[ECOS] Seeking Thread join / waitpid equivalent.

[John Carter]

I have just found this rather ugly code in the tftp_server.c

So it kills the tftp server thread...
        cyg_thread_kill(server->thread_handle);

whangs the priority of the thread it killed as high as possible.
        cyg_thread_set_priority(server->thread_handle, 0);

Waits a random period for it to die
         cyg_thread_delay(1);  // Make sure it gets to die...

Deletes the thread...
         if (cyg_thread_delete(server->thread_handle)) {

If deleting the thread actually worked...

             // Success shutting down the thread
Frees the memory associated with the thread..
             free(server);  // Give up memory
             return 1;
         }
Else ... we have a memory leak.

See why I'm looking for a cleaner way to do this?


On Fri, 27 Aug 2004, John Carter wrote:

>
> Yes and no. What the guy was trying to do via a thread destructor
> would have been much more simply achieved via a thread.join in a
> reaper thread.
>
> thread_join(thread);
> cyg_thread_delete(thread.handle);
> free(thread.stack);
>
>> 	void
>> 	thread_entry_function(cyg_addrword_t data)
>> 	{
>> 	    struct myThreadType *thread = (struct myThreadType*)data;
>> 	    (*thread->entry_function)(thread->data);
>> 	    cyg_semaphore_post(&thread->death_semaphore);
>> 	}
>> 
>
>> 	void
>> 	thread_join(struct myThreadType *thread)
>> 	{
>> 	    cyg_semaphore_wait(&thread->death_semaphore);
>> 	}
>> 
>
>
> So if you are doing something like..
>
> thread_join(  &thread);
> cyg_thread_delete( thread.handle);
>
> unless the thread doing the join is of lower priority than the
> exiting thread there exists a narrow gap between the post and the end
> of cyg_thread_exit during which cyg_thread_delete can fail.
>
> ie. Fundamentally _any_ userland fix to this problem is not going to
> work.
>
> The only hack I can think of is to use something like your thread
> join, do the delete, test the result, if it failed sleep for a period,
> repeat with exponential fall off on the sleep period.
>
> Ugly ugly ugly.
>
>
>
>
>
> John Carter                             Phone : (64)(3) 358 6639
> Tait Electronics                        Fax   : (64)(3) 359 4632
> PO Box 1645 Christchurch                Email : john.carter@tait.co.nz
> New Zealand
>
> The universe is absolutely plastered with the dashed lines exactly one
> space long.
>



John Carter                             Phone : (64)(3) 358 6639
Tait Electronics                        Fax   : (64)(3) 359 4632
PO Box 1645 Christchurch                Email : john.carter@tait.co.nz
New Zealand

The universe is absolutely plastered with the dashed lines exactly one
space long.

-- 
Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos
and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss