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From: John Stultz <johnstul@us.ibm.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Prarit Bhargava <prarit@redhat.com>,
	Linux Kernel <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	stable@vger.kernel.org
Subject: Re: [PATCH 1/6] hrtimer: Provide clock_was_set_delayed()
Date: Wed, 11 Jul 2012 09:47:25 -0700	[thread overview]
Message-ID: <4FFDAE1D.3050008@us.ibm.com> (raw)
In-Reply-To: <alpine.LFD.2.02.1207111539060.32033@ionos>

On 07/11/2012 08:18 AM, Thomas Gleixner wrote:
> That leaves NOHZ enabled systems and there we might be clever and
> avoid the IPIs to those cores which are not idle and let the tick
> interrupt deal with it. And we can make the calls async and just let
> them raise the hrtimer softirq on those cores, which will run the
> hrtimer interrupt code and take care of everything.

I'm not familiar with the details of the code that tracks which cores 
are idle or not, but I'd worry with this approach that there might be 
further races in determining which cores are idle and which cores are 
about to go idle with stale base offsets.

I'll see if my worry is unfounded, but it might be a bit too clever for 
rare events.

thanks
-john


  parent reply	other threads:[~2012-07-11 16:48 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-07-10 22:43 [PATCH 0/6] Fix for leapsecond caused hrtimer/futex issue (updated) John Stultz
2012-07-10 22:43 ` [PATCH 1/6] hrtimer: Provide clock_was_set_delayed() John Stultz
2012-07-11 12:15   ` Prarit Bhargava
2012-07-11 12:45     ` Thomas Gleixner
2012-07-11 13:05       ` Peter Zijlstra
2012-07-11 15:18         ` Thomas Gleixner
2012-07-11 15:56           ` Peter Zijlstra
2012-07-11 16:47           ` John Stultz [this message]
2012-07-12  7:44             ` Jan Ceuleers
2012-07-12 12:29               ` Prarit Bhargava
2012-07-11 13:05       ` Prarit Bhargava
2012-07-11 13:38         ` Peter Zijlstra
2012-07-11 21:40   ` [tip:timers/urgent] " tip-bot for John Stultz
2012-07-10 22:43 ` [PATCH 2/6] timekeeping: Fix leapsecond triggered load spike issue John Stultz
2012-07-11 21:41   ` [tip:timers/urgent] " tip-bot for John Stultz
2012-07-10 22:43 ` [PATCH 3/6] timekeeping: Maintain ktime_t based offsets for hrtimers John Stultz
2012-07-11 21:42   ` [tip:timers/urgent] " tip-bot for Thomas Gleixner
2012-07-10 22:43 ` [PATCH 4/6] hrtimer: Move lock held region in hrtimer_interrupt() John Stultz
2012-07-10 22:43 ` [PATCH 4/6] hrtimers: " John Stultz
2012-07-11 21:43   ` [tip:timers/urgent] " tip-bot for Thomas Gleixner
2012-07-10 22:43 ` [PATCH 5/6] timekeeping: Provide hrtimer update function John Stultz
2012-07-11 21:44   ` [tip:timers/urgent] " tip-bot for Thomas Gleixner
2012-07-10 22:43 ` [PATCH 6/6] hrtimer: Update hrtimer base offsets each hrtimer_interrupt John Stultz
2012-07-11 21:45   ` [tip:timers/urgent] " tip-bot for John Stultz
2012-07-15 15:22   ` [PATCH 6/6] " Andreas Schwab
2012-07-15 15:22     ` Andreas Schwab
2012-07-15 20:28     ` Rafael J. Wysocki
2012-07-15 20:28       ` Rafael J. Wysocki
     [not found]   ` <m2y5mlnj5z.fsf__49536.0585897744$1342365803$gmane$org@igel.home>
2012-07-15 16:02     ` Andreas Schwab
2012-07-10 22:53 ` [PATCH 0/6] Fix for leapsecond caused hrtimer/futex issue (updated) John Stultz
2012-07-12 22:43   ` Jiri Bohac
2012-07-12 23:58     ` John Stultz
2012-07-10 23:00 ` John Stultz
2012-07-13  0:43   ` John Stultz
2012-07-11 10:59 ` Peter Zijlstra
2012-07-11 11:17 ` Ingo Molnar
2012-07-12 12:32   ` Prarit Bhargava
2012-07-11 12:16 ` Prarit Bhargava

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