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

From: Michael Wang
Date: Sun Jul 22 2012 - 22:37:49 EST

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...

Michael Wang
> -Mike

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