All of lore.kernel.org
 help / color / mirror / Atom feed
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Don Zickus <dzickus@redhat.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Ingo Molnar <mingo@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Li Zhong <zhong@linux.vnet.ibm.com>
Subject: Re: [PATCH 3/8] watchdog: Boot-disable by default on full dynticks
Date: Mon, 20 May 2013 20:14:26 +0200	[thread overview]
Message-ID: <20130520181424.GA22846@somewhere> (raw)
In-Reply-To: <20130520175229.GI133453@redhat.com>

On Mon, May 20, 2013 at 01:52:29PM -0400, Don Zickus wrote:
> On Mon, May 20, 2013 at 06:01:51PM +0200, Frederic Weisbecker wrote:
> > When the watchdog runs, it prevents the full dynticks
> > CPUs from stopping their tick because the hard lockup
> > detector uses perf events internally, which in turn
> > rely on the periodic tick.
> > 
> > Since this is a rather confusing behaviour that is not
> > easy to track down and identify for those who want to
> > test CONFIG_NO_HZ_FULL, let's default disable the
> > watchdog on boot time when full dynticks is enabled.
> > 
> > The user can still enable it later on runtime using
> > proc or sysctl.
> 
> I thought Peter committed a patch to perf so that this isn't needed any
> more?

There is the patchset that converts perf_event_task_tick() to an hrtimer.
But I'm not sure it covers everything. Also this will be for the next merge
window. And in the end this moves the problem elsewhere: we still have timer
interrupts, they just come as specific hrtimers, although may be less often,
I haven't looked yet at the patchset.

  reply	other threads:[~2013-05-20 18:14 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-05-20 16:01 [PATCH 0/8] nohz: Random fixes Frederic Weisbecker
2013-05-20 16:01 ` [PATCH 1/8] nohz: Warn if the machine can not perform nohz_full Frederic Weisbecker
2013-05-20 16:01 ` [PATCH 2/8] vtime: Use consistent clocks among nohz accounting Frederic Weisbecker
2013-06-03  9:47   ` Stefan Seyfried
2013-06-03 13:48     ` Steven Rostedt
2013-06-03 19:48     ` Frederic Weisbecker
2013-06-03 19:51       ` Stefan Seyfried
2013-06-03 20:12         ` Frederic Weisbecker
2013-05-20 16:01 ` [PATCH 3/8] watchdog: Boot-disable by default on full dynticks Frederic Weisbecker
2013-05-20 17:52   ` Don Zickus
2013-05-20 18:14     ` Frederic Weisbecker [this message]
2013-05-20 16:01 ` [PATCH 4/8] kvm: Move guest entry/exit APIs to context_tracking Frederic Weisbecker
2013-05-20 16:01 ` [PATCH 5/8] nohz: Fix notifier return val that enforce timekeeping Frederic Weisbecker
2013-05-20 16:01 ` [RFC PATCH 6/8] kthread: Enable parking requests from setup() and unpark() callbacks Frederic Weisbecker
2013-05-21  5:34   ` anish singh
2013-05-21  7:49     ` Srivatsa S. Bhat
2013-05-21  8:58       ` anish singh
2013-05-21  9:07         ` Srivatsa S. Bhat
2013-05-22 15:18         ` Frederic Weisbecker
2013-05-21  6:59   ` Srivatsa S. Bhat
2013-06-05 16:33     ` Frederic Weisbecker
2013-05-20 16:01 ` [RFC PATCH 7/8] watchdog: Rename confusing state variable Frederic Weisbecker
2013-05-20 17:53   ` Don Zickus
2013-05-20 16:01 ` [RFC PATCH 8/8] watchdog: Fix internal state with boot user disabled watchdog Frederic Weisbecker
2013-05-20 17:54   ` Don Zickus

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=20130520181424.GA22846@somewhere \
    --to=fweisbec@gmail.com \
    --cc=akpm@linux-foundation.org \
    --cc=dzickus@redhat.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@kernel.org \
    --cc=paulmck@linux.vnet.ibm.com \
    --cc=peterz@infradead.org \
    --cc=rostedt@goodmis.org \
    --cc=tglx@linutronix.de \
    --cc=zhong@linux.vnet.ibm.com \
    /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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.