From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Ross Green" <rgkernel@gmail.com>,
linux-kernel@vger.kernel.org, mingo@kernel.org,
jiangshanlai@gmail.com, dipankar@in.ibm.com,
akpm@linux-foundation.org,
"Mathieu Desnoyers" <mathieu.desnoyers@efficios.com>,
josh@joshtriplett.org, tglx@linutronix.de, rostedt@goodmis.org,
dhowells@redhat.com, "Eric Dumazet" <edumazet@google.com>,
dvhart@linux.intel.com,
"Frédéric Weisbecker" <fweisbec@gmail.com>,
oleg@redhat.com, "pranith kumar" <bobby.prani@gmail.com>
Subject: Re: rcu_preempt self-detected stall on CPU from 4.5-rc3, since 3.17
Date: Wed, 17 Feb 2016 15:19:45 -0800 [thread overview]
Message-ID: <20160217231945.GA21140@linux.vnet.ibm.com> (raw)
In-Reply-To: <20160217202829.GO6719@linux.vnet.ibm.com>
On Wed, Feb 17, 2016 at 12:28:29PM -0800, Paul E. McKenney wrote:
> On Wed, Feb 17, 2016 at 08:45:54PM +0100, Peter Zijlstra wrote:
> > On Wed, Feb 17, 2016 at 11:28:17AM -0800, Paul E. McKenney wrote:
> > > On Tue, Feb 16, 2016 at 09:45:49PM -0800, Paul E. McKenney wrote:
> > > > On Tue, Feb 09, 2016 at 09:11:55PM +1100, Ross Green wrote:
> > > > > Continued testing with the latest linux-4.5-rc3 release.
> > > > >
> > > > > Please find attached a copy of traces from dmesg:
> > > > >
> > > > > There is a lot more debug and trace data so hopefully this will shed
> > > > > some light on what might be happening here.
> > > > >
> > > > > My testing remains run a series of simple benchmarks, let that run to
> > > > > completion and then leave the system idle away with just a few daemons
> > > > > running.
> > > > >
> > > > > the self detected stalls in this instance turned up after a days run time.
> > > > > There were NO heavy artificial computational loads on the machine.
> > > >
> > > > It does indeed look quiet on that dmesg for a good long time.
> > > >
> > > > The following insanely crude not-for-mainline hack -might- be producing
> > > > good results in my testing. It will take some time before I can claim
> > > > statistically different results. But please feel free to give it a go
> > > > in the meantime. (Thanks to Al Viro for pointing me in this direction.)
> >
> > Your case was special in that is was hotplug triggering it, right?
>
> Yes, it has thus far only shown up with CPU hotplug enabled.
>
> > I was auditing the hotplug paths involved when I fell ill two weeks ago,
> > and have not really made any progress on that because of that :/
>
> I have always said that being sick is bad for one's health, but I didn't
> realize that it could be bad for the kernel's health as well. ;-)
>
> > I'll go have another look, I had a vague feeling for a race back then,
> > lets see if I can still remember how..
>
> I believe that I can -finally- get an ftrace_dump() to happen within
> 10-20 milliseconds of the problem, which just might be soon enough
> after the problem to gather some useful information. I am currently
> testing this theory with "ftrace trace_event=sched_waking,sched_wakeup"
> boot arguments on a two-hour run.
And apparently another way to greatly reduce the probability of this
bug occurring is to enable ftrace. :-/
Will try longer runs.
Thanx, Paul
> If this works out, what would be a useful set of trace events for me
> to capture?
>
> Thanx, Paul
next prev parent reply other threads:[~2016-02-17 23:19 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-09 10:11 rcu_preempt self-detected stall on CPU from 4.5-rc3, since 3.17 Ross Green
2016-02-17 5:45 ` Paul E. McKenney
2016-02-17 19:28 ` Paul E. McKenney
2016-02-17 19:45 ` Peter Zijlstra
2016-02-17 20:28 ` Paul E. McKenney
2016-02-17 23:19 ` Paul E. McKenney [this message]
2016-02-18 11:51 ` Ross Green
2016-02-18 23:14 ` Mathieu Desnoyers
2016-02-19 3:56 ` Ross Green
2016-02-19 4:13 ` John Stultz
2016-02-19 17:33 ` Paul E. McKenney
2016-02-20 4:34 ` Ross Green
2016-02-20 6:32 ` Paul E. McKenney
2016-02-21 5:04 ` Ross Green
2016-02-21 18:15 ` Ross Green
2016-02-23 20:34 ` Mathieu Desnoyers
2016-02-23 20:55 ` Paul E. McKenney
2016-02-23 21:28 ` Ross Green
2016-02-25 5:13 ` Ross Green
2016-02-26 0:56 ` Paul E. McKenney
2016-02-26 1:35 ` Paul E. McKenney
2016-03-04 5:30 ` Ross Green
2016-03-04 15:18 ` Paul E. McKenney
2016-03-18 21:00 ` Josh Triplett
2016-03-18 23:56 ` Paul E. McKenney
2016-03-21 16:22 ` Jacob Pan
2016-03-21 17:26 ` Paul E. McKenney
2016-03-22 16:35 ` Chatre, Reinette
2016-03-22 17:40 ` Paul E. McKenney
2016-03-22 21:04 ` Chatre, Reinette
2016-03-22 21:19 ` Paul E. McKenney
2016-03-23 17:15 ` Chatre, Reinette
2016-03-23 18:20 ` Paul E. McKenney
2016-03-23 18:25 ` Chatre, Reinette
2016-03-23 19:50 ` Paul E. McKenney
2016-03-25 21:24 ` Chatre, Reinette
2016-03-25 21:46 ` Paul E. McKenney
2016-03-26 12:29 ` Mathieu Desnoyers
2016-03-26 15:28 ` Paul E. McKenney
2016-03-26 18:49 ` Paul E. McKenney
2016-03-26 22:22 ` Mathieu Desnoyers
2016-03-27 1:34 ` Paul E. McKenney
2016-03-27 13:48 ` Mathieu Desnoyers
2016-03-27 15:40 ` Paul E. McKenney
2016-03-27 20:00 ` Paul E. McKenney
2016-03-27 20:45 ` Peter Zijlstra
2016-03-27 21:06 ` Paul E. McKenney
2016-03-28 6:25 ` Peter Zijlstra
2016-03-28 13:08 ` Paul E. McKenney
2016-03-29 0:25 ` Paul E. McKenney
2016-03-29 0:28 ` Paul E. McKenney
2016-03-29 13:49 ` Paul E. McKenney
2016-03-30 14:55 ` Paul E. McKenney
2016-03-31 15:42 ` Paul E. McKenney
2016-04-03 8:18 ` Paul E. McKenney
2016-05-06 6:25 ` Ross Green
2016-05-07 15:25 ` Paul E. McKenney
2016-05-10 2:36 ` Ross Green
2016-06-30 17:52 ` Paul E. McKenney
2016-03-28 1:44 ` Mathieu Desnoyers
2016-03-28 2:23 ` Mathieu Desnoyers
2016-03-28 6:13 ` Peter Zijlstra
2016-03-28 13:50 ` Paul E. McKenney
2016-03-28 14:15 ` Mathieu Desnoyers
2016-03-27 20:53 ` Peter Zijlstra
2016-03-27 21:07 ` Paul E. McKenney
2016-03-27 20:54 ` Peter Zijlstra
2016-03-27 21:09 ` Paul E. McKenney
2016-03-28 6:28 ` Peter Zijlstra
2016-03-28 13:29 ` Paul E. McKenney
2016-03-28 15:07 ` Mathieu Desnoyers
2016-03-28 15:56 ` Paul E. McKenney
2016-03-28 16:12 ` Mathieu Desnoyers
2016-03-28 16:29 ` Paul E. McKenney
2016-03-30 12:58 ` Boqun Feng
2016-03-30 13:30 ` Paul E. McKenney
2016-03-30 14:15 ` Boqun Feng
2016-02-19 4:22 ` Paul E. McKenney
2016-02-19 5:59 ` Ross Green
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