Re: [QUESTION ON BUG] the rcu stall issue could not be reproduced

[Michael Wang <wangyun@linux.vnet.ibm.com>]

On 07/20/2012 05:08 PM, Mike Galbraith wrote:
> On Fri, 2012-07-20 at 16:30 +0800, Michael Wang wrote: 
>> On 07/20/2012 03:00 PM, Mike Galbraith wrote:
>>> On Fri, 2012-07-20 at 11:09 +0800, Michael Wang wrote: 
>>>> Hi, Mike, Martin, Dan
>>>>
>>>> I'm currently taking an eye on the rcu stall issue which was reported by
>>>> you in the mail:
>>>>
>>>> rcu: endless stalls
>>>> 	From: Mike Galbraith
>>>> linux-3.4-rc7: rcu_sched self-detected stall on CPU
>>>> 	From: Martin Mokrejs
>>>> RCU stalls in linux-next
>>>> 	From: Dan Carpenter
>>>>
>>>> I try to reproduce the issue on my X86 server with 12 cpu
>>>
>>> The 'endless stalls' box was 341.33333 times larger.  Dunno if you can
>>> even set a serial port slow enough to approximate all cores trying to
>>> gripe through a single pinhole simultaneously.
>>
>> Hi, Mike
>>
>> Thanks for your reply.
>>
>> So you mean this issue is still existing on you box and you can see it
>> without doing any special things?
> 
> It's not my box (thank god).  It was initially triggered by tasks
> exiting simultaneously on all cores.  They jammed up, endless stall
> followed.
> 
>> I just want to try to reproduce it but it's impossible for me to get
>> some hardware as yours...
>>
>> So is there any idea on how to reproduce it on normal hardware?
> 
> No, AFAIK this problem is restricted to size XXL boxen, with all the
> joys that come along with having way too many CPUs.

I see, thanks for your info, looks like it's hard to reproduce on normal
servers like mine...

Regards,
Michael Wang
> 
> -Mike
>