linux-kernel - Re: [PATCH -v2] x86: enable preemption in delay

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Message-ID: <Pine.LNX.4.58.0805250943010.22651@gandalf.stny.rr.com>
Date:	Sun, 25 May 2008 09:44:36 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Thomas Gleixner <tglx@...utronix.de>
cc:	LKML <linux-kernel@...r.kernel.org>,
	linux-rt-users <linux-rt-users@...r.kernel.org>, akpm@...l.org,
	Ingo Molnar <mingo@...e.hu>,
	Clark Williams <clark.williams@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"Luis Claudio R. Goncalves" <lclaudio@...g.org>,
	Gregory Haskins <ghaskins@...ell.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi-suse@...stfloor.org>
Subject: Re: [PATCH -v2] x86: enable preemption in delay


On Sun, 25 May 2008, Steven Rostedt wrote:

> +
> +		/*
> +		 * It is possible that we moved to another CPU, and
> +		 * since TSC's are per-cpu we need to calculate
> +		 * that. The delay must guarantee that we wait "at
> +		 * least" the amount of time. Being moved to another
> +		 * CPU could make the wait longer but we just need to
> +		 * make sure we waited long enough. Rebalance the
> +		 * counter for this CPU.
> +		 */
> +		if (unlikely(cpu != smp_processor_id())) {
> +			cpu = smp_processor_id();
> +			rdtscl(bclock);
> +		}
>  	}
>  	while ((now-bclock) < loops);

BAH! expect version 3. :-p

This was compiled tested.

-- Steve

>  	preempt_enable();
>
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