i try to investigate a hung with windbg and want to know if my assumptions are right. If I call the command !mlocks i got the following:
0:000> !mlocks
Examining SyncBlocks...
Scanning for ReaderWriterLock instances...
Scanning for holders of ReaderWriterLock locks...
Scanning for ReaderWriterLockSlim instances...
Scanning for holders of ReaderWriterLockSlim locks...
Examining CriticalSections...
ClrThread DbgThread OsThread LockType Lock LockLevel
--------------------------------------------------------------------------
0x640064 -1 0xffffffff RWLock 000000000339a338 Writer
0x6 7 0x1ea8 thinlock 000000000343ddd8 (recursion:0)
When executeing rwlocks i got the following:
0:000> !rwlock 000000000339a338
WriterThread: 0x640064 (DEAD) WriterLevel: 115 WaitingWriterCount: 0
WriterEvent: 0
WaitingWriterThreadIds: None
ReaderCount: 116
CurrentReaderThreadIds:
WaitingReaderCount: 576
ReaderEvent: 80400002
WaitingReaderThreadIds:
*This lock has 116 orphaned reader locks.
0:007> !rwlock
Address ReaderCount WaitingReaderCount WriterThread WaitingWriterCount
...
000000000339a338 116 576 0x640064 0
...
00000000053f0688 568 499 -- 6
...
i got this. When I call
0:000> !dlk Examining SyncBlocks... Scanning for ReaderWriterLock instances... Scanning for holders of ReaderWriterLock locks... Scanning for ReaderWriterLockSlim instances...
Scanning for holders of ReaderWriterLockSlim locks...
Examining CriticalSections...
Scanning for threads waiting on SyncBlocks...
Scanning for threads waiting on ReaderWriterLock locks...
Scanning for threads waiting on ReaderWriterLocksSlim locks...
Scanning for threads waiting on CriticalSections...
No deadlocks detected.
then no deadlock will be detected. I found this on Tess's blog My question is if this threads have to do with my hunging application, and what the scenario could be. What does it mean that the thread is DEAD. Can a lock happen on a dead thread? Or do I have to find somewhere else root cause of my hunging application? Please help me to interpret this output.
Regards, Bernhard
Here is some addional info:
0:000> dc 000000000339a338
00000000`0339a338 f2073268 000007fe 00000000 80000000 h2..............
00000000`0339a348 f2066960 000007fe 00000010 00650047 `i..........G.e.
00000000`0339a358 00480074 0073006f 00410074 00640064 t.H.o.s.t.A.d.d.
00000000`0339a368 00650072 00730073 00730065 00000000 r.e.s.s.e.s.....
00000000`0339a378 00000000 00000000 00000000 00000000 ................
00000000`0339a388 f2066960 000007fe 0000001c 00650066 `i..........f.e.
00000000`0339a398 00300038 003a003a 00380034 00310038 8.0.:.:.4.8.8.1.
00000000`0339a3a8 0034003a 00660039 003a0063 00300039 :.4.9.f.c.:.9.0.
0:000> db 000000000339a338
00000000`0339a338 68 32 07 f2 fe 07 00 00-00 00 00 00 00 00 00 80 h2..............
00000000`0339a348 60 69 06 f2 fe 07 00 00-10 00 00 00 47 00 65 00 `i..........G.e.
00000000`0339a358 74 00 48 00 6f 00 73 00-74 00 41 00 64 00 64 00 t.H.o.s.t.A.d.d.
00000000`0339a368 72 00 65 00 73 00 73 00-65 00 73 00 00 00 00 00 r.e.s.s.e.s.....
00000000`0339a378 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
00000000`0339a388 60 69 06 f2 fe 07 00 00-1c 00 00 00 66 00 65 00 `i..........f.e.
00000000`0339a398 38 00 30 00 3a 00 3a 00-34 00 38 00 38 00 31 00 8.0.:.:.4.8.8.1.
00000000`0339a3a8 3a 00 34 00 39 00 66 00-63 00 3a 00 39 00 30 00 :.4.9.f.c.:.9.0.
0:000> !mdt 000000000339a338
Can't get name for module 000007ff0068c3c0. Error = 0x80070057.
Can't get name for module 000007ff00791908. Error = 0x80070057.
Can't get name for module 000007ff0068c3c0. Error = 0x80070057.
Can't get name for module 000007ff00791908. Error = 0x80070057.
000000000339a338 (System.Threading.ReaderWriterLock)
_hWriterEvent:8000000000000000 (System.IntPtr)
_hReaderEvent:000007fef2066960 (System.IntPtr)
_hObjectHandle:0065004700000010 (System.IntPtr)
_dwState:0x480074 (System.Int32)
_dwULockID:0x73006f (System.Int32)
_dwLLockID:0x410074 (System.Int32)
_dwWriterID:0x640064 (System.Int32)
_dwWriterSeqNum:0x650072 (System.Int32)
_wWriterLevel:0x0073 (System.Int16)
0:000> !mdt 000000000343ddd8
Can't get name for module 000007ff0068c3c0. Error = 0x80070057.
Can't get name for module 000007ff00791908. Error = 0x80070057.
000000000343ddd8 (System.Collections.Generic.LinkedList`1[[TAU.GuiAccess.PopupHandler.ClientInfo, TAU.GuiAccess.PopupHandler]])
head:000000000823e148 (System.Collections.Generic.LinkedListNode`1[[TAU.GuiAccess.PopupHandler.ClientInfo, TAU.GuiAccess.PopupHandler]])
count:0x1 (System.Int32)
version:0x3b (System.Int32)
_syncRoot:NULL (System.Object)
siInfo:NULL (System.Runtime.Serialization.SerializationInfo)
0:000> !do 000000000343ddd8
Name: System.Collections.Generic.LinkedList`1[[TAU.GuiAccess.PopupHandler.ClientInfo, TAU.GuiAccess.PopupHandler]]
MethodTable: 000007ff009ce218
EEClass: 000007ff009dda20
Size: 48(0x30) bytes
File: C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System\v4.0_4.0.0.0__b77a5c561934e089\System.dll
Fields:
MT Field Offset Type VT Attr Value Name
000007ff009ced28 4000586 8 ...ss.PopupHandler]] 0 instance 000000000823e148 head
000007fef206c848 4000587 20 System.Int32 1 instance 1 count
000007fef206c848 4000588 24 System.Int32 1 instance 59 version
000007fef2065ab8 4000589 10 System.Object 0 instance 0000000000000000 _syncRoot
000007fef208a1b8 400058a 18 ...SerializationInfo 0 instance 0000000000000000 siInfo
ThinLock owner 6 (0000000000000000), Recursive 0
The "DEAD" indication means that there is no corresponding OS thread. When a managed thread is created, a managed thread object is created and assigned a thread ID. On Windows, there is currently always a 1:1 mapping between managed and native threads, so there is also an OS thread ID assigned. When a thread terminates, the association between the managed thread object and the native thread is obviously broken. However, it takes a period of time before the managed thread object gets cleaned up. A thread in this state is listed by sosex as "DEAD" and is listed as XXXX in the !sos.threads output.
In this case, the CLR thread ID (00640064) looks suspicious. It looks curiously like Unicode text 'dd'. There may be corruption around the managed lock address. Look around with the debugger's 'dc' or 'db' commands to see if some text has overwritten the thread ID field.