linux-kernel - Re: [PATCH] /dev/random: Insufficient of entropy on many architectures

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Message-ID: <20130910203853.GG29237@thunk.org>
Date:	Tue, 10 Sep 2013 16:38:53 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	John Stultz <john.stultz@...aro.org>
Cc:	Stephan Mueller <smueller@...onox.de>,
	LKML <linux-kernel@...r.kernel.org>, dave.taht@...ferbloat.net
Subject: Re: [PATCH] /dev/random: Insufficient of entropy on many
 architectures

On Tue, Sep 10, 2013 at 12:38:56PM -0700, John Stultz wrote:
> So the end of timekeeping_init() may not be what you want here. This
> only means we've started up the timekeping core with only the default
> clocksource (with only few exceptions, this is almost always jiffies).
> Then as clocksource drivers are initialized, they are registered and
> the timekeeping core will switch over to the best available
> clocksource.  Also, to avoid the churn at boot of switching to every
> clocksource registered, we queue them up and wait until fs_init time
> to switch to whatever is the best available then.

Is there any indication in the clocksource structures where we can
determine what the cost (in CPU, time, bus overhead, etc.) for a
particular clock source, verus the granularity of the clock source?

Also, is it always safe to read from a clock source from an interrupt
handler?

Thanks,

					- Ted
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