linux-kernel - Re: [RFC patch 0/4] TSC calibration improvements

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Message-ID: <alpine.LFD.1.10.0809061406150.3117@nehalem.linux-foundation.org>
Date:	Sat, 6 Sep 2008 14:10:32 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Thomas Gleixner <tglx@...utronix.de>
cc:	Alok Kataria <akataria@...are.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	LKML <linux-kernel@...r.kernel.org>,
	Arjan van de Veen <arjan@...radead.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Dan Hecht <dhecht@...are.com>,
	Garrett Smith <garrett@...are.com>
Subject: Re: [RFC patch 0/4] TSC calibration improvements



On Sat, 6 Sep 2008, Thomas Gleixner wrote:
>  
> Where is a guarantee, that excpect is not decremented before we break
> out of the loop ? 

Quite the reverse. We have a guarantee that it _is_ decremented.

Adn that guarantee is very much about the C language.

		for (a ; b ; c) {
			..
		}

translates as

		a;
		while (b) {
			..
	continue:
			c;
		}

And this has absolutely _nothing_ to do with any gcc oddity or anything 
else. 

The fact is, the code that Ingo added was totally bogus. The real bug was 
that he did a totally bogus "--expect" in the argument to that last call. 

Because 'c' *will* have been done after the last iteration of the loop.

			Linus
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