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

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

Jan Kiszka wrote:
 > 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.

On some architectures vmalloced memory is only added to a process page
directory when the fault occurs. I do not know if the RAM allocation is
delayed until then, though.

-- 


					    Gilles Chanteperdrix.