linux-kernel - Re: process 'stuck' at exit.

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Message-ID: <1386710734.3685.85.camel@dvhart-mobl4.amr.corp.intel.com>
Date:	Tue, 10 Dec 2013 13:25:34 -0800
From:	Darren Hart <dvhart@...ux.intel.com>
To:	Dave Jones <davej@...hat.com>, Steven Rostedt <rostedt@...dmis.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Mel Gorman <mgorman@...e.de>, Oleg Nesterov <oleg@...hat.com>
Subject: Re: process 'stuck' at exit.

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



-- 
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel


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