Problem with rtems_task_variable_delete

[Till Straumann]

RTM (see below)


Dieter.B.Schaefer at t-online.de wrote:

>>On Tue, 09 Dec 2003 01:18:32 -0800 (PST), "Fernando RUIZ CASAS" wrote:
>>
>>After browsing in the versions of sources the problem was fixed.
>>
>>
>>http://www.rtems.com/cgi-bin/cvsweb.cgi/rtems/cpukit/rtems/src/tasks.c.diff?r1=1.34&r2=1.35
>>
>>In tasks.c the problem can be isolated again.
>>
>> while (tvp) {   
>>     next = tvp->next;      
>>     if  (tvp->dtor)     
>>         (*tvp->dtor)( tvp->ptr ); <<< HERE the change and the source of the problem.          
>>     if (executing == deleted)      
>>         *tvp->ptr = tvp->gval;          
>>     _Workspace_Free( tvp );      
>>
>>Some printk let to show the dtor, the ptr, and more...
>>I can't test it. Sorry.
>>
>>    
>>
>
>Thank's for the hint. I had already modified this before. Unfortunately, 
>it's not the solution. Here is what happens ... 
>free(...) is called with the correct value 
>|-> calles rtems_region_return_segment(...)
>                |-> calles _RTEMS_Lock_allocator()
>                                |-> calles _Internal_error_Occured(...)
>                                               |-> calles _BSP_Fatal_error(...)
>-> the end of the world.
>Any ideas, any hints from RTEMS professionals?
>

As I already pointed out: the task variable destructor is called from a 
section of code which
is protected by 'disabling thread dispatching'. It is ILLEGAL to call 
'free()' from such a section.
_CORE_mutex_Seize() (called indirectly by 'free()' when it acquires the 
allocator lock)
detects the violation and raises 'Internal_error_Occurred()'.

PR#504 introduced this safeguard. Prior to PR504 everything would "work" 
but the heap
was corrupted!

You must not use 'free' as a task variable dtor (or use the modified 
'free()' I posted earlier
to work around this problem)

HTH

-- Till

PS: You guys might want to read the threads

         'Possible bug in _CORE_mutex_Seize()' discussed around 2003/9/30

       and

          'More heap corruption / allocator lock problems' discussed 
aroung 2003/10/7

>
>BTW, did someone manage to run *all* spxx tests on a mbx8xx board 
>successfully? Would be interesting to know if they all work with the 
>unmodified BSP supplied in the source tree (rtems-4.6.0pre5)
>
>Regards
>Dieter Schaefer
>
>
>
>  
>