linux-kernel - Re: [PATCH 15/16] time: Update tiemkeeper structure using a local shadow

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Message-ID: <1321567402.25715.35.camel@work-vm>
Date:	Thu, 17 Nov 2011 14:03:22 -0800
From:	John Stultz <john.stultz@...aro.org>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Richard Cochran <richardcochran@...il.com>
Subject: Re: [PATCH 15/16] time: Update tiemkeeper structure using a local
 shadow

On Mon, 2011-11-14 at 20:04 -0800, John Stultz wrote:
> Uses a local shadow structure to update the timekeeper. This
> reduces the timekeeper.lock hold time.
> 
> WARNING: This introduces a race, but the window might be provably
> so small as to not be observable. This patch needs lots more math
> and comments to validate that assumption.

Bah. After thinking about it, this patch won't work, since it would
possibly lose updates via settimeofday(), etc.

So I'm coming around to Thomas' double lock reader-seq/writer-lock
method.

thanks
-john

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