linux-kernel - [GIT PULL] nohz: Fix double clock write on idle ticks

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Date:	Fri, 22 Aug 2014 19:09:31 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
Subject: [GIT PULL] nohz: Fix double clock write on idle ticks

From: Frederic Weisbecker <fweisbec@...il.com>

Ingo,

Please pull the nohz/drop-double-write-v3 branch that can be found at:

git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
	nohz/drop-double-write-v3

Although the 1st patch fixes a bug, it was a longstanding issue so
that branch doesn't need to be applied in 3.17. The next merge window
looks better.

--
The tick reschedules itself unconditionally. It's relevant in periodic
mode but not in dynticks mode where it results in spurious double clock
writes and even spurious periodic behaviour for low-res case.

This set fixes that:

* 1st patch removes low-res periodic tick rescheduling in nohz mode.
This fixes spurious periodic behaviour.

* 2nd patch does the same for high-res mode. Here there is no such
spurious periodic behaviour but it still spares a double clock write
in some cases.
---


Thanks,
	Frederic
---

Viresh Kumar (2):
      nohz: Fix spurious periodic tick behaviour in low-res dynticks mode
      nohz: Avoid tick's double reprogramming in highres mode


 kernel/time/tick-sched.c | 8 ++++++++
 1 file changed, 8 insertions(+)
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