linux-kernel - Re: [GIT PULL rcu/next] rcu commits for 2.6.40

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Message-ID: <4DCA26CD.80305@kernel.org>
Date:	Tue, 10 May 2011 23:03:57 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	paulmck@...ux.vnet.ibm.com
CC:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: [GIT PULL rcu/next] rcu commits for 2.6.40

On 05/10/2011 09:54 PM, Paul E. McKenney wrote:
> On Tue, May 10, 2011 at 01:52:52PM -0700, Yinghai Lu wrote:
>> On 05/10/2011 12:32 PM, Paul E. McKenney wrote:
>>> On Tue, May 10, 2011 at 11:04:57AM -0700, Yinghai Lu wrote:
>>>> On 05/10/2011 01:56 AM, Paul E. McKenney wrote:
>>>>> On Mon, May 09, 2011 at 02:09:21PM -0700, Yinghai Lu wrote:
>>>>>> On Mon, May 9, 2011 at 12:36 AM, Ingo Molnar <mingo@...e.hu> wrote:
>>>>>>>
>>>>>>> * Paul E. McKenney <paulmck@...ux.vnet.ibm.com> wrote:
>>>>>>>
>>>>>>>> Hello, Ingo,
>>>>>>>>
>>>>>>>> This pull request covers RCU chnages for 2.6.40.  The major new features
>>>>>>>> are RCU priority boosting and the addition of kfree_rcu(), the latter
>>>>>>>> courtesy of Lai Jiangshan.  These two features cover well over half
>>>>>>>> of the commits.  There are a number of smaller features and bug fixes.
>>>>>>>> All have been sent to LKML in the following batches:
>>>>>>>>
>>>>>>>> 0.    https://lkml.org/lkml/2011/2/22/660: RCU priority boosting preview
>>>>>>>> 1.    https://lkml.org/lkml/2011/5/1/19: RCU priority boosting, kfree_rcu()
>>>>>>>> 2.    https://lkml.org/lkml/2011/5/2/40: More uses of kfree_rcu()
>>>>>>>> 3.    https://lkml.org/lkml/2011/5/8/60: miscellaneous
>>>>>>>>
>>>>>>>> The kfree_rcu() uses in the pull request have Acked-by:s from the
>>>>>>>> maintainers.  I have some additional kfree_rcu() requests that lack
>>>>>>>> Acked-by:s, and I will deal with these later.
>>>>>>>>
>>>>>>>> These channges are available in the -rcu git repository at:
>>>>>>>>
>>>>>>>>   git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-2.6-rcu.git rcu/next
>>>>>>>
>>>>>>> Pulled, thanks a lot Paul!
>>>>>>>
>>>>>>
>>>>>> it seems with this one in tip, my 8 sockets test setup will report cpu stall.
>>>>>>
>>>>>> after hard code to enable rcu_cpu_stall_suppress
>>>>>>
>>>>>> Index: linux-2.6/kernel/rcutree.c
>>>>>> ===================================================================
>>>>>> --- linux-2.6.orig/kernel/rcutree.c
>>>>>> +++ linux-2.6/kernel/rcutree.c
>>>>>> @@ -174,7 +174,7 @@ module_param(blimit, int, 0);
>>>>>>  module_param(qhimark, int, 0);
>>>>>>  module_param(qlowmark, int, 0);
>>>>>>
>>>>>> -int rcu_cpu_stall_suppress __read_mostly;
>>>>>> +int rcu_cpu_stall_suppress __read_mostly = 1;
>>>>>>  module_param(rcu_cpu_stall_suppress, int, 0644);
>>>>>>
>>>>>>  static void force_quiescent_state(struct rcu_state *rsp, int relaxed);
>>>>>>
>>>>>> will get system hang after pnp ACPI init.
>>>>>
>>>>> Could you please send the stack traces from the RCU CPU stall?  Also,
>>>>> you do have ce31332d3c77532d6ea97ddcb475a2b02dd358b4 applied, correct?
>>>>>
>>>>> 							Thanx, Paul
>>>>
>>>> Do not have time to bisect it at this point.
>>>
>>> Could you please send the stack traces from the RCU CPU stall?
> 
> Thank you!  OK, so CPU 0 has not been responding, despite resched IPIs.
> Everyone is idle, except for CPU 124, which detected the stall, and
> possibly CPU 0, which has csum_partial_copy_generic() on the stack, though
> that looks like a backtrace error to me.  The fact that it hangs if you
> disable RCU CPU stall detection leads me to believe that something real
> is being detected.
> 
> This looks very similar to the situation people were seeing before
> ce31332d3c77532d6ea97ddcb475a2b02dd358b4 was applied, so I have attached
> the diagnostic script that helped track this down.  Could you please
> enable CONFIG_RCU_TRACE, mount debugfs, and run the attached script,
> and send me the output?  Please check to make sure that the script knows
> where you mounted debugfs, of course.
> 

so which kernel that i should boot?

that is during boot stage.

assume at least i need to boot to shell to run your scripts.

Thanks

Yinghai
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