From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Tony Lindgren <tony@atomide.com>, Paul Walmsley <paul@pwsan.com>,
"Bruce, Becky" <bbruce@ti.com>,
"Paul E. McKenney" <paul.mckenney@linaro.org>,
"<linux-kernel@vger.kernel.org>" <linux-kernel@vger.kernel.org>,
"<linux-omap@vger.kernel.org>" <linux-omap@vger.kernel.org>,
"<linux-arm-kernel@lists.infradead.org>"
<linux-arm-kernel@lists.infradead.org>,
"Hilman, Kevin" <khilman@ti.com>,
"Shilimkar, Santosh" <santosh.shilimkar@ti.com>,
"Hunter, Jon" <jon-hunter@ti.com>,
"<snijsure@grid-net.com>" <snijsure@grid-net.com>
Subject: Re: rcu self-detected stall messages on OMAP3, 4 boards
Date: Sat, 22 Sep 2012 09:00:31 -0700 [thread overview]
Message-ID: <20120922160031.GC2934@linux.vnet.ibm.com> (raw)
In-Reply-To: <CAFTL4hy5wO9CL5_1e8U7L3Tihm_HYD6uAsda3ue-zDKFjir2Xg@mail.gmail.com>
On Sat, Sep 22, 2012 at 05:45:12PM +0200, Frederic Weisbecker wrote:
> 2012/9/22 Paul E. McKenney <paulmck@linux.vnet.ibm.com>:
> > On Fri, Sep 21, 2012 at 01:31:49PM -0700, Tony Lindgren wrote:
> >> * Paul E. McKenney <paulmck@linux.vnet.ibm.com> [120921 12:58]:
> >> >
> >> > Just to make sure I understand the combinations:
> >> >
> >> > o All stalls have happened when running a minimal userspace.
> >> > o CONFIG_NO_HZ=n suppresses the stalls.
> >> > o CONFIG_RCU_FAST_NO_HZ (which depends on CONFIG_NO_HZ=y) has
> >> > no observable effect on the stalls.
> >>
> >> The reason why you may need minimal userspace is to cut down
> >> the number of timers waking up the system with NO_HZ.
> >> Booting with init=/bin/sh might also do the trick for that.
> >
> > Good point! This does make for a very quiet system, but does not
> > reproduce the problem under kvm, even after waiting for four minutes.
> > I will leave it for more time, but it looks like I really might need to
> > ask Linaro for remote access to a Panda.
>
> I have one. I'm currently installing Ubuntu on it and I'll try to
> manage to build
> a kernel and reproduce the issue.
>
> I'll give more news soon.
Thank you!
My bet is that you have to have a userspace that is so small that it
registers only a few (but at least one!) RCU callback at boot time,
then never registers any callbacks ever again. I have coded up a
crude test case, using Tony Lindgren's suggestion of "init=/bin/sh",
but I appear to have inadvertently fixed this bug in current -rcu
(git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git,
branch rcu/next).
But I have been wrong a few times already on this particular bug...
Thanx, Paul
WARNING: multiple messages have this Message-ID (diff)
From: paulmck@linux.vnet.ibm.com (Paul E. McKenney)
To: linux-arm-kernel@lists.infradead.org
Subject: rcu self-detected stall messages on OMAP3, 4 boards
Date: Sat, 22 Sep 2012 09:00:31 -0700 [thread overview]
Message-ID: <20120922160031.GC2934@linux.vnet.ibm.com> (raw)
In-Reply-To: <CAFTL4hy5wO9CL5_1e8U7L3Tihm_HYD6uAsda3ue-zDKFjir2Xg@mail.gmail.com>
On Sat, Sep 22, 2012 at 05:45:12PM +0200, Frederic Weisbecker wrote:
> 2012/9/22 Paul E. McKenney <paulmck@linux.vnet.ibm.com>:
> > On Fri, Sep 21, 2012 at 01:31:49PM -0700, Tony Lindgren wrote:
> >> * Paul E. McKenney <paulmck@linux.vnet.ibm.com> [120921 12:58]:
> >> >
> >> > Just to make sure I understand the combinations:
> >> >
> >> > o All stalls have happened when running a minimal userspace.
> >> > o CONFIG_NO_HZ=n suppresses the stalls.
> >> > o CONFIG_RCU_FAST_NO_HZ (which depends on CONFIG_NO_HZ=y) has
> >> > no observable effect on the stalls.
> >>
> >> The reason why you may need minimal userspace is to cut down
> >> the number of timers waking up the system with NO_HZ.
> >> Booting with init=/bin/sh might also do the trick for that.
> >
> > Good point! This does make for a very quiet system, but does not
> > reproduce the problem under kvm, even after waiting for four minutes.
> > I will leave it for more time, but it looks like I really might need to
> > ask Linaro for remote access to a Panda.
>
> I have one. I'm currently installing Ubuntu on it and I'll try to
> manage to build
> a kernel and reproduce the issue.
>
> I'll give more news soon.
Thank you!
My bet is that you have to have a userspace that is so small that it
registers only a few (but at least one!) RCU callback at boot time,
then never registers any callbacks ever again. I have coded up a
crude test case, using Tony Lindgren's suggestion of "init=/bin/sh",
but I appear to have inadvertently fixed this bug in current -rcu
(git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git,
branch rcu/next).
But I have been wrong a few times already on this particular bug...
Thanx, Paul
next prev parent reply other threads:[~2012-09-22 16:00 UTC|newest]
Thread overview: 101+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-12 22:51 rcu self-detected stall messages on OMAP3, 4 boards Paul Walmsley
2012-09-12 22:51 ` Paul Walmsley
2012-09-13 1:12 ` Paul E. McKenney
2012-09-13 1:12 ` Paul E. McKenney
2012-09-13 18:52 ` Paul Walmsley
2012-09-13 18:52 ` Paul Walmsley
2012-09-20 0:03 ` Paul E. McKenney
2012-09-20 0:03 ` Paul E. McKenney
2012-09-20 0:03 ` Paul E. McKenney
2012-09-20 7:56 ` Paul Walmsley
2012-09-20 7:56 ` Paul Walmsley
2012-09-20 15:03 ` Bruce, Becky
2012-09-20 15:03 ` Bruce, Becky
2012-09-20 21:49 ` Bruce, Becky
2012-09-20 21:49 ` Bruce, Becky
2012-09-20 22:01 ` Paul E. McKenney
2012-09-20 22:01 ` Paul E. McKenney
2012-09-20 22:01 ` Paul E. McKenney
2012-09-20 22:47 ` Paul Walmsley
2012-09-20 22:47 ` Paul Walmsley
2012-09-20 23:21 ` Paul E. McKenney
2012-09-20 23:21 ` Paul E. McKenney
2012-09-20 23:21 ` Paul E. McKenney
2012-09-21 18:08 ` Paul Walmsley
2012-09-21 18:08 ` Paul Walmsley
2012-09-21 18:58 ` Paul E. McKenney
2012-09-21 18:58 ` Paul E. McKenney
2012-09-21 19:11 ` Paul Walmsley
2012-09-21 19:11 ` Paul Walmsley
2012-09-21 19:57 ` Paul E. McKenney
2012-09-21 19:57 ` Paul E. McKenney
2012-09-21 20:31 ` Tony Lindgren
2012-09-21 20:31 ` Tony Lindgren
2012-09-21 22:03 ` Paul E. McKenney
2012-09-21 22:03 ` Paul E. McKenney
2012-09-22 15:45 ` Frederic Weisbecker
2012-09-22 15:45 ` Frederic Weisbecker
2012-09-22 16:00 ` Paul E. McKenney [this message]
2012-09-22 16:00 ` Paul E. McKenney
2012-09-21 22:12 ` Paul E. McKenney
2012-09-21 22:12 ` Paul E. McKenney
2012-09-22 18:42 ` Paul Walmsley
2012-09-22 18:42 ` Paul Walmsley
2012-09-22 20:10 ` Paul E. McKenney
2012-09-22 20:10 ` Paul E. McKenney
2012-09-22 21:59 ` Paul E. McKenney
2012-09-22 21:59 ` Paul E. McKenney
2012-09-22 22:25 ` Paul Walmsley
2012-09-22 22:25 ` Paul Walmsley
2012-09-22 23:11 ` Paul E. McKenney
2012-09-22 23:11 ` Paul E. McKenney
2012-09-22 23:11 ` Paul E. McKenney
2012-09-23 7:55 ` Paul Walmsley
2012-09-23 7:55 ` Paul Walmsley
2012-09-23 7:55 ` Paul Walmsley
2012-09-23 12:11 ` Paul E. McKenney
2012-09-23 12:11 ` Paul E. McKenney
2012-09-23 12:11 ` Paul E. McKenney
2012-09-23 1:42 ` Paul Walmsley
2012-09-23 1:42 ` Paul Walmsley
2012-09-23 1:56 ` Paul E. McKenney
2012-09-23 1:56 ` Paul E. McKenney
2012-09-23 1:56 ` Paul E. McKenney
2012-09-23 2:01 ` Paul Walmsley
2012-09-23 2:01 ` Paul Walmsley
2012-09-24 9:41 ` Shilimkar, Santosh
2012-09-24 9:41 ` Shilimkar, Santosh
2012-09-24 13:18 ` Paul E. McKenney
2012-09-24 13:18 ` Paul E. McKenney
2012-10-01 8:55 ` Linus Walleij
2012-10-01 8:55 ` Linus Walleij
2012-10-01 13:28 ` Paul E. McKenney
2012-10-01 13:28 ` Paul E. McKenney
2012-09-21 18:59 ` Paul Walmsley
2012-09-21 18:59 ` Paul Walmsley
2012-09-21 17:47 ` Paul Walmsley
2012-09-21 17:47 ` Paul Walmsley
2012-09-21 17:51 ` Paul Walmsley
2012-09-21 17:51 ` Paul Walmsley
2012-09-21 21:20 ` Paul E. McKenney
2012-09-21 21:20 ` Paul E. McKenney
2012-09-21 21:20 ` Paul E. McKenney
2012-09-21 22:41 ` Paul Walmsley
2012-09-21 22:41 ` Paul Walmsley
2012-09-22 0:05 ` Paul E. McKenney
2012-09-22 0:05 ` Paul E. McKenney
2012-09-22 18:16 ` Paul Walmsley
2012-09-22 18:16 ` Paul Walmsley
2012-09-22 18:16 ` Paul Walmsley
2012-09-22 19:52 ` Paul E. McKenney
2012-09-22 19:52 ` Paul E. McKenney
2012-09-22 19:52 ` Paul E. McKenney
2012-09-22 22:20 ` Paul Walmsley
2012-09-22 22:20 ` Paul Walmsley
2012-09-22 22:20 ` Paul Walmsley
2012-09-22 23:17 ` Paul E. McKenney
2012-09-22 23:17 ` Paul E. McKenney
2012-09-24 21:54 ` Paul Walmsley
2012-09-24 21:54 ` Paul Walmsley
2012-09-24 22:00 ` Paul E. McKenney
2012-09-24 22:00 ` Paul E. McKenney
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