linux-kernel - Re: [PATCH 02/18] x86/ticketlock: convert spin loop to C

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Message-ID: <m2liuid1d6.fsf@firstfloor.org>
Date:	Wed, 24 Aug 2011 13:02:29 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Nick Piggin <npiggin@...nel.dk>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Subject: Re: [PATCH 02/18] x86/ticketlock: convert spin loop to C

Jeremy Fitzhardinge <jeremy@...p.org> writes:
> +
> +	for (;;) {
> +		if (inc.tickets.head == inc.tickets.tail)
> +			goto out;

What's wrong with break ?  Similar below.

> +		cpu_relax();
> +		inc.tickets.head = ACCESS_ONCE(lock->tickets.head);
> +	}
> +out:	barrier();		/* make sure nothing creeps before the lock is taken */
>  }


-Andi
-- 
ak@...ux.intel.com -- Speaking for myself only
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