linux-kernel - Re: Question on lockdep and sysrq

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Message-ID: <4A177ECE.7080508@candelatech.com>
Date:	Fri, 22 May 2009 21:42:54 -0700
From:	Ben Greear <greearb@...delatech.com>
To:	Ming Lei <tom.leiming@...il.com>
CC:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Question on lockdep and sysrq - d

Ming Lei wrote:
> See http://marc.info/?l=linux-kernel&m=124211522525625&w=2.
>   
That is about some real bug in the official kernel.  I am almost 100%
certain that my own code is at fault here.

I'm just trying to better understand the way lockdep prints out
all of the locks so I can easier debug my issue.

Thanks,
Ben

> thanks.
>
> 2009/5/23 Ben Greear <greearb@...delatech.com>:
>   
>> Hello!
>>
>> I'm trying to debug an apparent deadlock in some code I'm
>> writing.
>>
>> When I do a sysrq 'd', I get a nice dump of locks (I have lockdep enabled).
>>
>> However, the output appears to show multiple processes holding the
>> same locks (rtnl_mutex, for example):
>>
>> Showing all locks held in the system:
>> 3 locks held by events/11/63:
>>  #0:  (events){--..}, at: [<ffffffff8104f71e>] run_workqueue+0xb1/0x216
>>  #1:  ((linkwatch_work).work){--..}, at: [<ffffffff8104f71e>]
>> run_workqueue+0xb1/0x216
>>  #2:  (rtnl_mutex){--..}, at: [<ffffffff8125def1>] rtnl_lock+0x12/0x14
>> 1 lock held by irqbalance/3360:
>>  #0:  (rtnl_mutex){--..}, at: [<ffffffff8125def1>] rtnl_lock+0x12/0x14
>> 1 lock held by hald/3605:
>>  #0:  (rtnl_mutex){--..}, at: [<ffffffff8125def1>] rtnl_lock+0x12/0x14
>> ...
>>
>> Is this merely showing processes that are blocked on trying to acquire these
>> locks?
>>
>> If so, is there any way to tell which processes have fully acquired locks
>> v/s
>> just waiting to acquire them?
>>
>> Thanks,
>> Ben
>>     

-- 
Ben Greear <greearb@...delatech.com> 
Candela Technologies Inc  http://www.candelatech.com


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