disable thread dispatch problem

[Ashi]

2012/7/6 Joel Sherrill <joel.sherrill at oarcorp.com>

> On 07/06/2012 04:49 AM, Ashi wrote:
>
>> Hi, all.
>> I've a problem of _Thread_Disable_dispatch() function in below code. It's
>> my implementation of _POSIX_Keys_Run_destructors() function. I come across
>> the problem when I run the psxkey03 test:if _Thread_Disable_dispatch() was
>> commented out, psxkey03 can run without problem. when
>> _Thread_Disable_dispatch() added at line 1(as below), psxkey03 will fail. I
>> debug it in sparc-rtems4.11-gdb, and find psxkey03 runs into
>> _Internal_error_Occurred() function then stop. I know _POSIX_Keys_Get()(at
>> line 12) will also disable thread dispatch--does this lead to the problem?
>> However, can't figure out where exactly the problem exists, could anyone
>> explain it? Thanks!
>>
>
> This call chain goes back to score/src/threadclose.c and this section of
> code.
>
>   /*
>    *  We assume the Allocator Mutex is locked when we get here.
>    *  This provides sufficient protection to let the user extensions
>    *  run but as soon as we get back, we will make the thread
>    *  disappear and set a transient state on it.  So we temporarily
>    *  unnest dispatching.
>    */
>   _Thread_Unnest_dispatch();
>
>   _User_extensions_Thread_**delete( the_thread );
>
>  **** you are called in this state ***
>   - mutex allocator locked
>   - dispatching disabled (level = 1)
>
> I find the mutex allocator's work is protection for all memory allocations
and deallocations, does it mean I can't call _Workspace_Free at line 17?

>
>
>>   1 _Thread_Disable_dispatch();
>>
>>   2 chain = &((POSIX_API_Control *)thread->API_Extensions[
>> THREAD_API_POSIX ])->the_chain;
>>   3 iter = _Chain_First( chain );
>>   4 while ( !_Chain_Is_tail( chain, iter ) ) {
>>   5 next = _Chain_Next( iter );
>>   6  /**
>>   7   * here Chain_Node *iter can be convert to POSIX_Keys_Rbtree_node *,
>>   8   * because Chain_Node is the first member of POSIX_Keys_Rbtree_node
>> structure.
>>   9   */
>>   10  _RBTree_Extract_unprotected( &_POSIX_Keys_Rbtree,
>> &((POSIX_Keys_Rbtree_node *)iter)->rb_node );
>>   11 _Chain_Extract_unprotected( iter );
>>
>>  Thread dispatching is disabled here to level 1.
>
>    12  the_key = _POSIX_Keys_Get( ((POSIX_Keys_Rbtree_node *)iter)->key,
>> &location);
>>
> This nests the dispatching level to 2.
>
>
I would move your code below the _POSIX_Keys_Get() call. There are logically
> two actions: key removal from rbtree and run the destructor. Put comments
> above each block of code indicating what is happening LOGICALLY. Everyone
> can read the code.
>
> If order is important between the two blocks, document it. I am assuming
> your
> block will move between lines 12 and 13.
>
> Sorry, Joel, I haven't quite got your idea, what do you mean by "move code
below the _POSIX_Keys_Get() call"?

However, I test the code after add a _Thread_Enable_dispatch() between line
16 and 17, and the error is gone. Is it a proper solution to my problem?

>    13  destructor = the_key->destructor;
>>   14  value = ((POSIX_Keys_Rbtree_node *)iter)->value;
>>   15  if ( destructor != NULL && value != NULL )
>>   16    (*destructor)( value );
>>
>>   17  _Workspace_Free( (POSIX_Keys_Rbtree_node *)iter );
>>   18  iter = next;
>>   19}
>>
>>   20_Thread_Enable_dispatch();
>>
>> ---
>> Best regards!
>> Zhongwei Yao
>>
>>
>
> --
> Joel Sherrill, Ph.D.             Director of Research&   Development
> joel.sherrill at OARcorp.com        On-Line Applications Research
> Ask me about RTEMS: a free RTOS  Huntsville AL 35805
>     Support Available             (256) 722-9985
>
>
>


-- 
Best wishes!
Zhongwei Yao
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.rtems.org/pipermail/devel/attachments/20120709/5e9c1d92/attachment-0001.html>