Re: [Xenomai-core] [PATCH] provide rtdm_mmap_to_user / rtdm_munmap

[Rodrigo Rosenfeld Rosas <lbocseg@domain.hid>]

Jan Kiszka escreveu:

>Rodrigo Rosenfeld Rosas wrote:
>  
>
>>Jan Kiszka escreveu:
>>    
>>
>>>Ok, but even if you decide to let rt-mmap be non-deterministic, you
>>>still need some means to prevent the scenario you described above.
>>>Actually, all you need is some callback when the mapped memory block was
>>>actually released (munmap/application exit). Such a callback can be
>>>registered inside the rtdm_mmap handler as a vma_fileop.
>>>      
>>>
>>I have never worked with vma_fileop... I would need to learn it first.
>>    
>>
>
>Here is the patch to offer you access to those ops. Revert the previous
>version, then apply this one.
>
Actually I would have to revert the modifications I had to do for the 
patch to apply (some rejected chunks). But I think I'll update to the 
last SVN xenomai. BTW, is this patch for the SVN or 2.1 or 2.0.2 
xenomai? Or it would apply for all of them?

> It still needs some final documentation
>notes and a test on kernel 2.4. But is should already work on 2.6.
>  
>
I forgot to mention, I have one more problem. Since I call mmap on 
driver initialization (thus before any rtdm_dev_open), I do not have any 
rtdm_user_info_t, so I need to use current instead, but I'm not sure if 
this will work. Maybe mmap needs the 'current' struct of the user 
program... I don't know this very well... If that is true, so I'll have 
to do the maps in a non-rt context anyway...

>I also attached a demo for the handler usage based on my previous test
>framework. Just grab the pattern and put some useful code in the close
>handler...
>
>  
>
>>> It will run in
>>>non-RT, and could be used to mark the related hardware buffer as finally
>>>free for re-allocation.
>>>      
>>>
>>Now, I did realize that there is one more problem on my current design.
>>If the user application exits or is terminated, I'm not sure if the
>>close handler is called if the user forgot/was not able to. If it is
>>not, the buffer would be marked as used until I reloaded the driver...
>>Is the close handler invocated on application termination?
>>    
>>
>
>Yep, this is a general issue you cannot avoid: all skin objects besides
>task are only released when the user-space application cleans it up as
>it's ought to. There is no tracking of used resources, no auto-cleanup.
>If your application fails to close a device or socket, you will get a
>stalled handle which can be found in /proc/xenomai/rtdm/open_files.
>Writing the file descriptor number to this particular proc-file (e.g.
>"echo 3 > /proc/xeno...") will trigger an enforced close and will
>release the file descriptor again. Useful when debugging such broken
>applications.
>  
>
Yes, sorry... I forgot I've already read this... :)

Rodrigo.


	

	
		
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