netdev - Re: [BUG] RTNL and flush_scheduled

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Date:	Fri, 16 Feb 2007 08:06:25 -0800
From:	Ben Greear <greearb@...delatech.com>
To:	Jarek Poplawski <jarkao2@...pl>
CC:	Stephen Hemminger <shemminger@...ux-foundation.org>,
	Francois Romieu <romieu@...zoreil.com>, netdev@...r.kernel.org,
	Kyle Lucke <klucke@...ibm.com>,
	Raghavendra Koushik <raghavendra.koushik@...erion.com>,
	Al Viro <viro@....linux.org.uk>
Subject: Re: [BUG] RTNL and flush_scheduled_work deadlocks

Jarek Poplawski wrote:
> On Fri, Feb 16, 2007 at 10:04:25AM +0100, Jarek Poplawski wrote:
>   
>> On Fri, Feb 16, 2007 at 12:23:05AM -0800, Ben Greear wrote:
>>     
> ...
>   
>>> I don't see how asserting it in the rtnl_lock would help anything, 
>>> because at that
>>> point we are about to deadlock anyway...  (and this is probably very 
>>> rare, as mentioned above.)
>>>       
>> But it's happening now. Probably lockdep is not enough
>> and rtnl_lock is probably used in too many places, so I
>> meant some additional checks would be possible.
>>     
>
> And of course it already could be done by DEBUG_MUTEXES or
> DEBUG_SPINLOCK, so I gone too far and it's really bad idea.
>   

Well, I had lockdep and all of the locking debugging I could find 
enabled, but
it did not catch this problem..I had to use sysctl -t and manually dig 
through the backtraces
to find the deadlock....

It may be that lockdep could be enhanced to catch this sort of thing....

Ben

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


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