Query about: ARM11 MPCore: preemption/task migration cache coherency

[Andrew Yan-Pai Chen]

On Tue, Jun 5, 2012 at 12:50 PM, bill4carson <bill4carson at gmail.com> wrote:
> Hi, Geroge
>
> thanks for your updates.
>
>
>
> On 2012年06月05日 12:06, George G. Davis wrote:
>>
>> Hello,
>>
>> On May 9, 2012, at 5:11 AM, bill4carson wrote:
>>
>>> Hi, All
>>>
>>> I'm using ARM11 MPCore on linux-2.6.34, unfortunately I have random
>>> panic/segment fault with task migration. I noticed a patch set
>>> [ARM11 MPCore: preemption/task migration cache coherency fixups] to fix
>>> such issues in here:
>>>
>>
>>>
>>> http://lists.infradead.org/pipermail/linux-arm-kernel/2011-October/069851.html
>>>
>>> It seems there is no follow ups, is there official patch to fix such
>>> issues?
>>
>>
>> Apologies for the delayed reply.  Yes, I believe those patches are still
>> needed
>> for ARM11 MPCore, even when not using PREEMPT.  I vaguely recall at least
>> two cases where problems occurred w/o those patches, 1) LTP stress would
>> randomly fail, and 2) parallel module loading would invariably oops with a
>> random fault, with results similar to what you've reported later in this
>> thread.
>> The most reliable test case to reproduce the failure was the parallel
>> module
>> loading.  LTP stress test runs took a long time to trigger the errors.
>>
>> I'm dusting off the patches and trying to resurrect the test cases to see
>> if I can
>> reproduce the errors on latest kernel.org.  I'll followup with results in
>> a day or
>> so.  FWIW,   I've got LTP stress running on latest kernel.org now but
>> probably
>> should have resurrected the parallel module loading test case instead, as
>> LTP stress may take awhile to reproduce the error, if at all.
>>
>> --
>> Regards,
>> George
>>
>>>
>>>
>>> thanks
>>>
>>> --
>>> Love each day!
>>>
>>> --bill
>>
>>
>>
>
> --
> Love each day!
>
> --bill
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Hi all,

When PREEMPT disabled, is it possible that a kernel thread which performs
DMA transfers (such like dmatest) is migrated to other CPUs when it is
executing the DMA cache maintenance operations?
If so, isn't it needed to prevent task migration in DMA cache maintenance
operations (or in dma_map_single()) for ARMv6MPCore?

--
Regards,
Andrew