Re: unable to handle kernel NULL pointer dereference on 3.18.13-rt10

[Gratian Crisan <gratian.crisan@ni.com>]

On 07/24/2015 02:21 PM, Steven Rostedt wrote:
> On Fri, 24 Jul 2015 21:02:26 +0200 (CEST)
> Thomas Gleixner <tglx@linutronix.de> wrote:
> 
>> On Wed, 22 Jul 2015, Steven Rostedt wrote:
>>> It's still there. Note, that when I pull -rt into stable, I do a
>>>  git quiltimport, which renames the patch set. It's now called:
>>>
>>>  0089-slub-delay-ctor-until-the-object-is-requested.patch
>>
>> >From the 4.0.8-rt6 announce:
>>
>> - The delayed kmem_cache constructor caused problems. Steven Rostedt
>>   reported problems versus the signal handling code and Koehrer
>>   Mathias reported the same. The patch in question has been reverted
>>   and a patch currently sitting in -mm has been added which provides
>>   the same functionality (running the constructor with enabled
>>   interrupts). Patch provided by Thomas Gleixner. 
>>
>> The stable trees which carry the delay-ctor patches should be updated
>> to this.
>>
>> Reverting the patch at least prevents the BUG. Latencywise the slub patch
>>
>>    mm-slub-move-slab-initialization-into-irq-enabled-re.patch
>>
>> is the one which wants to be ported back.
>>
> 
> OK, thanks.
> 
> Just to let people know. I'm going to be traveling next week and when I
> get back in August, my top priority is to work on the stable patches.
> For 3.18, I'll be looking at the patches that have been emailed to the
> list, and I want to fix NO_HZ for 3.10-3.14.
> 

In case it saves you some work, we've had some success getting NO_HZ to
work on 3.14 (x86_64) after back-porting the following commit:

3010279f0fc36f0388872203e63ca49912f648fd x86: Tell irq work about self
IPI support

-Gratian