProg.MyEngine 17fbe84c 0231b48c System.Threading._TimerCallback 17fbe9fc 0231b48c System.Threading._TimerCallback
0:000> ~290e !clrstack OS Thread Id: 0x1af8 (290) ESP EIP 2e77f39c 77d2013d [HelperMethodFrame_1OBJ: 2e77f39c] System.Threading.ReaderWriterLock.AcquireReaderLockInternal(Int32) 2e77f3f8 0c3630d4 MyProg.MyEngine.GetBuyValue() 2e77f424 076fd4ad MyProg.MyParentClass.Execute(System.Object) 2e77f474 71e19fcf System.Threading._ThreadPoolWaitCallback.WaitCallback_Context(System.Object) 2e77f47c 71e302ff System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object) 2e77f494 71e1a533 System.Threading._ThreadPoolWaitCallback.PerformWaitCallbackInternal(System.Threading._ThreadPoolWaitCallback) 2e77f4a8 71e1a3c9 System.Threading._ThreadPoolWaitCallback.PerformWaitCallback(System.Object) 2e77f638 74071b4c [GCFrame: 2e77f638]
0:000> ~290e!dso OS Thread Id: 0x1af8 (290) ESP/REG Object Name 2e77f35c 022f3014 MyProg.MyEngine 2e77f360 02369b98 System.Threading.ContextCallback 2e77f378 02369b98 System.Threading.ContextCallback 2e77f3dc 023188f8 System.Threading.ReaderWriterLock 2e77f400 024862d8 MyProg.MyChildClass 2e77f410 02369b98 System.Threading.ContextCallback 2e77f430 024862d8 MyProg.MyChildClass 2e77f43c 024862d8 MyProg.MyChildClass 2e77f460 02369b98 System.Threading.ContextCallback 2e77f490 1156dd74 System.Threading._ThreadPoolWaitCallback
回答1:
I think you should try the extension dll SOSEX written by this guy http://stevestechspot.com/, there is a !dlk command which tries to find deadlocks and he recently added some new commands which will be of interest for you:
!mlocks – Lists all managed locks and unmanaged CriticalSections, along with their owner thread ID. !mwaits – Lists all waiting threads and, if it can be determined, the lock objects they are waiting on.
来源：https://stackoverflow.com/questions/10939285/detecting-deadlock-in-a-hung-c-sharp-application-using-windbg