netdev - Re: [PATCH net V4 2/2] igb: offer a PTP Hardware Clock instead of the timecompare method

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Date:	Wed, 21 Mar 2012 18:00:03 +0100
From:	Richard Cochran <richardcochran@...il.com>
To:	chetan loke <loke.chetan@...il.com>
Cc:	netdev@...r.kernel.org, e1000-devel@...ts.sourceforge.net,
	jacob.e.keller@...el.com, jeffrey.t.kirsher@...el.com,
	john.ronciak@...el.com, john.stultz@...aro.org, tglx@...utronix.de
Subject: Re: [PATCH net V4 2/2] igb: offer a PTP Hardware Clock instead of
 the timecompare method

On Wed, Mar 21, 2012 at 11:00:59AM -0400, chetan loke wrote:
> Once PHC->gettime goes live(aka exported to user space), we can't
> really control how users will use it in their applications. There
> could be 100+ apps all trying to get real-time from the network to do
> some time-keeping stuff. They might pound the ioctls at high rate. The
> last thing we would want is to self-induce a light weight DOS. What
> Eric Dumazet mentioned in the very first patch set seems like a good
> comment. seqlock or whatever it is we use for jiffies.

Can you please explain how using a seqlock could help here?

Thanks,
Richard
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