Re: sysrq+t doesn't work for some threads

[Robert Hancock <hancockr@shaw.ca>]

Bernd Schubert wrote:
> Hello,
> 
> I need to debug a lustre problem, where lustre threads take 100% cpu time and 
> also have a memory leak. The problem is, that sysrq+t doesn't work for these 
> threads. It nicely shows all stack traces, just the trouble some threads 
> won't show their traces:
> 
> [69338.858825] ll_mdt_36     R  running task       0 21679      2 (L-TLB)

This means this task is running, you won't get a stack trace for such a 
thread. You'd likely have to stop it somehow. Is this a kernel thread?

> [69338.865689] ll_mdt_37     S 0000000000000000     0 21680      2 (L-TLB)
> [69338.872676]  ffff8102e6d01dd0 0000000000000046 ffffffff88160325 
> 00000000ffffffed
> [69338.880544]  0000000000000000 ffffffff8815e016 000000000000000a 
> ffff810322ef4ea0
> [69338.888318]  ffff81031e7477b0 00003f0797609cef 000000000003434e 
> ffff810322ef5050
> [69338.895957] Call Trace:
> [69338.898787]  [<ffffffff8828cab5>] :ptlrpc:ptlrpc_main+0xa55/0x1ce0
> [69338.905297]  [<ffffffff8020a2f8>] child_rip+0xa/0x12
> 
> 
> But I really need to have the trace of ll_mdt_36, which is one of the 
> troublesome threads. Might this be a problem of the x86_64-mm-unwinder.patch 
> we always apply since it provides much better traces?
> This is with 2.6.22.19.
> 
> Any help would be appreciated.