linux-kernel - Re: [patch 0/7] tick: Optimize broadcast handling and prevent expiry ping pong

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Date:	Wed, 13 Mar 2013 15:05:16 +0530
From:	Santosh Shilimkar <santosh.shilimkar@...com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	LKML <linux-kernel@...r.kernel.org>,
	LAK <linux-arm-kernel@...ts.infradead.org>,
	John Stultz <john.stultz@...aro.org>,
	Arjan van de Veen <arjan@...radead.org>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Jason Liu <liu.h.jason@...il.com>
Subject: Re: [patch 0/7] tick: Optimize broadcast handling and prevent expiry
 ping pong

Thomas,

On Wednesday 06 March 2013 04:48 PM, Thomas Gleixner wrote:
> Jason decoded a problem related to the broadcast timer mode. The
> reprogramming of the cpu local timer causes a huge number of
> retries. Also there is a situation where the CPU which does not handle
> the broadcast timer interrupt exits and reenters broadcast mode before
> the broadcast interrupt got handled by another CPU. This can lead to
> an interesting ping pong of the broadcast and the cpu local timer
> code.
> 
> This series addresses these problems. The first two patches convert
> the broadcast code to proper cpumask_var_t instead of adding more
> bitmaps later.
> 
> The rest of the series is adopted from the quick patches which I
> posted earlier while discussing the issue with Jason et. al.
> 
> Please give it a proper testing on your affected hardware.
> 
I have tested this revised patches on OMAP4 and OMAP5 platforms
with CPUidle enabled against 3.9-rc2. As expected they seems to
work without any issue and also fixes the reported retry issue.

Tested-by: Santosh Shilimkar <santosh.shilimkar@...com>

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