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

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

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Roderik_Wildenburg@domain.hid wrote:
>> First of all, I'm not sure if that 8K of stack is enough on 
>> PPC with 2.4, on x86 over 2.6 it isn't. The native skin picks 
>> PTHREAD_STACK_MIN*4 for you by default. Is this too much? 
>> Unless dealing with dozens of
>> *simple* threads, reducing this makes no sense to me.
> 
> ?? Greping for PTHREAD_STACK_MIN xenomai/posix/pthread.h tells me, 
> it is 1024. 1024*4=4096. This is less than 8192 ;-)

That's for the kernel-space usage of the posix skin. In user-space you
have to look at /usr/include:

/usr/include/bits/local_lim.h:#define PTHREAD_STACK_MIN 16384
(glibc-2.4, x86 of course)

> Is there a differnce between x86 and PPC.
> (I simply did not realize that there is a default value for 
> the stacksize. Therfore I choose my own value, which was based on my 
> vxWorks experince)

Again, that /might/ be fine on PPC, cannot tell.

> 
> 
>> Then there was this bug:
>>
>> @@ -168,13 +169,13 @@
>>  void root_thread_exit(void)
>>  {
>>     int i;
>> -   RT_HEAP_INFO *hpinfo;
>> +   RT_HEAP_INFO hpinfo;
>>
>>     printf("UDP->root_thread_exit\n");
>>
>>     for(i=0;i<MAXHEAPBLOCKS;i++)
>>     {
>> -      if( !rt_heap_inquire(&bigheap[i],hpinfo) )
>> +      if( !rt_heap_inquire(&bigheap[i],&hpinfo) )
>>           rt_heap_delete(&bigheap[i]);
>>     }
> 
> Thank you ! 4 eyes see more than 2.
> (but this is probably not the reason for the segmentation fault, as 
> this routine is called for exit only !?)

True.

> But even after correcting this error, I get segmentation faults (not
> with 
> the first start but with the second or third)
> 
> 
>> Now I get some other strange effects (e.g. kernel oopses after OOM
>> oopses) that need a closer look under qemu later.
> 

I re-tried the setup, but was "only" able to find a 2.6-kernel bug in
the OOM roll-back path of vmalloc (2.4 is unaffected). The other issue,
totally failing rt_heap_alloc, was not reproducable. I must have messed
something up on the test box at work.

So this means I cannot trigger your problem here on x86/2.6, sorry.

Jan


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