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

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Message-ID: <20131210214143.GG27373@redhat.com>
Date:	Tue, 10 Dec 2013 16:41:43 -0500
From:	Dave Jones <davej@...hat.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Darren Hart <dvhart@...ux.intel.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Mel Gorman <mgorman@...e.de>
Subject: Re: process 'stuck' at exit.

On Tue, Dec 10, 2013 at 10:34:31PM +0100, Oleg Nesterov wrote:
 > On 12/10, Dave Jones wrote:
 > >
 > > On Tue, Dec 10, 2013 at 09:35:59PM +0100, Oleg Nesterov wrote:
 > >  >
 > >  > I am looking at the first message and I can't understand who stuck
 > >  > "at exit".
 > >  >
 > >  > The trace shows that the task with pid=10818 called sys_futex() ?
 > >  >
 > >  > Perhaps "exit" means the userspace paths?
 > >
 > > pid 1131 is wait()'ing for 10818 to exit
 > >
 > > pid 1130 is periodically sending SIGKILL to 10818 because it's gotten
 > > tired of waiting. 10818 is ignoring these because it's stuck in a loop
 > > somewhere in the kernel.
 > 
 > OK, thanks. So it doesn't return to user-space.
 > 
 > could you do
 > 
 > 	cd /sys/kernel/debug/tracing/
 > 	echo 10818 >> set_ftrace_pid
 > 	echo function_graph >> current_tracer
 > 	echo 1 >> tracing_on
 > 
 > and look into "trace" file to find out how exactly it loops?

http://codemonkey.org.uk/junk/trace

	Dave

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