Re: [Xenomai-help] memset of heap crashes Xenomai-Task

[Jan Kiszka <jan.kiszka@domain.hid>]

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Gilles Chanteperdrix wrote:
> Roderik_Wildenburg@domain.hid wrote:
>  > Xenomai Version : 2.2-rc2
>  > Skin : native
>  > Kernel : 2.4.25
>  > Arch.: PPC
>  > 
>  > I try to allocate as much memory as possible with the functions :
>  > rt_heap_create and
>  > rt_heap_alloc.
>  > (see also "Xenomai heap services" in this mailing list; see source
>  > attached)
>  > 
>  > When I try to use the allocated memory with memset, the Xenomai-task
>  > crashes with a "Segmentation fault".
>  > 
>  > Is memset allowed to be used with Xenomai heaps ?
> 
> memset should work with Xenomai heaps, I suspect your problem is rather
> that the memory is not really allocated until you memset it, which fails
> when no memory is available. In this case, calling memset on memory
> allocated with malloc should segfault the same way when the system
> memory is exhausted. IIRC, this behaviour is documented in mlockall
> manual page.

I wonder if this "virtual allocation" also applies to vmalloc'ed memory
like in this case. I don't think so, or the kernel would oops as well.

> 
> Be careful with sysconf(_SC_AVPHYS_PAGES), it may include the swap size,
> but when mlocking memory, your application can not use swap pages, so,
> you should substract the size of swap, if any.
> Also, what is the value of /proc/sys/vm/overcommit_memory on your system
> ?
> 

Jan


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