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Date: Tue, 10 Dec 2013 19:05:04 -0500
From: Steven Rostedt <rostedt@goodmis.org>
To: Dave Jones <davej@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>, Oleg Nesterov <oleg@redhat.com>,
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        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>, Mel Gorman <mgorman@suse.de>
Subject: Re: process 'stuck' at exit.
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On Tue, Dec 10, 2013 at 06:00:09PM -0500, Dave Jones wrote:
> 
> The only thing I'm still unclear on, is how that pid allegedly wasn't doing
> a futex call as part of its run. The only thing I can think of is that
> the other pid that _did_ do a futex call did it on a page that was MAP_SHARED
> between all the other children, and this 'spin forever' thing only
> happens when the last process with a reference on that page exits ?

Which thread did not do the futex call? The one that was spinning? No, that one
most definitely was, at least according to the stack trace trace you posted:

 trinity-child27-10818 [001] 89790.703547: kernel_stack:         <stack trace>
=> futex_requeue (ffffffff810df18a)
=> do_futex (ffffffff810e019e)
=> SyS_futex (ffffffff810e0de1)
=> tracesys (ffffffff81760be4)  

It did a futex() system call.

Or are you talking about another thread?

-- Steve