wkspace failed allocations with heap protection enabled

[Joel Sherrill]

On Wed, Apr 13, 2022 at 10:51 AM Matthew J Fletcher <amimjf at gmail.com>
wrote:

> Hi Joel,
>
> Works fine without debug, its the deferred free doing _Heap_Allocate with
> the negative size thats causing it.
>

Glad that workaround gets you by it. Please do file a ticket though. :)

--joel

>
>
> On Wed, 13 Apr 2022 at 16:09, Joel Sherrill <joel at rtems.org> wrote:
>
>> This appears to be a bad side-effect of the way the deferred free is
>> implemented
>> when the memory protection/fence is enabled. This is turned on by
>> enabling
>> rtems debug.
>>
>> I'd recommend filing a ticket and assigning it to Sebastian for a real
>> fix.
>>
>> In the meantime, see if building RTEMS without debug enabled helps.
>>
>> --joel
>>
>> On Wed, Apr 13, 2022 at 4:30 AM Matthew J Fletcher <amimjf at gmail.com>
>> wrote:
>>
>>> Hi,
>>>
>>> Investigating the "Total number of failed allocations:" from the
>>> wkspace cmd i see that;
>>>
>>>     /* Statistics */
>>>     ++stats->failed_allocs;
>>>
>>> Are incremented when _Heap_Allocate_aligned_with_boundary fails, however
>>> it
>>> seems this will routinely fail due to;
>>>
>>> _Heap_Protection_free_all_delayed_blocks seemingly on purpose creating an
>>> impossibly large allocation.
>>>
>>>     uintptr_t large = 0
>>>       - (uintptr_t) HEAP_BLOCK_HEADER_SIZE
>>>       - (uintptr_t) HEAP_ALLOC_BONUS
>>>       - (uintptr_t) 1;
>>>
>>>     void *p = _Heap_Allocate( heap, large );
>>>
>>> This makes it difficult to place a breakpoint on failed_allocs to
>>> investigate true low memory situations with heap protection enabled.
>>>
>>>
>>> regards
>>> ---
>>> Matthew J Fletcher
>>> _______________________________________________
>>> users mailing list
>>> users at rtems.org
>>> http://lists.rtems.org/mailman/listinfo/users
>>>
>>
>
> --
>
> regards
> ---
> Matthew J Fletcher
>
>