Re: workqueue, pci: INFO: possible recursive locking detected

[Lai Jiangshan]

On 07/23/2013 10:38 PM, Tejun Heo wrote:
> Hey, Lai.
> 
> On Tue, Jul 23, 2013 at 09:23:14AM +0800, Lai Jiangshan wrote:
>> The problem is that the userS may not know their work_on_cpu() nested,
>> especially when work_on_cpu()s are on different subsystems and the call depth
>> is deep enough but the nested work_on_cpu() depends on some conditions.
> 
> Yeah, that's a possibility.  Not sure how much it'd actually matter
> tho given that this is the only instance we have and we've had the
> lockdep annotation for years.
> 
>> I prefer to change the user instead of introducing work_on_cpu_nested(), and
>> I accept to change the user only instead of change work_on_cpu() since there is only
>> one nested-calls case found.
>>
>> But I'm thinking, since nested work_on_cpu() don't have any problem,
>> Why workqueue.c don't offer a more friendly API/behavior?
> 
> If we wanna solve it from workqueue side, let's please do it by
> introduing an internal flush_work() variant which skips the lockdep
> annotation.  I'd really like to avoid using completion here.  It's
> nasty as it depends solely on the fact that completion doesn't have
> lockdep annotation yet.  Let's do it explicitly.
> 
> Thanks.
>