Re: [PATCH] cpumask: remove cpumask allocation from idle_balance

[Jeremy Fitzhardinge <jeremy@goop.org>]

Ingo Molnar wrote:
> * Ingo Molnar <mingo@elte.hu> wrote:
>
>   
>>> This time for sure,
>>>       
>> not so sure:
>>
>> [    4.303068] =============================================================================
>> [    4.303332] BUG idr_layer_cache: Redzone overwritten
>> [    4.303332] -----------------------------------------------------------------------------
>> [    4.303332] 
>> [    4.303332] INFO: 0xffff88003f838958-0xffff88003f83895f. First byte 0xa1 instead of 0xbb
>> [    4.303332] INFO: Allocated in 0xffff88003f9b94b0 age=4294878587 cpu=2 pid=0
>> [    4.303332] INFO: Freed in 0xffff88003f8389f0 age=18446744073709463001 cpu=4294967295 pid=0
>> [    4.303332] INFO: Slab 0xffffe200015d5340 objects=13 used=10 fp=0xffff88003f838738 flags=0x40000000000020c3
>> [    4.303332] INFO: Object 0xffff88003f838738 @offset=1848 fp=0x(null)
>>     
>
> hm, i'm seeing this even with the cpus4096 bits removed.
>
> It _seems_ to trigger when i add these two commits:
>
>   71ff49d: x86: with the last user gone, remove set_pte_present
>   b40c757: x86/32: no need to use set_pte_present in set_pte_vaddr
>
> but i'm not completely sure it's related, i tried a bisection and it 
> showed heisenbug properties.
>
> Might have come from upstream, that saw some IDR changes recently.
>   

Seems very unlikely; those patches only touch 32-bit only code, and this 
looks like a 64-bit crash.

    J