[uml-devel] Re: [uml-user] Host processes never terminate on 2.6.9rc3 host (stuck in ptrace_stop)

[BlaisorBlade <blaisorblade_spam@yahoo.it>]

On Monday 18 October 2004 23:26, Gerd Knorr wrote:
> > > Yes, I see that as well, it actually *is* that ptrace change added in
> > > patch-2.6.9-rc1-bk16.
> > >
> > > IMHO it is a bug, I've reported it to lkml a
> > > few days ago, no response yet.
> >
> > Oh well, did I lost it or you did not CC the UML mailing list? And in the
> > 2nd case, why?

> I didn't cc the uml list as it isn't a uml bug, its just that uml
> triggeres it.
Hmm - trying to fix that or just reverting the patch inside the SKAS patch (or 
as attached patch) would have been a possible workaround.
> > I'm downloading the patches from BitKeeper.
>
> I'll attach the offending one for reference, also a short test app
> showing the buggy behavior.

> > > Problem is that you can't kill -9 processes any more which are ptraced
> > > _and_ stopped at the same time.
> >
> > Sorry, tried kill -CONT? I'm almost sure it works (tried by both Henrik
> > Normstrod and me, not in this case).

> IMHO it is a clear bug in the (host) kernel, so I didn't attempt yet to
> workaround that by playing tricks in the UML kernel.  I can't see the
> bug when reading the patch through, probably the separation of stopped
> and traced process states triggeres some odd corner case somewhere else
> in the kernel ...
>
> If you send a SIGKILL to the process being stopped & ptraced *nothing*
> happens.  Neither the process is killed nor the ptracing parent is
> notified.  That can't be correct.

Can you try using SIGCONT, please? Even the patch changelog clearly says that 
you must kill -CONT before kill -KILL (actually, a kill -CONT may make the 
process notice the SIGKILL), and that behaviour can be reproduced, I think, 
on every kernel version. There has been a thread on this (t-mode processes) 
on uml-devel. Quite frankly, I do not know the question myself - but people 
seem to agree that this is a correct behaviour.

That said, I'll give a look to the patch. Have you CC'ed the patch author on 
your report?
-- 
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729


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