Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760057AbXHXMAb (ORCPT ); Fri, 24 Aug 2007 08:00:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754702AbXHXMAP (ORCPT ); Fri, 24 Aug 2007 08:00:15 -0400 Received: from hu-out-0506.google.com ([72.14.214.232]:32083 "EHLO hu-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756797AbXHXMAM (ORCPT ); Fri, 24 Aug 2007 08:00:12 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=beta; h=received:from:to:subject:date:user-agent:cc:references:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:message-id; b=ClY8+lu2ywahmG2Q0JwJaxcNRNJ9otNhqSvl/vveXLgaQf6q8Y3wCcQgNrUSl19SDEjp5Zcquz7QF1jRUCT8sVcjRRGhB7vXjKeIAdlZAG2V6KdsW3LmATQ8LB/gNxjm3O1kDf2lUTagnVRl9JH3luwGHu+ZoHpOK0/Tb0rfzrQ= From: Denys Vlasenko To: Satyam Sharma Subject: Re: [PATCH] i386: Fix a couple busy loops in mach_wakecpu.h:wait_for_init_deassert() Date: Fri, 24 Aug 2007 12:59:32 +0100 User-Agent: KMail/1.9.1 Cc: Heiko Carstens , Herbert Xu , Chris Snook , clameter@sgi.com, Linux Kernel Mailing List , linux-arch@vger.kernel.org, Linus Torvalds , netdev@vger.kernel.org, Andrew Morton , ak@suse.de, davem@davemloft.net, schwidefsky@de.ibm.com, wensong@linux-vs.org, horms@verge.net.au, wjiang@resilience.com, cfriesen@nortel.com, zlynx@acm.org, rpjday@mindspring.com, jesper.juhl@gmail.com, segher@kernel.crashing.org References: <46C2350A.1010807@redhat.com> <20070815081841.GA16551@osiris.boeblingen.de.ibm.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200708241259.33659.vda.linux@googlemail.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 786 Lines: 23 On Thursday 16 August 2007 01:39, Satyam Sharma wrote: > > static inline void wait_for_init_deassert(atomic_t *deassert) > { > - while (!atomic_read(deassert)); > + while (!atomic_read(deassert)) > + cpu_relax(); > return; > } For less-than-briliant people like me, it's totally non-obvious that cpu_relax() is needed for correctness here, not just to make P4 happy. IOW: "atomic_read" name quite unambiguously means "I will read this variable from main memory". Which is not true and creates potential for confusion and bugs. -- vda - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/