From mboxrd@z Thu Jan  1 00:00:00 1970
From: Russell King - ARM Linux <linux@arm.linux.org.uk>
Subject: Re: [PATCH v4 02/17] sched_clock: Use seqcount instead of rolling
	our own
Date: Fri, 19 Jul 2013 15:27:18 +0100
Message-ID: <20130719142718.GG24642@n2100.arm.linux.org.uk>
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To: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Will Deacon <will.deacon@arm.com>, Stephen Boyd <sboyd@codeaurora.org>, John Stultz <john.stultz@linaro.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "linux-arm-msm@vger.kernel.org" <linux-arm-msm@vger.kernel.org>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>, Thomas Gleixner <tglx@linutronix.de>, Catalin Marinas <Catalin.Marinas@arm.com>, Christopher Covington <cov@codeaurora.org>
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On Fri, Jul 19, 2013 at 10:20:19AM -0400, Nicolas Pitre wrote:
> On Fri, 19 Jul 2013, Will Deacon wrote:
> 
> > Looks good to me. The current scheme would be very fiddly to extend to
> > 64-bit values on 32-bit architectures without cheap atomic doubleword
> > accesses.
> 
> You should have a look at include/linux/cnt32_to_63.h.
> This could be applied to pure software counters if the low part is 
> atomically increased.

But this can't be used for sched_clock().  That's exactly why I originally
had to rewrite that thing in the first place.