From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Sasha Levin <sasha.levin@oracle.com>,
LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: timers: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected
Date: Fri, 15 Jan 2016 13:11:25 -0800 [thread overview]
Message-ID: <20160115211125.GA3818@linux.vnet.ibm.com> (raw)
In-Reply-To: <alpine.DEB.2.11.1601151102320.3575@nanos>
On Fri, Jan 15, 2016 at 11:03:24AM +0100, Thomas Gleixner wrote:
> On Thu, 14 Jan 2016, Paul E. McKenney wrote:
> > > Untested patch below.
> >
> > One small fix to make it build below. Started rcutorture, somewhat
> > pointlessly given that the splat doesn't appear on my setup.
>
> Well, at least it tells us whether the change explodes by itself.
Hmmm...
So this is a strange one. I have been seeing increasing instability
in mainline over the past couple of releases, with the main symptom
being that the kernel decides that awakening RCU's grace-period kthreads
is an optional activity. The usual situation is that the kthread is
blocked for tens of seconds in an wait_event_interruptible_timeout(),
despite having a three-jiffy timeout. Doing periodic wakeups from
the scheduling-clock interrupt seems to clear things up, but such hacks
should not be necessary.
Normally, I have to run for for some hours to have a good chance of seeing
this happen. This change triggered in a 30-minute run. Not only that,
but in a .config scenario that is normally very hard to trigger. This
scenario does involve CPU hotplug, and I am re-running with CPU hotplug
disabled.
That said, I am starting to hear reports of people hitting this without
CPU hotplug operations...
Thanx, Paul
next prev parent reply other threads:[~2016-01-15 21:18 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-12 20:03 timers: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected Sasha Levin
2016-01-12 20:18 ` Peter Zijlstra
2016-01-12 20:52 ` Paul E. McKenney
2016-01-13 9:05 ` Thomas Gleixner
2016-01-13 16:16 ` Paul E. McKenney
2016-01-14 17:43 ` Thomas Gleixner
2016-01-14 18:18 ` Paul E. McKenney
2016-01-14 19:47 ` Thomas Gleixner
2016-01-15 1:42 ` Paul E. McKenney
2016-01-15 10:03 ` Thomas Gleixner
2016-01-15 21:11 ` Paul E. McKenney [this message]
2016-01-15 22:10 ` Paul E. McKenney
2016-01-15 23:14 ` Paul E. McKenney
2016-01-29 15:27 ` Peter Zijlstra
2016-01-31 0:28 ` Paul E. McKenney
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20160115211125.GA3818@linux.vnet.ibm.com \
--to=paulmck@linux.vnet.ibm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=peterz@infradead.org \
--cc=sasha.levin@oracle.com \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox