cleaner & greener (was Re: A patch for RTEMS4.10.0 PowerPC heap space initialization)

Joel Sherrill joel.sherrill at
Tue May 17 19:10:07 UTC 2011

On 05/17/2011 01:20 PM, Till Straumann wrote:
> On 05/16/2011 11:59 PM, Chris Johns wrote:
>> On 17/05/11 5:27 AM, Kate Feng wrote:
>>> The PR is at
>>> Thanks for all the feedback. I am glad that the API is more or
>>> less verified. Previously, I could not decide where to place the macro.
>>> The patch for the mvme5500 BSP is updated as well at
>> Thanks for sorting this. I will leave the patches for Till to review and
>> commit.
> OK, will do.
> Note that there will be a slight asymmetry if you configure a unified
> work area and have sbrk support. While allocating from the unified heap
> via 'malloc()' then the heap is transparently extended via sbrk().
> However, the unified heap is *not* extended transparently when you
> allocate via _Workspace_Allocate() / rtems_workspace_allocate().
I must admit that never occurred to me.
> Given that the entire sbrk business is only required for special
> purposes I assume we can live with that asymmetry for now (and
> the unified heap can always be extended explicitly via 'sbrk'
> and _Heap_Extend()).
I guess so.  Until someone hits this wall personally, I don't
have a good perspective.  You will do a create of an RTEMS
object, likely with unlimited as an option, and it will fail.
Extend the heap, try again and it will work.

My concern now is that it will involve a change to a fundamental
behaviour and core piece of code.  You just have to be
careful when you start changing behaviour that is
essentially unchanged since the earliest days of RTEMS.
Technically possible but caution is the word until a user
hits this wall.

So in 2027 when someone finds this in the archive,
we can discuss it again. :D
> - Till
>> I have finished PR1774 so this is all that needs to be applied to start
>> the 4.10.1 release process.
>> Chris
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Joel Sherrill, Ph.D.             Director of Research&  Development
joel.sherrill at        On-Line Applications Research
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