Re: process 'stuck' at exit.

[Thomas Gleixner]

On Tue, 10 Dec 2013, Darren Hart wrote:
> On Tue, 2013-12-10 at 15:55 -0500, Dave Jones wrote:
> > On Tue, Dec 10, 2013 at 09:34:24PM +0100, Thomas Gleixner wrote:
> >  
> >  > >  > PS: Oleg - the whole thread is on lkml. Ping me if you need more context.
> >  > > 
> >  > > btw, I've left the machine in that state, and will for as long as necesary
> >  > > in case someone has any ideas for further tracing experiments.
> >  > 
> >  > Can you gather a trace with the function tracer? That will tell us
> >  > what the thing is actually doing.
> > 
> > Feed me command lines, and I'll see what I can do.
> > 
> > 	Dave
> > 
> 
> So let's see if we can determine the call chain inside futex_requeue, if
> there is one. We want to see if we are calling the following functions:
> 
> futex.c: free_pi_state
> futex.c: get_futex_value_locked
> futex.c: futex_proxy_trylock_atomic
> futex.c: lookup_pi_state
> futex.c: fault_in_user_writeable
> 
> I'm hoping we can make use of ftrace here?
> 
> Consider:
> 
> $ trace-cmd record -P <PID> -p function -l '*futex*'
> 
> And to try outside of futex:
> 
> $ trace-cmd record -P <PID> -p function
> 
> Then ^C after a few seconds. The trace will be in trace.dat

We definitely want the latter. The futex code gets compiled into some
badly traceable mess.

Thanks,

	tglx
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