Debugging a Deadlock with Windbg's !clrstack command

Question

When I issued clrstack command, I got the following output. It is the callstack of a blocking thread which owns a deadlock and results in a deadlock. Is that its exact purpose? Does it have any other purposes (without any parameters). Where can I get more information?

!clrstack
OS Thread Id: 0x1b2c (6956)
ESP       EIP     
0012f370 7c90e514 [HelperMethodFrame: 0012f370] System.Threading.Thread.SleepInternal(Int32)
0012f3c4 79299275 System.Threading.Thread.Sleep(Int32)
0012f3c8 00e0030f testlock.LockTest.Test()
0012f420 00e00146 testlock.Program.Main(System.String[])
0012f69c 79e71b4c [GCFrame: 0012f69c] 

Solution 1

How to: Debug Deadlocks Using Windbg?

WinDbg / SOS Cheat Sheet

CLRStack [-a] [-l] [-p] [-n] Provides a stack trace of managed code only.

• The -p option shows arguments to the managed function.

• The -l option shows information on local variables in a frame. The SOS Debugging Extension cannot retrieve local names, so the output for local names is in the format = .

• The -a(all) option is a shortcut for -l and -pcombined.

• The -n option disables the display of source file names and line numbers. If the debugger has the option SYMOPT_LOAD_LINES specified, SOS will look up the symbols for every managed frame and if successful will display the corresponding source file name and line number. The -n (No line numbers) parameter can be specified to disable this behavior.

The SOS Debugging Extension does not display transition frames on x64 and IA-64-based platforms.

Update: (Thanks to @Liran): To see the call stacks for all the threads in your application, run the following command:

 ~*e!clrstack 

(which basically means, "iterate over all of the threads, and execute the command '!clrstack' on every one of them").

Solution 2

Use sosex by Steve Johnson. This has a command to detect deadlocks for you.

Download the extension from the link and load it, eg

.load D:\sosex_32\sosex.dll

then issue

!dlk

example output (taken from steve's site)

0:010> !dlk Deadlock detected: CLR thread 4 holds sync block 00000000024c6970 OBJ:000000007fff0f80[System.String] STRVAL=SYNC1 waits sync block 00000000024c6928 OBJ:000000007fff0fa8[System.String] STRVAL=SYNC2 CLR thread 5 holds sync block 00000000024c6928 OBJ:000000007fff0fa8[System.String] STRVAL=SYNC2 waits sync block 00000000024c6970 OBJ:000000007fff0f80[System.String] STRVAL=SYNC1 CLR Thread 4 is waiting at ConsoleTestApp.ConsoleTestApp.MonitorDeadlockThreadProc()+0xa4(IL) [C:\dev\ConsoleTestApp\ConsoleTestApp.cs, line 195] CLR Thread 5 is waiting at ConsoleTestApp.ConsoleTestApp.MonitorDeadlockThreadProc()+0xa4(IL) [C:\dev\ConsoleTestApp\ConsoleTestApp.cs, line 195]

See also this link for a walkthrough

Solution 3

Tess has blogged lots of useful information about windbg. Here is one post that might help.

Comments

[Maanu]

Thanks for the reply.. My application has 2 threads. But the !clrstack command displayed the callstack of only one thread. I have gone through the documents before posting the question..

[Liran]

@Maanu, this command is issued per-thread. In order to issue it for all the threads in your application, you will need to use the following command: ~*e!clrstack (which basically means, "iterate over all of the threads, and execute the command '!clrstack' on every one of them").