On Fri, 2010-04-16 at 16:04 +0200, Jan Kiszka wrote:
> Philippe Gerum wrote:
> > On Fri, 2010-04-16 at 14:31 +0200, Jan Kiszka wrote:
> >> Gilles Chanteperdrix wrote:
> >>> GIT version control wrote:
> >>>> Module: xenomai-jki
> >>>> Branch: for-upstream
> >>>> Commit: 55ebde80258b5b6c3d29d37b5f30a3199faf0881
> >>>> URL:    
> >>>> http://git.xenomai.org/?p=xenomai-jki.git;a=commit;h=55ebde80258b5b6c3d29d37b5f30a3199faf0881
> >>>>
> >>>> Author: Wolfgang Mauerer <wolfgang.maue...@siemens.com>
> >>>> Date:   Tue Mar 30 11:13:33 2010 +0200
> >>>>
> >>>> RTDM: Fix potential NULL pointer dereference
> >>>>
> >>>> The rework in 95278926edc559d4 misses the case that context can be NULL,
> >>>> which can (and has) triggered a kernel oops. Take care of this case.
> >>>>
> >>>> Signed-off-by: Wolfgang Mauerer <wolfgang.maue...@siemens.com>
> >>>> Signed-off-by: Jan Kiszka <jan.kis...@siemens.com>
> >>> I still think that fix is a useles waste of time. Let us merge
> >>> Philippe's patches instead.
> >> Please accept that Philippe's patch is orthogonal to this bug.
> >>
> >> And it didn't work as-is. I'll post a rework which has the same benefit
> >> (avoiding to poll on pending context references) - once it is tested.
> > 
> > You mean that your current implementation, does poll, right? Because
> > mine does not, that was the point of it, also to solve races in
> > cross-context management IIRC.
> 
> Polling is part of the RTDM API: If a driver requests it via EAGAIN, we
> have to provide it. We may deprecate this feature long-term, but for now
> there are no drop-in replacements available and we have drivers in the
> field that make use of it.

Well, you likely know my feeling about this. Being bug-compatible
induces more issues than it solves in the long run. As a frequent RTDM
user myself, I must admit that the close issue has been a real PITA over
time, and I guess a lot more people are suffering in silence. So
anything to solve it properly, I mean following the POLA, would be
warmly welcomed. POSIX is sometimes silly, but follows POLA for sure.

> 
> > That patch dates back to the 2.5 -rc
> > cycle, when I needed it to have a decent behavior while working on the
> > RTIPC stuff. It should not be that difficult to forward port it to
> > -head, I guess. Let me know if I can help.
> 
> Thanks. The patch is done, it just waits for the final tests as I wrote.
> I would be happy if you could test it as well if you have something that
> nicely stresses e.g. RTIPC in this domain.
> 

Ok, I can do that. Let me know when I can try things.

> Jan
> 


-- 
Philippe.



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