ARM RTEMS SMP Support

[Xi Yang]

On 14 February 2013 10:39, Joel Sherrill <joel.sherrill at oarcorp.com> wrote:
>
> Xi
>
> Can you post the URL for your project? And a general bit
> on the status and target. That way if someone wants to help,
> everything will be right here.

I am doing a research project for my PhD, which is using M3 cores to
do garbage collection for the JVM. The JVM is running on big A9 cores.
I don't have a URL for that. I will post the paper and code URL to the
mailing list after it is accepted.


Regards.
>
> --joel
>
> On 2/13/2013 4:56 PM, Xi Yang wrote:
>>
>> Hi Joel,
>>
>> On 14 February 2013 05:37, Joel Sherrill <joel.sherrill at oarcorp.com>
>> wrote:
>>>
>>> You just threw down the gauntlet to Xi Yang!! Time to
>>> merge. :)
>>>
>>> On 2/13/2013 12:02 PM, Claus, Ric wrote:
>>>
>>> SMP is not available for ARM?  That's a big issue for me.  What's
>>> involved
>>> to provide that support?
>>>
>>> Compared to writing a BSP from scratch, not much. :)
>>>
>>> You can look at either the pc386 or leon3 BSPs and associated
>>> ports for an idea of how much code is architecture
>>> and BSP specific.
>>>
>>> Or even better.. help us merge the GSOC project by Xi Yang.
>>
>> Sorry, Joel. I was too busy to clean the code. I will try my best to
>> submit the patches as soon as possible.
>>
>> By the way, I am doing a research project which is using RTEMS as the
>> kernel for the small M3 ARM cores.
>>
>>
>> Regards.
>>
>>> http://www.rtems.com/ml/rtems-users/2012/august/msg00084.html
>>> has a github link. I suspect there may be some BSP or CPU model
>>> variation between his work and yours.
>>>
>>> Our atomic code is based off that in FreeBSD. So this would be the
>>> starting point for the atomic.h support.
>>>
>>>
>>> http://svnweb.freebsd.org/base/head/sys/arm/include/atomic.h?view=log&pathrev=151334
>>>
>>> --joel
>>>
>>> Ric
>>>
>>> ________________________________________
>>> From: rtems-devel-bounces at rtems.org [rtems-devel-bounces at rtems.org] On
>>> Behalf Of Joel Sherrill [joel.sherrill at OARcorp.com]
>>> Sent: Wednesday, February 13, 2013 8:42 AM
>>> To: yangwei weiyang
>>> Cc: RTEMS Devel
>>> Subject: Re: [rtems commit] tests: atomic support for RTEMS. Uniprocessor
>>> tests for atomic ops.
>>>
>>> On 2/13/2013 10:28 AM, yangwei weiyang wrote:
>>>
>>> OK i am studying how to implement a common ISR_Disable and ISR_Enable
>>> ops to simulate atomic ops. But it is just for the UP architectures,
>>> for SMP architectures which are not supported by atomic now this will
>>> not be suitable.
>>>
>>> That's OK. The only architectures we currently support SMP on are
>>> x86 and SPARC (only for LEON3).  Beyond powerpc and arm, I think
>>> it is unlikely we will have SMP.
>>>
>>> In general terms, if the CPU doesn't have atomic instructions
>>> to implement these with, then it is very unlikely to ever show
>>> up in an SMP configuration.  This makes the ISR disable/enable
>>> implementation suitable for UP.
>>>
>>> My biggest concerns is more general. I envision two common
>>> scenarios within a single architecture:
>>>
>>> + certain cpu models or architecture revisions have atomic
>>>      instructions and some don't. But this is defined in the
>>>     architecture and can be handled in cpukit. ISR disable/enable
>>>      in some cases, real atomic in others.
>>> + Similar case but CPU models have pulled instructions from
>>>      architectural revisions "above" them. The instruction is
>>>      there but not part of the real architectural revision the CPU
>>>      model is based upon.
>>>
>>> The isr disable/enable implementation may need to be available
>>> all the time as a fallback.
>>>
>>> --joel
>>>
>>>
>>>
>>> --
>>> Joel Sherrill, Ph.D.             Director of Research & Development
>>> joel.sherrill at OARcorp.com        On-Line Applications Research
>>> Ask me about RTEMS: a free RTOS  Huntsville AL 35805
>>> Support Available                (256) 722-9985
>
>
>
> --
> Joel Sherrill, Ph.D.             Director of Research & Development
> joel.sherrill at OARcorp.com        On-Line Applications Research
> Ask me about RTEMS: a free RTOS  Huntsville AL 35805
> Support Available                (256) 722-9985
>